WorldWideScience

Sample records for surface fluxes compared

  1. Monte Carlo surface flux tallies

    International Nuclear Information System (INIS)

    Favorite, Jeffrey A.

    2010-01-01

    Particle fluxes on surfaces are difficult to calculate with Monte Carlo codes because the score requires a division by the surface-crossing angle cosine, and grazing angles lead to inaccuracies. We revisit the standard practice of dividing by half of a cosine 'cutoff' for particles whose surface-crossing cosines are below the cutoff. The theory behind this approximation is sound, but the application of the theory to all possible situations does not account for two implicit assumptions: (1) the grazing band must be symmetric about 0, and (2) a single linear expansion for the angular flux must be applied in the entire grazing band. These assumptions are violated in common circumstances; for example, for separate in-going and out-going flux tallies on internal surfaces, and for out-going flux tallies on external surfaces. In some situations, dividing by two-thirds of the cosine cutoff is more appropriate. If users were able to control both the cosine cutoff and the substitute value, they could use these parameters to make accurate surface flux tallies. The procedure is demonstrated in a test problem in which Monte Carlo surface fluxes in cosine bins are converted to angular fluxes and compared with the results of a discrete ordinates calculation.

  2. Comparison of surface energy fluxes with satellite-derived surface energy flux estimates from a shrub-steppe

    International Nuclear Information System (INIS)

    Kirkham, R.R.

    1993-12-01

    This thesis relates the components of the surface energy balance (i.e., net radiation, sensible and latent heat flux densities, soil heat flow) to remotely sensed data for native vegetation in a semi-arid environment. Thematic mapper data from Landsat 4 and 5 were used to estimate net radiation, sensible heat flux (H), and vegetation amount. Several sources of ground truth were employed. They included soil water balance using the neutron thermalization method and weighing lysimeters, and the measurement of energy fluxes with the Bowen ratio energy balance (BREB) technique. Sensible and latent heat flux were measured at four sites on the U.S. Department of Energy's Hanford Site using a weighing lysimeter and/or BREB stations. The objective was to calibrate an aerodynamic transport equation that related H to radiant surface temperature. The transport equation was then used with Landsat thermal data to generate estimates of H and compare these estimates against H values obtained with BREB/lysimeters at the time of overflight. Landsat and surface meteorologic data were used to estimate the radiation budget terms at the surface. Landsat estimates of short-wave radiation reflected from the surface correlate well with reflected radiation measured using inverted Eppley pyranometers. Correlation of net radiation estimates determined from satellite data, pyranometer, air temperature, and vapor pressure compared to net radiometer values obtained at time of overflight were excellent for a single image, but decrease for multiple images. Soil heat flux, G T , is a major component of the energy balance in arid systems and G T generally decreases as vegetation cover increases. Normalized difference vegetation index (NDVI) values generated from Landsat thermatic mapper data were representative of field observations of the presence of green vegetation, but it was not possible to determine a single relationship between NDVI and G T for all sites

  3. Plasma–Surface Interactions Under High Heat and Particle Fluxes

    Directory of Open Access Journals (Sweden)

    Gregory De Temmerman

    2013-01-01

    Full Text Available The plasma-surface interactions expected in the divertor of a future fusion reactor are characterized by extreme heat and particle fluxes interacting with the plasma-facing surfaces. Powerful linear plasma generators are used to reproduce the expected plasma conditions and allow plasma-surface interactions studies under those very harsh conditions. While the ion energies on the divertor surfaces of a fusion device are comparable to those used in various plasma-assited deposition and etching techniques, the ion (and energy fluxes are up to four orders of magnitude higher. This large upscale in particle flux maintains the surface under highly non-equilibrium conditions and bring new effects to light, some of which will be described in this paper.

  4. Development of computational technique for labeling magnetic flux-surfaces

    International Nuclear Information System (INIS)

    Nunami, Masanori; Kanno, Ryutaro; Satake, Shinsuke; Hayashi, Takaya; Takamaru, Hisanori

    2006-03-01

    In recent Large Helical Device (LHD) experiments, radial profiles of ion temperature, electric field, etc. are measured in the m/n=1/1 magnetic island produced by island control coils, where m is the poloidal mode number and n the toroidal mode number. When the transport of the plasma in the radial profiles is numerically analyzed, an average over a magnetic flux-surface in the island is a very useful concept to understand the transport. On averaging, a proper labeling of the flux-surfaces is necessary. In general, it is not easy to label the flux-surfaces in the magnetic field with the island, compared with the case of a magnetic field configuration having nested flux-surfaces. In the present paper, we have developed a new computational technique to label the magnetic flux-surfaces. This technique is constructed by using an optimization algorithm, which is known as an optimization method called the simulated annealing method. The flux-surfaces are discerned by using two labels: one is classification of the magnetic field structure, i.e., core, island, ergodic, and outside regions, and the other is a value of the toroidal magnetic flux. We have applied the technique to an LHD configuration with the m/n=1/1 island, and successfully obtained the discrimination of the magnetic field structure. (author)

  5. Plasmas fluxes to surfaces for an oblique magnetic field

    International Nuclear Information System (INIS)

    Pitcher, C.S.; Stangeby, P.C.; Elder, J.D.; Bell, M.G.; Kilpatrick, S.J.; Manos, D.M.; Medley, S.S.; Owens, D.K.; Ramsey, A.T.; Ulrickson, M.

    1992-07-01

    The poloidal and toroidal spatial distributions of D α , He I and C II emission have been obtained in the vicinity of the TFTR bumper limiter and are compared with models of ion flow to the surface. The distributions are found not to agree with a model (the ''Cosine'' model) which determines the incident flux density using only the parallel fluxes in the scrape-off layer and the projected area of the surface perpendicular to the field lines. In particular, the Cosine model is not able to explain the significant fluxes observed at locations on the surface which are oblique to the magnetic field. It is further shown that these fluxes cannot be explained by the finite Larmor radius of impinging ions. Finally, it is demonstrated, with the use of Monte Carlo codes, that the distributions can be explained by including both parallel and cross-field transport onto the limiter surface

  6. Surface Flux Modeling for Air Quality Applications

    Directory of Open Access Journals (Sweden)

    Limei Ran

    2011-08-01

    Full Text Available For many gasses and aerosols, dry deposition is an important sink of atmospheric mass. Dry deposition fluxes are also important sources of pollutants to terrestrial and aquatic ecosystems. The surface fluxes of some gases, such as ammonia, mercury, and certain volatile organic compounds, can be upward into the air as well as downward to the surface and therefore should be modeled as bi-directional fluxes. Model parameterizations of dry deposition in air quality models have been represented by simple electrical resistance analogs for almost 30 years. Uncertainties in surface flux modeling in global to mesoscale models are being slowly reduced as more field measurements provide constraints on parameterizations. However, at the same time, more chemical species are being added to surface flux models as air quality models are expanded to include more complex chemistry and are being applied to a wider array of environmental issues. Since surface flux measurements of many of these chemicals are still lacking, resistances are usually parameterized using simple scaling by water or lipid solubility and reactivity. Advances in recent years have included bi-directional flux algorithms that require a shift from pre-computation of deposition velocities to fully integrated surface flux calculations within air quality models. Improved modeling of the stomatal component of chemical surface fluxes has resulted from improved evapotranspiration modeling in land surface models and closer integration between meteorology and air quality models. Satellite-derived land use characterization and vegetation products and indices are improving model representation of spatial and temporal variations in surface flux processes. This review describes the current state of chemical dry deposition modeling, recent progress in bi-directional flux modeling, synergistic model development research with field measurements, and coupling with meteorological land surface models.

  7. Estimating surface fluxes over the north Tibetan Plateau area with ASTER imagery

    Directory of Open Access Journals (Sweden)

    Weiqiang Ma

    2009-01-01

    Full Text Available Surface fluxes are important boundary conditions for climatological modeling and Asian monsoon system. The recent availability of high-resolution, multi-band imagery from the ASTER (Advanced Space-borne Thermal Emission and Reflection radiometer sensor has enabled us to estimate surface fluxes to bridge the gap between local scale flux measurements using micrometeorological instruments and regional scale land-atmosphere exchanges of water and heat fluxes that are fundamental for the understanding of the water cycle in the Asian monsoon system. A parameterization method based on ASTER data and field observations has been proposed and tested for deriving surface albedo, surface temperature, Normalized Difference Vegetation Index (NDVI, Modified Soil Adjusted Vegetation Index (MSAVI, vegetation coverage, Leaf Area Index (LAI, net radiation flux, soil heat flux, sensible heat flux and latent heat flux over heterogeneous land surface in this paper. As a case study, the methodology was applied to the experimental area of the Coordinated Enhanced Observing Period (CEOP Asia-Australia Monsoon Project (CAMP on the Tibetan Plateau (CAMP/Tibet, located at the north Tibetan Plateau. The ASTER data of 24 July 2001, 29 November 2001 and 12 March 2002 was used in this paper for the case of summer, winter and spring. To validate the proposed methodology, the ground-measured surface variables (surface albedo and surface temperature and land surface heat fluxes (net radiation flux, soil heat flux, sensible heat flux and latent heat flux were compared to the ASTER derived values. The results show that the derived surface variables and land surface heat fluxes in three different months over the study area are in good accordance with the land surface status. Also, the estimated land surface variables and land surface heat fluxes are in good accordance with ground measurements, and all their absolute percentage difference (APD is less than 10% in the validation sites

  8. Soil surface CO2 fluxes on the Konza Prairie

    Science.gov (United States)

    Norman, J. M.; Garcia, R.; Verma, Shoshi B.

    1990-01-01

    The utilization of a soil chamber to measure fluxes of soil-surface CO2 fluxes is described in terms of equipment, analytical methods, and estimate quality. A soil chamber attached to a gas-exchange system measures the fluxes every 5-15 min, and the data are compared to measurements of the CO2 fluxes from the canopy and from the soil + canopy. The soil chamber yields good measurements when operated in a closed system that is ported to the free atmosphere, and the CO2 flux is found to have a diurnal component.

  9. Soil surface CO2 fluxes and the carbon budget of a grassland

    Science.gov (United States)

    Norman, J. M.; Garcia, R.; Verma, S. B.

    1992-01-01

    Measurements of soil surface CO2 fluxes are reported for three sites within the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) area, and simple empirical equations are fit to the data to provide predictions of soil fluxes from environmental observations. A prototype soil chamber, used to make the flux measurements, is described and tested by comparing CO2 flux measurements to a 40-L chamber, a 1-m/cu chamber, and eddy correlation. Results suggest that flux measurements with the prototype chamber are consistent with measurements by other methods to within about 20 percent. A simple empirical equation based on 10-cm soil temperature, 0- to 10-cm soil volumetric water content, and leaf area index predicts the soil surface CO2 flux with a rms error of 1.2 micro-mol sq m/s for all three sites. Further evidence supports using this equation to evaluate soil surface CO2 during the 1987 FIFE experiment. The soil surface CO2 fluxes when averaged over 24 hours are comparable to daily gross canopy photosynthetic rates. For 6 days of data the net daily accumulation of carbon is about 0.6 g CO2 sq m/d; this is only a few percent of the daily gross accumulation of carbon by photosynthesis. As the soil became drier in 1989, the net accumulation of carbon by the prairie increased, suggesting that the soil flux is more sensitive to temperature and drought than the photosynthetic fluxes.

  10. Response of Moist Convection to Multi-scale Surface Flux Heterogeneity

    Science.gov (United States)

    Kang, S. L.; Ryu, J. H.

    2015-12-01

    We investigate response of moist convection to multi-scale feature of the spatial variation of surface sensible heat fluxes (SHF) in the afternoon evolution of the convective boundary layer (CBL), utilizing a mesoscale-domain large eddy simulation (LES) model. The multi-scale surface heterogeneity feature is analytically created as a function of the spectral slope in the wavelength range from a few tens of km to a few hundreds of m in the spectrum of surface SHF on a log-log scale. The response of moist convection to the κ-3 - slope (where κ is wavenumber) surface SHF field is compared with that to the κ-2 - slope surface, which has a relatively weak mesoscale feature, and the homogeneous κ0 - slope surface. Given the surface energy balance with a spatially uniform available energy, the prescribed SHF has a 180° phase lag with the latent heat flux (LHF) in a horizontal domain of (several tens of km)2. Thus, warmer (cooler) surface is relatively dry (moist). For all the cases, the same observation-based sounding is prescribed for the initial condition. For all the κ-3 - slope surface heterogeneity cases, early non-precipitating shallow clouds further develop into precipitating deep thunderstorms. But for all the κ-2 - slope cases, only shallow clouds develop. We compare the vertical profiles of domain-averaged fluxes and variances, and the contribution of the mesoscale and turbulence contributions to the fluxes and variances, between the κ-3 versus κ-2 slope cases. Also the cross-scale processes are investigated.

  11. Validating modeled turbulent heat fluxes across large freshwater surfaces

    Science.gov (United States)

    Lofgren, B. M.; Fujisaki-Manome, A.; Gronewold, A.; Anderson, E. J.; Fitzpatrick, L.; Blanken, P.; Spence, C.; Lenters, J. D.; Xiao, C.; Charusambot, U.

    2017-12-01

    Turbulent fluxes of latent and sensible heat are important physical processes that influence the energy and water budgets of the Great Lakes. Validation and improvement of bulk flux algorithms to simulate these turbulent heat fluxes are critical for accurate prediction of hydrodynamics, water levels, weather, and climate over the region. Here we consider five heat flux algorithms from several model systems; the Finite-Volume Community Ocean Model, the Weather Research and Forecasting model, and the Large Lake Thermodynamics Model, which are used in research and operational environments and concentrate on different aspects of the Great Lakes' physical system, but interface at the lake surface. The heat flux algorithms were isolated from each model and driven by meteorological data from over-lake stations in the Great Lakes Evaporation Network. The simulation results were compared with eddy covariance flux measurements at the same stations. All models show the capacity to the seasonal cycle of the turbulent heat fluxes. Overall, the Coupled Ocean Atmosphere Response Experiment algorithm in FVCOM has the best agreement with eddy covariance measurements. Simulations with the other four algorithms are overall improved by updating the parameterization of roughness length scales of temperature and humidity. Agreement between modelled and observed fluxes notably varied with geographical locations of the stations. For example, at the Long Point station in Lake Erie, observed fluxes are likely influenced by the upwind land surface while the simulations do not take account of the land surface influence, and therefore the agreement is worse in general.

  12. Methane oxidation and methane fluxes in the ocean surface layer and deep anoxic waters

    Science.gov (United States)

    Ward, B. B.; Kilpatrick, K. A.; Novelli, P. C.; Scranton, M. I.

    1987-01-01

    Measured biological oxidation rates of methane in near-surface waters of the Cariaco Basin are compared with the diffusional fluxes computed from concentration gradients of methane in the surface layer. Methane fluxes and oxidation rates were investigated in surface waters, at the oxic/anoxic interface, and in deep anoxic waters. It is shown that the surface-waters oxidation of methane is a mechanism which modulates the flux of methane from marine waters to the atmosphere.

  13. Advances in the Surface Renewal Flux Measurement Method

    Science.gov (United States)

    Shapland, T. M.; McElrone, A.; Paw U, K. T.; Snyder, R. L.

    2011-12-01

    The measurement of ecosystem-scale energy and mass fluxes between the planetary surface and the atmosphere is crucial for understanding geophysical processes. Surface renewal is a flux measurement technique based on analyzing the turbulent coherent structures that interact with the surface. It is a less expensive technique because it does not require fast-response velocity measurements, but only a fast-response scalar measurement. It is therefore also a useful tool for the study of the global cycling of trace gases. Currently, surface renewal requires calibration against another flux measurement technique, such as eddy covariance, to account for the linear bias of its measurements. We present two advances in the surface renewal theory and methodology that bring the technique closer to becoming a fully independent flux measurement method. The first advance develops the theory of turbulent coherent structure transport associated with the different scales of coherent structures. A novel method was developed for identifying the scalar change rate within structures at different scales. Our results suggest that for canopies less than one meter in height, the second smallest coherent structure scale dominates the energy and mass flux process. Using the method for resolving the scalar exchange rate of the second smallest coherent structure scale, calibration is unnecessary for surface renewal measurements over short canopies. This study forms the foundation for analysis over more complex surfaces. The second advance is a sensor frequency response correction for measuring the sensible heat flux via surface renewal. Inexpensive fine-wire thermocouples are frequently used to record high frequency temperature data in the surface renewal technique. The sensible heat flux is used in conjunction with net radiation and ground heat flux measurements to determine the latent heat flux as the energy balance residual. The robust thermocouples commonly used in field experiments

  14. The effects of sea surface temperature gradients on surface turbulent fluxes

    Science.gov (United States)

    Steffen, John

    A positive correlation between sea surface temperature (SST) and wind stress perturbation near strong SST gradients (DeltaSST) has been observed in different parts of the world ocean, such as the Gulf Stream in the North Atlantic and the Kuroshio Extension east of Japan. These changes in winds and SSTs can modify near-surface stability, surface stress, and latent and sensible heat fluxes. In general, these small scale processes are poorly modeled in Numerical Weather Prediction (NWP) and climate models. Failure to account for these air--sea interactions produces inaccurate values of turbulent fluxes, and therefore a misrepresentation of the energy, moisture, and momentum budgets. Our goal is to determine the change in these surface turbulent fluxes due to overlooking the correlated variability in winds, SSTs, and related variables. To model these air--sea interactions, a flux model was forced with and without SST--induced changes to the surface wind fields. The SST modification to the wind fields is based on a baroclinic argument as implemented by the University of Washington Planetary Boundary-Layer (UWPBL) model. Other input parameters include 2-m air temperature, 2-m dew point temperature, surface pressure (all from ERA--interim), and Reynolds Daily Optimum Interpolation Sea Surface Temperature (OISST). Flux model runs are performed every 6 hours starting in December 2002 and ending in November 2003. From these model outputs, seasonal, monthly, and daily means of the difference between DeltaSST and no DeltaSST effects on sensible heat flux (SHF), latent heat flux (LHF), and surface stress are calculated. Since the greatest impacts occur during the winter season, six additional December-January-February (DJF) seasons were analyzed for 1987--1990 and 1999--2002. The greatest differences in surface turbulent fluxes are concentrated near strong SST fronts associated with the Gulf Stream and Kuroshio Extension. On average, 2002---2003 DJF seasonal differences in SHF

  15. An intercomparison of surface energy flux measurement systems used during FIFE 1987

    International Nuclear Information System (INIS)

    Nie, D.; Kanemasu, E.T.; Fritschen, L.J.; Weaver, H.L.; Smith, E.A.; Verma, S.B.; Field, R.T.; Kustas, W.P.; Stewart, J.B.

    1992-01-01

    During FIFE 1987, surface energy fluxes were measured at 22 flux sites by nine groups of scientists using different measuring systems. A rover Bowen ratio station was taken to 20 of the flux stations to serve as a reference for estimating the instrument-related differences. The rover system was installed within a few meters from the host instrument of a site. Using linear regression analysis, net radiation, Bowen ratio, and latent heat fluxes were compared between the rover measurements and the host measurements. The average differences in net radiation, Bowen ratio, and latent heat flux from different types of instruments can be up to 10, 30, and 20 percent, respectively. The Didcot net radiometer gave higher net radiation while the Swissteco type showed lower values, as compared to the corrected radiation energy balance system (REBS) model. The four-way components method and the Thornthwaite type give similar values to the REBS. The surface energy radiation balance systems type Bowen ratio systems exhibit slightly lower Bowen ratios and thus higher latent heat fluxes, compared to the arid zone evapotranspiration systems. Eddy correlation systems showed slightly lower latent heat flux in comparison to the Bowen ratio systems. It is recommended that users of the flux data take these differences into account. 11 refs

  16. Modeling radon flux from the earth's surface

    International Nuclear Information System (INIS)

    Schery, S.D.; Wasiolek, M.A.

    1998-01-01

    We report development of a 222 Rn flux density model and its use to estimate the 222 Rn flux density over the earth's land surface. The resulting maps are generated on a grid spacing of 1 0 x 1 0 using as input global data for soil radium, soil moisture, and surface temperature. While only a first approximation, the maps suggest a significant regional variation (a factor of three is not uncommon) and a significant seasonal variation (a factor of two is not uncommon) in 222 Rn flux density over the earth's surface. The estimated average global flux density from ice-free land is 34 ± 9 mBq m -2 s -1 . (author)

  17. Area-averaged surface fluxes and their time-space variability over the FIFE experimental domain

    Science.gov (United States)

    Smith, E. A.; Hsu, A. Y.; Crosson, W. L.; Field, R. T.; Fritschen, L. J.; Gurney, R. J.; Kanemasu, E. T.; Kustas, W. P.; Nie, D.; Shuttleworth, W. J.

    1992-01-01

    The underlying mean and variance properties of surface net radiation, sensible-latent heat fluxes and soil heat flux are studied over the densely instrumented grassland region encompassing FIFE. Flux variability is discussed together with the problem of scaling up to area-averaged fluxes. Results are compared and contrasted for cloudy and clear situations and examined for the influence of surface-induced biophysical controls (burn and grazing treatments) and topographic controls (aspect ratios and slope factors).

  18. A One-Source Approach for Estimating Land Surface Heat Fluxes Using Remotely Sensed Land Surface Temperature

    Directory of Open Access Journals (Sweden)

    Yongmin Yang

    2017-01-01

    Full Text Available The partitioning of available energy between sensible heat and latent heat is important for precise water resources planning and management in the context of global climate change. Land surface temperature (LST is a key variable in energy balance process and remotely sensed LST is widely used for estimating surface heat fluxes at regional scale. However, the inequality between LST and aerodynamic surface temperature (Taero poses a great challenge for regional heat fluxes estimation in one-source energy balance models. To address this issue, we proposed a One-Source Model for Land (OSML to estimate regional surface heat fluxes without requirements for empirical extra resistance, roughness parameterization and wind velocity. The proposed OSML employs both conceptual VFC/LST trapezoid model and the electrical analog formula of sensible heat flux (H to analytically estimate the radiometric-convective resistance (rae via a quartic equation. To evaluate the performance of OSML, the model was applied to the Soil Moisture-Atmosphere Coupling Experiment (SMACEX in United States and the Multi-Scale Observation Experiment on Evapotranspiration (MUSOEXE in China, using remotely sensed retrievals as auxiliary data sets at regional scale. Validated against tower-based surface fluxes observations, the root mean square deviation (RMSD of H and latent heat flux (LE from OSML are 34.5 W/m2 and 46.5 W/m2 at SMACEX site and 50.1 W/m2 and 67.0 W/m2 at MUSOEXE site. The performance of OSML is very comparable to other published studies. In addition, the proposed OSML model demonstrates similar skills of predicting surface heat fluxes in comparison to SEBS (Surface Energy Balance System. Since OSML does not require specification of aerodynamic surface characteristics, roughness parameterization and meteorological conditions with high spatial variation such as wind speed, this proposed method shows high potential for routinely acquisition of latent heat flux estimation

  19. Turbulent transport across invariant canonical flux surfaces

    International Nuclear Information System (INIS)

    Hollenberg, J.B.; Callen, J.D.

    1994-07-01

    Net transport due to a combination of Coulomb collisions and turbulence effects in a plasma is investigated using a fluid moment description that allows for kinetic and nonlinear effects via closure relations. The model considered allows for ''ideal'' turbulent fluctuations that distort but preserve the topology of species-dependent canonical flux surfaces ψ number-sign,s triple-bond ∫ dF · B number-sign,s triple-bond ∇ x [A + (m s /q s )u s ] in which u s is the flow velocity of the fluid species. Equations for the net transport relative to these surfaces due to ''nonideal'' dissipative processes are found for the total number of particles and total entropy enclosed by a moving canonical flux surface. The corresponding particle transport flux is calculated using a toroidal axisymmetry approximation of the ideal surfaces. The resulting Lagrangian transport flux includes classical, neoclassical-like, and anomalous contributions and shows for the first time how these various contributions should be summed to obtain the total particle transport flux

  20. Is X-ray emissivity constant on magnetic flux surfaces?

    International Nuclear Information System (INIS)

    Granetz, R.S.; Borras, M.C.

    1997-01-01

    Knowledge of the elongations and shifts of internal magnetic flux surfaces can be used to determine the q profile in elongated tokamak plasmas. X-ray tomography is thought to be a reasonable technique for independently measuring internal flux surface shapes, because it is widely believed that X-ray emissivity should be constant on a magnetic flux surface. In the Alcator C-Mod tokamak, the X-ray tomography diagnostic system consists of four arrays of 38 chords each. A comparison of reconstructed X-ray contours with magnetic flux surfaces shows a small but consistent discrepancy in the radial profile of elongation. Numerous computational tests have been performed to verify these findings, including tests of the sensitivity to calibration and viewing geometry errors, the accuracy of the tomography reconstruction algorithms, and other subtler effects. We conclude that the discrepancy between the X-ray contours and the magnetic flux surfaces is real, leading to the conclusion that X-ray emissivity is not exactly constant on a flux surface. (orig.)

  1. Quantifying the Terrestrial Surface Energy Fluxes Using Remotely-Sensed Satellite Data

    Science.gov (United States)

    Siemann, Amanda Lynn

    The dynamics of the energy fluxes between the land surface and the atmosphere drive local and regional climate and are paramount to understand the past, present, and future changes in climate. Although global reanalysis datasets, land surface models (LSMs), and climate models estimate these fluxes by simulating the physical processes involved, they merely simulate our current understanding of these processes. Global estimates of the terrestrial, surface energy fluxes based on observations allow us to capture the dynamics of the full climate system. Remotely-sensed satellite data is the source of observations of the land surface which provide the widest spatial coverage. Although net radiation and latent heat flux global, terrestrial, surface estimates based on remotely-sensed satellite data have progressed, comparable sensible heat data products and ground heat flux products have not progressed at this scale. Our primary objective is quantifying and understanding the terrestrial energy fluxes at the Earth's surface using remotely-sensed satellite data with consistent development among all energy budget components [through the land surface temperature (LST) and input meteorology], including validation of these products against in-situ data, uncertainty assessments, and long-term trend analysis. The turbulent fluxes are constrained by the available energy using the Bowen ratio of the un-constrained products to ensure energy budget closure. All final products are within uncertainty ranges of literature values, globally. When validated against the in-situ estimates, the sensible heat flux estimates using the CFSR air temperature and constrained with the products using the MODIS albedo produce estimates closest to the FLUXNET in-situ observations. Poor performance over South America is consistent with the largest uncertainties in the energy budget. From 1984-2007, the longwave upward flux increase due to the LST increase drives the net radiation decrease, and the

  2. Incoming Shortwave Fluxes at the Surface--A Comparison of GCM Results with Observations.

    Science.gov (United States)

    Garratt, J. R.

    1994-01-01

    Evidence is presented that the exam surface net radiation calculated in general circulation models at continental surfaces is mostly due to excess incoming shortwave fluxes. Based on long-term observations from 22 worldwide inland stations and results from four general circulation models the overestimate in models of 20% (11 W m2) in net radiation on an annual basis compares with 6% (9 W m2) for shortwave fluxes for the same 22 locations, or 9% (18 W m2) for a larger set of 93 stations (71 having shortwave fluxes only). For annual fluxes, these differences appear to be significant.

  3. Comparing the CarbonTracker and TM5-4DVar data assimilation systems for CO2 surface flux inversions

    NARCIS (Netherlands)

    Babenhauserheide, A.; Basu, S.; Peters, W.

    2015-01-01

    Data assimilation systems allow for estimating surface fluxes of greenhouse gases from atmospheric concentration measurements. Good knowledge about fluxes is essential to understand how climate change affects ecosystems and to characterize feedback mechanisms. Based on assimilation of more than one

  4. Comparing the CarbonTracker and TM5-4DVar data assimilation systems for CO2 surface flux inversions

    NARCIS (Netherlands)

    Babenhauserheide, A.; Basu, S.; Houweling, S.; Peters, W.; Butz, A.

    2015-01-01

    Data assimilation systems allow for estimating surface fluxes of greenhouse gases from atmospheric concentration measurements. Good knowledge about fluxes is essential to understand how climate change affects ecosystems and to characterize feedback mechanisms. Based on the assimilation of more than

  5. Surface renewal analysis for estimating turbulent surface fluxes

    International Nuclear Information System (INIS)

    Castellvi, F.

    2009-01-01

    A decade ago, the need for a long-term surface monitoring was recognized to better understand the soil-vegetation-atmosphere scalar exchange and interaction processes. the AmeriFlux concept emerged in the IGBP workshop (La Thuile, IT, 1995). Continuous acquisition of surface fluxes for different species such as temperature, water vapour, CO x , halocarbon, ozone, etc.,) and momentum allows determination of the influence of local (canopy) exchanges, fossil fuel emission, large-scale biotic exchange on ambient concentrations which are crucial to take decisions for protecting natural environments and water resources, to develop new perspective for modern agriculture and forest management and to better understand the global climate change. (Author)

  6. CYGNSS Surface Wind Observations and Surface Flux Estimates within Low-Latitude Extratropical Cyclones

    Science.gov (United States)

    Crespo, J.; Posselt, D. J.

    2017-12-01

    The Cyclone Global Navigation Satellite System (CYGNSS), launched in December 2016, aims to improve estimates of surface wind speeds over the tropical oceans. While CYGNSS's core mission is to provide better estimates of surface winds within the core of tropical cyclones, previous research has shown that the constellation, with its orbital inclination of 35°, also has the ability to observe numerous extratropical cyclones that form in the lower latitudes. Along with its high spatial and temporal resolution, CYGNSS can provide new insights into how extratropical cyclones develop and evolve, especially in the presence of thick clouds and precipitation. We will demonstrate this by presenting case studies of multiple extratropical cyclones observed by CYGNSS early on in its mission in both Northern and Southern Hemispheres. By using the improved estimates of surface wind speeds from CYGNSS, we can obtain better estimates of surface latent and sensible heat fluxes within and around extratropical cyclones. Surface heat fluxes, driven by surface winds and strong vertical gradients of water vapor and temperature, play a key role in marine cyclogenesis as they increase instability within the boundary layer and may contribute to extreme marine cyclogenesis. In the past, it has been difficult to estimate surface heat fluxes from space borne instruments, as these fluxes cannot be observed directly from space, and deficiencies in spatial coverage and attenuation from clouds and precipitation lead to inaccurate estimates of surface flux components, such as surface wind speeds. While CYGNSS only contributes estimates of surface wind speeds, we can combine this data with other reanalysis and satellite data to provide improved estimates of surface sensible and latent heat fluxes within and around extratropical cyclones and throughout the entire CYGNSS mission.

  7. Towards scale-independent land-surface flux estimates in Noah-MP

    Science.gov (United States)

    Thober, Stephan; Mizukami, Naoki; Samaniego, Luis; Attinger, Sabine; Clark, Martyn; Cuntz, Matthias

    2017-04-01

    Land-surface models use a variety of process representations to calculate terrestrial energy, water and biogeochemical fluxes. These process descriptions are usually derived from point measurements which are, in turn, scaled to much larger resolutions ranging from 1 km in catchment hydrology to 100 km in climate modelling. Both, hydrologic and climate models are nowadays run on different spatial resolutions, using the exactly same land surface representations. A fundamental criterion for the physical consistency of land-surface simulations across scales is that a flux estimated over a given area is independent of the spatial model resolution (i.e., the flux-matching criterion). The Noah-MP land surface model considers only one soil and land cover type per model grid cell without any representation of their subgrid variability, implying a weak flux-matching. A fractional approach simulates the subgrid variability but it requires a higher computational demand than using effective parameters and it is used only for land cover in current land surface schemes. A promising approach to derive scale-independent parameters is the Multiscale Parameter Regionalization (MPR) technique, which consists of two steps: first, it applies transfer functions directly to high-resolution data (such as 100 m soil maps) to derive high-resolution model parameter fields, acknowledging the full subgrid variability. Second, it upscales these high-resolution parameter fields to the model resolution by using appropriate upscaling operators. MPR has shown to improve substantially the scalability of the mesoscale Hydrologic Models mHM (Samaniego et al., 2010 WRR). Here, we apply the MPR technique to the Noah-MP land-surface model for a large sample of basins distributed across the contiguous USA. Specifically, we evaluate the flux-matching criterion for several hydrologic fluxes such as evapotranspiration and drainage at scales ranging from 3 km to 48 km. We investigate the impact of different

  8. An intercomparison and validation of satellite-based surface radiative energy flux estimates over the Arctic

    Science.gov (United States)

    Riihelä, Aku; Key, Jeffrey R.; Meirink, Jan Fokke; Kuipers Munneke, Peter; Palo, Timo; Karlsson, Karl-Göran

    2017-05-01

    Accurate determination of radiative energy fluxes over the Arctic is of crucial importance for understanding atmosphere-surface interactions, melt and refreezing cycles of the snow and ice cover, and the role of the Arctic in the global energy budget. Satellite-based estimates can provide comprehensive spatiotemporal coverage, but the accuracy and comparability of the existing data sets must be ascertained to facilitate their use. Here we compare radiative flux estimates from Clouds and the Earth's Radiant Energy System (CERES) Synoptic 1-degree (SYN1deg)/Energy Balanced and Filled, Global Energy and Water Cycle Experiment (GEWEX) surface energy budget, and our own experimental FluxNet / Satellite Application Facility on Climate Monitoring cLoud, Albedo and RAdiation (CLARA) data against in situ observations over Arctic sea ice and the Greenland Ice Sheet during summer of 2007. In general, CERES SYN1deg flux estimates agree best with in situ measurements, although with two particular limitations: (1) over sea ice the upwelling shortwave flux in CERES SYN1deg appears to be underestimated because of an underestimated surface albedo and (2) the CERES SYN1deg upwelling longwave flux over sea ice saturates during midsummer. The Advanced Very High Resolution Radiometer-based GEWEX and FluxNet-CLARA flux estimates generally show a larger range in retrieval errors relative to CERES, with contrasting tendencies relative to each other. The largest source of retrieval error in the FluxNet-CLARA downwelling shortwave flux is shown to be an overestimated cloud optical thickness. The results illustrate that satellite-based flux estimates over the Arctic are not yet homogeneous and that further efforts are necessary to investigate the differences in the surface and cloud properties which lead to disagreements in flux retrievals.

  9. Estimating surface fluxes using eddy covariance and numerical ogive optimization

    DEFF Research Database (Denmark)

    Sievers, J.; Papakyriakou, T.; Larsen, Søren Ejling

    2015-01-01

    Estimating representative surface fluxes using eddy covariance leads invariably to questions concerning inclusion or exclusion of low-frequency flux contributions. For studies where fluxes are linked to local physical parameters and up-scaled through numerical modelling efforts, low-frequency con......Estimating representative surface fluxes using eddy covariance leads invariably to questions concerning inclusion or exclusion of low-frequency flux contributions. For studies where fluxes are linked to local physical parameters and up-scaled through numerical modelling efforts, low...

  10. Evaluation of surface layer flux parameterizations using in-situ observations

    Science.gov (United States)

    Katz, Jeremy; Zhu, Ping

    2017-09-01

    Appropriate calculation of surface turbulent fluxes between the atmosphere and the underlying ocean/land surface is one of the major challenges in geosciences. In practice, the surface turbulent fluxes are estimated from the mean surface meteorological variables based on the bulk transfer model combined with the Monnin-Obukhov Similarity (MOS) theory. Few studies have been done to examine the extent to which such a flux parameterization can be applied to different weather and surface conditions. A novel validation method is developed in this study to evaluate the surface flux parameterization using in-situ observations collected at a station off the coast of Gulf of Mexico. The main findings are: (a) the theoretical prediction that uses MOS theory does not match well with those directly computed from the observations. (b) The largest spread in exchange coefficients is shown in strong stable conditions with calm winds. (c) Large turbulent eddies, which depend strongly on the mean flow pattern and surface conditions, tend to break the constant flux assumption in the surface layer.

  11. Neoclassical transport coefficients for tokamaks with bean-shaped flux surfaces

    International Nuclear Information System (INIS)

    Chang, C.S.; Kaye, S.M.

    1990-11-01

    Simple analytic representations of the neoclassical transport coefficients for indented flux surfaces are presented. It is shown that a transport coefficient for an indented flux surface can be expressed in terms of a linear combination of the previously known transport coefficients for two nonindented flux surfaces. Numerical calculations based on actual equilibria from the PBX-M tokamak indicate that, even for modestly indented flux surfaces, the ion neoclassical thermal transport can be over a factor of two smaller than in a circular plasma with the same midplane radius or with the equivalent areas. 6 refs., 5 figs., 1 tab

  12. Modeling surface energy fluxes from a patchwork of fields with different soils and crops

    Science.gov (United States)

    Klein, Christian; Thieme, Christoph; Heinlein, Florian; Priesack, Eckart

    2017-04-01

    Agroecosystems are a dominant terrestrial land-use on planet earth and cover about 36% of the ice-free surface (12% pasture, 26% agriculture) [Foley2011]. Within this land use type, management practices vary strongly due to climate, cultural preferences, degree of industrialization, soil properties, crop rotations, field sizes, degree of land use sustainability, water availability, sowing and harvest dates, tillage, etc. These management practices influence abiotic environmental factors like water flow and heat transport within the ecosystem leading to changes of land surface fluxes. The relevance of vegetation (e.g. crops), ground cover, and soil properties to the moisture and energy exchanges between the land surface and the atmosphere is well known [McPherson 2007], but the impact of vegetation growth dynamics on energy fluxes is only partly understood [Gayler et al. 2014]. Thus, the structure of turbulence and the albedo evolve during the cropping period and large variations of heat can be measured on the field scale [Aubinet2012]. One issue of local distributed mixture of different land use is the measurement process which makes it challenging to evaluate simulations. Unfortunately, for meteorological flux-measurements like the Flux-Gradient or the Eddy Covariance (EC) method, comparability with simulations only exists in the ideal case, where fields have to be completely uniform in land use and flat within the reach of the footprint. Then a model with one specific land use would have the same underlying source area as the measurement. An elegant method to avoid the shortcoming of grid cell resolution is the so called mixed approach, which was recently implemented into the ecosystem model framework Expert-N [Biernath et al. 2013]. The aim of this study was to analyze the impact of the characteristics of five managed field plots, planted with winter wheat, potato and maize on the near surface soil moistures and on the near surface energy flux exchanges of the

  13. Surface temperature and surface heat flux determination of the inverse heat conduction problem for a slab

    International Nuclear Information System (INIS)

    Kuroyanagi, Toshiyuki

    1983-07-01

    Based on an idea that surface conditions should be a reflection of interior temperature and interior heat flux variation as inverse as interior conditions has been determined completely by the surface temperature and/on surface heat flux as boundary conditions, a method is presented for determining the surface temperature and the surface heat flux of a solid when the temperature and heat flux at an interior point are a prescribed function of time. The method is developed by the integration of Duhumels' integral which has unknown temperature or unknown heat flux in its integrand. Specific forms of surface condition determination are developed for a sample inverse problem: slab. Ducussing the effect of a degree of avairable informations at an interior point due to damped system and the effect of variation of surface conditions on those formulations, it is shown that those formulations are capable of representing the unknown surface conditions except for small time interval followed by discontinuous change of surface conditions. The small un-resolved time interval is demonstrated by a numerical example. An evaluation method of heat flux at an interior point, which is requested by those formulations, is discussed. (author)

  14. Satellite-based Calibration of Heat Flux at the Ocean Surface

    Science.gov (United States)

    Barron, C. N.; Dastugue, J. M.; May, J. C.; Rowley, C. D.; Smith, S. R.; Spence, P. L.; Gremes-Cordero, S.

    2016-02-01

    Model forecasts of upper ocean heat content and variability on diurnal to daily scales are highly dependent on estimates of heat flux through the air-sea interface. Satellite remote sensing is applied to not only inform the initial ocean state but also to mitigate errors in surface heat flux and model representations affecting the distribution of heat in the upper ocean. Traditional assimilation of sea surface temperature (SST) observations re-centers ocean models at the start of each forecast cycle. Subsequent evolution depends on estimates of surface heat fluxes and upper-ocean processes over the forecast period. The COFFEE project (Calibration of Ocean Forcing with satellite Flux Estimates) endeavors to correct ocean forecast bias through a responsive error partition among surface heat flux and ocean dynamics sources. A suite of experiments in the southern California Current demonstrates a range of COFFEE capabilities, showing the impact on forecast error relative to a baseline three-dimensional variational (3DVAR) assimilation using Navy operational global or regional atmospheric forcing. COFFEE addresses satellite-calibration of surface fluxes to estimate surface error covariances and links these to the ocean interior. Experiment cases combine different levels of flux calibration with different assimilation alternatives. The cases may use the original fluxes, apply full satellite corrections during the forecast period, or extend hindcast corrections into the forecast period. Assimilation is either baseline 3DVAR or standard strong-constraint 4DVAR, with work proceeding to add a 4DVAR expanded to include a weak constraint treatment of the surface flux errors. Covariance of flux errors is estimated from the recent time series of forecast and calibrated flux terms. While the California Current examples are shown, the approach is equally applicable to other regions. These approaches within a 3DVAR application are anticipated to be useful for global and larger

  15. APPLICATION OF A SURFACE-RENEWAL MODEL TO PERMEATE-FLUX DATA FOR CONSTANTPRESSURE CROSS-FLOW MICROFILTRATION WITH DEAN VORTICES

    Directory of Open Access Journals (Sweden)

    G. Idan

    2015-06-01

    Full Text Available AbstractThe introduction of flow instabilities into a microfiltration process can dramatically change several elements such as the surface-renewal rate, permeate flux, specific cake resistance, and cake buildup on the membrane in a positive way. A recently developed surface-renewal model for constant-pressure, cross-flow microfiltration (Hasan et al., 2013 is applied to the permeate-flux data reported by Mallubhotla and Belfort (1997, one set of which included flow instabilities (Dean vortices while the other set did not. The surface-renewal model has two forms - the complete model and an approximate model. For the complete model, the introduction of vortices leads to a 53% increase in the surface-renewal rate, which increases the limiting (i.e., steady-state permeate flux by 30%, decreases the specific cake resistance by 14.5% and decreases the limiting cake mass by 15.5% compared to operation without vortices. For the approximate model, a 50% increase in the value of surface renewal rate is shown due to vortices, which increases the limiting permeate flux by 30%, decreases the specific cake resistance by 10.5% and decreases the limiting cake mass by 13.7%. The cake-filtration version of the critical-flux model of microfiltration (Field et al., 1995 is also compared against the experimental permeate-flux data of Mallubhotla and Belfort (1997. Although this model can represent the data, the quality of its fit is inferior compared to that of the surface-renewal model.

  16. Theory of redeposition of sputtered flux on to surface asperities

    International Nuclear Information System (INIS)

    Belson, J.; Wilson, I.H.

    1981-01-01

    This paper models the topographical evolution of features on amorphous surfaces under ion bombardment. Specifically, evolution due to accretion of material sputtered from areas adjacent to a feature has been investigated in terms of the flux density redeposited on to an arbitrary profile y = f(xi) from a linear emitter. Analytical solutions have been found for the early ( first burst ) evolution of linear and sinusoidal surface features in cases where the emitter radiates isotropically or anisotropically (cosine law) from each point of its length. The predictions of models based on these two types of emitter are compared. Both types produce enhanced deposition near the foot of a linear slope but the effect is much greater for isotropic emission. Above the foot of a linear slope there is a point beyond which the redeposition due to an anisotropic emitter is greater than that due to an isotropic emitter of identical luminance. For a 90 0 slope (step or groove of rectangular section) the point is about 0.4 times the emitter length (i.e. 0.4 x groove width) above the base. Sinusoidal asperities which are present in a high surface density are expected to receive significant redeposited flux only near their bases. By contrast, widely separated asperities would receive flux over almost all or their profiles. In this latter situation the magnitude of the redeposited flux density is found to be relatively insensitive to position on a profile. (orig.)

  17. Prediction of Experimental Surface Heat Flux of Thin Film Gauges using ANFIS

    Science.gov (United States)

    Sarma, Shrutidhara; Sahoo, Niranjan; Unal, Aynur

    2018-05-01

    Precise quantification of surface heat fluxes in highly transient environment is of paramount importance from the design point of view of several engineering equipment like thermal protection or cooling systems. Such environments are simulated in experimental facilities by exposing the surface with transient heat loads typically step/impulsive in nature. The surface heating rates are then determined from highly transient temperature history captured by efficient surface temperature sensors. The classical approach is to use thin film gauges (TFGs) in which temperature variations are acquired within milliseconds, thereby allowing calculation of surface heat flux, based on the theory of one-dimensional heat conduction on a semi-infinite body. With recent developments in the soft computing methods, the present study is an attempt for the application of intelligent system technique, called adaptive neuro fuzzy inference system (ANFIS) to recover surface heat fluxes from a given temperature history recorded by TFGs without having the need to solve lengthy analytical equations. Experiments have been carried out by applying known quantity of `impulse heat load' through laser beam on TFGs. The corresponding voltage signals have been acquired and surface heat fluxes are estimated through classical analytical approach. These signals are then used to `train' the ANFIS model, which later predicts output for `test' values. Results from both methods have been compared and these surface heat fluxes are used to predict the non-linear relationship between thermal and electrical properties of the gauges that are exceedingly pertinent to the design of efficient TFGs. Further, surface plots have been created to give an insight about dimensionality effect of the non-linear dependence of thermal/electrical parameters on each other. Later, it is observed that a properly optimized ANFIS model can predict the impulsive heat profiles with significant accuracy. This paper thus shows the

  18. Climate-induced hotspots in surface energy fluxes from 1948 to 2000

    International Nuclear Information System (INIS)

    Sheng Li; Liu Shuhua; Liu Heping

    2010-01-01

    Understanding how land surfaces respond to climate change requires knowledge of land-surface processes, which control the degree to which interannual variability and mean trends in climatic variables affect the surface energy budget. We use the latest version of the Community Land Model version 3.5 (CLM3.5), which is driven by the latest updated hybrid reanalysis-observation atmospheric forcing dataset constructed by Princeton University, to obtain global distributions of the surface energy budget from 1948 to 2000. We identify climate change hotspots and surface energy flux hotspots from 1948 to 2000. Surface energy flux hotspots, which reflect regions with strong changes in surface energy fluxes, reveal seasonal variations with strong signals in winter, spring, and autumn and weak ones in summer. Locations for surface energy flux hotspots are not, however, fully linked with those for climate change hotspots, suggesting that only in some regions are land surfaces more responsive to climate change in terms of interannual variability and mean trends.

  19. Intercomparison of oceanic and atmospheric forced and coupled mesoscale simulations. Part I: Surface fluxes

    Science.gov (United States)

    Josse, P.; Caniaux, G.; Giordani, H.; Planton, S.

    1999-04-01

    A mesoscale non-hydrostatic atmospheric model has been coupled with a mesoscale oceanic model. The case study is a four-day simulation of a strong storm event observed during the SEMAPHORE experiment over a 500 × 500 km2 domain. This domain encompasses a thermohaline front associated with the Azores current. In order to analyze the effect of mesoscale coupling, three simulations are compared: the first one with the atmospheric model forced by realistic sea surface temperature analyses; the second one with the ocean model forced by atmospheric fields, derived from weather forecast re-analyses; the third one with the models being coupled. For these three simulations the surface fluxes were computed with the same bulk parametrization. All three simulations succeed well in representing the main oceanic or atmospheric features observed during the storm. Comparison of surface fields with in situ observations reveals that the winds of the fine mesh atmospheric model are more realistic than those of the weather forecast re-analyses. The low-level winds simulated with the atmospheric model in the forced and coupled simulations are appreciably stronger than the re-analyzed winds. They also generate stronger fluxes. The coupled simulation has the strongest surface heat fluxes: the difference in the net heat budget with the oceanic forced simulation reaches on average 50 Wm-2 over the simulation period. Sea surface-temperature cooling is too weak in both simulations, but is improved in the coupled run and matches better the cooling observed with drifters. The spatial distributions of sea surface-temperature cooling and surface fluxes are strongly inhomogeneous over the simulation domain. The amplitude of the flux variation is maximum in the coupled run. Moreover the weak correlation between the cooling and heat flux patterns indicates that the surface fluxes are not responsible for the whole cooling and suggests that the response of the ocean mixed layer to the atmosphere is

  20. A comparison of optical and microwave scintillometers with eddy covariance derived surface heat fluxes

    KAUST Repository

    Yee, Mei Sun

    2015-11-01

    Accurate measurements of energy fluxes between land and atmosphere are important for understanding and modeling climatic patterns. Several methods are available to measure heat fluxes, and scintillometers are becoming increasingly popular because of their ability to measure sensible (. H) and latent (. LvE) heat fluxes over large spatial scales. The main motivation of this study was to test the use of different methods and technologies to derive surface heat fluxes.Measurements of H and LvE were carried out with an eddy covariance (EC) system, two different makes of optical large aperture scintillometers (LAS) and two microwave scintillometers (MWS) with different frequencies at a pasture site in a semi-arid environment of New South Wales, Australia. We used the EC measurements as a benchmark. Fluxes derived from the EC system and LAS systems agreed (R2>0.94), whereas the MWS systems measured lower H (bias ~60Wm-2) and larger LvE (bias ~65Wm-2) than EC. When the scintillometers were compared against each other, the two LASs showed good agreement of H (R2=0.98), while MWS with different frequencies and polarizations led to different results. Combination of LAS and MWS measurements (i.e., two wavelength method) resulted in performance that fell in between those estimated using either LAS or MWS alone when compared with the EC system. The cause for discrepancies between surface heat fluxes derived from the EC system and those from the MWS systems and the two-wavelength method are possibly related to inaccurate assignment of the structure parameter of temperature and humidity. Additionally, measurements from MWSs can be associated with two values of the Bowen ratio, thereby leading to uncertainties in the estimation of the fluxes. While only one solution has been considered in this study, when LvE was approximately less than 200Wm-2, the alternate solution may be more accurate. Therefore, for measurements of surface heat fluxes in a semi-arid or dry environment, the

  1. Estimating regional methane surface fluxes: the relative importance of surface and GOSAT mole fraction measurements

    Directory of Open Access Journals (Sweden)

    A. Fraser

    2013-06-01

    Full Text Available We use an ensemble Kalman filter (EnKF, together with the GEOS-Chem chemistry transport model, to estimate regional monthly methane (CH4 fluxes for the period June 2009–December 2010 using proxy dry-air column-averaged mole fractions of methane (XCH4 from GOSAT (Greenhouse gases Observing SATellite and/or NOAA ESRL (Earth System Research Laboratory and CSIRO GASLAB (Global Atmospheric Sampling Laboratory CH4 surface mole fraction measurements. Global posterior estimates using GOSAT and/or surface measurements are between 510–516 Tg yr−1, which is less than, though within the uncertainty of, the prior global flux of 529 ± 25 Tg yr−1. We find larger differences between regional prior and posterior fluxes, with the largest changes in monthly emissions (75 Tg yr−1 occurring in Temperate Eurasia. In non-boreal regions the error reductions for inversions using the GOSAT data are at least three times larger (up to 45% than if only surface data are assimilated, a reflection of the greater spatial coverage of GOSAT, with the two exceptions of latitudes >60° associated with a data filter and over Europe where the surface network adequately describes fluxes on our model spatial and temporal grid. We use CarbonTracker and GEOS-Chem XCO2 model output to investigate model error on quantifying proxy GOSAT XCH4 (involving model XCO2 and inferring methane flux estimates from surface mole fraction data and show similar resulting fluxes, with differences reflecting initial differences in the proxy value. Using a series of observing system simulation experiments (OSSEs we characterize the posterior flux error introduced by non-uniform atmospheric sampling by GOSAT. We show that clear-sky measurements can theoretically reproduce fluxes within 10% of true values, with the exception of tropical regions where, due to a large seasonal cycle in the number of measurements because of clouds and aerosols, fluxes are within 15% of true fluxes. We evaluate our

  2. Surface radiation fluxes in transient climate simulations

    Science.gov (United States)

    Garratt, J. R.; O'Brien, D. M.; Dix, M. R.; Murphy, J. M.; Stephens, G. L.; Wild, M.

    1999-01-01

    Transient CO 2 experiments from five coupled climate models, in which the CO 2 concentration increases at rates of 0.6-1.1% per annum for periods of 75-200 years, are used to document the responses of surface radiation fluxes, and associated atmospheric properties, to the CO 2 increase. In all five models, the responses of global surface temperature and column water vapour are non-linear and fairly tightly constrained. Thus, global warming lies between 1.9 and 2.7 K at doubled, and between 3.1 and 4.1 K at tripled, CO 2, whilst column water vapour increases by between 3.5 and 4.5 mm at doubled, and between 7 and 8 mm at tripled, CO 2. Global cloud fraction tends to decrease by 1-2% out to tripled CO 2, mainly the result of decreases in low cloud. Global increases in column water, and differences in these increases between models, are mainly determined by the warming of the tropical oceans relative to the middle and high latitudes; these links are emphasised in the zonal profiles of warming and column water vapour increase, with strong water vapour maxima in the tropics. In all models the all-sky shortwave flux to the surface S↓ (global, annual average) changes by less than 5 W m -2 out to tripled CO 2, in some cases being essentially invariant in time. In contrast, the longwave flux to the surface L↓ increases significantly, by 25 W m -2 typically at tripled CO 2. The variations of S↓ and L↓ (clear-sky and all-sky fluxes) with increase in CO 2 concentration are generally non-linear, reflecting the effects of ocean thermal inertia, but as functions of global warming are close to linear in all five models. This is best illustrated for the clear-sky downwelling fluxes, and the net radiation. Regionally, as illustrated in zonal profiles and global distributions, greatest changes in both S↓ and L↓ are the result primarily of local maxima in warming and column water vapour increases.

  3. Mapping Surface Heat Fluxes by Assimilating SMAP Soil Moisture and GOES Land Surface Temperature Data

    Science.gov (United States)

    Lu, Yang; Steele-Dunne, Susan C.; Farhadi, Leila; van de Giesen, Nick

    2017-12-01

    Surface heat fluxes play a crucial role in the surface energy and water balance. In situ measurements are costly and difficult, and large-scale flux mapping is hindered by surface heterogeneity. Previous studies have demonstrated that surface heat fluxes can be estimated by assimilating land surface temperature (LST) and soil moisture to determine two key parameters: a neutral bulk heat transfer coefficient (CHN) and an evaporative fraction (EF). Here a methodology is proposed to estimate surface heat fluxes by assimilating Soil Moisture Active Passive (SMAP) soil moisture data and Geostationary Operational Environmental Satellite (GOES) LST data into a dual-source (DS) model using a hybrid particle assimilation strategy. SMAP soil moisture data are assimilated using a particle filter (PF), and GOES LST data are assimilated using an adaptive particle batch smoother (APBS) to account for the large gap in the spatial and temporal resolution. The methodology is implemented in an area in the U.S. Southern Great Plains. Assessment against in situ observations suggests that soil moisture and LST estimates are in better agreement with observations after assimilation. The RMSD for 30 min (daytime) flux estimates is reduced by 6.3% (8.7%) and 31.6% (37%) for H and LE on average. Comparison against a LST-only and a soil moisture-only assimilation case suggests that despite the coarse resolution, assimilating SMAP soil moisture data is not only beneficial but also crucial for successful and robust flux estimation, particularly when the uncertainties in the model estimates are large.

  4. Spatial distribution of potential near surface moisture flux at Yucca Mountain

    International Nuclear Information System (INIS)

    Flint, A.L.; Flint, L.E.

    1994-01-01

    An estimate of the areal distribution of present-day surface liquid moisture flux at Yucca Mountain was made using field measured water contents and laboratory measured rock properties. Using available data for physical and hydrologic properties (porosity, saturated hydraulic conductivity, moisture retention functions) of the volcanic rocks, surface lithologic units that are hydrologically similar were delineated. Moisture retention and relative permeability functions were assigned to each surface unit based on the similarity of the mean porosity and saturated hydraulic conductivity of the surface unit to laboratory samples of the same lithology. The potential flux into the mountain was estimated for each surface hydrologic unit using the mean saturated hydraulic conductivity for each unit and assuming all matrix flow. Using measured moisture profiles for each of the surface units, estimates were made of the depth at which seasonal fluctuations diminish and steady state downward flux conditions are likely to exist. The hydrologic properties at that depth were used with the current relative saturation of the tuff, to estimate flux as the unsaturated hydraulic conductivity. This method assumes a unit gradient. The range in estimated flux was 0.02 mm/yr for the welded Tiva Canyon to 13.4 mm/yr for the nonwelded Paintbrush Tuff. The areally averaged flux was 1.4 mm/yr. The major zones of high flux occur to the north of the potential repository boundary where the nonwelded tuffs are exposed in the major drainages

  5. Spatial distribution of potential near surface moisture flux at Yucca Mountain

    International Nuclear Information System (INIS)

    Flint, A.L.; Flint, L.E.

    1994-01-01

    An estimate of the areal distribution of present-day surface liquid moisture flux at Yucca Mountain was made using field measured water contents and laboratory measured rock properties. Using available data for physical and hydrologic properties (porosity, saturated hydraulic conductivity moisture retention functions) of the volcanic rocks, surface lithologic units that are hydrologically similar were delineated. Moisture retention and relative permeability functions were assigned to each surface unit based on the similarity of the mean porosity and saturated hydraulic conductivity of the surface unit to laboratory samples of the same lithology. The potential flux into the mountain was estimated for each surface hydrologic unit using the mean saturated hydraulic conductivity for each unit and assuming all matrix flow. Using measured moisture profiles for each of the surface units, estimates were made of the depth at which seasonal fluctuations diminish and steady state downward flux conditions are likely to exist. The hydrologic properties at that depth were used with the current relative saturation of the tuff, to estimate flux as the unsaturated hydraulic conductivity. This method assumes a unit gradient. The range in estimated flux was 0.02 mm/yr for the welded Tiva Canyon to 13.4 mm/yr for the nonwelded Paintbrush Tuff. The areally averaged flux was 1.4 mm/yr. The major zones of high flux occur to the north of the potential repository boundary where the nonwelded tuffs are exposed in the major drainages

  6. Critical heat flux (CHF) phenomenon on a downward facing curved surface

    Energy Technology Data Exchange (ETDEWEB)

    Cheung, F.B.; Haddad, K.H.; Liu, Y.C. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Mechanical Engineering

    1997-06-01

    This report describes a theoretical and experimental study of the boundary layer boiling and critical heat flux phenomena on a downward facing curved heating surface, including both hemispherical and toroidal surfaces. A subscale boundary layer boiling (SBLB) test facility was developed to measure the spatial variation of the critical heat flux and observe the underlying mechanisms. Transient quenching and steady-state boiling experiments were performed in the SBLB facility under both saturated and subcooled conditions to obtain a complete database on the critical heat flux. To complement the experimental effort, an advanced hydrodynamic CHF model was developed from the conservation laws along with sound physical arguments. The model provides a clear physical explanation for the spatial variation of the CHF observed in the SBLB experiments and for the weak dependence of the CHF data on the physical size of the vessel. Based upon the CHF model, a scaling law was established for estimating the local critical heat flux on the outer surface of a heated hemispherical vessel that is fully submerged in water. The scaling law, which compares favorably with all the available local CHF data obtained for various vessel sizes, can be used to predict the local CHF limits on large commercial-size vessels. This technical information represents one of the essential elements that is needed in assessing the efficacy of external cooling of core melt by cavity flooding as a severe accident management strategy. 83 figs., 3 tabs.

  7. Critical heat flux (CHF) phenomenon on a downward facing curved surface

    International Nuclear Information System (INIS)

    Cheung, F.B.; Haddad, K.H.; Liu, Y.C.

    1997-06-01

    This report describes a theoretical and experimental study of the boundary layer boiling and critical heat flux phenomena on a downward facing curved heating surface, including both hemispherical and toroidal surfaces. A subscale boundary layer boiling (SBLB) test facility was developed to measure the spatial variation of the critical heat flux and observe the underlying mechanisms. Transient quenching and steady-state boiling experiments were performed in the SBLB facility under both saturated and subcooled conditions to obtain a complete database on the critical heat flux. To complement the experimental effort, an advanced hydrodynamic CHF model was developed from the conservation laws along with sound physical arguments. The model provides a clear physical explanation for the spatial variation of the CHF observed in the SBLB experiments and for the weak dependence of the CHF data on the physical size of the vessel. Based upon the CHF model, a scaling law was established for estimating the local critical heat flux on the outer surface of a heated hemispherical vessel that is fully submerged in water. The scaling law, which compares favorably with all the available local CHF data obtained for various vessel sizes, can be used to predict the local CHF limits on large commercial-size vessels. This technical information represents one of the essential elements that is needed in assessing the efficacy of external cooling of core melt by cavity flooding as a severe accident management strategy. 83 figs., 3 tabs

  8. Measurement of a surface heat flux and temperature

    Science.gov (United States)

    Davis, R. M.; Antoine, G. J.; Diller, T. E.; Wicks, A. L.

    1994-04-01

    The Heat Flux Microsensor is a new sensor which was recently patented by Virginia Tech and is just starting to be marketed by Vatell Corp. The sensor is made using the thin-film microfabrication techniques directly on the material that is to be measured. It consists of several thin-film layers forming a differential thermopile across a thermal resistance layer. The measured heat flux q is proportional to the temperature difference across the resistance layer q= k(sub g)/delta(sub g) x (t(sub 1) - T(sub 2)), where k(sub g) is the thermal conductivity and delta (sub g) is the thickness of the thermal resistance layer. Because the gages are sputter coated directly onto the surface, their total thickness is less than 2 micrometers, which is two orders of magnitude thinner than previous gages. The resulting temperature difference across the thermal resistance layer (delta is less than 1 micrometer) is very small even at high heat fluxes. To generate a measurable signal many thermocouple pairs are put in series to form a differential thermopile. The combination of series thermocouple junctions and thin-film design creates a gage with very attractive characteristics. It is not only physically non-intrusive to the flow, but also causes minimal disruption of the surface temperature. Because it is so thin, the response time is less than 20 microsec. Consequently, the frequency response is flat from 0 to over 50 kHz. Moreover, the signal of the Heat Flux Microsensor is directly proportional to the heat flux. Therefore, it can easily be used in both steady and transient flows, and it measures both the steady and unsteady components of the surface heat flux. A version of the Heat Flux Microsensor has been developed to meet the harsh demands of combustion environments. These gages use platinum and platinum-10 percent rhodium as the thermoelectric materials. The thermal resistance layer is silicon monoxide and a protective coating of Al2O3 is deposited on top of the sensor. The

  9. Estimating local atmosphere-surface fluxes using eddy covariance and numerical Ogive optimization

    DEFF Research Database (Denmark)

    Sievers, Jakob; Papakyriakou, Tim; Larsen, Søren

    2014-01-01

    Estimating representative surface-fluxes using eddy covariance leads invariably to questions concerning inclusion or exclusion of low-frequency flux contributions. For studies where fluxes are linked to local physical parameters and up-scaled through numerical modeling efforts, low-frequency cont......Estimating representative surface-fluxes using eddy covariance leads invariably to questions concerning inclusion or exclusion of low-frequency flux contributions. For studies where fluxes are linked to local physical parameters and up-scaled through numerical modeling efforts, low...

  10. Global surface wind and flux fields from model assimilation of Seasat data

    Science.gov (United States)

    Atlas, R.; Busalacchi, A. J.; Kalnay, E.; Bloom, S.; Ghil, M.

    1986-01-01

    Procedures for dealiasing Seasat data and developing global surface wind and latent and sensible heat flux fields are discussed. Seasat data from September 20, 1978 was dealiased using the Goddard Laboratory for Atmospheres (GLA) analysis/forecast system. The wind data obtained with the objective GLA forecast model are compared to the data subjectively dealiased by Peteherych et al. (1984) and Hoffman (1982, 1984). The GLA procedure is also verified using simulated Seasat data. The areas of high and low heat fluxes and cyclonic and anticyclonic wind stresses detected in the generated fields are analyzed and compared to climatological fields. It is observed that there is good correlation between the time-averaged analyses of wind stress obtained subjectively and objectively, and the monthly mean wind stress and latent fluxes agree with climatological fields and atmospheric and oceanic features.

  11. Gradient flux measurements of sea–air DMS transfer during the Surface Ocean Aerosol Production (SOAP experiment

    Directory of Open Access Journals (Sweden)

    M. J. Smith

    2018-04-01

    Full Text Available Direct measurements of marine dimethylsulfide (DMS fluxes are sparse, particularly in the Southern Ocean. The Surface Ocean Aerosol Production (SOAP voyage in February–March 2012 examined the distribution and flux of DMS in a biologically active frontal system in the southwest Pacific Ocean. Three distinct phytoplankton blooms were studied with oceanic DMS concentrations as high as 25 nmol L−1. Measurements of DMS fluxes were made using two independent methods: the eddy covariance (EC technique using atmospheric pressure chemical ionization–mass spectrometry (API-CIMS and the gradient flux (GF technique from an autonomous catamaran platform. Catamaran flux measurements are relatively unaffected by airflow distortion and are made close to the water surface, where gas gradients are largest. Flux measurements were complemented by near-surface hydrographic measurements to elucidate physical factors influencing DMS emission. Individual DMS fluxes derived by EC showed significant scatter and, at times, consistent departures from the Coupled Ocean–Atmosphere Response Experiment gas transfer algorithm (COAREG. A direct comparison between the two flux methods was carried out to separate instrumental effects from environmental effects and showed good agreement with a regression slope of 0.96 (r2 = 0.89. A period of abnormal downward atmospheric heat flux enhanced near-surface ocean stratification and reduced turbulent exchange, during which GF and EC transfer velocities showed good agreement but modelled COAREG values were significantly higher. The transfer velocity derived from near-surface ocean turbulence measurements on a spar buoy compared well with the COAREG model in general but showed less variation. This first direct comparison between EC and GF fluxes of DMS provides confidence in compilation of flux estimates from both techniques, as well as in the stable periods when the observations are not well predicted by the COAREG

  12. Gradient flux measurements of sea-air DMS transfer during the Surface Ocean Aerosol Production (SOAP) experiment

    Science.gov (United States)

    Smith, Murray J.; Walker, Carolyn F.; Bell, Thomas G.; Harvey, Mike J.; Saltzman, Eric S.; Law, Cliff S.

    2018-04-01

    Direct measurements of marine dimethylsulfide (DMS) fluxes are sparse, particularly in the Southern Ocean. The Surface Ocean Aerosol Production (SOAP) voyage in February-March 2012 examined the distribution and flux of DMS in a biologically active frontal system in the southwest Pacific Ocean. Three distinct phytoplankton blooms were studied with oceanic DMS concentrations as high as 25 nmol L-1. Measurements of DMS fluxes were made using two independent methods: the eddy covariance (EC) technique using atmospheric pressure chemical ionization-mass spectrometry (API-CIMS) and the gradient flux (GF) technique from an autonomous catamaran platform. Catamaran flux measurements are relatively unaffected by airflow distortion and are made close to the water surface, where gas gradients are largest. Flux measurements were complemented by near-surface hydrographic measurements to elucidate physical factors influencing DMS emission. Individual DMS fluxes derived by EC showed significant scatter and, at times, consistent departures from the Coupled Ocean-Atmosphere Response Experiment gas transfer algorithm (COAREG). A direct comparison between the two flux methods was carried out to separate instrumental effects from environmental effects and showed good agreement with a regression slope of 0.96 (r2 = 0.89). A period of abnormal downward atmospheric heat flux enhanced near-surface ocean stratification and reduced turbulent exchange, during which GF and EC transfer velocities showed good agreement but modelled COAREG values were significantly higher. The transfer velocity derived from near-surface ocean turbulence measurements on a spar buoy compared well with the COAREG model in general but showed less variation. This first direct comparison between EC and GF fluxes of DMS provides confidence in compilation of flux estimates from both techniques, as well as in the stable periods when the observations are not well predicted by the COAREG model.

  13. Seasonal and latitudinal variations of surface fluxes at two Arctic terrestrial sites

    Science.gov (United States)

    Grachev, Andrey A.; Persson, P. Ola G.; Uttal, Taneil; Akish, Elena A.; Cox, Christopher J.; Morris, Sara M.; Fairall, Christopher W.; Stone, Robert S.; Lesins, Glen; Makshtas, Alexander P.; Repina, Irina A.

    2017-11-01

    This observational study compares seasonal variations of surface fluxes (turbulent, radiative, and soil heat) and other ancillary atmospheric/surface/permafrost data based on in-situ measurements made at terrestrial research observatories located near the coast of the Arctic Ocean. Hourly-averaged multiyear data sets collected at Eureka (Nunavut, Canada) and Tiksi (East Siberia, Russia) are analyzed in more detail to elucidate similarities and differences in the seasonal cycles at these two Arctic stations, which are situated at significantly different latitudes (80.0°N and 71.6°N, respectively). While significant gross similarities exist in the annual cycles of various meteorological parameters and fluxes, the differences in latitude, local topography, cloud cover, snowfall, and soil characteristics produce noticeable differences in fluxes and in the structures of the atmospheric boundary layer and upper soil temperature profiles. An important factor is that even though higher latitude sites (in this case Eureka) generally receive less annual incoming solar radiation but more total daily incoming solar radiation throughout the summer months than lower latitude sites (in this case Tiksi). This leads to a counter-intuitive state where the average active layer (or thaw line) is deeper and the topsoil temperature in midsummer are higher in Eureka which is located almost 10° north of Tiksi. The study further highlights the differences in the seasonal and latitudinal variations of the incoming shortwave and net radiation as well as the moderating cloudiness effects that lead to temporal and spatial differences in the structure of the atmospheric boundary layer and the uppermost ground layer. Specifically the warm season (Arctic summer) is shorter and mid-summer amplitude of the surface fluxes near solar noon is generally less in Eureka than in Tiksi. During the dark Polar night and cold seasons (Arctic winter) when the ground is covered with snow and air temperatures

  14. Reconciling surface ocean productivity, export fluxes and sediment composition in a global biogeochemical ocean model

    Directory of Open Access Journals (Sweden)

    M. Gehlen

    2006-01-01

    Full Text Available This study focuses on an improved representation of the biological soft tissue pump in the global three-dimensional biogeochemical ocean model PISCES. We compare three parameterizations of particle dynamics: (1 the model standard version including two particle size classes, aggregation-disaggregation and prescribed sinking speed; (2 an aggregation-disaggregation model with a particle size spectrum and prognostic sinking speed; (3 a mineral ballast parameterization with no size classes, but prognostic sinking speed. In addition, the model includes a description of surface sediments and organic carbon early diagenesis. Model output is compared to data or data based estimates of ocean productivity, pe-ratios, particle fluxes, surface sediment bulk composition and benthic O2 fluxes. Model results suggest that different processes control POC fluxes at different depths. In the wind mixed layer turbulent particle coagulation appears as key process in controlling pe-ratios. Parameterization (2 yields simulated pe-ratios that compare well to observations. Below the wind mixed layer, POC fluxes are most sensitive to the intensity of zooplankton flux feeding, indicating the importance of zooplankton community composition. All model parameters being kept constant, the capability of the model to reproduce yearly mean POC fluxes below 2000 m and benthic oxygen demand does at first order not dependent on the resolution of the particle size spectrum. Aggregate formation appears essential to initiate an intense biological pump. At great depth the reported close to constant particle fluxes are most likely the result of the combined effect of aggregate formation and mineral ballasting.

  15. The influence of idealized surface heterogeneity on virtual turbulent flux measurements

    Science.gov (United States)

    De Roo, Frederik; Mauder, Matthias

    2018-04-01

    The imbalance of the surface energy budget in eddy-covariance measurements is still an unsolved problem. A possible cause is the presence of land surface heterogeneity, which affects the boundary-layer turbulence. To investigate the impact of surface variables on the partitioning of the energy budget of flux measurements in the surface layer under convective conditions, we set up a systematic parameter study by means of large-eddy simulation. For the study we use a virtual control volume approach, which allows the determination of advection by the mean flow, flux-divergence and storage terms of the energy budget at the virtual measurement site, in addition to the standard turbulent flux. We focus on the heterogeneity of the surface fluxes and keep the topography flat. The surface fluxes vary locally in intensity and these patches have different length scales. Intensity and length scales can vary for the two horizontal dimensions but follow an idealized chessboard pattern. Our main focus lies on surface heterogeneity of the kilometer scale, and one order of magnitude smaller. For these two length scales, we investigate the average response of the fluxes at a number of virtual towers, when varying the heterogeneity length within the length scale and when varying the contrast between the different patches. For each simulation, virtual measurement towers were positioned at functionally different positions (e.g., downdraft region, updraft region, at border between domains, etc.). As the storage term is always small, the non-closure is given by the sum of the advection by the mean flow and the flux-divergence. Remarkably, the missing flux can be described by either the advection by the mean flow or the flux-divergence separately, because the latter two have a high correlation with each other. For kilometer scale heterogeneity, we notice a clear dependence of the updrafts and downdrafts on the surface heterogeneity and likewise we also see a dependence of the energy

  16. Intercomparison of oceanic and atmospheric forced and coupled mesoscale simulations Part I: Surface fluxes

    Directory of Open Access Journals (Sweden)

    P. Josse

    1999-04-01

    Full Text Available A mesoscale non-hydrostatic atmospheric model has been coupled with a mesoscale oceanic model. The case study is a four-day simulation of a strong storm event observed during the SEMAPHORE experiment over a 500 × 500 km2 domain. This domain encompasses a thermohaline front associated with the Azores current. In order to analyze the effect of mesoscale coupling, three simulations are compared: the first one with the atmospheric model forced by realistic sea surface temperature analyses; the second one with the ocean model forced by atmospheric fields, derived from weather forecast re-analyses; the third one with the models being coupled. For these three simulations the surface fluxes were computed with the same bulk parametrization. All three simulations succeed well in representing the main oceanic or atmospheric features observed during the storm. Comparison of surface fields with in situ observations reveals that the winds of the fine mesh atmospheric model are more realistic than those of the weather forecast re-analyses. The low-level winds simulated with the atmospheric model in the forced and coupled simulations are appreciably stronger than the re-analyzed winds. They also generate stronger fluxes. The coupled simulation has the strongest surface heat fluxes: the difference in the net heat budget with the oceanic forced simulation reaches on average 50 Wm-2 over the simulation period. Sea surface-temperature cooling is too weak in both simulations, but is improved in the coupled run and matches better the cooling observed with drifters. The spatial distributions of sea surface-temperature cooling and surface fluxes are strongly inhomogeneous over the simulation domain. The amplitude of the flux variation is maximum in the coupled run. Moreover the weak correlation between the cooling and heat flux patterns indicates that the surface fluxes are not responsible for the whole cooling and suggests that the response of the ocean mixed layer

  17. Intercomparison of oceanic and atmospheric forced and coupled mesoscale simulations Part I: Surface fluxes

    Directory of Open Access Journals (Sweden)

    H. Giordani

    Full Text Available A mesoscale non-hydrostatic atmospheric model has been coupled with a mesoscale oceanic model. The case study is a four-day simulation of a strong storm event observed during the SEMAPHORE experiment over a 500 × 500 km2 domain. This domain encompasses a thermohaline front associated with the Azores current. In order to analyze the effect of mesoscale coupling, three simulations are compared: the first one with the atmospheric model forced by realistic sea surface temperature analyses; the second one with the ocean model forced by atmospheric fields, derived from weather forecast re-analyses; the third one with the models being coupled. For these three simulations the surface fluxes were computed with the same bulk parametrization. All three simulations succeed well in representing the main oceanic or atmospheric features observed during the storm. Comparison of surface fields with in situ observations reveals that the winds of the fine mesh atmospheric model are more realistic than those of the weather forecast re-analyses. The low-level winds simulated with the atmospheric model in the forced and coupled simulations are appreciably stronger than the re-analyzed winds. They also generate stronger fluxes. The coupled simulation has the strongest surface heat fluxes: the difference in the net heat budget with the oceanic forced simulation reaches on average 50 Wm-2 over the simulation period. Sea surface-temperature cooling is too weak in both simulations, but is improved in the coupled run and matches better the cooling observed with drifters. The spatial distributions of sea surface-temperature cooling and surface fluxes are strongly inhomogeneous over the simulation domain. The amplitude of the flux variation is maximum in the coupled run. Moreover the weak correlation between the cooling and heat flux patterns indicates that the surface fluxes are not responsible for the whole cooling and suggests that the response of the ocean mixed layer

  18. Soil Carbon Dioxide Production and Surface Fluxes: Subsurface Physical Controls

    Science.gov (United States)

    Risk, D.; Kellman, L.; Beltrami, H.

    Soil respiration is a critical determinant of landscape carbon balance. Variations in soil temperature and moisture patterns are important physical processes controlling soil respiration which need to be better understood. Relationships between soil respi- ration and physical controls are typically addressed using only surface flux data but other methods also exist which permit more rigorous interpretation of soil respira- tion processes. Here we use a combination of subsurface CO_{2} concentrations, surface CO_{2} fluxes and detailed physical monitoring of the subsurface envi- ronment to examine physical controls on soil CO_{2} production at four climate observatories in Eastern Canada. Results indicate that subsurface CO_{2} produc- tion is more strongly correlated to the subsurface thermal environment than the surface CO_{2} flux. Soil moisture was also found to have an important influence on sub- surface CO_{2} production, particularly in relation to the soil moisture - soil profile diffusivity relationship. Non-diffusive profile CO_{2} transport appears to be im- portant at these sites, resulting in a de-coupling of summertime surface fluxes from subsurface processes and violating assumptions that surface CO_{2} emissions are the result solely of diffusion. These results have implications for the study of soil respiration across a broad range of terrestrial environments.

  19. Magnetic flux surface measurements at the Wendelstein 7-X stellarator

    Energy Technology Data Exchange (ETDEWEB)

    Otte, Matthias; Andreeva, Tamara; Biedermann, Christoph; Bozhenkov, Sergey; Geiger, Joachim; Sunn Pedersen, Thomas [Max-Planck-Institut fuer Plasmaphysik, Greifswald (Germany); Lazerson, Samuel [Princeton Plasma Physics Laboratory, Princeton (United States)

    2016-07-01

    Recently the first plasma operation phase of the Wendelstein 7-X stellarator has been started at IPP Greifswald. Wendelstein 7-X is an optimized stellarator with a complex superconducting magnet system consisting of 50 non-planar and 20 planar field coils and further 10 normal conducting control and 5 trim coils. The magnetic confinement and hence the expected plasma performance are decisively determined by the properties of the magnet system, especially by the existence and quality of the magnetic flux surfaces. Even small error fields may result in significant changes of the flux surface topology. Therefore, measurements of the vacuum magnetic flux surfaces have been performed before plasma operation. The first experimental results confirm the existence and quality of the flux surfaces to the full extend from low field up to the nominal field strength of B=2.5T. This includes the dedicated magnetic limiter configuration that is exclusively used for the first plasma operation. Furthermore, the measurements are indicating that the intrinsic error fields are within the tolerable range and can be controlled utilizing the trim coils as expected.

  20. On the predictability of land surface fluxes from meteorological variables

    Science.gov (United States)

    Haughton, Ned; Abramowitz, Gab; Pitman, Andy J.

    2018-01-01

    Previous research has shown that land surface models (LSMs) are performing poorly when compared with relatively simple empirical models over a wide range of metrics and environments. Atmospheric driving data appear to provide information about land surface fluxes that LSMs are not fully utilising. Here, we further quantify the information available in the meteorological forcing data that are used by LSMs for predicting land surface fluxes, by interrogating FLUXNET data, and extending the benchmarking methodology used in previous experiments. We show that substantial performance improvement is possible for empirical models using meteorological data alone, with no explicit vegetation or soil properties, thus setting lower bounds on a priori expectations on LSM performance. The process also identifies key meteorological variables that provide predictive power. We provide an ensemble of empirical benchmarks that are simple to reproduce and provide a range of behaviours and predictive performance, acting as a baseline benchmark set for future studies. We reanalyse previously published LSM simulations and show that there is more diversity between LSMs than previously indicated, although it remains unclear why LSMs are broadly performing so much worse than simple empirical models.

  1. Global observation-based diagnosis of soil moisture control on land surface flux partition

    Science.gov (United States)

    Gallego-Elvira, Belen; Taylor, Christopher M.; Harris, Phil P.; Ghent, Darren; Veal, Karen L.; Folwell, Sonja S.

    2016-04-01

    Soil moisture plays a central role in the partition of available energy at the land surface between sensible and latent heat flux to the atmosphere. As soils dry out, evapotranspiration becomes water-limited ("stressed"), and both land surface temperature (LST) and sensible heat flux rise as a result. This change in surface behaviour during dry spells directly affects critical processes in both the land and the atmosphere. Soil water deficits are often a precursor in heat waves, and they control where feedbacks on precipitation become significant. State-of-the-art global climate model (GCM) simulations for the Coupled Model Intercomparison Project Phase 5 (CMIP5) disagree on where and how strongly the surface energy budget is limited by soil moisture. Evaluation of GCM simulations at global scale is still a major challenge owing to the scarcity and uncertainty of observational datasets of land surface fluxes and soil moisture at the appropriate scale. Earth observation offers the potential to test how well GCM land schemes simulate hydrological controls on surface fluxes. In particular, satellite observations of LST provide indirect information about the surface energy partition at 1km resolution globally. Here, we present a potentially powerful methodology to evaluate soil moisture stress on surface fluxes within GCMs. Our diagnostic, Relative Warming Rate (RWR), is a measure of how rapidly the land warms relative to the overlying atmosphere during dry spells lasting at least 10 days. Under clear skies, this is a proxy for the change in sensible heat flux as soil dries out. We derived RWR from MODIS Terra and Aqua LST observations, meteorological re-analyses and satellite rainfall datasets. Globally we found that on average, the land warmed up during dry spells for 97% of the observed surface between 60S and 60N. For 73% of the area, the land warmed faster than the atmosphere (positive RWR), indicating water stressed conditions and increases in sensible heat flux

  2. Estimation of sensible and latent heat flux from natural sparse vegetation surfaces using surface renewal

    Science.gov (United States)

    Zapata, N.; Martínez-Cob, A.

    2001-12-01

    This paper reports a study undertaken to evaluate the feasibility of the surface renewal method to accurately estimate long-term evaporation from the playa and margins of an endorreic salty lagoon (Gallocanta lagoon, Spain) under semiarid conditions. High-frequency temperature readings were taken for two time lags ( r) and three measurement heights ( z) in order to get surface renewal sensible heat flux ( HSR) values. These values were compared against eddy covariance sensible heat flux ( HEC) values for a calibration period (25-30 July 2000). Error analysis statistics (index of agreement, IA; root mean square error, RMSE; and systematic mean square error, MSEs) showed that the agreement between HSR and HEC improved as measurement height decreased and time lag increased. Calibration factors α were obtained for all analyzed cases. The best results were obtained for the z=0.9 m ( r=0.75 s) case for which α=1.0 was observed. In this case, uncertainty was about 10% in terms of relative error ( RE). Latent heat flux values were obtained by solving the energy balance equation for both the surface renewal ( LESR) and the eddy covariance ( LEEC) methods, using HSR and HEC, respectively, and measurements of net radiation and soil heat flux. For the calibration period, error analysis statistics for LESR were quite similar to those for HSR, although errors were mostly at random. LESR uncertainty was less than 9%. Calibration factors were applied for a validation data subset (30 July-4 August 2000) for which meteorological conditions were somewhat different (higher temperatures and wind speed and lower solar and net radiation). Error analysis statistics for both HSR and LESR were quite good for all cases showing the goodness of the calibration factors. Nevertheless, the results obtained for the z=0.9 m ( r=0.75 s) case were still the best ones.

  3. Scaling of surface energy fluxes using remotely sensed data

    Science.gov (United States)

    French, Andrew Nichols

    Accurate estimates of evapotranspiration (ET) across multiple terrains would greatly ease challenges faced by hydrologists, climate modelers, and agronomists as they attempt to apply theoretical models to real-world situations. One ET estimation approach uses an energy balance model to interpret a combination of meteorological observations taken at the surface and data captured by remote sensors. However, results of this approach have not been accurate because of poor understanding of the relationship between surface energy flux and land cover heterogeneity, combined with limits in available resolution of remote sensors. The purpose of this study was to determine how land cover and image resolution affect ET estimates. Using remotely sensed data collected over El Reno, Oklahoma, during four days in June and July 1997, scale effects on the estimation of spatially distributed ET were investigated. Instantaneous estimates of latent and sensible heat flux were calculated using a two-source surface energy balance model driven by thermal infrared, visible-near infrared, and meteorological data. The heat flux estimates were verified by comparison to independent eddy-covariance observations. Outcomes of observations taken at coarser resolutions were simulated by aggregating remote sensor data and estimated surface energy balance components from the finest sensor resolution (12 meter) to hypothetical resolutions as coarse as one kilometer. Estimated surface energy flux components were found to be significantly dependent on observation scale. For example, average evaporative fraction varied from 0.79, using 12-m resolution data, to 0.93, using 1-km resolution data. Resolution effects upon flux estimates were related to a measure of landscape heterogeneity known as operational scale, reflecting the size of dominant landscape features. Energy flux estimates based on data at resolutions less than 100 m and much greater than 400 m showed a scale-dependent bias. But estimates

  4. Soil surface CO2 flux in a boreal black spruce fire chronosequence

    Science.gov (United States)

    Wang, Chuankuan; Bond-Lamberty, Ben; Gower, Stith T.

    2003-02-01

    Understanding the effects of wildfire on the carbon (C) cycle of boreal forests is essential to quantifying the role of boreal forests in the global carbon cycle. Soil surface CO2 flux (Rs), the second largest C flux in boreal forests, is directly and indirectly affected by fire and is hypothesized to change during forest succession following fire. The overall objective of this study was to measure and model Rs for a black spruce (Picea mariana [Mill.] BSP) postfire chronosequence in northern Manitoba, Canada. The experiment design was a nested factorial that included two soil drainage classes (well and poorly drained) × seven postfire aged stands. Specific objectives were (1) to quantify the relationship between Rs and soil temperature for different aged boreal black spruce forests in well-drained and poorly drained soil conditions, (2) to examine Rs dynamics along postfire successional stands, and (3) to estimate annual soil surface CO2 flux for these ecosystems. Soil surface CO2 flux was significantly affected by soil drainage class (p = 0.014) and stand age (p = 0.006). Soil surface CO2 flux was positively correlated to soil temperature (R2 = 0.78, p aged stand combination. Soil surface CO2 flux was significantly greater at the well-drained than the poorly drained stands (p = 0.007) during growing season. Annual soil surface CO2 flux for the 1998, 1995, 1989, 1981, 1964, 1930, and 1870 burned stands averaged 226, 412, 357, 413, 350, 274, and 244 g C m-2 yr-1 in the well-drained stands and 146, 380, 300, 303, 256, 233, and 264 g C m-2 yr-1 in the poorly drained stands. Soil surface CO2 flux during the winter (from 1 November to 30 April) comprised from 5 to 19% of the total annual Rs. We speculate that the smaller soil surface CO2 flux in the recently burned than the older stands is mainly caused by decreased root respiration.

  5. Surface energy budget and turbulent fluxes at Arctic terrestrial sites

    Science.gov (United States)

    Grachev, Andrey; Persson, Ola; Uttal, Taneil; Konopleva-Akish, Elena; Crepinsek, Sara; Cox, Christopher; Fairall, Christopher; Makshtas, Alexander; Repina, Irina

    2017-04-01

    Determination of the surface energy budget (SEB) and all SEB components at the air-surface interface are required in a wide variety of applications including atmosphere-land/snow simulations and validation of the surface fluxes predicted by numerical models over different spatial and temporal scales. Here, comparisons of net surface energy budgets at two Arctic sites are made using long-term near-continuous measurements of hourly averaged surface fluxes (turbulent, radiation, and soil conduction). One site, Eureka (80.0 N; Nunavut, Canada), is located in complex topography near a fjord about 200 km from the Arctic Ocean. The other site, Tiksi (71.6 N; Russian East Siberia), is located on a relatively flat coastal plain less than 1 km from the shore of Tiksi Bay, a branch of the Arctic Ocean. We first analyzed diurnal and annual cycles of basic meteorological parameters and key SEB components at these locations. Although Eureka and Tiksi are located on different continents and at different latitudes, the annual course of the surface meteorology and SEB components are qualitatively similar. Surface energy balance closure is a formulation of the conservation of energy principle. Our direct measurements of energy balance for both Arctic sites show that the sum of the turbulent sensible and latent heat fluxes and the ground (conductive) heat flux systematically underestimate the net radiation by about 25-30%. This lack of energy balance closure is a fundamental and pervasive problem in micrometeorology. We discuss a variety of factors which may be responsible for the lack of SEB closure. In particular, various storage terms (e.g., air column energy storage due to radiative and/or sensible heat flux divergence, ground heat storage above the soil flux plate, energy used in photosynthesis, canopy biomass heat storage). For example, our observations show that the photosynthesis storage term is relatively small (about 1-2% of the net radiation), but about 8-12% of the

  6. Atmosphere–Surface Fluxes of CO2 using Spectral Techniques

    DEFF Research Database (Denmark)

    Sørensen, Lise Lotte; Larsen, Søren Ejling

    2010-01-01

    Different flux estimation techniques are compared here in order to evaluate air–sea exchange measurement methods used on moving platforms. Techniques using power spectra and cospectra to estimate fluxes are presented and applied to measurements of wind speed and sensible heat, latent heat and CO2...... fluxes. Momentum and scalar fluxes are calculated from the dissipation technique utilizing the inertial subrange of the power spectra and from estimation of the cospectral amplitude, and both flux estimates are compared to covariance derived fluxes. It is shown how even data having a poor signal......-to-noise ratio can be used for flux estimations....

  7. A Numerical Study on Impact of Taiwan Island Surface Heat Flux on Super Typhoon Haitang (2005

    Directory of Open Access Journals (Sweden)

    Hongxiong Xu

    2015-01-01

    Full Text Available Three to four tropical cyclones (TCs by average usually impact Taiwan every year. This study, using the Developmental Tested Center (DTC version of the Hurricane WRF (HWRF model, examines the effects of Taiwan’s island surface heat fluxes on typhoon structure, intensity, track, and its rainfall over the island. The numerical simulation successfully reproduced the structure and intensity of super Typhoon Haitang. The model, especially, reproduced the looped path and landfall at nearly the right position. Sensitive experiments indicated that Taiwan’s surface heat fluxes have significant influence on the super Typhoon Haitang. Compared to sensible heat (SH fluxes, latent heat (LH is the dominant factor affecting the intensity and rainfall, but they showed opposite effects on intensity and rainfall. LH (SH flux of Taiwan Island intensified (weakened Typhoon Haitang’s intensity and structure by transferring more energy from (to surface. However, only LH played a major role in the looped path before the landfall of the Typhoon Haitang.

  8. SIERRA-Flux: Measuring Regional Surface Fluxes of Carbon Dioxide, Methane, and Water Vapor from an Unmanned Aircraft System

    Science.gov (United States)

    Fladeland; Yates, Emma Louise; Bui, Thaopaul Van; Dean-Day, Jonathan; Kolyer, Richard

    2011-01-01

    The Eddy-Covariance Method for quantifying surface-atmosphere fluxes is a foundational technique for measuring net ecosystem exchange and validating regional-to-global carbon cycle models. While towers or ships are the most frequent platform for measuring surface-atmosphere exchange, experiments using aircraft for flux measurements have yielded contributions to several large-scale studies including BOREAS, SMACEX, RECAB by providing local-to-regional coverage beyond towers. The low-altitude flight requirements make airborne flux measurements particularly dangerous and well suited for unmanned aircraft.

  9. Roughness Length of Water Vapor over Land Surfaces and Its Influence on Latent Heat Flux

    Directory of Open Access Journals (Sweden)

    Sang-Jong Park

    2010-01-01

    Full Text Available Latent heat flux at the surface is largely dependent on the roughness length for water vapor (z0q. The determination of z0q is still uncertain because of its multifaceted characteristics of surface properties, atmospheric conditions and insufficient observations. In this study, observed values from the Fluxes Over Snow Surface II field experiment (FLOSS-II from November 2002 to March 2003 were utilized to estimate z0q over various land surfaces: bare soil, snow, and senescent grass. The present results indicate that the estimated z0q over bare soil is much smaller than the roughness length of momentum (z0m; thus, the ratio z0m/z0q is larger than those of previous studies by a factor of 20 - 150 for the available flow regime of the roughness Reynolds number, Re* > 0.1. On the snow surface, the ratio is comparable to a previous estimation for the rough flow (Re* > 1, but smaller by a factor of 10 - 50 as the flow became smooth (Re* < 1. Using the estimated ratio, an optimal regression equation of z0m/z0q is determined as a function of Re* for each surface type. The present parameterization of the ratio is found to greatly reduce biases of latent heat flux estimation compared with that estimated by the conventional method, suggesting the usefulness of current parameterization for numerical modeling.

  10. Plasma-surface interactions under high heat and particle fluxes

    NARCIS (Netherlands)

    De Temmerman, G.; Bystrov, K.; Liu, F.; Liu, W.; Morgan, T.; Tanyeli, I.; van den Berg, M.; Xu, H.; Zielinski, J.

    2013-01-01

    The plasma-surface interactions expected in the divertor of a future fusion reactor are characterized by extreme heat and particle fluxes interacting with the plasma-facing surfaces. Powerful linear plasma generators are used to reproduce the expected plasma conditions and allow plasma-surface

  11. Solar flux incident on an orbiting surface after reflection from a planet

    Science.gov (United States)

    Modest, M. F.

    1980-01-01

    Algorithms describing the solar radiation impinging on an infinitesimal surface after reflection from a gray and diffuse planet are derived. The following conditions apply: only radiation from the sunny half of the planet is taken into account; the radiation must fall on the top of the orbiting surface, and radiation must come from that part of the planet that can be seen from the orbiting body. A simple approximate formula is presented which displays excellent accuracy for all significant situations, with an error which is always less than 5% of the maximum possible reflected flux. Attention is also given to solar albedo flux on a surface directly facing the planet, the influence of solar position on albedo flux, and to solar albedo flux as a function of the surface-planet tilt angle.

  12. An extended rational thermodynamics model for surface excess fluxes

    NARCIS (Netherlands)

    Sagis, L.M.C.

    2012-01-01

    In this paper, we derive constitutive equations for the surface excess fluxes in multiphase systems, in the context of an extended rational thermodynamics formalism. This formalism allows us to derive Maxwell–Cattaneo type constitutive laws for the surface extra stress tensor, the surface thermal

  13. Aram Chaos and its constraints on the surface heat flux of Mars

    NARCIS (Netherlands)

    Schumacher, S.; Zegers, T.E.

    2011-01-01

    The surface heat flux of a planet is an important parameter to characterize its internal activity and to determine its thermal evolution. Here we report on a new method to constrain the surface heat flux of Mars during the Hesperian. For this, we explore the consequences for the martian surface

  14. Study on a Dynamic Vegetation Model for Simulating Land Surface Flux Exchanges at Lien-Hua-Chih Flux Observation Site in Taiwan

    Science.gov (United States)

    Yeh, T. Y.; Li, M. H.; Chen, Y. Y.; Ryder, J.; McGrath, M.; Otto, J.; Naudts, K.; Luyssaert, S.; MacBean, N.; Bastrikov, V.

    2016-12-01

    Dynamic vegetation model ORCHIDEE (Organizing Carbon and Hydrology In Dynamic EcosystEms) is a state of art land surface component of the IPSL (Institute Pierre Simon Laplace) Earth System Model. It has been used world-wide to investigate variations of water, carbon, and energy exchanges between the land surface and the atmosphere. In this study we assessed the applicability of using ORCHIDEE-CAN, a new feature with 3-D CANopy structure (Naudts et al., 2015; Ryder et al., 2016), to simulate surface fluxes measured at tower-based eddy covariance fluxes at the Lien-Hua-Chih experimental watershed in Taiwan. The atmospheric forcing including radiation, air temperature, wind speed, and the dynamics of vertical canopy structure for driving the model were obtained from the observations site. Suitable combinations of default plant function types were examined to meet in-situ observations of soil moisture and leaf area index from 2009 to 2013. The simulated top layer soil moisture was ranging from 0.1 to 0.4 and total leaf area was ranging from 2.2 to 4.4, respectively. A sensitivity analysis was performed to investigate the sensitive of model parameters and model skills of ORCHIDEE-CAN on capturing seasonal variations of surface fluxes. The most sensitive parameters were suggested and calibrated by an automatic data assimilation tool ORCHDAS (ORCHIDEE Data Assimilation Systems; http://orchidas.lsce.ipsl.fr/). Latent heat, sensible heat, and carbon fluxes simulated by the model were compared with long-term observations at the site. ORCHIDEE-CAN by making use of calibrated surface parameters was used to study variations of land-atmosphere interactions on a variety of temporal scale in associations with changes in both land and atmospheric conditions. Ref: Naudts, K., et al.,: A vertically discretised canopy description for ORCHIDEE (SVN r2290) and the modifications to the energy, water and carbon fluxes, Geoscientific Model Development, 8, 2035-2065, doi:10.5194/gmd-8

  15. Modelling and analysis of flux surface mapping experiments on W7-X

    Science.gov (United States)

    Lazerson, Samuel; Otte, Matthias; Bozhenkov, Sergey; Sunn Pedersen, Thomas; Bräuer, Torsten; Gates, David; Neilson, Hutch; W7-X Team

    2015-11-01

    The measurement and compensation of error fields in W7-X will be key to the device achieving high beta steady state operations. Flux surface mapping utilizes the vacuum magnetic flux surfaces, a feature unique to stellarators and heliotrons, to allow direct measurement of magnetic topology, and thereby allows a highly accurate determination of remnant magnetic field errors. As will be reported separately at this meeting, the first measurements confirming the existence of nested flux surfaces in W7-X have been made. In this presentation, a synthetic diagnostic for the flux surface mapping diagnostic is presented. It utilizes Poincaré traces to construct an image of the flux surface consistent with the measured camera geometry, fluorescent rod sweep plane, and emitter beam position. Forward modeling of the high-iota configuration will be presented demonstrating an ability to measure the intrinsic error field using the U.S. supplied trim coil system on W7-X, and a first experimental assessment of error fields in W7-X will be presented. This work has been authored by Princeton University under Contract Number DE-AC02-09CH11466 with the US Department of Energy.

  16. Using radiometric surface temperature for surface energy flux estimation in Mediterranean drylands from a two-source perspective

    DEFF Research Database (Denmark)

    Morillas, L.; Garcia Garcia, Monica; Nieto Solana, Hector

    2013-01-01

    A two-source model (TSM) for surface energy balance, considering explicitly soil and vegetation components, was tested under water stress conditions. The TSM evaluated estimates the sensible heat flux (H) using the surface-air thermal gradient and the latent heat flux (LE) as a residual from the ...

  17. An intercomparison between the surface heat flux feedback in five coupled models, COADS and the NCEP reanalysis

    Energy Technology Data Exchange (ETDEWEB)

    Frankignoul, C.; Kestenare, E. [Universite Pierre et Marie Curie, Institute Pierre-Simon Laplace, Laboratoire d' Oceanographie Dynamique et de Climatologie, 4 place Jussieu, 75252 Paris Cedex 05 (France); Botzet, M. [Max-Planck-Institut fuer Meteorologie, Hamburg (Germany); Carril, A.F. [Istituto Nazionale di Geofisica e Vulcanologia, Bologna (Italy); Drange, H. [Nansen Environmental and Remote Sensing Center, Bergen (Norway); Pardaens, A. [Hadley Centre for Climate Prediction and Research, Met Office (United Kingdom); Terray, L.; Sutton, R. [Department of Meteorology, University of Reading (United Kingdom)

    2004-04-01

    The surface heat flux feedback is estimated in the Atlantic and the extra-tropical Indo-Pacific, using monthly heat flux and sea surface temperature anomaly data from control simulations with five global climate models, and it is compared to estimates derived from COADS and the NCEP reanalysis. In all data sets, the heat flux feedback is negative nearly everywhere and damps the sea surface temperature anomalies. At extra-tropical latitudes, it is strongly dominated by the turbulent fluxes. The radiative feedback can be positive or negative, depending on location and season, but it remains small, except in some models in the tropical Atlantic. The negative heat flux feedback is strong in the mid-latitude storm tracks, exceeding 40 W m{sup -2} K{sup -1} at place, but in the Northern Hemisphere it is substantially underestimated in several models. The negative feedback weakens at high latitudes, although the models do not reproduce the weak positive feedback found in NCEP in the northern North Atlantic. The main differences are found in the tropical Atlantic where the heat flux feedback is weakly negative in some models, as in the observations, and strongly negative in others where it can exceed 30 W m{sup -2} K{sup -1} at large scales, in part because of a strong contribution of the radiative fluxes, in particular during spring. A comparison between models with similar atmospheric or oceanic components suggests that the atmospheric model is primarily responsible for the heat flux feedback differences at extra-tropical latitudes. In the tropical Atlantic, the ocean behavior plays an equal role. The differences in heat flux feedback in the tropical Atlantic are reflected in the sea surface temperature anomaly persistence, which is too small in models where the heat flux damping is large. A good representation of the heat flux feedback is thus required to simulate climate variability realistically. (orig.)

  18. Surface radiant flux densities inferred from LAC and GAC AVHRR data

    Science.gov (United States)

    Berger, F.; Klaes, D.

    To infer surface radiant flux densities from current (NOAA-AVHRR, ERS-1/2 ATSR) and future meteorological (Envisat AATSR, MSG, METOP) satellite data, the complex, modular analysis scheme SESAT (Strahlungs- und Energieflüsse aus Satellitendaten) could be developed (Berger, 2001). This scheme allows the determination of cloud types, optical and microphysical cloud properties as well as surface and TOA radiant flux densities. After testing of SESAT in Central Europe and the Baltic Sea catchment (more than 400scenes U including a detailed validation with various surface measurements) it could be applied to a large number of NOAA-16 AVHRR overpasses covering the globe.For the analysis, two different spatial resolutions U local area coverage (LAC) andwere considered. Therefore, all inferred results, like global area coverage (GAC) U cloud cover, cloud properties and radiant properties, could be intercompared. Specific emphasis could be made to the surface radiant flux densities (all radiative balance compoments), where results for different regions, like Southern America, Southern Africa, Northern America, Europe, and Indonesia, will be presented. Applying SESAT, energy flux densities, like latent and sensible heat flux densities could also be determined additionally. A statistical analysis of all results including a detailed discussion for the two spatial resolutions will close this study.

  19. Comparison of energy fluxes at the land surface-atmosphere interface in an Alpine valley as simulated with different models

    Directory of Open Access Journals (Sweden)

    G. Grossi

    2003-01-01

    Full Text Available Within the framework of a research project coupling meteorological and hydrological models in mountainous areas a distributed Snow-Soil-Vegetation-Atmosphere Transfer model was developed and applied to simulate the energy fluxes at the land surface – atmosphere interface in an Alpine valley (Toce Valley - North Italy during selected flood events in the last decade. Energy fluxes simulated by the distributed energy transfer model were compared with those simulated by a limited area meteorological model for the event of June 1997 and the differences in the spatial and temporal distribution. The Snow/Soil-Vegetation-Atmosphere Transfer model was also applied to simulate the energy fluxes at the land surface-atmosphere interface for a single cell, assumed to be representative of the Siberia site (Toce Valley, where a micro-meteorological station was installed and operated for 2.5 months in autumn 1999. The Siberia site is very close to the Nosere site, where a standard meteorological station was measuring precipitation, air temperature and humidity, global and net radiation and wind speed during the same special observing period. Data recorded by the standard meteorological station were used to force the energy transfer model and simulate the point energy fluxes at the Siberia site, while turbulent fluxes observed at the Siberia site were used to derive the latent heat flux from the energy balance equation. Finally, the hourly evapotranspiration flux computed by this procedure was compared to the evapotranspiration flux simulated by the energy transfer model. Keywords: energy exchange processes, land surface-atmosphere interactions, turbulent fluxes

  20. Influences of biomass heat and biochemical energy storages on the land surface fluxes and radiative temperature

    Science.gov (United States)

    Gu, Lianhong; Meyers, Tilden; Pallardy, Stephen G.; Hanson, Paul J.; Yang, Bai; Heuer, Mark; Hosman, Kevin P.; Liu, Qing; Riggs, Jeffery S.; Sluss, Dan; Wullschleger, Stan D.

    2007-01-01

    The interest of this study was to develop an initial assessment on the potential importance of biomass heat and biochemical energy storages for land-atmosphere interactions, an issue that has been largely neglected so far. We conducted flux tower observations and model simulations at a temperate deciduous forest site in central Missouri in the summer of 2004. The model used was the comprehensive terrestrial ecosystem Fluxes and Pools Integrated Simulator (FAPIS). We first examined FAPIS performance by testing its predictions with and without the representation of biomass energy storages against measurements of surface energy and CO2 fluxes. We then evaluated the magnitudes and temporal patterns of the biomass energy storages calculated by FAPIS. Finally, the effects of biomass energy storages on land-atmosphere exchanges of sensible and latent heat fluxes and variations of land surface radiative temperature were investigated by contrasting FAPIS simulations with and without these storage terms. We found that with the representation of the two biomass energy storage terms, FAPIS predictions agreed with flux tower measurements fairly well; without the representation, however, FAPIS performance deteriorated for all predicted surface energy flux terms although the effect on the predicted CO2 flux was minimal. In addition, we found that the biomass heat storage and biochemical energy storage had clear diurnal patterns with typical ranges from -50 to 50 and -3 to 20 W m-2, respectively; these typical ranges were exceeded substantially when there were sudden changes in atmospheric conditions. Furthermore, FAPIS simulations without the energy storages produced larger sensible and latent heat fluxes during the day but smaller fluxes (more negative values) at night as compared with simulations with the energy storages. Similarly, without-storage simulations had higher surface radiative temperature during the day but lower radiative temperature at night, indicating that the

  1. Surface fluxes in heterogeneous landscape

    Energy Technology Data Exchange (ETDEWEB)

    Bay Hasager, C

    1997-01-01

    The surface fluxes in homogeneous landscapes are calculated by similarity scaling principles. The methodology is well establish. In heterogeneous landscapes with spatial changes in the micro scale range, i e from 100 m to 10 km, advective effects are significant. The present work focus on these effects in an agricultural countryside typical for the midlatitudes. Meteorological and satellite data from a highly heterogeneous landscape in the Rhine Valley, Germany was collected in the large-scale field experiment TRACT (Transport of pollutants over complex terrain) in 1992. Classified satellite images, Landsat TM and ERS SAR, are used as basis for roughness maps. The roughnesses were measured at meteorological masts in the various cover classes and assigned pixel by pixel to the images. The roughness maps are aggregated, i e spatially averaged, into so-called effective roughness lengths. This calculation is performed by a micro scale aggregation model. The model solves the linearized atmospheric flow equations by a numerical (Fast Fourier Transform) method. This model also calculate maps of friction velocity and momentum flux pixel wise in heterogeneous landscapes. It is indicated how the aggregation methodology can be used to calculate the heat fluxes based on the relevant satellite data i e temperature and soil moisture information. (au) 10 tabs., 49 ills., 223 refs.

  2. Comparison of mesoscale model and tower measurements of surface fluxes during Winter Icing and Storms Program/Atmospheric Radiation Measurement 91

    International Nuclear Information System (INIS)

    Oncley, S.P.; Dudhia, J.

    1994-01-01

    This study is an evaluation of the ability of the Pennsylvania State University/National Center for Atmospheric Research (NCAR) mesoscale model (MM4) to determine surface fluxes to see if measured fluxes should be assimilated into model runs. Fluxes were compared from a high-resolution (5 km grid spacing) MM4 run during one day of the Winter Icing and Storms Programs/Atmospheric Radiation Measurement (WISP/ARM) experiment (over NE Colorado in winter 1991) with direct flux measurements made from a tower over a representative site by a three-dimensional sonic anemometer and fast response temperature and humidity sensors. This tower was part of the NCAR Atmosphere-Surface Turbulent Exchange Research (ASTER) facility. Also, mean values were compared to check whether any differences were due to the model parameterization or model variables

  3. Spatial and temporal patterns of land surface fluxes from remotely sensed surface temperatures within an uncertainty modelling framework

    Directory of Open Access Journals (Sweden)

    M. F. McCabe

    2005-01-01

    Full Text Available Characterising the development of evapotranspiration through time is a difficult task, particularly when utilising remote sensing data, because retrieved information is often spatially dense, but temporally sparse. Techniques to expand these essentially instantaneous measures are not only limited, they are restricted by the general paucity of information describing the spatial distribution and temporal evolution of evaporative patterns. In a novel approach, temporal changes in land surface temperatures, derived from NOAA-AVHRR imagery and a generalised split-window algorithm, are used as a calibration variable in a simple land surface scheme (TOPUP and combined within the Generalised Likelihood Uncertainty Estimation (GLUE methodology to provide estimates of areal evapotranspiration at the pixel scale. Such an approach offers an innovative means of transcending the patch or landscape scale of SVAT type models, to spatially distributed estimates of model output. The resulting spatial and temporal patterns of land surface fluxes and surface resistance are used to more fully understand the hydro-ecological trends observed across a study catchment in eastern Australia. The modelling approach is assessed by comparing predicted cumulative evapotranspiration values with surface fluxes determined from Bowen ratio systems and using auxiliary information such as in-situ soil moisture measurements and depth to groundwater to corroborate observed responses.

  4. Heterogeneous surface fluxes and their effects on the SGP CART site

    International Nuclear Information System (INIS)

    Doran, J.C.; Hu, Q.; Hubbe, J.M.; Liljegren, J.C.; Shaw, W.J.; Zhong, S.; Collatz, G.J.

    1995-03-01

    The treatment of subgrid-scale variations of surface properties and the resultant spatial variations of sensible and latent heat fluxes has received increasing attention in recent years. Mesoscale numerical simulations of highly idealized conditions, in which strong flux contrasts exist between adjacent surfaces, have shown that under some circumstances the secondary circulations induced by land-use differences can significantly affect the properties of the planetary boundary layer (PBL) and the region of the atmosphere above the PBL. At the Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) site, the fluxes from different land-surface types are not expected to differ as dramatically as those found in idealized simulations. Although the corresponding effects on the atmosphere should thus be less dramatic, they are still potentially important. From an ARM perspective, in tests of single column models (SCMs) it would be useful to understand the effects of the lower boundary conditions on model performance. We describe here our initial efforts to characterize the variable surface fluxes over the CART site and to assess their effects on the PBL that are important for the performance of SCMs

  5. Flux surface shape and current profile optimization in tokamaks

    International Nuclear Information System (INIS)

    Dobrott, D.R.; Miller, R.L.

    1977-01-01

    Axisymmetric tokamak equilibria of noncircular cross section are analyzed numerically to study the effects of flux surface shape and current profile on ideal and resistive interchange stability. Various current profiles are examined for circles, ellipses, dees, and doublets. A numerical code separately analyzes stability in the neighborhood of the magnetic axis and in the remainder of the plasma using the criteria of Mercier and Glasser, Greene, and Johnson. Results are interpreted in terms of flux surface averaged quantities such as magnetic well, shear, and the spatial variation in the magnetic field energy density over the cross section. The maximum stable β is found to vary significantly with shape and current profile. For current profiles varying linearly with poloidal flux, the highest β's found were for doublets. Finally, an algorithm is presented which optimizes the current profile for circles and dees by making the plasma everywhere marginally stable

  6. Material fluxes on the surface of the earth

    National Research Council Canada - National Science Library

    National Research Council Staff; Commission on Geosciences, Environment and Resources; Division on Earth and Life Studies; Board on Earth Sciences & Resources; National Research Council; National Academy of Sciences

    ...) level of surficial fluxes and their dynamics. Leading experts in the field offer a historical perspective on geofluxes and discuss the cycles of materials on the earth's surface, from weathering processes to the movement of material...

  7. Are ghost surfaces quadratic-flux-minimizing?

    International Nuclear Information System (INIS)

    Hudson, S.R.; Dewar, R.L.

    2009-01-01

    Two candidates for 'almost-invariant' toroidal surfaces passing through magnetic islands, namely quadratic-flux-minimizing (QFMin) surfaces and ghost surfaces, use families of periodic pseudo-orbits (i.e. paths for which the action is not exactly extremal). QFMin pseudo-orbits, which are coordinate-dependent, are field lines obtained from a modified magnetic field, and ghost-surface pseudo-orbits are obtained by displacing closed field lines in the direction of steepest descent of magnetic action, ∫A.dl. A generalized Hamiltonian definition of ghost surfaces is given and specialized to the usual Lagrangian definition. A modified Hamilton's Principle is introduced that allows the use of Lagrangian integration for calculation of the QFMin pseudo-orbits. Numerical calculations show QFMin and Lagrangian ghost surfaces give very similar results for a chaotic magnetic field perturbed from an integrable case, and this is explained using a perturbative construction of an auxiliary poloidal angle for which QFMin and Lagrangian ghost surfaces are the same up to second order. While presented in the context of 3-dimensional magnetic field line systems, the concepts are applicable to defining almost-invariant tori in other 11/2 degree-of-freedom nonintegrable Lagrangian/Hamiltonian systems.

  8. A Surface Temperature Initiated Closure (STIC) for surface energy balance fluxes

    DEFF Research Database (Denmark)

    Mallick, Kaniska; Jarvis, Andrew J.; Boegh, Eva

    2014-01-01

    The use of Penman–Monteith (PM) equation in thermal remote sensing based surface energy balance modeling is not prevalent due to the unavailability of any direct method to integrate thermal data into the PM equation and due to the lack of physical models expressing the surface (or stomatal......) and boundary layer conductances (gS and gB) as a function of surface temperature. Here we demonstrate a new method that physically integrates the radiometric surface temperature (TS) into the PM equation for estimating the terrestrial surface energy balance fluxes (sensible heat, H and latent heat, λ......E). The method combines satellite TS data with standard energy balance closure models in order to derive a hybrid closure that does not require the specification of surface to atmosphere conductance terms. We call this the Surface Temperature Initiated Closure (STIC), which is formed by the simultaneous solution...

  9. Recent trends (2003-2013) of land surface heat fluxes on the southern side of the central Himalayas, Nepal

    Science.gov (United States)

    Amatya, Pukar Man; Ma, Yaoming; Han, Cunbo; Wang, Binbin; Devkota, Lochan Prasad

    2015-12-01

    Novice efforts have been made in order to study the regional distribution of land surface heat fluxes on the southern side of the central Himalayas utilizing high-resolution remotely sensed products, but these have been on instantaneous scale. In this study the Surface Energy Balance System model is used to obtain annual averaged maps of the land surface heat fluxes for 11 years (2003-2013) and study their annual trends on the central Himalayan region. The maps were derived at 5 km resolution using monthly input products ranging from satellite derived to Global Land Data Assimilation System meteorological data. It was found that the net radiation flux is increasing as a result of decreasing precipitation (drier environment). The sensible heat flux did not change much except for the northwestern High Himalaya and High Mountains. In northwestern High Himalaya sensible heat flux is decreasing because of decrease in wind speed, ground-air temperature difference, and increase in winter precipitation, whereas in High Mountains it is increasing due to increase in ground-air temperature difference and high rate of deforestation. The latent heat flux has an overall increasing trend with increase more pronounced in the lower regions compared to high elevated regions. It has been reported that precipitation is decreasing with altitude in this region. Therefore, the increasing trend in latent heat flux can be attributed to increase in net radiation flux under persistent forest cover and irrigation land used for agriculture.

  10. Soil heat flux and day time surface energy balance closure at ...

    Indian Academy of Sciences (India)

    Soil heat flux is an important input component of surface energy balance. Estimates of soil heat flux were ... mate source of energy for all physical and bio- logical processes ... May) account for major thunderstorm activity in the state and winter ...

  11. Quantifying Surface Energy Flux Estimation Uncertainty Using Land Surface Temperature Observations

    Science.gov (United States)

    French, A. N.; Hunsaker, D.; Thorp, K.; Bronson, K. F.

    2015-12-01

    Remote sensing with thermal infrared is widely recognized as good way to estimate surface heat fluxes, map crop water use, and detect water-stressed vegetation. When combined with net radiation and soil heat flux data, observations of sensible heat fluxes derived from surface temperatures (LST) are indicative of instantaneous evapotranspiration (ET). There are, however, substantial reasons LST data may not provide the best way to estimate of ET. For example, it is well known that observations and models of LST, air temperature, or estimates of transport resistances may be so inaccurate that physically based model nevertheless yield non-meaningful results. Furthermore, using visible and near infrared remote sensing observations collected at the same time as LST often yield physically plausible results because they are constrained by less dynamic surface conditions such as green fractional cover. Although sensitivity studies exist that help identify likely sources of error and uncertainty, ET studies typically do not provide a way to assess the relative importance of modeling ET with and without LST inputs. To better quantify model benefits and degradations due to LST observational inaccuracies, a Bayesian uncertainty study was undertaken using data collected in remote sensing experiments at Maricopa, Arizona. Visible, near infrared and thermal infrared data were obtained from an airborne platform. The prior probability distribution of ET estimates were modeled using fractional cover, local weather data and a Penman-Monteith mode, while the likelihood of LST data was modeled from a two-source energy balance model. Thus the posterior probabilities of ET represented the value added by using LST data. Results from an ET study over cotton grown in 2014 and 2015 showed significantly reduced ET confidence intervals when LST data were incorporated.

  12. Influence of surface conditions in nucleate boiling--the concept of bubble flux density

    International Nuclear Information System (INIS)

    Shoukri, M.; Judd, R.L.

    1978-01-01

    A study of the influence of surface conditions in nucleate pool boiling is presented. The surface conditions are represented by the number and distribution of the active nucleation sites as well as the size and size distribution of the cavities that constitute the nucleation sites. The heat transfer rate during nucleate boiling is shown to be influenced by the surface condition through its effect on the number and distribution of the active nucleation sites as well as the frequency of bubble departure from each of these different size cavities. The concept of bubble flux density, which is a function of both the active site density and frequency of bubble departure, is introduced. A method of evaluating the bubble flux density is proposed and a uniform correlation between the boiling heat flux and the bubble flux density is found to exist for a particular solid-liquid combination irrespective of the surface finish within the region of isolated bubbles

  13. Direct evaluation of transient surface temperatures and heat fluxes

    International Nuclear Information System (INIS)

    Axford, R.A.

    1975-08-01

    Evaluations of transient surface temperatures resulting from the absorption of radiation are required in laser fusion reactor systems studies. A general method for the direct evaluation of transient surface temperatures and heat fluxes on the boundaries of bounded media is developed by constructing fundamental solutions of the scalar Helmholtz equation and performing certain elementary integrations

  14. Calibration of a distributed hydrology and land surface model using energy flux measurements

    DEFF Research Database (Denmark)

    Larsen, Morten Andreas Dahl; Refsgaard, Jens Christian; Jensen, Karsten H.

    2016-01-01

    In this study we develop and test a calibration approach on a spatially distributed groundwater-surface water catchment model (MIKE SHE) coupled to a land surface model component with particular focus on the water and energy fluxes. The model is calibrated against time series of eddy flux measure...

  15. Understanding the behavior of carbon dioxide and surface energy fluxes in semiarid Salt Lake Valley, Utah, USA

    Science.gov (United States)

    Ramamurthy, Prathap

    This dissertation reports the findings from the Salt Lake Valley flux study. The Salt Lake Valley flux study was designed to improve our understanding of the complex land-atmosphere interactions in urban areas. The flux study used the eddy covariance technique to quantify carbon dioxide and surface energy budget in the semiarid Salt Lake Valley. Apart from quantifying fluxes, the study has also added new insight into the nature of turbulent scalar transport in urban areas and has addressed some of the complications in using Eddy Covariance technique in urban areas. As part of this experiment, eddy fluxes of CO2 and surface energy fluxes were measured at two sites, with distinct urban landforms; One site was located in a suburban neighborhood with substantial vegetative cover, prototypical of many residential neighborhoods in the valley. The other CO2 site was in a preurban surrounding that resembled the Salt Lake Valley before it was urbanized. The two sites were intentionally chosen to illustrate the impact of urbanization on CO 2 and surface energy flux cycles. Results indicate that the suburban site acted as a sink of CO2 during the midday period due to photosynthesis and acted as a source of CO2 during the evening and nighttime periods. The vegetative cover around the suburban site also had a significant impact on the surface energy fluxes. Contribution from latent heat flux was substantially high at the suburban site during the summer months compared to sensible heat. The turbulence investigation found that the general behavior of turbulence was very much influenced by local factors and the statistics did not always obey Monin-Obukhov Similarity parameters. This investigation also found that the scalar (co)spectra observed at the suburban site were characterized by multiple peaks and were different compared to (co)spectra reported over forest and crop canopies. The study also observed multiscale CO2 transport at the suburban site during the convective period

  16. Measurements of flux surfaces in the ATF torsatron

    International Nuclear Information System (INIS)

    England, A.C.; Colchin, R.J.; Harris, J.H.; Hillis, D.L.; Jernigan, T.C.; Anderson, F.S.B.

    1989-01-01

    Flux surfaces in the advanced toroidal facility (ATF) torsatron have been measured using electron-beam techniques. The beam was injected toroidally and impinged on a phosphor-coated screen located ∼ 180 degrees from the gun. The gun was mounted on a drive mechanism that enabled the beam to scan the entire cross section of the last closed flux surface in ATF. The screen material was st. steel, coated with ZnO:Zn (P-15 or P-24) phosphor, and the transparency was ∼ 90%. The emitted light was detected with an image-intensified CCD camera that viewed the mesh through a nearby port. The images were displayed directly on a TV monitor and stored on video tape. Frames from the video tape were transferred to a computer, where the image was enhanced and transformed to remove spatial distortions due to the lens and the viewing angle of the camera

  17. Sequential cryogen spraying for heat flux control at the skin surface

    Science.gov (United States)

    Majaron, Boris; Aguilar, Guillermo; Basinger, Brooke; Randeberg, Lise L.; Svaasand, Lars O.; Lavernia, Enrique J.; Nelson, J. Stuart

    2001-05-01

    Heat transfer rate at the skin-air interface is of critical importance for the benefits of cryogen spray cooling in combination with laser therapy of shallow subsurface skin lesions, such as port-wine stain birthmarks. With some cryogen spray devices, a layer of liquid cryogen builds up on the skin surface during the spurt, which may impair heat transfer across the skin surface due to relatively low thermal conductivity and potentially higher temperature of the liquid cryogen layer as compared to the spray droplets. While the mass flux of cryogen delivery can be adjusted by varying the atomizing nozzle geometry, this may strongly affect other spray properties, such as lateral spread (cone), droplet size, velocity, and temperature distribution. We present here first experiments with sequential cryogen spraying, which may enable accurate mass flux control through variation of spray duty cycle, while minimally affecting other spray characteristics. The observed increase of cooling rate and efficiency at moderate duty cycle levels supports the above described hypothesis of isolating liquid layer, and demonstrates a novel approach to optimization of cryogen spray devices for individual laser dermatological applications.

  18. Estimating surface turbulent heat fluxes from land surface temperature and soil moisture using the particle batch smoother

    Science.gov (United States)

    Lu, Yang; Dong, Jianzhi; Steele-Dunne, Susan; van de Giesen, Nick

    2016-04-01

    This study is focused on estimating surface sensible and latent heat fluxes from land surface temperature (LST) time series and soil moisture observations. Surface turbulent heat fluxes interact with the overlying atmosphere and play a crucial role in meteorology, hydrology and other climate-related fields, but in-situ measurements are costly and difficult. It has been demonstrated that the time series of LST contains information of energy partitioning and that surface turbulent heat fluxes can be determined from assimilation of LST. These studies are mainly based on two assumptions: (1) a monthly value of bulk heat transfer coefficient under neutral conditions (CHN) which scales the sum of the fluxes, and (2) an evaporation fraction (EF) which stays constant during the near-peak hours of the day. Previous studies have applied variational and ensemble approaches to this problem. Here the newly developed particle batch smoother (PBS) algorithm is adopted to test its capability in this application. The PBS can be seen as an extension of the standard particle filter (PF) in which the states and parameters within a fix window are updated in a batch using all observations in the window. The aim of this study is two-fold. First, the PBS is used to assimilate only LST time series into the force-restore model to estimate fluxes. Second, a simple soil water transfer scheme is introduced to evaluate the benefit of assimilating soil moisture observations simultaneously. The experiments are implemented using the First ISLSCP (International Satellite Land Surface Climatology Project) (FIFE) data. It is shown that the restored LST time series using PBS agrees very well with observations, and that assimilating LST significantly improved the flux estimation at both daily and half-hourly time scales. When soil moisture is introduced to further constrain EF, the accuracy of estimated EF is greatly improved. Furthermore, the RMSEs of retrieved fluxes are effectively reduced at both

  19. Plateau diffusion coefficient for arbitrary flux surface geometry

    International Nuclear Information System (INIS)

    Meier, H.K.; Hirshman, S.P.; Sigmar, D.J.; Lao, L.L.

    1981-03-01

    A relatively simple but accurate representation has been developed for magnetic flux surfaces; it is valid for finite β and it describes configurations with both ellipticity and D-shape. This representation has been applied to the computation of the diffusion coefficient in the plateau regime

  20. Annual and latitudinal variations of surface fluxes and meteorological variables at Arctic terrestrial sites

    Science.gov (United States)

    Grachev, Andrey; Uttal, Taneil; Persson, Ola; Konopleva-Akish, Elena; Crepinsek, Sara; Cox, Christopher; Fairall, Christopher; Makshtas, Alexander; Repina, Irina

    2016-04-01

    This study analyzes and discusses seasonal and latitudinal variations of surface fluxes (turbulent, radiative, and soil ground heat) and other ancillary surface/snow/permafrost data based on in-situ measurements made at two long-term research observatories near the coast of the Arctic Ocean located in Canada and Russia. The hourly averaged data collected at Eureka (Canadian territory of Nunavut) and Tiksi (East Siberia) located at two quite different latitudes (80.0 N and 71.6 N respectively) are analyzed in details to describe the seasons in the Arctic. Although Eureka and Tiksi are located at the different continents and at the different latitudes, the annual course of the surface meteorology and the surface fluxes are qualitatively very similar. The air and soil temperatures display the familiar strong seasonal trend with maximum of measured temperatures in mid-summer and minimum during winter. According to our data, variation in incoming short-wave solar radiation led the seasonal pattern of the air and soil temperatures, and the turbulent fluxes. During the dark Polar nights, air and ground temperatures are strongly controlled by long-wave radiation associated generally with cloud cover. Due to the fact that in average the higher latitudes receive less solar radiation than lower latitudes, a length of the convective atmospheric boundary layer (warm season) is shorter and middle-summer amplitude of the turbulent fluxes is generally less in Eureka than in Tiksi. However, since solar elevation angle at local midnight in the middle of Arctic summer is higher for Eureka as compared to Tiksi, stable stratification and upward turbulent flux for carbon dioxide is generally did not observed at Eureka site during summer seasons. It was found a high correlation between the turbulent fluxes of sensible and latent heat, carbon dioxide and the net solar radiation. A comprehensive evaluation of energy balance closure problem is performed based on the multi-year data sets

  1. Flux pinning and flux flow studies in superconductors using flux flow noise techniques. Progress report, April 1, 1976--December 17, 1976

    International Nuclear Information System (INIS)

    Joiner, W.C.H.

    1976-12-01

    Measurements of flux flow noise power spectra have been combined with critical current measurements and measurements of current-voltage characteristics to study flux flow and local pinning interactions effective during flux flow. A model of flux flow noise generation in the presence of local pinning interactions is developed and applied to situations where pinning is dominated by: (1) grain boundaries, (2) normal metal precipitates in a superconducting matrix, (3) gross deformation producing a critical current peak effect, and (4) surface grooves imposed on a sample surface. In the case of pinning caused by normal metal precipitates in a superconducting matrix, unusual training and hysterisis effects are observed in the flux flow characteristics. The greater sensitivity of noise spectra, as compared with bulk critical current measurements, in obtaining a detailed picture of flux flow is emphasized

  2. Methodology for estimation of time-dependent surface heat flux due to cryogen spray cooling.

    Science.gov (United States)

    Tunnell, James W; Torres, Jorge H; Anvari, Bahman

    2002-01-01

    Cryogen spray cooling (CSC) is an effective technique to protect the epidermis during cutaneous laser therapies. Spraying a cryogen onto the skin surface creates a time-varying heat flux, effectively cooling the skin during and following the cryogen spurt. In previous studies mathematical models were developed to predict the human skin temperature profiles during the cryogen spraying time. However, no studies have accounted for the additional cooling due to residual cryogen left on the skin surface following the spurt termination. We formulate and solve an inverse heat conduction (IHC) problem to predict the time-varying surface heat flux both during and following a cryogen spurt. The IHC formulation uses measured temperature profiles from within a medium to estimate the surface heat flux. We implement a one-dimensional sequential function specification method (SFSM) to estimate the surface heat flux from internal temperatures measured within an in vitro model in response to a cryogen spurt. Solution accuracy and experimental errors are examined using simulated temperature data. Heat flux following spurt termination appears substantial; however, it is less than that during the spraying time. The estimated time-varying heat flux can subsequently be used in forward heat conduction models to estimate temperature profiles in skin during and following a cryogen spurt and predict appropriate timing for onset of the laser pulse.

  3. Determination of Surface Fluxes Using a Bowen Ratio System

    African Journals Online (AJOL)

    USER

    Components of the surface fluxes of the energy balance equation were determined ... and vapour pressure in combination with point measurements of net .... approaches zero, then almost all the energy available is used in evapotranspiration.

  4. Surface layer scintillometry for estimating the sensible heat flux component of the surface energy balance

    Directory of Open Access Journals (Sweden)

    M. J. Savage

    2010-01-01

    Full Text Available The relatively recently developed scintillometry method, with a focus on the dual-beam surface layer scintillometer (SLS, allows boundary layer atmospheric turbulence, surface sensible heat and momentum flux to be estimated in real-time. Much of the previous research using the scintillometer method has involved the large aperture scintillometer method, with only a few studies using the SLS method. The SLS method has been mainly used by agrometeorologists, hydrologists and micrometeorologists for atmospheric stability and surface energy balance studies to obtain estimates of sensible heat from which evaporation estimates representing areas of one hectare or larger are possible. Other applications include the use of the SLS method in obtaining crucial input parameters for atmospheric dispersion and turbulence models. The SLS method relies upon optical scintillation of a horizontal laser beam between transmitter and receiver for a separation distance typically between 50 and 250 m caused by refractive index inhomogeneities in the atmosphere that arise from turbulence fluctuations in air temperature and to a much lesser extent the fluctuations in water vapour pressure. Measurements of SLS beam transmission allow turbulence of the atmosphere to be determined, from which sub-hourly, real-time and in situ path-weighted fluxes of sensible heat and momentum may be calculated by application of the Monin-Obukhov similarity theory. Unlike the eddy covariance (EC method for which corrections for flow distortion and coordinate rotation are applied, no corrections to the SLS measurements, apart from a correction for water vapour pressure, are applied. Also, path-weighted SLS estimates over the propagation path are obtained. The SLS method also offers high temporal measurement resolution and usually greater spatial coverage compared to EC, Bowen ratio energy balance, surface renewal and other sensible heat measurement methods. Applying the shortened surface

  5. The influence of land surface parameters on energy flux densities derived from remote sensing data

    Energy Technology Data Exchange (ETDEWEB)

    Tittebrand, A.; Schwiebus, A. [Inst. for Hydrology und Meteorology, TU Dresden (Germany); Berger, F.H. [Observatory Lindenberg, German Weather Service, Lindenberg (Germany)

    2005-04-01

    Knowledge of the vegetation properties surface reflectance, normalised difference vegetation index (NDVI) and leaf area index (LAI) are essential for the determination of the heat and water fluxes between terrestrial ecosystems and the atmosphere. Remote sensing data can be used to derive spatial estimates of the required surface properties. The determination of land surface parameters and their influence on radiant and energy flux densities is investigated with data of different remote sensing systems. Sensitivity studies show the importance of correctly derived land surface properties to estimate the key quantity of the hydrological cycle, the evapotranspiration (L.E), most exactly. In addition to variable parameters like LAI or NDVI there are also parameters which are can not be inferred from satellite data but needed for the Penman-Monteith approach. Fixed values are assumed for these variables because they have little influence on L.E. Data of Landsat-7 ETM+ and NOAA-16 AVHRR are used to show results in different spatial resolution. The satellite derived results are compared with ground truth data provided by the Observatory Lindenberg of the German Weather Service. (orig.)

  6. Noble Gas Surface Flux Simulations And Atmospheric Transport

    Energy Technology Data Exchange (ETDEWEB)

    Carrigan, Charles R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Sun, Yunwei [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Simpson, Matthew D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2017-09-30

    Signatures from underground nuclear explosions or UNEs are strongly influenced by the containment regime surrounding them. The degree of gas leakage from the detonation cavity to the surface obviously affects the magnitude of surface fluxes of radioxenon that might be detected during the course of a Comprehensive Test Ban Treaty On-Site Inspection. In turn, the magnitude of surface fluxes will influence the downwind detectability of the radioxenon atmospheric signature from the event. Less obvious is the influence that leakage rates have on the evolution of radioxenon isotopes in the cavity or the downwind radioisotopic measurements that might be made. The objective of this letter report is to summarize our attempt to better understand how containment conditions affect both the detection and interpretation of radioxenon signatures obtained from sampling at the ground surface near an event as well as at greater distances in the atmosphere. In the discussion that follows, we make no attempt to consider other sources of radioactive noble gases such as natural backgrounds or atmospheric contamination and, for simplicity, only focus on detonation-produced radioxenon gases. Summarizing our simulations, they show that the decay of radioxenon isotopes (e.g., Xe-133, Xe-131m, Xe-133m and Xe-135) and their migration to the surface following a UNE means that the possibility of detecting these gases exists within a window of opportunity. In some cases, seeps or venting of detonation gases may allow significant quantities to reach the surface and be released into the atmosphere immediately following a UNE. In other release scenarios – the ones we consider here – hours to days may be required for gases to reach the surface at detectable levels. These release models are most likely more characteristic of “fully contained” events that lack prompt venting, but which still leak gas slowly across the surface for periods of months.

  7. Response of concrete exposed to a high heat flux on one surface

    International Nuclear Information System (INIS)

    Muir, J.F.

    1977-11-01

    Experiments were performed to investigate the response of concrete to severe thermal environments such as might be encountered during the interaction of molten reactor core materials with the containment substructure following a hypothetical fuel melt accident. The dominant mechanism for erosion of both limestone and basaltic concrete appears to be melting of the cementitious material in the matrix. The erosion proceeded in a quiescent manner with negligible spallation. The erosion rate increased with heat flux, becoming as large as approximately 70 cm/hr for a net surface heat flux of roughly 190 W/cm 2 . Analyses reveal the surface temperature to be the single most significant parameter affecting the net surface heat flux, through its importance to emitted radiation; and that the greatest fraction of the net energy transmitted to the concrete goes into sensible heat

  8. Comparison of sea surface flux measured by instrumented aircraft and ship during SOFIA and SEMAPHORE experiments

    Science.gov (United States)

    Durand, Pierre; Dupuis, HéLèNe; Lambert, Dominique; BéNech, Bruno; Druilhet, Aimé; Katsaros, Kristina; Taylor, Peter K.; Weill, Alain

    1998-10-01

    Two major campaigns (Surface of the Oceans, Fluxes and Interactions with the Atmosphere (SOFIA) and Structure des Echanges Mer-Atmosphère, Propriétés des Hétérogénéités Océaniques: Recherche Expérimentale (SEMAPHORE)) devoted to the study of ocean-atmosphere interaction were conducted in 1992 and 1993, respectively, in the Azores region. Among the various platforms deployed, instrumented aircraft and ship allowed the measurement of the turbulent flux of sensible heat, latent heat, and momentum. From coordinated missions we can evaluate the sea surface fluxes from (1) bulk relations and mean measurements performed aboard the ship in the atmospheric surface layer and (2) turbulence measurements aboard aircraft, which allowed the flux profiles to be estimated through the whole atmospheric boundary layer and therefore to be extrapolated toward the sea surface level. Continuous ship fluxes were calculated with bulk coefficients deduced from inertial-dissipation measurements in the same experiments, whereas aircraft fluxes were calculated with eddy-correlation technique. We present a comparison between these two estimations. Although momentum flux agrees quite well, aircraft estimations of sensible and latent heat flux are lower than those of the ship. This result is surprising, since aircraft momentum flux estimates are often considered as much less accurate than scalar flux estimates. The various sources of errors on the aircraft and ship flux estimates are discussed. For sensible and latent heat flux, random errors on aircraft estimates, as well as variability of ship flux estimates, are lower than the discrepancy between the two platforms, whereas the momentum flux estimates cannot be considered as significantly different. Furthermore, the consequence of the high-pass filtering of the aircraft signals on the flux values is analyzed; it is weak at the lowest altitudes flown and cannot therefore explain the discrepancies between the two platforms but becomes

  9. High-frequency pressure variations in the vicinity of a surface CO2 flux chamber

    Science.gov (United States)

    Eugene S. Takle; James R. Brandle; R. A. Schmidt; Rick Garcia; Irina V. Litvina; William J. Massman; Xinhua Zhou; Geoffrey Doyle; Charles W. Rice

    2003-01-01

    We report measurements of 2Hz pressure fluctuations at and below the soil surface in the vicinity of a surface-based CO2 flux chamber. These measurements were part of a field experiment to examine the possible role of pressure pumping due to atmospheric pressure fluctuations on measurements of surface fluxes of CO2. Under the moderate wind speeds, warm temperatures,...

  10. Characterization of land surface energy fluxes in a tropical lowland rice paddy

    Science.gov (United States)

    Chatterjee, Dibyendu; Tripathi, Rahul; Chatterjee, Sumanta; Debnath, Manish; Shahid, Mohammad; Bhattacharyya, Pratap; Swain, Chinmaya Kumar; Tripathy, Rojalin; Bhattacharya, Bimal K.; Nayak, Amaresh Kumar

    2018-04-01

    A field experiment was conducted in 2015 to study the land surface energy fluxes from tropical lowland rice paddy in eastern India with an objective to determine the mass, momentum, and energy exchange rates between rice paddies and the atmosphere. All the land surface energy fluxes were measured by eddy covariance (EC) system (make Campbell Scientific) in dry season (DS, 1-125 Julian days), dry fallow (DF, 126-181 Julian days), wet season (WS, 182-324 Julian days), and wet fallow (WF, 325-365 Julian days). The rice was cultivated in dry season (January-May) and wet season (July-November) in low wet lands and the ground is kept fallow during the remainder of the year. Results showed that albedo varied from 0.09 to 0.24 and showed positive value from morning 6:00 h until evening 18:00 h. Mean soil temperature (T g) was highest in DF, while the skin temperature (T s) was highest in WS. Average Bowen ratio (B) ranged from 0.21 to 0.64 and large variation in B was observed during the fallow periods as compared to the cropping seasons. The magnitude of aerodynamic, canopy, and climatological resistances increased with the progress of cropping season and their magnitudes decreased during the end of both cropping seasons and found minimum during the fallow periods. At a constant vapor pressure deficit (VPD) at 0.16, 0.18, 0.15, and 0.43 kPa, latent heat flux (LE) initially increased, but later it tended to level off with an increase in VPD. The actual evapotranspiration (ETa) during both the cropping seasons was higher than the fallow period. This study can be used as a source of default values for many land surface energy fluxes which are required in various meteorological or air-quality models for rice paddies. A larger imbalance of energy was observed during the wet season as the energy is stored and perhaps advected in the fresh water.

  11. Regional-Scale Surface Magnetic Fields and Proton Fluxes to Mercury's Surface from Proton-Reflection Magnetometry

    Science.gov (United States)

    Winslow, R. M.; Johnson, C. L.; Anderson, B. J.; Gershman, D. J.; Raines, J. M.; Lillis, R. J.; Korth, H.; Slavin, J. A.; Solomon, S. C.; Zurbuchen, T.

    2014-12-01

    The application of a recently developed proton-reflection magnetometry technique to MESSENGER spacecraft observations at Mercury has yielded two significant findings. First, loss-cone observations directly confirm particle precipitation to Mercury's surface and indicate that solar wind plasma persistently bombards the planet not only in the magnetic cusp regions but over a large fraction of the southern hemisphere. Second, the inferred surface field strengths independently confirm the north-south asymmetry in Mercury's global magnetic field structure first documented from observations of magnetic equator crossings. Here we extend this work with 1.5 additional years of observations (i.e., to 2.5 years in all) to further probe Mercury's surface magnetic field and better resolve proton flux precipitation to the planet's surface. We map regions where proton loss cones are observed; these maps indicate regions where protons precipitate directly onto the surface. The augmentation of our data set over that used in our original study allows us to examine the proton loss cones in cells of dimension 10° latitude by 20° longitude in Mercury body-fixed coordinates. We observe a transition from double-sided to single-sided loss cones in the pitch-angle distributions; this transition marks the boundary between open and closed field lines. At the surface this boundary lies between 60° and 70°N. Our observations allow the estimation of surface magnetic field strengths in the northern cusp region and the calculation of incident proton fluxes to both hemispheres. In the northern cusp, our regional-scale observations are consistent with an offset dipole field and a dipole moment of 190 nT RM3, where RM is Mercury's radius, implying that any regional-scale variations in surface magnetic field strengths are either weak relative to the dipole field or occur at length scales smaller than the resolution of our observations (~300 km). From the global proton flux map (north of 40° S

  12. Calculation of gamma-ray flux density above the Venus and Earth surfaces

    International Nuclear Information System (INIS)

    Surkov, Yu.A.; Manvelyan, O.S.

    1987-01-01

    Calculational results of dependence of flux density of nonscattered gamma-quanta on the height above the Venus and Earth planet surfaces are presented in the paper. Areas, where a certain part of gamma quanta is accumulated, are calaculted for each height. Spectra of scattered gamma quanta and their integral fluxes at different heights above the Venera planet surface are calculated. Effect of the atmosphere on gamma radiation recorded is considered. The results obtained allow to estimate optimal conditions for measuring gamma-fields above the Venus and Earth planet surfaces, to determine the area of the planet surface investigated. They are also necessary to determine the elementary composition of the rock according to the characteristic gamma radiation spectrum recorded

  13. Evaluating Surface Radiation Fluxes Observed From Satellites in the Southeastern Pacific Ocean

    Science.gov (United States)

    Pinker, R. T.; Zhang, B.; Weller, R. A.; Chen, W.

    2018-03-01

    This study is focused on evaluation of current satellite and reanalysis estimates of surface radiative fluxes in a climatically important region. It uses unique observations from the STRATUS Ocean Reference Station buoy in a region of persistent marine stratus clouds 1,500 km off northern Chile during 2000-2012. The study shows that current satellite estimates are in better agreement with buoy observations than model outputs at a daily time scale and that satellite data depict well the observed annual cycle in both shortwave and longwave surface radiative fluxes. Also, buoy and satellite estimates do not show any significant trend over the period of overlap or any interannual variability. This verifies the stability and reliability of the satellite data and should make them useful to examine El Niño-Southern Oscillation variability influences on surface radiative fluxes at the STRATUS site for longer periods for which satellite record is available.

  14. Surface fluxes and water balance of spatially varying vegetation within a small mountainous headwater catchment

    Directory of Open Access Journals (Sweden)

    G. N. Flerchinger

    2010-06-01

    Full Text Available Precipitation variability and complex topography often create a mosaic of vegetation communities in mountainous headwater catchments, creating a challenge for measuring and interpreting energy and mass fluxes. Understanding the role of these communities in modulating energy, water and carbon fluxes is critical to quantifying the variability in energy, carbon, and water balances across landscapes. The focus of this paper was: (1 to demonstrate the utility of eddy covariance (EC systems in estimating the evapotranspiration component of the water balance of complex headwater mountain catchments; and (2 to compare and contrast the seasonal surface energy and carbon fluxes across a headwater catchment characterized by large variability in precipitation and vegetation cover. Eddy covariance systems were used to measure surface fluxes over sagebrush (Artemesia arbuscula and Artemesia tridentada vaseyana, aspen (Populus tremuloides and the understory of grasses and forbs beneath the aspen canopy. Peak leaf area index of the sagebrush, aspen, and aspen understory was 0.77, 1.35, and 1.20, respectively. The sagebrush and aspen canopies were subject to similar meteorological forces, while the understory of the aspen was sheltered from the wind. Missing periods of measured data were common and made it necessary to extrapolate measured fluxes to the missing periods using a combination of measured and simulated data. Estimated cumulative evapotranspiratation from the sagebrush, aspen trees, and aspen understory were 384 mm, 314 mm and 185 mm. A water balance of the catchment indicated that of the 699 mm of areal average precipitation, 421 mm was lost to evapotranspiration, and 254 mm of streamflow was measured from the catchment; water balance closure for the catchment was within 22 mm. Fluxes of latent heat and carbon for all sites were minimal through the winter. Growing season fluxes of latent heat and carbon were consistently higher

  15. Observed Screen (Air) and GCM Surface/Screen Temperatures: Implications for Outgoing Longwave Fluxes at the Surface.

    Science.gov (United States)

    Garratt, J. R.

    1995-05-01

    There is direct evidence that excess net radiation calculated in general circulation models at continental surfaces [of about 11-17 W m2 (20%-27%) on an annual ~1 is not only due to overestimates in annual incoming shortwave fluxes [of 9-18 W m2 (6%-9%)], but also to underestimates in outgoing longwave fluxes. The bias in the outgoing longwave flux is deduced from a comparison of screen-air temperature observations, available as a global climatology of mean monthly values, and model-calculated surface and screen-air temperatures. An underestimate in the screen temperature computed in general circulation models over continents, of about 3 K on an annual basis, implies an underestimate in the outgoing longwave flux, averaged in six models under study, of 11-15 W m2 (3%-4%). For a set of 22 inland stations studied previously, the residual bias on an annual basis (the residual is the net radiation minus incoming shortwave plus outgoing longwave) varies between 18 and 23 W m2 for the models considered. Additional biases in one or both of the reflected shortwave and incoming longwave components cannot be ruled out.

  16. Mercury fluxes from air/surface interfaces in paddy field and dry land

    Energy Technology Data Exchange (ETDEWEB)

    Zhu Jinshan [Key Laboratory of Eco-Environments in Three Gorges Reservoir Region (Ministry of Education), College of Resources and Environment, Southwest University, No. 216, Tiansheng Street, Beibei, Chongqing 400715 (China); Wang Dingyong, E-mail: dywang@swu.edu.cn [Key Laboratory of Eco-Environments in Three Gorges Reservoir Region (Ministry of Education), College of Resources and Environment, Southwest University, No. 216, Tiansheng Street, Beibei, Chongqing 400715 (China)] [Chongqing Key Laboratory of Agricultural Resources and Environment, Chongqing 400716 (China); Liu Xiao; Zhang Yutong [Key Laboratory of Eco-Environments in Three Gorges Reservoir Region (Ministry of Education), College of Resources and Environment, Southwest University, No. 216, Tiansheng Street, Beibei, Chongqing 400715 (China)

    2011-02-15

    Research highlights: {yields} It was found that agricultural fields are important local atmospheric Hg sources in the region. {yields} The Hg emissions from dry cornfield were higher than those from the flooded rice paddy, higher mercury emissions in the warm season than the cold season, and during daytime than at night. {yields} Mercury evasion is strongly related to solar radiation which is important in the emission of Hg at both sites. - Abstract: In order to provide insight into the characteristics of Hg exchange in soil/water-air surface from cropland (including paddy field and dry land), Hg fluxes were measured in Chengjiang. Mercury fluxes were measured using the dynamic flux chamber method, coupled with a Lumex (registered) multifunctional Hg analyzer RA-915{sup +} (Lumex Ltd., Russia). The Hg fluxes from paddy field and dry land were alternatively measured every 30 min. Data were collected for 24-48 h once per month for 5 months. Mercury fluxes in both fields were synchronously measured under the same conditions to compare Hg emissions between paddy field and dry land over diurnal and seasonal periods and find out what factors affect Hg emission on each surface. These results indicated that air Hg concentrations at the monitoring site was double the value observed at the global background sites in Europe and North America. The Hg release fluxes were 46.5 {+-} 22.8 ng m{sup -2} h{sup -1} in the warm season, 15.5 {+-} 18.8 ng m{sup -2} h{sup -1} in the cold season for dry land, and 23.8 {+-} 15.6 ng m{sup -2} h{sup -1} in the warm season, 6.3 {+-} 11.9 ng m{sup -2} h{sup -1} in the cold season for paddy field. Solar radiation is important in the emission of Hg over both sites. Hg exchange at the soil/air and water/air interfaces showed temporal variations. The amount of Hg emission from dry land was higher than that from the paddy field, and the emission in daytime was higher than that at night. Moreover, Hg emissions from land covered by crops, was lower

  17. Critical heat flux for downward-facing pool boiling on CANDU calandria tube surface

    Energy Technology Data Exchange (ETDEWEB)

    Behdadi, Azin, E-mail: behdada@mcmaster.ca; Talebi, Farshad; Luxat, John

    2017-04-15

    Highlights: • Pressure tube-calandria tube contact may challenge fuel channel integrity in CANDU. • Critical heat flux variation is predicted on the outer surface of CANDU calandria tube. • A two-phase boundary layer flow driven by buoyancy is modeled on the surface. • Different slip ratios and flow regimes are considered inside the boundary layer. • Subcooling effects are added to the model using wall heat flux partitioning. - Abstract: One accident scenario in CANDU reactors that can challenge the integrity of the primary pressure boundary is a loss of coolant accident, referred to as critical break LOCA, in which the pressure tube (PT) can undergo thermal creep strain deformation and contact its calandria tube (CT). In such case, rapid redistribution of stored heat from PT to CT, leads to a large spike in heat flux to the moderator which can cause bubble accumulation and dryout on the CT surface. A challenge to fuel channel integrity is posed if critical heat flux occurs on the surface of the CT and results in sustained film boiling. If the post-dryout temperature becomes sufficiently high then continued creep strain of the PT and CT may lead to fuel channel failure. In this study, a mechanistic model is developed to predict the critical heat flux variations along the downward facing outer surface of CT. The hydrodynamic model considers a liquid macrolayer beneath an elongated vapor slug on the surface. Local dryout is postulated to occur whenever the fresh liquid supply to the macrolayer is not sufficient to compensate for the liquid depletion. A boundary layer analysis is performed, treating the two phase motion as an external buoyancy driven flow. The model shows good agreement with the available experimental data and has been modified to take into account the effect of subcooling.

  18. Stair-Step Particle Flux Spectra on the Lunar Surface: Evidence for Nonmonotonic Potentials?

    Science.gov (United States)

    Collier, Michael R.; Newheart, Anastasia; Poppe, Andrew R.; Hills, H. Kent; Farrell, William M.

    2016-01-01

    We present examples of unusual "stair-step" differential flux spectra observed by the Apollo 14 Suprathermal Ion Detector Experiment on the lunar dayside surface in Earth's magnetotail. These spectra exhibit a relatively constant differential flux below some cutoff energy and then drop off precipitously, by about an order of magnitude or more, at higher energies. We propose that these spectra result from photoions accelerated on the lunar dayside by nonmonotonic potentials (i.e.,potentials that do not decay to zero monotonically) and present a model for the expected differential flux. The energy of the cutoff and the magnitude of the differential flux are related to the properties of the local space environment and are consistent with the observed flux spectra. If this interpretation is correct, these surface-based ion observations provide a unique perspective that both complements and enhances the conclusions obtained by remote-sensing orbiter observations on the Moon's exospheric and electrostatic properties.

  19. Enhancing surface methane fluxes from an oligotrophic lake: exploring the microbubble hypothesis.

    Science.gov (United States)

    McGinnis, Daniel F; Kirillin, Georgiy; Tang, Kam W; Flury, Sabine; Bodmer, Pascal; Engelhardt, Christof; Casper, Peter; Grossart, Hans-Peter

    2015-01-20

    Exchange of the greenhouse gases carbon dioxide (CO2) and methane (CH4) across inland water surfaces is an important component of the terrestrial carbon (C) balance. We investigated the fluxes of these two gases across the surface of oligotrophic Lake Stechlin using a floating chamber approach. The normalized gas transfer rate for CH4 (k600,CH4) was on average 2.5 times higher than that for CO2 (k600,CO2) and consequently higher than Fickian transport. Because of its low solubility relative to CO2, the enhanced CH4 flux is possibly explained by the presence of microbubbles in the lake’s surface layer. These microbubbles may originate from atmospheric bubble entrainment or gas supersaturation (i.e., O2) or both. Irrespective of the source, we determined that an average of 145 L m(–2) d(–1) of gas is required to exit the surface layer via microbubbles to produce the observed elevated k600,CH4. As k600 values are used to estimate CH4 pathways in aquatic systems, the presence of microbubbles could alter the resulting CH4 and perhaps C balances. These microbubbles will also affect the surface fluxes of other sparingly soluble gases in inland waters, including O2 and N2.

  20. Surface Buoyancy Fluxes and the Strength of the Subpolar Gyre

    Science.gov (United States)

    Hogg, A. M.; Gayen, B.

    2017-12-01

    Midlatitude ocean gyres have long been considered to be driven by the mechanical wind stress on the ocean's surface (strictly speaking, the potential vorticity input from wind stress curl). However, surface buoyancy forcing (i.e. heating/cooling or freshening/salinification) also modifies the potential vorticity at the surface. Here, we present a simple argument to demonstrate that ocean gyres may (in principle) be driven by surface buoyancy forcing. This argument is derived in two ways: A Direct Numerical Simulation, driven purely by buoyancy forcing, which generates strong nonlinear gyers in the absence of wind stress; and A series of idealised eddy-resolving numerical ocean model simulations, in which wind stress and buoyancy flux are varied independently and together, are used to understand the relative importance of these two types of forcing. In these simulations, basin-scale gyres and western boundary currents with realistic magnitudes, remain even in the absence of mechanical forcing by surface wind stress. These results support the notion that surface buoyancy forcing can reorganise the potential vorticity in the ocean in such a way as to drive basin-scale gyres. The role of buoyancy is stronger in the subpolar gyre than in the subtropical gyre. We infer that surface buoyancy fluxes are likely to play a contributing role in governing the strength, variability and predictability of the North Atlantic subpolar gyre.

  1. Critical heat flux on micro-structured zircaloy surfaces for flow boiling of water at low pressures

    International Nuclear Information System (INIS)

    Haas, C.; Miassoedov, A.; Schulenberg, T.; Wetzel, T.

    2012-01-01

    The influence of surface structure on critical heat flux for flow boiling of water was investigated for Zircaloy tubes in a vertical annular test section. The objectives were to find suitable surface modification processes for Zircaloy tubes and to test their critical heat flux performance in comparison to the smooth tube. Surface structures with micro-channels, porous layer, oxidized layer, and elevations in micro- and nano-scale were produced on a section of a Zircaloy cladding tube. These modified tubes were tested in an internally heated vertical annulus with a heated length of 326 mm and an inner and outer diameter of 9.5 and 18 mm. The experiments were performed with mass fluxes of 250 and 400 kg/(m 2 s), outlet pressures between 120 and 300 kPa, and constant inlet subcooling enthalpy of 167 kJ/kg. Only a small influence of modified surface structures on critical heat flux was observed for the pressure of 120 kPa in the present test section geometry. However, with increasing pressure the critical heat flux could increase up to 29% using the surface structured tubes with micro-channels, porous and oxidized layers. Capillary effects and increased nucleation site density are assumed to improve the critical heat flux performance. (authors)

  2. Thermal response to heat fluxes of the W7-AS divertor surface submitted to surface modification under high temperature treatment

    Energy Technology Data Exchange (ETDEWEB)

    Hildebrandt, D., E-mail: dieter.hildebrandt@ipp.mpg.d [Euratom Association, Max-Planck-Institut fuer Plasmaphysik, Teilinstitut Greifswald, Wendelsteinstrasse 1, 17491 Greifswald (Germany); Duebner, A. [Euratom Association, Max-Planck-Institut fuer Plasmaphysik, Teilinstitut Greifswald, Wendelsteinstrasse 1, 17491 Greifswald (Germany); Greuner, H.; Wiltner, A. [Teilinstitut Garching, Boltzmannstr. 2, 85748 Garching (Germany)

    2009-06-15

    Some target tiles of the W7-AS divertor has been investigated with respect to their thermal behaviour at the surface during power loading with well-defined heat fluxes in the Gladis facility. The primary aim was to examine uncertainties in the determination of heat fluxes derived from IR-thermography during operation of W7-AS. It is found that the derived heat flux profiles are strongly influenced by the local distribution of plasma-deposited contamination analyzed by AES and SIMS. With the observed actual surface conditions characterized by redeposited contamination equivalent up to about 1 mum thickness, the heat fluxes were partially overestimated up to a factor of 4 during operation of W7-AS. This uncertainty is observed to be significantly reduced after heat treatment at temperatures beyond 700 deg. C attained at power flux densities of 10.5 MW/m{sup 2} and durations longer than 5 s.

  3. Thermal response to heat fluxes of the W7-AS divertor surface submitted to surface modification under high temperature treatment

    International Nuclear Information System (INIS)

    Hildebrandt, D.; Duebner, A.; Greuner, H.; Wiltner, A.

    2009-01-01

    Some target tiles of the W7-AS divertor has been investigated with respect to their thermal behaviour at the surface during power loading with well-defined heat fluxes in the Gladis facility. The primary aim was to examine uncertainties in the determination of heat fluxes derived from IR-thermography during operation of W7-AS. It is found that the derived heat flux profiles are strongly influenced by the local distribution of plasma-deposited contamination analyzed by AES and SIMS. With the observed actual surface conditions characterized by redeposited contamination equivalent up to about 1 μm thickness, the heat fluxes were partially overestimated up to a factor of 4 during operation of W7-AS. This uncertainty is observed to be significantly reduced after heat treatment at temperatures beyond 700 deg. C attained at power flux densities of 10.5 MW/m 2 and durations longer than 5 s.

  4. The Influence of a Sandy Substrate, Seagrass, or Highly Turbid Water on Albedo and Surface Heat Flux

    Science.gov (United States)

    Fogarty, M. C.; Fewings, M. R.; Paget, A. C.; Dierssen, H. M.

    2018-01-01

    Sea-surface albedo is a combination of surface-reflected and water-leaving irradiance, but water-leaving irradiance typically contributes less than 15% of the total albedo in open-ocean conditions. In coastal systems, however, the bottom substrate or suspended particulate matter can increase the amount of backscattered light, thereby increasing albedo and decreasing net shortwave surface heat flux. Here a sensitivity analysis using observations and models predicts the effect of light scattering on albedo and the net shortwave heat flux for three test cases: a bright sand bottom, a seagrass canopy, and turbid water. After scaling to the full solar shortwave spectrum, daytime average albedo for the test cases is up to 0.20 and exceeds the value of 0.05 predicted using a commonly applied parameterization. Daytime net shortwave heat flux into the water is significantly reduced, particularly for waters with bright sediments, dense horizontal seagrass canopies waters with suspended particulate matter concentration ≥ 50 g m-3. Observations of a more vertical seagrass canopy within 0.2 and 1 m of the surface indicate the increase in albedo compared to the common parameterization is negligible. Therefore, we suggest that the commonly applied albedo lookup table can be used in coastal heat flux estimates in water as shallow as 1 m unless the bottom substrate is highly reflective or the water is highly turbid. Our model results provide guidance to researchers who need to determine albedo in highly reflective or highly turbid conditions but have no direct observations.

  5. The role of land surface fluxes in Saudi-KAU AGCM: Temperature climatology over the Arabian Peninsula for the period 1981-2010

    Science.gov (United States)

    Ashfaqur Rahman, M.; Almazroui, Mansour; Nazrul Islam, M.; O'Brien, Enda; Yousef, Ahmed Elsayed

    2018-02-01

    A new version of the Community Land Model (CLM) was introduced to the Saudi King Abdulaziz University Atmospheric Global Climate Model (Saudi-KAU AGCM) for better land surface component representation, and so to enhance climate simulation. CLM replaced the original land surface model (LSM) in Saudi-KAU AGCM, with the aim of simulating more accurate land surface fluxes globally, but especially over the Arabian Peninsula. To evaluate the performance of Saudi-KAU AGCM, simulations were completed with CLM and LSM for the period 1981-2010. In comparison with LSM, CLM generates surface air temperature values that are closer to National Centre for Environmental Prediction (NCEP) observations. The global annual averages of land surface air temperature are 9.51, 9.52, and 9.57 °C for NCEP, CLM, and LSM respectively, although the same atmospheric radiative and surface forcing from Saudi-KAU AGCM are provided to both LSM and CLM at every time step. The better temperature simulations when using CLM can be attributed to the more comprehensive plant functional type and hierarchical tile approach to the land cover type in CLM, along with better parameterization of upward land surface fluxes compared to LSM. At global scale, CLM exhibits smaller annual and seasonal mean biases of temperature with respect to NCEP data. Moreover, at regional scale, CLM demonstrates reasonable seasonal and annual mean temperature over the Arabian Peninsula as compared to the Climatic Research Unit (CRU) data. Finally, CLM generated better matches to single point-wise observations of surface air temperature and surface fluxes for some case studies.

  6. Urban surface energy fluxes based on remotely-sensed data and micrometeorological measurements over the Kansai area, Japan

    Science.gov (United States)

    Sukeyasu, T.; Ueyama, M.; Ando, T.; Kosugi, Y.; Kominami, Y.

    2017-12-01

    The urban heat island is associated with land cover changes and increases in anthropogenic heat fluxes. Clear understanding of the surface energy budget at urban area is the most important for evaluating the urban heat island. In this study, we develop a model based on remotely-sensed data for the Kansai area in Japan and clarify temporal transitions and spatial distributions of the surface energy flux from 2000 to 2016. The model calculated the surface energy fluxes based on various satellite and GIS products. The model used land surface temperature, surface emissivity, air temperature, albedo, downward shortwave radiation and land cover/use type from the moderate resolution imaging spectroradiometer (MODIS) under cloud free skies from 2000 to 2016 over the Kansai area in Japan (34 to 35 ° N, 135 to 136 ° E). Net radiation was estimated by a radiation budget of upward/downward shortwave and longwave radiation. Sensible heat flux was estimated by a bulk aerodynamic method. Anthropogenic heat flux was estimated by the inventory data. Latent heat flux was examined with residues of the energy budget and parameterization of bulk transfer coefficients. We validated the model using observed fluxes from five eddy-covariance measurement sites: three urban sites and two forested sites. The estimated net radiation roughly agreed with the observations, but the sensible heat flux were underestimated. Based on the modeled spatial distributions of the fluxes, the daytime net radiation in the forested area was larger than those in the urban area, owing to higher albedo and land surface temperatures in the urban area than the forested area. The estimated anthropogenic heat flux was high in the summer and winter periods due to increases in energy-requirements.

  7. A method for sensible heat flux model parameterization based on radiometric surface temperature and environmental factors without involving the parameter KB-1

    Science.gov (United States)

    Zhuang, Qifeng; Wu, Bingfang; Yan, Nana; Zhu, Weiwei; Xing, Qiang

    2016-05-01

    Sensible heat flux is a key component of land-atmosphere interaction. In most parameterizations it is calculated with surface-air temperature differences and total aerodynamic resistance to heat transfer (Rae) that is related to the KB-1 parameter. Suitable values are hard to obtain since KB-1 is related both to canopy characteristics and environmental conditions. In this paper, a parameterize method for sensible heat flux over vegetated surfaces (maize field and grass land in the Heihe river basin of northwest China) was proposed based on the radiometric surface temperature, surface resistance (Rs) and vapor pressures (saturated and actual) at the surface and the atmosphere above the canopy. A biophysics-based surface resistance model was revised to compute surface resistance with several environmental factors. The total aerodynamic resistance to heat transfer is directly calculated by combining the biophysics-based surface resistance and vapor pressures. One merit of this method is that the calculation of KB-1 can be avoided. The method provides a new way to estimate sensible heat flux over vegetated surfaces and its performance compares well to the LAS measured sensible heat and other empirical or semi-empirical KB-1 based estimations.

  8. Surface latent heat flux as an earthquake precursor

    Directory of Open Access Journals (Sweden)

    S. Dey

    2003-01-01

    Full Text Available The analysis of surface latent heat flux (SLHF from the epicentral regions of five recent earthquakes that occurred in close proximity to the oceans has been found to show anomalous behavior. The maximum increase of SLHF is found 2–7 days prior to the main earthquake event. This increase is likely due to an ocean-land-atmosphere interaction. The increase of SLHF prior to the main earthquake event is attributed to the increase in infrared thermal (IR temperature in the epicentral and surrounding region. The anomalous increase in SLHF shows great potential in providing early warning of a disastrous earthquake, provided that there is a better understanding of the background noise due to the tides and monsoon in surface latent heat flux. Efforts have been made to understand the level of background noise in the epicentral regions of the five earthquakes considered in the present paper. A comparison of SLHF from the epicentral regions over the coastal earthquakes and the earthquakes that occurred far away from the coast has been made and it has been found that the anomalous behavior of SLHF prior to the main earthquake event is only associated with the coastal earthquakes.

  9. The role of surface energy fluxes in pan-Arctic snow cover changes

    International Nuclear Information System (INIS)

    Shi Xiaogang; Lettenmaier, Dennis P; Groisman, Pavel Ya; Dery, Stephen J

    2011-01-01

    We analyze snow cover extent (SCE) trends in the National Oceanic and Atmospheric Administration's (NOAA) northern hemisphere weekly satellite SCE data using the Mann-Kendall trend test and find that North American and Eurasian snow cover in the pan-Arctic have declined significantly in spring and summer over the period of satellite record beginning in the early 1970s. These trends are reproduced, both in trend direction and statistical significance, in reconstructions using the variable infiltration capacity (VIC) hydrological model. We find that spring and summer surface radiative and turbulent fluxes generated in VIC have strong correlations with satellite observations of SCE. We identify the role of surface energy fluxes and determine which is most responsible for the observed spring and summer SCE recession. We find that positive trends in surface net radiation (SNR) accompany most of the SCE trends, whereas modeled latent heat (LH) and sensible heat (SH) trends associated with warming on SCE mostly cancel each other, except for North America in spring, and to a lesser extent for Eurasia in summer. In spring over North America and summer in Eurasia, the SH contribution to the observed snow cover trends is substantial. The results indicate that ΔSNR is the primary energy source and ΔSH plays a secondary role in changes of SCE. Compared with ΔSNR and ΔSH, ΔLH has a minor influence on pan-Arctic snow cover changes.

  10. Effects of the divertor tile geometries and magnetic field angles on the heat fluxes to the surface

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Wanpeng; Sang, Chaofeng; Sun, Zhenyue; Wang, Dezhen, E-mail: wangdez@dlut.edu.cn

    2017-03-15

    Highlights: • Simulation of the plasma behaviors in the divertor gap region is done by using a 2d3 v Particle-In-Cell code. • Heat fluxes on the wall surface in different gap geometries are studied. • The effect of the magnetic field angle on the heat flux is investigated. - Abstract: A two dimension-in-space and three dimension-in-velocity (2d3v) Particle-In-Cell (PIC) code is applied to investigate the plasma behaviors at the divertor gaps region in this work. Electron and D{sup +} ion fluxes to the tile surface in the poloidal and toroidal gaps for different shaped edges are compared to demonstrate the optimized tile geometry. For poloidal gap, shaped edge in the shadowing side makes more ions penetrate into the gap, while shaped edge in the wetted side can mitigate the peak flux value. For toroidal gap, most ions entering the gap impinge on the side tile mainly due to the E × B drift, and shaped wetted edges also can mitigate the peak heat fluxes. In addition, effects of magnetic field inclination angle from toroidal direction on the plasma behaviors are simulated for poloidal and toroidal gaps, respectively. It is found that the magnetic field angles don’t influence the plasma behaviors in poloidal gap; while significant changes have been observed in the toroidal gap.

  11. Validation of parameterizations for the surface turbulent fluxes over sea ice with CHINARE 2010 and SHEBA data

    Directory of Open Access Journals (Sweden)

    Yixiong Lu

    2013-09-01

    Full Text Available This study examines the modelled surface turbulent fluxes over sea ice from the bulk algorithms of the Beijing Climate Centre Climate System Model (BCC_CSM, the European Centre for Medium-Range Weather Forecasts (ECMWF model and the Community Earth System Model (CESM with data from the fourth Chinese National Arctic Research Expedition (CHINARE 2010 and the Surface Heat Budget of the Arctic Ocean (SHEBA experiment. Of all the model algorithms, wind stresses are replicated well and have small annual biases (−0.6% in BCC_CSM, 0.2% in CESM and 17% in ECMWF with observations, annual sensible heat fluxes are consistently underestimated by 83–141%, and annual latent heat fluxes are generally overestimated by 49–73%. Five sets of stability functions for stable stratification are evaluated based on theoretical and observational analyses, and the superior stability functions are employed in a new bulk algorithm proposal, which also features varying roughness lengths. Compared to BCC_CSM, the new algorithm can estimate the friction velocity with significantly reduced bias, 84% smaller in winter and 56% smaller in summer, respectively. For the sensible heat flux, the bias of the new algorithm is 30% smaller in winter and 19% smaller in summer than that of BCC_CSM. Finally, the bias of modelled latent heat fluxes is 27% smaller in summer.

  12. A Particle-In-Cell approach to particle flux shaping with a surface mask

    Directory of Open Access Journals (Sweden)

    G. Kawamura

    2017-08-01

    Full Text Available The Particle-In-Cell simulation code PICS has been developed to study plasma in front of a surface with two types of masks, step-type and roof-type. Parameter scans with regard to magnetic field angle, electron density, and mask height were carried out to understand their influence on ion particle flux distribution on a surface. A roof-type mask with a small mask height yields short decay length in the flux distribution which is consistent with that estimated experimentally. A roof-type mask with a large height yields very long decay length and the flux value does not depend on a mask height or an electron density, but rather on a mask length and a biasing voltage of the surface. Mask height also changes the flux distribution apart from the mask because of the shading effect of the mask. Electron density changes the distribution near the mask edge according to the Debye length. Dependence of distribution on parameters are complicated especially for a roof-type mask, and simulation study with various parameters are useful to understand the physical reasons of dependence and also is useful as a tool for experiment studies.

  13. Monthly Sea Surface Salinity and Freshwater Flux Monitoring

    Science.gov (United States)

    Ren, L.; Xie, P.; Wu, S.

    2017-12-01

    Taking advantages of the complementary nature of the Sea Surface Salinity (SSS) measurements from the in-situ (CTDs, shipboard, Argo floats, etc.) and satellite retrievals from Soil Moisture Ocean Salinity (SMOS) satellite of the European Space Agency (ESA), the Aquarius of a joint venture between US and Argentina, and the Soil Moisture Active Passive (SMAP) of national Aeronautics and Space Administration (NASA), a technique is developed at NOAA/NCEP/CPC to construct an analysis of monthly SSS, called the NOAA Blended Analysis of Sea-Surface Salinity (BASS). The algorithm is a two-steps approach, i.e. to remove the bias in the satellite data through Probability Density Function (PDF) matching against co-located in situ measurements; and then to combine the bias-corrected satellite data with the in situ measurements through the Optimal Interpolation (OI) method. The BASS SSS product is on a 1° by 1° grid over the global ocean for a 7-year period from 2010. Combined with the NOAA/NCEP/CPC CMORPH satellite precipitation (P) estimates and the Climate Forecast System Reanalysis (CFSR) evaporation (E) fields, a suite of monthly package of the SSS and oceanic freshwater flux (E and P) was developed to monitor the global oceanic water cycle and SSS on a monthly basis. The SSS in BASS product is a suite of long-term SSS and fresh water flux data sets with temporal homogeneity and inter-component consistency better suited for the examination of the long-term changes and monitoring. It presents complete spatial coverage and improved resolution and accuracy, which facilitates the diagnostic analysis of the relationship and co-variability among SSS, freshwater flux, mixed layer processes, oceanic circulation, and assimilation of SSS into global models. At the AGU meeting, we will provide more details on the CPC salinity and fresh water flux data package and its applications in the monitoring and analysis of SSS variations in association with the ENSO and other major climate

  14. Drift wave turbulence studies on closed and open flux surfaces: effect limiter/divertor plates location

    International Nuclear Information System (INIS)

    Ribeiro, T.; Scott, B.

    2007-01-01

    The field line connection of a tokamak sheared magnetic field has an important impact on turbulence, by ensuring a finite parallel dynamical response for every degree of freedom available in the system. This constitutes the main property which distinguishes closed from open flux surfaces in such a device. In the latter case, the poloidal periodicity of the magnetic field is replaced by a Debye sheath arising where the field lines strike the limiter/divertor plates. This is enough to break the field line connection constraint and allow the existence of convective cell modes, leading to a change in the character of the turbulence from drift wave- (closed flux surfaces) to interchange-type (open flux surfaces), and hence increasing the turbulent transport observed. Here we study the effect of changing the poloidal position of the limiter/divertor plates, using the three-dimensional electromagnetic gyrofluid turbulence code GEM, which has time dependently self consistent field aligned flux tube coordinates. For the closed flux surfaces, the globally consistent periodic boundary conditions are invoked, and for open flux surfaces a standard Debye sheath is used at the striking points. In particular, the use of two limiter positions simultaneously, top and bottom, is in order, such to allow a separation between the inboard and outboard sides of the tokamak. This highlights the differences between those two regions of the tokamak, where the curvature is either favourable (former) or unfavourable (latter), and further makes room for future experimental qualitative comparisons, for instance, on double null configurations of the tokamak ASDEX Upgrade. (author)

  15. LBA-HMET PC-06 ECMWF Modeled Precipitation and Surface Flux, Rondonia, Brazil: 1999

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: This data set provides the mean diurnal cycle of precipitation, near-surface thermodynamics, and surface fluxes generated from short-term forecasts from...

  16. Surface oxygen vacancy and oxygen permeation flux limits of perovskite ion transport membranes

    KAUST Repository

    Hunt, Anton

    2015-09-01

    © 2015 Elsevier B.V. The mechanisms and quantitative models for how oxygen is separated from air using ion transport membranes (ITMs) are not well understood, largely due to the experimental complexity for determining surface exchange reactions at extreme temperatures (>800°C). This is especially true when fuels are present at the permeate surface. For both inert and reactive (fuels) operations, solid-state oxygen surface vacancies (δ) are ultimately responsible for driving the oxygen flux, JO2. In the inert case, the value of δ at either surface is a function of the local PO2 and temperature, whilst the magnitude of δ dictates both the JO2 and the inherent stability of the material. In this study values of δ are presented based on experimental measurements under inert (CO2) sweep: using a permeation flux model and local PO2 measurements, collected by means of a local gas-sampling probe in our large-scale reactor, we can determine δ directly. The ITM assessed was La0.9Ca0.1FeO3-δ (LCF); the relative resistances to JO2 were quantified using the pre-defined permeation flux model and local PO2 values. Across a temperature range from 825°C to 1056°C, δ was found to vary from 0.007 to 0.029 (<1%), safely within material stability limits, whilst the permeate surface exchange resistance dominates. An inert JO2 limit was identified owing to a maximum sweep surface δ, δmaxinert. The physical presence of δmaxinert is attributed to a rate limiting step shift from desorption to associative electron transfer steps on the sweep surface as PO2 is reduced. Permeate surface exchange limitations under non-reactive conditions suggest that reactive (fuel) operation is necessary to accelerate surface chemistry for future work, to reduce flux resistance and push δpast δmaxinert in a stable manner.

  17. Two-wavelength Method Estimates Heat fluxes over Heterogeneous Surface in North-China

    Science.gov (United States)

    Zhang, G.; Zheng, N.; Zhang, J.

    2017-12-01

    Heat fluxes is a key process of hydrological and heat transfer of soil-plant-atmosphere continuum (SPAC), and now it is becoming an important topic in meteorology, hydrology, ecology and other related research areas. Because the temporal and spatial variation of fluxes at regional scale is very complicated, it is still difficult to measure fluxes at the kilometer scale over a heterogeneous surface. A technique called "two-wavelength method" which combines optical scintillometer with microwave scintillometer is able to measure both sensible and latent heat fluxes over large spatial scales at the same time. The main purpose of this study is to investigate the fluxes over non-uniform terrain in North-China. Estimation of heat fluxes was carried out with the optical-microwave scintillometer and an eddy covariance (EC) system over heterogeneous surface in Tai Hang Mountains, China. EC method was set as a benchmark in the study. Structure parameters obtained from scintillometer showed that the typical measurement values of Cn2 are around 10-13 m-2/3 for microwave scintillometer, and values of Cn2 were around 10-15 m-2/3 for optical scintillometer. The correlation of heat fluxes (H) derived from scintillometer and EC system showed as a ratio of 1.05,and with R2=0.75, while the correlation of latent heat fluxes (LE) showed as 1.29 with R2=0.67. It was also found that heat fluxes derived from the two system showed good agreement (R2=0.9 for LE, R2=0.97 for H) when the Bowen ratio (β) was 1.03, while discrepancies showed significantly when β=0.75, and RMSD in H was 139.22 W/m2, 230.85 W/m2 in LE respectively.Experiment results in our research shows that, the two-wavelength method gives a larger heat fluxes over the study area, and a deeper study should be conduct. We expect that our investigate and analysis can be promoted the application of scintillometry method in regional evapotranspiration measurements and relevant disciplines.

  18. The surface energy, water, carbon flux and their intercorrelated seasonality in a global climate-vegetation coupled model

    International Nuclear Information System (INIS)

    Li Dan.; Jinjun Ji

    2007-01-01

    The sensible and latent heat fluxes, representatives of the physical exchange processes of energy and water between land and air, are the two crucial variables controlling the surface energy partitioning related to temperature and humidity. The net primary production (NPP), the major carbon flux exchange between vegetation and atmosphere, is of great importance for the terrestrial ecosystem carbon cycle. The fluxes are simulated by a two-way coupled model, Atmosphere-Vegetation Interaction Model-Global Ocean-Atmosphere-Land System Model (AVIM-GOALS) in which the surface physical and physiological processes are coupled with general circulation model (GCM), and the global spatial and temporal variation of the fluxes is studied. The simulated terrestrial surface physical fluxes are consistent with the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis (ERA40) in the global distribution, but the magnitudes are generally 20-40 W/m 2 underestimated. The annual NPP agrees well with the International Geosphere Biosphere Programme (IGBP) NPP data except for the lower value in northern high latitudes. The surface physical fluxes, leaf area index (LAI) and NPP of the global mid-latitudes, especially between 30 deg N-50 deg N, show great variation in annual oscillation amplitudes. And all physical and biological fields in northern mid-latitudes have the largest seasonality with a high statistical significance of 99.9%. The seasonality of surface physical fluxes, LAI and NPP are highly correlated with each other. The meridional three-peak pattern of seasonal change emerges in northern mid-latitudes, which indicates the interaction of topographical gradient variation of surface fluxes and vegetation phenology on these three latitudinal belts

  19. Verification of land-atmosphere coupling in forecast models, reanalyses and land surface models using flux site observations.

    Science.gov (United States)

    Dirmeyer, Paul A; Chen, Liang; Wu, Jiexia; Shin, Chul-Su; Huang, Bohua; Cash, Benjamin A; Bosilovich, Michael G; Mahanama, Sarith; Koster, Randal D; Santanello, Joseph A; Ek, Michael B; Balsamo, Gianpaolo; Dutra, Emanuel; Lawrence, D M

    2018-02-01

    We confront four model systems in three configurations (LSM, LSM+GCM, and reanalysis) with global flux tower observations to validate states, surface fluxes, and coupling indices between land and atmosphere. Models clearly under-represent the feedback of surface fluxes on boundary layer properties (the atmospheric leg of land-atmosphere coupling), and may over-represent the connection between soil moisture and surface fluxes (the terrestrial leg). Models generally under-represent spatial and temporal variability relative to observations, which is at least partially an artifact of the differences in spatial scale between model grid boxes and flux tower footprints. All models bias high in near-surface humidity and downward shortwave radiation, struggle to represent precipitation accurately, and show serious problems in reproducing surface albedos. These errors create challenges for models to partition surface energy properly and errors are traceable through the surface energy and water cycles. The spatial distribution of the amplitude and phase of annual cycles (first harmonic) are generally well reproduced, but the biases in means tend to reflect in these amplitudes. Interannual variability is also a challenge for models to reproduce. Our analysis illuminates targets for coupled land-atmosphere model development, as well as the value of long-term globally-distributed observational monitoring.

  20. Detecting buried radium contamination using soil-gas and surface-flux radon meaurements

    International Nuclear Information System (INIS)

    Karp, K.E.

    1988-06-01

    The Technical Measurements Center (TMC) has investigated the effectiveness of using radon soil-gas under surface-flux measurments to locate radium contamination that is buried sufficiently deep to be undetectable by surface gamma methods. At the first test site studied, an indication of a buried source was revealed by mapping anomalous surface-flux and soil-gas concentrations in the near surface overburden. The mapped radon anomalies were found to correspond in rough outline to the shape of the areal extent of the deposit as determined by borehole gamma-ray logs. The 5.9pCi/g radium deposit, buried 2 feet below the surface, went undetected by conventional surface gamma measurements. Similar results were obtained at the second test site where radon and conventional surface gamma measurements were taken in an area having radium concentrations ranging from 13.3 to 341.0 pCi/g at a depth of 4 feet below the surface. The radon methods were found to have a detection limit for buried radium lower than that of the surface gamma methods, as evidenced by the discovery of the 13.3 pCi/g deposit which went undetected by the surface gamma methods. 15 refs., 33 figs., 8 tabs

  1. Influence of particle flux density and temperature on surface modifications of tungsten and deuterium retention

    International Nuclear Information System (INIS)

    Buzi, Luxherta; Temmerman, Greg De; Unterberg, Bernhard; Reinhart, Michael; Litnovsky, Andrey; Philipps, Volker; Oost, Guido Van; Möller, Sören

    2014-01-01

    Systematic study of deuterium irradiation effects on tungsten was done under ITER – relevant high particle flux density, scanning a broad surface temperature range. Polycrystalline ITER – like grade tungsten samples were exposed in linear plasma devices to two different ranges of deuterium ion flux densities (high: 3.5–7 · 10 23 D + /m 2 s and low: 9 · 10 21 D + /m 2 s). Particle fluence and ion energy, respectively 10 26 D + /m 2 and ∼38 eV were kept constant in all cases. The experiments were performed at three different surface temperatures 530 K, 630 K and 870 K. Experimental results concerning the deuterium retention and surface modifications of low flux exposure confirmed previous investigations. At temperatures 530 K and 630 K, deuterium retention was higher at lower flux density due to the longer exposure time (steady state plasma operation) and a consequently deeper diffusion range. At 870 K, deuterium retention was found to be higher at high flux density according to the thermal desorption spectroscopy (TDS) measurements. While blisters were completely absent at low flux density, small blisters of about 40–50 nm were formed at high flux density exposure. At the given conditions, a relation between deuterium retention and blister formation has been found which has to be considered in addition to deuterium trapping in defects populated by diffusion

  2. Characterization of ion fluxes and heat fluxes for PMI relevant conditions on Proto-MPEX

    Science.gov (United States)

    Beers, Clyde; Shaw, Guinevere; Biewer, Theodore; Rapp, Juergen

    2016-10-01

    Plasma characterization, in particular, particle flux and electron and ion temperature distributions nearest to an exposed target, are critical to quantifying Plasma Surface Interaction (PSI). In the Proto-Material Plasma Exposure eXperiment (Proto-MPEX), the ion fluxes and heat fluxes are derived from double Langmuir Probes (DLP) and Thomson Scattering in front of the target assuming Bohm conditions at the sheath entrance. Power fluxes derived from ne and Te measurements are compared to heat fluxes measured with IR thermography. The comparison will allow conclusions on the sheath heat transmission coefficient to be made experimentally. Different experimental conditions (low and high density plasmas (0.5 - 6 x 1019 m-3) with different magnetic configuration are compared. This work was supported by the U.S. D.O.E. contract DE-AC05-00OR22725.

  3. Inverse modeling of hydrologic parameters using surface flux and runoff observations in the Community Land Model

    Science.gov (United States)

    Sun, Y.; Hou, Z.; Huang, M.; Tian, F.; Leung, L. Ruby

    2013-12-01

    This study demonstrates the possibility of inverting hydrologic parameters using surface flux and runoff observations in version 4 of the Community Land Model (CLM4). Previous studies showed that surface flux and runoff calculations are sensitive to major hydrologic parameters in CLM4 over different watersheds, and illustrated the necessity and possibility of parameter calibration. Both deterministic least-square fitting and stochastic Markov-chain Monte Carlo (MCMC)-Bayesian inversion approaches are evaluated by applying them to CLM4 at selected sites with different climate and soil conditions. The unknowns to be estimated include surface and subsurface runoff generation parameters and vadose zone soil water parameters. We find that using model parameters calibrated by the sampling-based stochastic inversion approaches provides significant improvements in the model simulations compared to using default CLM4 parameter values, and that as more information comes in, the predictive intervals (ranges of posterior distributions) of the calibrated parameters become narrower. In general, parameters that are identified to be significant through sensitivity analyses and statistical tests are better calibrated than those with weak or nonlinear impacts on flux or runoff observations. Temporal resolution of observations has larger impacts on the results of inverse modeling using heat flux data than runoff data. Soil and vegetation cover have important impacts on parameter sensitivities, leading to different patterns of posterior distributions of parameters at different sites. Overall, the MCMC-Bayesian inversion approach effectively and reliably improves the simulation of CLM under different climates and environmental conditions. Bayesian model averaging of the posterior estimates with different reference acceptance probabilities can smooth the posterior distribution and provide more reliable parameter estimates, but at the expense of wider uncertainty bounds.

  4. Soil heat flux and day time surface energy balance closure

    Indian Academy of Sciences (India)

    Soil heat flux; surface energy balance; Bowen's ratio; sensible and latent ... The energy storage term for the soil layer 0–0.05 m is calculated and the ground heat ... When a new method that accounts for both soil thermal conduction and soil ...

  5. Goddard Satellite-Based Surface Turbulent Fluxes Climatology, Yearly Grid V3

    Data.gov (United States)

    National Aeronautics and Space Administration — These data are the Goddard Satellite-based Surface Turbulent Fluxes Version-3 Dataset recently produced through a MEaSUREs funded project led by Dr. Chung-Lin Shie...

  6. Goddard Satellite-Based Surface Turbulent Fluxes Climatology, Seasonal Grid V3

    Data.gov (United States)

    National Aeronautics and Space Administration — These data are the Goddard Satellite-based Surface Turbulent Fluxes Version-3 Dataset recently produced through a MEaSUREs funded project led by Dr. Chung-Lin Shie...

  7. Comparative Assessment of Two Vegetation Fractional Cover Estimating Methods and Their Impacts on Modeling Urban Latent Heat Flux Using Landsat Imagery

    Directory of Open Access Journals (Sweden)

    Kai Liu

    2017-05-01

    Full Text Available Quantifying vegetation fractional cover (VFC and assessing its role in heat fluxes modeling using medium resolution remotely sensed data has received less attention than it deserves in heterogeneous urban regions. This study examined two approaches (Normalized Difference Vegetation Index (NDVI-derived and Multiple Endmember Spectral Mixture Analysis (MESMA-derived methods that are commonly used to map VFC based on Landsat imagery, in modeling surface heat fluxes in urban landscape. For this purpose, two different heat flux models, Two-source energy balance (TSEB model and Pixel Component Arranging and Comparing Algorithm (PCACA model, were adopted for model evaluation and analysis. A comparative analysis of the NDVI-derived and MESMA-derived VFCs showed that the latter achieved more accurate estimates in complex urban regions. When the two sources of VFCs were used as inputs to both TSEB and PCACA models, MESMA-derived urban VFC produced more accurate urban heat fluxes (Bowen ratio and latent heat flux relative to NDVI-derived urban VFC. Moreover, our study demonstrated that Landsat imagery-retrieved VFC exhibited greater uncertainty in obtaining urban heat fluxes for the TSEB model than for the PCACA model.

  8. Soil surface Hg emission flux in coalfield in Wuda, Inner Mongolia, China.

    Science.gov (United States)

    Li, Chunhui; Liang, Handong; Liang, Ming; Chen, Yang; Zhou, Yi

    2018-03-30

    Hg emission flux from various land covers, such as forests, wetlands, and urban areas, have been investigated. China has the largest area of coalfield in the world, but data of Hg flux of coalfields, especially, those with coal fires, are seriously limited. In this study, Hg fluxes of a coalfield were measured using the dynamic flux chamber (DFC) method, coupled with a Lumex multifunctional Hg analyzer RA-915+ (Lumex Ltd., Russia). The results show that the Hg flux in Wuda coalfield ranged from 4 to 318 ng m -2  h -1 , and the average value for different areas varied, e.g., coal-fire area 99 and 177 ng m -2  h -1 ; no coal-fire area 19 and 32 ng m -2  h -1 ; and backfilling area 53 ng m -2  h -1 . Hg continued to be emitted from an underground coal seam, even if there were no phenomena, such as vents, cracks, and smog, of coal fire on the soil surface. This phenomenon occurred in all area types, i.e., coal-fire area, no coal-fire area, and backfilling area, which is universal in Wuda coalfield. Considering that many coalfields in northern China are similar to Wuda coalfield, they may be large sources of atmospheric Hg. The correlations of Hg emission flux with influence factors, such as sunlight intensity, soil surface temperature, and atmospheric Hg content, were also investigated for Wuda coalfield. Graphical abstract ᅟ.

  9. Influence of particle flux density and temperature on surface modifications of tungsten and deuterium retention

    Energy Technology Data Exchange (ETDEWEB)

    Buzi, Luxherta, E-mail: l.buzi@fz-juelich.de [Ghent University, Department of Applied Physics, Sint-Pietersnieuwstraat 41, B-9000 Ghent (Belgium); FOM Institute DIFFER-Dutch Institute for Fundamental Energy Research, Edisonbaan 14, 3439 MN, PO Box 1207, 3430 BE Nieuwegein (Netherlands); Institut für Energie und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich GmbH, Leo-Brandt-Straße, 52425 Jülich (Germany); Université de Lorraine, Institut Jean Lamour, CNRS UMR 7198, Bvd. des Aiguillettes, F-54506 Vandoeuvre (France); Temmerman, Greg De [FOM Institute DIFFER-Dutch Institute for Fundamental Energy Research, Edisonbaan 14, 3439 MN, PO Box 1207, 3430 BE Nieuwegein (Netherlands); Unterberg, Bernhard; Reinhart, Michael; Litnovsky, Andrey; Philipps, Volker [Institut für Energie und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich GmbH, Leo-Brandt-Straße, 52425 Jülich (Germany); Oost, Guido Van [Ghent University, Department of Applied Physics, Sint-Pietersnieuwstraat 41, B-9000 Ghent (Belgium); Möller, Sören [Institut für Energie und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich GmbH, Leo-Brandt-Straße, 52425 Jülich (Germany)

    2014-12-15

    Systematic study of deuterium irradiation effects on tungsten was done under ITER – relevant high particle flux density, scanning a broad surface temperature range. Polycrystalline ITER – like grade tungsten samples were exposed in linear plasma devices to two different ranges of deuterium ion flux densities (high: 3.5–7 · 10{sup 23} D{sup +}/m{sup 2} s and low: 9 · 10{sup 21} D{sup +}/m{sup 2} s). Particle fluence and ion energy, respectively 10{sup 26} D{sup +}/m{sup 2} and ∼38 eV were kept constant in all cases. The experiments were performed at three different surface temperatures 530 K, 630 K and 870 K. Experimental results concerning the deuterium retention and surface modifications of low flux exposure confirmed previous investigations. At temperatures 530 K and 630 K, deuterium retention was higher at lower flux density due to the longer exposure time (steady state plasma operation) and a consequently deeper diffusion range. At 870 K, deuterium retention was found to be higher at high flux density according to the thermal desorption spectroscopy (TDS) measurements. While blisters were completely absent at low flux density, small blisters of about 40–50 nm were formed at high flux density exposure. At the given conditions, a relation between deuterium retention and blister formation has been found which has to be considered in addition to deuterium trapping in defects populated by diffusion.

  10. Effect of micrometric hot spots on surface temperature measurement and flux calculation in the middle and long infrared

    International Nuclear Information System (INIS)

    Delchambre, E; Counsell, G; Kirk, A

    2009-01-01

    The non-uniformity of the target temperature due to micrometric hot spots (Hermann et al 2004 Phys. Scr. T 111 98) is an explanation for the experimental fact that near-infrared measurements yield higher temperature values than mid-infrared measurements (Hildebrandt et al 2003 InfraMation 2003 Proc. (Las Vegas, USA, October 2003), Delchambre et al 2005 J. Nucl. Mater. 337-339 1069). The issue of micrometric hot spot disturbance in the surface temperature (T surf ) measurement and heat load calculation is addressed in this paper. The theoretical investigation at 3, 5 and 12 μm and experiments in the range 3.5-5 μm indicate that the surface state can play an important role in the non-uniform heating surface and consequently in the overestimation of the bulk temperature. The contribution of the hot spots to temperature measurements and flux calculations has been simulated at different wavelengths. Calculations show that (1) the overestimation of the bulk temperature decreases with the wavelength and (2) the overestimation depends on the temperature difference, ΔT, between the bulk and the micrometric hot spots. In addition, experiments have been carried out in order to compare the flux calculations at different wavelengths on different graphite (polished, dusty). The results obtained are very sensitive to the surface state pointing out the difficulties in improving the heat flux calculation model, since the surface state can change during the plasma discharges. This paper shows that the problem of non-homogenous surface temperature can be significantly diminished on working at longer wavelengths.

  11. Towards closure of regional heat budgets in the North Atlantic using Argo floats and surface flux datasets

    Directory of Open Access Journals (Sweden)

    N. C. Wells

    2009-04-01

    Full Text Available The upper ocean heat budget (0–300 m of the North Atlantic from 20°–60° N is investigated using data from Argo profiling floats for 1999–2005 and the NCEP/NCAR and NOC surface flux datasets. Estimates of the different terms in the budget (heat storage, advection, diffusion and surface exchange are obtained using the methodology developed by Hadfield et al. (2007a, b. The method includes optimal interpolation of the individual profiles to produce gridded fields with error estimates at a 10°×10° grid box resolution. Closure of the heat budget is obtained within the error estimates for some regions – particularly the eastern subtropical Atlantic – but not for those boxes that include the Gulf Stream. Over the whole range considered, closure is obtained for 13 (9 out of 20 boxes with the NOC (NCEP/NCAR surface fluxes. The seasonal heat budget at 20–30° N, 35–25° W is considered in detail. Here, the NCEP based budget has an annual mean residual of −55±35 Wm−2 compared with a NOC based value of −4±35 Wm−2. For this box, the net heat divergence of 36 Wm−2 (Ekman=−4 Wm−2, geostrophic=11 Wm−2, diffusion=29 Wm−2 offsets the net heating of 32 Wm−2 from the NOC surface heat fluxes. The results in this box are consistent with an earlier evaluation of the fluxes using measurements from research buoys in the subduction array which revealed biases in NCEP but good agreement of the buoy values with the NOC fields.

  12. Comparing convective heat fluxes derived from thermodynamics to a radiative-convective model and GCMs

    Science.gov (United States)

    Dhara, Chirag; Renner, Maik; Kleidon, Axel

    2015-04-01

    The convective transport of heat and moisture plays a key role in the climate system, but the transport is typically parameterized in models. Here, we aim at the simplest possible physical representation and treat convective heat fluxes as the result of a heat engine. We combine the well-known Carnot limit of this heat engine with the energy balances of the surface-atmosphere system that describe how the temperature difference is affected by convective heat transport, yielding a maximum power limit of convection. This results in a simple analytic expression for convective strength that depends primarily on surface solar absorption. We compare this expression with an idealized grey atmosphere radiative-convective (RC) model as well as Global Circulation Model (GCM) simulations at the grid scale. We find that our simple expression as well as the RC model can explain much of the geographic variation of the GCM output, resulting in strong linear correlations among the three approaches. The RC model, however, shows a lower bias than our simple expression. We identify the use of the prescribed convective adjustment in RC-like models as the reason for the lower bias. The strength of our model lies in its ability to capture the geographic variation of convective strength with a parameter-free expression. On the other hand, the comparison with the RC model indicates a method for improving the formulation of radiative transfer in our simple approach. We also find that the latent heat fluxes compare very well among the approaches, as well as their sensitivity to surface warming. What our comparison suggests is that the strength of convection and their sensitivity in the climatic mean can be estimated relatively robustly by rather simple approaches.

  13. The SURFEXv7.2 land and ocean surface platform for coupled or offline simulation of earth surface variables and fluxes

    Directory of Open Access Journals (Sweden)

    V. Masson

    2013-07-01

    Full Text Available SURFEX is a new externalized land and ocean surface platform that describes the surface fluxes and the evolution of four types of surfaces: nature, town, inland water and ocean. It is mostly based on pre-existing, well-validated scientific models that are continuously improved. The motivation for the building of SURFEX is to use strictly identical scientific models in a high range of applications in order to mutualise the research and development efforts. SURFEX can be run in offline mode (0-D or 2-D runs or in coupled mode (from mesoscale models to numerical weather prediction and climate models. An assimilation mode is included for numerical weather prediction and monitoring. In addition to momentum, heat and water fluxes, SURFEX is able to simulate fluxes of carbon dioxide, chemical species, continental aerosols, sea salt and snow particles. The main principles of the organisation of the surface are described first. Then, a survey is made of the scientific module (including the coupling strategy. Finally, the main applications of the code are summarised. The validation work undertaken shows that replacing the pre-existing surface models by SURFEX in these applications is usually associated with improved skill, as the numerous scientific developments contained in this community code are used to good advantage.

  14. The SURFEXv7.2 land and ocean surface platform for coupled or offline simulation of earth surface variables and fluxes

    Science.gov (United States)

    Masson, V.; Le Moigne, P.; Martin, E.; Faroux, S.; Alias, A.; Alkama, R.; Belamari, S.; Barbu, A.; Boone, A.; Bouyssel, F.; Brousseau, P.; Brun, E.; Calvet, J.-C.; Carrer, D.; Decharme, B.; Delire, C.; Donier, S.; Essaouini, K.; Gibelin, A.-L.; Giordani, H.; Habets, F.; Jidane, M.; Kerdraon, G.; Kourzeneva, E.; Lafaysse, M.; Lafont, S.; Lebeaupin Brossier, C.; Lemonsu, A.; Mahfouf, J.-F.; Marguinaud, P.; Mokhtari, M.; Morin, S.; Pigeon, G.; Salgado, R.; Seity, Y.; Taillefer, F.; Tanguy, G.; Tulet, P.; Vincendon, B.; Vionnet, V.; Voldoire, A.

    2013-07-01

    SURFEX is a new externalized land and ocean surface platform that describes the surface fluxes and the evolution of four types of surfaces: nature, town, inland water and ocean. It is mostly based on pre-existing, well-validated scientific models that are continuously improved. The motivation for the building of SURFEX is to use strictly identical scientific models in a high range of applications in order to mutualise the research and development efforts. SURFEX can be run in offline mode (0-D or 2-D runs) or in coupled mode (from mesoscale models to numerical weather prediction and climate models). An assimilation mode is included for numerical weather prediction and monitoring. In addition to momentum, heat and water fluxes, SURFEX is able to simulate fluxes of carbon dioxide, chemical species, continental aerosols, sea salt and snow particles. The main principles of the organisation of the surface are described first. Then, a survey is made of the scientific module (including the coupling strategy). Finally, the main applications of the code are summarised. The validation work undertaken shows that replacing the pre-existing surface models by SURFEX in these applications is usually associated with improved skill, as the numerous scientific developments contained in this community code are used to good advantage.

  15. Comparing inversion techniques for constraining CO2 fluxes in the Brazilian Amazon Basin with aircraft observations

    Science.gov (United States)

    Chow, V. Y.; Gerbig, C.; Longo, M.; Koch, F.; Nehrkorn, T.; Eluszkiewicz, J.; Ceballos, J. C.; Longo, K.; Wofsy, S. C.

    2012-12-01

    The Balanço Atmosférico Regional de Carbono na Amazônia (BARCA) aircraft program spanned the dry to wet and wet to dry transition seasons in November 2008 & May 2009 respectively. It resulted in ~150 vertical profiles covering the Brazilian Amazon Basin (BAB). With the data we attempt to estimate a carbon budget for the BAB, to determine if regional aircraft experiments can provide strong constraints for a budget, and to compare inversion frameworks when optimizing flux estimates. We use a LPDM to integrate satellite-, aircraft-, & surface-data with mesoscale meteorological fields to link bottom-up and top-down models to provide constraints and error bounds for regional fluxes. The Stochastic Time-Inverted Lagrangian Transport (STILT) model driven by meteorological fields from BRAMS, ECMWF, and WRF are coupled to a biosphere model, the Vegetation Photosynthesis Respiration Model (VPRM), to determine regional CO2 fluxes for the BAB. The VPRM is a prognostic biosphere model driven by MODIS 8-day EVI and LSWI indices along with shortwave radiation and temperature from tower measurements and mesoscale meteorological data. VPRM parameters are tuned using eddy flux tower data from the Large-Scale Biosphere Atmosphere experiment. VPRM computes hourly CO2 fluxes by calculating Gross Ecosystem Exchange (GEE) and Respiration (R) for 8 different vegetation types. The VPRM fluxes are scaled up to the BAB by using time-averaged drivers (shortwave radiation & temperature) from high-temporal resolution runs of BRAMS, ECMWF, and WRF and vegetation maps from SYNMAP and IGBP2007. Shortwave radiation from each mesoscale model is validated using surface data and output from GL 1.2, a global radiation model based on GOES 8 visible imagery. The vegetation maps are updated to 2008 and 2009 using landuse scenarios modeled by Sim Amazonia 2 and Sim Brazil. A priori fluxes modeled by STILT-VPRM are optimized using data from BARCA, eddy covariance sites, and flask measurements. The

  16. Flux quantization and quantum mechanics on Riemann surfaces in an external magnetic field

    International Nuclear Information System (INIS)

    Bolte, J.; Steiner, F.

    1990-10-01

    We investigate the possibility to apply an external constant magnetic field to a quantum mechanical system consisting of a particle moving on a compact or non-compact two-dimensional manifold of constant negative Gaussian curvature and of finite volume. For the motion on compact Riemann surfaces we find that a consistent formulation is only possible if the magnetic flux is quantized, as it is proportional to the (integrated) first Chern class of a certain complex line bundle over the manifold. In the case of non-compact surfaces of finite volume we obtain the striking result that the magnetic flux has to vanish identically due to the theorem that any holomorphic line bundle over a non-compact Riemann surface is holomorphically trivial. (orig.)

  17. New Constraints on Terrestrial Surface-Atmosphere Fluxes of Gaseous Elemental Mercury Using a Global Database.

    Science.gov (United States)

    Agnan, Yannick; Le Dantec, Théo; Moore, Christopher W; Edwards, Grant C; Obrist, Daniel

    2016-01-19

    Despite 30 years of study, gaseous elemental mercury (Hg(0)) exchange magnitude and controls between terrestrial surfaces and the atmosphere still remain uncertain. We compiled data from 132 studies, including 1290 reported fluxes from more than 200,000 individual measurements, into a database to statistically examine flux magnitudes and controls. We found that fluxes were unevenly distributed, both spatially and temporally, with strong biases toward Hg-enriched sites, daytime and summertime measurements. Fluxes at Hg-enriched sites were positively correlated with substrate concentrations, but this was absent at background sites. Median fluxes over litter- and snow-covered soils were lower than over bare soils, and chamber measurements showed higher emission compared to micrometeorological measurements. Due to low spatial extent, estimated emissions from Hg-enriched areas (217 Mg·a(-1)) were lower than previous estimates. Globally, areas with enhanced atmospheric Hg(0) levels (particularly East Asia) showed an emerging importance of Hg(0) emissions accounting for half of the total global emissions estimated at 607 Mg·a(-1), although with a large uncertainty range (-513 to 1353 Mg·a(-1) [range of 37.5th and 62.5th percentiles]). The largest uncertainties in Hg(0) fluxes stem from forests (-513 to 1353 Mg·a(-1) [range of 37.5th and 62.5th percentiles]), largely driven by a shortage of whole-ecosystem fluxes and uncertain contributions of leaf-atmosphere exchanges, questioning to what degree ecosystems are net sinks or sources of atmospheric Hg(0).

  18. Flux canceling in three-dimensional radiative magnetohydrodynamic simulations

    Science.gov (United States)

    Thaler, Irina; Spruit, H. C.

    2017-05-01

    We aim to study the processes involved in the disappearance of magnetic flux between regions of opposite polarity on the solar surface using realistic three-dimensional (3D) magnetohydrodynamic (MHD) simulations. "Retraction" below the surface driven by magnetic forces is found to be a very effective mechanism of flux canceling of opposite polarities. The speed at which flux disappears increases strongly with initial mean flux density. In agreement with existing inferences from observations we suggest that this is a key process of flux disappearance within active complexes. Intrinsic kG strength concentrations connect the surface to deeper layers by magnetic forces, and therefore the influence of deeper layers on the flux canceling process is studied. We do this by comparing simulations extending to different depths. For average flux densities of 50 G, and on length scales on the order of 3 Mm in the horizontal and 10 Mm in depth, deeper layers appear to have only a mild influence on the effective rate of diffusion.

  19. Quantification of surface energy fluxes from a small water body using scintillometry and eddy covariance

    DEFF Research Database (Denmark)

    McGloin, Ryan; McGowan, Hamish; McJannet, David

    2014-01-01

    Accurate quantification of evaporation from small water storages is essential for water management and planning, particularly in water-scarce regions. In order to ascertain suitable methods for direct measurement of evaporation from small water bodies, this study presents a comparison of eddy......% greater than eddy covariance measurements. We suggest possible reasons for this difference and provide recommendations for further research for improving measurements of surface energy fluxes over small water bodies using eddy covariance and scintillometry. Key Points Source areas for Eddy covariance...... and scintillometry were on the water surface Reasonable agreement was shown between the sensible heat flux measurements Scintillometer estimates of latent heat flux were greater than eddy covariance...

  20. Impacts of Irrigation on the Heat Fluxes and Near-Surface Temperature in an Inland Irrigation Area of Northern China

    Directory of Open Access Journals (Sweden)

    Li Jiang

    2014-03-01

    Full Text Available Irrigated agriculture has the potential to alter regional to global climate significantly. We investigate how irrigation will affect regional climate in the future in an inland irrigation area of northern China, focusing on its effects on heat fluxes and near-surface temperature. Using the Weather Research and Forecasting (WRF model, we compare simulations among three land cover scenarios: the control scenario (CON, the irrigation scenario (IRR, and the irrigated cropland expansion scenario (ICE. Our results show that the surface energy budgets and temperature are sensitive to changes in the extent and spatial pattern of irrigated land. Conversion to irrigated agriculture at the contemporary scale leads to an increase in annual mean latent heat fluxes of 12.10 W m−2, a decrease in annual mean sensible heat fluxes of 8.85 W m−2, and a decrease in annual mean temperature of 1.3 °C across the study region. Further expansion of irrigated land increases annual mean latent heat fluxes by 18.08 W m−2, decreases annual mean sensible heat fluxes by 12.31 W m−2, and decreases annual mean temperature by 1.7 °C. Our simulated effects of irrigation show that changes in land use management such as irrigation can be an important component of climate change and need to be considered together with greenhouse forcing in climate change assessments.

  1. A DOUBLE-RING ALGORITHM FOR MODELING SOLAR ACTIVE REGIONS: UNIFYING KINEMATIC DYNAMO MODELS AND SURFACE FLUX-TRANSPORT SIMULATIONS

    International Nuclear Information System (INIS)

    Munoz-Jaramillo, Andres; Martens, Petrus C. H.; Nandy, Dibyendu; Yeates, Anthony R.

    2010-01-01

    The emergence of tilted bipolar active regions (ARs) and the dispersal of their flux, mediated via processes such as diffusion, differential rotation, and meridional circulation, is believed to be responsible for the reversal of the Sun's polar field. This process (commonly known as the Babcock-Leighton mechanism) is usually modeled as a near-surface, spatially distributed α-effect in kinematic mean-field dynamo models. However, this formulation leads to a relationship between polar field strength and meridional flow speed which is opposite to that suggested by physical insight and predicted by surface flux-transport simulations. With this in mind, we present an improved double-ring algorithm for modeling the Babcock-Leighton mechanism based on AR eruption, within the framework of an axisymmetric dynamo model. Using surface flux-transport simulations, we first show that an axisymmetric formulation-which is usually invoked in kinematic dynamo models-can reasonably approximate the surface flux dynamics. Finally, we demonstrate that our treatment of the Babcock-Leighton mechanism through double-ring eruption leads to an inverse relationship between polar field strength and meridional flow speed as expected, reconciling the discrepancy between surface flux-transport simulations and kinematic dynamo models.

  2. The Path to High Q-Factors in Superconducting Accelerating Cavities: Flux Expulsion and Surface Resistance Optimization

    Energy Technology Data Exchange (ETDEWEB)

    Martinello, Martina [Illinois Inst. of Technology, Chicago, IL (United States)

    2016-12-01

    Accelerating cavities are devices resonating in the radio-frequency (RF) range used to accelerate charged particles in accelerators. Superconducting accelerating cavities are made out of niobium and operate at the liquid helium temperature. Even if superconducting, these resonating structures have some RF driven surface resistance that causes power dissipation. In order to decrease as much as possible the power losses, the cavity quality factor must be increased by decreasing the surface resistance. In this dissertation, the RF surface resistance is analyzed for a large variety of cavities made with different state-of-the-art surface treatments, with the goal of finding the surface treatment capable to return the highest Q-factor values in a cryomodule-like environment. This study analyzes not only the superconducting properties described by the BCS surface resistance, which is the contribution that takes into account dissipation due to quasi-particle excitations, but also the increasing of the surface resistance due to trapped flux. When cavities are cooled down below their critical temperature inside a cryomodule, there is always some remnant magnetic field that may be trapped increasing the global RF surface resistance. This thesis also analyzes how the fraction of external magnetic field, which is actually trapped in the cavity during the cooldown, can be minimized. This study is performed on an elliptical single-cell horizontally cooled cavity, resembling the geometry of cavities cooled in accelerator cryomodules. The horizontal cooldown study reveals that, as in case of the vertical cooldown, when the cooling is performed fast, large thermal gradients are created along the cavity helping magnetic flux expulsion. However, for this geometry the complete magnetic flux expulsion from the cavity equator is more difficult to achieve. This becomes even more challenging in presence of orthogonal magnetic field, that is easily trapped on top of the cavity equator

  3. The path to high Q-factors in superconducting accelerating cavities: Flux expulsion and surface resistance optimization

    Science.gov (United States)

    Martinello, Martina

    Accelerating cavities are devices resonating in the radio-frequency (RF) range used to accelerate charged particles in accelerators. Superconducting accelerating cavities are made out of niobium and operate at the liquid helium temperature. Even if superconducting, these resonating structures have some RF driven surface resistance that causes power dissipation. In order to decrease as much as possible the power losses, the cavity quality factor must be increased by decreasing the surface resistance. In this dissertation, the RF surface resistance is analyzed for a large variety of cavities made with different state-of-the-art surface treatments, with the goal of finding the surface treatment capable to return the highest Q-factor values in a cryomodule-like environment. This study analyzes not only the superconducting properties described by the BCS surface resistance, which is the contribution that takes into account dissipation due to quasi-particle excitations, but also the increasing of the surface resistance due to trapped flux. When cavities are cooled down below their critical temperature inside a cryomodule, there is always some remnant magnetic field that may be trapped increasing the global RF surface resistance. This thesis also analyzes how the fraction of external magnetic field, which is actually trapped in the cavity during the cooldown, can be minimized. This study is performed on an elliptical single-cell horizontally cooled cavity, resembling the geometry of cavities cooled in accelerator cryomodules. The horizontal cooldown study reveals that, as in case of the vertical cooldown, when the cooling is performed fast, large thermal gradients are created along the cavity helping magnetic flux expulsion. However, for this geometry the complete magnetic flux expulsion from the cavity equator is more difficult to achieve. This becomes even more challenging in presence of orthogonal magnetic field, that is easily trapped on top of the cavity equator

  4. Impact of Dust on Mars Surface Albedo and Energy Flux with LMD General Circulation Model

    Science.gov (United States)

    Singh, D.; Flanner, M.; Millour, E.; Martinez, G.

    2015-12-01

    Mars, just like Earth experience different seasons because of its axial tilt (about 25°). This causes growth and retreat of snow cover (primarily CO2) in Martian Polar regions. The perennial caps are the only place on the planet where condensed H2O is available at surface. On Mars, as much as 30% atmospheric CO2 deposits in each hemisphere depending upon the season. This leads to a significant variation on planet's surface albedo and hence effecting the amount of solar flux absorbed or reflected at the surface. General Circulation Model (GCM) of Laboratoire de Météorologie Dynamique (LMD) currently uses observationally derived surface albedo from Thermal Emission Spectrometer (TES) instrument for the polar caps. These TES albedo values do not have any inter-annual variability, and are independent of presence of any dust/impurity on surface. Presence of dust or other surface impurities can significantly reduce the surface albedo especially during and right after a dust storm. This change will also be evident in the surface energy flux interactions. Our work focuses on combining earth based Snow, Ice, and Aerosol Radiation (SNICAR) model with current state of GCM to incorporate the impact of dust on Martian surface albedo, and hence the energy flux. Inter-annual variability of surface albedo and planet's top of atmosphere (TOA) energy budget along with their correlation with currently available mission data will be presented.

  5. Estimating the amount and distribution of radon flux density from the soil surface in China

    International Nuclear Information System (INIS)

    Zhuo Weihai; Guo Qiuju; Chen Bo; Cheng Guan

    2008-01-01

    Based on an idealized model, both the annual and the seasonal radon ( 222 Rn) flux densities from the soil surface at 1099 sites in China were estimated by linking a database of soil 226 Ra content and a global ecosystems database. Digital maps of the 222 Rn flux density in China were constructed in a spatial resolution of 25 km x 25 km by interpolation among the estimated data. An area-weighted annual average 222 Rn flux density from the soil surface across China was estimated to be 29.7 ± 9.4 mBq m -2 s -1 . Both regional and seasonal variations in the 222 Rn flux densities are significant in China. Annual average flux densities in the southeastern and northwestern China are generally higher than those in other regions of China, because of high soil 226 Ra content in the southeastern area and high soil aridity in the northwestern one. The seasonal average flux density is generally higher in summer/spring than winter, since relatively higher soil temperature and lower soil water saturation in summer/spring than other seasons are common in China

  6. Improvements to the swath-level near-surface atmospheric state parameter retrievals within the NRL Ocean Surface Flux System (NFLUX)

    Science.gov (United States)

    May, J. C.; Rowley, C. D.; Meyer, H.

    2017-12-01

    The Naval Research Laboratory (NRL) Ocean Surface Flux System (NFLUX) is an end-to-end data processing and assimilation system used to provide near-real-time satellite-based surface heat flux fields over the global ocean. The first component of NFLUX produces near-real-time swath-level estimates of surface state parameters and downwelling radiative fluxes. The focus here will be on the satellite swath-level state parameter retrievals, namely surface air temperature, surface specific humidity, and surface scalar wind speed over the ocean. Swath-level state parameter retrievals are produced from satellite sensor data records (SDRs) from four passive microwave sensors onboard 10 platforms: the Special Sensor Microwave Imager/Sounder (SSMIS) sensor onboard the DMSP F16, F17, and F18 platforms; the Advanced Microwave Sounding Unit-A (AMSU-A) sensor onboard the NOAA-15, NOAA-18, NOAA-19, Metop-A, and Metop-B platforms; the Advanced Technology Microwave Sounder (ATMS) sensor onboard the S-NPP platform; and the Advanced Microwave Scannin Radiometer 2 (AMSR2) sensor onboard the GCOM-W1 platform. The satellite SDRs are translated into state parameter estimates using multiple polynomial regression algorithms. The coefficients to the algorithms are obtained using a bootstrapping technique with all available brightness temperature channels for a given sensor, in addition to a SST field. For each retrieved parameter for each sensor-platform combination, unique algorithms are developed for ascending and descending orbits, as well as clear vs cloudy conditions. Each of the sensors produces surface air temperature and surface specific humidity retrievals. The SSMIS and AMSR2 sensors also produce surface scalar wind speed retrievals. Improvement is seen in the SSMIS retrievals when separate algorithms are used for the even and odd scans, with the odd scans performing better than the even scans. Currently, NFLUX treats all SSMIS scans as even scans. Additional improvement in all of

  7. Understanding the Effect of Atmospheric Density on the Cosmic Ray Flux Variations at the Earth Surface

    OpenAIRE

    Dayananda, Mathes; Zhang, Xiaohang; Butler, Carola; He, Xiaochun

    2013-01-01

    We report in this letter for the first time the numerical simulations of muon and neutron flux variations at the surface of the earth with varying air densities in the troposphere and stratosphere. The simulated neutron and muon flux variations are in very good agreement with the measured neutron flux variation in Oulu and the muon flux variation in Atlanta. We conclude from this study that the stratosphere air density variation dominates the effects on the muon flux changes while the density...

  8. The Boston Methane Project: Mapping Surface Emissions to Inform Atmospheric Estimation of Urban Methane Flux

    Science.gov (United States)

    Phillips, N.; Crosson, E.; Down, A.; Hutyra, L.; Jackson, R. B.; McKain, K.; Rella, C.; Raciti, S. M.; Wofsy, S. C.

    2012-12-01

    Lost and unaccounted natural gas can amount to over 6% of Massachusetts' total annual greenhouse gas inventory (expressed as equivalent CO2 tonnage). An unknown portion of this loss is due to natural gas leaks in pipeline distribution systems. The objective of the Boston Methane Project is to estimate the overall leak rate from natural gas systems in metropolitan Boston, and to compare this flux with fluxes from the other primary methane emissions sources. Companion talks at this meeting describe the atmospheric measurement and modeling framework, and chemical and isotopic tracers that can partition total atmospheric methane flux into natural gas and non-natural gas components. This talk focuses on estimation of surface emissions that inform the atmospheric modeling and partitioning. These surface emissions include over 3,300 pipeline natural gas leaks in Boston. For the state of Massachusetts as a whole, the amount of natural gas reported as lost and unaccounted for by utility companies was greater than estimated landfill emissions by an order of magnitude. Moreover, these landfill emissions were overwhelmingly located outside of metro Boston, while gas leaks are concentrated in exactly the opposite pattern, increasing from suburban Boston toward the urban core. Work is in progress to estimate spatial distribution of methane emissions from wetlands and sewer systems. We conclude with a description of how these spatial data sets will be combined and represented for application in atmospheric modeling.

  9. On the use of radiative surface temperature to estimate sensible heat flux over sparse shrubs in Nevada

    Science.gov (United States)

    Chehbouni, A.; Nichols, W. D.; Qi, J.; Njoku, E. G.; Kerr, Y. H.; Cabot, F.

    1994-01-01

    The accurate partitioning of available energy into sensible and latent heat flux is crucial to the understanding of surface atmosphere interactions. This issue is more complicated in arid and semi arid regions where the relative contribution to surface fluxes from the soil and vegetation may vary significantly throughout the day and throughout the season. A three component model to estimate sensible heat flux over heterogeneous surfaces is presented. The surface was represented with two adjacent compartments. The first compartment is made up of two components, shrubs and shaded soil, the second of open 'illuminated' soil. Data collected at two different sites in Nevada (U.S.) during the Summers of 1991 and 1992 were used to evaluate model performance. The results show that the present model is sufficiently general to yield satisfactory results for both sites.

  10. Comparative study of elemental mercury flux measurement techniques over a Fennoscandian boreal peatland

    Science.gov (United States)

    Osterwalder, S.; Sommar, J.; Åkerblom, S.; Jocher, G.; Fritsche, J.; Nilsson, M. B.; Bishop, K.; Alewell, C.

    2018-01-01

    Quantitative estimates of the land-atmosphere exchange of gaseous elemental mercury (GEM) are biased by the measurement technique employed, because no standard method or scale in space and time are agreed upon. Here we present concurrent GEM exchange measurements over a boreal peatland using a novel relaxed eddy accumulation (REA) system, a rectangular Teflon® dynamic flux chamber (DFC) and a DFC designed according to aerodynamic considerations (Aero-DFC). During four consecutive days the DFCs were placed alternately on two measurement plots in every cardinal direction around the REA sampling mast. Spatial heterogeneity in peat surface characteristics (0-34 cm) was identified by measuring total mercury in eight peat cores (57 ± 8 ng g-1, average ± SE), vascular plant coverage (32-52%), water table level (4.5-14.1 cm) and dissolved gaseous elemental mercury concentrations (28-51 pg L-1) in the peat water. The GEM fluxes measured by the DFCs showed a distinct diel pattern, but no spatial difference in the average fluxes was detected (ANOVA, α = 0.05). Even though the correlation between the Teflon® DFC and Aero-DFC was significant (r = 0.76, p design is in agreement for cumulative flux estimates with the Aero-DFC, which incorporates the effect of atmospheric turbulence. The comparison was performed over a fetch with spatially rather homogenous GEM flux dynamics under fairly consistent weather conditions, minimizing the effect of weather influence on the data from the three measurement systems. However, in complex biomes with heterogeneous surface characteristics where there can be large spatial variability in GEM gas exchange, the small footprint of chambers (<0.2 m2) makes for large coefficients of variation. Thus many chamber measurement replications are needed to establish a credible biome GEM flux estimate, even for a single point in time. Dynamic flux chambers will, however, be able to resolve systematic differences between small scale features, such as

  11. Observational constraints on Arctic boundary-layer clouds, surface moisture and sensible heat fluxes

    Science.gov (United States)

    Wu, D. L.; Boisvert, L.; Klaus, D.; Dethloff, K.; Ganeshan, M.

    2016-12-01

    The dry, cold environment and dynamic surface variations make the Arctic a unique but difficult region for observations, especially in the atmospheric boundary layer (ABL). Spaceborne platforms have been the key vantage point to capture basin-scale changes during the recent Arctic warming. Using the AIRS temperature, moisture and surface data, we found that the Arctic surface moisture flux (SMF) had increased by 7% during 2003-2013 (18 W/m2 equivalent in latent heat), mostly in spring and fall near the Arctic coastal seas where large sea ice reduction and sea surface temperature (SST) increase were observed. The increase in Arctic SMF correlated well with the increases in total atmospheric column water vapor and low-level clouds, when compared to CALIPSO cloud observations. It has been challenging for climate models to reliably determine Arctic cloud radiative forcing (CRF). Using the regional climate model HIRHAM5 and assuming a more efficient Bergeron-Findeisen process with generalized subgrid-scale variability for total water content, we were able to produce a cloud distribution that is more consistent with the CloudSat/CALIPSO observations. More importantly, the modified schemes decrease (increase) the cloud water (ice) content in mixed-phase clouds, which help to improve the modeled CRF and energy budget at the surface, because of the dominant role of the liquid water in CRF. Yet, the coupling between Arctic low clouds and the surface is complex and has strong impacts on ABL. Studying GPS/COSMIC radio occultation (RO) refractivity profiles in the Arctic coldest and driest months, we successfully derived ABL inversion height and surface-based inversion (SBI) frequency, and they were anti-correlated over the Arctic Ocean. For the late summer and early fall season, we further analyzed Japanese R/V Mirai ship measurements and found that the open-ocean surface sensible heat flux (SSHF) can explain 10 % of the ABL height variability, whereas mechanisms such as cloud

  12. Linking atmospheric synoptic transport, cloud phase, surface energy fluxes, and sea-ice growth: observations of midwinter SHEBA conditions

    Science.gov (United States)

    Persson, P. Ola G.; Shupe, Matthew D.; Perovich, Don; Solomon, Amy

    2017-08-01

    Observations from the Surface Heat Budget of the Arctic Ocean (SHEBA) project are used to describe a sequence of events linking midwinter long-range advection of atmospheric heat and moisture into the Arctic Basin, formation of supercooled liquid water clouds, enhancement of net surface energy fluxes through increased downwelling longwave radiation, and reduction in near-surface conductive heat flux loss due to a warming of the surface, thereby leading to a reduction in sea-ice bottom growth. The analyses provide details of two events during Jan. 1-12, 1998, one entering the Arctic through Fram Strait and the other from northeast Siberia; winter statistics extend the results. Both deep, precipitating frontal clouds and post-frontal stratocumulus clouds impact the surface radiation and energy budget. Cloud liquid water, occurring preferentially in stratocumulus clouds extending into the base of the inversion, provides the strongest impact on surface radiation and hence modulates the surface forcing, as found previously. The observations suggest a minimum water vapor threshold, likely case dependent, for producing liquid water clouds. Through responses to the radiative forcing and surface warming, this cloud liquid water also modulates the turbulent and conductive heat fluxes, and produces a thermal wave penetrating into the sea ice. About 20-33 % of the observed variations of bottom ice growth can be directly linked to variations in surface conductive heat flux, with retarded ice growth occurring several days after these moisture plumes reduce the surface conductive heat flux. This sequence of events modulate pack-ice wintertime environmental conditions and total ice growth, and has implications for the annual sea-ice evolution, especially for the current conditions of extensive thinner ice.

  13. Reconstructing solar magnetic fields from historical observations: Testing the surface flux transport model

    Science.gov (United States)

    Virtanen, Iiro; Virtanen, Ilpo; Pevtsov, Alexei; Yeates, Anthony; Mursula, Kalevi

    2017-04-01

    We aim to use the surface flux transport model to simulate the long-term evolution of the photospheric magnetic field from historical observations. In this work we study the accuracy of the model and its sensitivity to uncertainties in its main parameters and the input data. We test the model by running simulations with different values of meridional circulation and supergranular diffusion parameters, and study how the flux distribution inside active regions and the initial magnetic field affect the simulation. We compare the results to assess how sensitive the simulation is to uncertainties in meridional circulation speed, supergranular diffusion and input data. We also compare the simulated magnetic field with observations. We find that there is generally good agreement between simulations and observations. While the model is not capable of replicating fine details of the magnetic field, the long-term evolution of the polar field is very similar in simulations and observations. Simulations typically yield a smoother evolution of polar fields than observations, that often include artificial variations due to observational limitations. We also find that the simulated field is fairly insensitive to uncertainties in model parameters or the input data. Due to the decay term included in the model the effects of the uncertainties are rather minor or temporary, lasting typically one solar cycle.

  14. Surface Flux Measurements at King Sejong Station in West Antarctica

    Science.gov (United States)

    Choi, T.; Lee, B.; Lee, H.; Shim, J.

    2004-12-01

    The Antarctic Peninsula is important in terms of global warming research due to pronounced increase of air temperature over the last century. The first eddy covariance system was established and turbulent fluxes of heat, water vapor, CO2 and momentum have been measured at King Sejong Station (62 \\deg 13øØS, 58 \\deg 47øØW) located in the northern edge of the Antarctic Peninsula since December in 2002. Our objectives are to better understand the interactions between the Antarctic land surface and the atmosphere and to test the feasibility of the long-term operation of eddy covariance system under extreme weather conditions. Various lichens cover the study area and the dominant species is Usnea fasciata-Himantormia. Based on the analyses on turbulent statistics such as integral turbulence characteristics of vertical velocity (w) and heat (T), stationarity test and investigation of correlation coefficient, they follow the Monin-Obukhov similarity and eddy covariance flux data were reliable. About 50 % of total retrieved sensible heat flux data could be used for further analysis. We will report on seasonal variations of energy and mass fluxes and environmental variables. In addition, factors controlling these fluxes will be presented. Acknowledgement: This study was supported by ¡rEnvironmental Monitoring on Human Impacts at the King Sejong Station, Antarctica¡_ (Project PP04102 of Korea Polar Research Institute) and ¡rEco-technopia 21 project¡_ (Ministry of Environment of Korea).

  15. Flux Meter Assesses the Effects of Groundwater, Surface Water, and Contaminated Sediment Interactions on Ecosystems

    Science.gov (United States)

    The slow flow of water between groundwater (GW) and surface water (SW) is often referred to as seepage, or in scientific terms, advective flux. This slow flow at the GW/SW interface presents measurement difficulties. This project was conducted to develop a durable advective flux ...

  16. Estimation of Surface Energy Fluxes from Bare Ground in a Tropical ...

    African Journals Online (AJOL)

    This investigation was designed to test the performance of Priestley Taylor method in the partitioning of the available energy into sensible and latent heat fluxes in a tropical site. Compared to eddy covariance measured fluxes, the conventional Priestley Taylor constant (αPT) of 1.25 gave low coefficient of determination and ...

  17. Feedback system for divertor impurity seeding based on real-time measurements of surface heat flux in the Alcator C-Mod tokamak

    Science.gov (United States)

    Brunner, D.; Burke, W.; Kuang, A. Q.; LaBombard, B.; Lipschultz, B.; Wolfe, S.

    2016-02-01

    Mitigation of the intense heat flux to the divertor is one of the outstanding problems in fusion energy. One technique that has shown promise is impurity seeding, i.e., the injection of low-Z gaseous impurities (typically N2 or Ne) to radiate and dissipate the power before it arrives to the divertor target plate. To this end, the Alcator C-Mod team has created a first-of-its-kind feedback system to control the injection of seed gas based on real-time surface heat flux measurements. Surface thermocouples provide real-time measurements of the surface temperature response to the plasma heat flux. The surface temperature measurements are inputted into an analog computer that "solves" the 1-D heat transport equation to deliver accurate, real-time signals of the surface heat flux. The surface heat flux signals are sent to the C-Mod digital plasma control system, which uses a proportional-integral-derivative (PID) algorithm to control the duty cycle demand to a pulse width modulated piezo valve, which in turn controls the injection of gas into the private flux region of the C-Mod divertor. This paper presents the design and implementation of this new feedback system as well as initial results using it to control divertor heat flux.

  18. Parameter optimization for surface flux transport models

    Science.gov (United States)

    Whitbread, T.; Yeates, A. R.; Muñoz-Jaramillo, A.; Petrie, G. J. D.

    2017-11-01

    Accurate prediction of solar activity calls for precise calibration of solar cycle models. Consequently we aim to find optimal parameters for models which describe the physical processes on the solar surface, which in turn act as proxies for what occurs in the interior and provide source terms for coronal models. We use a genetic algorithm to optimize surface flux transport models using National Solar Observatory (NSO) magnetogram data for Solar Cycle 23. This is applied to both a 1D model that inserts new magnetic flux in the form of idealized bipolar magnetic regions, and also to a 2D model that assimilates specific shapes of real active regions. The genetic algorithm searches for parameter sets (meridional flow speed and profile, supergranular diffusivity, initial magnetic field, and radial decay time) that produce the best fit between observed and simulated butterfly diagrams, weighted by a latitude-dependent error structure which reflects uncertainty in observations. Due to the easily adaptable nature of the 2D model, the optimization process is repeated for Cycles 21, 22, and 24 in order to analyse cycle-to-cycle variation of the optimal solution. We find that the ranges and optimal solutions for the various regimes are in reasonable agreement with results from the literature, both theoretical and observational. The optimal meridional flow profiles for each regime are almost entirely within observational bounds determined by magnetic feature tracking, with the 2D model being able to accommodate the mean observed profile more successfully. Differences between models appear to be important in deciding values for the diffusive and decay terms. In like fashion, differences in the behaviours of different solar cycles lead to contrasts in parameters defining the meridional flow and initial field strength.

  19. Annual mean statistics of the surface fluxes of the tropical Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    RameshKumar, M.R.; Rao, L.V.G.

    MEAN STATISTICS OF THE SURFACE FLUXES OF THE TROPICAL INDIAN OCEAN (Research Note) M. R. RAMESH KUMAR and L. V. GANGADHARA RAO Physical Oceanography Division, National Institute of Oceanography, Dona Paula, 403004, Goa, India (Received in final...

  20. Simultaneously estimation for surface heat fluxes of steel slab in a reheating furnace based on DMC predictive control

    International Nuclear Information System (INIS)

    Li, Yanhao; Wang, Guangjun; Chen, Hong

    2015-01-01

    The predictive control theory is utilized for the research of a simultaneous estimation of heat fluxes through the upper, side and lower surface of a steel slab in a walking beam type rolling steel reheating furnace. An inverse algorithm based on dynamic matrix control (DMC) is established. That is, each surface heat flux of a slab is simultaneously estimated through rolling optimization on the basis of temperature measurements in selected points of its interior by utilizing step response function as predictive model of a slab's temperature. The reliability of the DMC results is enhanced without prior assuming specific functions of heat fluxes over a period of future time. The inverse algorithm proposed a respective regularization to effectively improve the stability of the estimated results by considering obvious strength differences between the upper as well as lower and side surface heat fluxes of the slab. - Highlights: • The predictive control theory is adopted. • An inversion scheme based on DMC is established. • Upper, side and lower surface heat fluxes of slab are estimated based DMC. • A respective regularization is proposed to improve the stability of results

  1. A redetermination of the Barnes-Evans relation for surface flux in the V band

    International Nuclear Information System (INIS)

    Eaton, J.A.; Poe, C.H.

    1984-01-01

    Paying especial attention to the errors, we have redetermined the relation between visual flux at the star and color for stars with measured angular diameters. For stars cooler than the sun this is given both as a group of four polynomials in (V-R) for various parts of the range (V-R) >or approx.0.2, which start to recognize the fine structure in the flux-color relation, and as a straight line fitted to the data for 0,7 ≤ (V-R) ≤ 2.5. For stars hotter than the sun we give a table of surface flux vs. spectral type and (B-I) color. For stars later than the sun this flux-color relation is still defined almost entirely by giants. The conclusion that visual surface flux is a single function of (V-R) for all luminosity classes remains weak because of the small number of dwarfs and supergiants with angular diameters, likely systematic errors in the angular diameters of supergiants and the relatively large errors of individual angular diameters. The flux-color relation is combined with independent scales of bolometric corrections to give effective temperatures. We find that our results agree moderately well with those of Code et al. (1976), on which they are primarily based, for the hotter stars. However, they imply significant revisions of both the temperature and bolometric-correction scales for cool stars. 94 refs., 5 figs., 4 tabs. (author)

  2. Diurnal variability of surface fluxes at an oceanic station in the Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Sarma, Y.V.B.; Rao, D.P.

    Diurnal variability of the surface fluxes and ocean heat content was studied using the time-series data on marine surface meteorological parameters and upper ocean temperature collected at an oceanic station in the Bay of Bengal during 1st to 8th...

  3. Surface flux density distribution characteristics of bulk high-Tc superconductor in external magnetic field

    International Nuclear Information System (INIS)

    Torii, S.; Yuasa, K.

    2004-01-01

    Various magnetic levitation systems using oxide superconductors are developed as strong pinning forces are obtained in melt-processed bulk. However, the trapped flux of superconductor is moved by flux creep and fluctuating magnetic field. Therefore, to examine the internal condition of superconductor, the authors measure the dynamic surface flux density distribution of YBCO bulk. Flux density measurement system has a structure with the air-core coil and the Hall sensors. Ten Hall sensors are arranged in series. The YBCO bulk, which has 25 mm diameter and 13 mm thickness, is field cooled by liquid nitrogen. After that, magnetic field is changed by the air-core coil. This paper describes about the measured results of flux density distribution of YBCO bulk in the various frequencies of air-core coils currents

  4. Surface flux density distribution characteristics of bulk high- Tc superconductor in external magnetic field

    Science.gov (United States)

    Torii, S.; Yuasa, K.

    2004-10-01

    Various magnetic levitation systems using oxide superconductors are developed as strong pinning forces are obtained in melt-processed bulk. However, the trapped flux of superconductor is moved by flux creep and fluctuating magnetic field. Therefore, to examine the internal condition of superconductor, the authors measure the dynamic surface flux density distribution of YBCO bulk. Flux density measurement system has a structure with the air-core coil and the Hall sensors. Ten Hall sensors are arranged in series. The YBCO bulk, which has 25 mm diameter and 13 mm thickness, is field cooled by liquid nitrogen. After that, magnetic field is changed by the air-core coil. This paper describes about the measured results of flux density distribution of YBCO bulk in the various frequencies of air-core coils currents.

  5. Comparison of surface sensible and latent heat fluxes over the Tibetan Plateau from reanalysis and observations

    Science.gov (United States)

    Xie, Jin; Yu, Ye; Li, Jiang-lin; Ge, Jun; Liu, Chuan

    2018-02-01

    Surface sensible and latent heat fluxes (SH and LE) over the Tibetan Plateau (TP) have been under research since 1950s, especially for recent several years, by mainly using observation, reanalysis, and satellite data. However, the spatiotemporal changes are not consistent among different studies. This paper focuses on the spatiotemporal variation of SH and LE over the TP from 1981 to 2013 using reanalysis data sets (ERA-Interim, JRA-55, and MERRA) and observations. Results show that the spatiotemporal changes from the three reanalysis data sets are significantly different and the probable causes are discussed. Averaged for the whole TP, both SH and LE from MERRA are obviously higher than the other two reanalysis data sets. ERA-Interim shows a significant downward trend for SH and JRA-55 shows a significant increase of LE during the 33 years with other data sets having no obvious changes. By comparing the heat fluxes and some climate factors from the reanalysis with observations, it is found that the differences of heat fluxes among the three reanalysis data sets are closely related to their differences in meteorological conditions as well as the different parameterizations for surface transfer coefficients. In general, the heat fluxes from the three reanalysis have a better representation in the western TP than that in the eastern TP under inter-annual scale. While in terms of monthly variation, ERA-Interim may have better applicability in the eastern TP with dense vegetation conditions, while SH of JRA-55 and LE of MERRA are probably more representative for the middle and western TP with poor vegetation conditions.

  6. An assessment of TropFlux and NCEP air-sea fluxes on ROMS simulations over the Bay of Bengal region

    Science.gov (United States)

    Dey, Dipanjan; Sil, Sourav; Jana, Sudip; Pramanik, Saikat; Pandey, P. C.

    2017-12-01

    This study presents an assessment of the TropFlux and the National Centers for Environmental Prediction (NCEP) reanalysis air-sea fluxes in simulating the surface and subsurface oceanic parameters over the Bay of Bengal (BoB) region during 2002-2014 using the Regional Ocean Modelling System (ROMS). The assessment has been made by comparing the simulated fields with in-situ and satellite observations. The simulated surface and subsurface temperatures in the TropFlux forced experiment (TropFlux-E) show better agreement with the Research Moored Array for African-Asian-Australian Monsoon Analysis (RAMA) and Argo observations than the NCEP forced experiment (NCEP-E). The BoB domain averaged sea surface temperature (SST) simulated in the NCEP-E is consistently cooler than the satellite SST, with a root mean square error (RMSE) of 0.79 °C. Moreover, NCEP-E shows a limitation in simulating the observed seasonal cycle of the SST due to substantial underestimation of the pre-monsoon SST peak. These limitations are mostly due to the lower values of the NCEP net heat flux. The seasonal and interannual variations of SST in the TropFlux-E are better comparable to the observations with correlations and skills more than 0.80 and 0.90 respectively. However, SST is overestimated during summer monsoon periods mainly due to higher net heat flux. The superiority of TropFlux forcing over the NCEP reanalysis can also be seen when simulating the interannual variabilities of the magnitude and vertical extent of Wyrtki jets at two equatorial RAMA buoy locations. The jet is weaker in the NCEP-E relative to the TropFlux-E and observations. The simulated sea surface height anomalies (SSHA) from both the experiments are able to capture the regions of positive and negative SSHA with respect to satellite-derived altimeter data with better performance in the TropFlux-E. The speed of the westward propagating Rossby wave along 18°N in the TropFlux-E is found to be about 4.7 cm/s, which is close to

  7. Turbulent flux modelling with a simple 2-layer soil model and extrapolated surface temperature applied at Nam Co Lake basin on the Tibetan Plateau

    Directory of Open Access Journals (Sweden)

    T. Gerken

    2012-04-01

    Full Text Available This paper introduces a surface model with two soil-layers for use in a high-resolution circulation model that has been modified with an extrapolated surface temperature, to be used for the calculation of turbulent fluxes. A quadratic temperature profile based on the layer mean and base temperature is assumed in each layer and extended to the surface. The model is tested at two sites on the Tibetan Plateau near Nam Co Lake during four days during the 2009 Monsoon season. In comparison to a two-layer model without explicit surface temperature estimate, there is a greatly reduced delay in diurnal flux cycles and the modelled surface temperature is much closer to observations. Comparison with a SVAT model and eddy covariance measurements shows an overall reasonable model performance based on RMSD and cross correlation comparisons between the modified and original model. A potential limitation of the model is the need for careful initialisation of the initial soil temperature profile, that requires field measurements. We show that the modified model is capable of reproducing fluxes of similar magnitudes and dynamics when compared to more complex methods chosen as a reference.

  8. Bi-Maxwellian electron energy distribution function in the vicinity of the last closed flux surface in fusion plasma

    Czech Academy of Sciences Publication Activity Database

    Popov, T.S.V.K.; Dimitrova, Miglena; Pedrosa, M. A.; López-Bruna, D.; Horáček, Jan; Kovačič, J.; Dejarnac, Renaud; Stöckel, Jan; Aftanas, Milan; Böhm, Petr; Bílková, Petra; Hidalgo, C.; Pánek, Radomír

    2015-01-01

    Roč. 57, č. 11 (2015), č. článku 115011. ISSN 0741-3335 R&D Projects: GA ČR(CZ) GAP205/12/2327; GA MŠk(CZ) LM2011021 Institutional support: RVO:61389021 Keywords : COMPASS tokamak, parallel power flux density * TJ-II stellarator * bi-Maxwellian EEDF * last closed flux surface * SOL * parallel power flux density Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 2.404, year: 2015

  9. Legirani praški za navarjanje z večžično elektrodo: Alloyed fluxes for surfacing with multiple - wire electrode:

    OpenAIRE

    Kejžar, Božena; Kejžar, Rajko

    1997-01-01

    Submerged arc surfacing with alloyed agglomerated fluxes permits unalloyed and low-alloy structural steels to be surfaced in one layer of high-alloyed claddings. Surfacing dilution produced by fusion of the parent metal, and burn-off of alloying elements are substituted by additional alloying by means of a welding flux, which is, in the case of the above-mentioned surfacing processes, the main carrier of alloying elements for surfacing alloying. With alloyed agglomerated fluxes, it is recomme...

  10. Uncertainties of Large-Scale Forcing Caused by Surface Turbulence Flux Measurements and the Impacts on Cloud Simulations at the ARM SGP Site

    Science.gov (United States)

    Tang, S.; Xie, S.; Tang, Q.; Zhang, Y.

    2017-12-01

    Two types of instruments, the eddy correlation flux measurement system (ECOR) and the energy balance Bowen ratio system (EBBR), are used at the Atmospheric Radiation Measurement (ARM) program Southern Great Plains (SGP) site to measure surface latent and sensible fluxes. ECOR and EBBR typically sample different land surface types, and the domain-mean surface fluxes derived from ECOR and EBBR are not always consistent. The uncertainties of the surface fluxes will have impacts on the derived large-scale forcing data and further affect the simulations of single-column models (SCM), cloud-resolving models (CRM) and large-eddy simulation models (LES), especially for the shallow-cumulus clouds which are mainly driven by surface forcing. This study aims to quantify the uncertainties of the large-scale forcing caused by surface turbulence flux measurements and investigate the impacts on cloud simulations using long-term observations from the ARM SGP site.

  11. Stable water isotope and surface heat flux simulation using ISOLSM: Evaluation against in-situ measurements

    KAUST Repository

    Cai, Mick Y.; Wang, Lixin; Parkes, Stephen; Strauss, Josiah; McCabe, Matthew; Evans, Jason P.; Griffiths, Alan D.

    2015-01-01

    The stable isotopes of water are useful tracers of water sources and hydrological processes. Stable water isotope-enabled land surface modeling is a relatively new approach for characterizing the hydrological cycle, providing spatial and temporal variability for a number of hydrological processes. At the land surface, the integration of stable water isotopes with other meteorological measurements can assist in constraining surface heat flux estimates and discriminate between evaporation (E) and transpiration (T). However, research in this area has traditionally been limited by a lack of continuous in-situ isotopic observations. Here, the National Centre for Atmospheric Research stable isotope-enabled Land Surface Model (ISOLSM) is used to simulate the water and energy fluxes and stable water isotope variations. The model was run for a period of one month with meteorological data collected from a coastal sub-tropical site near Sydney, Australia. The modeled energy fluxes (latent heat and sensible heat) agreed reasonably well with eddy covariance observations, indicating that ISOLSM has the capacity to reproduce observed flux behavior. Comparison of modeled isotopic compositions of evapotranspiration (ET) against in-situ Fourier Transform Infrared spectroscopy (FTIR) measured bulk water vapor isotopic data (10. m above the ground), however, showed differences in magnitude and temporal patterns. The disparity is due to a small contribution from local ET fluxes to atmospheric boundary layer water vapor (~1% based on calculations using ideal gas law) relative to that advected from the ocean for this particular site. Using ISOLSM simulation, the ET was partitioned into E and T with 70% being T. We also identified that soil water from different soil layers affected T and E differently based on the simulated soil isotopic patterns, which reflects the internal working of ISOLSM. These results highlighted the capacity of using the isotope-enabled models to discriminate

  12. Stable water isotope and surface heat flux simulation using ISOLSM: Evaluation against in-situ measurements

    KAUST Repository

    Cai, Mick Y.

    2015-04-01

    The stable isotopes of water are useful tracers of water sources and hydrological processes. Stable water isotope-enabled land surface modeling is a relatively new approach for characterizing the hydrological cycle, providing spatial and temporal variability for a number of hydrological processes. At the land surface, the integration of stable water isotopes with other meteorological measurements can assist in constraining surface heat flux estimates and discriminate between evaporation (E) and transpiration (T). However, research in this area has traditionally been limited by a lack of continuous in-situ isotopic observations. Here, the National Centre for Atmospheric Research stable isotope-enabled Land Surface Model (ISOLSM) is used to simulate the water and energy fluxes and stable water isotope variations. The model was run for a period of one month with meteorological data collected from a coastal sub-tropical site near Sydney, Australia. The modeled energy fluxes (latent heat and sensible heat) agreed reasonably well with eddy covariance observations, indicating that ISOLSM has the capacity to reproduce observed flux behavior. Comparison of modeled isotopic compositions of evapotranspiration (ET) against in-situ Fourier Transform Infrared spectroscopy (FTIR) measured bulk water vapor isotopic data (10. m above the ground), however, showed differences in magnitude and temporal patterns. The disparity is due to a small contribution from local ET fluxes to atmospheric boundary layer water vapor (~1% based on calculations using ideal gas law) relative to that advected from the ocean for this particular site. Using ISOLSM simulation, the ET was partitioned into E and T with 70% being T. We also identified that soil water from different soil layers affected T and E differently based on the simulated soil isotopic patterns, which reflects the internal working of ISOLSM. These results highlighted the capacity of using the isotope-enabled models to discriminate

  13. Modeling surface energy fluxes and thermal dynamics of a seasonally ice-covered hydroelectric reservoir.

    Science.gov (United States)

    Wang, Weifeng; Roulet, Nigel T; Strachan, Ian B; Tremblay, Alain

    2016-04-15

    The thermal dynamics of human created northern reservoirs (e.g., water temperatures and ice cover dynamics) influence carbon processing and air-water gas exchange. Here, we developed a process-based one-dimensional model (Snow, Ice, WAater, and Sediment: SIWAS) to simulate a full year's surface energy fluxes and thermal dynamics for a moderately large (>500km(2)) boreal hydroelectric reservoir in northern Quebec, Canada. There is a lack of climate and weather data for most of the Canadian boreal so we designed SIWAS with a minimum of inputs and with a daily time step. The modeled surface energy fluxes were consistent with six years of observations from eddy covariance measurements taken in the middle of the reservoir. The simulated water temperature profiles agreed well with observations from over 100 sites across the reservoir. The model successfully captured the observed annual trend of ice cover timing, although the model overestimated the length of ice cover period (15days). Sensitivity analysis revealed that air temperature significantly affects the ice cover duration, water and sediment temperatures, but that dissolved organic carbon concentrations have little effect on the heat fluxes, and water and sediment temperatures. We conclude that the SIWAS model is capable of simulating surface energy fluxes and thermal dynamics for boreal reservoirs in regions where high temporal resolution climate data are not available. SIWAS is suitable for integration into biogeochemical models for simulating a reservoir's carbon cycle. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Mixed quantum-classical equilibrium in global flux surface hopping

    International Nuclear Information System (INIS)

    Sifain, Andrew E.; Wang, Linjun; Prezhdo, Oleg V.

    2015-01-01

    Global flux surface hopping (GFSH) generalizes fewest switches surface hopping (FSSH)—one of the most popular approaches to nonadiabatic molecular dynamics—for processes exhibiting superexchange. We show that GFSH satisfies detailed balance and leads to thermodynamic equilibrium with accuracy similar to FSSH. This feature is particularly important when studying electron-vibrational relaxation and phonon-assisted transport. By studying the dynamics in a three-level quantum system coupled to a classical atom in contact with a classical bath, we demonstrate that both FSSH and GFSH achieve the Boltzmann state populations. Thermal equilibrium is attained significantly faster with GFSH, since it accurately represents the superexchange process. GFSH converges closer to the Boltzmann averages than FSSH and exhibits significantly smaller statistical errors

  15. Correlations Between Sea-Surface Salinity Tendencies and Freshwater Fluxes in the Pacific Ocean

    Science.gov (United States)

    Li, Zhen; Adamec, David

    2007-01-01

    Temporal changes in sea-surface salinity (SSS) from 21 years of a high resolution model integration of the Pacific Ocean are correlated with the freshwater flux that was used to force the integration. The correlations are calculated on a 1 x10 grid, and on a monthly scale to assess the possibility of deducing evaporation minus precipitation (E-P) fields from the salinity measurements to be taken by the upcoming Aquarius/SAC-D mission. Correlations between the monthly mean E-P fields and monthly mean SSS temporal tendencies are mainly zonally-oriented, and are highest where the local precipitation is relatively high. Nonseasonal (deviations from the monthly mean) correlations are highest along mid-latitude storm tracks and are relatively small in the tropics. The response of the model's surface salinity to surface forcing is very complex, and retrievals of freshwater fluxes from SSS measurements alone will require consideration of other processes, including horizontal advection and vertical mixing, rather than a simple balance between the two.

  16. Effects of nonuniform surface heat flux and uniform volumetric heating on blanket design for fusion reactors

    International Nuclear Information System (INIS)

    Hasan, M.Z.

    1988-05-01

    An analytical solution for the temperature profile and film temperature drop for fully-developed, laminar flow in a circular tube is provided. The surface heat flux varies circcimferentally but is constant along the axis of the tube. The volulmetric heat generation is uniform in the fluid. The fully developed laminar velocity profile is approximated by a power velocity profile to represent the flattening effect of a perpendicular magnetic field when the coolant is electrivally conductive. The presence of volumetric heat generation in the fluid adds another component to the film temperature drop to that due to the surface heat flux. The reduction of the boundary layer thickness by a perpendicular magnetic field reduces both of these two film temperature drops. A strong perpendicular magnetic field can reduce the film termperatiure drop by a factor of two if the fluid is electrically conducting. The effect of perpendicualr magnetic field )or the flatness of the velocity profile) is less pronounced on teh film termperature drop due to nonuniform surfacae heat flux than on that due to uniform surface heat flux. An example is provided to show the relative effects on these two film temperd

  17. Human Effects and Soil Surface CO2 fluxes in Tropical Urban Green Areas, Singapore

    Science.gov (United States)

    Ng, Bernard; Gandois, Laure; Kai, Fuu Ming; Chua, Amy; Cobb, Alex; Harvey, Charles; Hutyra, Lucy

    2013-04-01

    Urban green spaces are appreciated for their amenity value, with increasing interest in the ecosystem services they could provide (e.g. climate amelioration and increasingly as possible sites for carbon sequestration). In Singapore, turfgrass occupies approximately 20% of the total land area and is readily found on both planned and residual spaces. This project aims at understanding carbon fluxes in tropical urban green areas, including controls of soil environmental factors and the effect of urban management techniques. Given the large pool of potentially labile carbon, management regimes are recognised to have an influence on soil environmental factors (temperature and moisture), this would affect soil respiration and feedbacks to the greenhouse effect. A modified closed dynamic chamber method was employed to measure total soil respiration fluxes. In addition to soil respiration rates, environmental factors such as soil moisture and temperature, and ambient air temperature were monitored for the site in an attempt to evaluate their control on the observed fluxes. Measurements of soil-atmosphere CO2 exchanges are reported for four experimental plots within the Singtel-Kranji Radio Transmission Station (103o43'49E, 1o25'53N), an area dominated by Axonopus compressus. Different treatments such as the removal of turf, and application of clippings were effected as a means to determine the fluxes from the various components (respiration of soil and turf, and decomposition of clippings), and to explore the effects of human intervention on observed effluxes. The soil surface CO2 fluxes observed during the daylight hours ranges from 2.835 + 0.772 umol m-2 s-1 for the bare plot as compared to 6.654 + 1.134 umol m-2 s-1 for the turfed plot; this could be attributed to both autotrophic and heterotrophic respiration. Strong controls of both soil temperature and soil moisture are observed on measured soil fluxes. On the base soils, fluxes were positively correlated to soil

  18. Estimation of annual heat flux balance at the sea surface from sst (NOAA-satellite and ships drift data off southeast Brazil

    Directory of Open Access Journals (Sweden)

    Yoshimine Ikeda

    1985-01-01

    Full Text Available The objective of this work is to study the possibility of estimating the heat flux balance at the sea surface from GOSSTCOMP (Global Ocean Sea Surface Temperature Computation developed by NOAA/NESS, USA, and sea surface current data based from ships drift information obtained from Pilot Charts, published by the Diretoria de Hidrografia e Navegação (DHN, Brazilian Navy. The annual mean value of the heat flux balance at the sea surface off southeast Brazil for 1977, is estimated from data on the balance between the heat transported by the currents and that transported by eddy diffusion for each volume defined as 2º x 2º (Lat. x Long. square with a constant depth equivalent to an oceanic mixed layer, 100 m thick. Results show several oceanic areas where there are net flows of heat from atmosphere towards the sea surface. In front of Rio de Janeiro the heat flow was downward and up to 70 ly day-1 and is probably related to the upwellirug phenomenon normally occurring in that area. Another coastal area between Lat. 25ºS to 28ºS indicated an downward flow up to 50 ly day-1; and for an area south of Lat. 27ºS, Long. 040ºW - 048ºW an downward flow up to 200 ly day-1, where the transfer was probably due to the cold water of a nortward flux from the Falkland (Malvinas Current. Results also show several oceanic areas where net flows of heat (of about -100 ly day-1 were toward the atmosphere. In the oceanic areas Lat. 19ºS - 23ºS and Lat. 24ºS - 30ºS, the flows were probably due to the warm water of a southward flux of the Brazil Current. The resulting fluxes from the warm waters of the Brazil Current when compared with those from warm waters of the Gulf Stream and Kuroshio, indicate that the Gulf Stream carries about 3.3 times and the Kuroshio 1.7 times more heat than the Brazil Current. These values agree with those of data available on the heat fluxes of the above mentioned Currents calculated by different methods (Budyko, 1974.

  19. Total luminous flux measurement for flexible surface sources with an integrating sphere photometer

    International Nuclear Information System (INIS)

    Yu, Hsueh-Ling; Liu, Wen-Chun

    2014-01-01

    Applying an integrating sphere photometer for total luminous flux measurement is a widely used method. However, the measurement accuracy depends on the spatial uniformity of the integrating sphere, especially when the test sample has a different light distribution from that of the standard source. Therefore, spatial correction is needed to eliminate the effect caused by non-uniformity. To reduce the inconvenience of spatial correction but retain the measurement accuracy, a new type of working standard is designed for flexible and curved surface sources. Applying this new type standard source, the measurement deviation due to different orientations is reduced by an order of magnitude compared with using a naked incandescent lamp as the standard source. (paper)

  20. Two-phase jet impingement cooling for high heat flux wide band-gap devices using multi-scale porous surfaces

    International Nuclear Information System (INIS)

    Joshi, Shailesh N.; Dede, Ercan M.

    2017-01-01

    Highlights: • Jet impingement with phase change on multi-scale porous surfaces is investigated. • Porous coated flat, pin-fin, open tunnel, and closed tunnel structures are studied. • Boiling curve, heat transfer coefficient, and pressure drop metrics are reported. • Flow visualization shows vapor removal from the surface is a key aspect of design. • The porous coated pin-fin surface exhibits superior two-phase cooling performance. - Abstract: In the future, wide band-gap (WBG) devices such as silicon carbide and gallium nitride will be widely used in automotive power electronics due to performance advantages over silicon-based devices. The high heat fluxes dissipated by WBG devices pose extreme cooling challenges that demand the use of advanced thermal management technologies such as two-phase cooling. In this light, we describe the performance of a submerged two-phase jet impingement cooler in combination with porous coated heat spreaders and multi-jet orifices. The cooling performance of four different porous coated structures was evaluated using R-245fa as the coolant at sub-cooling of 5 K. The results show that the boiling performance of a pin-fin heat spreader is the highest followed by that for an open tunnel (OPT), closed tunnel (CLT), and flat heat spreader. Furthermore, the flat heat spreader demonstrated the lowest critical heat flux (CHF), while the pin-fin surface sustained a heat flux of 218 W/cm 2 without reaching CHF. The CHF values of the OPT and CLT surfaces were 202 W/cm 2 and 194 W/cm 2 , respectively. The pin-fin heat spreader has the highest two-phase heat transfer coefficient of 97,800 W/m 2 K, while the CLT surface has the lowest heat transfer coefficient of 69,300 W/m 2 K, both at a heat flux of 165 W/cm 2 . The variation of the pressure drop of all surfaces is similar for the entire range of heat fluxes tested. The flat heat spreader exhibited the least pressure drop, 1.73 kPa, while the CLT surface had the highest, 2.17 kPa at a

  1. The validation of ocean surface heat fluxes in AMIP

    International Nuclear Information System (INIS)

    Gleckler, P.J.; Randall, D.A.

    1993-09-01

    Recent intercomparisons of Atmospheric General Circulation Models (AGCMS) constrained with sea-surface temperatures have shown that while there are substantial differences among various models (with each other and available observations), overall the differences between them have been decreasing. The primary goal of AMIP is to enable a systematic intercomparison and validation of state-of-the- art AGCMs by supporting in-depth diagnosis of and interpretation of the model results. Official AMIP simulations are 10 years long, using monthly mean Sea-Surface Temperatures (SSTs) and sea ice conditions which are representative of the 1979--1988 decade. Some model properties are also dictated by the design of AMIP such as the solar constant, the atmospheric CO 2 concentration, and the approximate horizontal resolution. In this paper, some of the preliminary results of AMIP Subproject No. 5 will be summarized. The focus will be on the intercomparison and validation of ocean surface heat fluxes of the AMIP simulations available thus far

  2. Multi-sensor remote sensing parameterization of heat fluxes over heterogeneous land surfaces

    NARCIS (Netherlands)

    Faivre, R.D.

    2014-01-01

    The parameterization of heat transfer by remote sensing, and based on SEBS scheme for turbulent heat fluxes retrieval, already proved to be very convenient for estimating evapotranspiration (ET) over homogeneous land surfaces. However, the use of such a method over heterogeneous landscapes (e.g.

  3. Determination of 3D Equilibria from Flux Surface Knowledge Only

    International Nuclear Information System (INIS)

    Mynick, H.E.; Pomphrey, N.

    2001-01-01

    We show that the method of Christiansen and Taylor, from which complete tokamak equilibria can be determined given only knowledge of the shape of the flux surfaces, can be extended to 3-dimensional equilibria, such as those of stellarators. As for the tokamak case, the given geometric knowledge has a high degree of redundancy, so that the full equilibrium can be obtained using only a small portion of that information

  4. An Optimal Estimation Method to Obtain Surface Layer Turbulent Fluxes from Profile Measurements

    Science.gov (United States)

    Kang, D.

    2015-12-01

    In the absence of direct turbulence measurements, the turbulence characteristics of the atmospheric surface layer are often derived from measurements of the surface layer mean properties based on Monin-Obukhov Similarity Theory (MOST). This approach requires two levels of the ensemble mean wind, temperature, and water vapor, from which the fluxes of momentum, sensible heat, and water vapor can be obtained. When only one measurement level is available, the roughness heights and the assumed properties of the corresponding variables at the respective roughness heights are used. In practice, the temporal mean with large number of samples are used in place of the ensemble mean. However, in many situations the samples of data are taken from multiple levels. It is thus desirable to derive the boundary layer flux properties using all measurements. In this study, we used an optimal estimation approach to derive surface layer properties based on all available measurements. This approach assumes that the samples are taken from a population whose ensemble mean profile follows the MOST. An optimized estimate is obtained when the results yield a minimum cost function defined as a weighted summation of all error variance at each sample altitude. The weights are based one sample data variance and the altitude of the measurements. This method was applied to measurements in the marine atmospheric surface layer from a small boat using radiosonde on a tethered balloon where temperature and relative humidity profiles in the lowest 50 m were made repeatedly in about 30 minutes. We will present the resultant fluxes and the derived MOST mean profiles using different sets of measurements. The advantage of this method over the 'traditional' methods will be illustrated. Some limitations of this optimization method will also be discussed. Its application to quantify the effects of marine surface layer environment on radar and communication signal propagation will be shown as well.

  5. Achieving scale-independent land-surface flux estimates - Application of the Multiscale Parameter Regionalization (MPR) to the Noah-MP land-surface model across the contiguous USA

    Science.gov (United States)

    Thober, S.; Mizukami, N.; Samaniego, L. E.; Attinger, S.; Clark, M. P.; Cuntz, M.

    2016-12-01

    Land-surface models use a variety of process representations to calculate terrestrial energy, water and biogeochemical fluxes. These process descriptions are usually derived from point measurements but are scaled to much larger resolutions in applications that range from about 1 km in catchment hydrology to 100 km in climate modelling. Both, hydrologic and climate models are nowadays run on different spatial resolutions, using the exact same land surface representations. A fundamental criterion for the physical consistency of land-surface simulations across scales is that a flux estimated over a given area is independent of the spatial model resolution (i.e., the flux-matching criterion). The Noah-MP land surface model considers only one soil and land cover type per model grid cell without any representation of subgrid variability, implying a weak flux-matching. A fractional approach simulates subgrid variability but it requires a higher computational demand than using effective parameters and it is used only for land cover in current land surface schemes. A promising approach to derive scale-independent parameters is the Multiscale Parameter Regionalization (MPR) technique, which consists of two steps: first, it applies transfer functions directly to high-resolution data (such as 100 m soil maps) to derive high-resolution model parameter fields, acknowledging the full subgrid variability. Second, it upscales these high-resolution parameter fields to the model resolution by using appropriate upscaling operators. MPR has shown to improve substantially the scalability of hydrologic models. Here, we apply the MPR technique to the Noah-MP land-surface model for a large sample of basins distributed across the contiguous USA. Specifically, we evaluate the flux-matching criterion for several hydrologic fluxes such as evapotranspiration and total runoff at scales ranging from 3 km to 48 km. We also investigate a p-norm scaling operator that goes beyond the current

  6. Flux threshold measurements of He-ion beam induced nanofuzz formation on hot tungsten surfaces

    International Nuclear Information System (INIS)

    Meyer, F W; Hijazi, H; Bannister, M E; Unocic, K A; Garrison, L M; Parish, C M

    2016-01-01

    We report measurements of the energy dependence of flux thresholds and incubation fluences for He-ion induced nano-fuzz formation on hot tungsten surfaces at UHV conditions over a wide energy range using real-time sample imaging of tungsten target emissivity change to monitor the spatial extent of nano-fuzz growth, corroborated by ex situ SEM and FIB/SEM analysis, in conjunction with accurate ion-flux profile measurements. The measurements were carried out at the multicharged ion research facility (MIRF) at energies from 218 eV to 8.5 keV, using a high-flux deceleration module and beam flux monitor for optimizing the decel optics on the low energy MIRF beamline. The measurements suggest that nano-fuzz formation proceeds only if a critical rate of change of trapped He density in the W target is exceeded. To understand the energy dependence of the observed flux thresholds, the energy dependence of three contributing factors: ion reflection, ion range and target damage creation, were determined using the SRIM simulation code. The observed energy dependence can be well reproduced by the combined energy dependences of these three factors. The incubation fluences deduced from first visual appearance of surface emissivity change were (2–4) × 10 23 m −2 at 218 eV, and roughly a factor of 10 less at the higher energies, which were all at or above the displacement energy threshold. The role of trapping at C impurity sites is discussed. (paper)

  7. Evaluation of NASA's Carbon Monitoring System (CMS) Flux Pilot: Terrestrial CO2 Fluxes

    Science.gov (United States)

    Fisher, J. B.; Polhamus, A.; Bowman, K. W.; Collatz, G. J.; Potter, C. S.; Lee, M.; Liu, J.; Jung, M.; Reichstein, M.

    2011-12-01

    NASA's Carbon Monitoring System (CMS) flux pilot project combines NASA's Earth System models in land, ocean and atmosphere to track surface CO2 fluxes. The system is constrained by atmospheric measurements of XCO2 from the Japanese GOSAT satellite, giving a "big picture" view of total CO2 in Earth's atmosphere. Combining two land models (CASA-Ames and CASA-GFED), two ocean models (ECCO2 and NOBM) and two atmospheric chemistry and inversion models (GEOS-5 and GEOS-Chem), the system brings together the stand-alone component models of the Earth System, all of which are run diagnostically constrained by a multitude of other remotely sensed data. Here, we evaluate the biospheric land surface CO2 fluxes (i.e., net ecosystem exchange, NEE) as estimated from the atmospheric flux inversion. We compare against the prior bottom-up estimates (e.g., the CASA models) as well. Our evaluation dataset is the independently derived global wall-to-wall MPI-BGC product, which uses a machine learning algorithm and model tree ensemble to "scale-up" a network of in situ CO2 flux measurements from 253 globally-distributed sites in the FLUXNET network. The measurements are based on the eddy covariance method, which uses observations of co-varying fluxes of CO2 (and water and energy) from instruments on towers extending above ecosystem canopies; the towers integrate fluxes over large spatial areas (~1 km2). We present global maps of CO2 fluxes and differences between products, summaries of fluxes by TRANSCOM region, country, latitude, and biome type, and assess the time series, including timing of minimum and maximum fluxes. This evaluation shows both where the CMS is performing well, and where improvements should be directed in further work.

  8. Estimating surface CO2 fluxes from space-borne CO2 dry air mole fraction observations using an ensemble Kalman Filter

    Directory of Open Access Journals (Sweden)

    S. Dance

    2009-04-01

    Full Text Available We have developed an ensemble Kalman Filter (EnKF to estimate 8-day regional surface fluxes of CO2 from space-borne CO2 dry-air mole fraction observations (XCO2 and evaluate the approach using a series of synthetic experiments, in preparation for data from the NASA Orbiting Carbon Observatory (OCO. The 32-day duty cycle of OCO alternates every 16 days between nadir and glint measurements of backscattered solar radiation at short-wave infrared wavelengths. The EnKF uses an ensemble of states to represent the error covariances to estimate 8-day CO2 surface fluxes over 144 geographical regions. We use a 12×8-day lag window, recognising that XCO2 measurements include surface flux information from prior time windows. The observation operator that relates surface CO2 fluxes to atmospheric distributions of XCO2 includes: a the GEOS-Chem transport model that relates surface fluxes to global 3-D distributions of CO2 concentrations, which are sampled at the time and location of OCO measurements that are cloud-free and have aerosol optical depths 2 profiles to XCO2, accounting for differences between nadir and glint measurements, and the associated scene-dependent observation errors. We show that OCO XCO2 measurements significantly reduce the uncertainties of surface CO2 flux estimates. Glint measurements are generally better at constraining ocean CO2 flux estimates. Nadir XCO2 measurements over the terrestrial tropics are sparse throughout the year because of either clouds or smoke. Glint measurements provide the most effective constraint for estimating tropical terrestrial CO2 fluxes by accurately sampling fresh continental outflow over neighbouring oceans. We also present results from sensitivity experiments that investigate how flux estimates change with 1 bias and unbiased errors, 2 alternative duty cycles, 3 measurement density and correlations, 4 the spatial resolution of estimated flux estimates, and 5 reducing the length of the lag window and the

  9. Revisiting the paper “Using radiometric surface temperature for surface energy flux estimation in Mediterranean drylands from a two-source perspective”

    DEFF Research Database (Denmark)

    Kustas, William P.; Nieto, Hector; Morillas, Laura

    2016-01-01

    The recent paper by Morillas et al. [Morillas, L. et al. Using radiometric surface temperature for surface energy flux estimation in Mediterranean drylands from a two-source perspective, Remote Sens. Environ. 136, 234–246, 2013] evaluates the two-source model (TSM) of Norman et al. (1995) with re......The recent paper by Morillas et al. [Morillas, L. et al. Using radiometric surface temperature for surface energy flux estimation in Mediterranean drylands from a two-source perspective, Remote Sens. Environ. 136, 234–246, 2013] evaluates the two-source model (TSM) of Norman et al. (1995......) with revisions by Kustas and Norman (1999) over a semiarid tussock grassland site in southeastern Spain. The TSM - in its current incarnation, the two-source energy balance model (TSEB) - was applied to this landscape using ground-based infrared radiometer sensors to estimate both the composite surface...... greenness and local leaf area index values as well as modifications to the coefficients of the soil resistance formulation to account for the very rough (rocky) soil surface conditions with a clumped canopy. This indicates that both limitations in remote estimates of biophysical indicators of the canopy...

  10. Regional CO2 and latent heat surface fluxes in the Southern Great Plains: Measurements, modeling, and scaling

    Energy Technology Data Exchange (ETDEWEB)

    Riley, W. J.; Biraud, S.C.; Torn, M.S.; Fischer, M.L.; Billesbach, D.P.; Berry, J.A.

    2009-08-15

    Characterizing net ecosystem exchanges (NEE) of CO{sub 2} and sensible and latent heat fluxes in heterogeneous landscapes is difficult, yet critical given expected changes in climate and land use. We report here a measurement and modeling study designed to improve our understanding of surface to atmosphere gas exchanges under very heterogeneous land cover in the mostly agricultural U.S. Southern Great Plains (SGP). We combined three years of site-level, eddy covariance measurements in several of the dominant land cover types with regional-scale climate data from the distributed Mesonet stations and Next Generation Weather Radar precipitation measurements to calibrate a land surface model of trace gas and energy exchanges (isotope-enabled land surface model (ISOLSM)). Yearly variations in vegetation cover distributions were estimated from Moderate Resolution Imaging Spectroradiometer normalized difference vegetation index and compared to regional and subregional vegetation cover type estimates from the U.S. Department of Agriculture census. We first applied ISOLSM at a 250 m spatial scale to account for vegetation cover type and leaf area variations that occur on hundred meter scales. Because of computational constraints, we developed a subsampling scheme within 10 km 'macrocells' to perform these high-resolution simulations. We estimate that the Atmospheric Radiation Measurement Climate Research Facility SGP region net CO{sub 2} exchange with the local atmosphere was -240, -340, and -270 gC m{sup -2} yr{sup -1} (positive toward the atmosphere) in 2003, 2004, and 2005, respectively, with large seasonal variations. We also performed simulations using two scaling approaches at resolutions of 10, 30, 60, and 90 km. The scaling approach applied in current land surface models led to regional NEE biases of up to 50 and 20% in weekly and annual estimates, respectively. An important factor in causing these biases was the complex leaf area index (LAI) distribution

  11. Sea ice-atmospheric interaction: Application of multispectral satellite data in polar surface energy flux estimates

    Science.gov (United States)

    Steffen, Konrad; Key, J.; Maslanik, J.; Schweiger, A.

    1993-01-01

    This is the third annual report on: Sea Ice-Atmosphere Interaction - Application of Multispectral Satellite Data in Polar Surface Energy Flux Estimates. The main emphasis during the past year was on: radiative flux estimates from satellite data; intercomparison of satellite and ground-based cloud amounts; radiative cloud forcing; calibration of the Advanced Very High Resolution Radiometer (AVHRR) visible channels and comparison of two satellite derived albedo data sets; and on flux modeling for leads. Major topics covered are arctic clouds and radiation; snow and ice albedo, and leads and modeling.

  12. Surface-Air Mercury Fluxes Across Western North America: A Synthesis of Spatial Trends and Controlling Variables.

    Science.gov (United States)

    Eckley, C.; Tate, M.; Lin, C. J.; Gustin, M. S.; Dent, S.; Eagles-Smith, C.; Lutz, M.; Wickland, K.; Wang, B.; Gray, J.; Edwards, G. C.; Krabbenhoft, D. P.; Smith, D. B.

    2016-12-01

    Mercury (Hg) emission and deposition can occur to and from soils and are an important component of the global atmospheric Hg budget. This presentation focuses on synthesizing existing surface-air Hg flux data collected throughout the Western North American region and is part of a series of geographically focused Hg synthesis projects. A database of existing Hg flux data collected using the dynamic flux chamber (DFC) approach from almost a thousand locations was created for the Western North America region. Statistical analysis was performed on the data to identify the important variables controlling Hg fluxes and to allow spatiotemporal scaling. The results indicated that most of the variability in soil-air Hg fluxes could be explained by variations in soil-Hg concentrations, solar radiation, and soil moisture. This analysis also identified that variations in DFC methodological approaches were detectable among the field studies, with the chamber material and sampling flushing flow rate influencing the magnitude of calculated emissions. The spatiotemporal scaling of soil-air Hg fluxes identified that the largest emissions occurred from irrigated agricultural landscapes in California. Vegetation was shown to have a large impact on surface-air Hg fluxes due to both a reduction in solar radiation reaching the soil as well as from direct uptake of Hg in foliage. Despite high soil Hg emissions from some forested and other heavily vegetated regions, the net ecosystem flux (soil flux + vegetation uptake) was low. Conversely, sparsely vegetated regions showed larger net ecosystem emissions, which were similar in magnitude to atmospheric Hg deposition (except for the Mediterranean California region where soil emissions were higher). The net ecosystem flux results highlight the important role of landscape characteristics in effecting the balance between Hg sequestration and (re-)emission to the atmosphere.

  13. Surface-air mercury fluxes across Western North America: A synthesis of spatial trends and controlling variables

    Science.gov (United States)

    Eckley, Chris S.; Tate, Michael T.; Lin, Che-Jen; Gustin, Mae S.; Dent, Stephen; Eagles-Smith, Collin A.; Lutz, Michelle A; Wickland, Kimberly; Wang, Bronwen; Gray, John E.; Edwards, Grant; Krabbenhoft, David P.; Smith, David

    2016-01-01

    Mercury (Hg) emission and deposition can occur to and from soils, and are an important component of the global atmospheric Hg budget. This paper focuses on synthesizing existing surface-air Hg flux data collected throughout the Western North American region and is part of a series of geographically focused Hg synthesis projects. A database of existing Hg flux data collected using the dynamic flux chamber (DFC) approach from almost a thousand locations was created for the Western North America region. Statistical analysis was performed on the data to identify the important variables controlling Hg fluxes and to allow spatiotemporal scaling. The results indicated that most of the variability in soil-air Hg fluxes could be explained by variations in soil-Hg concentrations, solar radiation, and soil moisture. This analysis also identified that variations in DFC methodological approaches were detectable among the field studies, with the chamber material and sampling flushing flow rate influencing the magnitude of calculated emissions. The spatiotemporal scaling of soil-air Hg fluxes identified that the largest emissions occurred from irrigated agricultural landscapes in California. Vegetation was shown to have a large impact on surface-air Hg fluxes due to both a reduction in solar radiation reaching the soil as well as from direct uptake of Hg in foliage. Despite high soil Hg emissions from some forested and other heavily vegetated regions, the net ecosystem flux (soil flux + vegetation uptake) was low. Conversely, sparsely vegetated regions showed larger net ecosystem emissions, which were similar in magnitude to atmospheric Hg deposition (except for the Mediterranean California region where soil emissions were higher). The net ecosystem flux results highlight the important role of landscape characteristics in effecting the balance between Hg sequestration and (re-)emission to the atmosphere.

  14. Surface renewal: an advanced micrometeorological method for measuring and processing field-scale energy flux density data.

    Science.gov (United States)

    McElrone, Andrew J; Shapland, Thomas M; Calderon, Arturo; Fitzmaurice, Li; Paw U, Kyaw Tha; Snyder, Richard L

    2013-12-12

    Advanced micrometeorological methods have become increasingly important in soil, crop, and environmental sciences. For many scientists without formal training in atmospheric science, these techniques are relatively inaccessible. Surface renewal and other flux measurement methods require an understanding of boundary layer meteorology and extensive training in instrumentation and multiple data management programs. To improve accessibility of these techniques, we describe the underlying theory of surface renewal measurements, demonstrate how to set up a field station for surface renewal with eddy covariance calibration, and utilize our open-source turnkey data logger program to perform flux data acquisition and processing. The new turnkey program returns to the user a simple data table with the corrected fluxes and quality control parameters, and eliminates the need for researchers to shuttle between multiple processing programs to obtain the final flux data. An example of data generated from these measurements demonstrates how crop water use is measured with this technique. The output information is useful to growers for making irrigation decisions in a variety of agricultural ecosystems. These stations are currently deployed in numerous field experiments by researchers in our group and the California Department of Water Resources in the following crops: rice, wine and raisin grape vineyards, alfalfa, almond, walnut, peach, lemon, avocado, and corn.

  15. Sub-surface microstructure of single and polycrystalline tungsten after high flux plasma exposure studied by TEM

    Energy Technology Data Exchange (ETDEWEB)

    Dubinko, A., E-mail: adubinko@sckcen.be [Institute for Nuclear Material Sciences, SCK-CEN, 2400 Mol (Belgium); Department of Applied Physics, Ghent University, 9000 Ghent (Belgium); Terentyev, D. [Institute for Nuclear Material Sciences, SCK-CEN, 2400 Mol (Belgium); Bakaeva, A. [Institute for Nuclear Material Sciences, SCK-CEN, 2400 Mol (Belgium); Department of Applied Physics, Ghent University, 9000 Ghent (Belgium); Hernández-Mayoral, M. [Division of Materials, CIEMAT, 28040 Madrid (Spain); De Temmerman, G. [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St Paul-lez-Durance Cedex (France); Buzi, L. [Forschungszentrum Julich, Inst. Energie & Klimaforsch Plasmaphys, D-52425 Julich (Germany); Noterdaeme, J.-M. [Department of Applied Physics, Ghent University, 9000 Ghent (Belgium); Unterberg, B. [Forschungszentrum Julich, Inst. Energie & Klimaforsch Plasmaphys, D-52425 Julich (Germany)

    2017-01-30

    Highlights: • Plasma exposure induces dislocation-dominated microstructure as indicated by TEM. • Plasma exposure increases surface dislocation density by an order of magnitude in the polycrystalline tungsten. • Intensive dislocation-grain boundary interaction observed in polycrystalline tungsten. • Dislocation loops are observed in both polycrystalline and single crystal tungsten. - Abstract: We have performed high flux plasma exposure of tungsten and subsequent microstructural characterization using transmission electron microscopy (TEM) techniques. The aim was to reveal the nanometric features in the sub-surface region as well as to compare the microstructural evolution in tungsten single crystal and ITER-relevant specification. In both types of samples, TEM examination revealed the formation of a dense dislocation network and dislocation tangles. The estimated dislocation density in the sub-surface region was of the order of 10{sup 14} m{sup −2} and it gradually decreased with a depth position of the examined sample. Besides individual dislocation lines, networks and tangles, the interstitial dislocation loops have been observed in all examined samples only after the exposure. Contrary to that, examination of the pristine single crystal W and backside of the plasma-exposed samples did not reveal the presence of dislocation loops and tangles. This clearly proves that high flux plasma exposure induces severe plastic deformation in the sub-surface region irrespective of the presence of initial dislocations and sub-grains, and the formation of dislocation tangles, networks and interstitial loops is a co-product of thermal stress and intensive plasma particles uptake.

  16. The Global Energy Balance Archive (GEBA): A database for the worldwide measured surface energy fluxes

    Science.gov (United States)

    Wild, Martin; Ohmura, Atsumu; Schär, Christoph; Müller, Guido; Hakuba, Maria Z.; Mystakidis, Stefanos; Arsenovic, Pavle; Sanchez-Lorenzo, Arturo

    2017-02-01

    The Global Energy Balance Archive (GEBA) is a database for the worldwide measured energy fluxes at the Earth's surface. GEBA is maintained at ETH Zurich (Switzerland) and has been founded in the 1980s by Prof. Atsumu Ohmura. It has continuously been updated and currently contains around 2500 stations with 500`000 monthly mean entries of various surface energy balance components. Many of the records extend over several decades. The most widely measured quantity available in GEBA is the solar radiation incident at the Earth's surface ("global radiation"). The data sources include, in addition to the World Radiation Data Centre (WRDC) in St. Petersburg, data reports from National Weather Services, data from different research networks (BSRN, ARM, SURFRAD), data published in peer-reviewed publications and data obtained through personal communications. Different quality checks are applied to check for gross errors in the dataset. GEBA is used in various research applications, such as for the quantification of the global energy balance and its spatiotemporal variation, or for the estimation of long-term trends in the surface fluxes, which enabled the detection of multi-decadal variations in surface solar radiation, known as "global dimming" and "brightening". GEBA is further extensively used for the evaluation of climate models and satellite-derived surface flux products. On a more applied level, GEBA provides the basis for engineering applications in the context of solar power generation, water management, agricultural production and tourism. GEBA is publicly accessible over the internet via www.geba.ethz.ch.

  17. An Integrated Approach to Estimate Instantaneous Near-Surface Air Temperature and Sensible Heat Flux Fields during the SEMAPHORE Experiment.

    Science.gov (United States)

    Bourras, Denis; Eymard, Laurence; Liu, W. Timothy; Dupuis, Hélène

    2002-03-01

    A new technique was developed to retrieve near-surface instantaneous air temperatures and turbulent sensible heat fluxes using satellite data during the Structure des Echanges Mer-Atmosphere, Proprietes des Heterogeneites Oceaniques: Recherche Experimentale (SEMAPHORE) experiment, which was conducted in 1993 under mainly anticyclonic conditions. The method is based on a regional, horizontal atmospheric temperature advection model whose inputs are wind vectors, sea surface temperature fields, air temperatures around the region under study, and several constants derived from in situ measurements. The intrinsic rms error of the method is 0.7°C in terms of air temperature and 9 W m2 for the fluxes, both at 0.16° × 0.16° and 1.125° × 1.125° resolution. The retrieved air temperature and flux horizontal structures are in good agreement with fields from two operational general circulation models. The application to SEMAPHORE data involves the First European Remote Sensing Satellite (ERS-1) wind fields, Advanced Very High Resolution Radiometer (AVHRR) SST fields, and European Centre for Medium-Range Weather Forecasts (ECMWF) air temperature boundary conditions. The rms errors obtained by comparing the estimations with research vessel measurements are 0.3°C and 5 W m2.

  18. Surface-air mercury fluxes across Western North America: A synthesis of spatial trends and controlling variables

    Energy Technology Data Exchange (ETDEWEB)

    Eckley, Chris S., E-mail: eckley.chris@epa.gov [US Environmental Protection Agency, Region-10, Seattle, WA 98101 (United States); Tate, Mike T. [US Geological Survey, Middleton, WI 53562 (United States); Lin, Che-Jen [Center for Advances on Water and Air quality, Lamar University, Beaumont, TX 77710 (United States); Gustin, Mae [Department of Natural Resources & Environmental Science, University of Nevada, Reno, NV 89557 (United States); Dent, Stephen [CDM Smith, Portland, OR 97205 (United States); Eagles-Smith, Collin [US Geological Survey, Corvallis, OR 97331 (United States); Lutz, Michelle A. [US Geological Survey, Middleton, WI 53562 (United States); Wickland, Kimberly P. [US Geological Survey Boulder, CO 80303 (United States); Wang, Bronwen [US Geological Survey, Anchorage, AK 99508 (United States); Gray, John E. [US Geological Survey, Denver, CO 80225 (United States); Edwards, Grant C. [Department of Environment and Geography, Macquarie University, North Ryde, NSW 2109 (Australia); Krabbenhoft, Dave P. [US Geological Survey, Middleton, WI 53562 (United States); Smith, David B. [US Geological Survey, Denver, CO 80225 (United States)

    2016-10-15

    Mercury (Hg) emission and deposition can occur to and from soils, and are an important component of the global atmospheric Hg budget. This paper focuses on synthesizing existing surface-air Hg flux data collected throughout the Western North American region and is part of a series of geographically focused Hg synthesis projects. A database of existing Hg flux data collected using the dynamic flux chamber (DFC) approach from almost a thousand locations was created for the Western North America region. Statistical analysis was performed on the data to identify the important variables controlling Hg fluxes and to allow spatiotemporal scaling. The results indicated that most of the variability in soil-air Hg fluxes could be explained by variations in soil-Hg concentrations, solar radiation, and soil moisture. This analysis also identified that variations in DFC methodological approaches were detectable among the field studies, with the chamber material and sampling flushing flow rate influencing the magnitude of calculated emissions. The spatiotemporal scaling of soil-air Hg fluxes identified that the largest emissions occurred from irrigated agricultural landscapes in California. Vegetation was shown to have a large impact on surface-air Hg fluxes due to both a reduction in solar radiation reaching the soil as well as from direct uptake of Hg in foliage. Despite high soil Hg emissions from some forested and other heavily vegetated regions, the net ecosystem flux (soil flux + vegetation uptake) was low. Conversely, sparsely vegetated regions showed larger net ecosystem emissions, which were similar in magnitude to atmospheric Hg deposition (except for the Mediterranean California region where soil emissions were higher). The net ecosystem flux results highlight the important role of landscape characteristics in effecting the balance between Hg sequestration and (re-)emission to the atmosphere. - Highlights: • Soil-air Hg fluxes are an important component of the

  19. Surface-air mercury fluxes across Western North America: A synthesis of spatial trends and controlling variables

    International Nuclear Information System (INIS)

    Eckley, Chris S.; Tate, Mike T.; Lin, Che-Jen; Gustin, Mae; Dent, Stephen; Eagles-Smith, Collin; Lutz, Michelle A.; Wickland, Kimberly P.; Wang, Bronwen; Gray, John E.; Edwards, Grant C.; Krabbenhoft, Dave P.; Smith, David B.

    2016-01-01

    Mercury (Hg) emission and deposition can occur to and from soils, and are an important component of the global atmospheric Hg budget. This paper focuses on synthesizing existing surface-air Hg flux data collected throughout the Western North American region and is part of a series of geographically focused Hg synthesis projects. A database of existing Hg flux data collected using the dynamic flux chamber (DFC) approach from almost a thousand locations was created for the Western North America region. Statistical analysis was performed on the data to identify the important variables controlling Hg fluxes and to allow spatiotemporal scaling. The results indicated that most of the variability in soil-air Hg fluxes could be explained by variations in soil-Hg concentrations, solar radiation, and soil moisture. This analysis also identified that variations in DFC methodological approaches were detectable among the field studies, with the chamber material and sampling flushing flow rate influencing the magnitude of calculated emissions. The spatiotemporal scaling of soil-air Hg fluxes identified that the largest emissions occurred from irrigated agricultural landscapes in California. Vegetation was shown to have a large impact on surface-air Hg fluxes due to both a reduction in solar radiation reaching the soil as well as from direct uptake of Hg in foliage. Despite high soil Hg emissions from some forested and other heavily vegetated regions, the net ecosystem flux (soil flux + vegetation uptake) was low. Conversely, sparsely vegetated regions showed larger net ecosystem emissions, which were similar in magnitude to atmospheric Hg deposition (except for the Mediterranean California region where soil emissions were higher). The net ecosystem flux results highlight the important role of landscape characteristics in effecting the balance between Hg sequestration and (re-)emission to the atmosphere. - Highlights: • Soil-air Hg fluxes are an important component of the

  20. Downwelling Longwave Fluxes at Continental Surfaces-A Comparison of Observations with GCM Simulations and Implications for the Global Land-Surface Radiation Budget.

    Science.gov (United States)

    Garratt, J. R.; Prata, A. J.

    1996-03-01

    Previous work suggests that general circulation (global climate) models have excess net radiation at land surfaces, apparently due to overestimates in downwelling shortwave flux and underestimates in upwelling long-wave flux. Part of this excess, however, may be compensated for by an underestimate in downwelling longwave flux. Long term observations of the downwelling longwave component at several land stations in Europe, the United States, Australia, and Antarctica suggest that climate models (four are used, as in previous studies) underestimate this flux component on an annual basis by up to 10 W m2, yet with low statistical significance. It is probable that the known underestimate in boundary-layer air temperature contributes to this, as would low model cloudiness and neglect of minor gases such as methane, nitrogen oxide, and the freons. The bias in downwelling longwave flux, together with those found earlier for downwelling shortwave and upwlling long-wave fluxes, are consistent with the model bias found previously for net radiation. All annually averaged fluxes and biases are deduced for global land as a whole.

  1. The advantages, and challenges, in using multiple techniques in the estimation of surface water-groundwater fluxes.

    Science.gov (United States)

    Shanafield, M.; Cook, P. G.

    2014-12-01

    When estimating surface water-groundwater fluxes, the use of complimentary techniques helps to fill in uncertainties in any individual method, and to potentially gain a better understanding of spatial and temporal variability in a system. It can also be a way of preventing the loss of data during infrequent and unpredictable flow events. For example, much of arid Australia relies on groundwater, which is recharged by streamflow through ephemeral streams during flood events. Three recent surface water/groundwater investigations from arid Australian systems provide good examples of how using multiple field and analysis techniques can help to more fully characterize surface water-groundwater fluxes, but can also result in conflicting values over varying spatial and temporal scales. In the Pilbara region of Western Australia, combining streambed radon measurements, vertical heat transport modeling, and a tracer test helped constrain very low streambed residence times, which are on the order of minutes. Spatial and temporal variability between the methods yielded hyporheic exchange estimates between 10-4 m2 s-1 and 4.2 x 10-2 m2 s-1. In South Australia, three-dimensional heat transport modeling captured heterogeneity within 20 square meters of streambed, identifying areas of sandy soil (flux rates of up to 3 m d-1) and clay (flux rates too slow to be accurately characterized). Streamflow front modeling showed similar flux rates, but averaged over 100 m long stream segments for a 1.6 km reach. Finally, in central Australia, several methods are used to decipher whether any of the flow down a highly ephemeral river contributes to regional groundwater recharge, showing that evaporation and evapotranspiration likely accounts for all of the infiltration into the perched aquifer. Lessons learned from these examples demonstrate the influences of the spatial and temporal variability between techniques on estimated fluxes.

  2. Reconstructing solar magnetic fields from historical observations. II. Testing the surface flux transport model

    Science.gov (United States)

    Virtanen, I. O. I.; Virtanen, I. I.; Pevtsov, A. A.; Yeates, A.; Mursula, K.

    2017-07-01

    Aims: We aim to use the surface flux transport model to simulate the long-term evolution of the photospheric magnetic field from historical observations. In this work we study the accuracy of the model and its sensitivity to uncertainties in its main parameters and the input data. Methods: We tested the model by running simulations with different values of meridional circulation and supergranular diffusion parameters, and studied how the flux distribution inside active regions and the initial magnetic field affected the simulation. We compared the results to assess how sensitive the simulation is to uncertainties in meridional circulation speed, supergranular diffusion, and input data. We also compared the simulated magnetic field with observations. Results: We find that there is generally good agreement between simulations and observations. Although the model is not capable of replicating fine details of the magnetic field, the long-term evolution of the polar field is very similar in simulations and observations. Simulations typically yield a smoother evolution of polar fields than observations, which often include artificial variations due to observational limitations. We also find that the simulated field is fairly insensitive to uncertainties in model parameters or the input data. Due to the decay term included in the model the effects of the uncertainties are somewhat minor or temporary, lasting typically one solar cycle.

  3. Thin Film Heat Flux Sensors: Design and Methodology

    Science.gov (United States)

    Fralick, Gustave C.; Wrbanek, John D.

    2013-01-01

    Thin Film Heat Flux Sensors: Design and Methodology: (1) Heat flux is one of a number of parameters, together with pressure, temperature, flow, etc. of interest to engine designers and fluid dynamists, (2) The measurement of heat flux is of interest in directly determining the cooling requirements of hot section blades and vanes, and (3)In addition, if the surface and gas temperatures are known, the measurement of heat flux provides a value for the convective heat transfer coefficient that can be compared with the value provided by CFD codes.

  4. Surface Turbulent Fluxes, 1x1 deg Daily Grid, Set1 V2c

    Data.gov (United States)

    National Aeronautics and Space Administration — These data are the Goddard Satellite-based Surface Turbulent Fluxes Version-2c (GSSTF2c) Dataset recently produced through a MEaSUREs funded project led by Dr....

  5. Thermal wave propagation in blood perfused tissues under hyperthermia treatment for unique oscillatory heat flux at skin surface and appropriate initial condition

    Science.gov (United States)

    Dutta, Jaideep; Kundu, Balaram

    2018-05-01

    This paper aims to develop an analytical study of heat propagation in biological tissues for constant and variable heat flux at the skin surface correlated with Hyperthermia treatment. In the present research work we have attempted to impose two unique kind of oscillating boundary condition relevant to practical aspect of the biomedical engineering while the initial condition is constructed as spatially dependent according to a real life situation. We have implemented Laplace's Transform method (LTM) and Green Function (GFs) method to solve single phase lag (SPL) thermal wave model of bioheat equation (TWMBHE). This research work strongly focuses upon the non-invasive therapy by employing oscillating heat flux. The heat flux at the skin surface is considered as constant, sinusoidal, and cosine forms. A comparative study of the impact of different kinds of heat flux on the temperature field in living tissue explored that sinusoidal heat flux will be more effective if the time of therapeutic heating is high. Cosine heating is also applicable in Hyperthermia treatment due to its precision in thermal waveform. The result also emphasizes that accurate observation must be required for the selection of phase angle and frequency of oscillating heat flux. By possible comparison with the published experimental research work and published mathematical study we have experienced a difference in temperature distribution as 5.33% and 4.73%, respectively. A parametric analysis has been devoted to suggest an appropriate procedure of the selection of important design variables in viewpoint of an effective heating in hyperthermia treatment.

  6. Surface wettability effects on critical heat flux of boiling heat transfer using nanoparticle coatings

    KAUST Repository

    Hsu, Chin-Chi

    2012-06-01

    This study investigates the effects of surface wettability on pool boiling heat transfer. Nano-silica particle coatings were used to vary the wettability of the copper surface from superhydrophilic to superhydrophobic by modifying surface topography and chemistry. Experimental results show that critical heat flux (CHF) values are higher in the hydrophilic region. Conversely, CHF values are lower in the hydrophobic region. The experimental CHF data of the modified surface do not fit the classical models. Therefore, this study proposes a simple model to build the nexus between the surface wettability and the growth of bubbles on the heating surface. © 2012 Elsevier Ltd. All rights reserved.

  7. Operational tools and applications of EO satellite data to retrieve surface fluxes in semi-arid countries

    Science.gov (United States)

    Tanguy, Maliko

    The objective of the thesis is to develop and evaluate useful tools and applications of Earth Observation (EO) satellite data to estimate surface fluxes in semi-arid countries. In a first part (Chapter 4), we assess the performance of a new parameterisation scheme of ground heat flux (G) to be used in remote sensing (RS) evapotranspiration (ET) estimation methods. The G-parameterisation optimized with AMMA flux data performs well and improves the sensible heat flux (H) and ET retrieved by means of the triangle method (Jiang & Islam, 2001). In a second part (Chapter 5), the triangle method is compared with ET estimated by means of a land surface model (JULES). An attempt is made to calibrate JULES using the triangle method through Monte Carlo simulations, but the two methods supply rather different results, indicating that further intercomparison tasks should be carried out to assess the performance of RS-based algorithms and land surface models in estimating the components of the land surface energy balance. Chapter 6 presents a set of operational examples for retrieving surface fluxes using RS data. The first example is the study of temporal evolution of ET-maps in Western Africa under monsoonal influence. In a second example, we apply the new scheme proposed in Chapter 4 to retrieve and analyse the long term evolution (2000-2009) of the surface energy balance components, G, H and ET at several sites of the Segura Basin (S-E Spain) using MODIS-Terra data (land surface temperature and NDVI). Temporal and spatial distribution of evapotranspiration reveals different controls on ET. (Chapter 6). In the last example, MODIS-Aqua Sea Surface Temperature (SST) is used to validate a mathematical model to retrieve surface fluxes in a Mediterranean coastal lagoon (Mar Menor, S-E Spain). El objetivo de esta tesis es de desarrollar y evaluar herramientas y aplicaciones de la teledetección para estimar flujos de superficie en zonas semiáridas. En una primera parte (Cap

  8. High-flux He+ irradiation effects on surface damages of tungsten under ITER relevant conditions

    International Nuclear Information System (INIS)

    Liu, Lu; Liu, Dongping; Hong, Yi; Fan, Hongyu; Ni, Weiyuan; Yang, Qi; Bi, Zhenhua; Benstetter, Günther; Li, Shouzhe

    2016-01-01

    A large-power inductively coupled plasma source was designed to perform the continuous helium ions (He + ) irradiations of polycrystalline tungsten (W) under International Thermonuclear Experimental Reactor (ITER) relevant conditions. He + irradiations were performed at He + fluxes of 2.3 × 10 21 –1.6 × 10 22 /m 2  s and He + energies of 12–220 eV. Surface damages and microstructures of irradiated W were observed by scanning electron microscopy. This study showed the growth of nano-fuzzes with their lengths of 1.3–2.0 μm at He + energies of >70 eV or He + fluxes of >1.3 × 10 22 /m 2  s. Nanometer-sized defects or columnar microstructures were formed in W surface layer due to low-energy He + irradiations at an elevated temperature (>1300 K). The diffusion and coalescence of He atoms in W surface layers led to the growth and structures of nano-fuzzes. This study indicated that a reduction of He + energy below 12–30 eV may greatly decrease the surface damage of tungsten diverter in the fusion reactor.

  9. Flux measurement of methanol, acetaldehyde and other oxygenated VOCs from crop harvesting using proton-transfer-reaction mass spectrometry and surface layer gradient method

    International Nuclear Information System (INIS)

    Lindinger, C.; Jordan, A.; Karl, T.; Guenther, A.; Tschiersch, J.; Ruckerbauer, F.; Paretzke, H.

    2002-01-01

    PTR-MS technique was used to measure fluxes of various VOC's including oxygenates using surface layer gradient method. The VOC concentrations and temperature were measured at heights of about 0.5 m and 3.9 m above ground at field site in St. Johann in Tirol during and after grass cutting (24th and 25th of May 2000) in order to calculate fluxes. The sensible heat flux was obtained by a sonic anemometer with turbulence data analyzer. The major crop in this part of Austria are perennial grasses used for livestock farming. We observed VOC emission fluxes including methanol and acetaldehyde as the major volatile, C 5 and C 6 leaf wound compounds with lesser amounts and traces of acetone and butanone. This composition of VOC's is very similar to that released from slashed pasture grass. At the same time, VOC fluxes were measured with PTR-MS and eddy covariance method. Comparing the flux data of methanol and acetaldehyde of both days have shown very similar results. (author)

  10. Surface flux density distribution characteristics of bulk high-T{sub c} superconductor in external magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Torii, S.; Yuasa, K

    2004-10-01

    Various magnetic levitation systems using oxide superconductors are developed as strong pinning forces are obtained in melt-processed bulk. However, the trapped flux of superconductor is moved by flux creep and fluctuating magnetic field. Therefore, to examine the internal condition of superconductor, the authors measure the dynamic surface flux density distribution of YBCO bulk. Flux density measurement system has a structure with the air-core coil and the Hall sensors. Ten Hall sensors are arranged in series. The YBCO bulk, which has 25 mm diameter and 13 mm thickness, is field cooled by liquid nitrogen. After that, magnetic field is changed by the air-core coil. This paper describes about the measured results of flux density distribution of YBCO bulk in the various frequencies of air-core coils currents.

  11. Use of Germanium as comparator and integral monitor of neutron flux in activation analysis

    International Nuclear Information System (INIS)

    Furnari, Juan C.; Cohen, Isaac M.; Arribere, Maria A.; Kestelman, Abraham J.

    1997-01-01

    The possibility of using germanium as monitor of the thermal and epithermal components of the neutron flux, and comparator in parametric activation analysis, is discussed. The advantages and drawbacks associated to the use of this element are commented on, and the comparison with zirconium, in terms of the determination relative error, is performed. The utilisation of germanium as integral flux monitor, including the fast component of the neutron spectrum, is also discussed. Data corresponding to measurements of k 0 factor for the most relevant gamma transitions from Ge-75 and Be-77 are presented, as well as the results of the reference material analysis, employing germanium as flux monitor and comparator in a simultaneous way. (author). 8 refs., 3 figs., 2 tabs

  12. Surface flux transport simulations: Effect of inflows toward active regions and random velocities on the evolution of the Sun's large-scale magnetic field

    Science.gov (United States)

    Martin-Belda, D.; Cameron, R. H.

    2016-02-01

    Aims: We aim to determine the effect of converging flows on the evolution of a bipolar magnetic region (BMR), and to investigate the role of these inflows in the generation of poloidal flux. We also discuss whether the flux dispersal due to turbulent flows can be described as a diffusion process. Methods: We developed a simple surface flux transport model based on point-like magnetic concentrations. We tracked the tilt angle, the magnetic flux and the axial dipole moment of a BMR in simulations with and without inflows and compared the results. To test the diffusion approximation, simulations of random walk dispersal of magnetic features were compared against the predictions of the diffusion treatment. Results: We confirm the validity of the diffusion approximation to describe flux dispersal on large scales. We find that the inflows enhance flux cancellation, but at the same time affect the latitudinal separation of the polarities of the bipolar region. In most cases the latitudinal separation is limited by the inflows, resulting in a reduction of the axial dipole moment of the BMR. However, when the initial tilt angle of the BMR is small, the inflows produce an increase in latitudinal separation that leads to an increase in the axial dipole moment in spite of the enhanced flux destruction. This can give rise to a tilt of the BMR even when the BMR was originally aligned parallel to the equator.

  13. Surface damages of polycrystalline W and La2O3-doped W induced by high-flux He plasma irradiation

    Science.gov (United States)

    Liu, Lu; Li, Shouzhe; Liu, Dongping; Benstetter, Günther; Zhang, Yang; Hong, Yi; Fan, Hongyu; Ni, Weiyuan; Yang, Qi; Wu, Yunfeng; Bi, Zhenhua

    2018-04-01

    In this study, polycrystalline tungsten (W) and three oxide dispersed strengthened W with 0.1 vol %, 1.0 vol % and 5.0 vol % lanthanum trioxide (La2O3) were irradiated with low-energy (200 eV) and high-flux (5.8 × 1021 or 1.4 × 1022 ions/m2ṡs) He+ ions at elevated temperature. After He+ irradiation at a fluence of 3.0 × 1025/m2, their surface damages were observed by scanning electron microscopy, energy dispersive spectroscopy, scanning electron microscopy-electron backscatter diffraction, and conductive atomic force microscopy. Micron-sized holes were formed on the surface of W alloys after He+ irradiation at 1100 K. Analysis shows that the La2O3 grains doped in W were sputtered preferentially by the high-flux He+ ions when compared with the W grains. For irradiation at 1550 K, W nano-fuzz was formed at the surfaces of both polycrystalline W and La2O3-doped W. The thickness of the fuzz layers formed at the surface of La2O3-doped W is 40% lower than the one of polycrystalline W. The presence of La2O3 could suppress the diffusion and coalescence of He atoms inside W, which plays an important role in the growth of nanostructures fuzz.

  14. Flux-driven turbulence GDB simulations of the IWL Alcator C-Mod L-mode edge compared with experiment

    Science.gov (United States)

    Francisquez, Manaure; Zhu, Ben; Rogers, Barrett

    2017-10-01

    Prior to predicting confinement regime transitions in tokamaks one may need an accurate description of L-mode profiles and turbulence properties. These features determine the heat-flux width upon which wall integrity depends, a topic of major interest for research aid to ITER. To this end our work uses the GDB model to simulate the Alcator C-Mod edge and contributes support for its use in studying critical edge phenomena in current and future tokamaks. We carried out 3D electromagnetic flux-driven two-fluid turbulence simulations of inner wall limited (IWL) C-Mod shots spanning closed and open flux surfaces. These simulations are compared with gas puff imaging (GPI) and mirror Langmuir probe (MLP) data, examining global features and statistical properties of turbulent dynamics. GDB reproduces important qualitative aspects of the C-Mod edge regarding global density and temperature profiles, within reasonable margins, and though the turbulence statistics of the simulated turbulence follow similar quantitative trends questions remain about the code's difficulty in exactly predicting quantities like the autocorrelation time A proposed breakpoint in the near SOL pressure and the posited separation between drift and ballooning dynamics it represents are examined This work was supported by DOE-SC-0010508. This research used resources of the National Energy Research Scientific Computing Center (NERSC).

  15. Dry deposition fluxes and deposition velocities of trace metals in the Tokyo metropolitan area measured with a water surface sampler.

    Science.gov (United States)

    Sakata, Masahiro; Marumoto, Kohji

    2004-04-01

    Dry deposition fluxes and deposition velocities (=deposition flux/atmospheric concentration) for trace metals including Hg, Cd, Cu, Mn, Pb, and Zn in the Tokyo metropolitan area were measured using an improved water surface sampler. Mercury is deposited on the water surface in both gaseous (reactive gaseous mercury, RGM) and particulate (particulate mercury, Hg(p)) forms. The results based on 1 yr observations found that dry deposition plays a significant if not dominant role in trace metal deposition in this urban area, contributing fluxes ranging from 0.46 (Cd) to 3.0 (Zn) times those of concurrent wet deposition fluxes. The deposition velocities were found to be dependent on the deposition of coarse particles larger than approximately 5 microm in diameter on the basis of model calculations. Our analysis suggests that the 84.13% diameter is a more appropriate index for each deposited metal than the 50% diameter in the assumed undersize log-normal distribution, because larger particles are responsible for the flux. The deposition velocities for trace metals other than mercury increased exponentially with an increase in their 84.13% diameters. Using this regression equation, the deposition velocities for Hg(p) were estimated from its 84.13% diameter. The deposition fluxes for Hg(p) calculated from the estimated velocities tended to be close to the mercury fluxes measured with the water surface sampler during the study periods except during summer.

  16. Tests of a robust eddy correlation system for sensible heat flux

    Science.gov (United States)

    Blanford, J. H.; Gay, L. W.

    1992-03-01

    Sensible heat flux estimates from a simple, one-propeller eddy correlation system (OPEC) were compared with those from a sonic anemometer eddy correlation system (SEC). In accordance with similarity theory, the performance of the OPEC system improved with increasing height of the sensor above the surface. Flux totals from the two systems at sites with adequate fetch were in excellent agreement after frequency response corrections were applied. The propeller system appears suitable for long periods of unattended measurement. The sensible heat flux measurements can be combined with net radiation and soil heat flux measurements to estimate latent heat as a residual in the surface energy balance.

  17. Quantification of long-term wastewater fluxes at the surface water/groundwater-interface: an integrative model perspective using stable isotopes and acesulfame.

    Science.gov (United States)

    Engelhardt, I; Barth, J A C; Bol, R; Schulz, M; Ternes, T A; Schüth, C; van Geldern, R

    2014-01-01

    The suitability of acesulfame to trace wastewater-related surface water fluxes from streams into the hyporheic and riparian zones over long-term periods was investigated. The transport behavior of acesulfame was compared with the transport of water stable isotopes (δ(18)O or δ(2)H). A calibrated model based on a joint inversion of temperature, acesulfame, and piezometric pressure heads was employed in a model validation using data sets of acesulfame and water stable isotopes collected over 5months in a stream and groundwater. The spatial distribution of fresh water within the groundwater resulting from surface water infiltration was estimated by computing groundwater ages and compared with the predicted acesulfame plume obtained after 153day simulation time. Both, surface water ratios calculated with a mixing equation from water stable isotopes and simulated acesulfame mass fluxes, were investigated for their ability to estimate the contribution of wastewater-related surface water inflow within groundwater. The results of this study point to limitations for the application of acesulfame to trace surface water-groundwater interactions properly. Acesulfame completely missed the wastewater-related surface water volumes that still remained in the hyporheic zone under stream-gaining conditions. In contrast, under stream-losing conditions, which developed after periods of stagnating hydraulic exchange, acesulfame based predictions lead to an overestimation of the surface water volume of up to 25% in the riparian zone. If slow seepage velocities prevail a proportion of acesulfame might be stored in smaller pores, while when released under fast flowing water conditions it will travel further downstream with the groundwater flow direction. Therefore, under such conditions acesulfame can be a less-ideal tracer in the hyporheic and riparian zones and additional monitoring with other environmental tracers such as water stable isotopes is highly recommended. © 2013 Elsevier

  18. Comparison of regional and ecosystem CO{sub 2} fluxes

    Energy Technology Data Exchange (ETDEWEB)

    Gryning, S. E. (Wind Energy Department, Risoe National Laboratory for Sustainable Energy, Technical Univ. of Denmark, Roskilde (Denmark)); Soegaard, H. (Institute of Geography and Geology, University of Copenhagen, Copenhagen (Denmark)); Batchvarova, E. (National Institute of Meteorology and Hydrology, Bulgarian Academy of Sciences, Sofia (Bulgaria))

    2009-07-01

    A budget method to derive the regional surface flux of CO{sub 2} from the evolution of the boundary layer is presented and applied. The necessary input for the method can be deduced from a combination of vertical profile measurements of CO{sub 2} concentrations by i.e. an airplane, successive radio-soundings and standard measurements of the CO{sub 2} concentration near the ground. The method was used to derive the regional flux of CO{sub 2} over an agricultural site at Zealand in Denmark during an experiment on 12-13 June 2006. The regional fluxes of CO{sub 2} represent a combination of agricultural and forest surface conditions. It was found that the regional flux of CO{sub 2} in broad terms follows the behavior of the flux of CO{sub 2} at the agricultural (grassland) and the deciduous forest station. The regional flux is comparable not only in size but also in the diurnal (daytime) cycle of CO{sub 2} fluxes at the two stations. (orig.)

  19. Simulation of Lake Surface Heat Fluxes by the Canadian Small Lake Model: Offline Performance Assessment for Future Coupling with a Regional Climate Model

    Science.gov (United States)

    Pernica, P.; Guerrero, J. L.; MacKay, M.; Wheater, H. S.

    2014-12-01

    Lakes strongly influence local and regional climate especially in regions where they are abundant. Development of a lake model for the purpose of integration within a regional climate model is therefore a subject of scientific interest. Of particular importance are the heat flux predictions provided by the lake model since they function as key forcings in a fully coupled atmosphere-land-lake system. The first step towards a coupled model is to validate and characterize the accuracy of the lake model over a range of conditions and to identify limitations. In this work, validation results from offline tests of the Canadian Small Lake Model; a deterministic, computationally efficient, 1D integral model, are presented. Heat fluxes (sensible and latent) and surface water temperatures simulated by the model are compared with in situ observations from two lakes; Landing Lake (NWT, Canada) and L239 (ELA, Canada) for the 2007-2009 period. Sensitivity analysis is performed to identify key parameters important for heat flux predictions. The results demonstrate the ability of the 1-D lake model to reproduce both diurnal and seasonal variations in heat fluxes and surface temperatures for the open water period. These results, in context of regional climate modelling are also discussed.

  20. Surface hardening induced by high flux plasma in tungsten revealed by nano-indentation

    Energy Technology Data Exchange (ETDEWEB)

    Terentyev, D., E-mail: dterenty@sckcen.be [SCK-CEN, Nuclear Materials Science Institute, Boeretang 200, 2400 Mol (Belgium); Bakaeva, A. [SCK-CEN, Nuclear Materials Science Institute, Boeretang 200, 2400 Mol (Belgium); Department of Applied Physics, Ghent University, St. Pietersnieuwstraat 41, 9000 Ghent (Belgium); Pardoen, T.; Favache, A. [Institute of Mechanics, Materials and Civil Engineering, Université catholique de Louvain, Place Sainte Barbe 2 L5.02.02, 1348 Louvain-la-Neuve (Belgium); Zhurkin, E.E. [Department of Experimental Nuclear Physics K-89, Faculty of Physics and Mechanics, St. Petersburg State Polytechnical University, 29 Polytekhnicheskaya str., 195251 St. Petersburg (Russian Federation)

    2016-08-01

    Surface hardness of tungsten after high flux deuterium plasma exposure has been characterized by nanoindentation. The effect of plasma exposure was rationalized on the basis of available theoretical models. Resistance to plastic penetration is enhanced within the 100 nm sub-surface region, attributed to the pinning of geometrically necessary dislocations on nanometric deuterium cavities – signature of plasma-induced defects and deuterium retention. Sub-surface extension of thereby registered plasma-induced damage is in excellent agreement with the results of alternative measurements. The study demonstrates suitability of nano-indentation to probe the impact of deposition of plasma-induced defects in tungsten on near surface plasticity under ITER-relevant plasma exposure conditions.

  1. A comparison of cellulosic fuel yields and separated soil-surface CO2 fluxes in maize and prairie biofuel cropping systems

    Science.gov (United States)

    Nichols, Virginia A.

    It has been suggested that strategic incorporation of perennial vegetation into agricultural landscapes could provide ecosystem services while maintaining agricultural productivity. To evaluate potential use of prairie as a Midwestern cellulosic feedstock, we investigated theoretical cellulosic fuel yields, as well as soil-surface carbon dioxide emissions of prairie-based biofuel systems as compared to maize-based systems on fertile soils in Boone County, IA, USA. Investigated systems were: a maize-soybean rotation grown for grain only, continuous maize grown for grain and stover both with and without a winter rye cover crop, and a 31-species reconstructed prairie grown with and without spring nitrogen fertilization for fall-harvested biomass. From 2009-2013, the highest producing system was N-fertilized prairie, averaging 10.4 Mg ha -1 yr-1 above-ground biomass with average harvest removals of 7.8 Mg ha-1 yr-1. The unfertilized prairie produced 7.4 Mg ha-1 yr-1, averaging harvests of 5.3 Mg ha-1 yr-1. Lowest cellulosic biomass harvests were realized from continuous maize systems, averaging 3.5 Mg ha -1 yr-1 when grown with, and 3.7 Mg ha-1 yr-1 when grown without a winter rye cover crop, respectively. Un-fertilized prairie biomass and maize stover had equivalent dietary conversion ratios at 330 g ethanol kg-1 dry biomass, but N-fertilized prairie was lower at 315. Over four years prairie systems averaged 1287 L cellulosic ethanol ha-1 yr-1 more than maize systems, with fertilization increasing prairie ethanol production by 865 L ha-1 yr-1. Harvested biomass accounted for >90% of ethanol yield variation. A major hurdle in carbon cycling studies is the separation of the soil-surface CO2 flux into its respective components. From 2012-2013 we used a shading method to separate soil-surface CO2 resulting from oxidation of soil organic matter and CO2 derived from live-root activity in three systems: unfertilized prairie, N-fertilized prairie, and continuous maize

  2. Uncertainty analysis of the Operational Simplified Surface Energy Balance (SSEBop) model at multiple flux tower sites

    Science.gov (United States)

    Chen, Mingshi; Senay, Gabriel B.; Singh, Ramesh K.; Verdin, James P.

    2016-01-01

    Evapotranspiration (ET) is an important component of the water cycle – ET from the land surface returns approximately 60% of the global precipitation back to the atmosphere. ET also plays an important role in energy transport among the biosphere, atmosphere, and hydrosphere. Current regional to global and daily to annual ET estimation relies mainly on surface energy balance (SEB) ET models or statistical and empirical methods driven by remote sensing data and various climatological databases. These models have uncertainties due to inevitable input errors, poorly defined parameters, and inadequate model structures. The eddy covariance measurements on water, energy, and carbon fluxes at the AmeriFlux tower sites provide an opportunity to assess the ET modeling uncertainties. In this study, we focused on uncertainty analysis of the Operational Simplified Surface Energy Balance (SSEBop) model for ET estimation at multiple AmeriFlux tower sites with diverse land cover characteristics and climatic conditions. The 8-day composite 1-km MODerate resolution Imaging Spectroradiometer (MODIS) land surface temperature (LST) was used as input land surface temperature for the SSEBop algorithms. The other input data were taken from the AmeriFlux database. Results of statistical analysis indicated that the SSEBop model performed well in estimating ET with an R2 of 0.86 between estimated ET and eddy covariance measurements at 42 AmeriFlux tower sites during 2001–2007. It was encouraging to see that the best performance was observed for croplands, where R2 was 0.92 with a root mean square error of 13 mm/month. The uncertainties or random errors from input variables and parameters of the SSEBop model led to monthly ET estimates with relative errors less than 20% across multiple flux tower sites distributed across different biomes. This uncertainty of the SSEBop model lies within the error range of other SEB models, suggesting systematic error or bias of the SSEBop model is within

  3. On the analytical flux distribution modeling of an axial-flux surface-mounted permanent magnet motor for control applications

    International Nuclear Information System (INIS)

    Liu, C.-T.; Lin, S.-C.; Chiang, T.-S.

    2004-01-01

    By combining the recoil line characteristics of permanent magnet and the equivalent operational magnetic circuits at various rotor positions, a systematic procedure for developing the desired analytical model of an axial-flux surface-mounted permanent magnet motor can be devised. Supported by detailed three-dimensional finite element analysis results and statistical evaluations, accuracies of the developed analytical model can be guaranteed. With such well developed system model, the relative high-precision controls and operations of the motor can then be conveniently realized

  4. Dynamic ignition regime of condensed system by radiate heat flux

    International Nuclear Information System (INIS)

    Arkhipov, V A; Zolotorev, N N; Korotkikh, A G; Kuznetsov, V T

    2017-01-01

    The main ignition characteristics of high-energy materials are the ignition time and critical heat flux allowing evaluation of the critical conditions for ignition, fire and explosive safety for the test solid propellants. The ignition process is typically studied in stationary conditions of heat input at constant temperature of the heating surface, environment or the radiate heat flux on the sample surface. In real conditions, ignition is usually effected at variable time-dependent values of the heat flux. In this case, the heated layer is formed on the sample surface in dynamic conditions and significantly depends on the heat flux change, i.e. increasing or decreasing falling heat flux in the reaction period of the propellant sample. This paper presents a method for measuring the ignition characteristics of a high-energy material sample in initiation of the dynamic radiant heat flux, which includes the measurement of the ignition time when exposed to a sample time varying radiant heat flux given intensity. In case of pyroxyline containing 1 wt. % of soot, it is shown that the ignition times are reduced by 20–50 % depending on the initial value of the radiant flux density in initiation by increasing or decreasing radiant heat flux compared with the stationary conditions of heat supply in the same ambient conditions. (paper)

  5. Influence of tungsten microstructure and ion flux on deuterium plasma-induced surface modifications and deuterium retention

    NARCIS (Netherlands)

    Buzi, L.; De Temmerman, G.; Unterberg, B.; M. Reinhart,; Dittmar, T.; Matveev, D.; Linsmeier, C.; Breuer, U.; Kreter, A.; Van Oost, G.

    2015-01-01

    The influence of surface temperature, particle flux density and material microstructure on the surface morphology and deuterium retention was studied by exposing tungsten targets (20 μm and 40 μm grain size) to deuterium plasma at the same particle fluence (1026 m−2) and

  6. Area-averaged evapotranspiration over a heterogeneous land surface: aggregation of multi-point EC flux measurements with a high-resolution land-cover map and footprint analysis

    Directory of Open Access Journals (Sweden)

    F. Xu

    2017-08-01

    Full Text Available The determination of area-averaged evapotranspiration (ET at the satellite pixel scale/model grid scale over a heterogeneous land surface plays a significant role in developing and improving the parameterization schemes of the remote sensing based ET estimation models and general hydro-meteorological models. The Heihe Watershed Allied Telemetry Experimental Research (HiWATER flux matrix provided a unique opportunity to build an aggregation scheme for area-averaged fluxes. On the basis of the HiWATER flux matrix dataset and high-resolution land-cover map, this study focused on estimating the area-averaged ET over a heterogeneous landscape with footprint analysis and multivariate regression. The procedure is as follows. Firstly, quality control and uncertainty estimation for the data of the flux matrix, including 17 eddy-covariance (EC sites and four groups of large-aperture scintillometers (LASs, were carefully done. Secondly, the representativeness of each EC site was quantitatively evaluated; footprint analysis was also performed for each LAS path. Thirdly, based on the high-resolution land-cover map derived from aircraft remote sensing, a flux aggregation method was established combining footprint analysis and multiple-linear regression. Then, the area-averaged sensible heat fluxes obtained from the EC flux matrix were validated by the LAS measurements. Finally, the area-averaged ET of the kernel experimental area of HiWATER was estimated. Compared with the formerly used and rather simple approaches, such as the arithmetic average and area-weighted methods, the present scheme is not only with a much better database, but also has a solid grounding in physics and mathematics in the integration of area-averaged fluxes over a heterogeneous surface. Results from this study, both instantaneous and daily ET at the satellite pixel scale, can be used for the validation of relevant remote sensing models and land surface process models. Furthermore, this

  7. Area-averaged evapotranspiration over a heterogeneous land surface: aggregation of multi-point EC flux measurements with a high-resolution land-cover map and footprint analysis

    Science.gov (United States)

    Xu, Feinan; Wang, Weizhen; Wang, Jiemin; Xu, Ziwei; Qi, Yuan; Wu, Yueru

    2017-08-01

    The determination of area-averaged evapotranspiration (ET) at the satellite pixel scale/model grid scale over a heterogeneous land surface plays a significant role in developing and improving the parameterization schemes of the remote sensing based ET estimation models and general hydro-meteorological models. The Heihe Watershed Allied Telemetry Experimental Research (HiWATER) flux matrix provided a unique opportunity to build an aggregation scheme for area-averaged fluxes. On the basis of the HiWATER flux matrix dataset and high-resolution land-cover map, this study focused on estimating the area-averaged ET over a heterogeneous landscape with footprint analysis and multivariate regression. The procedure is as follows. Firstly, quality control and uncertainty estimation for the data of the flux matrix, including 17 eddy-covariance (EC) sites and four groups of large-aperture scintillometers (LASs), were carefully done. Secondly, the representativeness of each EC site was quantitatively evaluated; footprint analysis was also performed for each LAS path. Thirdly, based on the high-resolution land-cover map derived from aircraft remote sensing, a flux aggregation method was established combining footprint analysis and multiple-linear regression. Then, the area-averaged sensible heat fluxes obtained from the EC flux matrix were validated by the LAS measurements. Finally, the area-averaged ET of the kernel experimental area of HiWATER was estimated. Compared with the formerly used and rather simple approaches, such as the arithmetic average and area-weighted methods, the present scheme is not only with a much better database, but also has a solid grounding in physics and mathematics in the integration of area-averaged fluxes over a heterogeneous surface. Results from this study, both instantaneous and daily ET at the satellite pixel scale, can be used for the validation of relevant remote sensing models and land surface process models. Furthermore, this work will be

  8. The Oceanic Flux Program: A three decade time-series of particle flux in the deep Sargasso Sea

    Science.gov (United States)

    Weber, J. C.; Conte, M. H.

    2010-12-01

    The Oceanic Flux Program (OFP), 75 km SE of Bermuda, is the longest running time-series of its kind. Initiated in 1978, the OFP has produced an unsurpassed, nearly continuous record of temporal variability in deep ocean fluxes, with a >90% temporal coverage at 3200m depth. The OFP, in conjunction with the co-located Bermuda-Atlantic Time Series (BATS) and the Bermuda Testbed Mooring (BTM) time-series, has provided key observations enabling detailed assessment of how seasonal and non-seasonal variability in the deep ocean is linked with the overlying physical and biogeochemical environment. This talk will focus on the short-term flux variability that overlies the seasonal flux pattern in the Sargasso Sea, emphasizing episodic extreme flux events. Extreme flux events are responsible for much of the year-to-year variability in mean annual flux and are most often observed during early winter and late spring when surface stratification is weak or transient. In addition to biological phenomena (e.g. salp blooms), passage of productive meso-scale features such as eddies, which alter surface water mixing characteristics and surface export fluxes, may initiate some extreme flux events. Yet other productive eddies show a minimal influence on the deep flux, underscoring the importance of upper ocean ecosystem structure and midwater processes on the coupling between the surface ocean environment and deep fluxes. Using key organic and inorganic tracers, causative processes that influence deep flux generation and the strength of the coupling with the surface ocean environment can be identified.

  9. Inferring near surface soil temperature time series from different land uses to quantify the variation of heat fluxes into a shallow aquifer in Austria

    Science.gov (United States)

    Kupfersberger, Hans; Rock, Gerhard; Draxler, Johannes C.

    2017-09-01

    Different land uses exert a strong spatially distributed and temporal varying signal of heat fluxes from the surface in or out of the ground. In this paper we show an approach to quantify the heat fluxes into a groundwater body differentiating between near surface soil temperatures under grass, forest, asphalt, agriculture and surface water bodies and heat fluxes from subsurface structures like heated basements or sewage pipes. Based on observed time series of near surface soil temperatures we establish individual parameters (e.g. shift, moving average) of a simple empirical function that relates air temperature to soil temperature. This procedure is useful since air temperature time series are readily available and the complex energy flux processes at the soil atmosphere interface do not need to be described in detail. To quantify the heat flux from heated subsurface structures that have lesser depths to the groundwater table the 1D heat conduction module SoilTemp is developed. Based on soil temperature time series observed at different depths in a research lysimeter heat conduction and heat storage capacity values are calibrated disregarding their dependence on the water content. With SoilTemp the strong interaction between time series of groundwater temperature and groundwater level, near surface soil temperatures and the basement temperatures in heated buildings could be evaluated showing the dynamic nature of thermal gradients. The heat fluxes from urban areas are calculated considering the land use patterns within a spatial unit by mixing the heat fluxes from basements with those under grass and asphalt. The heat fluxes from sewage pipes and of sewage leakage are shown to be negligible for evaluated pipe diameters and sewage discharges. The developed methodology will allow to parameterize the upper boundary of heat transport models and to differentiate between the heat fluxes from different surface usages and their dynamics into the subsurface.

  10. Surface Turbulent Fluxes, 1x1 deg Daily Grid, Satellite F15 V2c

    Data.gov (United States)

    National Aeronautics and Space Administration — These data are part of the Goddard Satellite-based Surface Turbulent Fluxes Version-2c (GSSTF 2c) Dataset recently produced through a MEaSURES funded project led by...

  11. Optimizing critical heat flux enhancement through nano-particle-based surface modifications

    International Nuclear Information System (INIS)

    Truong, B.; Hu, L. W.; Buongiorno, J.

    2008-01-01

    Colloidal dispersions of nano-particles, also known as nano-fluids, have shown to yield significant Critical Heat Flux (CHF) enhancement. The CHF enhancement mechanism in nano-fluids is due to the buildup of a porous layer of nano-particles upon boiling. Unlike microporous coatings that had been studied extensively, nano-particles have the advantages of forming a thin layer on the substrate with surface roughness ranges from the sub-micron to several microns. By tuning the chemical properties it is possible to coat the nano-particles in colloidal dispersions onto the desired surface, as has been demonstrated in engineering thin film industry. Building on recent work conducted at MIT, this paper illustrates the maximum CHF enhancement that can be achieved based on existing correlations. Optimization of the CHF enhancement by incorporation of key factors, such as the surface wettability and roughness, will also be discussed. (authors)

  12. Dependence of trapped-flux-induced surface resistance of a large-grain Nb superconducting radio-frequency cavity on spatial temperature gradient during cooldown through Tc

    Science.gov (United States)

    Huang, Shichun; Kubo, Takayuki; Geng, R. L.

    2016-08-01

    Recent studies by Romanenko et al. revealed that cooling down a superconducting cavity under a large spatial temperature gradient decreases the amount of trapped flux and leads to reduction of the residual surface resistance. In the present paper, the flux expulsion ratio and the trapped-flux-induced surface resistance of a large-grain cavity cooled down under a spatial temperature gradient up to 80 K /m are studied under various applied magnetic fields from 5 to 20 μ T . We show the flux expulsion ratio improves as the spatial temperature gradient increases, independent of the applied magnetic field: our results support and enforce the previous studies. We then analyze all rf measurement results obtained under different applied magnetic fields together by plotting the trapped-flux-induced surface resistance normalized by the applied magnetic field as a function of the spatial temperature gradient. All the data can be fitted by a single curve, which defines an empirical formula for the trapped-flux-induced surface resistance as a function of the spatial temperature gradient and applied magnetic field. The formula can fit not only the present results but also those obtained by Romanenko et al. previously. The sensitivity rfl of surface resistance from trapped magnetic flux of fine-grain and large-grain niobium cavities and the origin of d T /d s dependence of Rfl/Ba are also discussed.

  13. Surface analyses of TiC coated molybdenum limiter material exposed to high heat flux electron beam

    International Nuclear Information System (INIS)

    Onozuka, M.; Uchikawa, T.; Yamao, H.; Kawai, H.; Kousaku, A.; Nakamura, H.; Niikura, S.

    1987-01-01

    Observation and surface analyses of TiC coated molybdenum exposed to high heat flux have been performed to study thermal damage resistance of TiC coated molybdenum limiter material. High heat loads were provided by a 120 kW electron beam facility. SEM, AES and EPMA have been applied to the surface analyses

  14. KoFlux: Korean Regional Flux Network in AsiaFlux

    Science.gov (United States)

    Kim, J.

    2002-12-01

    AsiaFlux, the Asian arm of FLUXNET, held the Second International Workshop on Advanced Flux Network and Flux Evaluation in Jeju Island, Korea on 9-11 January 2002. In order to facilitate comprehensive Asia-wide studies of ecosystem fluxes, the meeting launched KoFlux, a new Korean regional network of long-term micrometeorological flux sites. For a successful assessment of carbon exchange between terrestrial ecosystems and the atmosphere, an accurate measurement of surface fluxes of energy and water is one of the prerequisites. During the 7th Global Energy and Water Cycle Experiment (GEWEX) Asian Monsoon Experiment (GAME) held in Nagoya, Japan on 1-2 October 2001, the Implementation Committee of the Coordinated Enhanced Observing Period (CEOP) was established. One of the immediate tasks of CEOP was and is to identify the reference sites to monitor energy and water fluxes over the Asian continent. Subsequently, to advance the regional and global network of these reference sites in the context of both FLUXNET and CEOP, the Korean flux community has re-organized the available resources to establish a new regional network, KoFlux. We have built up domestic network sites (equipped with wind profiler and radiosonde measurements) over deciduous and coniferous forests, urban and rural rice paddies and coastal farmland. As an outreach through collaborations with research groups in Japan, China and Thailand, we also proposed international flux sites at ecologically and climatologically important locations such as a prairie on the Tibetan plateau, tropical forest with mixed and rapid land use change in northern Thailand. Several sites in KoFlux already begun to accumulate interesting data and some highlights are presented at the meeting. The sciences generated by flux networks in other continents have proven the worthiness of a global array of micrometeorological flux towers. It is our intent that the launch of KoFlux would encourage other scientists to initiate and

  15. Intercomparison of the finite difference and nodal discrete ordinates and surface flux transport methods for a LWR pool-reactor benchmark problem in X-Y geometry

    International Nuclear Information System (INIS)

    O'Dell, R.D.; Stepanek, J.; Wagner, M.R.

    1983-01-01

    The aim of the present work is to compare and discuss the three of the most advanced two dimensional transport methods, the finite difference and nodal discrete ordinates and surface flux method, incorporated into the transport codes TWODANT, TWOTRAN-NODAL, MULTIMEDIUM and SURCU. For intercomparison the eigenvalue and the neutron flux distribution are calculated using these codes in the LWR pool reactor benchmark problem. Additionally the results are compared with some results obtained by French collision probability transport codes MARSYAS and TRIDENT. Because the transport solution of this benchmark problem is close to its diffusion solution some results obtained by the finite element diffusion code FINELM and the finite difference diffusion code DIFF-2D are included

  16. Energy flux simulation in heterogeneous cropland - a two year study

    Science.gov (United States)

    Klein, Christian; Thieme, Christoph; Biernath, Christian; Heinlein, Florian; Priesack, Eckart

    2016-04-01

    Recent studies show that uncertainties in regional and global climate and weather simulations are partly due to inadequate descriptions of the energy flux exchanges between the land surface and the atmosphere [Stainforth et al. 2005]. One major shortcoming is the limitation of the grid-cell resolution, which is recommended to be about at least 3x3 km² in most models due to limitations in the model physics. To represent each individual grid cell most models select one dominant soil type and one dominant land use type. This resolution, however, is often too coarse in regions where the spatial heterogeneity of soil and land use types are high, e.g. in Central Europe. The relevance of vegetation (e.g. crops), ground cover, and soil properties to the moisture and energy exchanges between the land surface and the atmosphere is well known [McPherson 2007], but the impact of vegetation growth dynamics on energy fluxes is only partly understood [Gayler et al. 2014]. An elegant method to avoid the shortcoming of grid cell resolution is the so called mosaic approach. This approach is part of the recently developed ecosystem model framework Expert-N [Biernath et al. 2013] . The aim of this study was to analyze the impact of the characteristics of five managed field plots, planted with winter wheat, potato and maize on the near surface soil moistures and on the near surface energy flux exchanges of the soil-plant-atmosphere interface. The simulated energy fluxes were compared with eddy flux tower measurements between the respective fields at the research farm Scheyern, North-West of Munich, Germany. To perform these simulations, we coupled the ecosystem model Expert-N to an analytical footprint model [Mauder & Foken 2011] . The coupled model system has the ability to calculate the mixing ratio of the surface energy fluxes at a given point within one grid cell (in this case at the flux tower between the two fields). The approach accounts for the temporarily and spatially

  17. Calculation of the flux density of gamma rays above the surface of Venus and the Earth

    International Nuclear Information System (INIS)

    Surkov, Yu.A.; Manvelyan, O.S.

    1987-01-01

    In this article the authors present the results of calculating the flux density of unscattered gamma rays as a function of height above the surfaces of Venus and the Earth. At each height they calculate the areas which will collect a certain fraction of the gamma rays. The authors calculate the spectra of scattered gamma rays, as well as their integrated fluxes at various heights above the surface of Venus. They consider how the atmosphere will affect the recording of gamma rays. Their results enable them to evaluate the optimal conditions for measuring the gamma-ray fields above the surfaces of Venus and the Earth and to determine the area of the planet which can be investigated in this way. These results are also necessary if they are to determine the elemental composition of the rock from the characteristic recorded spectrum of gamma radiation

  18. Comparison of Sensible Heat Flux from Eddy Covariance and Scintillometer over different land surface conditions

    Science.gov (United States)

    Zeweldi, D. A.; Gebremichael, M.; Summis, T.; Wang, J.; Miller, D.

    2008-12-01

    The large source of uncertainty in satellite-based evapotranspiration algorithm results from the estimation of sensible heat flux H. Traditionally eddy covariance sensors, and recently large-aperture scintillometers, have been used as ground truth to evaluate satellite-based H estimates. The two methods rely on different physical measurement principles, and represent different foot print sizes. In New Mexico, we conducted a field campaign during summer 2008 to compare H estimates obtained from the eddy covariance and scintillometer methods. During this field campaign, we installed sonic anemometers; one propeller eddy covariance (OPEC) equipped with net radiometer and soil heat flux sensors; large aperture scintillometer (LAS); and weather station consisting of wind speed, direction and radiation sensors over three different experimental areas consisting of different roughness conditions (desert, irrigated area and lake). Our results show the similarities and differences in H estimates obtained from these various methods over the different land surface conditions. Further, our results show that the H estimates obtained from the LAS agree with those obtained from the eddy covariance method when high frequency thermocouple temperature, instead of the typical weather station temperature measurements, is used in the LAS analysis.

  19. An analytic model of pool boiling critical heat flux on an immerged downward facing curved surface

    International Nuclear Information System (INIS)

    He, Hui; Pan, Liang-ming; Wu, Yao; Chen, De-qi

    2015-01-01

    Highlights: • Thin liquid film and supplement of liquid contribute to the CHF. • CHF increases from the bottom to the upper of the lowerhead. • Evaporation of thin liquid film is dominant nearby bottom region. • The subcooling has significant effects on the CHF. - Abstract: In this paper, an analytical model of the critical heat flux (CHF) on the downward facing curved surface for pool boiling has been proposed, which hypothesizes that the CHF on the downward facing curved is composed of two parts, i.e. the evaporation of the thin liquid film underneath the elongated bubble adhering to the lower head outer surface and the depletion of supplement of liquid due to the relative motion of vapor bubbles along with the downward facing curved. The former adopts the Kelvin–Helmholtz instability analysis of vapor–liquid interface of the vapor jets which penetrating in the thin liquid film. When the heat flux closing to the CHF point, the vapor–liquid interface becomes highly distorted, which block liquid to feed the thin liquid film and the thin liquid film will dry out gradually. While the latter considers that the vapor bubbles move along with the downward facing curved surface, and the liquid in two-phase boundary layer enter the liquid film that will be exhausted when the CHF occurs. Based on the aforementioned mechanism and the energy balance between the thin liquid film evaporation and water feeding, and taking the subcooling of the bulk water into account, the mathematic model about the downward facing curved surface CHF has been proposed. The CHF of the downward facing curved surface for pool boiling increases along with the downward facing orientation except in the vicinity of bottom center region, because in this region the vapor bubble almost stagnates and the evaporation of the thin liquid film is dominant. In addition, the subcooling has significant effect on the CHF. Comparing the result of this model with the published experimental results show

  20. Optimal estimation of the surface fluxes of methyl chloride using a 3-D global chemical transport model

    Directory of Open Access Journals (Sweden)

    X. Xiao

    2010-06-01

    Full Text Available Methyl chloride (CH3Cl is a chlorine-containing trace gas in the atmosphere contributing significantly to stratospheric ozone depletion. Large uncertainties in estimates of its source and sink magnitudes and temporal and spatial variations currently exist. GEIA inventories and other bottom-up emission estimates are used to construct a priori maps of the surface fluxes of CH3Cl. The Model of Atmospheric Transport and Chemistry (MATCH, driven by NCEP interannually varying meteorological data, is then used to simulate CH3Cl mole fractions and quantify the time series of sensitivities of the mole fractions at each measurement site to the surface fluxes of various regional and global sources and sinks. We then implement the Kalman filter (with the unit pulse response method to estimate the surface fluxes on regional/global scales with monthly resolution from January 2000 to December 2004. High frequency observations from the AGAGE, SOGE, NIES, and NOAA/ESRL HATS in situ networks and low frequency observations from the NOAA/ESRL HATS flask network are used to constrain the source and sink magnitudes. The inversion results indicate global total emissions around 4100 ± 470 Gg yr−1 with very large emissions of 2200 ± 390 Gg yr−1 from tropical plants, which turn out to be the largest single source in the CH3Cl budget. Relative to their a priori annual estimates, the inversion increases global annual fungal and tropical emissions, and reduces the global oceanic source. The inversion implies greater seasonal and interannual oscillations of the natural sources and sink of CH3Cl compared to the a priori. The inversion also reflects the strong effects of the 2002/2003 globally widespread heat waves and droughts on global emissions from tropical plants, biomass burning and salt marshes, and on the soil sink.

  1. Stagnation point flow towards nonlinear stretching surface with Cattaneo-Christov heat flux

    Science.gov (United States)

    Hayat, T.; Zubair, M.; Ayub, M.; Waqas, M.; Alsaedi, A.

    2016-10-01

    Here the influence of the non-Fourier heat flux in a two-dimensional (2D) stagnation point flow of Eyring-Powell liquid towards a nonlinear stretched surface is reported. The stretching surface is of variable thickness. Thermal conductivity of fluid is taken temperature-dependent. Ordinary differential systems are obtained through the implementation of meaningful transformations. The reduced non-dimensional expressions are solved for the convergent series solutions. Convergence interval is obtained for the computed solutions. Graphical results are displayed and analyzed in detail for the velocity, temperature and skin friction coefficient. The obtained results reveal that the temperature gradient enhances when the thermal relaxation parameter is increased.

  2. Influence of tungsten microstructure and ion flux on deuterium plasma-induced surface modifications and deuterium retention

    Energy Technology Data Exchange (ETDEWEB)

    Buzi, Luxherta [IEK - Plasmaphysik, Forschungszentrum Juelich GmbH, Association EURATOM-FZJ, Juelich (Germany); FOM Institute DIFFER-Dutch Institute for Fundamental Energy Research (Netherlands); Ghent University (Belgium); Temmerman, Greg de [FOM Institute DIFFER-Dutch Institute for Fundamental Energy Research (Netherlands); Reinhart, Michael; Matveev, Dmitry; Unterberg, Bernhard; Wienhold, Peter; Breuer, Uwe; Kreter, Arkadi [IEK - Plasmaphysik, Forschungszentrum Juelich GmbH, Association EURATOM-FZJ, Juelich (Germany); Oost, Guido van [Ghent University (Belgium)

    2014-07-01

    Tungsten is to be used as plasma-facing material for the ITER divertor due to its favourable thermal properties, low erosion and fuel retention. Bombardment of tungsten by low energy ions of hydrogen isotopes, at different surface temperature, can lead to surface modifications and influence the fuel accumulation in the material. This contribution will assess the impact of material microstructure and the correlation between the particle flux, surface modifications and deuterium retention in tungsten. Tungsten samples were exposed to deuterium plasma at a surface temperature of 510 K, 670 K and 870 K, ion energy of 40 eV and ion fluence of 10{sup 26} m{sup -2}. The high and low ion flux ranges were in the order 10{sup 24} m{sup -2}s{sup -1} and 10{sup 22} m{sup -2}s{sup -1}. Depth profiling of deuterium in all the samples was done by secondary ion mass spectroscopy technique and a scanning electron microscope was used to investigate the surface modifications. Modelling of the D desorption spectra with the coupled reaction diffusion system model will be also presented.

  3. Flux surface shaping effects on tokamak edge turbulence and flows

    Energy Technology Data Exchange (ETDEWEB)

    Kendl, A. [Innsbruck Univ., Institut fuer Theoretische Physik, Association EURATOM (Austria); Scott, B.D. [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Garching bei Muenchen (Germany)

    2004-07-01

    The influence of shaping of magnetic flux surfaces in tokamaks on gyro-fluid edge turbulence is studied numerically. Magnetic field shaping in tokamaks is mainly due to elongation, triangularity, shift and the presence of a divertor X-point. A series of tokamak configurations with varying elongation 1 {<=} {kappa} {>=} 2 and triangularity 0 {<=} {delta} {<=} 0.4, and an actual ASDEX Upgrade divertor configuration are obtained with the equilibrium code HELENA and implemented into the gyro-fluid turbulence code GEM. The study finds minimal impact on the zonal flow physics itself, but strong impact on the turbulence and transport. (authors)

  4. Flux surface shaping effects on tokamak edge turbulence and flows

    International Nuclear Information System (INIS)

    Kendl, A.; Scott, B.D.

    2004-01-01

    The influence of shaping of magnetic flux surfaces in tokamaks on gyro-fluid edge turbulence is studied numerically. Magnetic field shaping in tokamaks is mainly due to elongation, triangularity, shift and the presence of a divertor X-point. A series of tokamak configurations with varying elongation 1 ≤ κ ≥ 2 and triangularity 0 ≤ δ ≤ 0.4, and an actual ASDEX Upgrade divertor configuration are obtained with the equilibrium code HELENA and implemented into the gyro-fluid turbulence code GEM. The study finds minimal impact on the zonal flow physics itself, but strong impact on the turbulence and transport. (authors)

  5. Mass transfer inside a flux hood for the sampling of gaseous emissions from liquid surfaces - Experimental assessment and emission rate rescaling

    Science.gov (United States)

    Prata, Ademir A.; Lucernoni, Federico; Santos, Jane M.; Capelli, Laura; Sironi, Selena; Le-Minh, Nhat; Stuetz, Richard M.

    2018-04-01

    This study assesses the mass transfer of compounds inside the US EPA flux hood, one of the enclosure devices most commonly employed for the direct measurement of atmospheric emissions from liquid surfaces in wastewater treatment plants (WWTPs). Experiments comprised the evaporation of water and the volatilisation of a range of volatile organic compounds (VOCs). Special attention was given to the evaluation of the mass transfer coefficients in the microenvironment created by the flux hood and the effects of concentration build up in the hood's headspace. The VOCs emission rates and the water evaporation rates generally increased with the sweep air flow rate, as did the mass transfer coefficients for all compounds. The emission of compounds whose volatilisation is significantly influenced by the gas phase was greatly affected by concentration build up, whereas this effect was not significant for liquid phase-controlled compounds. The gas-film mass transfer coefficient (kG) estimated inside the US EPA flux hood was of the same order as the respective kG reported in the literature for wind tunnel-type devices, but the emission rates measured by the flux hood can be expected to be lower, due to the concentration build-up. Compared against an emission model for the passive surfaces in WWTPs, the mass transfer of acetic acid (representing a gas phase-dominated compound) inside the US EPA flux hood was equivalent to conditions of wind speeds at 10 m height (U10) of 0.27, 0.51 and 0.99 m s-1, respectively, for sweep air flow rates of 2, 5 and 10 L min-1. On the other hand, for higher wind speeds, the emission rates of gas phase-controlled compounds obtained with the flux hood can be considerably underestimated: for instance, at U10 = 5 m s-1, the emission rates of acetic acid inside the flux hood would be approximately 23, 12 and 6 times lower than the emission rates in the field, for sweep air flow rates of 2, 5 and 10 L min-1, respectively. A procedure is presented in

  6. Seasonality of Overstory and Understory Fluxes in a Semi-Arid Oak Savanna: What can be Learned from Comparing Measured and Modeled Fluxes?

    Science.gov (United States)

    Raz-Yaseef, N.; Sonnentag, O.; Kobayashi, H.; Chen, J. M.; Verfaillie, J. G.; Ma, S.; Baldocchi, D. D.

    2011-12-01

    Semi-arid climates experience large seasonal and inter-annual variability in radiation and precipitation, creating natural conditions adequate to study how year-to-year changes affect atmosphere-biosphere fluxes. Especially, savanna ecosystems, that combine tree and below-canopy components, create a unique environment in which phenology dramatically changes between seasons. We used a 10-year flux database in order to define seasonal and interannual variability of climatic inputs and fluxes, and evaluate model capability to reproduce observed variability. This is based on the perception that model capability to construct the deviation, and not the average, is important in order to correctly predict ecosystem sensitivity to climate change. Our research site is a low density and low LAI (0.8) semi-arid savanna, located at Tonzi Ranch, Northern California. In this system, trees are active during the warm season (Mar - Oct), and grasses are active during the wet season (Dec - May). Measurements of carbon and water fluxes above and below the tree canopy using eddy covariance and supplementary measurements have been made since 2001. Fluxes were simulated using bio-meteorological process-oriented ecosystem models: BEPS and 3D-CAONAK. Models were partly capable of reproducing fluxes on daily scales (R2=0.66). We then compared model outputs for different ecosystem components and seasons, and found distinct seasons with high correlations while other seasons were purely represented. Comparison was much higher for ET than for GPP. The understory was better simulated than the overstory. CANOAK overestimated spring understory fluxes, probably due to the capability to directly calculated 3D radiative transfer. BEPS underestimated spring understory fluxes, following the pre-description of grass die-off. Both models underestimated peak spring overstory fluxes. During winter tree dormant, modeled fluxes were null, but occasional high fluxes of both ET and GPP were measured following

  7. Global CO2 fluxes estimated from GOSAT retrievals of total column CO2

    Directory of Open Access Journals (Sweden)

    S. Basu

    2013-09-01

    Full Text Available We present one of the first estimates of the global distribution of CO2 surface fluxes using total column CO2 measurements retrieved by the SRON-KIT RemoTeC algorithm from the Greenhouse gases Observing SATellite (GOSAT. We derive optimized fluxes from June 2009 to December 2010. We estimate fluxes from surface CO2 measurements to use as baselines for comparing GOSAT data-derived fluxes. Assimilating only GOSAT data, we can reproduce the observed CO2 time series at surface and TCCON sites in the tropics and the northern extra-tropics. In contrast, in the southern extra-tropics GOSAT XCO2 leads to enhanced seasonal cycle amplitudes compared to independent measurements, and we identify it as the result of a land–sea bias in our GOSAT XCO2 retrievals. A bias correction in the form of a global offset between GOSAT land and sea pixels in a joint inversion of satellite and surface measurements of CO2 yields plausible global flux estimates which are more tightly constrained than in an inversion using surface CO2 data alone. We show that assimilating the bias-corrected GOSAT data on top of surface CO2 data (a reduces the estimated global land sink of CO2, and (b shifts the terrestrial net uptake of carbon from the tropics to the extra-tropics. It is concluded that while GOSAT total column CO2 provide useful constraints for source–sink inversions, small spatiotemporal biases – beyond what can be detected using current validation techniques – have serious consequences for optimized fluxes, even aggregated over continental scales.

  8. Effects of heat flux on dropwise condensation on a superhydrophobic surface

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Kyung Won; Park, Hyun Sun; Moriyama, Kiyofumi [POSTECH, Pohang (Korea, Republic of); Kim, Dong Hyun [KAERI, Daejeon (Korea, Republic of); Jo, Hang Jin [University of Wisconsin-Madison, Wisconsin (United States); Kim, Moo Hwan [KINS, Daejeon (Korea, Republic of)

    2016-05-15

    The condensation heat transfer efficiencies of superhydrophobic surfaces that have ∼160.deg. contact angle under atmospheric conditions were investigated experimentally. The departing diameter and the contact angle hysteresis of droplets were measured by capturing front and tilted side views of condensation phenomena with a high speed camera and an endoscope, respectively. Condensation behaviors on the surface were observed at the micro-scale using an Environmental scanning electron microscope (ESEM). Apparently-spherical droplets formed at very low heat flux q' ∼20 kW/m{sup 2} but hemispherical droplets formed at high q' ∼ 440 kW/m{sup 2} . At high q', heat transfer coefficients were lower on the superhydrophobic surface than on a hydrophobic surface although the superhydrophobic surface is water repellent so droplets roll off. The results of contact angle hysteresis and ESEM image revealed that the reduced heat transfer of the surface can be attributed to the large size of departing droplets caused by adhesive condensed droplets at nucleation sites. The results suggest that the effect of q' or degree of sub-cooling of a condensation wall determine the droplet shape, which is closely related to removal rates of condensates and finally to the heat transfer coefficient.

  9. Inferring CO2 Fluxes from OCO-2 for Assimilation into Land Surface Models to Calculate Net Ecosystem Exchange

    Science.gov (United States)

    Prouty, R.; Radov, A.; Halem, M.; Nearing, G. S.

    2016-12-01

    Investigations of mid to high latitude atmospheric CO2 show a growing seasonal amplitude. Land surface models poorly predict net ecosystem exchange (NEE) and are unable to substantiate these sporadic observations. An investigation of how the biosphere has reacted to changes in atmospheric CO2 is essential to our understanding of potential climate-vegetation feedbacks. A global, seasonal investigation of CO2-flux is then necessary in order to assimilate into land surface models for improving the prediction of annual NEE. The Atmospheric Radiation Measurement program (ARM) of DOE collects CO2-flux measurements (in addition to CO2 concentration and various other meteorological quantities) at several towers located around the globe at half hour temporal frequencies. CO2-fluxes are calculated via the eddy covariance technique, which utilizes CO2-densities and wind velocities to calculate CO2-fluxes. The global coverage of CO2 concentrations as provided by the Orbiting Carbon Observatory (OCO-2) provide satellite-derived CO2 concentrations all over the globe. A framework relating the satellite-inferred CO2 concentrations collocated with the ground-based ARM as well as Ameriflux stations would enable calculations of CO2-fluxes far from the station sites around the entire globe. Regression techniques utilizing deep-learning neural networks may provide such a framework. Additionally, meteorological reanalysis allows for the replacement of the ARM multivariable meteorological variables needed to infer the CO2-fluxes. We present the results of inferring CO2-fluxes from OCO-2 CO2 concentrations for a two year period, Sept. 2014- Sept. 2016 at the ARM station located near Oklahoma City. A feed-forward neural network (FFNN) is used to infer relationships between the following data sets: F([ARM CO2-density], [ARM Meteorological Data]) = [ARM CO2-Flux] F([OCO-2 CO2-density],[ARM Meteorological Data]) = [ARM CO2-Flux] F([ARM CO2-density],[Meteorological Reanalysis]) = [ARM CO2-Flux

  10. An eddy covariance system to characterize the atmospheric surface layer and turbulent latent heat fluxes over a debris-covered Himalayan glacier.

    Science.gov (United States)

    Litt, Maxime; Steiner, Jakob F.; Stigter, Emmy E.; Immerzeel, Walter; Shea, Joseph Michael

    2017-04-01

    Over debris-covered glaciers, water content variations in the debris layer can drive significant changes in its thermal conductivity and significantly impact melt rates. Since sublimation and evaporation are favoured in high-altitude conditions, e.g., low atmospheric pressure and high wind speeds, they are expected to strongly influence the water balance of the debris-layer. Dedicated latent heat fluxes measurements at the debris surface are essential to characterize the debris heat conductivity in order to assess underlying ice melt. Furthermore, the contribution of the turbulent fluxes in the surface energy balance over debris covered glacier remains uncertain since they are generally evaluated through similarity methods which might not be valid in complex terrain. We present the first results of a 15-day eddy-covariance experiment installed at the end of the monsoon (September-October) on a 3-m tower above the debris-covered Lirung glacier in Nepal. The tower also included measurements of the 4 radiation components. The eddy covariance measurements allowed for the characterization of the turbulence in the atmospheric surface layer, as well as the direct measurements of evaporation, sublimation and turbulent sensible heat fluxes. The experiment helps us to evaluate the contribution of turbulent fluxes to the surface energy balance over this debris-covered glacier, through a precise characterization of the overlying turbulent atmospheric surface layer. It also helps to study the role of the debris-layer water content changes through evaporation and sublimation and its feedback on heat conduction in this layer. The large observed turbulent fluxes play a significant role in the energy balance at the debris surface and significantly influence debris moisture, conductivity and subsequently underlying ice melt.

  11. Assessing uncertainty and sensitivity of model parameterizations and parameters in WRF affecting simulated surface fluxes and land-atmosphere coupling over the Amazon region

    Science.gov (United States)

    Qian, Y.; Wang, C.; Huang, M.; Berg, L. K.; Duan, Q.; Feng, Z.; Shrivastava, M. B.; Shin, H. H.; Hong, S. Y.

    2016-12-01

    This study aims to quantify the relative importance and uncertainties of different physical processes and parameters in affecting simulated surface fluxes and land-atmosphere coupling strength over the Amazon region. We used two-legged coupling metrics, which include both terrestrial (soil moisture to surface fluxes) and atmospheric (surface fluxes to atmospheric state or precipitation) legs, to diagnose the land-atmosphere interaction and coupling strength. Observations made using the Department of Energy's Atmospheric Radiation Measurement (ARM) Mobile Facility during the GoAmazon field campaign together with satellite and reanalysis data are used to evaluate model performance. To quantify the uncertainty in physical parameterizations, we performed a 120 member ensemble of simulations with the WRF model using a stratified experimental design including 6 cloud microphysics, 3 convection, 6 PBL and surface layer, and 3 land surface schemes. A multiple-way analysis of variance approach is used to quantitatively analyze the inter- and intra-group (scheme) means and variances. To quantify parameter sensitivity, we conducted an additional 256 WRF simulations in which an efficient sampling algorithm is used to explore the multiple-dimensional parameter space. Three uncertainty quantification approaches are applied for sensitivity analysis (SA) of multiple variables of interest to 20 selected parameters in YSU PBL and MM5 surface layer schemes. Results show consistent parameter sensitivity across different SA methods. We found that 5 out of 20 parameters contribute more than 90% total variance, and first-order effects dominate comparing to the interaction effects. Results of this uncertainty quantification study serve as guidance for better understanding the roles of different physical processes in land-atmosphere interactions, quantifying model uncertainties from various sources such as physical processes, parameters and structural errors, and providing insights for

  12. Measurements of EUV coronal holes and open magnetic flux

    International Nuclear Information System (INIS)

    Lowder, C.; Qiu, J.; Leamon, R.; Liu, Y.

    2014-01-01

    Coronal holes are regions on the Sun's surface that map the footprints of open magnetic field lines. We have developed an automated routine to detect and track boundaries of long-lived coronal holes using full-disk extreme-ultraviolet (EUV) images obtained by SOHO/EIT, SDO/AIA, and STEREO/EUVI. We measure coronal hole areas and magnetic flux in these holes, and compare the measurements with calculations by the potential field source surface (PFSS) model. It is shown that, from 1996 through 2010, the total area of coronal holes measured with EIT images varies between 5% and 17% of the total solar surface area, and the total unsigned open flux varies between (2-5)× 10 22 Mx. The solar cycle dependence of these measurements is similar to the PFSS results, but the model yields larger hole areas and greater open flux than observed by EIT. The AIA/EUVI measurements from 2010-2013 show coronal hole area coverage of 5%-10% of the total surface area, with significant contribution from low latitudes, which is under-represented by EIT. AIA/EUVI have measured much enhanced open magnetic flux in the range of (2-4)× 10 22 Mx, which is about twice the flux measured by EIT, and matches with the PFSS calculated open flux, with discrepancies in the location and strength of coronal holes. A detailed comparison between the three measurements (by EIT, AIA-EUVI, and PFSS) indicates that coronal holes in low latitudes contribute significantly to the total open magnetic flux. These low-latitude coronal holes are not well measured with either the He I 10830 line in previous studies, or EIT EUV images; neither are they well captured by the static PFSS model. The enhanced observations from AIA/EUVI allow a more accurate measure of these low-latitude coronal holes and their contribution to open magnetic flux.

  13. Potential feedbacks between snow cover, soil moisture and surface energy fluxes in Southern Norway

    Science.gov (United States)

    Brox Nilsen, Irene; Tallaksen, Lena M.; Stordal, Frode

    2017-04-01

    At high latitudes, the snow season has become shorter during the past decades because snowmelt is highly sensitive to a warmer climate. Snowmelt influences the energy balance by changing the albedo and the partitioning between latent and sensible heat fluxes. It further influences the water balance by changing the runoff and soil moisture. In a previous study, we identified southern Norway as a region where significant temperature changes in summer could potentially be explained by land-atmosphere interactions. In this study we hypothesise that changes in snow cover would influence the summer surface fluxes in the succeeding weeks or months. The exceptionally warm summer of 2014 was chosen as a test bed. In Norway, evapotranspiration is not soil moisture limited, but energy limited, under normal conditions. During warm summers, however, such as in 2014, evapotranspiration can be restricted by the available soil moisture. Using the Weather Research and Forecasting (WRF) model we replace the initial ground conditions for 2014 with conditions representative of a snow-poor spring and a snow-rich spring. WRF was coupled to Noah-MP at 3 km horizontal resolution in the inner domain, and the simulations covered mid-May through September 2014. Boundary conditions used to force WRF were taken from the Era-Interim reanalysis. Snow, runoff, soil moisture and soil temperature observational data were provided by the Norwegian Water Resources and Energy Directorate for validation. The validation shows generally good agreement with observations. Preliminary results show that the reduced snowpack, hereafter "sim1" increased the air temperature by up to 5 K and the surface temperature by up to 10 K in areas affected by snow changes. The increased snowpack, hereafter "sim2", decreased the air and surface temperature by the same amount. These are weekly mean values for the first eight simulation weeks from mid May. Because of the higher net energy available ( 100 Wm-2) in sim 1, both

  14. Impact of Land Cover Change Induced by a Fire Event on the Surface Energy Fluxes Derived from Remote Sensing

    Directory of Open Access Journals (Sweden)

    Juan M. Sánchez

    2015-11-01

    Full Text Available Forest fires affect the natural cycle of the vegetation, and the structure and functioning of ecosystems. As a consequence of defoliation and vegetation mortality, surface energy flux patterns can suffer variations. Remote sensing techniques together with surface energy balance modeling offer the opportunity to explore these changes. In this paper we focus on a Mediterranean forest ecosystem. A fire event occurred in 2001 in Almodóvar del Pinar (Spain affecting a pine and shrub area. A two-source energy balance approach was applied to a set of Landsat 5-TM and Landsat 7-EMT+ images to estimate the surface fluxes in the area. Three post-fire periods were analyzed, six, seven, nine, and 11 years after the fire event. Results showed the regeneration of the shrub area in 6–7 years, in contrast to the pine area, where an important decrease in evapotranspiration, around 1 mm·day−1, remained. Differences in evapotranspiration were mitigated nine and 11 years after the fire in the pine area, whereas significant deviations in the rest of the terms of the energy balance equation were still observed. The combined effect of changes in the vegetation structure and surface variables, such as land surface temperature, albedo, or vegetation coverage, is responsible for these variations in the surface energy flux patterns.

  15. Water, Energy, and Carbon with Artificial Neural Networks (WECANN): a statistically based estimate of global surface turbulent fluxes and gross primary productivity using solar-induced fluorescence

    Science.gov (United States)

    Hamed Alemohammad, Seyed; Fang, Bin; Konings, Alexandra G.; Aires, Filipe; Green, Julia K.; Kolassa, Jana; Miralles, Diego; Prigent, Catherine; Gentine, Pierre

    2017-09-01

    A new global estimate of surface turbulent fluxes, latent heat flux (LE) and sensible heat flux (H), and gross primary production (GPP) is developed using a machine learning approach informed by novel remotely sensed solar-induced fluorescence (SIF) and other radiative and meteorological variables. This is the first study to jointly retrieve LE, H, and GPP using SIF observations. The approach uses an artificial neural network (ANN) with a target dataset generated from three independent data sources, weighted based on a triple collocation (TC) algorithm. The new retrieval, named Water, Energy, and Carbon with Artificial Neural Networks (WECANN), provides estimates of LE, H, and GPP from 2007 to 2015 at 1° × 1° spatial resolution and at monthly time resolution. The quality of ANN training is assessed using the target data, and the WECANN retrievals are evaluated using eddy covariance tower estimates from the FLUXNET network across various climates and conditions. When compared to eddy covariance estimates, WECANN typically outperforms other products, particularly for sensible and latent heat fluxes. Analyzing WECANN retrievals across three extreme drought and heat wave events demonstrates the capability of the retrievals to capture the extent of these events. Uncertainty estimates of the retrievals are analyzed and the interannual variability in average global and regional fluxes shows the impact of distinct climatic events - such as the 2015 El Niño - on surface turbulent fluxes and GPP.

  16. REMOTE SENSING AND SURFACE ENERGY FLUX MODELS TO DERIVE EVAPOTRANSPIRATION AND CROP COEFFICIENT

    Directory of Open Access Journals (Sweden)

    Salvatore Barbagallo

    2008-06-01

    Full Text Available Remote sensing techniques using high resolution satellite images provide opportunities to evaluate daily crop water use and its spatial and temporal distribution on a field by field basis. Mapping this indicator with pixels of few meters of size on extend areas allows to characterize different processes and parameters. Satellite data on vegetation reflectance, integrated with in field measurements of canopy coverage features and the monitoring of energy fluxes through the soil-plant-atmosphere system, allow to estimate conventional irrigation components (ET, Kc thus improving irrigation strategies. In the study, satellite potential evapotranspiration (ETp and crop coefficient (Kc maps of orange orchards are derived using semi-empirical approaches between reflectance data from IKONOS imagery and ground measurements of vegetation features. The monitoring of energy fluxes through the orchard allows to estimate actual crop evapotranspiration (ETa using energy balance and the Surface Renewal theory. The approach indicates substantial promise as an efficient, accurate and relatively inexpensive procedure to predict actual ET fluxes and Kc from irrigated lands.

  17. Surface Turbulent Fluxes, 1x1 deg Monthly Climatology, Set1 and NCEP V2c

    Data.gov (United States)

    National Aeronautics and Space Administration — These data are the Goddard Satellite-based Surface Turbulent Fluxes Version-2c Dataset recently produced through a MEaSURES funded project led by Dr. Chung-Lin Shie...

  18. Surface Turbulent Fluxes, 1x1 deg Yearly Climatology, Set1 and NCEP V2c

    Data.gov (United States)

    National Aeronautics and Space Administration — These data are the Goddard Satellite-based Surface Turbulent Fluxes Version-2c Dataset recently produced through a MEaSURES funded project led by Dr. Chung-Lin Shie...

  19. Temperature-dependent surface modification of Ta due to high-flux, low-energy He+ ion irradiation

    International Nuclear Information System (INIS)

    Novakowski, T.J.; Tripathi, J.K.; Hassanein, A.

    2015-01-01

    This work examines the response of Tantalum (Ta) as a potential candidate for plasma-facing components (PFCs) in future nuclear fusion reactors. Tantalum samples were exposed to high-flux, low-energy He + ion irradiation at different temperatures in the range of 823–1223 K. The samples were irradiated at normal incidence with 100 eV He + ions at constant flux of 1.2 × 10 21 ions m −2  s −1 to a total fluence of 4.3 × 10 24 ions m −2 . An additional Ta sample was also irradiated at 1023 K using a higher ion fluence of 1.7 × 10 25 ions m −2 (at the same flux of 1.2 × 10 21 ions m −2  s −1 ), to confirm the possibility of fuzz formation at higher fluence. This higher fluence was chosen to roughly correspond to the lower fluence threshold of fuzz formation in Tungsten (W). Surface morphology was characterized with a combination of field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). These results demonstrate that the main mode of surface damage is pinholes with an average size of ∼70 nm 2 for all temperatures. However, significantly larger pinholes are observed at elevated temperatures (1123 and 1223 K) resulting from the agglomeration of smaller pinholes. Ex situ X-ray photoelectron spectroscopy (XPS) provides information about the oxidation characteristics of irradiated surfaces, showing minimal exfoliation of the irradiated Ta surface. Additionally, optical reflectivity measurements are performed to further characterize radiation damage on Ta samples, showing gradual reductions in the optical reflectivity as a function of temperature.

  20. Fate factors and emission flux estimates for emerging contaminants in surface waters

    Directory of Open Access Journals (Sweden)

    Hoa T. Trinh

    2016-01-01

    Full Text Available Pharmaceuticals, personal care products, hormones, and wastewater products are emerging environmental concerns for manifold reasons, including the potential of some compounds found in these products for endocrine disruption at a very low chronic exposure level. The environmental occurrences and sources of these contaminants in the water, soil, sediment and biota in European nations and the United States are well documented. This work reports a screening-level emission and fate assessment of thirty compounds, listed in the National Reconnaissance of the United States Geological Survey (USGS, 1999–2000 as the most frequently detected organic wastewater contaminants in U.S. streams and rivers. Estimations of the surface water fate factors were based on Level II and Level III multimedia fugacity models for a 1000 km2 model environment, the size of a typical county in the eastern United States. The compounds are categorized into three groups based upon the sensitivity of their predicted surface water fate factors to uncertainties in their physicochemical property values and the landscape parameters. The environmental fate factors, mass distributions, and loss pathways of all of the compounds are strongly affected by their assumed modes of entry into the environment. It is observed that for thirteen of the thirty organic wastewater contaminants most commonly detected in surface waters, conventional treatment strategies may be ineffective for their removal from wastewater effluents. The surface water fate factors predicted by the fugacity models were used in conjunction with the surface water concentrations measured in the USGS reconnaissance to obtain emission flux estimates for the compounds into U.S. streams and rivers. These include estimated fluxes of 6.8 × 10−5 to 0.30 kg/h km2 for the biomarker coprostanol; 1.7 × 10−5 to 6.5 × 10−5 kg/h km2 for the insect repellent N,N-diethyltoluamide; and 4.3 × 10−6 to 3.1 × 10−5 kg/h km2 for

  1. Determination of transient temperature and heat flux on the surface of a reactor control rod based on temperature measurements at the interior points

    International Nuclear Information System (INIS)

    Cebula, Artur; Taler, Jan

    2014-01-01

    The paper presents heat transfer calculation results concerning a control rod of nuclear power plant. Apart from numerical calculation results, experimental heat transfer measurements of the control rod model are also presented. The control rod that is the object of interest is surrounded by a mixing region of hot and cold streams and, as a consequence, is subjected to thermal fluctuations. The paper describes a method based on the solution of the inverse heat conduction problem (IHCP) for determining heat flux on the outer surface of the rod. Numerical tests were conducted to validate the method by comparison of the results with the time changes of surface temperature and heat flux which were obtained from the computational fluid dynamics (CFD) simulation of the mixing process. A measuring instrument was designed to measure the heat flux at the outer surface of the control rod model. In addition, the principle of operation and construction of heat flux meter is presented in detail. -- Highlights: • Temperature and heat flux estimation during cooling of control rod are presented. • The inverse technique is based on the space marching method. • The instrument for surface heat flux measurement was manufactured and tested. • CFD simulations were used to validate the developed inverse technique. • Actual data were used to demonstrate practical applicability of the method

  2. The Global Energy Balance Archive (GEBA) version 2017: a database for worldwide measured surface energy fluxes

    Science.gov (United States)

    Wild, Martin; Ohmura, Atsumu; Schär, Christoph; Müller, Guido; Folini, Doris; Schwarz, Matthias; Zyta Hakuba, Maria; Sanchez-Lorenzo, Arturo

    2017-08-01

    The Global Energy Balance Archive (GEBA) is a database for the central storage of the worldwide measured energy fluxes at the Earth's surface, maintained at ETH Zurich (Switzerland). This paper documents the status of the GEBA version 2017 dataset, presents the new web interface and user access, and reviews the scientific impact that GEBA data had in various applications. GEBA has continuously been expanded and updated and contains in its 2017 version around 500 000 monthly mean entries of various surface energy balance components measured at 2500 locations. The database contains observations from 15 surface energy flux components, with the most widely measured quantity available in GEBA being the shortwave radiation incident at the Earth's surface (global radiation). Many of the historic records extend over several decades. GEBA contains monthly data from a variety of sources, namely from the World Radiation Data Centre (WRDC) in St. Petersburg, from national weather services, from different research networks (BSRN, ARM, SURFRAD), from peer-reviewed publications, project and data reports, and from personal communications. Quality checks are applied to test for gross errors in the dataset. GEBA has played a key role in various research applications, such as in the quantification of the global energy balance, in the discussion of the anomalous atmospheric shortwave absorption, and in the detection of multi-decadal variations in global radiation, known as global dimming and brightening. GEBA is further extensively used for the evaluation of climate models and satellite-derived surface flux products. On a more applied level, GEBA provides the basis for engineering applications in the context of solar power generation, water management, agricultural production and tourism. GEBA is publicly accessible through the internet via http://www.geba.ethz.ch. Supplementary data are available at https://doi.org/10.1594/PANGAEA.873078.

  3. MHD Flow Towards a Permeable Surface with Prescribed Wall Heat Flux

    International Nuclear Information System (INIS)

    Ishak, Anuar; Nazar, Roslinda; Pop, Ioan

    2009-01-01

    The steady magnetohydrodynamic (MHD) mixed convection flow towards a vertical permeable surface with prescribed heat flux is investigated. The governing partial differential equations are transformed into a system of ordinary differential equations, which is then solved numerically by a finite-difference method. The features of the flow and heat transfer characteristics for different values of the governing parameters are analysed and discussed. Both assisting and opposing flows are considered. It is found that dual solutions exist for the assisting flow, besides the solutions usually reported in the literature for the opposing fow

  4. Couplings between the seasonal cycles of surface thermodynamics and radiative fluxes in the semi-arid Sahel

    Science.gov (United States)

    Guichard, F.; Kergoat, L.; Mougin, E.; Timouk, F.; Bock, O.; Hiernaux, P.

    2009-04-01

    A good knowledge of surface fluxes and atmospheric low levels is central to improving our understanding of the West African monsoon. This study provides a quantitative analysis of the peculiar seasonal and diurnal cycles of surface thermodynamics and radiative fluxes encountered in Central Sahel. It is based on a multi-year dataset collected in the Malian Gourma over a sandy soil at 1.5°W-15.3°N (a site referred to as Agoufou) with an automated weather station and a sunphotometer (AERONET), complemented by observations from the AMMA field campaign. The seasonal cycle of this Tropical region is characterized by a broad maximum of temperature in May, following the first minimum of the solar zenith angle by a few weeks, when Agoufou lies within the West African Heat-Low, and a late summer maximum of equivalent potential temperature within the core of the monsoon season, around the second yearly maximum of solar zenith angle, as the temperature reaches its Summer minimum. More broadly, subtle balances between surface air temperature and moisture fields are found on a range of scales. For instance, during the monsoon, apart from August, their opposite daytime fluctuations (warming, drying) lead to an almost flat diurnal cycle of the equivalent potential temperature at the surface. This feature stands out in contrast to other more humid continental regions. Here, the strong dynamics associated with the transition from a drier hot Spring to a brief cooler wet tropical Summer climate involves very large transformations of the diurnal cycles. The Summer increase of surface net radiation, Rnet, is also strong; typically 10-day mean Rnet reaches about 5 times its Winter minimum (~30 W.m-2) in August (~150 W.m-2). A major feature revealed by observations is that this increase is mostly driven by modifications of the surface upwelling fluxes shaped by rainfall events and vegetation phenology (surface cooling and darkening), while the direct impact of atmospheric changes on

  5. Transient flow between aquifers and surface water: analytically derived field-scale hydraulic heads and fluxes

    Directory of Open Access Journals (Sweden)

    G. H. de Rooij

    2012-03-01

    Full Text Available The increasing importance of catchment-scale and basin-scale models of the hydrological cycle makes it desirable to have a simple, yet physically realistic model for lateral subsurface water flow. As a first building block towards such a model, analytical solutions are presented for horizontal groundwater flow to surface waters held at prescribed water levels for aquifers with parallel and radial flow. The solutions are valid for a wide array of initial and boundary conditions and additions or withdrawals of water, and can handle discharge into as well as lateral infiltration from the surface water. Expressions for the average hydraulic head, the flux to or from the surface water, and the aquifer-scale hydraulic conductivity are developed to provide output at the scale of the modelled system rather than just point-scale values. The upscaled conductivity is time-variant. It does not depend on the magnitude of the flux but is determined by medium properties as well as the external forcings that drive the flow. For the systems studied, with lateral travel distances not exceeding 10 m, the circular aquifers respond very differently from the infinite-strip aquifers. The modelled fluxes are sensitive to the magnitude of the storage coefficient. For phreatic aquifers a value of 0.2 is argued to be representative, but considerable variations are likely. The effect of varying distributions over the day of recharge damps out rapidly; a soil water model that can provide accurate daily totals is preferable over a less accurate model hat correctly estimates the timing of recharge peaks.

  6. Dependence of trapped-flux-induced surface resistance of a large-grain Nb superconducting radio-frequency cavity on spatial temperature gradient during cooldown through T_{c}

    Directory of Open Access Journals (Sweden)

    Shichun Huang

    2016-08-01

    Full Text Available Recent studies by Romanenko et al. revealed that cooling down a superconducting cavity under a large spatial temperature gradient decreases the amount of trapped flux and leads to reduction of the residual surface resistance. In the present paper, the flux expulsion ratio and the trapped-flux-induced surface resistance of a large-grain cavity cooled down under a spatial temperature gradient up to 80  K/m are studied under various applied magnetic fields from 5 to 20  μT. We show the flux expulsion ratio improves as the spatial temperature gradient increases, independent of the applied magnetic field: our results support and enforce the previous studies. We then analyze all rf measurement results obtained under different applied magnetic fields together by plotting the trapped-flux-induced surface resistance normalized by the applied magnetic field as a function of the spatial temperature gradient. All the data can be fitted by a single curve, which defines an empirical formula for the trapped-flux-induced surface resistance as a function of the spatial temperature gradient and applied magnetic field. The formula can fit not only the present results but also those obtained by Romanenko et al. previously. The sensitivity r_{fl} of surface resistance from trapped magnetic flux of fine-grain and large-grain niobium cavities and the origin of dT/ds dependence of R_{fl}/B_{a} are also discussed.

  7. Quantification of long-term wastewater fluxes at the surface water/groundwater-interface: An integrative model perspective using stable isotopes and acesulfame

    Energy Technology Data Exchange (ETDEWEB)

    Engelhardt, I., E-mail: i.engelhardt@fz-juelich.de [Forschungszentrum Jülich, Institute of Bio- and Geosciences, Agrosphere — IBG-3 (Germany); Technical University of Darmstadt, Institute of Applied Geosciences (Germany); Barth, J.A.C. [GeoZentrum Nordbayern, University of Erlangen-Nuremberg (Germany); Bol, R. [Forschungszentrum Jülich, Institute of Bio- and Geosciences, Agrosphere — IBG-3 (Germany); Schulz, M.; Ternes, T.A. [Federal Institute of Hydrology (BfG) (Germany); Schüth, C. [Technical University of Darmstadt, Institute of Applied Geosciences (Germany); van Geldern, R. [GeoZentrum Nordbayern, University of Erlangen-Nuremberg (Germany)

    2014-01-01

    The suitability of acesulfame to trace wastewater-related surface water fluxes from streams into the hyporheic and riparian zones over long-term periods was investigated. The transport behavior of acesulfame was compared with the transport of water stable isotopes (δ{sup 18}O or δ{sup 2}H). A calibrated model based on a joint inversion of temperature, acesulfame, and piezometric pressure heads was employed in a model validation using data sets of acesulfame and water stable isotopes collected over 5 months in a stream and groundwater. The spatial distribution of fresh water within the groundwater resulting from surface water infiltration was estimated by computing groundwater ages and compared with the predicted acesulfame plume obtained after 153 day simulation time. Both, surface water ratios calculated with a mixing equation from water stable isotopes and simulated acesulfame mass fluxes, were investigated for their ability to estimate the contribution of wastewater-related surface water inflow within groundwater. The results of this study point to limitations for the application of acesulfame to trace surface water–groundwater interactions properly. Acesulfame completely missed the wastewater-related surface water volumes that still remained in the hyporheic zone under stream-gaining conditions. In contrast, under stream-losing conditions, which developed after periods of stagnating hydraulic exchange, acesulfame based predictions lead to an overestimation of the surface water volume of up to 25% in the riparian zone. If slow seepage velocities prevail a proportion of acesulfame might be stored in smaller pores, while when released under fast flowing water conditions it will travel further downstream with the groundwater flow direction. Therefore, under such conditions acesulfame can be a less-ideal tracer in the hyporheic and riparian zones and additional monitoring with other environmental tracers such as water stable isotopes is highly recommended

  8. Gross greenhouse gas fluxes from hydro-power reservoir compared to thermo-power plants

    International Nuclear Information System (INIS)

    Santos, Marco Aurelio dos; Pinguelli Rosa, Luiz; Sikar, Bohdan; Sikar, Elizabeth; Santos, Ednaldo Oliveira dos

    2006-01-01

    This paper presents the findings of gross carbon dioxide and methane emissions measurements in several Brazilian hydro-reservoirs, compared to thermo power generation. The term 'gross emissions' means gas flux measurements from the reservoir surface without natural pre-impoundment emissions by natural bodies such as the river channel, seasonal flooding and terrestrial ecosystems. The net emissions result from deducting pre-existing emissions by the reservoir. A power dam emits biogenic gases such as CO 2 and CH 4 . However, studies comparing gas emissions (gross emissions) from the reservoir surface with emissions by thermo-power generation technologies show that the hydro-based option presents better results in most cases analyzed. In this study, measurements were carried in the Miranda, Barra Bonita, Segredo, Tres Marias, Xingo, and Samuel and Tucurui reservoirs, located in two different climatological regimes. Additional data were used here from measurements taken at the Itaipu and Serra da Mesa reservoirs. Comparisons were also made between emissions from hydro-power plants and their thermo-based equivalents. Bearing in mind that the estimated values for hydro-power plants include emissions that are not totally anthropogenic, the hydro-power plants studied generally posted lower emissions than their equivalent thermo-based counterparts. Hydro-power complexes with greater power densities (capacity/area flooded-W/m 2 ), such as Itaipu, Xingo, Segredo and Miranda, have the best performance, well above thermo-power plants using state-of-the-art technology: combined cycle fueled by natural gas, with 50% efficiency. On the other hand, some hydro-power complexes with low-power density perform only slightly better or even worse than their thermo-power counterparts

  9. Effects of high heat flux hydrogen and helium mixture beam irradiation on surface modification and hydrogen retention in tungsten materials

    International Nuclear Information System (INIS)

    Tokunaga, K.; Fujiwara, T.; Ezato, K.; Suzuki, S.; Akiba, M.; Kurishita, H.; Nagata, S.; Tsuchiya, B.; Tonegawa, A.; Yoshida, N.

    2009-01-01

    High heat flux experiments using a hydrogen-helium mixture beam have been carried out on powder metallurgy tungsten (PM-W) and ultra fine grain W-TiC alloy (W-0.5 wt%TiC-H 2 ). The energy of is 18 keV. Beam flux and heat flux at the beam center is 2.0 x 10 21 atoms/m 2 s and 7.0 MW/m 2 , respectively. Typical ratio of He/D ion is 0.25. Beam duration is 1.5-3 s and interval of beam shot start is 30 s. The samples are irradiated up to a fluence of 10 22 -10 24 He/m 2 by the repeated irradiation pulses. After the irradiation, surface modification by the irradiation and hydrogen retention, surface composition have been investigated. Surface modification by hydrogen-helium mixture beams is completely different from results of single beam irradiation. In particular, mixture beam irradiation causes remarkably high hydrogen retention.

  10. Estimation of surface heat and moisture fluxes over a prairie grassland. I - In situ energy budget measurements incorporating a cooled mirror dew point hygrometer

    Science.gov (United States)

    Smith, Eric A.; Crosson, William L.; Tanner, Bertrand D.

    1992-01-01

    Attention is focused on in situ measurements taken during FIFE required to support the development and validation of a biosphere model. Seasonal time series of surface flux measurements obtained from two surface radiation and energy budget stations utilized to support the FIFE surface flux measurement subprogram are examined. Data collection and processing procedures are discussed along with the measurement analysis for the complete 1987 test period.

  11. Sensitivity of Surface Temperature to Oceanic Forcing via q-Flux Green’s Function Experiments. Part I: Linear Response Function

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Fukai; Lu, Jian; Garuba, Oluwayemi A.; Leung, Lai-Yung; Luo, Yiyong; Wan, Xiuquan

    2018-05-01

    This paper explores the use of linear response function (LRF) to relate the mean sea surface temperature (SST) response to prescribed ocean heat convergence (q-flux) forcings. Two methods for constructing the LRF based on the fluctuation-dissipation theorem (FDT) and Green’s function (GRF) are examined. A 900-year preindustrial simulation from the Community Earth System Model with a slab ocean (CESM-SOM) is used to estimate the LRF using FDT. For GRF, 106 pairs of CESM-SOM simulations with warm and cold q-flux patches are performed. FDT is found to have skill in estimating the SST response to a q-flux forcing when the local SST response is strong, but it fails in inverse estimation of the q-flux forcing for a given SST pattern. In contrast, GRF is shown to be reasonably accurate in estimating both SST response and q-flux forcing. Possible degradation in FDT may be attributed to insufficient data sampling, significant departures of the SST data from Gaussian, and the non-normality of the constructed operator. The accurately estimated GRF-based LRF is used to (i) generate a global surface temperature sensitivity map that shows the q-flux forcing in higher latitudes to be three to four times more effective than in low latitudes in producing global surface warming; (ii) identify the most excitable SST mode (neutral vector) resembling Interdecadal Pacific Oscillation; and (iii) estimate a time-invariant q-flux forcing needed for maintaining the GHG-induced SST warming pattern. The GRF experiments will be used to construct LRF for other variables to further explore climate sensitivities and feedbacks.

  12. Atmospheric inversion of the surface CO2 flux with 13CO2 constraint

    Science.gov (United States)

    Chen, J. M.; Mo, G.; Deng, F.

    2013-10-01

    Observations of 13CO2 at 73 sites compiled in the GLOBALVIEW database are used for an additional constraint in a global atmospheric inversion of the surface CO2 flux using CO2 observations at 210 sites for the 2002-2004 period for 39 land regions and 11 ocean regions. This constraint is implemented using the 13CO2/CO2 flux ratio modeled with a terrestrial ecosystem model and an ocean model. These models simulate 13CO2 discrimination rates of terrestrial photosynthesis and respiration and ocean-atmosphere diffusion processes. In both models, the 13CO2 disequilibrium between fluxes to and from the atmosphere is considered due to the historical change in atmospheric 13CO2 concentration. For the 2002-2004 period, the 13CO2 constraint on the inversion increases the total land carbon sink from 3.40 to 3.70 Pg C yr-1 and decreases the total oceanic carbon sink from 1.48 to 1.12 Pg C yr-1. The largest changes occur in tropical areas: a considerable decrease in the carbon source in the Amazon forest, and this decrease is mostly compensated by increases in the ocean region immediately west of the Amazon and the southeast Asian land region. Our further investigation through different treatments of the 13CO2/CO2 flux ratio used in the inversion suggests that variable spatial distributions of the 13CO2 isotopic discrimination rate simulated by the models over land and ocean have considerable impacts on the spatial distribution of the inverted CO2 flux over land and the inversion results are not sensitive to errors in the estimated disequilibria over land and ocean.

  13. Using Flux Site Observations to Calibrate Root System Architecture Stencils for Water Uptake of Plant Functional Types in Land Surface Models.

    Science.gov (United States)

    Bouda, M.

    2017-12-01

    Root system architecture (RSA) can significantly affect plant access to water, total transpiration, as well as its partitioning by soil depth, with implications for surface heat, water, and carbon budgets. Despite recent advances in land surface model (LSM) descriptions of plant hydraulics, RSA has not been included because of its three-dimensional complexity, which makes RSA modelling generally too computationally costly. This work builds upon the recently introduced "RSA stencil," a process-based 1D layered model that captures the dynamic shifts in water potential gradients of 3D RSA in response to heterogeneous soil moisture profiles. In validations using root systems calibrated to the rooting profiles of four plant functional types (PFT) of the Community Land Model, the RSA stencil predicts plant water potentials within 2% of the outputs of full 3D models, despite its trivial computational cost. In transient simulations, the RSA stencil yields improved predictions of water uptake and soil moisture profiles compared to a 1D model based on root fraction alone. Here I show how the RSA stencil can be calibrated to time-series observations of soil moisture and transpiration to yield a water uptake PFT definition for use in terrestrial models. This model-data integration exercise aims to improve LSM predictions of soil moisture dynamics and, under water-limiting conditions, surface fluxes. These improvements can be expected to significantly impact predictions of downstream variables, including surface fluxes, climate-vegetation feedbacks and soil nutrient cycling.

  14. Evaluation of different methods to model near-surface turbulent fluxes for a mountain glacier in the Cariboo Mountains, BC, Canada

    Science.gov (United States)

    Radić, Valentina; Menounos, Brian; Shea, Joseph; Fitzpatrick, Noel; Tessema, Mekdes A.; Déry, Stephen J.

    2017-12-01

    As part of surface energy balance models used to simulate glacier melting, choosing parameterizations to adequately estimate turbulent heat fluxes is extremely challenging. This study aims to evaluate a set of four aerodynamic bulk methods (labeled as C methods), commonly used to estimate turbulent heat fluxes for a sloped glacier surface, and two less commonly used bulk methods developed from katabatic flow models. The C methods differ in their parameterizations of the bulk exchange coefficient that relates the fluxes to the near-surface measurements of mean wind speed, air temperature, and humidity. The methods' performance in simulating 30 min sensible- and latent-heat fluxes is evaluated against the measured fluxes from an open-path eddy-covariance (OPEC) method. The evaluation is performed at a point scale of a mountain glacier, using one-level meteorological and OPEC observations from multi-day periods in the 2010 and 2012 summer seasons. The analysis of the two independent seasons yielded the same key findings, which include the following: first, the bulk method, with or without the commonly used Monin-Obukhov (M-O) stability functions, overestimates the turbulent heat fluxes over the observational period, mainly due to a substantial overestimation of the friction velocity. This overestimation is most pronounced during the katabatic flow conditions, corroborating the previous findings that the M-O theory works poorly in the presence of a low wind speed maximum. Second, the method based on a katabatic flow model (labeled as the KInt method) outperforms any C method in simulating the friction velocity; however, the C methods outperform the KInt method in simulating the sensible-heat fluxes. Third, the best overall performance is given by a hybrid method, which combines the KInt approach with the C method; i.e., it parameterizes eddy viscosity differently than eddy diffusivity. An error analysis reveals that the uncertainties in the measured meteorological

  15. Evaluation of different methods to model near-surface turbulent fluxes for a mountain glacier in the Cariboo Mountains, BC, Canada

    Directory of Open Access Journals (Sweden)

    V. Radić

    2017-12-01

    Full Text Available As part of surface energy balance models used to simulate glacier melting, choosing parameterizations to adequately estimate turbulent heat fluxes is extremely challenging. This study aims to evaluate a set of four aerodynamic bulk methods (labeled as C methods, commonly used to estimate turbulent heat fluxes for a sloped glacier surface, and two less commonly used bulk methods developed from katabatic flow models. The C methods differ in their parameterizations of the bulk exchange coefficient that relates the fluxes to the near-surface measurements of mean wind speed, air temperature, and humidity. The methods' performance in simulating 30 min sensible- and latent-heat fluxes is evaluated against the measured fluxes from an open-path eddy-covariance (OPEC method. The evaluation is performed at a point scale of a mountain glacier, using one-level meteorological and OPEC observations from multi-day periods in the 2010 and 2012 summer seasons. The analysis of the two independent seasons yielded the same key findings, which include the following: first, the bulk method, with or without the commonly used Monin–Obukhov (M–O stability functions, overestimates the turbulent heat fluxes over the observational period, mainly due to a substantial overestimation of the friction velocity. This overestimation is most pronounced during the katabatic flow conditions, corroborating the previous findings that the M–O theory works poorly in the presence of a low wind speed maximum. Second, the method based on a katabatic flow model (labeled as the KInt method outperforms any C method in simulating the friction velocity; however, the C methods outperform the KInt method in simulating the sensible-heat fluxes. Third, the best overall performance is given by a hybrid method, which combines the KInt approach with the C method; i.e., it parameterizes eddy viscosity differently than eddy diffusivity. An error analysis reveals that the uncertainties in

  16. Measurements of EUV coronal holes and open magnetic flux

    Energy Technology Data Exchange (ETDEWEB)

    Lowder, C.; Qiu, J.; Leamon, R. [Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Liu, Y., E-mail: clowder@solar.physics.montana.edu [W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 (United States)

    2014-03-10

    Coronal holes are regions on the Sun's surface that map the footprints of open magnetic field lines. We have developed an automated routine to detect and track boundaries of long-lived coronal holes using full-disk extreme-ultraviolet (EUV) images obtained by SOHO/EIT, SDO/AIA, and STEREO/EUVI. We measure coronal hole areas and magnetic flux in these holes, and compare the measurements with calculations by the potential field source surface (PFSS) model. It is shown that, from 1996 through 2010, the total area of coronal holes measured with EIT images varies between 5% and 17% of the total solar surface area, and the total unsigned open flux varies between (2-5)× 10{sup 22} Mx. The solar cycle dependence of these measurements is similar to the PFSS results, but the model yields larger hole areas and greater open flux than observed by EIT. The AIA/EUVI measurements from 2010-2013 show coronal hole area coverage of 5%-10% of the total surface area, with significant contribution from low latitudes, which is under-represented by EIT. AIA/EUVI have measured much enhanced open magnetic flux in the range of (2-4)× 10{sup 22} Mx, which is about twice the flux measured by EIT, and matches with the PFSS calculated open flux, with discrepancies in the location and strength of coronal holes. A detailed comparison between the three measurements (by EIT, AIA-EUVI, and PFSS) indicates that coronal holes in low latitudes contribute significantly to the total open magnetic flux. These low-latitude coronal holes are not well measured with either the He I 10830 line in previous studies, or EIT EUV images; neither are they well captured by the static PFSS model. The enhanced observations from AIA/EUVI allow a more accurate measure of these low-latitude coronal holes and their contribution to open magnetic flux.

  17. Pool boiling characteristics and critical heat flux mechanisms of microporous surfaces and enhancement through structural modification

    Science.gov (United States)

    Ha, Minseok; Graham, Samuel

    2017-08-01

    Experimental studies have shown that microporous surfaces induce one of the highest enhancements in critical heat flux (CHF) during pool boiling. However, microporous surfaces may also induce a very large surface superheat (>100 °C) which is not desirable for applications such as microelectronics cooling. While the understanding of the CHF mechanism is the key to enhancing boiling heat transfer, a comprehensive understanding is not yet available. So far, three different theories for the CHF of microporous surfaces have been suggested: viscous-capillary model, hydrodynamic instability model, and dryout of the porous coatings. In general, all three theories account for some aspects of boiling phenomena. In this study, the theories are examined through their correlations with experimental data on microporous surfaces during pool boiling using deionized (DI) water. It was found that the modulation of the vapor-jet through the pore network enables a higher CHF than that of a flat surface based on the hydrodynamic instability theory. In addition, it was found that as the heat flux increases, a vapor layer grows in the porous coatings described by a simple thermal resistance model which is responsible for the large surface superheat. Once the vapor layer grows to fill the microporous structure, transition to film boiling occurs and CHF is reached. By disrupting the formation of this vapor layer through the fabrication of channels to allow vapor escape, an enhancement in the CHF and heat transfer coefficient was observed, allowing CHF greater than 3500 kW/m2 at a superheat less than 50 °C.

  18. Clustering of Emerging Flux

    Science.gov (United States)

    Ruzmaikin, A.

    1997-01-01

    Observations show that newly emerging flux tends to appear on the Solar surface at sites where there is flux already. This results in clustering of solar activity. Standard dynamo theories do not predict this effect.

  19. Surface Turbulent Fluxes, 1x1 deg Monthly Grid, Set1 and Interpolated Data V2c

    Data.gov (United States)

    National Aeronautics and Space Administration — These data are the Goddard Satellite-based Surface Turbulent Fluxes Version-2c Dataset recently produced through a MEaSUREs funded project led by Dr. Chung-Lin Shie...

  20. The influence of surface roughness and turbulence on heat fluxes from an oil palm plantation in Jambi, Indonesia

    Science.gov (United States)

    June, Tania; Meijide, Ana; Stiegler, Christian; Purba Kusuma, Alan; Knohl, Alexander

    2018-05-01

    Oil palm plantations are expanding vastly in Jambi, resulted in altered surface roughness and turbulence characteristics, which may influence exchange of heat and mass. Micrometeorological measurements above oil palm canopy were conducted for the period 2013–2015. The oil palms were 12.5 years old, canopy height 13 meters and 1.5 years old canopy height 2.5 m. We analyzed the influence of surface roughness and turbulence strenght on heat (sensible and latent) fluxes by investigating the profiles and gradient of wind speed, and temperature, surface roughness (roughness length, zo, and zero plane displacement, d), and friction velocity u*. Fluxes of heat were calculated using profile similarity methods taking into account atmospheric stability calculated using Richardson number Ri and the generalized stability factor ζ. We found that roughness parameters (zo, d, and u*) directly affect turbulence in oil palm canopy and hence heat fluxes; they are affected by canopy height, wind speed and atmospheric stability. There is a negative trend of d towards air temperature above the oil palm canopy, indicating the effect of plant volume and height in lowering air temperature. We propose studying the relation between zero plane displacement d with a remote sensing vegetation index for scaling up this point based analysis.

  1. Surface analyses of TiC coated molybdenum limiter material exposed to high heat flux electron beam

    International Nuclear Information System (INIS)

    Onozuka, M.; Uchikawa, T.; Yamao, H.; Kawai, H.; Kousaku, A.; Nakamura, H.; Niikura, S.

    1986-01-01

    Observation and surface analyses of TiC coated molybdenum exposed to high heat flux have been performed to study thermal damage resistance of TiC coated molybdenum limiter material. High heat loads were provided by a 120 kW electron beam facility. (author)

  2. Effect of Paste Flux Concentration on Adhesion Behavior

    Directory of Open Access Journals (Sweden)

    DU Quan-bin

    2017-11-01

    Full Text Available In view of the problem that paste flux is difficult to spread uniformly on the surface of filler metal, the adhesion behavior of the different concentrations of paste flux on the surface of filler metal was studied by the equipment of OM, wetting angle tester and surface tensiometer. The results show that adhesive layer is gradually thickened with the increase of the concentration of paste flux. A small amount of shrinkage appears in the thin adhesive layer. however, mass paste flux slides off filler metal when adhesive layer is thicker, accompanying by severe aggregation and shrinkage. For the ideal surface, the adhesive tension of paste flux with different concentrations of paste flux is the same. For the actual surface, the stripe groove additional pressure is formed when paste flux wets stripe groove, and the additional pressure is the main reason for the lagging phenomenon of the shrinkage of the adhesive layer. With the increase of paste flux concentration, the additional pressure decreases, the hysteresis resistance decreases, and the shrinkage increases. A relationship is satisfied when the shrinkage takes place in thin adhesive layer, this is ΔWC ≥ A+ΔP. Whether the shrinkage occurs mainly depends on the adhesion tension and the additional pressure.

  3. Defining the Magnitude: Patterns, Regularities and Direct TOA-Surface Flux Relationships in the 15-Year Long CERES Satellite Data — Observations, Model and Theory

    Science.gov (United States)

    Zagoni, M.

    2017-12-01

    Over the past fifteen years, the NASA Clouds and the Earth's Radiant Energy System (CERES) satellite mission has provided the scientific community with the most reliable Earth radiation budget data. This presentation offers quantitative assessment of the published CERES Energy Balanced and Filled (EBAF) Edition 2.8 and Edition 4.0 data products, and reveals several internal patterns, ratios and regularities within the annual global mean flux components of the all-sky and clear-sky surface and atmospheric energy budgets. The found patterns, among others, include: (i) direct relationships between the top-of-atmosphere (TOA) radiative and surface radiative and non-radiative fluxes (contradicting the expectation that TOA and surface fluxes are physically decoupled); (ii) integer ratios and relationships between the absorbed and emitted surface and atmospheric energy flow elements; and (iii) definite connections among the clear-sky and the all-sky shortwave, longwave and non-radiative (turbulent) flux elements and the corresponding greenhouse effect. Comparison between the EBAF Ed2.8 and Ed4.0 SFC and TOA data products and trend analyses of the normalized clear-sky and all-sky greenhouse factors are presented. Longwave cloud radiative effect (LW CRE) proved to be playing a principal role in organizing the found numerical patterns in the surface and atmospheric energy flow components. All of the revealed structures are quantitatively valid within the one-sigma range of uncertainty of the involved individual flux elements. This presentation offers a conceptual framework to interpret the found relationships and shows how the observed CERES fluxes can be deduced from this proposed physical model. An important conclusion drawn from our analysis is that the internal atmospheric and surface energy flow system forms a definite structure and seems to be more constrained to the incoming solar energy than previously thought.

  4. Surface flux density distribution characteristics of bulk high-T c superconductor in external magnetic field

    International Nuclear Information System (INIS)

    Nishikawa, H.; Torii, S.; Yuasa, K.

    2005-01-01

    This paper describes the measured results of the two-dimensional flux density distribution of a YBCO bulk under applied AC magnetic fields with various frequency. Melt-processed oxide superconductors have been developed in order to obtain strong pinning forces. Various electric mechanical systems or magnetic levitation systems use those superconductors. The major problem is that cracks occur because the bulk superconductors are brittle. The bulk may break in magnetizing process after cracks make superconducting state instable. The trapped flux density and the permanent current characteristics of bulk superconductors have been analyzed, so as to examine the magnetizing processes or superconducting states of the bulk. In those studies, the two-dimensional surface flux density distributions of the bulk in static fields are discussed. On the other hand, the distributions in dynamic fields are little discussed. We attempted to examine the states of the bulk in the dynamic fields, and made a unique experimental device which has movable sensors synchronized with AC applied fields. As a result, the two-dimensional distributions in the dynamic fields are acquired by recombining the one-dimensional distributions. The dynamic states of the flux of the bulk and the influences of directions of cracks are observed from the distributions. In addition, a new method for measuring two-dimensional flux density distribution under dynamic magnetic fields is suggested

  5. Nanofluidic transport over a curved surface with viscous dissipation and convective mass flux

    Energy Technology Data Exchange (ETDEWEB)

    Mehmood, Zaffar; Iqbal, Z.; Azhar, Ehtsham; Maraj, E.N. [HITEC Univ., Taxila (Pakistan). Dept. of Mathematics

    2017-06-01

    This article is a numerical investigation of boundary layer flow of nanofluid over a bended stretching surface. The study is carried out by considering convective mass flux condition. Contribution of viscous dissipation is taken into the account along with thermal radiation. Suitable similarity transformations are employed to simplify the system of nonlinear partial differential equations into a system of nonlinear ordinary differential equations. Computational results are extracted by means of a shooting method embedded with a Runge-Kutta Fehlberg technique. Key findings include that velocity is a decreasing function of curvature parameter K. Moreover, Nusselt number decreases with increase in curvature of the stretching surface while skin friction and Sherwood number enhance with increase in K.

  6. Temperature-dependent surface porosity of Nb{sub 2}O{sub 5} under high-flux, low-energy He{sup +} ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Novakowski, T.J., E-mail: tnovakow@purdue.edu; Tripathi, J.K.; Hosinski, G.M.; Joseph, G.; Hassanein, A.

    2016-01-30

    Graphical abstract: - Highlights: • Nb{sub 2}O{sub 5} surfaces are nanostructured with a novel He{sup +} ion irradiation process. • High-flux, low energy He{sup +} ion irradiation generates highly porous surfaces. • Top-down approach guarantees good contact between different crystallites. • Sample annealing demonstrates temperature effect on surface morphology. • Surface pore diameter increases with increasing temperature. - Abstract: The present study reports on high-flux, low-energy He{sup +} ion irradiation as a novel method of enhancing the surface porosity and surface area of naturally oxidized niobium (Nb). Our study shows that ion-irradiation-induced Nb surface micro- and nano-structures are highly tunable by varying the target temperature during ion bombardment. Mirror-polished Nb samples were irradiated with 100 eV He{sup +} ions at a flux of 1.2 × 10{sup 21} ions m{sup −2} s{sup −1} to a total fluence of 4.3 × 10{sup 24} ions m{sup −2} with simultaneous sample annealing in the temperature range of 773–1223 K to demonstrate the influence of sample temperature on the resulting Nb surface morphology. This surface morphology was primarily characterized using field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). Below 923 K, Nb surfaces form nano-scale tendrils and exhibit significant increases in surface porosity. Above 923 K, homogeneously populated nano-pores with an average diameter of ∼60 nm are observed in addition to a smaller population of sub-micron sized pores (up to ∼230 nm in diameter). Our analysis shows a significant reduction in surface pore number density and surface porosity with increasing sample temperature. High-resolution ex situ X-ray photoelectron spectroscopy (XPS) shows Nb{sub 2}O{sub 5} phase in all of the ion-irradiated samples. To further demonstrate the length scales in which radiation-induced surface roughening occurs, optical reflectivity was performed over a spectrum of

  7. Heat flux distribution on an optimised limiter surface and structure of the scrape-off-layer

    International Nuclear Information System (INIS)

    Denner, T.

    1998-12-01

    The heat load on plasma-facing components is a key issue for forthcoming fusion experiments. In this work the heat flux on the pump limiter in TEXTOR-94 is measured by a newly developed digital thermography system and these results are compared with theoretical models. The limiter is shaped in such a way as to keep the heat load of the plasma-wetted area low; this is achieved by reducing the angle of incidence of the magnetic field lines with respect to the limiter surface to less than 1 for the first 10 mm of the scrape-off-layer (SOL). This small angle of incidence enhances all effects of toroidal non-uniformity as given e.g. by the magnetic field ripple. Extensive modelling explains well the observed heating pattern on the limiter surface due to the ripple effect. In contrast to expectations from density and temperature distributions in the SOL and at the edge of the confined region, an excessive power density is deposited on the first few millimetres near the roof tip of the limiter. Physical effects which could cause this phenomenon are discussed. (orig.)

  8. Ideal flux field dielectric concentrators.

    Science.gov (United States)

    García-Botella, Angel

    2011-10-01

    The concept of the vector flux field was first introduced as a photometrical theory and later developed in the field of nonimaging optics; it has provided new perspectives in the design of concentrators, overcoming standard ray tracing techniques. The flux field method has shown that reflective concentrators with the geometry of the field lines achieve the theoretical limit of concentration. In this paper we study the role of surfaces orthogonal to the field vector J. For rotationally symmetric systems J is orthogonal to its curl, and then a family of surfaces orthogonal to the lines of J exists, which can be called the family of surfaces of constant pseudopotential. Using the concept of the flux tube, it is possible to demonstrate that refractive concentrators with the shape of these pseudopotential surfaces achieve the theoretical limit of concentration.

  9. Discrepancies between soft x-ray emissivity contours and magnetic flux surfaces in Alcator C-Mod

    International Nuclear Information System (INIS)

    Borras, M.C.; Granetz, R.S.

    1996-01-01

    The soft x-ray diagnostic system of Alcator C-Mod, equipped with 152 detectors distributed in four arrays, is used to obtain iso-emissivity surfaces. These surfaces have been characterized by giving their elongation and relative shift from the centre of the tokamak as functions of plasma radius. Flux surfaces, provided by magnetic diagnostics, have also been described with elongation and shift. Results from the comparison of the two sets of geometric parameters obtained from magnetic and x-ray diagnostics are presented. We find that, whereas the shifts obtained from these two diagnostic methods are always in good agreement, the corresponding elongation curves show different patterns. An agreement between elongations better than 2% is only found in a range of about 2 cm in minor radius. On the other hand, the elongations can differ by 10% towards the plasma edge and the plasma centre. Error bars for the x-ray diagnostic are obtained by propagating the effect of ± 1% random errors at the detector signals, and can amount to ± 1-2% of the estimated values near the edge and the centre of the plasma. The estimated uncertainties in the determination of elongation from magnetic flux surfaces are of the order of 4%. A series of tests and simulations performed to verify the accuracy of the X-ray diagnostic system is presented. The discrepancies found could imply the existence of asymmetries in impurity concentration. (Author)

  10. Proceedings of US/Japan workshop, Q219 on high heat flux components and plasma surface interactions for next fusion devices

    Energy Technology Data Exchange (ETDEWEB)

    Ulrickson, M.A.; Stevens, P.L.; Hino, T.; Hirohata, Y. [eds.

    1996-12-01

    This report contains the viewgraphs from the proceedings of US/Japan Workshop on High Heat Flux Components and Plasma Surface Interactions for Next Fusion Devices. Some of the general topics covered by this report are: PFC/PSI in tokamak and helical devices; development of high heat flux components; PSIS and plasma facing materials;tritium; and material damage.

  11. Proceedings of US/Japan workshop, Q219 on high heat flux components and plasma surface interactions for next fusion devices

    International Nuclear Information System (INIS)

    Ulrickson, M.A.; Stevens, P.L.; Hino, T.; Hirohata, Y.

    1996-12-01

    This report contains the viewgraphs from the proceedings of US/Japan Workshop on High Heat Flux Components and Plasma Surface Interactions for Next Fusion Devices. Some of the general topics covered by this report are: PFC/PSI in tokamak and helical devices; development of high heat flux components; PSIS and plasma facing materials;tritium; and material damage

  12. Comparison between Evapotranspiration Fluxes Assessment Methods

    Science.gov (United States)

    Casola, A.; Longobardi, A.; Villani, P.

    2009-11-01

    Knowledge of hydrological processes acting in the water balance is determinant for a rational water resources management plan. Among these, the water losses as vapour, in the form of evapotranspiration, play an important role in the water balance and the heat transfers between the land surface and the atmosphere. Mass and energy interactions between soil, atmosphere and vegetation, in fact, influence all hydrological processes modificating rainfall interception, infiltration, evapotraspiration, surface runoff and groundwater recharge.A numbers of methods have been developed in scientific literature for modelling evapotranspiration. They can be divided in three main groups: i) traditional meteorological models, ii) energy fluxes balance models, considering interaction between vegetation and the atmosphere, and iii) remote sensing based models. The present analysis preliminary performs a study of fluxes directions and an evaluation of energy balance closure in a typical Mediterranean short vegetation area, using data series recorded from an eddy covariance station, located in the Campania region, Southern Italy. The analysis was performed on different seasons of the year with the aim to assess climatic forcing features impact on fluxes balance, to evaluate the smaller imbalance and to highlight influencing factors and sampling errors on balance closure. The present study also concerns evapotranspiration fluxes assessment at the point scale. Evapotranspiration is evaluated both from empirical relationships (Penmann-Montheit, Penmann F AO, Prestley&Taylor) calibrated with measured energy fluxes at mentioned experimental site, and from measured latent heat data scaled by the latent heat of vaporization. These results are compared with traditional and reliable well known models at the plot scale (Coutagne, Turc, Thorthwaite).

  13. The Effect of Growth Temperature and V/III Flux Ratio of MOCVD Antimony Based Semiconductors on Growth Rate and Surface Morphology

    Directory of Open Access Journals (Sweden)

    Ramelan Ari Handono

    2017-01-01

    Full Text Available Epitaxial Alx Ga1-x Sb layers on GaSb and GaAs substrates have been grown by atmospheric pressure metalorganic chemical vapor deposition using TMAl, TMGa and TMSb. Nomarski microscope and a profiler were employed to examine the surface morphology and growth rate of the samples. We report the effect of growth temperature and V/III flux ratio on growth rate and surface morphology. Growth temperatures in the range of 520°C and 680°C and V/III ratios from 1 to 5 have been investigated. A growth rate activation energy of 0.73 eV was found. At low growth temperatures between 520 and 540°C, the surface morphology is poor due to antimonide precipitates associated with incomplete decomposition of the TMSb. For layers grown on GaAs at 580°C and 600°C with a V/III ratio of 3 a high quality surface morphology is typical, with a mirror-like surface and good composition control. It was found that a suitable growth temperature and V/III flux ratio was beneficial for producing good AlGaSb layers. Undoped AlGaSb grown at 580°C with a V/III flux ratio of 3 at the rate of 3.5 μm/hour shows p-type conductivity with smooth surface morphology

  14. Modeling energy fluxes in heterogeneous landscapes employing a mosaic approach

    Science.gov (United States)

    Klein, Christian; Thieme, Christoph; Priesack, Eckart

    2015-04-01

    Recent studies show that uncertainties in regional and global climate and weather simulations are partly due to inadequate descriptions of the energy flux exchanges between the land surface and the atmosphere. One major shortcoming is the limitation of the grid-cell resolution, which is recommended to be about at least 3x3 km² in most models due to limitations in the model physics. To represent each individual grid cell most models select one dominant soil type and one dominant land use type. This resolution, however, is often too coarse in regions where the spatial diversity of soil and land use types are high, e.g. in Central Europe. An elegant method to avoid the shortcoming of grid cell resolution is the so called mosaic approach. This approach is part of the recently developed ecosystem model framework Expert-N 5.0. The aim of this study was to analyze the impact of the characteristics of two managed fields, planted with winter wheat and potato, on the near surface soil moistures and on the near surface energy flux exchanges of the soil-plant-atmosphere interface. The simulated energy fluxes were compared with eddy flux tower measurements between the respective fields at the research farm Scheyern, North-West of Munich, Germany. To perform these simulations, we coupled the ecosystem model Expert-N 5.0 to an analytical footprint model. The coupled model system has the ability to calculate the mixing ratio of the surface energy fluxes at a given point within one grid cell (in this case at the flux tower between the two fields). This approach accounts for the differences of the two soil types, of land use managements, and of canopy properties due to footprint size dynamics. Our preliminary simulation results show that a mosaic approach can improve modeling and analyzing energy fluxes when the land surface is heterogeneous. In this case our applied method is a promising approach to extend weather and climate models on the regional and on the global scale.

  15. Magnetotail Reconnection and Flux Circulation: Jupiter and Saturn Compared

    Science.gov (United States)

    Jackman, C. M.; Vogt, M. F.; Slavin, J. A.; Cowley, S. W. H.; Boardsen, S. A.

    2011-01-01

    The Jovian magnetosphere has been visited by eight spacecraft, and the magnetometer data have been used to identify dozens of plasmoids and 250 field dipolarizations associated with magnetic reconnection in the tail [e.g. Vogt et al., 2010]. Since the arrival of the Cassini spacecraft at Saturn in 2004, the magnetometer instrument has also been used to identify reconnection signatures. The deepest magnetotail orbits were in 2006, and during this time 34 signatures of plasmoids were identified. In this study we compare the statistical properties of plasmoids at Jupiter and Saturn such as duration, size, location, and recurrence period. Such parameters can be influenced by many factors, including the different Dungey cycle timescales and cross-magnetospheric potential drops at the two planets. We present superposed epoch analyses of plasmoids at the two planets to determine their average properties and to infer their role in the reconfiguration of the nightside of the magnetosphere. We examine the contributions of plasmoids to the magnetic flux transfer cycle at both planets. At Jupiter, there is evidence of an extended interval after reconnection where the field remains northward (analogous to the terrestrial post-plasmoid plasma sheet). At Saturn we see a similar feature, and calculate the amount of flux closed on average in reconnection events, leading us to an estimation of the recurrence rate of plasmoid release.

  16. Recovery Time After a Late-Dry Season Fire: the Effect on Fluxes, Surface Properties and Vegetation Green-Up.

    Science.gov (United States)

    Saha, M. V.; D'Odorico, P.; Scanlon, T. M.

    2014-12-01

    Large regions of Africa burn on an annual basis. These fires damage vegetation, change surface albedo and modify the hydrologic cycle. Quantifying the magnitude and persistence of these changes is key in understanding the complex ways in which fire affects ecosystem functioning at smaller scales and will inform ongoing modeling efforts. We report the results of a field study in a semi-arid savanna in northern Botswana during the transition from dry to wet season (Oct-Dec) in 2012 and 2013. The goals of this study were to: (1) characterize the multifaceted effect that late dry-season fires have on fluxes and radiative surface processes during green-up, and (2) describe the timescales over which these variables recover to non-burnt levels. Our study synthesizes a suite of data, including flux tower measurements, vegetation sampling, time-lapse photography and concurrent remotely sensed variables over plots with variable burn patterns. Albedo decreased immediately after fire, converging on unburned values 10 days post-burn. The magnitude and direction of this response was comparable to the albedo change elicited by strong rainfall events. Soil temperature and soil heat flux were not significantly modified by fire. Carbon fluxes showed no discernible difference from an unburned control site immediately after fire. There was a small burst in ecosystem respiration at immediately following the first post-fire rainfall event, returning to baseline values after 3 days. Persistent CO2 release, which we attribute to soil respiration, occurred for 10 days after successive strong wetting events, confirming the centrality of available moisture in determining ecosystem function. Fire delayed the green-up in some plots, but this effect was variable and short-lived. One month after fire there was no evidence of a difference in ground observations of greenness between burnt and control plots or plots that differed in their time of burning. We attribute the relatively ephemeral

  17. Analysis of Water Vapour Flux Between Alpine Wetlands Underlying the Surface and Atmosphere in the Source Region of the Yellow River

    Science.gov (United States)

    Xie, Y.; Wen, J.; Liu, R.; Wang, X.; JIA, D.

    2017-12-01

    Wetland underlying surface is sensitive to climate change. Analysis of the degree of coupling between wetlands and the atmosphere and a quantitative assessment of how environmental factors influence latent heat flux have considerable scientific significance. Previous studies, which focused on the forest, grassland and farmland ecosystems, lack research on the alpine wetlands. In addition, research on the environmental control mechanism of latent heat flux is still qualitative and lacks quantitative evaluations and calculations. Using data from the observational tests of the Maduo Observatory of Climate and Environment of the Northwest Institute of Eco-Environment and Resource, CAS, from June 1 to August 31, 2014, this study analysed the time-varying characteristics and causes of the degree of coupling between alpine wetlands underlying surface and the atmosphere and quantitatively calculated the influences of different environmental factors (solar radiation and vapour pressure deficit) on latent heat flux. The results were as follows: Due to the diurnal variations of solar radiation and wind speed, the diurnal variations of the Ω factor present a trend in which the Ω factor are small in the morning and large in the evening. Due to the vegetation growing cycle, the seasonal variations of the Ω factor present a reverse "U" trend . These trends are similar to the diurnal and seasonal variations of the absolute control exercised by solar radiation over the latent heat flux. This conforms to omega theory. The values for average absolute atmospheric factor (surface factor or total ) control exercised by solar radiation and water vapour pressure are 0.20 (0.02 or 0.22 ) and 0.005 (-0.07 or -0.06) W·m-2·Pa-1, respectively.. Generally speaking, solar radiation and water vapour pressure deficit exert opposite forces on the latent heat flux. The average Ω factor is high during the vegetation growing season, with a value of 0.38, and the degree of coupling between the

  18. Experimental investigation of pool boiling heat transfer and critical heat flux on a downward facing surface

    International Nuclear Information System (INIS)

    Gocmanac, M.; Luxat, J.C.

    2012-01-01

    A separate effects experimental study of heat transfer and Critical Heat Flux (CHF) on a downward facing plate in subcooled water pool boiling is described. Two geometries of downwards facing surfaces are studied. The first is termed the 'confined' study in which bubble motion is restricted to the heated surface. The second is termed the 'unconfined' study where individual bubbles are free to move along the heated surface and vent in any direction. The method used in the confined study is novel and involves the placement of a lip surrounding the heated surface. The CHF as a function of angle of inclination of the surface is presented and is in good agreement with other experimental data from somewhat different test geometries. (author)

  19. Modelling of surface fluxes and Urban Boundary Layer over an old mediterannean city core

    Science.gov (United States)

    Lemonsu, A.; Masson, V.; Grimmond, Cs. B.

    2003-04-01

    In the frameworks of the UBL(Urban Boundary Layer)-ESCOMPTE campaign, the Town Energy Balance (TEB) model was run in off-line mode for Marseille. TEB's performance is evaluated with observations of surface temperatures and surface energy balance fluxes collected during the campaign. Parameterization improvements allow to better represent the energy exchanges between the air inside the canyon and the atmosphere above the roof level. Then, high resolution Méso-NH simulations are done to study the 3-D structure and the evolution of the Urban Boundary Layer (UBL) over Marseille. Will will give a special attention to the impact of the seabord effects (sea-breeze circulation) on the UBL.

  20. Continental-scale water fluxes from continuous GPS observations of Earth surface loading

    Science.gov (United States)

    Borsa, A. A.; Agnew, D. C.; Cayan, D. R.

    2015-12-01

    After more than a decade of observing annual oscillations of Earth's surface from seasonal snow and water loading, continuous GPS is now being used to model time-varying terrestrial water fluxes on the local and regional scale. Although the largest signal is typically due to the seasonal hydrological cycle, GPS can also measure subtle surface deformation caused by sustained wet and dry periods, and to estimate the spatial distribution of the underlying terrestrial water storage changes. The next frontier is expanding this analysis to the continental scale and paving the way for incorporating GPS models into the National Climate Assessment and into the observational infrastructure for national water resource management. This will require reconciling GPS observations with predictions from hydrological models and with remote sensing observations from a suite of satellite instruments (e.g. GRACE, SMAP, SWOT). The elastic Earth response which transforms surface loads into vertical and horizontal displacements is also responsible for the contamination of loading observations by tectonic and anthropogenic transients, and we discuss these and other challenges to this new application of GPS.

  1. Wind tunnel experiments on the effects of tillage ridge features on wind erosion horizontal fluxes

    Directory of Open Access Journals (Sweden)

    M. Kardous

    2005-11-01

    Full Text Available In addition to the well-known soil factors which control wind erosion on flat, unridged surfaces, two specific processes affect the susceptibility of tillage ridged surfaces to wind erosion: ridge-induced roughness and ridge- trapping efficiency. In order to parameterize horizontal soil fluxes produced by wind over tillage ridges, eight-ridge configurations composed of sandy soil and exhibiting ridge heights to ridge spacing (RH/RS ratios ranging from 0.18 to 0.38 were experimented in a wind tunnel. These experiments are used to develop a parameterization of the horizontal fluxes over tillage ridged surfaces based only on the geometric characteristics of the ridges. Indeed, the key parameters controlling the horizontal flux, namely the friction velocity, threshold friction velocity and the adjustment coefficient, are derived through specific expressions, from ridge heights (RH and ridge spacing (RS. This parameterization was evaluated by comparing the results of the simulations to an additional experimental data set and to the data set obtained by Hagen and Armbrust (1992. In both cases, predicted and measured values are found to be in a satisfying agreement. This parameterization was used to evaluate the efficiency of ridges in reducing wind erosion. The results show that ridged surfaces, when compared to a loose, unridged soil surface, lead to an important reduction in the horizontal fluxes (exceeding 60%. Moreover, the effect of ridges in trapping particles contributes for more than 90% in the flux reduction while the ridge roughness effect is weak and decreases when the wind velocity increases.

  2. Surface Turbulent Fluxes, 1x1 deg Daily Grid, Set1 V2c (GSSTF) at GES DISC

    Data.gov (United States)

    National Aeronautics and Space Administration — These data are the Goddard Satellite-based Surface Turbulent Fluxes Version-2c (GSSTF2c) Dataset recently produced through a MEaSUREs funded project led by Dr....

  3. Seasonal variability of the temperature and heat fluxes in the Gulf of Mexico

    OpenAIRE

    ZAVALA-HIDALGO, J.; PARÉS-SIERRA, A.; OCHOA, J.

    2002-01-01

    Heat fluxes between the atmosphere and the sea surface in the Gulf of Mexico are computed using the COADS climatology, bulk formulae, radiation estimations from satellite, and a numerical model. 9 W m-2 is the estimated mean surface heat flux into the ocean, this is higher than previous studies due to different bulk formulae and data sources. The annual cycle has an amplitude of 168 W m-2. The contribution of each term in the heat equation is computed, analyzed and compared to previous studie...

  4. Comparison of surface freshwater fluxes from different climate forecasts produced through different ensemble generation schemes.

    Science.gov (United States)

    Romanova, Vanya; Hense, Andreas; Wahl, Sabrina; Brune, Sebastian; Baehr, Johanna

    2016-04-01

    The decadal variability and its predictability of the surface net freshwater fluxes is compared in a set of retrospective predictions, all using the same model setup, and only differing in the implemented ocean initialisation method and ensemble generation method. The basic aim is to deduce the differences between the initialization/ensemble generation methods in view of the uncertainty of the verifying observational data sets. The analysis will give an approximation of the uncertainties of the net freshwater fluxes, which up to now appear to be one of the most uncertain products in observational data and model outputs. All ensemble generation methods are implemented into the MPI-ESM earth system model in the framework of the ongoing MiKlip project (www.fona-miklip.de). Hindcast experiments are initialised annually between 2000-2004, and from each start year 10 ensemble members are initialized for 5 years each. Four different ensemble generation methods are compared: (i) a method based on the Anomaly Transform method (Romanova and Hense, 2015) in which the initial oceanic perturbations represent orthogonal and balanced anomaly structures in space and time and between the variables taken from a control run, (ii) one-day-lagged ocean states from the MPI-ESM-LR baseline system (iii) one-day-lagged of ocean and atmospheric states with preceding full-field nudging to re-analysis in both the atmospheric and the oceanic component of the system - the baseline one MPI-ESM-LR system, (iv) an Ensemble Kalman Filter (EnKF) implemented into oceanic part of MPI-ESM (Brune et al. 2015), assimilating monthly subsurface oceanic temperature and salinity (EN3) using the Parallel Data Assimilation Framework (PDAF). The hindcasts are evaluated probabilistically using fresh water flux data sets from four different reanalysis data sets: MERRA, NCEP-R1, GFDL ocean reanalysis and GECCO2. The assessments show no clear differences in the evaluations scores on regional scales. However, on the

  5. Stress state of transversally isotropic body with elliptical crack in the presence of a uniform heat flux at its surface

    International Nuclear Information System (INIS)

    Podil'chuk, Yu.N.

    1995-01-01

    An explicit solution of the state thermoelasticity problem is constructed for an infinite transversally isotropic body containing an internal elliptical crack in the isotropy plane. It is assumed that a uniform heat flux is specified at the crack surface and the body is free of external loads. Values of the stress-intensity coefficients depending on the heat flux, the crack dimensions, and the thermoelastic properties of the material are obtained. Note that the analogous problem was considered for an isotropic body. The static thermoelasticity problem for a transversally isotropic body with an internal elliptical crack at whose surface linear temperature variation is specified was solved

  6. Turbine blade and vane heat flux sensor development, phase 2

    Science.gov (United States)

    Atkinson, W. H.; Cyr, M. A.; Strange, R. R.

    1985-01-01

    The development of heat flux sensors for gas turbine blades and vanes and the demonstration of heat transfer measurement methods are reported. The performance of the heat flux sensors was evaluated in a cylinder in cross flow experiment and compared with two other heat flux measurement methods, the slug calorimeter and a dynamic method based on fluctuating gas and surface temperature. Two cylinders, each instrumented with an embedded thermocouple sensor, a Gardon gauge, and a slug calorimeter, were fabricated. Each sensor type was calibrated using a quartz lamp bank facility. The instrumented cylinders were then tested in an atmospheric pressure combustor rig at conditions up to gas stream temperatures of 1700K and velocities to Mach 0.74. The test data are compared to other measurements and analytical prediction.

  7. The importance of wind-flux feedbacks during the November CINDY-DYNAMO MJO event

    Science.gov (United States)

    Riley Dellaripa, Emily; Maloney, Eric; van den Heever, Susan

    2015-04-01

    High-resolution, large-domain cloud resolving model (CRM) simulations probing the importance of wind-flux feedbacks to Madden-Julian Oscillation (MJO) convection are performed for the November 2011 CINDY-DYNAMO MJO event. The work is motivated by observational analysis from RAMA buoys in the Indian Ocean and TRMM precipitation retrievals that show a positive correlation between MJO precipitation and wind-induced surface fluxes, especially latent heat fluxes, during and beyond the CINDY-DYNAMO time period. Simulations are done using Colorado State University's Regional Atmospheric Modeling System (RAMS). The domain setup is oceanic and spans 1000 km x 1000 km with 1.5 km horizontal resolution and 65 stretched vertical levels centered on the location of Gan Island - one of the major CINDY-DYNAMO observation points. The model is initialized with ECMWF reanalysis and Aqua MODIS sea surface temperatures. Nudging from ECMWF reanalysis is applied at the domain periphery to encourage realistic evolution of MJO convection. The control experiment is run for the entire month of November so both suppressed and active, as well as, transitional phases of the MJO are modeled. In the control experiment, wind-induced surface fluxes are activated through the surface bulk aerodynamic formula and allowed to evolve organically. Sensitivity experiments are done by restarting the control run one week into the simulation and controlling the wind-induced flux feedbacks. In one sensitivity experiment, wind-induced surface flux feedbacks are completely denied, while in another experiment the winds are kept constant at the control simulations mean surface wind speed. The evolution of convection, especially on the mesoscale, is compared between the control and sensitivity simulations.

  8. Modeling the large-scale effects of surface moisture heterogeneity on wetland carbon fluxes in the West Siberian Lowland

    Directory of Open Access Journals (Sweden)

    T. J. Bohn

    2013-10-01

    Full Text Available We used a process-based model to examine the role of spatial heterogeneity of surface and sub-surface water on the carbon budget of the wetlands of the West Siberian Lowland over the period 1948–2010. We found that, while surface heterogeneity (fractional saturated area had little overall effect on estimates of the region's carbon fluxes, sub-surface heterogeneity (spatial variations in water table depth played an important role in both the overall magnitude and spatial distribution of estimates of the region's carbon fluxes. In particular, to reproduce the spatial pattern of CH4 emissions recorded by intensive in situ observations across the domain, in which very little CH4 is emitted north of 60° N, it was necessary to (a account for CH4 emissions from unsaturated wetlands and (b use spatially varying methane model parameters that reduced estimated CH4 emissions in the northern (permafrost half of the domain (and/or account for lower CH4 emissions under inundated conditions. Our results suggest that previous estimates of the response of these wetlands to thawing permafrost may have overestimated future increases in methane emissions in the permafrost zone.

  9. Application of Relaxed Eddy Accumulation (REA) method to estimate CO2 and CH4 surface fluxes in the city of Krakow, southern Poland.

    Science.gov (United States)

    Zimnoch, Miroslaw; Gorczyca, Zbigniew; Pieniazek, Katarzyna; Jasek, Alina; Chmura, Lukasz; Rozanski, Kazimierz

    2013-04-01

    There is a growing interest in the recent years in studies aimed at quantifying carbon cycling in urban centres. Worldwide migration of human population from rural to urban areas and corresponding growth of extensive urban agglomerations and megacities leads to intensification of anthropogenic emissions of carbon and strong disruption of natural carbon cycle on these areas. Therefore, a deeper understanding of the carbon "metabolism" of such regions is required. Apart of better quantification of surface carbon fluxes, also a thorough understanding of the functioning of biosphere under strong anthropogenic influence is needed. Nowadays, covariance methods are widely applied for studying gas exchange between the atmosphere and the Earth's surface. Relaxed Eddy Accumulation method (REA), combined with the CO2 and CH4 CRDS analyser allows simultaneous measurements of surface fluxes of carbon dioxide and methane within the chosen footprint of the detection system, thus making possible thorough characterisation of the overall exchange of those gases between the atmosphere and the urban surface across diverse spatial and temporal scales. Here we present preliminary results of the study aimed at quantifying surface fluxes of CO2 and CH4 in Krakow, southern Poland. The REA system for CO2 and CH4 flux measurements has been installed on top of a 20m high tower mounted on the roof of the faculty building, close to the city centre of Krakow. The sensors were installed ca 42 m above the local ground. Gill Windmaster-Pro sonic anemometer was coupled with self-made system, designed by the Poznan University of Life Sciences, Poland, for collecting air samples in two pairs of 10-liter Tedlar bags, and with Picarro G2101-i CRDS analyser. The air was collected in 30-min intervals. The CO2 and CH4 mixing ratios in these cumulative downdraft and updraft air samples were determined by the CRDS analyser after each sampling interval. Based on the measured mixing ratios difference and the

  10. Using a thermal-based two source energy balance model with time-differencing to estimate surface energy fluxes with day-night MODIS observations

    DEFF Research Database (Denmark)

    Guzinski, Radoslaw; Anderson, M.C.; Kustas, W.P.

    2013-01-01

    The Dual Temperature Difference (DTD) model, introduced by Norman et al. (2000), uses a two source energy balance modelling scheme driven by remotely sensed observations of diurnal changes in land surface temperature (LST) to estimate surface energy fluxes. By using a time-differential temperature...... agreement with field measurements is obtained for a number of ecosystems in Denmark and the United States. Finally, regional maps of energy fluxes are produced for the Danish Hydrological ObsErvatory (HOBE) in western Denmark, indicating realistic patterns based on land use....

  11. Diurnal Variations of the Flux Imbalance Over Homogeneous and Heterogeneous Landscapes

    Science.gov (United States)

    Zhou, Yanzhao; Li, Dan; Liu, Heping; Li, Xin

    2018-05-01

    It is well known that the sum of the turbulent sensible and latent heat fluxes as measured by the eddy-covariance method is systematically lower than the available energy (i.e., the net radiation minus the ground heat flux). We examine the separate and joint effects of diurnal and spatial variations of surface temperature on this flux imbalance in a dry convective boundary layer using the Weather Research and Forecasting model. Results show that, over homogeneous surfaces, the flux due to turbulent-organized structures is responsible for the imbalance, whereas over heterogeneous surfaces, the flux due to mesoscale or secondary circulations is the main contributor to the imbalance. Over homogeneous surfaces, the flux imbalance in free convective conditions exhibits a clear diurnal cycle, showing that the flux-imbalance magnitude slowly decreases during the morning period and rapidly increases during the afternoon period. However, in shear convective conditions, the flux-imbalance magnitude is much smaller, but slightly increases with time. The flux imbalance over heterogeneous surfaces exhibits a diurnal cycle under both free and shear convective conditions, which is similar to that over homogeneous surfaces in free convective conditions, and is also consistent with the general trend in the global observations. The rapid increase in the flux-imbalance magnitude during the afternoon period is mainly caused by the afternoon decay of the turbulent kinetic energy (TKE). Interestingly, over heterogeneous surfaces, the flux imbalance is linearly related to the TKE and the difference between the potential temperature and surface temperature, ΔT; the larger the TKE and ΔT values, the smaller the flux-imbalance magnitude.

  12. Effect of Energetic Plasma Flux on Flowing Liquid Lithium Surfaces

    Science.gov (United States)

    Kalathiparambil, Kishor; Jung, Soonwook; Christenson, Michael; Fiflis, Peter; Xu, Wenyu; Szott, Mathew; Ruzic, David

    2014-10-01

    An operational liquid lithium system with steady state flow driven by thermo-electric magneto-hydrodynamic force and capable of constantly refreshing the plasma exposed surface have been demonstrated at U of I. To evaluate the system performance in reactor relevant conditions, specifically to understand the effect of disruptive plasma events on the performance of the liquid metal PFCs, the setup was integrated to a pulsed plasma generator. A coaxial plasma generator drives the plasma towards a theta pinch which preferentially heats the ions, simulating ELM like flux, and the plasma is further guided towards the target chamber which houses the flowing lithium system. The effect of the incident flux is examined using diagnostic tools including triple Langmuir probe, calorimeter, rogowski coils, Ion energy analyzers, and fast frame spectral image acquisition with specific optical filters. The plasma have been well characterized and a density of ~1021 m-3, with electron temperature ~10 - 20 eV is measured, and final plasma velocities of 34 - 74 kms-1 have been observed. Calorimetric measurements using planar molybdenum targets indicate a maximum plasma energy (with 6 kV plasma gun and 20 kV theta pinch) of 0.08 MJm-2 with plasma divergence effects resulting in marginal reduction of 40 +/- 23 J in plasma energy. Further results from the other diagnostic tools, using the flowing lithium targets and the planar targets coated with lithium will be presented. DOE DE-SC0008587.

  13. Studying temporal and spatial variations of groundwater-surface water exchange flux for the Slootbeek (Belgium) using the LPML method

    Science.gov (United States)

    Anibas, Christian; Schneideweind, Uwe; Vandersteen, Gerd; Huysmans, Marijke; Batelaan, Okke

    2015-04-01

    Knowledge of groundwater-surface water interaction is important for the assessment of water resources and for the investigation of fate and transport of contaminants and nutrients. In streams and rivers exchange fluxes of water are sensitive to local and regional factors such as riverbed hydraulic conductivity and hydraulic gradients. Field monitoring in time and space is therefore indispensible for assessing the variability of groundwater-surface water interaction. Not only the complexity of the examined processes demand novel data processing and characterization tools, the amount of acquired data also urges for new modeling tools. These tools should be easily applicable, allow for a fast computation, and utilize the maximum amount of available data for detailed analysis, including uncertainties. Such analytical tools should be combined with modern field equipment, data processing tools, geographical information systems and geostatistics for best results. A simple and cost effective methodology to estimate groundwater-surface water interaction is the use of temperature as an environmental tracer (ANDERSON, 2005). LPML (VANDERSTEEN et al., 2014) is one of the most advanced analytical 1D coupled water flow and heat transport models, combining a local polynomial method with a maximum likelihood estimator. It is flexible, fast and able to create time series of exchange fluxes, as well as model quality and parameter uncertainty. LPML determines frequency response functions from measured temperature time series and an analytical model, and applies a non-linear optimization technique. With this tool the variability of groundwater-surface water interaction of the Belgian stream Slootbeek was assessed. Multilevel temperature sensors were placed in seven locations to obtain temperature-time series. Located at the streambed top and at six depths below, several months worth of data was collected and analyzed. Results identified a high spatial and temporal variability of

  14. Carbon dioxide flux measurements from a coastal Douglas-fir forest floor

    International Nuclear Information System (INIS)

    Drewitt, G.B.

    2002-01-01

    This thesis examined the process that affects the exchange of carbon between the soil and the atmosphere with particular attention to the large amounts of carbon stored in soils in the form of decaying organic matter. This forest floor measuring study was conducted in 2000 at a micro-meteorological tower flux site in a coastal temperature Douglas-fir forest. The measuring study involved half hourly measurements of both carbon dioxide and below-ground carbon dioxide storage. Measurements were taken at 6 locations between April and December to include a large portion of the growing season. Eddy covariance (EC) measurements of carbon dioxide flux above the forest floor over a two month period in the summer and the autumn were compared with forest floor measurements. Below-ground carbon dioxide mixing ratios of soil air were measured at 6 depths between 0.02 to 1 m using gas diffusion probes and a syringe sampling method. Maximum carbon dioxide fluxes measured by the soil chambers varied by a factor of 3 and a high spatial variability in soil carbon dioxide flux was noted. Forest floor carbon dioxide fluxes measured by each of the chambers indicated different sensitivities to soil temperature. Hysteresis in the flux temperature relationship over the year was evident. Reliable below-canopy EC measurements of the forest floor carbon dioxide flux were difficult to obtain because of the every low wind speeds below the forest canopy. The amount of carbon dioxde present in the soil increased rapidly with depth near the surface but less rapidly deeper in the soil. It was suggested that approximately half of the carbon dioxide produced below-ground comes from between the soil surface and the first 0.15 m of depth. Carbon dioxide fluxes from the floor of a Douglas-fir forest were found to be large compared to other, less productive ecosystems

  15. Eddy covariance flux measurements of gaseous elemental mercury using cavity ring-down spectroscopy.

    Science.gov (United States)

    Pierce, Ashley M; Moore, Christopher W; Wohlfahrt, Georg; Hörtnagl, Lukas; Kljun, Natascha; Obrist, Daniel

    2015-02-03

    A newly developed pulsed cavity ring-down spectroscopy (CRDS) system for measuring atmospheric gaseous elemental mercury (GEM) concentrations at high temporal resolution (25 Hz) was used to successfully conduct the first eddy covariance (EC) flux measurements of GEM. GEM is the main gaseous atmospheric form, and quantification of bidirectional exchange between the Earth's surface and the atmosphere is important because gas exchange is important on a global scale. For example, surface GEM emissions from natural sources, legacy emissions, and re-emission of previously deposited anthropogenic pollution may exceed direct primary anthropogenic emissions. Using the EC technique for flux measurements requires subsecond measurements, which so far has not been feasible because of the slow time response of available instrumentation. The CRDS system measured GEM fluxes, which were compared to fluxes measured with the modified Bowen ratio (MBR) and a dynamic flux chamber (DFC). Measurements took place near Reno, NV, in September and October 2012 encompassing natural, low-mercury (Hg) background soils and Hg-enriched soils. During nine days of measurements with deployment of Hg-enriched soil in boxes within 60 m upwind of the EC tower, the covariance of GEM concentration and vertical wind speed was measured, showing that EC fluxes over an Hg-enriched area were detectable. During three separate days of flux measurements over background soils (without Hg-enriched soils), no covariance was detected, indicating fluxes below the detection limit. When fluxes were measurable, they strongly correlated with wind direction; the highest fluxes occurred when winds originated from the Hg-enriched area. Comparisons among the three methods showed good agreement in direction (e.g., emission or deposition) and magnitude, especially when measured fluxes originated within the Hg-enriched soil area. EC fluxes averaged 849 ng m(-2) h(-1), compared to DFC fluxes of 1105 ng m(-2) h(-1) and MBR fluxes

  16. Flux Trapping Properties of Bulk HIGH-TC Superconductors in Static Field-Cooling Magnetization

    Science.gov (United States)

    Deng, Z.; Tsuzuki, K.; Miki, M.; Felder, B.; Hara, S.; Izumi, M.

    2013-06-01

    The trapping process and saturation effect of trapped magnetic flux of bulk high-temperature superconductors by static field-cooling magnetization (FCM) are reported in the paper. With a cryogenic Bell Hall sensor attached on the center of the bulk surface, the synchronous magnetic signals were recorded during the whole magnetization process. It enables us to know the flux trapping behavior since the removal of the excitation field, as well as the subsequent flux relaxation phenomenon and the flux dissipation in the quench process of the bulk sample. With the help of flux mapping techniques, the relationship between the trapped flux and the applied field was further investigated; the saturation effect of trapped flux was discussed by comparing the peak trapped field and total magnetic flux of the bulk sample. These studies are useful to understand the basic flux trapping properties of bulk superconductors.

  17. Nocturnal soil CO2 uptake and its relationship to sub-surface soil and ecosystem carbon fluxes in a Chihuahuan Desert shrubland

    Science.gov (United States)

    Despite their prevalence, little attention has been given to quantifying aridland soil and ecosystem carbon fluxes over prolonged, annually occurring dry periods. We measured surface soil respiration (Rsoil), volumetric soil moisture and temperature in inter- and under-canopy soils, sub-surface soi...

  18. Calculation with MCNP of capture photon flux in VVER-1000 experimental reactor.

    Science.gov (United States)

    Töre, Candan; Ortego, Pedro

    2005-01-01

    The aim of this study is to obtain by Monte Carlo method the high energy photon flux due to neutron capture in the internals and vessel layers of the experimental reactor LR-0 located in REZ, Czech Republic, and loaded with VVER-1000 fuel. The calclated neutron, photon and photon to neutron flux ratio are compared with experimental measurements performed with a multi-parameter stilbene detector. The results show clear underestimation of photon flux in downcomer and some overestimation at vessel surface and 1/4 thickness but a good fitting for deeper points in vessel.

  19. A simple mathematical procedure to estimate heat flux in machining using measured surface temperature with infrared laser

    Directory of Open Access Journals (Sweden)

    Hocine Mzad

    2015-09-01

    Full Text Available Several techniques have been developed over time for the measurement of heat and the temperatures generated in various manufacturing processes and tribological applications. Each technique has its own advantages and disadvantages. The appropriate technique for temperature measurement depends on the application under consideration as well as the available tools for measurement. This paper presents a procedure for a simple and accurate determination of the time-varying heat flux at the workpiece–tool interface of three different metals under known cutting conditions. A portable infrared thermometer is used for surface temperature measurements. A spline smoothing interpolation of the surface temperature history enables to determine the local heat flux produced during stock removal. The measured temperature is represented by a third-order spline approximation. Nonetheless, the accuracy of polynomial interpolation depends on how close are the interpolated points; an increase in degree cannot be used to increase the accuracy. Although the data analysis is relatively complicated, the computing time is very small.

  20. Using a thermal-based two source energy balance model with time-differencing to estimate surface energy fluxes with day-night MODIS observations

    Science.gov (United States)

    Guzinski, R.; Anderson, M. C.; Kustas, W. P.; Nieto, H.; Sandholt, I.

    2013-07-01

    The Dual Temperature Difference (DTD) model, introduced by Norman et al. (2000), uses a two source energy balance modelling scheme driven by remotely sensed observations of diurnal changes in land surface temperature (LST) to estimate surface energy fluxes. By using a time-differential temperature measurement as input, the approach reduces model sensitivity to errors in absolute temperature retrieval. The original formulation of the DTD required an early morning LST observation (approximately 1 h after sunrise) when surface fluxes are minimal, limiting application to data provided by geostationary satellites at sub-hourly temporal resolution. The DTD model has been applied primarily during the active growth phase of agricultural crops and rangeland vegetation grasses, and has not been rigorously evaluated during senescence or in forested ecosystems. In this paper we present modifications to the DTD model that enable applications using thermal observations from polar orbiting satellites, such as Terra and Aqua, with day and night overpass times over the area of interest. This allows the application of the DTD model in high latitude regions where large viewing angles preclude the use of geostationary satellites, and also exploits the higher spatial resolution provided by polar orbiting satellites. A method for estimating nocturnal surface fluxes and a scheme for estimating the fraction of green vegetation are developed and evaluated. Modification for green vegetation fraction leads to significantly improved estimation of the heat fluxes from the vegetation canopy during senescence and in forests. When the modified DTD model is run with LST measurements acquired with the Moderate Resolution Imaging Spectroradiometer (MODIS) on board the Terra and Aqua satellites, generally satisfactory agreement with field measurements is obtained for a number of ecosystems in Denmark and the United States. Finally, regional maps of energy fluxes are produced for the Danish

  1. Using a thermal-based two source energy balance model with time-differencing to estimate surface energy fluxes with day–night MODIS observations

    Directory of Open Access Journals (Sweden)

    R. Guzinski

    2013-07-01

    Full Text Available The Dual Temperature Difference (DTD model, introduced by Norman et al. (2000, uses a two source energy balance modelling scheme driven by remotely sensed observations of diurnal changes in land surface temperature (LST to estimate surface energy fluxes. By using a time-differential temperature measurement as input, the approach reduces model sensitivity to errors in absolute temperature retrieval. The original formulation of the DTD required an early morning LST observation (approximately 1 h after sunrise when surface fluxes are minimal, limiting application to data provided by geostationary satellites at sub-hourly temporal resolution. The DTD model has been applied primarily during the active growth phase of agricultural crops and rangeland vegetation grasses, and has not been rigorously evaluated during senescence or in forested ecosystems. In this paper we present modifications to the DTD model that enable applications using thermal observations from polar orbiting satellites, such as Terra and Aqua, with day and night overpass times over the area of interest. This allows the application of the DTD model in high latitude regions where large viewing angles preclude the use of geostationary satellites, and also exploits the higher spatial resolution provided by polar orbiting satellites. A method for estimating nocturnal surface fluxes and a scheme for estimating the fraction of green vegetation are developed and evaluated. Modification for green vegetation fraction leads to significantly improved estimation of the heat fluxes from the vegetation canopy during senescence and in forests. When the modified DTD model is run with LST measurements acquired with the Moderate Resolution Imaging Spectroradiometer (MODIS on board the Terra and Aqua satellites, generally satisfactory agreement with field measurements is obtained for a number of ecosystems in Denmark and the United States. Finally, regional maps of energy fluxes are produced for the

  2. Wind tunnel experiments on the effects of tillage ridge features on wind erosion horizontal fluxes

    Directory of Open Access Journals (Sweden)

    M. Kardous

    2005-11-01

    Full Text Available In addition to the well-known soil factors which control wind erosion on flat, unridged surfaces, two specific processes affect the susceptibility of tillage ridged surfaces to wind erosion: ridge-induced roughness and ridge- trapping efficiency.

    In order to parameterize horizontal soil fluxes produced by wind over tillage ridges, eight-ridge configurations composed of sandy soil and exhibiting ridge heights to ridge spacing (RH/RS ratios ranging from 0.18 to 0.38 were experimented in a wind tunnel. These experiments are used to develop a parameterization of the horizontal fluxes over tillage ridged surfaces based only on the geometric characteristics of the ridges. Indeed, the key parameters controlling the horizontal flux, namely the friction velocity, threshold friction velocity and the adjustment coefficient, are derived through specific expressions, from ridge heights (RH and ridge spacing (RS. This parameterization was evaluated by comparing the results of the simulations to an additional experimental data set and to the data set obtained by Hagen and Armbrust (1992. In both cases, predicted and measured values are found to be in a satisfying agreement.

    This parameterization was used to evaluate the efficiency of ridges in reducing wind erosion. The results show that ridged surfaces, when compared to a loose, unridged soil surface, lead to an important reduction in the horizontal fluxes (exceeding 60%. Moreover, the effect of ridges in trapping particles contributes for more than 90% in the flux reduction while the ridge roughness effect is weak and decreases when the wind velocity increases.

  3. Reviews and syntheses: An empirical spatiotemporal description of the global surface-atmosphere carbon fluxes: opportunities and data limitations

    Science.gov (United States)

    Zscheischler, Jakob; Mahecha, Miguel D.; Avitabile, Valerio; Calle, Leonardo; Carvalhais, Nuno; Ciais, Philippe; Gans, Fabian; Gruber, Nicolas; Hartmann, Jens; Herold, Martin; Ichii, Kazuhito; Jung, Martin; Landschützer, Peter; Laruelle, Goulven G.; Lauerwald, Ronny; Papale, Dario; Peylin, Philippe; Poulter, Benjamin; Ray, Deepak; Regnier, Pierre; Rödenbeck, Christian; Roman-Cuesta, Rosa M.; Schwalm, Christopher; Tramontana, Gianluca; Tyukavina, Alexandra; Valentini, Riccardo; van der Werf, Guido; West, Tristram O.; Wolf, Julie E.; Reichstein, Markus

    2017-08-01

    Understanding the global carbon (C) cycle is of crucial importance to map current and future climate dynamics relative to global environmental change. A full characterization of C cycling requires detailed information on spatiotemporal patterns of surface-atmosphere fluxes. However, relevant C cycle observations are highly variable in their coverage and reporting standards. Especially problematic is the lack of integration of the carbon dioxide (CO2) exchange of the ocean, inland freshwaters and the land surface with the atmosphere. Here we adopt a data-driven approach to synthesize a wide range of observation-based spatially explicit surface-atmosphere CO2 fluxes from 2001 to 2010, to identify the state of today's observational opportunities and data limitations. The considered fluxes include net exchange of open oceans, continental shelves, estuaries, rivers, and lakes, as well as CO2 fluxes related to net ecosystem productivity, fire emissions, loss of tropical aboveground C, harvested wood and crops, as well as fossil fuel and cement emissions. Spatially explicit CO2 fluxes are obtained through geostatistical and/or remote-sensing-based upscaling, thereby minimizing biophysical or biogeochemical assumptions encoded in process-based models. We estimate a bottom-up net C exchange (NCE) between the surface (land, ocean, and coastal areas) and the atmosphere. Though we provide also global estimates, the primary goal of this study is to identify key uncertainties and observational shortcomings that need to be prioritized in the expansion of in situ observatories. Uncertainties for NCE and its components are derived using resampling. In many regions, our NCE estimates agree well with independent estimates from other sources such as process-based models and atmospheric inversions. This holds for Europe (mean ± 1 SD: 0.8 ± 0.1 PgC yr-1, positive numbers are sources to the atmosphere), Russia (0.1 ± 0.4 PgC yr-1), East Asia (1.6 ± 0.3 PgC yr-1), South Asia (0.3 ± 0

  4. MERRA 2D IAU Diagnostic, Surface Fluxes, Diurnal (2/3x1/2L1) V5.2.0

    Data.gov (United States)

    National Aeronautics and Space Administration — The MATUNXFLX or tavgU_2d_flx_Nx data product is the MERRA Data Assimilation System 2-Dimensional surface turbulence flux diagnostic that is time averaged...

  5. Magnetic flux tubes and transport of heat in the convection zone of the sun

    International Nuclear Information System (INIS)

    Spruit, H.C.

    1977-01-01

    This thesis consists of five papers dealing with transport of heat in the solar convection zone on the one hand, and with the structure of magnetic flux tubes in the top of the convection zone on the other hand. These subjects are interrelated. For example, the heat flow in the convection zone is disturbed by the presence of magnetic flux tubes, while exchange of heat between a flux tube and the convection zone is important for the energy balance of such a tube. A major part of this thesis deals with the structure of small magnetic flux tubes. Such small tubes (diameters less than about 2'') carry most of the flux appearing at the solar surface. An attempt is made to construct models of the surface layers of such small tubes in sufficient detail to make a comparison with observations possible. Underlying these model calculations is the assumption that the magnetic elements at the solar surface are flux tubes in a roughly static equilibrium. The structure of such tubes is governed by their pressure equilibrium, exchange of heat with the surroundings, and transport of heat by some modified form of convection along the tube. The tube models calculated are compared with observations

  6. One-dimensional critical heat flux concerning surface orientation and gap size effects

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yong Hoon; Suh, Kune Y. E-mail: kysuh@snu.ac.kr

    2003-12-01

    Tests were conducted to examine the critical heat flux (CHF) on a one-dimensional downward heating rectangular channel having a narrow gap by changing the orientation of the copper test heater assembly in a pool of saturated water under atmospheric pressure. The test parameters include both the gap sizes of 1, 2, 5 and 10 mm, and the surface orientation angles from the downward-facing position (180 deg.) to the vertical position (90 deg.), respectively. Also, the CHF experiments were performed for pool boiling with varying heater surface orientations in the unconfined space at atmospheric pressure using the rectangular test section. It was observed that the CHF generally decreases as the surface inclination angle increases and as the gap size decreases. In consistency with several studies reported in the literature, it was found that there exists a transition angle at which the CHF changes with a rapid slope. An engineering correlation is developed for the CHF during natural convective boiling in the inclined, confined rectangular channels with the aid of dimensional analysis. This correlation agrees with the experimental data of this study within {+-}20%.

  7. Buoyancy effects laminar slot jet impinging on a surface with constant heat flux

    International Nuclear Information System (INIS)

    Shokouhmand, H.; Esfahanian, V.; Masoodi, R.

    2004-01-01

    The two-dimensional laminar air jet issuing from a nozzle of half which terminates at height above a flat plate normal to the jet is numerically on the flow and thermal structure of the region near impingement. The impinging surface is maintained at a constant heat flux condition. The full Navier-Stocks and energy equations are solved by a finite difference method to evaluate the velocity profiles and temperature distribution. The governing parameters and their ranges are: Reynolds number Re, 10-50, Grashof number Gr, 0-50, Richardson number Ri=Gr/ Re 2 , Non dimensional nozzle height H,2-3. Results of the free streamline, local friction factor and heat transfer coefficient are graphically presented. It is found that enhancement of the heat transfer rate is substantial for high Richardson number conditions. Although the laminar jet impingement for isothermal condition has been already studied, however the constant heat flux has not been studied enough. the present paper will analyze a low velocity air jet, Which can be used for cooling of a simulated electronics package

  8. Effect of spectrally varying albedo of vegetation surfaces on shortwave radiation fluxes and aerosol direct radiative forcing

    Directory of Open Access Journals (Sweden)

    L. Zhu

    2012-12-01

    Full Text Available This study develops an algorithm for representing detailed spectral features of vegetation albedo based on Moderate Resolution Imaging Spectrometer (MODIS observations at 7 discrete channels, referred to as the MODIS Enhanced Vegetation Albedo (MEVA algorithm. The MEVA algorithm empirically fills spectral gaps around the vegetation red edge near 0.7 μm and vegetation water absorption features at 1.48 and 1.92 μm which cannot be adequately captured by the MODIS 7 channels. We then assess the effects of applying MEVA in comparison to four other traditional approaches to calculate solar fluxes and aerosol direct radiative forcing (DRF at the top of atmosphere (TOA based on the MODIS discrete reflectance bands. By comparing the DRF results obtained through the MEVA method with the results obtained through the other four traditional approaches, we show that filling the spectral gap of the MODIS measurements around 0.7 μm based on the general spectral behavior of healthy green vegetation leads to significant improvement in the instantaneous aerosol DRF at TOA (up to 3.02 W m−2 difference or 48% fraction of the aerosol DRF, −6.28 W m−2, calculated for high spectral resolution surface reflectance from 0.3 to 2.5 μm for deciduous vegetation surface. The corrections of the spectral gaps in the vegetation spectrum in the near infrared, again missed by the MODIS reflectances, also contributes to improving TOA DRF calculations but to a much lower extent (less than 0.27 W m−2, or about 4% of the instantaneous DRF.

    Compared to traditional approaches, MEVA also improves the accuracy of the outgoing solar flux between 0.3 to 2.5 μm at TOA by over 60 W m−2 (for aspen 3 surface and aerosol DRF by over 10 W m−2 (for dry grass. Specifically, for Amazon vegetation types, MEVA can improve the accuracy of daily averaged aerosol radiative forcing in the spectral range of 0.3 to 2.5 μm at

  9. Tissue responses to fractional transient heating with sinusoidal heat flux condition on skin surface.

    Science.gov (United States)

    Ezzat, Magdy A; El-Bary, Alaa A; Al-Sowayan, Noorah S

    2016-10-01

    A fractional model of Bioheat equation for describing quantitatively the thermal responses of skin tissue under sinusoidal heat flux conditions on skin surface is given. Laplace transform technique is used to obtain the solution in a closed form. The resulting formulation is applied to one-dimensional application to investigate the temperature distribution in skin with instantaneous surface heating for different cases. According to the numerical results and its graphs, conclusion about the fractional bioheat transfer equation has been constructed. Sensitivity analysis is performed to explore the thermal effects of various control parameters on tissue temperature. The comparisons are made with the results obtained in the case of the absence of time-fractional order. © 2016 Japanese Society of Animal Science. © 2016 Japanese Society of Animal Science.

  10. Calibration of Ocean Forcing with satellite Flux Estimates (COFFEE)

    Science.gov (United States)

    Barron, Charlie; Jan, Dastugue; Jackie, May; Rowley, Clark; Smith, Scott; Spence, Peter; Gremes-Cordero, Silvia

    2016-04-01

    Predicting the evolution of ocean temperature in regional ocean models depends on estimates of surface heat fluxes and upper-ocean processes over the forecast period. Within the COFFEE project (Calibration of Ocean Forcing with satellite Flux Estimates, real-time satellite observations are used to estimate shortwave, longwave, sensible, and latent air-sea heat flux corrections to a background estimate from the prior day's regional or global model forecast. These satellite-corrected fluxes are used to prepare a corrected ocean hindcast and to estimate flux error covariances to project the heat flux corrections for a 3-5 day forecast. In this way, satellite remote sensing is applied to not only inform the initial ocean state but also to mitigate errors in surface heat flux and model representations affecting the distribution of heat in the upper ocean. While traditional assimilation of sea surface temperature (SST) observations re-centers ocean models at the start of each forecast cycle, COFFEE endeavors to appropriately partition and reduce among various surface heat flux and ocean dynamics sources. A suite of experiments in the southern California Current demonstrates a range of COFFEE capabilities, showing the impact on forecast error relative to a baseline three-dimensional variational (3DVAR) assimilation using operational global or regional atmospheric forcing. Experiment cases combine different levels of flux calibration with assimilation alternatives. The cases use the original fluxes, apply full satellite corrections during the forecast period, or extend hindcast corrections into the forecast period. Assimilation is either baseline 3DVAR or standard strong-constraint 4DVAR, with work proceeding to add a 4DVAR expanded to include a weak constraint treatment of the surface flux errors. Covariance of flux errors is estimated from the recent time series of forecast and calibrated flux terms. While the California Current examples are shown, the approach is

  11. Quantifying the drivers of ocean-atmosphere CO2 fluxes

    Science.gov (United States)

    Lauderdale, Jonathan M.; Dutkiewicz, Stephanie; Williams, Richard G.; Follows, Michael J.

    2016-07-01

    A mechanistic framework for quantitatively mapping the regional drivers of air-sea CO2 fluxes at a global scale is developed. The framework evaluates the interplay between (1) surface heat and freshwater fluxes that influence the potential saturated carbon concentration, which depends on changes in sea surface temperature, salinity and alkalinity, (2) a residual, disequilibrium flux influenced by upwelling and entrainment of remineralized carbon- and nutrient-rich waters from the ocean interior, as well as rapid subduction of surface waters, (3) carbon uptake and export by biological activity as both soft tissue and carbonate, and (4) the effect on surface carbon concentrations due to freshwater precipitation or evaporation. In a steady state simulation of a coarse-resolution ocean circulation and biogeochemistry model, the sum of the individually determined components is close to the known total flux of the simulation. The leading order balance, identified in different dynamical regimes, is between the CO2 fluxes driven by surface heat fluxes and a combination of biologically driven carbon uptake and disequilibrium-driven carbon outgassing. The framework is still able to reconstruct simulated fluxes when evaluated using monthly averaged data and takes a form that can be applied consistently in models of different complexity and observations of the ocean. In this way, the framework may reveal differences in the balance of drivers acting across an ensemble of climate model simulations or be applied to an analysis and interpretation of the observed, real-world air-sea flux of CO2.

  12. Interactions of bluff-body obstacles with turbulent airflows affecting evaporative fluxes from porous surfaces

    Science.gov (United States)

    Haghighi, Erfan; Or, Dani

    2015-11-01

    Bluff-body obstacles interacting with turbulent airflows are common in many natural and engineering applications (from desert pavement and shrubs over natural surfaces to cylindrical elements in compact heat exchangers). Even with obstacles of simple geometry, their interactions within turbulent airflows result in a complex and unsteady flow field that affects surface drag partitioning and transport of scalars from adjacent evaporating surfaces. Observations of spatio-temporal thermal patterns on evaporating porous surfaces adjacent to bluff-body obstacles depict well-defined and persistent zonation of evaporation rates that were used to construct a simple mechanistic model for surface-turbulence interactions. Results from evaporative drying of sand surfaces with isolated cylindrical elements (bluff bodies) subjected to constant turbulent airflows were in good agreement with model predictions for localized exchange rates. Experimental and theoretical results show persistent enhancement of evaporative fluxes from bluff-rough surfaces relative to smooth flat surfaces under similar conditions. The enhancement is attributed to formation of vortices that induce a thinner boundary layer over part of the interacting surface footprint. For a practical range of air velocities (0.5-4.0 m/s), low-aspect ratio cylindrical bluff elements placed on evaporating sand surfaces enhanced evaporative mass losses (relative to a flat surface) by up to 300% for high density of elements and high wind velocity, similar to observations reported in the literature. Concepts from drag partitioning were used to generalize the model and upscale predictions to evaporation from surfaces with multiple obstacles for potential applications to natural bluff-rough surfaces.

  13. Soil methane and CO2 fluxes in rainforest and rubber plantations

    Science.gov (United States)

    Lang, Rong; Blagodatsky, Sergey; Goldberg, Stefanie; Xu, Jianchu

    2017-04-01

    Expansion of rubber plantations in South-East Asia has been a land use transformation trend leading to losses of natural forest cover in the region. Besides impact on ecosystem carbon stocks, this conversion influences the dynamics of greenhouse gas fluxes from soil driven by microbial activity, which has been insufficiently studied. Aimed to understand how land use change affects the soil CO2 and CH4 fluxes, we measured surface gas fluxes, gas concentration gradient, and 13C signature in CH4 and soil organic matter in profiles in a transect in Xishuangbanna, including a rainforest site and three rubber plantation sites with age gradient. Gas fluxes were measured by static chamber method and open chamber respiration system. Soil gases were sampled from installed gas samplers at 5, 10, 30, and 75cm depth at representative time in dry and rainy season. The soil CO2 flux was comparable in rainforest and old rubber plantations, while young rubber plantation had the lowest rate. Total carbon content in the surface soil well explained the difference of soil CO2 flux between sites. All sites were CH4 sinks in dry season and uptake decreased in the order of rainforest, old rubber plantations and young rubber plantation. From dry season to rainy season, CH4 consumption decreased with increasing CH4 concentration in the soil profile at all depths. The enrichment of methane by 13CH4 shifted towards to lowerδ13C, being the evidence of enhanced CH4 production process while net surface methane flux reflected the consumption in wet condition. Increment of CH4 concentration in the profile from dry to rainy season was higher in old rubber plantation compared to rainforest, while the shifting of δ13CH4 was larger in rainforest than rubber sites. Turnover rates of soil CO2 and CH4 suggested that the 0-5 cm surface soil was the most active layer for gaseous carbon exchange. δ13C in soil organic matter and soil moisture increased from rainforest, young rubber plantation to old

  14. Planktic foraminifer and coccolith contribution to carbonate export fluxes over the central Kerguelen Plateau

    Science.gov (United States)

    Rembauville, M.; Meilland, J.; Ziveri, P.; Schiebel, R.; Blain, S.; Salter, I.

    2016-05-01

    We report the contribution of planktic foraminifers and coccoliths to the particulate inorganic carbon (PIC) export fluxes collected over an annual cycle (October 2011/September 2012) on the central Kerguelen Plateau in the Antarctic Zone (AAZ) south of the Polar Front (PF). The seasonality of PIC flux was decoupled from surface chlorophyll a concentration and particulate organic carbon (POC) fluxes and was characterized by a late summer (February) maximum. This peak was concomitant with the highest satellite-derived sea surface PIC and corresponded to a Emiliania huxleyi coccoliths export event that accounted for 85% of the annual PIC export. The foraminifer contribution to the annual PIC flux was much lower (15%) and dominated by Turborotalita quinqueloba and Neogloboquadrina pachyderma. Foraminifer export fluxes were closely related to the surface chlorophyll a concentration, suggesting food availability as an important factor regulating the foraminifer's biomass. We compared size-normalized test weight (SNW) of the foraminifers with previously published SNW from the Crozet Islands using the same methodology and found no significant difference in SNW between sites for a given species. However, the SNW was significantly species-specific with a threefold increase from T. quinqueloba to Globigerina bulloides. The annual PIC:POC molar ratio of 0.07 was close to the mean ratio for the global ocean and lead to a low carbonate counter pump effect (~5%) compared to a previous study north of the PF (6-32%). We suggest that lowers counter pump effect south of the PF despite similar productivity levels is due to a dominance of coccoliths in the PIC fluxes and a difference in the foraminifers species assemblage with a predominance of polar species with lower SNW.

  15. Pyrolytic graphite gauge for measuring heat flux

    Science.gov (United States)

    Bunker, Robert C. (Inventor); Ewing, Mark E. (Inventor); Shipley, John L. (Inventor)

    2002-01-01

    A gauge for measuring heat flux, especially heat flux encountered in a high temperature environment, is provided. The gauge includes at least one thermocouple and an anisotropic pyrolytic graphite body that covers at least part of, and optionally encases the thermocouple. Heat flux is incident on the anisotropic pyrolytic graphite body by arranging the gauge so that the gauge surface on which convective and radiative fluxes are incident is perpendicular to the basal planes of the pyrolytic graphite. The conductivity of the pyrolytic graphite permits energy, transferred into the pyrolytic graphite body in the form of heat flux on the incident (or facing) surface, to be quickly distributed through the entire pyrolytic graphite body, resulting in small substantially instantaneous temperature gradients. Temperature changes to the body can thereby be measured by the thermocouple, and reduced to quantify the heat flux incident to the body.

  16. Neutralized wettability effect of superhydrophilic Cr-layered surface on pool boiling critical heat flux

    International Nuclear Information System (INIS)

    Son, Hong Hyun; Jeong, Ui Ju; Seo, Gwang Hyeok; Jeun, Gyoo Dong; Kim, Sung Joong

    2016-01-01

    The former method is deemed challenging due to longer development period and license issue. In this regard, FeCrAl, Cr, and SiC have been received positive attention as ATF coating materials because they are highly resistant to high temperature steam reaction causing massive hydrogen generation. In this study, Cr was selected as a target deposition material on the metal substrate because we found that Cr-layered surface becomes superhydrophilic, favorable to delaying the triggering of the critical heat flux (CHF). Thus in order to investigate the effect of Cr-layered superhydrophilic surfaces (under explored coating conditions) on pool boiling heat transfer, pool boiling experiment was conducted in the saturated deionized water under atmospheric pressure. As a physical vapor deposition (PVD) method, the DC magnetron sputtering technique was introduced to develop Cr-layered nanostructure. As a control variable of DC sputtering, substrate temperature was selected. Surface wettability and nanostructure were analyzed as major surface parameters on the CHF. We believe that highly dense micro/nano structure without nucleation cavities and inner pores neutralized the wettability effect on the CHF. Moreover, superhydrophilic surface with deficient cavity density rather hinders active nucleation. This emphasizes the importance of micro/nano structure surface for enhanced boiling heat transfer.

  17. The NASA Carbon Airborne Flux Experiment (CARAFE): instrumentation and methodology

    Science.gov (United States)

    Wolfe, Glenn M.; Kawa, S. Randy; Hanisco, Thomas F.; Hannun, Reem A.; Newman, Paul A.; Swanson, Andrew; Bailey, Steve; Barrick, John; Thornhill, K. Lee; Diskin, Glenn; DiGangi, Josh; Nowak, John B.; Sorenson, Carl; Bland, Geoffrey; Yungel, James K.; Swenson, Craig A.

    2018-03-01

    The exchange of trace gases between the Earth's surface and atmosphere strongly influences atmospheric composition. Airborne eddy covariance can quantify surface fluxes at local to regional scales (1-1000 km), potentially helping to bridge gaps between top-down and bottom-up flux estimates and offering novel insights into biophysical and biogeochemical processes. The NASA Carbon Airborne Flux Experiment (CARAFE) utilizes the NASA C-23 Sherpa aircraft with a suite of commercial and custom instrumentation to acquire fluxes of carbon dioxide, methane, sensible heat, and latent heat at high spatial resolution. Key components of the CARAFE payload are described, including the meteorological, greenhouse gas, water vapor, and surface imaging systems. Continuous wavelet transforms deliver spatially resolved fluxes along aircraft flight tracks. Flux analysis methodology is discussed in depth, with special emphasis on quantification of uncertainties. Typical uncertainties in derived surface fluxes are 40-90 % for a nominal resolution of 2 km or 16-35 % when averaged over a full leg (typically 30-40 km). CARAFE has successfully flown two missions in the eastern US in 2016 and 2017, quantifying fluxes over forest, cropland, wetlands, and water. Preliminary results from these campaigns are presented to highlight the performance of this system.

  18. Calculation of the dependence on the Moon and Mars γ-quantum flux on the relief and distance to the surface

    International Nuclear Information System (INIS)

    Surkov, Yu.A.; Noskaleva, L.P.; Manvelyan, O.S.

    1978-01-01

    The dependence of the gamma quantum flux on height over a planet, area over which the gamma radiation is ''collected'', and surface relief is calculated. The effect of the planet atmosphere on detected gamma radiation is considered. If the specific power of gamma-quantum sources is known, the results obtained allow to determine for any height over a planet the gamma-quantum flux due to the planet rock and its atmosphere radiations, as well as the detector spatial resolution

  19. Microtopography and methane flux in boreal peatlands, northern Ontario, Canada

    International Nuclear Information System (INIS)

    Bubier, J.; Costello, A.; Moore, T.R.; Roulet, N.T.; Savage, K.

    1993-01-01

    Peatlands act as a major sink of carbon dioxide and a source of methane. Fluxes of methane were measured by a static chamber technique at hummock, hollow, and lawn microtopographic locations in 12 peatland sites near Cochrane, northern Ontario, from May to October 1991. Average fluxes (mg/m 2 /d) were 2.3 at hummocks, 44.4 at hollows, and 15.6 at lawns. Methane flux was negatively correlated with average water table position based on the 36 locations, with hummocks having a smaller flux than hollows or lawns, where the water table depth was <25 cm. Peat samples from a bog hummock and hollow failed to produce methane during anaerobic incubations in the laboratory; samples from a poor fen hollow produced <1.4 μg/g/d. The production decreased with depth but was greater than the rates observed during incubation of samples from an adjacent hummock. Rates of methane consumption during aerobic incubations ranged from 1 to 55 μg/g/d and were greatest in the surface layers and decreased with depth. Differences in methane emissions between hummocks and hollows appear to be controlled primarily by greater methane production rates in hollows compared with hummocks. Of secondary importance are the capacity of the peat profiles to consume methane during its transport to the peat surface and warmer temperatures at the water table beneath hollows compared with hummocks. 29 refs., 4 figs., 2 tabs

  20. Heat flux microsensor measurements and calibrations

    Science.gov (United States)

    Terrell, James P.; Hager, Jon M.; Onishi, Shinzo; Diller, Thomas E.

    1992-01-01

    A new thin-film heat flux gage has been fabricated specifically for severe high temperature operation using platinum and platinum-10 percent rhodium for the thermocouple elements. Radiation calibrations of this gage were performed at the AEDC facility over the available heat flux range (approx. 1.0 - 1,000 W/cu cm). The gage output was linear with heat flux with a slight increase in sensitivity with increasing surface temperature. Survivability of gages was demonstrated in quench tests from 500 C into liquid nitrogen. Successful operation of gages to surface temperatures of 750 C has been achieved. No additional cooling of the gages is required because the gages are always at the same temperature as the substrate material. A video of oxyacetylene flame tests with real-time heat flux and temperature output is available.

  1. Gas-particle interactions above a Dutch heathland: I. Surface exchange fluxes of NH3, SO2, HNO3 and HCl

    Directory of Open Access Journals (Sweden)

    E. Nemitz

    2004-01-01

    Full Text Available A field measurement campaign was carried out over a Dutch heathland to investigate the effect of gas-to-particle conversion and ammonium aerosol evaporation on surface/atmosphere fluxes of ammonia and related species. Continuous micrometeorological measurements of the surface exchange of NH3, SO2, HNO3 and HCl were made and are analyzed here with regard to average fluxes, deposition velocities (Vd, canopy resistances (Rc and canopy compensation point for NH3. Gradients of SO2, HNO3 and HCl were measured with a novel wet-denuder system with online anion chromatography. Measurements of HNO3 and HCl indicate an Rc of 100 to 200 s m-1 during warm daytime periods, probably at least partly due to non-zero acid partial pressures above NH4NO3 and NH4Cl on the leaf surfaces. Although it is likely that this observation is exacerbated by the effect of the evaporation of airborne NH4+ on the gradient measurements, the findings nevertheless add to the growing evidence that HNO3 and HCl are not always deposited at the maximum rate. Ammonia (NH3 fluxes show mainly deposition, with some periods of significant daytime emission. The net exchange could be reproduced both with an Rc model (deposition fluxes only using resistance parameterizations from former measurements, as well as with the canopy compensation point model, using parameterizations derived from the measurements. The apoplastic ratio of ammonium and hydrogen concentration (Γs=[NH4+]/[H+] of 1200 estimated from the measurements is large for semi-natural vegetation, but smaller than indicated by previous measurements at this site.

  2. Gas-particle interactions above a Dutch heathland: I. Surface exchange fluxes of NH3, SO2, HNO3 and HCl

    Science.gov (United States)

    Nemitz, E.; Sutton, M. A.; Wyers, G. P.; Jongejan, P. A. C.

    2004-07-01

    A field measurement campaign was carried out over a Dutch heathland to investigate the effect of gas-to-particle conversion and ammonium aerosol evaporation on surface/atmosphere fluxes of ammonia and related species. Continuous micrometeorological measurements of the surface exchange of NH3, SO2, HNO3 and HCl were made and are analyzed here with regard to average fluxes, deposition velocities (Vd), canopy resistances (Rc) and canopy compensation point for NH3. Gradients of SO2, HNO3 and HCl were measured with a novel wet-denuder system with online anion chromatography. Measurements of HNO3 and HCl indicate an Rc of 100 to 200 s m-1 during warm daytime periods, probably at least partly due to non-zero acid partial pressures above NH4NO3 and NH4Cl on the leaf surfaces. Although it is likely that this observation is exacerbated by the effect of the evaporation of airborne NH4+ on the gradient measurements, the findings nevertheless add to the growing evidence that HNO3 and HCl are not always deposited at the maximum rate. Ammonia (NH3) fluxes show mainly deposition, with some periods of significant daytime emission. The net exchange could be reproduced both with an Rc model (deposition fluxes only) using resistance parameterizations from former measurements, as well as with the canopy compensation point model, using parameterizations derived from the measurements. The apoplastic ratio of ammonium and hydrogen concentration (Γs=[NH4+]/[H+]) of 1200 estimated from the measurements is large for semi-natural vegetation, but smaller than indicated by previous measurements at this site.

  3. Seasonal contrast in the surface energy balance of the Sahel

    Science.gov (United States)

    Miller, R. L.; Slingo, A.; Barnard, J. C.; Kassianov, E.

    2009-07-01

    Over much of the world, heating of the surface by sunlight is balanced predominately by evaporative cooling. However, at the Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF) in Niamey, Niger, evaporation makes a significant contribution to the surface energy balance only at the height of the rainy season, when precipitation has replenished the reservoir of soil moisture. The AMF was placed at Niamey from late 2005 to early 2007 to provide measurements of surface fluxes in coordination with geostationary satellite retrievals of radiative fluxes at the top of the atmosphere, as part of the RADAGAST experiment to calculate atmospheric radiative divergence. We use observations at the mobile facility to investigate how the surface adjusts to radiative forcing throughout the year. The surface response to solar heating varies with changes in atmospheric water vapor associated with the seasonal reversal of the West African monsoon, which modulates the greenhouse effect and the ability of the surface to radiate thermal energy directly to space. During the dry season, sunlight is balanced mainly by longwave radiation and the turbulent flux of sensible heat. The ability of longwave radiation to cool the surface drops after the onset of southwesterly surface winds at Niamey, when moist, oceanic air flows onshore, increasing local column moisture and atmospheric opacity. Following the onset of southwesterly flow, evaporation remains limited by the supply of moisture from precipitation. By the height of the rainy season, however, sufficient precipitation has accumulated that evaporation is controlled by incident sunlight, and radiative forcing of the surface is balanced comparably by the latent, sensible, and longwave fluxes. Evaporation increases with the leaf area index, suggesting that plants are a significant source of atmospheric moisture and may tap moisture stored beneath the surface that accumulated during a previous rainy season. Surface radiative forcing

  4. Correlation between the critical heat flux and the fractal surface roughness of zirconium alloy tubes

    International Nuclear Information System (INIS)

    Fong, R.W.L.; McRae, G.A.; Coleman, C.E.; Nitheanandan, T.; Sanderson, D.B.

    1999-10-01

    In CANDU fuel channels, Zircaloy calandria tubes isolate the hot pressure tubes from the cool heavy water moderator. The heavy-water moderator provides a backup heat sink during some postulated loss-of-coolant accidents. The decay heat from the fuel is transferred to the moderator to ensure fuel channel integrity during emergencies. Moderator temperature requirements are specified to ensure that the transfer of decay heat does not exceed the critical heat flux (CHF) on the outside surface of the calandria tube. An enhanced CHF provides increases in safety margin. Pool boiling experiments indicate the CHF is enhanced with glass-peening of the outside surface of the calandria tubes. The objective of this study was to evaluate the surface characteristics of glass-peened tubes and relate these characteristics to CHF. The micro-topologies of the tube surfaces were analysed using stereo-pair micrographs obtained from scanning electron microscopy (SEM) and photogrammetry techniques. A linear relationship correlated the CHF as a function of the 'fractal' surface roughness of the tubes. (author)

  5. Temperature effect correction for muon flux at the Earth surface: estimation of the accuracy of different methods

    International Nuclear Information System (INIS)

    Dmitrieva, A N; Astapov, I I; Kovylyaeva, A A; Pankova, D V

    2013-01-01

    Correction of the muon flux at the Earth surface for temperature effect with the help of two simple methods is considered. In the first method, it is assumed that major part of muons are generated at some effective generation level, which altitude depends on the temperature profile of the atmosphere. In the second method, dependence of muon flux on the mass-averaged atmosphere temperature is considered. The methods were tested with the data of muon hodoscope URAGAN (Moscow, Russia). Difference between data corrected with the help of differential in altitude temperature coefficients and simplified methods does not exceed 1-1.5%, so the latter ones may be used for introduction of a fast preliminary correction.

  6. MERRA 2D IAU Diagnostic, Surface Fluxes, Monthly Mean (2/3x1/2L1) V5.2.0

    Data.gov (United States)

    National Aeronautics and Space Administration — The MATMNXFLX or tavgM_2d_flx_Nx data product is the MERRA Data Assimilation System 2-Dimensional surface turbulence flux diagnostic that is time averaged...

  7. Elucidating Carbon Exchange at the Regional Scale Via Airborne Eddy Covariance Flux Measurements

    Science.gov (United States)

    Hannun, R. A.; Wolfe, G. M.; Kawa, S. R.; Newman, P. A.; Hanisco, T. F.; Diskin, G. S.; DiGangi, J. P.; Nowak, J. B.; Barrick, J. D. W.; Thornhill, K. L., II; Noormets, A.; Vargas, R.; Clark, K. L.; Kustas, W. P.

    2017-12-01

    Direct flux observations from aircraft provide a unique tool for probing greenhouse gas (GHG) sources and sinks on a regional scale. Airborne eddy covariance, which relies on high-frequency, simultaneous measurements of fluctuations in concentration and vertical wind speed, is a robust method for quantifying surface-atmosphere exchange. We have assembled and flown an instrument payload onboard the NASA C-23 Sherpa aircraft capable of measuring CO2, CH4, H2O, and heat fluxes. Flights for the Carbon Airborne Flux Experiment (CARAFE) took place during September 2016 and May 2017 based out of Wallops Flight Facility, VA. Flight tracks covered a variety of ecosystems and land-use types in the Mid-Atlantic, including forests, croplands, and wetlands. Carbon fluxes are derived using eddy covariance and wavelet analysis. Our results show a strong drawdown of CO2 and near-zero CH4 emissions from crops and dry-land forest, but seasonally strong CH4 flux from wetland forest. CARAFE flux data will also be compared with observations from several flux towers along the flight path to complement the airborne measurements. We will further assess the effects of land surface type and seasonal variability in carbon exchange. Regional-scale flux observations from CARAFE supply a useful constraint for improving top-down and bottom up estimates of carbon sources and sinks.

  8. Analysis of the dual phase lag bio-heat transfer equation with constant and time-dependent heat flux conditions on skin surface

    Directory of Open Access Journals (Sweden)

    Ziaei Poor Hamed

    2016-01-01

    Full Text Available This article focuses on temperature response of skin tissue due to time-dependent surface heat fluxes. Analytical solution is constructed for DPL bio-heat transfer equation with constant, periodic and pulse train heat flux conditions on skin surface. Separation of variables and Duhamel’s theorem for a skin tissue as a finite domain are employed. The transient temperature responses for constant and time-dependent boundary conditions are obtained and discussed. The results show that there is major discrepancy between the predicted temperature of parabolic (Pennes bio-heat transfer, hyperbolic (thermal wave and DPL bio-heat transfer models when high heat flux accidents on the skin surface with a short duration or propagation speed of thermal wave is finite. The results illustrate that the DPL model reduces to the hyperbolic model when τT approaches zero and the classic Fourier model when both thermal relaxations approach zero. However for τq = τT the DPL model anticipates different temperature distribution with that predicted by the Pennes model. Such discrepancy is due to the blood perfusion term in energy equation. It is in contrast to results from the literature for pure conduction material, where the DPL model approaches the Fourier heat conduction model when τq = τT . The burn injury is also investigated.

  9. Heat flux from magmatic hydrothermal systems related to availability of fluid recharge

    Science.gov (United States)

    Harvey, M. C.; Rowland, J.V.; Chiodini, G.; Rissmann, C.F.; Bloomberg, S.; Hernandez, P.A.; Mazot, A.; Viveiros, F.; Werner, Cynthia A.

    2015-01-01

    Magmatic hydrothermal systems are of increasing interest as a renewable energy source. Surface heat flux indicates system resource potential, and can be inferred from soil CO2 flux measurements and fumarole gas chemistry. Here we compile and reanalyze results from previous CO2 flux surveys worldwide to compare heat flux from a variety of magma-hydrothermal areas. We infer that availability of water to recharge magmatic hydrothermal systems is correlated with heat flux. Recharge availability is in turn governed by permeability, structure, lithology, rainfall, topography, and perhaps unsurprisingly, proximity to a large supply of water such as the ocean. The relationship between recharge and heat flux interpreted by this study is consistent with recent numerical modeling that relates hydrothermal system heat output to rainfall catchment area. This result highlights the importance of recharge as a consideration when evaluating hydrothermal systems for electricity generation, and the utility of CO2 flux as a resource evaluation tool.

  10. Determining Adequate Averaging Periods and Reference Coordinates for Eddy Covariance Measurements of Surface Heat and Water Vapor Fluxes over Mountainous Terrain

    Directory of Open Access Journals (Sweden)

    Yi-Ying Chen Ming-Hsu Li

    2012-01-01

    Full Text Available Two coordinate rotation approaches (double and planar-fit rotations and no rotation, in association with averaging periods of 15 - 480 min, were applied to compute surface heat and water vapor fluxes using the eddy covariance approach. Measurements were conducted in an experimental watershed, the Lien-Hua-Chih (LHC watershed, located in central Taiwan. For no rotation and double rotation approaches, an adequate averaging period of 15 or 30 min was suggested for better energy closure and small variations on energy closure fractions. For the planar-fit rotation approach, an adequate averaging period of 60 or 120 min was recommended, and a typical averaging period of 30 min is not superior to that of 60 or 120 min in terms of better energy closure and small variations on energy closure fractions. The Ogive function analysis revealed that the energy closure was improved with the increase of averaging time by capturing sensible heat fluxes at low-frequency ranges during certain midday hours at LHC site. Seasonal variations of daily energy closure fractions, high in dry season and low in wet season, were found to be associated with the surface dryness and strength of turbulent development. The mismatching of flux footprint areas among flux sensors was suggested as the cause of larger CF variations during the dry seasons as that indicated by the footprint analysis showing scattered source areas. During the wet season, the underestimation of turbulent fluxes by EC observations at the LHC site was attributed to weak turbulence developments as the source area identified by the footprint analysis was closer to the flux tower than those scattered in dry season.

  11. Surface Turbulent Fluxes, 1x1 deg Yearly Climatology, Set1 and NCEP V2c (GSSTFYC) at GES DISC

    Data.gov (United States)

    National Aeronautics and Space Administration — These data are the Goddard Satellite-based Surface Turbulent Fluxes Version-2c Dataset recently produced through a MEaSURES funded project led by Dr. Chung-Lin Shie...

  12. Surface Turbulent Fluxes, 1x1 deg Monthly Climatology, Set1 and NCEP V2c (GSSTFMC) at GES DISC

    Data.gov (United States)

    National Aeronautics and Space Administration — These data are the Goddard Satellite-based Surface Turbulent Fluxes Version-2c Dataset recently produced through a MEaSURES funded project led by Dr. Chung-Lin Shie...

  13. The Response of the Ocean Thermal Skin Layer to Air-Sea Surface Heat Fluxes

    Science.gov (United States)

    Wong, Elizabeth Wing-See

    There is much evidence that the ocean is heating as a result of an increase in concentrations of greenhouse gases (GHGs) in the atmosphere from human activities. GHGs absorb infrared radiation and re-emit infrared radiation back to the ocean's surface which is subsequently absorbed. However, the incoming infrared radiation is absorbed within the top micrometers of the ocean's surface which is where the thermal skin layer exists. Thus the incident infrared radiation does not directly heat the upper few meters of the ocean. We are therefore motivated to investigate the physical mechanism between the absorption of infrared radiation and its effect on heat transfer at the air-sea boundary. The hypothesis is that since heat lost through the air-sea interface is controlled by the thermal skin layer, which is directly influenced by the absorption and emission of infrared radiation, the heat flow through the thermal skin layer adjusts to maintain the surface heat loss, assuming the surface heat loss does not vary, and thus modulates the upper ocean heat content. This hypothesis is investigated through utilizing clouds to represent an increase in incoming longwave radiation and analyzing retrieved thermal skin layer vertical temperature profiles from a shipboard infrared spectrometer from two research cruises. The data are limited to night-time, no precipitation and low winds of less than 2 m/s to remove effects of solar radiation, wind-driven shear and possibilities of thermal skin layer disruption. The results show independence of the turbulent fluxes and emitted radiation on the incident radiative fluxes which rules out the immediate release of heat from the absorption of the cloud infrared irradiance back into the atmosphere through processes such as evaporation and increase infrared emission. Furthermore, independence was confirmed between the incoming and outgoing radiative flux which implies the heat sink for upward flowing heat at the air-sea interface is more

  14. Burnout heat flux in natural flow boiling

    International Nuclear Information System (INIS)

    Helal, M.M.; Darwish, M.A.; Mahmoud, S.I.

    1978-01-01

    Twenty runs of experiments were conducted to determine the critical heat flux for natural flow boiling with water flowing upwards through annuli of centrally heated stainless steel tube. The test section has concentric heated tube of 14mm diameter and heated lengthes of 15 and 25 cm. The outside surface of the annulus was formed by various glass tubes of 17.25, 20 and 25.9mm diameter. System pressure is atmospheric. Inlet subcooling varied from 18 to 5 0 C. Obtained critical heat flux varied from 24.46 to 62.9 watts/cm 2 . A number of parameters having dominant influence on the critical heat flux and hydrodynamic instability (flow and pressure oscillations) preceeding the burnout have been studied. These parameters are mass flow rate, mass velocity, throttling, channel geometry (diameters ratio, length to diameter ratio, and test section length), and inlet subcooling. Flow regimes before and at the moments of burnout were observed, discussed, and compared with the existing physical model of burnout

  15. SPACETRAN, Radiation Leakage from Cylinder with ANISN Flux Calculation

    International Nuclear Information System (INIS)

    Cramer, S.N.; Solomito, M.

    1974-01-01

    1 - Nature of physical problem solved: SPACETRAN is designed to calculate the energy-dependent total flux or some proportional quantity such as kerma, due to the radiation leakage from the surface of a right-circular cylinder at detector positions located at arbitrary distances from the surface. The assumptions are made that the radiation emerging from the finite cylinder has no spatial dependence and that a vacuum surrounds the cylinder. 2 - Method of solution: There are three versions of the program in the code package. SPACETRAN-I uses the surface angular fluxes calculated by the discrete ordinates SN code ANISN, as input. SPACETRAN-II assumes that the surface angular flux for all energies can be represented as a function (Cos(PHI))**N, where PHI is the angle between surface outward normal and radiation direction, and N is an integer specified by the user. For both versions the energy group structure and the number and location of detectors is arbitrary. The flux (or response function) for a given energy group at some detection point is computed by summing the contributions from each surface area element over the entire surface. The surface area elements are defined by input data. SPACETRAN-III uses surface angular fluxes from DOT-3. SPACETRAN-I handles contributions either from a cylinder 'end' or 'side', so the total contributions must be obtained by adding the results of separate end and side runs. ANISN angular fluxes are specified for discrete directions. In general, the direction between the detector and contributing area will not exactly coincide with one of these discrete directions. In this case, the ANISN angular flux for the 'closest' discrete direction is used to approximate the contribution to the detector. SPACETRAN-II handles contributions from both the side and end of a cylinder in a single run. Since the assumed angular distribution is specified by a continuous function, it is not necessary to perform the angle selection described above. For

  16. The NASA Carbon Airborne Flux Experiment (CARAFE: instrumentation and methodology

    Directory of Open Access Journals (Sweden)

    G. M. Wolfe

    2018-03-01

    Full Text Available The exchange of trace gases between the Earth's surface and atmosphere strongly influences atmospheric composition. Airborne eddy covariance can quantify surface fluxes at local to regional scales (1–1000 km, potentially helping to bridge gaps between top-down and bottom-up flux estimates and offering novel insights into biophysical and biogeochemical processes. The NASA Carbon Airborne Flux Experiment (CARAFE utilizes the NASA C-23 Sherpa aircraft with a suite of commercial and custom instrumentation to acquire fluxes of carbon dioxide, methane, sensible heat, and latent heat at high spatial resolution. Key components of the CARAFE payload are described, including the meteorological, greenhouse gas, water vapor, and surface imaging systems. Continuous wavelet transforms deliver spatially resolved fluxes along aircraft flight tracks. Flux analysis methodology is discussed in depth, with special emphasis on quantification of uncertainties. Typical uncertainties in derived surface fluxes are 40–90 % for a nominal resolution of 2 km or 16–35 % when averaged over a full leg (typically 30–40 km. CARAFE has successfully flown two missions in the eastern US in 2016 and 2017, quantifying fluxes over forest, cropland, wetlands, and water. Preliminary results from these campaigns are presented to highlight the performance of this system.

  17. Uncertainties in surface mass and energy flux estimates due to different eddy covariance sensors and technical set-up

    Science.gov (United States)

    Arriga, Nicola; Fratini, Gerardo; Forgione, Antonio; Tomassucci, Michele; Papale, Dario

    2010-05-01

    Eddy covariance is a well established and widely used methodology for the measurement of turbulent fluxes of mass and energy in the atmospheric boundary layer, in particular to estimate CO2/H2O and heat exchange above ecologically relevant surfaces (Aubinet 2000, Baldocchi 2003). Despite its long term application and theoretical studies, many issues are still open about the effect of different experimental set-up on final flux estimates. Open issues are the evaluation of the performances of different kind of sensors (e.g. open path vs closed path infra-red gas analysers, vertical vs horizontal mounting ultrasonic anemometers), the quantification of the impact of corresponding physical corrections to be applied to get robust flux estimates taking in account all processes concurring to the measurement (e.g. the so-called WPL term, signal attenuation due to air sampling system for closed path analyser, relative position of analyser and anemometer) and the differences between several data transmission protocols used (analogue, digital RS-232, SDM). A field experiment was designed to study these issues using several instruments among those most used within the Fluxnet community and to compare their performances under conditions supposed to be critical: rainy and cold weather conditions for open-path analysers (Burba 2008), water transport and absorption at high air relative humidity conditions for closed-path systems (Ibrom, 2007), frequency sampling limits and recorded data robustness due to different transmission protocols (RS232, SDM, USB, Ethernet) and finally the effect of the displacement between anemometer and analyser using at least two identical analysers placed at different horizontal and vertical distances from the anemometer. Aim of this experiment is to quantify the effect of several technical solutions on the final estimates of fluxes measured at a point in the space and if they represent a significant source of uncertainty for mass and energy cycle

  18. Soil heat flux calculation for sunlit and shaded surfaces under row crops: 1 - Model Development and sensitivity analysis

    Science.gov (United States)

    Soil heat flux at the surface (G0) is strongly influenced by whether the soil is shaded or sunlit, and therefore can have large spatial variability for incomplete vegetation cover, such as across the interrows of row crops. Most practical soil-plant-atmosphere energy balance models calculate G0 as a...

  19. [Characteristics of water and heat fluxes and its footprint climatology on farmland in low hilly region of red soil].

    Science.gov (United States)

    Li, Yang; Jing, Yuan Shu; Qin, Ben Ben

    2017-01-01

    The analysis of the characteristics and footprint climatology of farmland water and heat fluxes has great significance to strengthen regional climate resource management and improve the hydrothermal resource utilization in the region of red soil. Based on quality controlled data from large aperture scintillometer and automatic meteorological station in hilly region of red soil, this paper analyzed in detail the characteristics of farmland water and heat fluxes at different temporal scales and the corresponding source area distribution of flux measurement in the non-rainy season and crop growth period in hilly region of red soil. The results showed that the diurnal variation of water and heat fluxes showed a unimodal trend, but compared with the sunny day, the diurnal variation curves fluctuated more complicatedly on cloudy day. In the whole, either ten-day periods or month scale, the water and heat fluxes were greater in August than in September, while the net radiation flux was more distributed to latent heat exchange. The proportion of net radiation to latent heat flux decreased in September compared to August, but the sensible heat flux was vice versa. With combined effects of weather conditions (particularly wind), stability, and surface condition, the source areas of flux measurement at different temporal scales showed different distribution characteristics. Combined with the underlying surface crops, the source areas at different temporal scales also had different contribution sources.

  20. Flux cutting in superconductors

    International Nuclear Information System (INIS)

    Campbell, A M

    2011-01-01

    This paper describes experiments and theories of flux cutting in superconductors. The use of the flux line picture in free space is discussed. In superconductors cutting can either be by means of flux at an angle to other layers of flux, as in longitudinal current experiments, or due to shearing of the vortex lattice as in grain boundaries in YBCO. Experiments on longitudinal currents can be interpreted in terms of flux rings penetrating axial lines. More physical models of flux cutting are discussed but all predict much larger flux cutting forces than are observed. Also, cutting is occurring at angles between vortices of about one millidegree which is hard to explain. The double critical state model and its developments are discussed in relation to experiments on crossed and rotating fields. A new experiment suggested by Clem gives more direct information. It shows that an elliptical yield surface of the critical state works well, but none of the theoretical proposals for determining the direction of E are universally applicable. It appears that, as soon as any flux flow takes place, cutting also occurs. The conclusion is that new theories are required. (perspective)

  1. Estimating carbon flux phenology with satellite-derived land surface phenology and climate drivers for different biomes: a synthesis of AmeriFlux observations.

    Directory of Open Access Journals (Sweden)

    Wenquan Zhu

    Full Text Available Carbon Flux Phenology (CFP can affect the interannual variation in Net Ecosystem Exchange (NEE of carbon between terrestrial ecosystems and the atmosphere. In this study, we proposed a methodology to estimate CFP metrics with satellite-derived Land Surface Phenology (LSP metrics and climate drivers for 4 biomes (i.e., deciduous broadleaf forest, evergreen needleleaf forest, grasslands and croplands, using 159 site-years of NEE and climate data from 32 AmeriFlux sites and MODIS vegetation index time-series data. LSP metrics combined with optimal climate drivers can explain the variability in Start of Carbon Uptake (SCU by more than 70% and End of Carbon Uptake (ECU by more than 60%. The Root Mean Square Error (RMSE of the estimations was within 8.5 days for both SCU and ECU. The estimation performance for this methodology was primarily dependent on the optimal combination of the LSP retrieval methods, the explanatory climate drivers, the biome types, and the specific CFP metric. This methodology has a potential for allowing extrapolation of CFP metrics for biomes with a distinct and detectable seasonal cycle over large areas, based on synoptic multi-temporal optical satellite data and climate data.

  2. A comparison of critical heat flux in tubes and bilaterally heated annuli

    Energy Technology Data Exchange (ETDEWEB)

    Doerffer, S.; Groeneveld, D.C.; Cheng, S.C. [Univ. of Ottawa (Canada)

    1995-09-01

    This paper examines the critical heat flux (CHF) behaviour for annular flow in bilaterally heated annuli and compares it to that in tubes and unilaterally heated annuli. It was found that the differences in CHF between bilaterally and unilaterally heated annuli or tubes strongly depend on pressure and quality. the CHF in bilaterally heated annuli can be predicted by tube CHF prediction methods for the simultaneous CHF occurrence at both surfaces, and the following flow conditions: pressure 7-10 MPa, mass flux 0.5-4.0 Mg/m{sup 2}s and critical quality 0.23-0.9. The effect on CHF of the outer-to-inner surface heat flux ratio, was also examined. The prediction of CHF for bilaterally heated annuli was based on the droplet-diffusion model proposed by Kirillov and Smogalev. While their model refers only to CHF occurrence at the inner surface, we extended it to cases where CHF occurs at the outer surface, and simultaneously at both surfaces, thus covering all cases of CHF occurrence in bilaterally heated annuli. From the annuli CHF data of Becker and Letzter, we derived empirical functions required by the model. the proposed equations provide good accuracy for the CHF data used in this study. Moreover, the equations can predict conditions at which CHF occurs simultaneously at both surfaces. Also, this method can be used for cases with only one heated surface.

  3. Comparing laser-based open- and closed-path gas analyzers to measure methane fluxes using the eddy covariance method

    Science.gov (United States)

    Detto, Matteo; Verfaillie, Joseph; Anderson, Frank; Xu, Liukang; Baldocchi, Dennis

    2011-01-01

    Closed- and open-path methane gas analyzers are used in eddy covariance systems to compare three potential methane emitting ecosystems in the Sacramento-San Joaquin Delta (CA, USA): a rice field, a peatland pasture and a restored wetland. The study points out similarities and differences of the systems in field experiments and data processing. The closed-path system, despite a less intrusive placement with the sonic anemometer, required more care and power. In contrast, the open-path system appears more versatile for a remote and unattended experimental site. Overall, the two systems have comparable minimum detectable limits, but synchronization between wind speed and methane data, air density corrections and spectral losses have different impacts on the computed flux covariances. For the closed-path analyzer, air density effects are less important, but the synchronization and spectral losses may represent a problem when fluxes are small or when an undersized pump is used. For the open-path analyzer air density corrections are greater, due to spectroscopy effects and the classic Webb–Pearman–Leuning correction. Comparison between the 30-min fluxes reveals good agreement in terms of magnitudes between open-path and closed-path flux systems. However, the scatter is large, as consequence of the intensive data processing which both systems require.

  4. Surface wettability and subcooling on nucleate pool boiling heat transfer

    Science.gov (United States)

    Suroto, Bambang Joko; Kohno, Masamichi; Takata, Yasuyuki

    2018-02-01

    The effect of varying surface wettabilities and subcooling on nucleate pool boiling heat transfer at intermediate heat flux has been examined and investigated. The experiments were performed using pure water as the working fluid and subcooling ranging from 0, 5 and 10 K, respectively. The three types of heat transfer block were used that are bare surface/hydrophilic (polished copper), superhydrophilic/TiO2-coated on copper and hydrophobic/PTFE surface. The experimental results will be examined by the existing model. The results show that the heat transfer performance of surfaces with PTFE coating is better at low heat flux. While for an intermediate heat flux, superhydrophilic surface (TiO2) is superior compared to hydrophilic and hydrophobic surfaces. It is observed that the heat transfer performance is decreasing when the sub cooling degree is increased.

  5. A New Framework to Compare Mass-Flux Schemes Within the AROME Numerical Weather Prediction Model

    Science.gov (United States)

    Riette, Sébastien; Lac, Christine

    2016-08-01

    In the Application of Research to Operations at Mesoscale (AROME) numerical weather forecast model used in operations at Météo-France, five mass-flux schemes are available to parametrize shallow convection at kilometre resolution. All but one are based on the eddy-diffusivity-mass-flux approach, and differ in entrainment/detrainment, the updraft vertical velocity equation and the closure assumption. The fifth is based on a more classical mass-flux approach. Screen-level scores obtained with these schemes show few discrepancies and are not sufficient to highlight behaviour differences. Here, we describe and use a new experimental framework, able to compare and discriminate among different schemes. For a year, daily forecast experiments were conducted over small domains centred on the five French metropolitan radio-sounding locations. Cloud base, planetary boundary-layer height and normalized vertical profiles of specific humidity, potential temperature, wind speed and cloud condensate were compared with observations, and with each other. The framework allowed the behaviour of the different schemes in and above the boundary layer to be characterized. In particular, the impact of the entrainment/detrainment formulation, closure assumption and cloud scheme were clearly visible. Differences mainly concerned the transport intensity thus allowing schemes to be separated into two groups, with stronger or weaker updrafts. In the AROME model (with all interactions and the possible existence of compensating errors), evaluation diagnostics gave the advantage to the first group.

  6. Experimental measurements and analytical analysis related to gas turbine heat transfer. Part 1: Time-averaged heat-flux and surface-pressure measurements on the vanes and blades of the SSME fuel-side turbine and comparison with prediction. Part 2: Phase-resolved surface-pressure and heat-flux measurements on the first blade of the SSME fuel-side turbine

    Science.gov (United States)

    1994-01-01

    Time averaged Stanton number and surface-pressure distributions are reported for the first-stage vane row, the first stage blade row, and the second stage vane row of the Rocketdyne Space Shuttle Main Engine two-stage fuel-side turbine. Unsteady pressure envelope measurements for the first blade are also reported. These measurements were made at 10 percent, 50 percent, and 90 percent span on both the pressure and suction surfaces of the first stage components. Additional Stanton number measurements were made on the first stage blade platform blade tip, and shroud, and at 50 percent span on the second vane. A shock tube was used as a short duration source of heated and pressurized air to which the turbine was subjected. Platinum thin-film heat flux gages were used to obtain the heat flux measurements, while miniature silicon-diaphragm flush-mounted pressure transducers were used to obtain the pressure measurements. The first stage vane Stanton number distributions are compared with predictions obtained using a version of STAN5 and a quasi-3D Navier-Stokes solution. This same quasi-3D N-S code was also used to obtain predictions for the first blade and the second vane.

  7. A Numerical Study on Impact of Taiwan Island Surface Heat Flux on Super Typhoon Haitang (2005)

    OpenAIRE

    Xu, Hongxiong

    2015-01-01

    Three to four tropical cyclones (TCs) by average usually impact Taiwan every year. This study, using the Developmental Tested Center (DTC) version of the Hurricane WRF (HWRF) model, examines the effects of Taiwan’s island surface heat fluxes on typhoon structure, intensity, track, and its rainfall over the island. The numerical simulation successfully reproduced the structure and intensity of super Typhoon Haitang. The model, especially, reproduced the looped path and landfall at nearly the ...

  8. Estimating spatially distributed turbulent heat fluxes from high-resolution thermal imagery acquired with a UAV system.

    Science.gov (United States)

    Brenner, Claire; Thiem, Christina Elisabeth; Wizemann, Hans-Dieter; Bernhardt, Matthias; Schulz, Karsten

    2017-05-19

    In this study, high-resolution thermal imagery acquired with a small unmanned aerial vehicle (UAV) is used to map evapotranspiration (ET) at a grassland site in Luxembourg. The land surface temperature (LST) information from the thermal imagery is the key input to a one-source and two-source energy balance model. While the one-source model treats the surface as a single uniform layer, the two-source model partitions the surface temperature and fluxes into soil and vegetation components. It thus explicitly accounts for the different contributions of both components to surface temperature as well as turbulent flux exchange with the atmosphere. Contrary to the two-source model, the one-source model requires an empirical adjustment parameter in order to account for the effect of the two components. Turbulent heat flux estimates of both modelling approaches are compared to eddy covariance (EC) measurements using the high-resolution input imagery UAVs provide. In this comparison, the effect of different methods for energy balance closure of the EC data on the agreement between modelled and measured fluxes is also analysed. Additionally, the sensitivity of the one-source model to the derivation of the empirical adjustment parameter is tested. Due to the very dry and hot conditions during the experiment, pronounced thermal patterns developed over the grassland site. These patterns result in spatially variable turbulent heat fluxes. The model comparison indicates that both models are able to derive ET estimates that compare well with EC measurements under these conditions. However, the two-source model, with a more complex treatment of the energy and surface temperature partitioning between the soil and vegetation, outperformed the simpler one-source model in estimating sensible and latent heat fluxes. This is consistent with findings from prior studies. For the one-source model, a time-variant expression of the adjustment parameter (to account for the difference between

  9. Greenland ice sheet surface mass-balance modelling and freshwater flux for 2007, and in a 1995-2007 perspective

    DEFF Research Database (Denmark)

    Mernild, Sebastian H.; Liston, Glen E.; Hiemstra, Christopher A.

    2009-01-01

    y-1); the only year with a negative GrIS SMB. Runoff in 2007 was approximately 35% greater than average for 1995-2006. From 1995 through 2007 overall, precipitation decreased while ablation increased, leading to an increased average SMB loss of 127 km3. The modelled GrIS SMB was merged with previous......-stations) were used as model inputs. The GrIS minimum surface melt extent of 29% occurred in 1996, while the greatest extent of 51% was present in 2007. The 2007 melt extent was 20% greater than the average for 1995-2006. The year 2007 had the highest GrIS surface runoff (523 km3 y-1) and the lowest SMB (-3 km3...... estimates of GrIS subglacial runoff (from geothermal melt) and GrIS calving to quantify GrIS freshwater flux to the ocean, indicating an average negative mass-balance of 265 (±83) km3 y-1. This study further suggests an average GrIS freshwater flux of approximately 786 km3 y-1 to the ocean, of which 45...

  10. Do Surface Energy Fluxes Reveal Land Use/Land Cover Change in South Florida?: A Remote Sensing Perspective

    Science.gov (United States)

    Kandel, H. P.; Melesse, A. M.

    2017-12-01

    Series of changes on land use/ land cover in South Florida resulting from drainage and development activities during early to mid-20th followed by restoration measures since late-20th century have had prominent impacts on hydrologic regime and energy fluxes in the region. Previous results from numerical modeling and MODIS-based analysis have shown a shift in dominance of heat fluxes: from latent to sensible along the axes of urbanization, and an opposite along the axes of restoration. This study implements a slightly modified version of surface energy balance algorithm (SEBAL) on cloud-masked Landsat imageries archived over the period of 30-years combined with ground-meteorological data for South Florida using spatial analysis model in ArcGIS and calculates energy flux components: sensible heat flux, latent heat flux, and ground heat flux. The study finally computes variation of Bowen's ratio (BR) and daily evapotranspiration (ET) rate over various land covers for different years. Coexistences are apparent between increased BR and increased intensity of urbanization, and between increased daily ET rates and improved best management practices in agricultural areas. An increase in mean urban BR from 1.67 in 1984 to 3.06 in 2010 show plausible link of BR with urban encroachment of open lands, and expulsion of additional heat by increased population/automobiles/factories/air conditioning units. Likewise, increase in mean agricultural daily ET rates from 0.21 mm/day to 3.60 mm/day between 1984 to 2010 probably shows the effects of improved moisture conditions on the northern farm lands as the results of restoration practices. Once new observed data become available to corroborate these results, remote sensing methods-owing to their greater spatial and temporal details-can be used as assessment measures both for the progress of restoration evaluation and for the extent detection of human-induced climate change.

  11. A Novel Method to Magnetic Flux Linkage Optimization of Direct-Driven Surface-Mounted Permanent Magnet Synchronous Generator Based on Nonlinear Dynamic Analysis

    Directory of Open Access Journals (Sweden)

    Qian Xie

    2016-07-01

    Full Text Available This paper pays attention to magnetic flux linkage optimization of a direct-driven surface-mounted permanent magnet synchronous generator (D-SPMSG. A new compact representation of the D-SPMSG nonlinear dynamic differential equations to reduce system parameters is established. Furthermore, the nonlinear dynamic characteristics of new D-SPMSG equations in the process of varying magnetic flux linkage are considered, which are illustrated by Lyapunov exponent spectrums, phase orbits, Poincaré maps, time waveforms and bifurcation diagrams, and the magnetic flux linkage stable region of D-SPMSG is acquired concurrently. Based on the above modeling and analyses, a novel method of magnetic flux linkage optimization is presented. In addition, a 2 MW D-SPMSG 2D/3D model is designed by ANSYS software according to the practical design requirements. Finally, five cases of D-SPMSG models with different magnetic flux linkages are simulated by using the finite element analysis (FEA method. The nephograms of magnetic flux density are agreement with theoretical analysis, which both confirm the correctness and effectiveness of the proposed approach.

  12. The inverse Numerical Computer Program FLUX-BOT for estimating Vertical Water Fluxes from Temperature Time-Series.

    Science.gov (United States)

    Trauth, N.; Schmidt, C.; Munz, M.

    2016-12-01

    Heat as a natural tracer to quantify water fluxes between groundwater and surface water has evolved to a standard hydrological method. Typically, time series of temperatures in the surface water and in the sediment are observed and are subsequently evaluated by a vertical 1D representation of heat transport by advection and dispersion. Several analytical solutions as well as their implementation into user-friendly software exist in order to estimate water fluxes from the observed temperatures. Analytical solutions can be easily implemented but assumptions on the boundary conditions have to be made a priori, e.g. sinusoidal upper temperature boundary. Numerical models offer more flexibility and can handle temperature data which is characterized by irregular variations such as storm-event induced temperature changes and thus cannot readily be incorporated in analytical solutions. This also reduced the effort of data preprocessing such as the extraction of the diurnal temperature variation. We developed a software to estimate water FLUXes Based On Temperatures- FLUX-BOT. FLUX-BOT is a numerical code written in MATLAB which is intended to calculate vertical water fluxes in saturated sediments, based on the inversion of measured temperature time series observed at multiple depths. It applies a cell-centered Crank-Nicolson implicit finite difference scheme to solve the one-dimensional heat advection-conduction equation. Besides its core inverse numerical routines, FLUX-BOT includes functions visualizing the results and functions for performing uncertainty analysis. We provide applications of FLUX-BOT to generic as well as to measured temperature data to demonstrate its performance.

  13. Using heat to characterize streambed water flux variability in four stream reaches

    Science.gov (United States)

    Essaid, H.I.; Zamora, C.M.; McCarthy, K.A.; Vogel, J.R.; Wilson, J.T.

    2008-01-01

    Estimates of streambed water flux are needed for the interpretation of streambed chemistry and reactions. Continuous temperature and head monitoring in stream reaches within four agricultural watersheds (Leary Weber Ditch, IN; Maple Creek, NE; DR2 Drain, WA; and Merced River, CA) allowed heat to be used as a tracer to study the temporal and spatial variability of fluxes through the streambed. Synoptic methods (seepage meter and differential discharge measurements) were compared with estimates obtained by using heat as a tracer. Water flux was estimated by modeling one-dimensional vertical flow of water and heat using the model VS2DH. Flux was influenced by physical heterogeneity of the stream channel and temporal variability in stream and ground-water levels. During most of the study period (April-December 2004), flux was upward through the streambeds. At the IN, NE, and CA sites, high-stage events resulted in rapid reversal of flow direction inducing short-term surface-water flow into the streambed. During late summer at the IN site, regional ground-water levels dropped, leading to surface-water loss to ground water that resulted in drying of the ditch. Synoptic measurements of flux generally supported the model flux estimates. Water flow through the streambed was roughly an order of magnitude larger in the humid basins (IN and NE) than in the arid basins (WA and CA). Downward flux, in response to sudden high streamflows, and seasonal variability in flux was most pronounced in the humid basins and in high conductivity zones in the streambed. Copyright ?? 2008 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.

  14. Surface Turbulent Fluxes, 1x1 deg Monthly Grid, Set1 and Interpolated Data V2c (GSSTFM) at GES DISC

    Data.gov (United States)

    National Aeronautics and Space Administration — These data are the Goddard Satellite-based Surface Turbulent Fluxes Version-2c Dataset recently produced through a MEaSUREs funded project led by Dr. Chung-Lin Shie...

  15. Goddard Satellite-Based Surface Turbulent Fluxes, 0.25x0.25 deg, Daily Grid, V3, (GSSTF_F14) V3

    Data.gov (United States)

    National Aeronautics and Space Administration — These data are part of the Goddard Satellite-based Surface Turbulent Fluxes Version 3 (GSSTF3) Dataset recently produced through a MEaSURES funded project led by Dr....

  16. Effects of Oxidation and fractal surface roughness on the wettability and critical heat flux of glass-peened zirconium alloy tubes

    International Nuclear Information System (INIS)

    Fong, R.W.L.; Nitheanandan, T.; Bullock, C.D.; Slater, L.F.; McRae, G.A.

    2003-05-01

    Glass-bead peening the outside surfaces of zirconium alloy tubes has been shown to increase the Critical Heat Flux (CHF) in pool boiling of water. The CHF is found to correlate with the fractal roughness of the metal tube surfaces. In this study on the effect of oxidation on glass-peened surfaces, test measurements for CHF, surface wettability and roughness have been evaluated using various glass-peened and oxidized zirconium alloy tubes. The results show that oxidation changes the solid-liquid contact angle (i.e., decreases wettability of the metal-oxide surface), but does not change the fractal surface roughness, appreciably. Thus, oxidation of the glass-peened surfaces of zirconium alloy tubes is not expected to degrade the CHF enhancement obtained by glass-bead peening. (author)

  17. Pressure driven currents near magnetic islands in 3D MHD equilibria: Effects of pressure variation within flux surfaces and of symmetry

    Science.gov (United States)

    Reiman, Allan H.

    2016-07-01

    In toroidal, magnetically confined plasmas, the heat and particle transport is strongly anisotropic, with transport along the field lines sufficiently strong relative to cross-field transport that the equilibrium pressure can generally be regarded as constant on the flux surfaces in much of the plasma. The regions near small magnetic islands, and those near the X-lines of larger islands, are exceptions, having a significant variation of the pressure within the flux surfaces. It is shown here that the variation of the equilibrium pressure within the flux surfaces in those regions has significant consequences for the pressure driven currents. It is further shown that the consequences are strongly affected by the symmetry of the magnetic field if the field is invariant under combined reflection in the poloidal and toroidal angles. (This symmetry property is called "stellarator symmetry.") In non-stellarator-symmetric equilibria, the pressure-driven currents have logarithmic singularities at the X-lines. In stellarator-symmetric MHD equilibria, the singular components of the pressure-driven currents vanish. These equilibria are to be contrasted with equilibria having B ṡ∇p =0 , where the singular components of the pressure-driven currents vanish regardless of the symmetry. They are also to be contrasted with 3D MHD equilibrium solutions that are constrained to have simply nested flux surfaces, where the pressure-driven current goes like 1 /x near rational surfaces, where x is the distance from the rational surface, except in the case of quasi-symmetric flux surfaces. For the purpose of calculating the pressure-driven currents near magnetic islands, we work with a closed subset of the MHD equilibrium equations that involves only perpendicular force balance, and is decoupled from parallel force balance. It is not correct to use the parallel component of the conventional MHD force balance equation, B ṡ∇p =0 , near magnetic islands. Small but nonzero values of B

  18. BOREAS TF-06 SSA-YA Surface Energy Flux and Meteorological Data

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: Contains meteorology data collected at the SSA-YA tower flux site by the TF6 group. These data were reported at 10 minute intervals. The flux and ancillary...

  19. Landsat and Local Land Surface Temperatures in a Heterogeneous Terrain Compared to MODIS Values

    Directory of Open Access Journals (Sweden)

    Gemma Simó

    2016-10-01

    Full Text Available Land Surface Temperature (LST as provided by remote sensing onboard satellites is a key parameter for a number of applications in Earth System studies, such as numerical modelling or regional estimation of surface energy and water fluxes. In the case of Moderate Resolution Imaging Spectroradiometer (MODIS onboard Terra or Aqua, pixels have resolutions near 1 km 2 , LST values being an average of the real subpixel variability of LST, which can be significant for heterogeneous terrain. Here, we use Landsat 7 LST decametre-scale fields to evaluate the temporal and spatial variability at the kilometre scale and compare the resulting average values to those provided by MODIS for the same observation time, for the very heterogeneous Campus of the University of the Balearic Islands (Mallorca, Western Mediterranean, with an area of about 1 km 2 , for a period between 2014 and 2016. Variations of LST between 10 and 20 K are often found at the sub-kilometre scale. In addition, MODIS values are compared to the ground truth for one point in the Campus, as obtained from a four-component net radiometer, and a bias of 3.2 K was found in addition to a Root Mean Square Error (RMSE of 4.2 K. An indication of a more elaborated local measurement strategy in the Campus is given, using an array of radiometers distributed in the area.

  20. Characterization of local heat fluxes around ICRF antennas on JET

    Energy Technology Data Exchange (ETDEWEB)

    Campergue, A.-L. [Ecole Nationale des Ponts et Chaussées, F77455 Marne-la-Vallée (France); Jacquet, P.; Monakhov, I.; Arnoux, G.; Brix, M.; Sirinelli, A. [Euratom/CCFE Association, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom); Bobkov, V. [Max-Planck-Institut für Plasmaphysik, EURATOM-Assoziation, Garching (Germany); Milanesio, D. [Politecnico di Torino, Department of Electronics, Torino (Italy); Colas, L. [CEA, IRFM, F-13108 Saint-Paul-Lez-Durance (France); Collaboration: JET-EFDA Contributors

    2014-02-12

    When using Ion Cyclotron Range of Frequency (ICRF) heating, enhanced power deposition on Plasma-Facing Components (PFCs) close to the antennas can occur. Experiments have recently been carried out on JET with the new ITER-Like-Wall (ILW) to characterize the heat fluxes on the protection of the JET ICRF antennas, using Infra-Red (IR) thermography measurement. The measured heat flux patterns along the poloidal limiters surrounding powered antennas were compared to predictions from a simple RF sheath rectification model. The RF electric field, parallel to the static magnetic field in front of the antenna, was evaluated using the TOPICA code, integrating a 3D flattened model of the JET A2 antennas. The poloidal density variation in front of the limiters was obtained from the mapping of the Li-beam or edge reflectometry measurements using the flux surface geometry provided by EFIT equilibrium reconstruction. In many cases, this simple model can well explain the position of the maximum heat flux on the different protection limiters and the heat-flux magnitude, confirming that the parallel RF electric field and the electron plasma density in front of the antenna are the main driving parameters for ICRF-induced local heat fluxes.

  1. Hybrid Heat Pipes for Lunar and Martian Surface and High Heat Flux Space Applications

    Science.gov (United States)

    Ababneh, Mohammed T.; Tarau, Calin; Anderson, William G.; Farmer, Jeffery T.; Alvarez-Hernandez, Angel R.

    2016-01-01

    Novel hybrid wick heat pipes are developed to operate against gravity on planetary surfaces, operate in space carrying power over long distances and act as thermosyphons on the planetary surface for Lunar and Martian landers and rovers. These hybrid heat pipes will be capable of operating at the higher heat flux requirements expected in NASA's future spacecraft and on the next generation of polar rovers and equatorial landers. In addition, the sintered evaporator wicks mitigate the start-up problems in vertical gravity aided heat pipes because of large number of nucleation sites in wicks which will allow easy boiling initiation. ACT, NASA Marshall Space Flight Center, and NASA Johnson Space Center, are working together on the Advanced Passive Thermal experiment (APTx) to test and validate the operation of a hybrid wick VCHP with warm reservoir and HiK"TM" plates in microgravity environment on the ISS.

  2. Lunar dusty plasma: A result of interaction of the solar wind flux and ultraviolet radiation with the lunar surface

    International Nuclear Information System (INIS)

    Lisin, E A; Tarakanov, V P; Petrov, O F; Popel, S I

    2015-01-01

    One of the main problems of future missions to the Moon is associated with lunar dust. Solar wind flux and ultraviolet radiation interact with the lunar surface. As a result, there is a substantial surface change and a near-surface plasma sheath. Dust particles from the lunar regolith, which turned in this plasma because of any mechanical processes, can levitate above the surface, forming dust clouds. In preparing of the space experiments “Luna-Glob” and “Luna-Resource” particle-in-cell calculations of the near-surface plasma sheath parameters are carried out. Here we present some new results of particle-in-cell simulation of the plasma sheath formed near the surface of the moon as a result of interaction of the solar wind and ultraviolet radiation with the lunar surface. The conditions of charging and stable levitation of dust particles in plasma above the lunar surface are also considered. (paper)

  3. Effects of leaf area index on the coupling between water table, land surface energy fluxes, and planetary boundary layer at the regional scale

    Science.gov (United States)

    Lu, Y.; Rihani, J.; Langensiepen, M.; Simmer, C.

    2013-12-01

    Vegetation plays an important role in the exchange of moisture and energy at the land surface. Previous studies indicate that vegetation increases the complexity of the feedbacks between the atmosphere and subsurface through processes such as interception, root water uptake, leaf surface evaporation, and transpiration. Vegetation cover can affect not only the interaction between water table depth and energy fluxes, but also the development of the planetary boundary layer. Leaf Area Index (LAI) is shown to be a major factor influencing these interactions. In this work, we investigate the sensitivity of water table, surface energy fluxes, and atmospheric boundary layer interactions to LAI as a model input. We particularly focus on the role LAI plays on the location and extent of transition zones of strongest coupling and how this role changes over seasonal timescales for a real catchment. The Terrestrial System Modelling Platform (TerrSysMP), developed within the Transregional Collaborative Research Centre 32 (TR32), is used in this study. TerrSysMP consists of the variably saturated groundwater model ParFlow, the land surface model Community Land Model (CLM), and the regional climate and weather forecast model COSMO (COnsortium for Small-scale Modeling). The sensitivity analysis is performed over a range of LAI values for different vegetation types as extracted from the Moderate Resolution Imaging Spectroradiometer (MODIS) dataset for the Rur catchment in Germany. In the first part of this work, effects of vegetation structure on land surface energy fluxes and their connection to water table dynamics are studied using the stand-alone CLM and the coupled subsurface-surface components of TerrSysMP (ParFlow-CLM), respectively. The interconnection between LAI and transition zones of strongest coupling are investigated and analyzed through a subsequent set of subsurface-surface-atmosphere coupled simulations implementing the full TerrSysMP model system.

  4. Eddy Correlation Flux Measurement System Handbook

    Energy Technology Data Exchange (ETDEWEB)

    Cook, D. R. [Argonne National Lab. (ANL), Argonne, IL (United States)

    2016-01-01

    The eddy correlation (ECOR) flux measurement system provides in situ, half-hour measurements of the surface turbulent fluxes of momentum, sensible heat, latent heat, and carbon dioxide (CO2) (and methane at one Southern Great Plains extended facility (SGP EF) and the North Slope of Alaska Central Facility (NSA CF). The fluxes are obtained with the eddy covariance technique, which involves correlation of the vertical wind component with the horizontal wind component, the air temperature, the water vapor density, and the CO2 concentration. The instruments used are: • a fast-response, three-dimensional (3D) wind sensor (sonic anemometer) to obtain the orthogonal wind components and the speed of sound (SOS) (used to derive the air temperature) • an open-path infrared gas analyzer (IRGA) to obtain the water vapor density and the CO2 concentration, and • an open-path infrared gas analyzer (IRGA) to obtain methane density and methane flux at one SGP EF and at the NSA CF. The ECOR systems are deployed at the locations where other methods for surface flux measurements (e.g., energy balance Bowen ratio [EBBR] systems) are difficult to employ, primarily at the north edge of a field of crops. A Surface Energy Balance System (SEBS) has been installed collocated with each deployed ECOR system in SGP, NSA, Tropical Western Pacific (TWP), ARM Mobile Facility 1 (AMF1), and ARM Mobile Facility 2 (AMF2). The surface energy balance system consists of upwelling and downwelling solar and infrared radiometers within one net radiometer, a wetness sensor, and soil measurements. The SEBS measurements allow the comparison of ECOR sensible and latent heat fluxes with the energy balance determined from the SEBS and provide information on wetting of the sensors for data quality purposes. The SEBS at one SGP and one NSA site also support upwelling and downwelling PAR measurements to qualify those two locations as Ameriflux sites.

  5. Powder Flux Regulation in the Laser Material Deposition Process

    Science.gov (United States)

    Arrizubieta, Jon Iñaki; Wegener, Maximiliam; Arntz, Kristian; Lamikiz, Aitzol; Ruiz, Jose Exequiel

    In the present research work a powder flux regulation system has been designed, developed and validated with the aim of improving the Laser Material Deposition (LMD) process. In this process, the amount of deposited material per substrate surface unit area depends on the real feed rate of the nozzle. Therefore, a regulation system based on a solenoid valve has been installed at the nozzle entrance in order to control the powder flux. The powder flux control has been performed based on the machine real feed rate, which is compared with the programmed feed rate. An instantaneous velocity error is calculated and the powder flow is controlled as a function of this variation using Pulse Width Modulation (PWM) signals. Thereby, in zones where the Laser Material Deposition machine reduces the feed rate due to a trajectory change, powder accumulation can be avoided and the generated clads would present a homogeneous shape.

  6. Atmosphere-surface interactions over polar oceans and heterogeneous surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Vihma, T.

    1995-12-31

    Processes of interaction between the atmospheric boundary layer and the planetary surface have been studied with special emphasis on polar ocean surfaces: the open ocean, leads, polynyas and sea ice. The local exchange of momentum, heat and moisture has been studied experimentally both in the Weddell Sea and in the Greenland Sea. Exchange processes over heterogeneous surfaces are addressed by modelling studies. Over a homogeneous surface, the local turbulent fluxes can be reasonably well estimated using an iterative flux-profile scheme based on the Monin-Obukhov similarity theory. In the Greenland Sea, the near-surface air temperature and the generally small turbulent fluxes over the open ocean were affected by the sea surface temperature fronts. Over the sea ice cover in the Weddell Sea, the turbulent sensible heat flux was generally downwards, and together with an upward oceanic heat flux through the ice it compensated the heat loss from the surface via long-wave radiation. The wind dominated on time scales of days, while the current became important on longer time scales. The drift dynamics showed apparent spatial differences between the eastern and western regions, as well as between the Antarctic Circumpolar Current and the rest of the Weddell Sea. Inertial motion was present in regions of low ice concentration. The surface heterogeneity, arising e.g. from roughness or temperature distribution, poses a problem for the parameterization of surface exchange processes in large-scale models. In the case of neutral flow over a heterogeneous terrain, an effective roughness length can be used to parameterize the roughness effects

  7. Atmosphere-surface interactions over polar oceans and heterogeneous surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Vihma, T

    1996-12-31

    Processes of interaction between the atmospheric boundary layer and the planetary surface have been studied with special emphasis on polar ocean surfaces: the open ocean, leads, polynyas and sea ice. The local exchange of momentum, heat and moisture has been studied experimentally both in the Weddell Sea and in the Greenland Sea. Exchange processes over heterogeneous surfaces are addressed by modelling studies. Over a homogeneous surface, the local turbulent fluxes can be reasonably well estimated using an iterative flux-profile scheme based on the Monin-Obukhov similarity theory. In the Greenland Sea, the near-surface air temperature and the generally small turbulent fluxes over the open ocean were affected by the sea surface temperature fronts. Over the sea ice cover in the Weddell Sea, the turbulent sensible heat flux was generally downwards, and together with an upward oceanic heat flux through the ice it compensated the heat loss from the surface via long-wave radiation. The wind dominated on time scales of days, while the current became important on longer time scales. The drift dynamics showed apparent spatial differences between the eastern and western regions, as well as between the Antarctic Circumpolar Current and the rest of the Weddell Sea. Inertial motion was present in regions of low ice concentration. The surface heterogeneity, arising e.g. from roughness or temperature distribution, poses a problem for the parameterization of surface exchange processes in large-scale models. In the case of neutral flow over a heterogeneous terrain, an effective roughness length can be used to parameterize the roughness effects

  8. A new geometrical construction using rounded surfaces proposed for the transverse flux machine for direct drive wind turbine

    DEFF Research Database (Denmark)

    Argeseanu, Alin; Nica, Florin Valentin Traian; Ritchie, Ewen

    2014-01-01

    This paper proposes a new construction for transverse flux machines (TFM) using a rounded surfaces core geometry. The new concept has been developed for TFM with U core geometry. In this case a new analytic design procedure was proposed. The analytic design of the new TFM construction is further ...... proposed concept is more attractive for the direct-drive wind turbine application....

  9. Flux pinning by voids in surface-oxidized superconducting niobium and vanadium

    International Nuclear Information System (INIS)

    Meij, G.P. van der.

    1984-03-01

    The volume pinning force in several niobium and vanadium samples with voids is determined at various temperatures. Reasonable agreement is found with the collective pinning theory of Larkin and Ovchinnikov above the field of maximum pinning, if the flux line lattice is assumed to be amorphous in this region and if the elementary pinning force is calculated from the quasi-classical theory of Thuneberg, Kurkijaervi, and Rainer. Also some history and relaxation effects are studied in an alternating field. A qualitative explanation is given in terms of flux line dislocations, which reduce the shear strength of the flux line lattice. (Auth.)

  10. Turbulent fluxes of momentum and heat over land in the High-Arctic summer: the influence of observation techniques

    Directory of Open Access Journals (Sweden)

    Anna Sjöblom

    2014-06-01

    Full Text Available Different observation techniques for atmospheric turbulent fluxes of momentum and sensible heat were tested in a High-Arctic valley in Svalbard during two consecutive summers (June–August in 2010 and 2011. The gradient method (GM and the bulk method (BM have been compared to the more direct eddy covariance method (ECM in order to evaluate if relatively robust and cheap instrumentation with low power consumption can be used as a means to increase the number of observations, especially at remote locations where instruments need to be left unattended for extended periods. Such campaigns increase knowledge about the snow-free surface exchange processes, an area which is relatively little investigated compared to snow-covered ground. The GM agreed closely to the ECM, especially for momentum flux where the two methods agree within 5%. For sensible heat flux, the GM produces, on average, approximately 40% lower values for unstable stratification and 67% lower for stable stratification. However, this corresponds to only 20 and 12 W m−2, respectively. The BM, however, shows a greater scatter and larger differences for both parameters. In addition to testing these methods, radiation properties were measured and the surface albedo was found to increase through the summer, from approximately 0.1 to 0.2. The surface energy budget shows that the sensible heat flux is usually directed upwards for the whole summer, while the latent heat flux is upwards in June, but becomes downward in July and August.

  11. Measuring Convective Mass Fluxes Over Tropical Oceans

    Science.gov (United States)

    Raymond, David

    2017-04-01

    Deep convection forms the upward branches of all large-scale circulations in the tropics. Understanding what controls the form and intensity of vertical convective mass fluxes is thus key to understanding tropical weather and climate. These mass fluxes and the corresponding conditions supporting them have been measured by recent field programs (TPARC/TCS08, PREDICT, HS3) in tropical disturbances considered to be possible tropical storm precursors. In reality, this encompasses most strong convection in the tropics. The measurements were made with arrays of dropsondes deployed from high altitude. In some cases Doppler radar provided additional measurements. The results are in some ways surprising. Three factors were found to control the mass flux profiles, the strength of total surface heat fluxes, the column-integrated relative humidity, and the low to mid-tropospheric moist convective instability. The first two act as expected, with larger heat fluxes and higher humidity producing more precipitation and stronger lower tropospheric mass fluxes. However, unexpectedly, smaller (but still positive) convective instability produces more precipitation as well as more bottom-heavy convective mass flux profiles. Furthermore, the column humidity and the convective instability are anti-correlated, at least in the presence of strong convection. On spatial scales of a few hundred kilometers, the virtual temperature structure appears to be in dynamic balance with the pattern of potential vorticity. Since potential vorticity typically evolves on longer time scales than convection, the potential vorticity pattern plus the surface heat fluxes then become the immediate controlling factors for average convective properties. All measurements so far have taken place in regions with relatively flat sea surface temperature (SST) distributions. We are currently seeking funding for a measurement program in the tropical east Pacific, a region that exhibits strong SST gradients and

  12. Dry-out heat fluxes of falling film and low-mass flux upward-flow in heated tubes

    International Nuclear Information System (INIS)

    Koizumi, Yasuo; Ueda, Tatsuhiro; Matsuo, Teruyuki; Miyota, Yukio

    1998-01-01

    Dry-out heat fluxes were investigated experimentally for a film flow falling down on the inner surface of vertical heated-tubes and for a low mass flux forced-upward flow in the tubes using R 113. This work followed the study on those for a two-phase natural circulation system. For the falling film boiling, flow state observation tests were also performed, where dry-patches appearing and disappearing repeatedly were observed near the exit end of the heated section at the dry-out heat flux conditions. Relation between the dry-out heat flux and the liquid film flow rate is analyzed. The dry-out heat fluxes of the low mass flux upflow are expressed well by the correlation proposed in the previous work. The relation for the falling film boiling shows a similar trend to that for the upflow boiling, however, the dry-out heat fluxes of the falling film are much lower, approximately one third, than those of the upward flow. (author)

  13. Heat in the Barents Sea: transport, storage, and surface fluxes

    Directory of Open Access Journals (Sweden)

    L. H. Smedsrud

    2010-02-01

    Full Text Available A column model is set up for the Barents Sea to explore sensitivity of surface fluxes and heat storage from varying ocean heat transport. Mean monthly ocean transport and atmospheric forcing are synthesised and force the simulations. Results show that by using updated ocean transports of heat and freshwater the vertical mean hydrographic seasonal cycle can be reproduced fairly well.

    Our results indicate that the ~70 TW of heat transported to the Barents Sea by ocean currents is lost in the southern Barents Sea as latent, sensible, and long wave radiation, each contributing 23–39 TW to the total heat loss. Solar radiation adds 26 TW in the south, as there is no significant ice production.

    The northern Barents Sea receives little ocean heat transport. This leads to a mixed layer at the freezing point during winter and significant ice production. There is little net surface heat loss annually in the north. The balance is achieved by a heat loss through long wave radiation all year, removing most of the summer solar heating.

    During the last decade the Barents Sea has experienced an atmospheric warming and an increased ocean heat transport. The Barents Sea responds to such large changes by adjusting temperature and heat loss. Decreasing the ocean heat transport below 50 TW starts a transition towards Arctic conditions. The heat loss in the Barents Sea depend on the effective area for cooling, and an increased heat transport leads to a spreading of warm water further north.

  14. Evapotranspiration and Surface Energy Fluxes Estimation Using the Landsat-7 Enhanced Thematic Mapper Plus Image over a Semiarid Agrosystem in the North-West of Algeria

    Directory of Open Access Journals (Sweden)

    Nehal Laounia

    Full Text Available Abstract Monitoring evapotranspiration and surface energy fluxes over a range of spatial and temporal scales is crucial for many agroenvironmental applications. Different remote sensing based energy balance models have been developed, to estimate evapotranspiration at both field and regional scales. In this contribution, METRIC (Mapping EvapoTranspiration at high Resolution with Internalized Calibration, has been applied for the estimation of actual evapotranspiration in the Ghriss plain in Mascara (western Algeria, a semiarid region with heterogeneous surface conditions. Four images acquired during 2001 and 2002 by the Landsat-7 satellite were used. The METRIC model followed an energy balance approach, where evapotranspiration is estimated as the residual term when net radiation, sensible and soil heat fluxes are known. Different moisture indicators derived from the evapotranspiration were then calculated: reference evapotranspiration fraction, Priestley-Taylor parameter and surface resistance to evaporation. The evaluation of evapotranspiration and surface energy fluxes are accurate enough for the spatial variations of evapotranspiration rather satisfactory than sophisticated models without having to introduce an important number of parameters in input with difficult accessibility in routine. In conclusion, the results suggest that METRIC can be considered as an operational approach to predict actual evapotranspiration from agricultural areas having limited amount of ground information.

  15. Sun's pole-equator flux differences

    Energy Technology Data Exchange (ETDEWEB)

    Belvedere, G [Istituto di Astronomia dell' Universita di Catania, Italy; Paterno, L [Osservatorio Astrofisico di Catania, Italy

    1977-04-01

    The possibility that large flux differences between the poles and the equator at the bottom of the solar convective zone are compatible with the small differences observed at the surface is studied. The consequences of increasing the depth of the convective zone due to overshooting are explored. A Boussinesq model is used for the convective zone and it is assumed that the interaction of the global convection with rotation is modelled through a convective flux coefficient whose perturbed part is proportional to the local Taylor number. The numerical integration of the equations of motion and energy shows that coexistence between large pole-equator flux differences at the bottom and small ones at the surface is possible if the solar convective zone extends to a depth of 0.4 R(Sun). The angular velocity distribution inside the convective zone is in agreement with the ..cap alpha omega..-dynamo theories of the solar cycle.

  16. Atmospheric sensitivity to land surface changes: comparing the impact of albedo, roughness, and evaporative resistance on near-surface air temperature using an idealized land model.

    Science.gov (United States)

    Lague, M. M.; Swann, A. L. S.; Bonan, G. B.

    2017-12-01

    Past studies have demonstrated how changes in vegetation can impact the atmosphere; however, it is often difficult to identify the exact physical pathway through which vegetation changes drive an atmospheric response. Surface properties (such as vegetation color, or height) control surface energy fluxes, which feed back on the atmosphere on both local and global scales by modifying temperatures, cloud cover, and energy gradients. Understanding how land surface properties influence energy fluxes is crucial for improving our understanding of how vegetation change - past, present, and future - impacts the atmosphere, global climate, and people. We explore the sensitivity of the atmosphere to perturbations of three land surface properties - albedo, roughness, and evaporative resistance - using an idealized land model coupled to an Earth System Model. We derive a relationship telling us how large a change in each surface property is required to drive a local 0.1 K change in 2m air temperature. Using this idealized framework, we are able to separate the influence on the atmosphere of each individual surface property. We demonstrate that the impact of each surface property on the atmosphere is spatially variable - that is, a similar change in vegetation can have different climate impacts if made in different locations. This analysis not only improves our understanding of how the land system can influence climate, but also provides us with a set of theoretical limits on the potential climate impact of arbitrary vegetation change (natural or anthropogenic).

  17. Orientation-free and differentially pumped addition of a low-flux reactive gas beam to a surface analysis system.

    Science.gov (United States)

    Harthcock, Colin; Jahanbekam, Abdolreza; Eskelsen, Jeremy R; Lee, David Y

    2016-11-01

    We describe an example of a piecewise gas chamber that can be customized to incorporate a low flux of gas-phase radicals with an existing surface analysis chamber for in situ and stepwise gas-surface interaction experiments without any constraint in orientation. The piecewise nature of this gas chamber provides complete angular freedom and easy alignment and does not require any modification of the existing surface analysis chamber. In addition, the entire gas-surface system is readily differentially pumped with the surface chamber kept under ultra-high-vacuum during the gas-surface measurements. This new design also allows not only straightforward reconstruction to accommodate the orientation of different surface chambers but also for the addition of other desired features, such as an additional pump to the current configuration. Stepwise interaction between atomic oxygen and a highly ordered pyrolytic graphite surface was chosen to test the effectiveness of this design, and the site-dependent O-atom chemisorption and clustering on the graphite surface were resolved by a scanning tunneling microscope in the nm-scale. X-ray photoelectron spectroscopy was used to further confirm the identity of the chemisorbed species on the graphite surface as oxygen.

  18. Modeling the South American regional smoke plume: aerosol optical depth variability and surface shortwave flux perturbation

    Directory of Open Access Journals (Sweden)

    N. E. Rosário

    2013-03-01

    Full Text Available Intra-seasonal variability of smoke aerosol optical depth (AOD and downwelling solar irradiance at the surface during the 2002 biomass burning season in South America was modeled using the Coupled Chemistry-Aerosol-Tracers Transport model with the Brazilian developments on the Regional Atmospheric Modeling System (CCATT-BRAMS. Measurements of total and fine mode fraction (FMF AOD from the AErosol RObotic NETwork (AERONET and solar irradiance at the surface from the Solar Radiation Network (SolRad-NET were used to evaluate model results. In general, the major features associated with AOD evolution over the southern part of the Amazon basin and cerrado ecosystem are captured by the model. The main discrepancies were found for high aerosol loading events. In the northeastern portion of the Amazon basin the model systematically underestimated total AOD, as expected, since smoke contribution is not dominant as it is in the southern portion and emissions other than smoke were not considered in the simulation. Better agreement was obtained comparing the model results with observed FMF AOD, which pointed out the relevance of coarse mode aerosol emission in that region. Likewise, major discrepancies over cerrado during high AOD events were found to be associated with coarse mode aerosol omission in our model. The issue of high aerosol loading events in the southern part of the Amazon was related to difficulties in predicting the smoke AOD field, which was discussed in the context of emissions shortcomings. The Cuiabá cerrado site was the only one where the highest quality AERONET data were unavailable for both total and FMF AOD. Thus, lower quality data were used. Root-mean-square error (RMSE between the model and observed FMF AOD decreased from 0.34 to 0.19 when extreme AOD events (FMF AOD550 nm ≥ 1.0 and Cuiabá were excluded from the analysis. Downward surface solar irradiance comparisons also followed similar trends when extreme AOD were excluded

  19. Development of micro-engineered textured tungsten surfaces for high heat flux applications

    Energy Technology Data Exchange (ETDEWEB)

    Sharafat, Shahram, E-mail: shahrams@ucla.edu [University of California Los Angeles, CA (United States); Aoyama, Aaron [University of California Los Angeles, CA (United States); Williams, Brian, E-mail: brian.williams@ultramet.com [Ultramet Inc., Pacoima, CA (United States); Ghoniem, Nasr [University of California Los Angeles, CA (United States)

    2013-11-15

    Surface micro-engineering can enhance the thermo-mechanical performance of plasma facing components (PFCs). For example, castellation of a surface can reduce thermal stress due to high heat loads and thus provide higher thermo-mechanical resilience. Recently, fabrication of a variety of micro-sized refractory dendrites with reproducible geometric characteristics (e.g., density, length, height, and aspect ratio) has been demonstrated. In contrast to flat surfaces exposed to high heat loads, dendrites deform independently to minimize near-surface thermal stress, which results in improved thermo-mechanical performance. Thus, the use of dendrites offers a unique micro-engineering approach to enhance the performance of PFC structures. A brief overview of W, Re, and Mo dendritic structures is given along with micrographs that show dendrite-coated surfaces. The thermal responses of representative dendrite structures are analyzed as a function of aspect ratios and dendrite geometry. The heat-management capability of needle-like dendrites exposed to a surface energy of up to 1 MJ/m{sup 2} is analyzed and compared to a flat surface. It is concluded that dendrite structures can significantly reduce thermal stress in the substrate when compared to flat surfaces. Implications of dendritic surfaces on sputter erosion rates are also discussed briefly.

  20. Development of high flux thermal neutron generator for neutron activation analysis

    Energy Technology Data Exchange (ETDEWEB)

    Vainionpaa, Jaakko H., E-mail: hannes@adelphitech.com [Adelphi Technology, 2003 E Bayshore Rd, Redwood City, CA 94063 (United States); Chen, Allan X.; Piestrup, Melvin A.; Gary, Charles K. [Adelphi Technology, 2003 E Bayshore Rd, Redwood City, CA 94063 (United States); Jones, Glenn [G& J Jones Enterprice, 7486 Brighton Ct, Dublin, CA 94568 (United States); Pantell, Richard H. [Department of Electrical Engineering, Stanford University, Stanford, CA (United States)

    2015-05-01

    The new model DD110MB neutron generator from Adelphi Technology produces thermal (<0.5 eV) neutron flux that is normally achieved in a nuclear reactor or larger accelerator based systems. Thermal neutron fluxes of 3–5 · 10{sup 7} n/cm{sup 2}/s are measured. This flux is achieved using four ion beams arranged concentrically around a target chamber containing a compact moderator with a central sample cylinder. Fast neutron yield of ∼2 · 10{sup 10} n/s is created at the titanium surface of the target chamber. The thickness and material of the moderator is selected to maximize the thermal neutron flux at the center. The 2.5 MeV neutrons are quickly thermalized to energies below 0.5 eV and concentrated at the sample cylinder. The maximum flux of thermal neutrons at the target is achieved when approximately half of the neutrons at the sample area are thermalized. In this paper we present simulation results used to characterize performance of the neutron generator. The neutron flux can be used for neutron activation analysis (NAA) prompt gamma neutron activation analysis (PGNAA) for determining the concentrations of elements in many materials. Another envisioned use of the generator is production of radioactive isotopes. DD110MB is small enough for modest-sized laboratories and universities. Compared to nuclear reactors the DD110MB produces comparable thermal flux but provides reduced administrative and safety requirements and it can be run in pulsed mode, which is beneficial in many neutron activation techniques.

  1. MERRA 2D IAU Diagnostic, Surface Fluxes, Time Average 1-hourly (2/3x1/2L1) V5.2.0

    Data.gov (United States)

    National Aeronautics and Space Administration — The MAT1NXFLX or tavg1_2d_flx_Nx data product is the MERRA Data Assimilation System 2-Dimensional surface turbulence flux diagnostic that is time averaged...

  2. Ship-borne contour integration for flux determination

    NARCIS (Netherlands)

    Groeskamp, S.; Maas, L.R.M.

    2012-01-01

    The consumption of nutrients by mussel beds can be monitored by measuring the net nutrient flux across a circumscribing vertical surface. Measuring this nutrient flux not only requires resolving the spatial (and temporal) distribution of nutrients at the bounding contour, but also an ability to

  3. Integrable perturbed magnetic fields in toroidal geometry: An exact analytical flux surface label for large aspect ratio

    Energy Technology Data Exchange (ETDEWEB)

    Kallinikos, N.; Isliker, H.; Vlahos, L.; Meletlidou, E. [Department of Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece)

    2014-06-15

    An analytical description of magnetic islands is presented for the typical case of a single perturbation mode introduced to tokamak plasma equilibrium in the large aspect ratio approximation. Following the Hamiltonian structure directly in terms of toroidal coordinates, the well known integrability of this system is exploited, laying out a precise and practical way for determining the island topology features, as required in various applications, through an analytical and exact flux surface label.

  4. Integrable perturbed magnetic fields in toroidal geometry: An exact analytical flux surface label for large aspect ratio

    Science.gov (United States)

    Kallinikos, N.; Isliker, H.; Vlahos, L.; Meletlidou, E.

    2014-06-01

    An analytical description of magnetic islands is presented for the typical case of a single perturbation mode introduced to tokamak plasma equilibrium in the large aspect ratio approximation. Following the Hamiltonian structure directly in terms of toroidal coordinates, the well known integrability of this system is exploited, laying out a precise and practical way for determining the island topology features, as required in various applications, through an analytical and exact flux surface label.

  5. Integrable perturbed magnetic fields in toroidal geometry: An exact analytical flux surface label for large aspect ratio

    International Nuclear Information System (INIS)

    Kallinikos, N.; Isliker, H.; Vlahos, L.; Meletlidou, E.

    2014-01-01

    An analytical description of magnetic islands is presented for the typical case of a single perturbation mode introduced to tokamak plasma equilibrium in the large aspect ratio approximation. Following the Hamiltonian structure directly in terms of toroidal coordinates, the well known integrability of this system is exploited, laying out a precise and practical way for determining the island topology features, as required in various applications, through an analytical and exact flux surface label

  6. Mercury fluxes over an Australian alpine grassland and observation of nocturnal atmospheric mercury depletion events

    Directory of Open Access Journals (Sweden)

    D. Howard

    2018-01-01

    Full Text Available Aerodynamic gradient measurements of the air–surface exchange of gaseous elemental mercury (GEM were undertaken over a 40 ha alpine grassland in Australia's Snowy Mountains region across a 3-week period during the late austral summer. Bi-directional GEM fluxes were observed throughout the study, with overall mean value of 0.2 ± 14.5 ng m−2 h−1 and mean nocturnal fluxes of −1.5 ± 7.8 ng m−2 h−1 compared to diurnal fluxes of 1.8 ± 18.6 ng m−2 h−1. Deposition velocities ranged from −2.2 to 2.9 cm s−1, whilst ambient GEM concentrations throughout the study were 0.59 ± 0.10 ng m−3. Cumulative GEM fluxes correlated well with 24 h running mean soil temperatures, and one precipitation event was shown to have a positive impact on diurnal emission fluxes. The underlying vegetation had largely senesced and showed little stomatal control on fluxes. Nocturnal atmospheric mercury depletion events (NAMDEs were observed concomitant with O3 depletion and dew formation under shallow, stable nocturnal boundary layers. A mass balance box model was able to reproduce ambient GEM concentration patterns during NAMDE and non-NAMDE nights without invoking chemical oxidation of GEM throughout the column, indicating a significant role of surface processes controlling deposition in these events. Surface deposition was enhanced under NAMDE nights, though uptake to dew likely represents less than one-fifth of this enhanced deposition. Instead, enhancement of the surface GEM gradient as a result of oxidation at the surface in the presence of dew is hypothesised to be responsible for a large portion of GEM depletion during these particular events. GEM emission pulses following nights with significant deposition provide evidence for the prompt recycling of 17 % of deposited mercury, with the remaining portion retained in surface sinks. The long-term impacts of any sinks are however likely to be minimal, as

  7. Dis-aggregation of airborne flux measurements using footprint analysis

    NARCIS (Netherlands)

    Hutjes, R.W.A.; Vellinga, O.S.; Gioli, B.; Miglietta, F.

    2010-01-01

    Aircraft measurements of turbulent fluxes are generally being made with the objective to obtain an estimate of regional exchanges between land surface and atmosphere, to investigate the spatial variability of these fluxes, but also to learn something about the fluxes from some or all of the land

  8. Prediction of transient maximum heat flux based on a simple liquid layer evaporation model

    International Nuclear Information System (INIS)

    Serizawa, A.; Kataoka, I.

    1981-01-01

    A model of liquid layer evaporation with considerable supply of liquid has been formulated to predict burnout characteristics (maximum heat flux, life, etc.) during an increase of the power. The analytical description of the model is built upon the visual and photographic observations of the boiling configuration at near peak heat flux reported by other investigators. The prediction compares very favourably with water data presently available. It is suggested from the work reported here that the maximum heat flux occurs because of a balance between the consumption of the liquid film on the heated surface and the supply of liquid. Thickness of the liquid film is also very important. (author)

  9. Numerical solutions for magnetohydrodynamic flow of nanofluid over a bidirectional non-linear stretching surface with prescribed surface heat flux boundary

    International Nuclear Information System (INIS)

    Mahanthesh, B.; Gireesha, B.J.; Gorla, R.S. Reddy; Abbasi, F.M.; Shehzad, S.A.

    2016-01-01

    Numerical solutions of three-dimensional flow over a non-linear stretching surface are developed in this article. An electrically conducting flow of viscous nanoliquid is considered. Heat transfer phenomenon is accounted under thermal radiation, Joule heating and viscous dissipation effects. We considered the variable heat flux condition at the surface of sheet. The governing mathematical equations are reduced to nonlinear ordinary differential systems through suitable dimensionless variables. A well-known shooting technique is implemented to obtain the results of dimensionless velocities and temperature. The obtained results are plotted for multiple values of pertinent parameters to discuss the salient features of these parameters on fluid velocity and temperature. The expressions of skin-friction coefficient and Nusselt number are computed and analyzed comprehensively through numerical values. A comparison of present results with the previous results in absence of nanoparticle volume fraction, mixed convection and magnetic field is computed and an excellent agreement noticed. We also computed the results for both linear and non-linear stretching sheet cases. - Highlights: • Hydromagnetic flow of nanofluid over a bidirectional non-linear stretching surface is examined. • Cu, Al 2 O3 and TiO 2 types nanoparticles are taken into account. • Numerical solutions have been computed and addressed. • The values of skin-friction and Nusselt number are presented.

  10. Evaluating the influence of plant-specific physiological parameterizations on the partitioning of land surface energy fluxes

    Science.gov (United States)

    Sulis, Mauro; Langensiepen, Matthias; Shrestha, Prabhakar; Schickling, Anke; Simmer, Clemens; Kollet, Stefan

    2015-04-01

    Vegetation has a significant influence on the partitioning of radiative forcing, the spatial and temporal variability of soil water and soil temperature. Therefore plant physiological properties play a key role in mediating and amplifying interactions and feedback mechanisms in the soil-vegetation-atmosphere continuum. Because of the direct impact on latent heat fluxes, these properties may also influence weather generating processes, such as the evolution of the atmospheric boundary layer (ABL). In land surface models, plant physiological properties are usually obtained from literature synthesis by unifying several plant/crop species in predefined vegetation classes. In this work, crop-specific physiological characteristics, retrieved from detailed field measurements, are included in the bio-physical parameterization of the Community Land Model (CLM), which is a component of the Terrestrial Systems Modeling Platform (TerrSysMP). The measured set of parameters for two typical European mid-latitudinal crops (sugar beet and winter wheat) is validated using eddy covariance measurements (sensible heat and latent heat) over multiple years from three measurement sites located in the North Rhine-Westphalia region, Germany. We found clear improvements of CLM simulations, when using the crop-specific physiological characteristics of the plants instead of the generic crop type when compared to the measurements. In particular, the increase of latent heat fluxes in conjunction with decreased sensible heat fluxes as simulated by the two new crop-specific parameter sets leads to an improved quantification of the diurnal energy partitioning. These findings are cross-validated using estimates of gross primary production extracted from net ecosystem exchange measurements. This independent analysis reveals that the better agreement between observed and simulated latent heat using the plant-specific physiological properties largely stems from an improved simulation of the

  11. Magnetic flux reconstruction methods for shaped tokamaks

    International Nuclear Information System (INIS)

    Tsui, Chi-Wa.

    1993-12-01

    The use of a variational method permits the Grad-Shafranov (GS) equation to be solved by reducing the problem of solving the 2D non-linear partial differential equation to the problem of minimizing a function of several variables. This high speed algorithm approximately solves the GS equation given a parameterization of the plasma boundary and the current profile (p' and FF' functions). The author treats the current profile parameters as unknowns. The goal is to reconstruct the internal magnetic flux surfaces of a tokamak plasma and the toroidal current density profile from the external magnetic measurements. This is a classic problem of inverse equilibrium determination. The current profile parameters can be evaluated by several different matching procedures. Matching of magnetic flux and field at the probe locations using the Biot-Savart law and magnetic Green's function provides a robust method of magnetic reconstruction. The matching of poloidal magnetic field on the plasma surface provides a unique method of identifying the plasma current profile. However, the power of this method is greatly compromised by the experimental errors of the magnetic signals. The Casing Principle provides a very fast way to evaluate the plasma contribution to the magnetic signals. It has the potential of being a fast matching method. The performance of this method is hindered by the accuracy of the poloidal magnetic field computed from the equilibrium solver. A flux reconstruction package has been implemented which integrates a vacuum field solver using a filament model for the plasma, a multi-layer perception neural network as an interface, and the volume integration of plasma current density using Green's functions as a matching method for the current profile parameters. The flux reconstruction package is applied to compare with the ASEQ and EFIT data. The results are promising

  12. An iterative procedure for estimating areally averaged heat flux using planetary boundary layer mixed layer height and locally measured heat flux

    Energy Technology Data Exchange (ETDEWEB)

    Coulter, R. L.; Gao, W.; Lesht, B. M.

    2000-04-04

    Measurements at the central facility of the Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) are intended to verify, improve, and develop parameterizations in radiative flux models that are subsequently used in General Circulation Models (GCMs). The reliability of this approach depends upon the representativeness of the local measurements at the central facility for the site as a whole or on how these measurements can be interpreted so as to accurately represent increasingly large scales. The variation of surface energy budget terms over the SGP CART site is extremely large. Surface layer measurements of the sensible heat flux (H) often vary by a factor of 2 or more at the CART site (Coulter et al. 1996). The Planetary Boundary Layer (PBL) effectively integrates the local inputs across large scales; because the mixed layer height (h) is principally driven by H, it can, in principal, be used for estimates of surface heat flux over scales on the order of tens of kilometers. By combining measurements of h from radiosondes or radar wind profiles with a one-dimensional model of mixed layer height, they are investigating the ability of diagnosing large-scale heat fluxes. The authors have developed a procedure using the model described by Boers et al. (1984) to investigate the effect of changes in surface sensible heat flux on the mixed layer height. The objective of the study is to invert the sense of the model.

  13. A Comparison between a Minijet Model and a Glasma Flux Tube Model for Central Au-Au Collisions at √(ovr sNN)=200 GeV

    International Nuclear Information System (INIS)

    Longacre, R.S.

    2011-01-01

    In this paper we compare two models with central Au-Au collisions at √(ovr s NN )=200 GeV. The first model is a minijet model which assumes that around ∼50 minijets are produced in back-to-back pairs and have an altered fragmentation functions. It is also assumed that the fragments are transparent and escape the collision zone and are detected. The second model is a glasma flux tube model which leads to flux tubes on the surface of a radial expanding fireball driven by interacting flux tubes near the center of the fireball through plasma instabilities. This internal fireball becomes an opaque hydro fluid which pushes the surface flux tubes outward. Around ∼12 surface flux tubes remain and fragment with ∼1/2 the produced particles escaping the collision zone and are detected. Both models can reproduce two particle angular correlations in the different p t1 p t2 bins. We also compare the two models for three additional effects: meson baryon ratios; the long range nearside correlation called the ridge; and the so-called mach cone effect when applied to three particle angular correlations.

  14. Flux agreement above a Scots pine plantation

    Science.gov (United States)

    Gay, L. W.; Vogt, R.; Bernhofer, Ch.; Blanford, J. H.

    1996-03-01

    The surface energy exchange of 12m high Scots pine plantation at Hartheim, Germany, was measured with a variety of methods during a 11-day period of fine weather in mid-May 1992. Net radiation and rate of thermal storage were measured with conventional net radiometers, soil heat flux discs and temperature-based storage models. The turbulent fluxes discussed in this report were obtained with an interchanging Bowen ratio energy budget system (BREB, at 14 m), two one-propeller eddy correlation systems (OPEC systems 1 and 2 at 17m), a 1-dimensional sonic eddy correlation system (SEC system 3) at 15 m, all on one “low” tower, and a 3-dimensional sonic eddy correlation system (SEC system 22) at 22 m on the “high” tower that was about 46 m distant. All systems measured sensible and latent heat (H and LE) directly, except for OPEC systems 1 and 2 which estimated LE as a residual term in the surface energy balance. Closure of turbulent fluxes from the two SEC systems was around 80% for daytime and 30% for night, with closure of 1-dimensional SEC system 3 exceeding that of 3-dimensional SEC system 22. The night measurements of turbulent fluxes contained considerable uncertainty, especially with the BREB system where measured gradients often yielded erroneous fluxes due to problems inherent in the method (i.e., computational instability as Bowen's ratio approaches -1). Also, both eddy correlation system designs (OPEC and SEC) appeared to underestimate |H| during stable conditions at night. In addition, both sonic systems (1- and 3-dimensional) underestimated |LE| during stable conditions. The underestimate of |H| at night generated residual estimates of OPEC LE containing a “phantom dew” error that erroneously decreased daily LE totals by about 10 percent. These special night problems are circumvented here by comparing results for daytime periods only, rather than for full days. To summarize, turbulent fluxes on the low tower from OPEC system 2 and the adjacent

  15. 1km Global Terrestrial Carbon Flux: Estimations and Evaluations

    Science.gov (United States)

    Murakami, K.; Sasai, T.; Kato, S.; Saito, M.; Matsunaga, T.; Hiraki, K.; Maksyutov, S. S.

    2017-12-01

    Estimating global scale of the terrestrial carbon flux change with high accuracy and high resolution is important to understand global environmental changes. Furthermore the estimations of the global spatiotemporal distribution may contribute to the political and social activities such as REDD+. In order to reveal the current state of terrestrial carbon fluxes covering all over the world and a decadal scale. The satellite-based diagnostic biosphere model is suitable for achieving this purpose owing to observing on the present global land surface condition uniformly at some time interval. In this study, we estimated the global terrestrial carbon fluxes with 1km grids by using the terrestrial biosphere model (BEAMS). And we evaluated our new carbon flux estimations on various spatial scales and showed the transition of forest carbon stocks in some regions. Because BEAMS required high resolution meteorological data and satellite data as input data, we made 1km interpolated data using a kriging method. The data used in this study were JRA-55, GPCP, GOSAT L4B atmospheric CO2 data as meteorological data, and MODIS land product as land surface satellite data. Interpolating process was performed on the meteorological data because of insufficient resolution, but not on MODIS data. We evaluated our new carbon flux estimations using the flux tower measurement (FLUXNET2015 Datasets) in a point scale. We used 166 sites data for evaluating our model results. These flux sites are classified following vegetation type (DBF, EBF, ENF, mixed forests, grass lands, croplands, shrub lands, Savannas, wetlands). In global scale, the BEAMS estimations was underestimated compared to the flux measurements in the case of carbon uptake and release. The monthly variations of NEP showed relatively high correlations in DBF and mixed forests, but the correlation coefficients of EBF, ENF, and grass lands were less than 0.5. In the meteorological factors, air temperature and solar radiation showed

  16. The effect of misleading surface temperature estimations on the sensible heat fluxes at a high Arctic site – the Arctic Turbulence Experiment 2006 on Svalbard (ARCTEX-2006

    Directory of Open Access Journals (Sweden)

    J. Lüers

    2010-01-01

    Full Text Available The observed rapid climate warming in the Arctic requires improvements in permafrost and carbon cycle monitoring, accomplished by setting up long-term observation sites with high-quality in-situ measurements of turbulent heat, water and carbon fluxes as well as soil physical parameters in Arctic landscapes. But accurate quantification and well adapted parameterizations of turbulent fluxes in polar environments presents fundamental problems in soil-snow-ice-vegetation-atmosphere interaction studies. One of these problems is the accurate estimation of the surface or aerodynamic temperature T(0 required to force most of the bulk aerodynamic formulae currently used. Results from the Arctic-Turbulence-Experiment (ARCTEX-2006 performed on Svalbard during the winter/spring transition 2006 helped to better understand the physical exchange and transport processes of energy. The existence of an atypical temperature profile close to the surface in the Arctic spring at Svalbard could be proven to be one of the major issues hindering estimation of the appropriate surface temperature. Thus, it is essential to adjust the set-up of measurement systems carefully when applying flux-gradient methods that are commonly used to force atmosphere-ocean/land-ice models. The results of a comparison of different sensible heat-flux parameterizations with direct measurements indicate that the use of a hydrodynamic three-layer temperature-profile model achieves the best fit and reproduces the temporal variability of the surface temperature better than other approaches.

  17. Impact of Convection on Surface Fluxes Observed During LASP/DYNAMO 2011

    Science.gov (United States)

    2014-12-01

    20  Figure 8.  FFM maneuver used in the LASP/DYNAMO experiment (from Wang et al. 2013...Atmosphere Response Experiment DYNAMO Dynamics of Madden-Julian Oscillation EM electro-magnetic EO electro-optical FFM flight-level flux mapping FVS...level flux mapping ( FFM ) modules. Convection modules consisted of dropsonde cloud survey or radar convective element maneuver. Dropsonde modules

  18. An updated climatology of surface dimethlysulfide concentrations and emission fluxes in the global ocean

    Science.gov (United States)

    Lana, A.; Bell, T. G.; Simó, R.; Vallina, S. M.; Ballabrera-Poy, J.; Kettle, A. J.; Dachs, J.; Bopp, L.; Saltzman, E. S.; Stefels, J.; Johnson, J. E.; Liss, P. S.

    2011-03-01

    The potentially significant role of the biogenic trace gas dimethylsulfide (DMS) in determining the Earth's radiation budget makes it necessary to accurately reproduce seawater DMS distribution and quantify its global flux across the sea/air interface. Following a threefold increase of data (from 15,000 to over 47,000) in the global surface ocean DMS database over the last decade, new global monthly climatologies of surface ocean DMS concentration and sea-to-air emission flux are presented as updates of those constructed 10 years ago. Interpolation/extrapolation techniques were applied to project the discrete concentration data onto a first guess field based on Longhurst's biogeographic provinces. Further objective analysis allowed us to obtain the final monthly maps. The new climatology projects DMS concentrations typically in the range of 1-7 nM, with higher levels occurring in the high latitudes, and with a general trend toward increasing concentration in summer. The increased size and distribution of the observations in the DMS database have produced in the new climatology substantially lower DMS concentrations in the polar latitudes and generally higher DMS concentrations in regions that were severely undersampled 10 years ago, such as the southern Indian Ocean. Using the new DMS concentration climatology in conjunction with state-of-the-art parameterizations for the sea/air gas transfer velocity and climatological wind fields, we estimate that 28.1 (17.6-34.4) Tg of sulfur are transferred from the oceans into the atmosphere annually in the form of DMS. This represents a global emission increase of 17% with respect to the equivalent calculation using the previous climatology. This new DMS climatology represents a valuable tool for atmospheric chemistry, climate, and Earth System models.

  19. An LES study on the spatial variability impact of surface sensible heat flux (SHF) on the convective boundary layer (CBL)

    Science.gov (United States)

    Kang, S. L.; Chun, J.; Kumar, A.

    2015-12-01

    We study the spatial variability impact of surface sensible heat flux (SHF) on the convective boundary layer (CBL), using the Weather Research and Forecasting (WRF) model in large eddy simulation (LES) mode. In order to investigate the response of the CBL to multi-scale feature of the surface SHF field over a local area of several tens of kilometers or smaller, an analytic surface SHF map is crated as a function of the chosen feature. The spatial variation in the SHF map is prescribed with a two-dimensional analytical perturbation field, which is generated by using the inverse transform technique of the Fourier series whose coefficients are controlled, of which spectrum to have a particular slope in the chosen range of wavelength. Then, the CBL responses to various SHF heterogeneities are summarized as a function of the spectral slope, in terms of mean structure, turbulence statistics and cross-scale processes. The range of feasible SHF heterogeneities is obtained from the SHF maps produced by a land surface model (LSM) of the WRF system. The LSM-derived SHF maps are a function of geographical data on various resolutions. Based on the numerical experiment results with the surface heterogeneities in the range, we will discuss the uncertainty in the SHF heterogeneity and its impact on the atmosphere in a numerical model. Also we will present the range of spatial scale of the surface SHF heterogeneity that significantly influence on the whole CBL. Lastly, we will report the test result of the hypothesis that the spatial variability of SHF is more representative of surface thermal heterogeneity than is the latent heat flux over the local area of several tens of kilometers or smaller.

  20. First-order chemistry in the surface-flux layer

    DEFF Research Database (Denmark)

    Kristensen, L.; Andersen, C.E.; Ejsing Jørgensen, Hans

    1997-01-01

    of a characteristic turbulent time scale and the scalar mean lifetime. We show that if we use only first-order closure and neglect the effect of the Damkohler ratio on the turbulent diffusivity we obtain another analytic solution for the profiles of the flux and the mean concentration which, from an experimental...

  1. Fast modeling of flux trapping cascaded explosively driven magnetic flux compression generators.

    Science.gov (United States)

    Wang, Yuwei; Zhang, Jiande; Chen, Dongqun; Cao, Shengguang; Li, Da; Liu, Chebo

    2013-01-01

    To predict the performance of flux trapping cascaded flux compression generators, a calculation model based on an equivalent circuit is investigated. The system circuit is analyzed according to its operation characteristics in different steps. Flux conservation coefficients are added to the driving terms of circuit differential equations to account for intrinsic flux losses. To calculate the currents in the circuit by solving the circuit equations, a simple zero-dimensional model is used to calculate the time-varying inductance and dc resistance of the generator. Then a fast computer code is programmed based on this calculation model. As an example, a two-staged flux trapping generator is simulated by using this computer code. Good agreements are achieved by comparing the simulation results with the measurements. Furthermore, it is obvious that this fast calculation model can be easily applied to predict performances of other flux trapping cascaded flux compression generators with complex structures such as conical stator or conical armature sections and so on for design purpose.

  2. A mobile detector for measurements of the atmospheric muon flux in underground sites

    Energy Technology Data Exchange (ETDEWEB)

    Mitrica, Bogdan, E-mail: mitrica@nipne.ro [Horia Hulubei National Institute for Physics and Nuclear Engineering, P.O.B. MG-6, 077125 Magurele (Romania); Margineanu, Romul; Stoica, Sabin; Petcu, Mirel; Brancus, Iliana [Horia Hulubei National Institute for Physics and Nuclear Engineering, P.O.B. MG-6, 077125 Magurele (Romania); Jipa, Alexandru; Lazanu, Ionel; Sima, Octavian [Department of Physics, University of Bucharest, P.O.B. MG-11 (Romania); Haungs, Andreas; Rebel, Heinigerd [Institut fur Kernphysik, Karlsruhe Institute of Technology - Campus North, 76021 Karlsruhe (Germany); Petre, Marian; Toma, Gabriel; Saftoiu, Alexandra; Stanca, Denis; Apostu, Ana; Gomoiu, Claudia [Horia Hulubei National Institute for Physics and Nuclear Engineering, P.O.B. MG-6, 077125 Magurele (Romania)

    2011-10-21

    Muons comprise an important contribution of the natural radiation dose in air (approx. 30 nSv/h of a total dose rate of 65-130 nSv/h), as well as in underground sites even when the flux and relative contribution are significantly reduced. The flux of muons observed underground can be used as an estimator for the depth in mwe (meter water equivalent) of the underground site. The water equivalent depth is important information to devise physics experiments feasible for a specific site. A mobile detector for performing measurements of the muon flux was developed in IFIN-HH, Bucharest. Consisting of two scintillator plates (approx. 0.9 m{sup 2}) which measure in coincidence, the detector is installed on a van which facilitates measurements at different locations at the surface or underground. The detector was used to determine muon fluxes at different sites in Romania. In particular, data were taken and the values of meter water equivalents were assessed for several locations at the salt mine in Slanic-Prahova, Romania. The measurements have been performed in two different galleries of the Slanic mine at different depths. In order to test the stability of the method, also measurements of the muon flux at the surface at different elevations were performed. The results were compared with predictions of Monte-Carlo simulations using the CORSIKA and MUSIC codes.

  3. A mobile detector for measurements of the atmospheric muon flux in underground sites

    International Nuclear Information System (INIS)

    Mitrica, Bogdan; Margineanu, Romul; Stoica, Sabin; Petcu, Mirel; Brancus, Iliana; Jipa, Alexandru; Lazanu, Ionel; Sima, Octavian; Haungs, Andreas; Rebel, Heinigerd; Petre, Marian; Toma, Gabriel; Saftoiu, Alexandra; Stanca, Denis; Apostu, Ana; Gomoiu, Claudia

    2011-01-01

    Muons comprise an important contribution of the natural radiation dose in air (approx. 30 nSv/h of a total dose rate of 65-130 nSv/h), as well as in underground sites even when the flux and relative contribution are significantly reduced. The flux of muons observed underground can be used as an estimator for the depth in mwe (meter water equivalent) of the underground site. The water equivalent depth is important information to devise physics experiments feasible for a specific site. A mobile detector for performing measurements of the muon flux was developed in IFIN-HH, Bucharest. Consisting of two scintillator plates (approx. 0.9 m 2 ) which measure in coincidence, the detector is installed on a van which facilitates measurements at different locations at the surface or underground. The detector was used to determine muon fluxes at different sites in Romania. In particular, data were taken and the values of meter water equivalents were assessed for several locations at the salt mine in Slanic-Prahova, Romania. The measurements have been performed in two different galleries of the Slanic mine at different depths. In order to test the stability of the method, also measurements of the muon flux at the surface at different elevations were performed. The results were compared with predictions of Monte-Carlo simulations using the CORSIKA and MUSIC codes.

  4. Comparison of eddy covariance and modified Bowen ratio methods for measuring gas fluxes and implications for measuring fluxes of persistent organic pollutants

    Directory of Open Access Journals (Sweden)

    D. J. Bolinius

    2016-04-01

    Full Text Available Semi-volatile persistent organic pollutants (POPs cycle between the atmosphere and terrestrial surfaces; however measuring fluxes of POPs between the atmosphere and other media is challenging. Sampling times of hours to days are required to accurately measure trace concentrations of POPs in the atmosphere, which rules out the use of eddy covariance techniques that are used to measure gas fluxes of major air pollutants. An alternative, the modified Bowen ratio (MBR method, has been used instead. In this study we used data from FLUXNET for CO2 and water vapor (H2O to compare fluxes measured by eddy covariance to fluxes measured with the MBR method using vertical concentration gradients in air derived from averaged data that simulate the long sampling times typically required to measure POPs. When concentration gradients are strong and fluxes are unidirectional, the MBR method and the eddy covariance method agree within a factor of 3 for CO2, and within a factor of 10 for H2O. To remain within the range of applicability of the MBR method, field studies should be carried out under conditions such that the direction of net flux does not change during the sampling period. If that condition is met, then the performance of the MBR method is neither strongly affected by the length of sample duration nor the use of a fixed value for the transfer coefficient.

  5. A simple formula for the net long-wave radiation flux in the southern Baltic Sea

    Directory of Open Access Journals (Sweden)

    Tomasz Zapadka

    2001-09-01

    Full Text Available This paper discusses problems of estimating the net long-wave radiation flux at the sea surface on the basis of easily measurable meteorological quantities (air and sea surface temperatures, near-surface water vapour pressure, cloudiness. Empirical data and existing formulae are compared. Additionally, an improved formula for the southern Baltic region is introduced, with a systematic error of less than 1 W -2 and a statistical error of less than 20 W -2.

  6. Neutron flux monitoring device

    International Nuclear Information System (INIS)

    Shimazu, Yoichiro.

    1995-01-01

    In a neutron flux monitoring device, there are disposed a neutron flux measuring means for outputting signals in accordance with the intensity of neutron fluxes, a calculation means for calculating a self power density spectrum at a frequency band suitable to an object to be measured based on the output of the neutron flux measuring means, an alarm set value generation means for outputting an alarm set value as a comparative reference, and an alarm judging means for comparing the alarm set value with the outputted value of the calculation means to judge requirement of generating an alarm and generate an alarm in accordance with the result of the judgement. Namely, the time-series of neutron flux signals is put to fourier transformation for a predetermined period of time by the calculation means, and from each of square sums for real number component and imaginary number component for each of the frequencies, a self power density spectrum in the frequency band suitable to the object to be measured is calculated. Then, when the set reference value is exceeded, an alarm is generated. This can reliably prevent generation of erroneous alarm due to neutron flux noises and can accurately generate an alarm at an appropriate time. (N.H.)

  7. Do We Really Need Sinusoidal Surface Temperatures to Apply Heat Tracing Techniques to Estimate Streambed Fluid Fluxes?

    Science.gov (United States)

    Luce, C. H.; Tonina, D.; Applebee, R.; DeWeese, T.

    2017-12-01

    Two common refrains about using the one-dimensional advection diffusion equation to estimate fluid fluxes, thermal conductivity, or bed surface elevation from temperature time series in streambeds are that the solution assumes that 1) the surface boundary condition is a sine wave or nearly so, and 2) there is no gradient in mean temperature with depth. Concerns on these subjects are phrased in various ways, including non-stationarity in frequency, amplitude, or phase. Although the mathematical posing of the original solution to the problem might lead one to believe these constraints exist, the perception that they are a source of error is a fallacy. Here we re-derive the inverse solution of the 1-D advection-diffusion equation starting with an arbitrary surface boundary condition for temperature. In doing so, we demonstrate the frequency-independence of the solution, meaning any single frequency can be used in the frequency-domain solutions to estimate thermal diffusivity and 1-D fluid flux in streambeds, even if the forcing has multiple frequencies. This means that diurnal variations with asymmetric shapes, gradients in the mean temperature with depth, or `non-stationary' amplitude and frequency (or phase) do not actually represent violations of assumptions, and they should not cause errors in estimates when using one of the suite of existing solution methods derived based on a single frequency. Misattribution of errors to these issues constrains progress on solving real sources of error. Numerical and physical experiments are used to verify this conclusion and consider the utility of information at `non-standard' frequencies and multiple frequencies to augment the information derived from time series of temperature.

  8. SURFACE ENERGY BALANCE OVER ORANGE ORCHARD USING SURFACE RENEWAL ANALYSIS

    Directory of Open Access Journals (Sweden)

    Salvatore Barbagallo

    2009-12-01

    Full Text Available Reliable estimation of surface sensible and latent heat flux is the most important process to appraise energy and mass exchange among atmosphere and biosphere. In this study the surface energy fluxes were measured over an irrigated orange orchard during 2005-2008 monitoring periods using a Surface Renewal- Energy Balance approach. The experimental area is located in a representative orchard growing area of eastern Sicily (Italy. The performance of Surface Renewal (SR analysis for estimating sensible heat flux (H was analysed and evaluated in terms of correlation with H fluxes from the eddy covariance (EC method. Study revealed that the mean available energy (RN- G and latent heat flux (LE were of about 300 W m-2 and 237 W m-2, respectively, during dry periods and unstable-case atmospheric conditions. The estimated crop coefficient Kc values for the orchard crop averaged close to 0.80, which is considerably higher than previous FAO studies that found the value to be 0.65 for citrus with 70% of ground cover. The intercepted photosynthetically active radiation (LI PAR by the crop was measured and relationships between LAI and crop coefficient (Kc were established.

  9. Visible imaging measurement of position and displacement of the last closed flux surface in EAST tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Y.F. [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230026 (China); Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Xu, G.S., E-mail: gsxu@ipp.ac.cn [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230026 (China); Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Li, Y.L.; Yang, J.H.; Yan, N.; Liu, L.; Yuan, S.; Luo, Z.P. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Sang, C.F. [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Gu, S.; Xu, J.C.; Hu, G.H.; Wang, Y.S. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Peng, Y.K.M.; Wan, B.N. [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230026 (China); Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China)

    2017-06-15

    Highlights: • A new method for measuring the position and displacement of the LCFS has been developed in EAST tokamak. • This method is based on the visible imaging diagnostic and shown to be an effective and convenient approach. • This method can be applied to measure displacements of the LCFS during application of resonant magnetic perturbation fields. - Abstract: A new method for measuring the position and displacement of the last closed flux surface (LCFS) with visible imaging diagnostics has been developed in EAST. By measuring the relative intensity profiles of the green visible Li-II emission in the tangential planes of the optical systems, it is possible to infer the positions of certain points on the LCFS. This emission line is readily available in discharges with Li-coating wall routinely employed to improve the plasma performance. We describe the measuring method, giving results which are compared with those obtained by EFIT, and showing this as an effective and convenient approach to determine the position of the LCFS. This method is further applied to measure the displacements of the LCFS during application of resonant magnetic perturbation fields in the EAST tokamak.

  10. The role of soil weathering and hydrology in regulating chemical fluxes from catchments (Invited)

    Science.gov (United States)

    Maher, K.; Chamberlain, C. P.

    2010-12-01

    Catchment-scale chemical fluxes have been linked to a number of different parameters that describe the conditions at the Earth’s surface, including runoff, temperature, rock type, vegetation, and the rate of tectonic uplift. However, many of the relationships relating chemical denudation to surface processes and conditions, while based on established theoretical principles, are largely empirical and derived solely from modern observations. Thus, an enhanced mechanistic basis for linking global solute fluxes to both surface processes and climate may improve our confidence in extrapolating modern solute fluxes to past and future conditions. One approach is to link observations from detailed soil-based studies with catchment-scale properties. For example, a number of recent studies of chemical weathering at the soil-profile scale have reinforced the importance of hydrologic processes in controlling chemical weathering rates. An analysis of data from granitic soils shows that weathering rates decrease with increasing fluid residence times and decreasing flow rates—over moderate fluid residence times, from 5 days to 10 years, transport-controlled weathering explains the orders of magnitude variation in weathering rates to a better extent than soil age. However, the importance of transport-controlled weathering is difficult to discern at the catchment scale because of the range of flow rates and fluid residence times captured by a single discharge or solute flux measurement. To assess the importance of transport-controlled weathering on catchment scale chemical fluxes, we present a model that links the chemical flux to the extent of reaction between the soil waters and the solids, or the fluid residence time. Different approaches for describing the distribution of fluid residence times within a catchment are then compared with the observed Si fluxes for a limited number of catchments. This model predicts high solute fluxes in regions with high run-off, relief, and

  11. Evaluations of carbon fluxes estimated by top-down and bottom-up approaches

    Science.gov (United States)

    Murakami, K.; Sasai, T.; Kato, S.; Hiraki, K.; Maksyutov, S. S.; Yokota, T.; Nasahara, K.; Matsunaga, T.

    2013-12-01

    There are two types of estimating carbon fluxes using satellite observation data, and these are referred to as top-down and bottom-up approaches. Many uncertainties are however still remain in these carbon flux estimations, because the true values of carbon flux are still unclear and estimations vary according to the type of the model (e.g. a transport model, a process based model) and input data. The CO2 fluxes in these approaches are estimated by using different satellite data such as the distribution of CO2 concentration in the top-down approach and the land cover information (e.g. leaf area, surface temperature) in the bottom-up approach. The satellite-based CO2 flux estimations with reduced uncertainty can be used efficiently for identifications of large emission area and carbon stocks of forest area. In this study, we evaluated the carbon flux estimates from two approaches by comparing with each other. The Greenhouse gases Observing SATellite (GOSAT) has been observing atmospheric CO2 concentrations since 2009. GOSAT L4A data product is the monthly CO2 flux estimations for 64 sub-continental regions and is estimated by using GOSAT FTS SWIR L2 XCO2 data and atmospheric tracer transport model. We used GOSAT L4A CO2 flux as top-down approach estimations and net ecosystem productions (NEP) estimated by the diagnostic type biosphere model BEAMS as bottom-up approach estimations. BEAMS NEP is only natural land CO2 flux, so we used GOSAT L4A CO2 flux after subtraction of anthropogenic CO2 emissions and oceanic CO2 flux. We compared with two approach in temperate north-east Asia region. This region is covered by grassland and crop land (about 60 %), forest (about 20 %) and bare ground (about 20 %). The temporal variation for one year period was indicated similar trends between two approaches. Furthermore we show the comparison of CO2 flux estimations in other sub-continental regions.

  12. Estimation of Atmospheric Methane Surface Fluxes Using a Global 3-D Chemical Transport Model

    Science.gov (United States)

    Chen, Y.; Prinn, R.

    2003-12-01

    Accurate determination of atmospheric methane surface fluxes is an important and challenging problem in global biogeochemical cycles. We use inverse modeling to estimate annual, seasonal, and interannual CH4 fluxes between 1996 and 2001. The fluxes include 7 time-varying seasonal (3 wetland, rice, and 3 biomass burning) and 3 steady aseasonal (animals/waste, coal, and gas) global processes. To simulate atmospheric methane, we use the 3-D chemical transport model MATCH driven by NCEP reanalyzed observed winds at a resolution of T42 ( ˜2.8° x 2.8° ) in the horizontal and 28 levels (1000 - 3 mb) in the vertical. By combining existing datasets of individual processes, we construct a reference emissions field that represents our prior guess of the total CH4 surface flux. For the methane sink, we use a prescribed, annually-repeating OH field scaled to fit methyl chloroform observations. MATCH is used to produce both the reference run from the reference emissions, and the time-dependent sensitivities that relate individual emission processes to observations. The observational data include CH4 time-series from ˜15 high-frequency (in-situ) and ˜50 low-frequency (flask) observing sites. Most of the high-frequency data, at a time resolution of 40-60 minutes, have not previously been used in global scale inversions. In the inversion, the high-frequency data generally have greater weight than the weekly flask data because they better define the observational monthly means. The Kalman Filter is used as the optimal inversion technique to solve for emissions between 1996-2001. At each step in the inversion, new monthly observations are utilized and new emissions estimates are produced. The optimized emissions represent deviations from the reference emissions that lead to a better fit to the observations. The seasonal processes are optimized for each month, and contain the methane seasonality and interannual variability. The aseasonal processes, which are less variable, are

  13. Effects of radiation and thermal diffusivity on heat transfer over a stretching surface with variable heat flux

    International Nuclear Information System (INIS)

    Seddeek, M.A.; Abdelmeguid, M.S.

    2006-01-01

    The effect of radiation and thermal diffusivity on heat transfer over a stretching surface with variable heat flux has been studied. The thermal diffusivity is assumed to vary as a linear function of temperature. The governing partial differential equations have been transformed to ordinary differential equations. The exact analytical solution for the velocity and the numerical solution for the temperature field are given. Numerical solutions are obtained for different values of variable thermal diffusivity, radiation, temperature parameter and Prandtl number

  14. Prediction of turbulent heat transfer with surface blowing using a non-linear algebraic heat flux model

    International Nuclear Information System (INIS)

    Bataille, F.; Younis, B.A.; Bellettre, J.; Lallemand, A.

    2003-01-01

    The paper reports on the prediction of the effects of blowing on the evolution of the thermal and velocity fields in a flat-plate turbulent boundary layer developing over a porous surface. Closure of the time-averaged equations governing the transport of momentum and thermal energy is achieved using a complete Reynolds-stress transport model for the turbulent stresses and a non-linear, algebraic and explicit model for the turbulent heat fluxes. The latter model accounts explicitly for the dependence of the turbulent heat fluxes on the gradients of mean velocity. Results are reported for the case of a heated boundary layer which is first developed into equilibrium over a smooth impervious wall before encountering a porous section through which cooler fluid is continuously injected. Comparisons are made with LDA measurements for an injection rate of 1%. The reduction of the wall shear stress with increase in injection rate is obtained in the calculations, and the computed rates of heat transfer between the hot flow and the wall are found to agree well with the published data

  15. AVERAGE FLUXES FROM HETEROGENEOUS VEGETATED REGIONS

    NARCIS (Netherlands)

    KLAASSEN, W

    Using a surface-layer model, fluxes of heat and momentum have been calculated for flat regions with regularly spaced step changes in surface roughness and stomatal resistance. The distance between successive step changes is limited to 10 km in order to fill the gap between micro-meteorological

  16. User's guide for SLWDN9, a code for calculating flux-surfaced-averaging of alpha densities, currents, and heating in non-circular tokamaks

    International Nuclear Information System (INIS)

    Hively, L.M.; Miley, G.M.

    1980-03-01

    The code calculates flux-surfaced-averaged values of alpha density, current, and electron/ion heating profiles in realistic, non-circular tokamak plasmas. The code is written in FORTRAN and execute on the CRAY-1 machine at the Magnetic Fusion Energy Computer Center

  17. Diagnostics comparing sea surface temperature feedbacks from operational hurricane forecasts to observations

    Directory of Open Access Journals (Sweden)

    Ian D. Lloyd

    2011-11-01

    Full Text Available This paper examines the ability of recent versions of the Geophysical Fluid Dynamics Laboratory Operational Hurricane Forecast Model (GHM to reproduce the observed relationship between hurricane intensity and hurricane-induced Sea Surface Temperature (SST cooling. The analysis was performed by taking a Lagrangian composite of all hurricanes in the North Atlantic from 1998–2009 in observations and 2005–2009 for the GHM. A marked improvement in the intensity-SST relationship for the GHM compared to observations was found between the years 2005 and 2006–2009 due to the introduction of warm-core eddies, a representation of the loop current, and changes to the drag coefficient parameterization for bulk turbulent flux computation. A Conceptual Hurricane Intensity Model illustrates the essential steady-state characteristics of the intensity-SST relationship and is explained by two coupled equations for the atmosphere and ocean. The conceptual model qualitatively matches observations and the 2006–2009 period in the GHM, and presents supporting evidence for the conclusion that weaker upper oceanic thermal stratification in the Gulf of Mexico, caused by the introduction of the loop current and warm core eddies, is crucial to explaining the observed SST-intensity pattern. The diagnostics proposed by the conceptual model offer an independent set of metrics for comparing operational hurricane forecast models to observations.

  18. Numerical solutions for magnetohydrodynamic flow of nanofluid over a bidirectional non-linear stretching surface with prescribed surface heat flux boundary

    Energy Technology Data Exchange (ETDEWEB)

    Mahanthesh, B., E-mail: bmanths@gmail.com [Department of Mathematics, AIMS Institutes, Peenya, 560058 Bangalore (India); Department of Studies and Research in Mathematics, Kuvempu University, Shankaraghatta, 577451 Shimoga, Karnataka (India); Gireesha, B.J., E-mail: bjgireesu@rediffmail.com [Department of Studies and Research in Mathematics, Kuvempu University, Shankaraghatta, 577451 Shimoga, Karnataka (India); Department of Mechanical Engineering, Cleveland State University, Cleveland, OH (United States); Gorla, R.S. Reddy, E-mail: r.gorla@csuohio.edu [Department of Mechanical Engineering, Cleveland State University, Cleveland, OH (United States); Abbasi, F.M., E-mail: abbasisarkar@gmail.com [Department of Mathematics, Comsats Institute of Information Technology, Islamabad 44000 (Pakistan); Shehzad, S.A., E-mail: ali_qau70@yahoo.com [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan)

    2016-11-01

    Numerical solutions of three-dimensional flow over a non-linear stretching surface are developed in this article. An electrically conducting flow of viscous nanoliquid is considered. Heat transfer phenomenon is accounted under thermal radiation, Joule heating and viscous dissipation effects. We considered the variable heat flux condition at the surface of sheet. The governing mathematical equations are reduced to nonlinear ordinary differential systems through suitable dimensionless variables. A well-known shooting technique is implemented to obtain the results of dimensionless velocities and temperature. The obtained results are plotted for multiple values of pertinent parameters to discuss the salient features of these parameters on fluid velocity and temperature. The expressions of skin-friction coefficient and Nusselt number are computed and analyzed comprehensively through numerical values. A comparison of present results with the previous results in absence of nanoparticle volume fraction, mixed convection and magnetic field is computed and an excellent agreement noticed. We also computed the results for both linear and non-linear stretching sheet cases. - Highlights: • Hydromagnetic flow of nanofluid over a bidirectional non-linear stretching surface is examined. • Cu, Al{sub 2}O3 and TiO{sub 2} types nanoparticles are taken into account. • Numerical solutions have been computed and addressed. • The values of skin-friction and Nusselt number are presented.

  19. Effects of tropospheric aerosols on radiative flux calculations at UV and visible wavelengths

    International Nuclear Information System (INIS)

    Grossman, A.S.; Grant, K.E.

    1994-08-01

    The surface fluxes in the wavelength range 175 to 735nm have been calculated for an atmosphere which contains a uniformly mixed aerosol layer of thickness 1km at the earth's surface. Two different aerosol types were considered, a rural aerosol, and an urban aerosol. The visibility range for the aerosol layers was 95 to 15 km. Surface flux ratios (15km/95km) were in agreement with previously published results for the rural aerosol layer to within about 2%. The surface flux ratios vary from 7 to 14% for the rural aerosol layer and from 13 to 23% for the urban aerosol layer over the wavelength range. A tropospheric radiative forcing of about 1.3% of the total tropospheric flux was determined for the 95km to 15km visibility change in the rural aerosol layer, indicating the potential of tropospheric feedback effects on the surface flux changes. This effect was found to be negligible for the urban aerosol layer. Stratospheric layer heating rate changes due to visibility changes in either the rural or urban aerosol layer were found to be negligible

  20. The FluxCompensator: Making Radiative Transfer Models of Hydrodynamical Simulations Directly Comparable to Real Observations

    Science.gov (United States)

    Koepferl, Christine M.; Robitaille, Thomas P.

    2017-11-01

    When modeling astronomical objects throughout the universe, it is important to correctly treat the limitations of the data, for instance finite resolution and sensitivity. In order to simulate these effects, and to make radiative transfer models directly comparable to real observations, we have developed an open-source Python package called the FluxCompensator that enables the post-processing of the output of 3D Monte Carlo radiative transfer codes, such as Hyperion. With the FluxCompensator, realistic synthetic observations can be generated by modeling the effects of convolution with arbitrary point-spread functions, transmission curves, finite pixel resolution, noise, and reddening. Pipelines can be applied to compute synthetic observations that simulate observatories, such as the Spitzer Space Telescope or the Herschel Space Observatory. Additionally, this tool can read in existing observations (e.g., FITS format) and use the same settings for the synthetic observations. In this paper, we describe the package as well as present examples of such synthetic observations.

  1. The FluxCompensator: Making Radiative Transfer Models of Hydrodynamical Simulations Directly Comparable to Real Observations

    Energy Technology Data Exchange (ETDEWEB)

    Koepferl, Christine M.; Robitaille, Thomas P., E-mail: koepferl@usm.lmu.de [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany)

    2017-11-01

    When modeling astronomical objects throughout the universe, it is important to correctly treat the limitations of the data, for instance finite resolution and sensitivity. In order to simulate these effects, and to make radiative transfer models directly comparable to real observations, we have developed an open-source Python package called the FluxCompensator that enables the post-processing of the output of 3D Monte Carlo radiative transfer codes, such as Hyperion. With the FluxCompensator, realistic synthetic observations can be generated by modeling the effects of convolution with arbitrary point-spread functions, transmission curves, finite pixel resolution, noise, and reddening. Pipelines can be applied to compute synthetic observations that simulate observatories, such as the Spitzer Space Telescope or the Herschel Space Observatory . Additionally, this tool can read in existing observations (e.g., FITS format) and use the same settings for the synthetic observations. In this paper, we describe the package as well as present examples of such synthetic observations.

  2. Atmospheric and oceanic dust fluxes in the northeastern tropical Atlantic Ocean: how close a coupling?

    Directory of Open Access Journals (Sweden)

    A. Bory

    2002-12-01

    Full Text Available Atmospheric inputs to the ocean of dust originating from Africa are compared with downward dust flux in the oceanic water column. Atmospheric fluxes were estimated using remote-sensing-derived dust optical thickness and parameters from a transport/deposition model (TM2z. Oceanic fluxes were measured directly over/in two regions of contrasting primary productivity of the northeastern tropical Atlantic (one mesotrophic and one oligotrophic, located at about 500 and 1500 km off Mauritania underlying the offshore dust plume. In both regions, estimates of annual atmospheric dust inputs to the ocean surface are lower than, but of the same order of magnitude as, oceanic fluxes (49.5 and 8.8 mg.m-2 .d-1 in the mesotrophic and oligotrophic regions. Part of this mismatch may reflect both a general flaw in the dust grain size distribution used in transport models, which likely underestimates large particles, and/or lateral advection to each region of dustier surface waters from upstream, where dust deposition is higher. Higher-frequency temporal coupling between atmospheric and oceanic fluxes seems to be primary-productivity dependent, as hypothesized in previously reported studies.Key words. Atmospheric composition and structure (aerosols and particles; geochemical cycles Oceanography: biological and chemical (geochemistry

  3. Analytical characterization of selective benthic flux components in estuarine and coastal waters

    Science.gov (United States)

    King, Jeffrey N.

    2011-01-01

    Benthic flux is the rate of flow across the bed of a water body, per unit area of bed. It is forced by component mechanisms, which interact. For example, pressure gradients across the bed, forced by tide, surface gravity waves, density gradients, bed–current interaction, turbulence, and terrestrial hydraulic gradients, drive an advective benthic flux of water and constituents between estuarine and coastal waters, and surficial aquifers. Other mechanisms also force benthic flux, such as chemical gradients, bioturbation, and dispersion. A suite of component mechanisms force a total benthic flux at any given location, where each member of the suite contributes a component benthic flux. Currently, the types and characteristics of component interactions are not fully understood. For example, components may interact linearly or nonlinearly, and the interaction may be constructive or destructive. Benthic flux is a surface water–groundwater interaction process. Its discharge component to a marine water body is referred to, in some literature, as submarine groundwater discharge. Benthic flux is important in characterizing water and constituent budgets of estuarine and coastal systems. Analytical models to characterize selective benthic flux components are reviewed. Specifically, these mechanisms are for the component associated with the groundwater tidal prism, and forced by surface gravity wave setup, surface gravity waves on a plane bed, and the terrestrial hydraulic gradient. Analytical models are applied to the Indian River Lagoon, Florida; Great South Bay, New York; and the South Atlantic Bight in South Carolina and portions of North Carolina.

  4. Importance of Preserving Cross-correlation in developing Statistically Downscaled Climate Forcings and in estimating Land-surface Fluxes and States

    Science.gov (United States)

    Das Bhowmik, R.; Arumugam, S.

    2015-12-01

    Multivariate downscaling techniques exhibited superiority over univariate regression schemes in terms of preserving cross-correlations between multiple variables- precipitation and temperature - from GCMs. This study focuses on two aspects: (a) develop an analytical solutions on estimating biases in cross-correlations from univariate downscaling approaches and (b) quantify the uncertainty in land-surface states and fluxes due to biases in cross-correlations in downscaled climate forcings. Both these aspects are evaluated using climate forcings available from both historical climate simulations and CMIP5 hindcasts over the entire US. The analytical solution basically relates the univariate regression parameters, co-efficient of determination of regression and the co-variance ratio between GCM and downscaled values. The analytical solutions are compared with the downscaled univariate forcings by choosing the desired p-value (Type-1 error) in preserving the observed cross-correlation. . For quantifying the impacts of biases on cross-correlation on estimating streamflow and groundwater, we corrupt the downscaled climate forcings with different cross-correlation structure.

  5. Surface energy and radiation balance systems - General description and improvements

    Science.gov (United States)

    Fritschen, Leo J.; Simpson, James R.

    1989-01-01

    Surface evaluation of sensible and latent heat flux densities and the components of the radiation balance were desired for various vegetative surfaces during the ASCOT84 experiment to compare with modeled results and to relate these values to drainage winds. Five battery operated data systems equipped with sensors to determine the above values were operated for 105 station days during the ASCOT84 experiment. The Bowen ratio energy balance technique was used to partition the available energy into the sensible and latent heat flux densities. A description of the sensors and battery operated equipment used to collect and process the data is presented. In addition, improvements and modifications made since the 1984 experiment are given. Details of calculations of soil heat flow at the surface and an alternate method to calculate sensible and latent heat flux densities are provided.

  6. Window Material Daylighting Performance Assessment Algorithm: Comparing Radiosity and Split-Flux Methods

    Directory of Open Access Journals (Sweden)

    Yeo Beom Yoon

    2014-04-01

    Full Text Available Windows are the primary aperture to introduce solar radiation to the interior space of a building. This experiment explores the use of EnergyPlus software for analyzing the illuminance level on the floor of a room with reference to its distance from the window. For this experiment, a double clear glass window has been used. The preliminary modelling in EnergyPlus showed a consistent result with the experimentally monitored data in real time. EnergyPlus has two mainly used daylighting algorithms: DElight method employing radiosity technique and Detailed method employing split-flux technique. Further analysis for illuminance using DElight and Detailed methods showed significant difference in the results. Finally, we compared the algorithms of the two analysis methods in EnergyPlus.

  7. Cabauw Experimental Results from the Project for Intercomparison of Land-Surface Parameterization Schemes.

    Science.gov (United States)

    Chen, T. H.; Henderson-Sellers, A.; Milly, P. C. D.; Pitman, A. J.; Beljaars, A. C. M.; Polcher, J.; Abramopoulos, F.; Boone, A.; Chang, S.; Chen, F.; Dai, Y.; Desborough, C. E.; Dickinson, R. E.; Dümenil, L.; Ek, M.; Garratt, J. R.; Gedney, N.; Gusev, Y. M.;  Kim, J.;  Koster, R.;  Kowalczyk, E. A.;  Laval, K.;  Lean, J.;  Lettenmaier, D.;  Liang, X.;  Mahfouf, J.-F.;  Mengelkamp, H.-T.;  Mitchell, K.;  Nasonova, O. N.;  Noilhan, J.;  Robock, A.;  Rosenzweig, C.;  Schaake, J.;  Schlosser, C. A.;  Schulz, J.-P.;  Shao, Y.;  Shmakin, A. B.;  Verseghy, D. L.;  Wetzel, P.;  Wood, E. F.;  Xue, Y.;  Yang, Z.-L.;  Zeng, Q.

    1997-06-01

    In the Project for Intercomparison of Land-Surface Parameterization Schemes phase 2a experiment, meteorological data for the year 1987 from Cabauw, the Netherlands, were used as inputs to 23 land-surface flux schemes designed for use in climate and weather models. Schemes were evaluated by comparing their outputs with long-term measurements of surface sensible heat fluxes into the atmosphere and the ground, and of upward longwave radiation and total net radiative fluxes, and also comparing them with latent heat fluxes derived from a surface energy balance. Tuning of schemes by use of the observed flux data was not permitted. On an annual basis, the predicted surface radiative temperature exhibits a range of 2 K across schemes, consistent with the range of about 10 W m2 in predicted surface net radiation. Most modeled values of monthly net radiation differ from the observations by less than the estimated maximum monthly observational error (±10 W m2). However, modeled radiative surface temperature appears to have a systematic positive bias in most schemes; this might be explained by an error in assumed emissivity and by models' neglect of canopy thermal heterogeneity. Annual means of sensible and latent heat fluxes, into which net radiation is partitioned, have ranges across schemes of30 W m2 and 25 W m2, respectively. Annual totals of evapotranspiration and runoff, into which the precipitation is partitioned, both have ranges of 315 mm. These ranges in annual heat and water fluxes were approximately halved upon exclusion of the three schemes that have no stomatal resistance under non-water-stressed conditions. Many schemes tend to underestimate latent heat flux and overestimate sensible heat flux in summer, with a reverse tendency in winter. For six schemes, root-mean-square deviations of predictions from monthly observations are less than the estimated upper bounds on observation errors (5 W m2 for sensible heat flux and 10 W m2 for latent heat flux). Actual

  8. A comprehensive set of benchmark tests for a land surface model of simultaneous fluxes of water and carbon at both the global and seasonal scale

    Directory of Open Access Journals (Sweden)

    E. Blyth

    2011-04-01

    Full Text Available Evaluating the models we use in prediction is important as it allows us to identify uncertainties in prediction as well as guiding the priorities for model development. This paper describes a set of benchmark tests that is designed to quantify the performance of the land surface model that is used in the UK Hadley Centre General Circulation Model (JULES: Joint UK Land Environment Simulator. The tests are designed to assess the ability of the model to reproduce the observed fluxes of water and carbon at the global and regional spatial scale, and on a seasonal basis. Five datasets are used to test the model: water and carbon dioxide fluxes from ten FLUXNET sites covering the major global biomes, atmospheric carbon dioxide concentrations at four representative stations from the global network, river flow from seven catchments, the seasonal mean NDVI over the seven catchments and the potential land cover of the globe (after the estimated anthropogenic changes have been removed. The model is run in various configurations and results are compared with the data.

    A few examples are chosen to demonstrate the importance of using combined use of observations of carbon and water fluxes in essential in order to understand the causes of model errors. The benchmarking approach is suitable for application to other global models.

  9. Net Ecosystem Fluxes of Hydrocarbons from a Ponderosa Pine Forest in Colorado

    Science.gov (United States)

    Rhew, R. C.; Turnipseed, A. A.; Ortega, J. V.; Smith, J. N.; Guenther, A. B.; Shen, S.; Martinez, L.; Koss, A.; Warneke, C.; De Gouw, J. A.; Deventer, M. J.

    2015-12-01

    Light (C2-C4) alkenes, light alkanes and isoprene (C5H8) are non-methane hydrocarbons that play important roles in the photochemical production of tropospheric ozone and in the formation of secondary organic aerosols. Natural terrestrial fluxes of the light hydrocarbons are poorly characterized, with global emission estimates based on limited field measurements. In 2014, net fluxes of these compounds were measured at the Manitou Experimental Forest Observatory, a semi-arid ponderosa pine forest in the Colorado Rocky Mountains and site of the prior BEACHON campaigns. Three field intensives were conducted between June 17 and August 10, 2014. Net ecosystem flux measurements utilized a relaxed eddy accumulation system coupled to an automated gas chromatograph. Summertime average emissions of ethene and propene were up to 90% larger than those observed from a temperate deciduous forest. Ethene and propene fluxes were also correlated to each other, similar to the deciduous forest study. Emissions of isoprene were small, as expected for a coniferous forest, and these fluxes were not correlated with either ethene or propene. Unexpected emissions of light alkanes were also observed, and these showed a distinct diurnal cycle. Understory flux measurements allowed for the partitioning of fluxes between the surface and the canopy. Full results from the three field intensives will be compared with environmental variables in order to parameterize the fluxes for use in modeling emissions.

  10. Eddy Correlation Flux Measurement System (ECOR) Handbook

    Energy Technology Data Exchange (ETDEWEB)

    Cook, DR

    2011-01-31

    The eddy correlation (ECOR) flux measurement system provides in situ, half-hour measurements of the surface turbulent fluxes of momentum, sensible heat, latent heat, and carbon dioxide (CO2) (and methane at one Southern Great Plains extended facility (SGP EF) and the North Slope of Alaska Central Facility (NSA CF). The fluxes are obtained with the eddy covariance technique, which involves correlation of the vertical wind component with the horizontal wind component, the air temperature, the water vapor density, and the CO2 concentration.

  11. Global observations and modeling of atmosphere-surface exchange of elemental mercury: a critical review

    Science.gov (United States)

    Zhu, Wei; Lin, Che-Jen; Wang, Xun; Sommar, Jonas; Fu, Xuewu; Feng, Xinbin

    2016-04-01

    Reliable quantification of air-surface fluxes of elemental Hg vapor (Hg0) is crucial for understanding mercury (Hg) global biogeochemical cycles. There have been extensive measurements and modeling efforts devoted to estimating the exchange fluxes between the atmosphere and various surfaces (e.g., soil, canopies, water, snow, etc.) in the past three decades. However, large uncertainties remain due to the complexity of Hg0 bidirectional exchange, limitations of flux quantification techniques and challenges in model parameterization. In this study, we provide a critical review on the state of science in the atmosphere-surface exchange of Hg0. Specifically, the advancement of flux quantification techniques, mechanisms in driving the air-surface Hg exchange and modeling efforts are presented. Due to the semi-volatile nature of Hg0 and redox transformation of Hg in environmental media, Hg deposition and evasion are influenced by multiple environmental variables including seasonality, vegetative coverage and its life cycle, temperature, light, moisture, atmospheric turbulence and the presence of reactants (e.g., O3, radicals, etc.). However, the effects of these processes on flux have not been fundamentally and quantitatively determined, which limits the accuracy of flux modeling. We compile an up-to-date global observational flux database and discuss the implication of flux data on the global Hg budget. Mean Hg0 fluxes obtained by micrometeorological measurements do not appear to be significantly greater than the fluxes measured by dynamic flux chamber methods over unpolluted surfaces (p = 0.16, one-tailed, Mann-Whitney U test). The spatiotemporal coverage of existing Hg0 flux measurements is highly heterogeneous with large data gaps existing in multiple continents (Africa, South Asia, Middle East, South America and Australia). The magnitude of the evasion flux is strongly enhanced by human activities, particularly at contaminated sites. Hg0 flux observations in East

  12. Surface and Tethered-Balloon Observations of Actinic Flux: Effects of Arctic stratus, Surface Albedo and Solar Zenith Angle

    NARCIS (Netherlands)

    Roode, S.R. de; Duynkerke, P.G.; Boot, Wim; Hage, Jeroen C.H. van der

    2000-01-01

    As part of the FIRE III (First ISCCP Regional Experiment) Arctic Cloud Experiment actinic flux measurements were made above the Arctic Sea ice during May 1998. FIRE III was designed to address questions concerning clouds, radiation and chemistry in the Arctic sea ice region. The actinic flux,

  13. Fabrication of high flux and antifouling mixed matrix fumarate-alumoxane/PAN membranes via electrospinning for application in membrane bioreactors

    Science.gov (United States)

    Moradi, Golshan; Zinadini, Sirus; Rajabi, Laleh; Dadari, Soheil

    2018-01-01

    The nanofibrous Polyacrylonitrile (PAN) membranes embedded with fumarate-alumoxane (Fum-A) nanoparticles were prepared via electrospinning technique as high flux and antifouling membranes for membrane bioreactor (MBR) applications. The effect of Fum-A nanoparticles on membrane morphology, surface hydrophilicity, pure water flux, effluent turbidity and the antifouling property was investigated. Fum-A is a carboxylate-alumoxane nanoparticle covered by extra hydroxyl and carboxylate groups on its surface. By embedding Fum-A nanoparticles into the spinning solution, the surface hydrophilicity and pure water flux of the resulted membranes were improved. The smooth surface of fibers at the low amount of nanoparticles and the agglomeration of nanoparticles at their high concentration were shown in SEM images of the membranes surface. The energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) analysis of the prepared Fum-A/PAN membrane confirmed the presence of carboxylate and hydroxyl functional groups of Fum-A nanoparticles on the surface of the Fum-A nanoparticles containing membrane. The results obtained from the filtration of activated sludge suspension revealed that by addition of a low amount of Fum-A nanoparticles, the irreversible fouling was significantly decreased due to the higher hydrophilicity. The Fum-A/PAN membranes showed superior permeate flux and antifouling properties compared to bare electrospun PAN membrane. Finally, 2 wt.% Fum-A/PAN membrane exhibited the highest FRR of 96% and the lowest irreversible fouling of 4% with excellent durability of antifouling property during twenty repeated activated sludge filtrations.

  14. A comparison of UV surface brightness and HI surface densities for spiral galaxies

    International Nuclear Information System (INIS)

    Federman, S.R.; Strom, C.

    1990-01-01

    Shaya and Federman (1987) suggested that the ambient ultraviolet flux at 1000 A permeating a spiral galaxy controls the neutral hydrogen (HI) surface density in the galaxy. They found that the atomic envelopes surrounding small molecular clouds, because of their great number, provide the major contribution to the HI surface density over the stellar disk. The increase in HI surface density with later Hubble types was ascribed to the stronger UV fields from more high-mass stars in later Hubble types. These hypotheses are based on the observations of nearby diffuse interstellar clouds, which show a sharp atomic-to-molecular transition (Savage et al. 1977), and on the theoretical framework introduced by Federman, Glassgold, and Kwan (1979). Atomic envelopes around interstellar clouds in the solar neighborhood arise when a steady state is reached between photodissociation of H2 and the formation of H2 on grains. The photodissociation process involves photons with wavelengths between 912 A and 1108 A. Shaya and Federman used H-alpha flux as an approximate measure for the far UV flux and made their comparisons based on averages over Hubble type. Here, researchers compare, on an individual basis, UV data obtained with space-borne and balloon-borne instruments for galaxies with measurements of HI surface density (Warmels 1988a, b). The comparisons substantiate the conclusion of Shaya and Federman that the far UV field controls the HI content of spiral galaxies

  15. Freshwater flux to Sermilik Fjord, SE Greenland

    Directory of Open Access Journals (Sweden)

    S. H. Mernild

    2010-10-01

    Full Text Available Terrestrial inputs of freshwater flux to Sermilik Fjord, SE Greenland, were estimated, indicating ice discharge to be the dominant source of freshwater. A freshwater flux of 40.4 ± 4.9×109 m3 y−1 was found (1999–2008, with an 85% contribution originated from ice discharge (65% alone from Helheim Glacier, 11% from terrestrial surface runoff (from melt water and rain, 3% from precipitation at the fjord surface area, and 1% from subglacial geothermal and frictional melting due to basal ice motion. The results demonstrate the dominance of ice discharge as a primary mechanism for delivering freshwater to Sermilik Fjord. Time series of ice discharge for Helheim Glacier, Midgård Glacier, and Fenris Glacier were calculated from satellite-derived average surface velocity, glacier width, and estimated ice thickness, and fluctuations in terrestrial surface freshwater runoff were simulated based on observed meteorological data. These simulations were compared and bias corrected against independent glacier catchment runoff observations. Modeled runoff to Sermilik Fjord was variable, ranging from 2.9 ± 0.4×109 m3 y−1 in 1999 to 5.9 ± 0.9×109 m3 y−1 in 2005. The sub-catchment runoff of the Helheim Glacier region accounted for 25% of the total runoff to Sermilik Fjord. The runoff distribution from the different sub-catchments suggested a strong influence from the spatial variation in glacier coverage, indicating high runoff volumes, where glacier cover was present at low elevations.

  16. Multi-year Estimates of Methane Fluxes in Alaska from an Atmospheric Inverse Model

    Science.gov (United States)

    Miller, S. M.; Commane, R.; Chang, R. Y. W.; Miller, C. E.; Michalak, A. M.; Dinardo, S. J.; Dlugokencky, E. J.; Hartery, S.; Karion, A.; Lindaas, J.; Sweeney, C.; Wofsy, S. C.

    2015-12-01

    We estimate methane fluxes across Alaska over a multi-year period using observations from a three-year aircraft campaign, the Carbon Arctic Reservoirs Vulnerability Experiment (CARVE). Existing estimates of methane from Alaska and other Arctic regions disagree in both magnitude and distribution, and before the CARVE campaign, atmospheric observations in the region were sparse. We combine these observations with an atmospheric particle trajectory model and a geostatistical inversion to estimate surface fluxes at the model grid scale. We first use this framework to estimate the spatial distribution of methane fluxes across the state. We find the largest fluxes in the south-east and North Slope regions of Alaska. This distribution is consistent with several estimates of wetland extent but contrasts with the distribution in most existing flux models. These flux models concentrate methane in warmer or more southerly regions of Alaska compared to the estimate presented here. This result suggests a discrepancy in how existing bottom-up models translate wetland area into methane fluxes across the state. We next use the inversion framework to explore inter-annual variability in regional-scale methane fluxes for 2012-2014. We examine the extent to which this variability correlates with weather or other environmental conditions. These results indicate the possible sensitivity of wetland fluxes to near-term variability in climate.

  17. Simulating carbon exchange using a regional atmospheric model coupled to an advanced land-surface model

    Directory of Open Access Journals (Sweden)

    H. W. Ter Maat

    2010-08-01

    Full Text Available This paper is a case study to investigate what the main controlling factors are that determine atmospheric carbon dioxide content for a region in the centre of The Netherlands. We use the Regional Atmospheric Modelling System (RAMS, coupled with a land surface scheme simulating carbon, heat and momentum fluxes (SWAPS-C, and including also submodels for urban and marine fluxes, which in principle should include the dominant mechanisms and should be able to capture the relevant dynamics of the system. To validate the model, observations are used that were taken during an intensive observational campaign in central Netherlands in summer 2002. These include flux-tower observations and aircraft observations of vertical profiles and spatial fluxes of various variables.

    The simulations performed with the coupled regional model (RAMS-SWAPS-C are in good qualitative agreement with the observations. The station validation of the model demonstrates that the incoming shortwave radiation and surface fluxes of water and CO2 are well simulated. The comparison against aircraft data shows that the regional meteorology (i.e. wind, temperature is captured well by the model. Comparing spatially explicitly simulated fluxes with aircraft observed fluxes we conclude that in general latent heat fluxes are underestimated by the model compared to the observations but that the latter exhibit large variability within all flights. Sensitivity experiments demonstrate the relevance of the urban emissions of carbon dioxide for the carbon balance in this particular region. The same tests also show the relation between uncertainties in surface fluxes and those in atmospheric concentrations.

  18. Characteristics of heat flux and particle flux to the divertor in H-mode of JT-60U

    International Nuclear Information System (INIS)

    Itami, K.; Hosogane, N.; Asakura, N.; Kubo, H.; Tsuji, S.; Shimada, M.

    1995-01-01

    Heat flux and particle flux behavior in H-mode is studied in a comparative manner. It was confirmed that the multiple peak structure of heat flux during ELM activity has a role in reducing the average value of a peak heat flux at the divertor. In order to characterize heat and particle flux during ELM activity, the ELM part and the steady state part of heat flux and particle flux were determined and statistically analyzed. A large in-out asymmetry of peak ELM heat flux density was found. The asymmetry is almost unaffected by the ion grad-B drift direction. In-out asymmetry of both ELM and steady-state parts of the particle flux were found to be similar. ((orig.))

  19. The Open Flux Problem

    Science.gov (United States)

    Linker, J. A.; Caplan, R. M.; Downs, C.; Riley, P.; Mikic, Z.; Lionello, R.; Henney, C. J.; Arge, C. N.; Liu, Y.; Derosa, M. L.; Yeates, A.; Owens, M. J.

    2017-10-01

    The heliospheric magnetic field is of pivotal importance in solar and space physics. The field is rooted in the Sun’s photosphere, where it has been observed for many years. Global maps of the solar magnetic field based on full-disk magnetograms are commonly used as boundary conditions for coronal and solar wind models. Two primary observational constraints on the models are (1) the open field regions in the model should approximately correspond to coronal holes (CHs) observed in emission and (2) the magnitude of the open magnetic flux in the model should match that inferred from in situ spacecraft measurements. In this study, we calculate both magnetohydrodynamic and potential field source surface solutions using 14 different magnetic maps produced from five different types of observatory magnetograms, for the time period surrounding 2010 July. We have found that for all of the model/map combinations, models that have CH areas close to observations underestimate the interplanetary magnetic flux, or, conversely, for models to match the interplanetary flux, the modeled open field regions are larger than CHs observed in EUV emission. In an alternative approach, we estimate the open magnetic flux entirely from solar observations by combining automatically detected CHs for Carrington rotation 2098 with observatory synoptic magnetic maps. This approach also underestimates the interplanetary magnetic flux. Our results imply that either typical observatory maps underestimate the Sun’s magnetic flux, or a significant portion of the open magnetic flux is not rooted in regions that are obviously dark in EUV and X-ray emission.

  20. The Open Flux Problem

    Energy Technology Data Exchange (ETDEWEB)

    Linker, J. A.; Caplan, R. M.; Downs, C.; Riley, P.; Mikic, Z.; Lionello, R. [Predictive Science Inc., 9990 Mesa Rim Road, Suite 170, San Diego, CA 92121 (United States); Henney, C. J. [Air Force Research Lab/Space Vehicles Directorate, 3550 Aberdeen Avenue SE, Kirtland AFB, NM (United States); Arge, C. N. [Science and Exploration Directorate, NASA/GSFC, Greenbelt, MD 20771 (United States); Liu, Y. [W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 (United States); Derosa, M. L. [Lockheed Martin Solar and Astrophysics Laboratory, 3251 Hanover Street B/252, Palo Alto, CA 94304 (United States); Yeates, A. [Department of Mathematical Sciences, Durham University, Durham, DH1 3LE (United Kingdom); Owens, M. J., E-mail: linkerj@predsci.com [Space and Atmospheric Electricity Group, Department of Meteorology, University of Reading, Earley Gate, P.O. Box 243, Reading RG6 6BB (United Kingdom)

    2017-10-10

    The heliospheric magnetic field is of pivotal importance in solar and space physics. The field is rooted in the Sun’s photosphere, where it has been observed for many years. Global maps of the solar magnetic field based on full-disk magnetograms are commonly used as boundary conditions for coronal and solar wind models. Two primary observational constraints on the models are (1) the open field regions in the model should approximately correspond to coronal holes (CHs) observed in emission and (2) the magnitude of the open magnetic flux in the model should match that inferred from in situ spacecraft measurements. In this study, we calculate both magnetohydrodynamic and potential field source surface solutions using 14 different magnetic maps produced from five different types of observatory magnetograms, for the time period surrounding 2010 July. We have found that for all of the model/map combinations, models that have CH areas close to observations underestimate the interplanetary magnetic flux, or, conversely, for models to match the interplanetary flux, the modeled open field regions are larger than CHs observed in EUV emission. In an alternative approach, we estimate the open magnetic flux entirely from solar observations by combining automatically detected CHs for Carrington rotation 2098 with observatory synoptic magnetic maps. This approach also underestimates the interplanetary magnetic flux. Our results imply that either typical observatory maps underestimate the Sun’s magnetic flux, or a significant portion of the open magnetic flux is not rooted in regions that are obviously dark in EUV and X-ray emission.

  1. Stepping towards new parameterizations for non-canonical atmospheric surface-layer conditions

    Science.gov (United States)

    Calaf, M.; Margairaz, F.; Pardyjak, E.

    2017-12-01

    Representing land-atmosphere exchange processes as a lower boundary condition remains a challenge. This is partially a result of the fact that land-surface heterogeneity exists at all spatial scales and its variability does not "average" out with decreasing scales. Such variability need not rapidly blend away from the boundary thereby impacting the near-surface region of the atmosphere. Traditionally, momentum and energy fluxes linking the land surface to the flow in NWP models have been parameterized using atmospheric surface layer (ASL) similarity theory. There is ample evidence that such representation is acceptable for stationary and planar-homogeneous flows in the absence of subsidence. However, heterogeneity remains a ubiquitous feature eliciting appreciable deviations when using ASL similarity theory, especially in scalars such moisture and air temperature whose blending is less efficient when compared to momentum. The focus of this project is to quantify the effect of surface thermal heterogeneity with scales Ο(1/10) the height of the atmospheric boundary layer and characterized by uniform roughness. Such near-canonical cases describe inhomogeneous scalar transport in an otherwise planar homogeneous flow when thermal stratification is weak or absent. In this work we present a large-eddy simulation study that characterizes the effect of surface thermal heterogeneities on the atmospheric flow using the concept of dispersive fluxes. Results illustrate a regime in which the flow is mostly driven by the surface thermal heterogeneities, in which the contribution of the dispersive fluxes can account for up to 40% of the total sensible heat flux. Results also illustrate an alternative regime in which the effect of the surface thermal heterogeneities is quickly blended, and the dispersive fluxes provide instead a quantification of the flow spatial heterogeneities produced by coherent turbulent structures result of the surface shear stress. A threshold flow

  2. Bichromatic Scintillometer Measurements of Sensible and Latent Heat Fluxes over a Boreal Forested Valley

    Science.gov (United States)

    Isabelle, P. E.; Nadeau, D.; Parent, A. C.; Rousseau, A. N.; Jutras, S.; Anctil, F.

    2017-12-01

    Boreal forest covers roughly 10% of the earth emerged surface, making it one of the world most common type of landscape. There is a large number of studies on the land-atmosphere exchanges of water and energy for this type of forested surfaces. However, few were located in complex terrain, and, to the best of our knowledge, none have looked at continuous regional scale fluxes. Scintillometry is a powerful tool that allows such measurements, but is usually used over flat homogeneous terrain due to its dependency on Monin-Obukhov Similarity Theory. However, some recent studies have applied this method over slopes, measuring fluxes comparable to those using the eddy covariance method. Still, more experiments are needed using scintillometry over sloped surfaces. This study presents bichromatic scintillometer measurements of sensible and latent heat fluxes over a boreal-forested valley. The field site is located in the Montmorency Forest, Québec, Canada (47°17'N; 71°10'W). The instrumented valley is surrounded by ridges at 900 m elevation, with the bottom stream at 785 m, and follows a 300-120° azimuth coinciding with the two main wind direction (up and down-valley, respectively). Vegetation mostly includes balsam firs 6-10 m tall, creating a rough but homogeneous surface. Scintillometer transmitters and receivers are installed on top of the ridges enclosing the valley, making the path 1.35 km long and its effective height 70-m tall. The setup includes a large aperture and a micro-wave scintillometer with crossing paths allowing the use of the bichromatic method. Measurement are taken continuously from August to October 2017. Scintillometer fluxes are compared with those measured by a 15-m eddy covariance tower located 100 m west of the measurement path, on the southern slope of the valley. Net radiation is also measured to assess energy budget closure over the valley. The setup allows us to test the limits of applicability of scintillometer measurements, especially

  3. Variations in Below Canopy Turbulent Flux From Snow in North American Mountain Environments

    Science.gov (United States)

    Essery, R.; Marks, D.; Pomeroy, J.; Grangere, R.; Reba, M.; Hedstrom, N.; Link, T.; Winstral, A.

    2004-12-01

    Sensible and latent heat and mass fluxes from the snow surface are modulated by site canopy density and structure. Forest and shrub canopies reduce wind speeds and alter the radiation and thermal environment which will alter the below canopy energetics that control the magnitude of turbulent fluxes between the snow surface and the atmosphere. In this study eddy covariance (EC) systems were located in three experimental catchments along a mountain transect through the North American Cordillera. Within each catchment, a variety of sites representing the local range of climate, weather, and canopy conditions were selected for measurement of sensible and latent heat and mass flux from the snow surface. EC measurements were made 1) below a uniform pine canopy (2745m) in the Fraser Experimental Forest in Colorado from February through June melt-out in 2003; 2) at an open, unforested site (2100m), and below an Aspen canopy (2055m) within a small headwater catchment in the Reynolds Creek Experimental Watershed, Owyhee Mts., Idaho from October, 2003, through June melt-out, 2004; and 3) at five sites, representing a range of conditions: a) below a dense spruce forest (750m); b) a north-facing shrub-tundra slope (1383m); c) a south-facing shrub-tundra slope; d) the valley bottom between b) and c) (1363m); and e) a tundra site (1402m) in the Wolf Creek Research Basin (WCRB) in the Yukon, Canada during the 2001 and 2002 snow seasons. Summary data from all sites are presented and compared including the relative significance of sublimation losses at each site, the importance of interception losses to the snowcover mass balance, and the occurrence of condensation events. Site and weather conditions that inhibit or enhance flux from the snow surface are discussed. This research will improve snow modeling by allowing better representation of turbulent fluxes from snow in forested regions, and improved simulation of the snowcover mass balance over low deposition, high latitude sites

  4. Effects of Sea-Surface Waves and Ocean Spray on Air-Sea Momentum Fluxes

    Science.gov (United States)

    Zhang, Ting; Song, Jinbao

    2018-04-01

    The effects of sea-surface waves and ocean spray on the marine atmospheric boundary layer (MABL) at different wind speeds and wave ages were investigated. An MABL model was developed that introduces a wave-induced component and spray force to the total surface stress. The theoretical model solution was determined assuming the eddy viscosity coefficient varied linearly with height above the sea surface. The wave-induced component was evaluated using a directional wave spectrum and growth rate. Spray force was described using interactions between ocean-spray droplets and wind-velocity shear. Wind profiles and sea-surface drag coefficients were calculated for low to high wind speeds for wind-generated sea at different wave ages to examine surface-wave and ocean-spray effects on MABL momentum distribution. The theoretical solutions were compared with model solutions neglecting wave-induced stress and/or spray stress. Surface waves strongly affected near-surface wind profiles and sea-surface drag coefficients at low to moderate wind speeds. Drag coefficients and near-surface wind speeds were lower for young than for old waves. At high wind speeds, ocean-spray droplets produced by wind-tearing breaking-wave crests affected the MABL strongly in comparison with surface waves, implying that wave age affects the MABL only negligibly. Low drag coefficients at high wind caused by ocean-spray production increased turbulent stress in the sea-spray generation layer, accelerating near-sea-surface wind. Comparing the analytical drag coefficient values with laboratory measurements and field observations indicated that surface waves and ocean spray significantly affect the MABL at different wind speeds and wave ages.

  5. Assesment of pesticide fluxes to surface water using Uranine in Colombia

    Science.gov (United States)

    Garcia-Santos, G.; Scheiben, D.; Diaz, J.; Leuenberger, F.; Binder, C. R.

    2009-04-01

    In the highlands of Colombia, potato farmers maximize their yields by the application of pesticides. Properly applied pesticides can significantly reduce yield loss and improve product quality; however their misuse leads to human health and environmental problems, i.e. water bodies contaminated with pesticides. Due to the lack of control regarding local pesticide use, unmeasured hydrological parameters and use of local water runoff as a drinking water supply, an assessment of the impact of agricultural practice on water quality is mandatory as first stage. In order to accomplish this, our study assesses pesticide fluxes to surface water using the tracer Uranine. The experimental area La Hoya main basin (3 km2) contains the Pantano Verde river which flows into the Teatinos river in the Boyaca region (Colombia). Some facts such as the deep soils in the area and the importance of the unsaturated zone for the sorption and degradation of pesticides suggest a lack of contaminants in groundwater. However, due to the humid conditions, steep slopes and an intensive agricultural with high pesticide use, we expect surface water to be highly contaminated. In order to assess pesticide pathways, a tracer (Uranine), detectable at very low amount was used. Four local farmers applied the tracer instead of the pesticide mixture covering a total surface of 1.2 10-2 km2. Meteorological data were measured every 15 min with one compact meteorological station installed within the basin and water flow and water sampling were obtained using an ISCO-6700 water sampler, during one week every 10 min in the outlet of Pantano Verde River. In addition, three pairs of membranes were installed down the river and collected 1 week, one month and 4 months after the experiment to measure tracer accumulation. The tracer in water was analysed using a fluorescent spectrometer. Results of this study show first variations of tracer concentration in water in La Hoya basin and constitute an initial steep in

  6. Comparative study on current limiting characteristics of flux-lock type SFCL with series or parallel connection of two coils

    International Nuclear Information System (INIS)

    Lim, S.H.

    2008-01-01

    We investigated the current limiting characteristics of the flux-lock type superconducting fault current limiter (SFCL) with series or parallel connection of two coils. These two flux-lock type SFCLs with magnetically coupled two coils have the same operational principle that the fault current can be limited by the magnetic flux generated between two coils of the SFCL when a fault happens. In addition, the inductance ratio and the winding direction of two coils in both the SFCLs are the major design parameters that affect the fault current limiting characteristics of the SFCL. On the other hand, the operational current and the limiting impedance of both the SFCLs under the same design condition have the different tendency, which results from the different winding methods of two coils on an iron core. Therefore, the comparative study for both the SFCLs from the current limiting performance of the SFCL point of view is needed. To compare the current limiting characteristics of both the SFCLs, the operational current and the limiting impedance of the SFCL, which describes the performance of the SFCL, were derived from each SFCL's electrical equivalent circuit. Through the analysis for the fault current limiting experiments of both the SFCLs, the different current limiting characteristics of both the SFCLs were discussed

  7. Evaluation of Deep Learning Models for Predicting CO2 Flux

    Science.gov (United States)

    Halem, M.; Nguyen, P.; Frankel, D.

    2017-12-01

    Artificial neural networks have been employed to calculate surface flux measurements from station data because they are able to fit highly nonlinear relations between input and output variables without knowing the detail relationships between the variables. However, the accuracy in performing neural net estimates of CO2 flux from observations of CO2 and other atmospheric variables is influenced by the architecture of the neural model, the availability, and complexity of interactions between physical variables such as wind, temperature, and indirect variables like latent heat, and sensible heat, etc. We evaluate two deep learning models, feed forward and recurrent neural network models to learn how they each respond to the physical measurements, time dependency of the measurements of CO2 concentration, humidity, pressure, temperature, wind speed etc. for predicting the CO2 flux. In this paper, we focus on a) building neural network models for estimating CO2 flux based on DOE data from tower Atmospheric Radiation Measurement data; b) evaluating the impact of choosing the surface variables and model hyper-parameters on the accuracy and predictions of surface flux; c) assessing the applicability of the neural network models on estimate CO2 flux by using OCO-2 satellite data; d) studying the efficiency of using GPU-acceleration for neural network performance using IBM Power AI deep learning software and packages on IBM Minsky system.

  8. The Validation of the GEWEX SRB Surface Shortwave Flux Data Products Using BSRN Measurements: A Systematic Quality Control, Production and Application Approach

    Science.gov (United States)

    Zhang, Taiping; Stackhouse, Paul W., Jr.; Gupta, Shashi K.; Cox, Stephen J.; Mikovitz, J. Colleen; Hinkelman, Laura M.

    2013-01-01

    The NASA/GEWEX Surface Radiation Budget (SRB) project has produced a 24.5-year continuous record of global shortwave and longwave radiation fluxes at TOA and the Earth's surface from satellite measurements. The time span of the data is from July 1983 to December 2007, and the spatial resolution is 11 latitude11 longitude. The inputs of the latest version (Release 3.0) include the GEOS Version 4.0.3 meteorological information and cloud properties derived from ISCCP DX data. The SRB products are available on 3-hourly, 3-hourly-monthly, daily and monthly time scales. To assess the quality of the product, we extensively validated the SRB data against 5969 site-months of groundbased measurements from 52 Baseline Surface Radiation Network (BSRN) stations. This paper describes first the characteristics of the BSRN data and the GEWEX SRB data, the methodology for quality control and processing of the shortwave BSRN data, and then the systematic SRB-BSRN comparisons. It is found that, except for occasional extreme outliers as seen in scatter plots, the satellite-based surface radiation data generally agree very well with BSRN measurements. Specifically, the bias/RMS for the daily and monthly mean shortwave fluxes are, respectively, -3.6/35.5 and -5.2/23.3W1 m2 under all-sky conditions.

  9. Integrating satellite retrieved leaf chlorophyll into land surface models for constraining simulations of water and carbon fluxes

    KAUST Repository

    Houborg, Rasmus

    2013-07-01

    In terrestrial biosphere models, key biochemical controls on carbon uptake by vegetation canopies are typically assigned fixed literature-based values for broad categories of vegetation types although in reality significant spatial and temporal variability exists. Satellite remote sensing can support modeling efforts by offering distributed information on important land surface characteristics, which would be very difficult to obtain otherwise. This study investigates the utility of satellite based retrievals of leaf chlorophyll for estimating leaf photosynthetic capacity and for constraining model simulations of water and carbon fluxes. © 2013 IEEE.

  10. 2D surface temperature measurement of plasma facing components with modulated active pyrometry

    International Nuclear Information System (INIS)

    Amiel, S.; Loarer, T.; Pocheau, C.; Roche, H.; Gauthier, E.; Aumeunier, M.-H.; Courtois, X.; Jouve, M.; Balorin, C.; Moncada, V.; Le Niliot, C.; Rigollet, F.

    2014-01-01

    In nuclear fusion devices, such as Tore Supra, the plasma facing components (PFC) are in carbon. Such components are exposed to very high heat flux and the surface temperature measurement is mandatory for the safety of the device and also for efficient plasma scenario development. Besides this measurement is essential to evaluate these heat fluxes for a better knowledge of the physics of plasma-wall interaction, it is also required to monitor the fatigue of PFCs. Infrared system (IR) is used to manage to measure surface temperature in real time. For carbon PFCs, the emissivity is high and known (ε ∼ 0.8), therefore the contribution of the reflected flux from environment and collected by the IR cameras can be neglected. However, the future tokamaks such as WEST and ITER will be equipped with PFCs in metal (W and Be/W, respectively) with low and variable emissivities (ε ∼ 0.1–0.4). Consequently, the reflected flux will contribute significantly in the collected flux by IR camera. The modulated active pyrometry, using a bicolor camera, proposed in this paper allows a 2D surface temperature measurement independently of the reflected fluxes and the emissivity. Experimental results with Tungsten sample are reported and compared with simultaneous measurement performed with classical pyrometry (monochromatic and bichromatic) with and without reflective flux demonstrating the efficiency of this method for surface temperature measurement independently of the reflected flux and the emissivity

  11. A one-layer satellite surface energy balance for estimating evapotranspiration rates and crop water stress indexes.

    Science.gov (United States)

    Barbagallo, Salvatore; Consoli, Simona; Russo, Alfonso

    2009-01-01

    Daily evapotranspiration fluxes over the semi-arid Catania Plain area (Eastern Sicily, Italy) were evaluated using remotely sensed data from Landsat Thematic Mapper TM5 images. A one-source parameterization of the surface sensible heat flux exchange using satellite surface temperature has been used. The transfer of sensible and latent heat is described by aerodynamic resistance and surface resistance. Required model inputs are brightness, temperature, fractional vegetation cover or leaf area index, albedo, crop height, roughness lengths, net radiation, air temperature, air humidity and wind speed. The aerodynamic resistance (r(ah)) is formulated on the basis of the Monin-Obukhov surface layer similarity theory and the surface resistance (r(s)) is evaluated from the energy balance equation. The instantaneous surface flux values were converted into evaporative fraction (EF) over the heterogeneous land surface to derive daily evapotranspiration values. Remote sensing-based assessments of crop water stress (CWSI) were also made in order to identify local irrigation requirements. Evapotranspiration data and crop coefficient values obtained from the approach were compared with: (i) data from the semi-empirical approach "K(c) reflectance-based", which integrates satellite data in the visible and NIR regions of the electromagnetic spectrum with ground-based measurements and (ii) surface energy flux measurements collected from a micrometeorological tower located in the experiment area. The expected variability associated with ET flux measurements suggests that the approach-derived surface fluxes were in acceptable agreement with the observations.

  12. An inter-comparison of six latent and sensible heat flux products over the Southern Ocean

    Directory of Open Access Journals (Sweden)

    Lejiang Yu

    2011-11-01

    Full Text Available The latent heat fluxes (LHF and sensible heat fluxes (SHF over the Southern Ocean from six different data sets are inter-compared for the period 1988–2000. The six data sets include three satellite-based products, namely, the second version of the Goddard Satellite-Based Surface Turbulent Fluxes data set (GSSTF-2, the third version of the Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Data (HOAPS-3 and the Japanese Ocean Fluxes Data Sets with Use of Remote Sensing Observations (J-OFURO; two global reanalysis products, namely, the National Centers for Environmental Prediction–Department of Energy Reanalysis 2 data set (NCEP-2 and the European Centre for Medium-Range Weather Forecasts 40 Year Re-analysis data set (ERA-40; and the Objectively Analyzed Air–Sea Fluxes for the Global Oceans data set (OAFlux. All these products reveal a similar pattern in the averaged flux fields. The zonal mean LHF fields all exhibit a continuous increase equatorward. With an exception of HOAPS-3, the zonal mean SHF fields display a minimum value near 50°S, increasing both pole- and equatorward. The differences in the standard deviation for LHF are larger among the six data products than the differences for SHF. Over the regions where the surface fluxes are significantly influenced by the Antarctic Oscillation and the Pacific–South American teleconnection, the values and distributions of both LHF and SHF are consistent among the six products. It was found that the spatial patterns of the standard deviations and trends of LHF and SHF can be explained primarily by sea–air specific humidity and temperature differences; wind speed plays a minor role.

  13. Pulsed magnetic flux leakage method for hairline crack detection and characterization

    Science.gov (United States)

    Okolo, Chukwunonso K.; Meydan, Turgut

    2018-04-01

    The Magnetic Flux leakage (MFL) method is a well-established branch of electromagnetic Non-Destructive Testing (NDT), extensively used for evaluating defects both on the surface and far-surface of pipeline structures. However the conventional techniques are not capable of estimating their approximate size, location and orientation, hence an additional transducer is required to provide the extra information needed. This research is aimed at solving the inevitable problem of granular bond separation which occurs during manufacturing, leaving pipeline structures with miniature cracks. It reports on a quantitative approach based on the Pulsed Magnetic Flux Leakage (PMFL) method, for the detection and characterization of the signals produced by tangentially oriented rectangular surface and far-surface hairline cracks. This was achieved through visualization and 3D imaging of the leakage field. The investigation compared finite element numerical simulation with experimental data. Experiments were carried out using a 10mm thick low carbon steel plate containing artificial hairline cracks with various depth sizes, and different features were extracted from the transient signal. The influence of sensor lift-off and pulse width variation on the magnetic field distribution which affects the detection capability of various hairline cracks located at different depths in the specimen is explored. The findings show that the proposed technique can be used to classify both surface and far-surface hairline cracks and can form the basis for an enhanced hairline crack detection and characterization for pipeline health monitoring.

  14. Impacts of spectral nudging on the simulated surface air temperature in summer compared with the selection of shortwave radiation and land surface model physics parameterization in a high-resolution regional atmospheric model

    Science.gov (United States)

    Park, Jun; Hwang, Seung-On

    2017-11-01

    The impact of a spectral nudging technique for the dynamical downscaling of the summer surface air temperature in a high-resolution regional atmospheric model is assessed. The performance of this technique is measured by comparing 16 analysis-driven simulation sets of physical parameterization combinations of two shortwave radiation and four land surface model schemes of the model, which are known to be crucial for the simulation of the surface air temperature. It is found that the application of spectral nudging to the outermost domain has a greater impact on the regional climate than any combination of shortwave radiation and land surface model physics schemes. The optimal choice of two model physics parameterizations is helpful for obtaining more realistic spatiotemporal distributions of land surface variables such as the surface air temperature, precipitation, and surface fluxes. However, employing spectral nudging adds more value to the results; the improvement is greater than using sophisticated shortwave radiation and land surface model physical parameterizations. This result indicates that spectral nudging applied to the outermost domain provides a more accurate lateral boundary condition to the innermost domain when forced by analysis data by securing the consistency with large-scale forcing over a regional domain. This consequently indirectly helps two physical parameterizations to produce small-scale features closer to the observed values, leading to a better representation of the surface air temperature in a high-resolution downscaled climate.

  15. Downscaling of surface moisture flux and precipitation in the Ebro Valley (Spain using analogues and analogues followed by random forests and multiple linear regression

    Directory of Open Access Journals (Sweden)

    G. Ibarra-Berastegi

    2011-06-01

    Full Text Available In this paper, reanalysis fields from the ECMWF have been statistically downscaled to predict from large-scale atmospheric fields, surface moisture flux and daily precipitation at two observatories (Zaragoza and Tortosa, Ebro Valley, Spain during the 1961–2001 period. Three types of downscaling models have been built: (i analogues, (ii analogues followed by random forests and (iii analogues followed by multiple linear regression. The inputs consist of data (predictor fields taken from the ERA-40 reanalysis. The predicted fields are precipitation and surface moisture flux as measured at the two observatories. With the aim to reduce the dimensionality of the problem, the ERA-40 fields have been decomposed using empirical orthogonal functions. Available daily data has been divided into two parts: a training period used to find a group of about 300 analogues to build the downscaling model (1961–1996 and a test period (1997–2001, where models' performance has been assessed using independent data. In the case of surface moisture flux, the models based on analogues followed by random forests do not clearly outperform those built on analogues plus multiple linear regression, while simple averages calculated from the nearest analogues found in the training period, yielded only slightly worse results. In the case of precipitation, the three types of model performed equally. These results suggest that most of the models' downscaling capabilities can be attributed to the analogues-calculation stage.

  16. Heat flux estimation in an infrared experimental furnace using an inverse method

    International Nuclear Information System (INIS)

    Le Bideau, P.; Ploteau, J.P.; Glouannec, P.

    2009-01-01

    Infrared emitters are widely used in industrial furnaces for thermal treatment. In these processes, the knowledge of the incident heat flux on the surface of the product is a primary step to optimise the command emitters and for maintenance shift. For these reasons, it is necessary to develop autonomous flux meters that could provide an answer to these requirements. These sensors must give an in-line distribution of infrared irradiation in the tunnel furnace and must be able to measure high heat flux in severe thermal environments. In this paper we present a method for in-line assessments solving an inverse heat conduction problem. A metallic mass is instrumented by thermocouples and an inverse method allows the incident heat flux to be estimated. In the first part, attention is focused on a new design tool, which is a numerical code, for the evaluation of potential options during captor conception. In the second part we present the realization and the test of this 'indirect' flux meter and its associated inverse problem. 'Direct' detectors based on thermoelectric devices are compared with this new flux meter in the same conditions in the same furnace. Results prove that this technique is a reliable method, appropriate for high temperature ambiances. This technique can be applied to furnaces where the heat flux is inaccessible to 'direct' measurements.

  17. Temperature distribution and heat radiation of patterned surfaces at short wavelengths

    Science.gov (United States)

    Emig, Thorsten

    2017-05-01

    We analyze the equilibrium spatial distribution of surface temperatures of patterned surfaces. The surface is exposed to a constant external heat flux and has a fixed internal temperature that is coupled to the outside heat fluxes by finite heat conductivity across the surface. It is assumed that the temperatures are sufficiently high so that the thermal wavelength (a few microns at room temperature) is short compared to all geometric length scales of the surface patterns. Hence the radiosity method can be employed. A recursive multiple scattering method is developed that enables rapid convergence to equilibrium temperatures. While the temperature distributions show distinct dependence on the detailed surface shapes (cuboids and cylinder are studied), we demonstrate robust universal relations between the mean and the standard deviation of the temperature distributions and quantities that characterize overall geometric features of the surface shape.

  18. Enhanced pool boiling critical heat flux induced by capillary wicking effect of a Cr-sputtered superhydrophilic surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Son, Hong Hyun; Seo, Gwang Hyeok; Kim, Sung Joong [Hanyang University, Seoul (Korea, Republic of)

    2016-10-15

    In light of boiling heat transfer, the smooth surface potentially reduces active nucleation of bubbles and rewetting of dry spots near the critical heat flux (CHF). This kind of process is highly likely to deteriorate the CHF. Thus, it is essential to produce appropriate microstructures on the surface for the enhancement of the CHF. In this study, to investigate the microstructural effect of thin film-fabricated surfaces on the pool boiling CHF, we controlled the surface roughness in a narrow range of 0.1-0.25 μm and its morphologies, in the form of micro-scratches using PVD sputtering technique. Specifically for DC magnetron sputtering, pure chromium (Cr) was selected as a target material owing to its high oxidation resistance. In order to analyze the CHF trend with changes in roughness, we introduced existing capillary wicking-based models because superhydrophilic characteristics of microstructures are highly related to the capillary wicking behaviors in micro-flow channels. After Cr sputtering under given conditions, the Cr-sputtered surfaces showed superhydrophilic characteristics and its capability became more enhanced with an increase of surface roughness. Judging from spreading behavior of a liquid droplet, the presence of micro-wicking channels, coupled with Cr nanostructures, effectively enhanced the advancing rate of drop base diameter. The CHF exhibited an increasing trend with increasing surface roughness. However, the enhancement ratio agreed poorly with the predictions of the roughness factor-based models, all of which originated from a conventional static force balance.

  19. Flux estimation algorithms for electric drives: a comparative study

    OpenAIRE

    Koteich , Mohamad

    2016-01-01

    International audience; This paper reviews the stator flux estimation algorithms applied to the alternating current motor drives. The so-called voltage model estimation, which consists of integrating the back-electromotive force signal, is addressed. However, in practice , the pure integration is prone to drift problems due to noises, measurement error, stator resistance uncertainty and unknown initial conditions. This limitation becomes more restrictive at low speed operation. Several soluti...

  20. An explanation for the different climate sensitivities of land and ocean surfaces based on the diurnal cycle

    Directory of Open Access Journals (Sweden)

    A. Kleidon

    2017-09-01

    Full Text Available Observations and climate model simulations consistently show a higher climate sensitivity of land surfaces compared to ocean surfaces. Here we show that this difference in temperature sensitivity can be explained by the different means by which the diurnal variation in solar radiation is buffered. While ocean surfaces buffer the diurnal variations by heat storage changes below the surface, land surfaces buffer it mostly by heat storage changes above the surface in the lower atmosphere that are reflected in the diurnal growth of a convective boundary layer. Storage changes below the surface allow the ocean surface–atmosphere system to maintain turbulent fluxes over day and night, while the land surface–atmosphere system maintains turbulent fluxes only during the daytime hours, when the surface is heated by absorption of solar radiation. This shorter duration of turbulent fluxes on land results in a greater sensitivity of the land surface–atmosphere system to changes in the greenhouse forcing because nighttime temperatures are shaped by radiative exchange only, which are more sensitive to changes in greenhouse forcing. We use a simple, analytic energy balance model of the surface–atmosphere system in which turbulent fluxes are constrained by the maximum power limit to estimate the effects of these different means to buffer the diurnal cycle on the resulting temperature sensitivities. The model predicts that land surfaces have a 50 % greater climate sensitivity than ocean surfaces, and that the nighttime temperatures on land increase about twice as much as daytime temperatures because of the absence of turbulent fluxes at night. Both predictions compare very well with observations and CMIP5 climate model simulations. Hence, the greater climate sensitivity of land surfaces can be explained by its buffering of diurnal variations in solar radiation in the lower atmosphere.