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.

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

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)

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

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.

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

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.

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.

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

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.

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.

Fourier transform profilometry (FTP) using an innovative band-pass filter for accurate 3-D surface reconstruction

Science.gov (United States)

Chen, Liang-Chia; Ho, Hsuan-Wei; Nguyen, Xuan-Loc

2010-02-01

This article presents a novel band-pass filter for Fourier transform profilometry (FTP) for accurate 3-D surface reconstruction. FTP can be employed to obtain 3-D surface profiles by one-shot images to achieve high-speed measurement. However, its measurement accuracy has been significantly influenced by the spectrum filtering process required to extract the phase information representing various surface heights. Using the commonly applied 2-D Hanning filter, the measurement errors could be up to 5-10% of the overall measuring height and it is unacceptable to various industrial application. To resolve this issue, the article proposes an elliptical band-pass filter for extracting the spectral region possessing essential phase information for reconstructing accurate 3-D surface profiles. The elliptical band-pass filter was developed and optimized to reconstruct 3-D surface models with improved measurement accuracy. Some experimental results verify that the accuracy can be effectively enhanced by using the elliptical filter. The accuracy improvement of 44.1% and 30.4% can be achieved in 3-D and sphericity measurement, respectively, when the elliptical filter replaces the traditional filter as the band-pass filtering method. Employing the developed method, the maximum measured error can be kept within 3.3% of the overall measuring range.

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

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

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

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

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...

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

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

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.

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.

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.

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.

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

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.

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

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.

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.

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

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.

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

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

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

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.

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 ...

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.

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.

Increase in compton scattering of gamma rays passing along metal surface

International Nuclear Information System (INIS)

Grigor'ev, A.N.; Bilyk, Z.V.; Sakun, A.V.; Marushchenko, V.V.; Chernyavskij, O.Yu.; Litvinov, Yu.V.

2014-01-01

The paper considers experimental study of changes in energy of 137 Cs gamma source as gamma rays pass along metal surface. Decrease in gamma energy was examined by reducing the number of gamma rays in the complete absorption peak to the Compton length level and increasing the Compton effect. The number of gamma rays in the complete absorption peak decreases by 3.5 times in the angle range under study

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.

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

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

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...

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).

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...

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 ...

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.

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.

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

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

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

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...

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

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

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

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

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

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.

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.)

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.

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

Surface effects in the energy loss of ions passing through a thin foil

International Nuclear Information System (INIS)

Osma, J.; Garcia de Abajo, F.J.

1997-01-01

The role of surface plasmon excitation in the interaction of ions passing through thin films has been studied in both the Bloch hydrodynamic approximation and the local response approach for projectile velocities above the maximum of the stopping power curve. The effect of the surface is found to be much weaker when the dispersion of the modes is taken into consideration than in the case of nondispersive media, though qualitatively the main features of the hydrodynamic approach resemble those of the local one. A generalization of the Bothe-Landau convolution formula for the loss probability distribution is derived to take into account the scattering due to the surface. The effects of the surface in the energy-loss spectra are discussed. A comparison with experiment is given. copyright 1997 The American Physical Society

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.

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

An outlook on comparison of hybrid welds of different root pass and ...

Indian Academy of Sciences (India)

Pritesh Prajapati

2018-05-11

May 11, 2018 ... pass and filler pass of flux cored arc welding and gas metal arc welding were acquired. The comparative ... [2], GMAW-plasma welding [3], laser welding-gas tung- sten arc welding ..... by optical emission spectroscopy. Plasma ...

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,...

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

The Physical Therapy and Society Summit (PASS) Meeting: observations and opportunities.

Science.gov (United States)

Kigin, Colleen M; Rodgers, Mary M; Wolf, Steven L

2010-11-01

The construct of delivering high-quality and cost-effective health care is in flux, and the profession must strategically plan how to meet the needs of society. In 2006, the House of Delegates of the American Physical Therapy Association passed a motion to convene a summit on "how physical therapists can meet current, evolving, and future societal health care needs." The Physical Therapy and Society Summit (PASS) meeting on February 27-28, 2009, in Leesburg, Virginia, sent a clear message that for physical therapists to be effective and thrive in the health care environment of the future, a paradigm shift is required. During the PASS meeting, participants reframed our traditional focus on the physical therapist and the patient/client (consumer) to one in which physical therapists are an integral part of a collaborative, multidisciplinary health care team with the health care consumer as its focus. The PASS Steering Committee recognized that some of the opportunities that surfaced during the PASS meeting may be disruptive or may not be within the profession's present strategic or tactical plans. Thus, adopting a framework that helps to establish the need for change that is provocative and potentially disruptive to our present care delivery, yet prioritizes opportunities, is a critical and essential step. Each of us in the physical therapy profession must take on post-PASS roles and responsibilities to accomplish the systemic change that is so intimately intertwined with our destiny. This article offers a perspective of the dynamic dialogue and suggestions that emerged from the PASS event, providing further opportunities for discussion and action within our profession.

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

INVESTIGATION OF SINGLE-PASS/DOUBLE-PASS TECHNIQUES ON FRICTION STIR WELDING OF ALUMINIUM

Directory of Open Access Journals (Sweden)

N.A.A. Sathari

2014-12-01

Full Text Available The aim of this research is to study the effects of single-pass/ double-pass techniques on friction stir welding of aluminium. Two pieces of AA1100 with a thickness of 6.0 mm were friction stir welded using a CNC milling machine at rotational speeds of 1400 rpm, 1600 rpm and 1800 rpm respectively for single-pass and double-pass. Microstructure observations of the welded area were studied using an optical microscope. The specimens were tested by using a tensile test and Vickers hardness test to evaluate their mechanical properties. The results indicated that, at low rotational speed, defects such as ‘surface lack of fill’ and tunnels in the welded area contributed to a decrease in mechanical properties. Welded specimens using double-pass techniques show increasing values of tensile strength and hardness. From this investigation it is found that the best parameters of FSW welded aluminium AA1100 plate were those using double-pass techniques that produce mechanically sound joints with a hardness of 56.38 HV and 108 MPa strength at 1800 rpm compared to the single-pass technique. Friction stir welding, single-pass/ double-pass techniques, AA1100, microstructure, mechanical properties.

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.

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.

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

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

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

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

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.

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

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.

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.

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.

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.

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.

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.

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

Influence of Surface-profile and Movement-path of Roller on Thickness Thinning during Multi-pass Deep Drawing Spinning

Directory of Open Access Journals (Sweden)

Xia Qinxiang

2016-01-01

Full Text Available Over thinning is a serious defect influencing the forming quality of spun workpiece during multi-pass deep drawing spinning. Surface-profile and movement-path of roller are the key factors influencing the thinning ratio of wall thickness of spun workpiece. The influence of surface-profile and movement-path of roller on thickness thinning were studied based on numerical simulation and experimental research, four groups of forming experiments were carried out under the combination of the different surface-profile of roller (R12 and R25-12 and movement-path of roller (spinning from the bottom of the blank and spinning from the middle of the blank. The results show that both the surface-profile and movement-path of roller have great influence on wall thickness thinning during multi-pass deep drawing spinning; and compared with the movement-path of roller, the influence of surface-profile of roller is more significant. The experimental results conform well to the simulation ones. It indicates that the FEA model established is reasonable and reliable.

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)

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.

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.

Linear magnetic motor/generator. [to generate electric energy using magnetic flux for spacecraft power supply

Science.gov (United States)

Studer, P. A. (Inventor)

1982-01-01

A linear magnetic motor/generator is disclosed which uses magnetic flux to provide mechanical motion or electrical energy. The linear magnetic motor/generator includes an axially movable actuator mechanism. A permament magnet mechanism defines a first magnetic flux path which passes through a first end portion of the actuator mechanism. Another permament magnet mechanism defines a second magnetic flux path which passes through a second end portion of the actuator mechanism. A drive coil defines a third magnetic flux path passing through a third central portion of the actuator mechanism. A drive coil selectively adds magnetic flux to and subtracts magnetic flux from magnetic flux flowing in the first and second magnetic flux path.

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.

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.

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.

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.

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

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)

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...

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.

Continuous Surface Rendering, Passing from CAD to Physical Representation

Directory of Open Access Journals (Sweden)

Mario Covarrubias

2013-06-01

Full Text Available This paper describes a desktop-mechatronic interface that has been conceived to support designers in the evaluation of aesthetic virtual shapes. This device allows a continuous and smooth free hand contact interaction on a real and developable plastic tape actuated by a servo-controlled mechanism. The objective in designing this device is to reproduce a virtual surface with a consistent physical rendering well adapted to designers' needs. The desktop-mechatronic interface consists in a servo-actuated plastic strip that has been devised and implemented using seven interpolation points. In fact, by using the MEC (Minimal Energy Curve Spline approach, a developable real surface is rendered taking into account the CAD geometry of the virtual shapes. In this paper, we describe the working principles of the interface by using both absolute and relative approaches to control the position on each single control point on the MEC spline. Then, we describe the methodology that has been implemented, passing from the CAD geometry, linked to VisualNastran in order to maintain the parametric properties of the virtual shape. Then, we present the co-simulation between VisualNastran and MATLAB/Simulink used for achieving this goal and controlling the system and finally, we present the results of the subsequent testing session specifically carried out to evaluate the accuracy and the effectiveness of the mechatronic device.

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.

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

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

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.

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

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

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

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

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 ...

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...

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...

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.

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.

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.

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.)

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.

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.

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.)

Force sensor using changes in magnetic flux

Science.gov (United States)

Pickens, Herman L. (Inventor); Richard, James A. (Inventor)

2012-01-01

A force sensor includes a magnetostrictive material and a magnetic field generator positioned in proximity thereto. A magnetic field is induced in and surrounding the magnetostrictive material such that lines of magnetic flux pass through the magnetostrictive material. A sensor positioned in the vicinity of the magnetostrictive material measures changes in one of flux angle and flux density when the magnetostrictive material experiences an applied force that is aligned with the lines of magnetic flux.

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...

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.

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.

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.

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

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

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.

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

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

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...

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.

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.

Experimentally guided Monte Carlo calculations of the atmospheric muon flux for interdisciplinary applications

International Nuclear Information System (INIS)

Mitrica, B.; Brancus, I.M.; Toma, G.; Bercuci, A.; Aiftimiei, C.; Wentz, J.; Rebel, H.

2004-01-01

Atmospheric muons are produced in the interactions of primary cosmic rays particle with Earth's atmosphere, mainly by the decay of pions and kaons generated in hadronic interactions. They decay further in electrons and positrons and electron and muon neutrinos. Being the penetrating cosmic rays component, the muons manage to pass entirely through the atmosphere and can pass even larger absorbers before they interact with the material at the Earth's surface, and due to cosmogenic production of isotopes by atmospheric muons, information of astrophysical, environmental and material research interest can be obtained. Up to now, mainly semi-analytical approximations have been used to calculate the muon flux for estimating the cosmogenic isotope production, necessary for different applications. Our estimation of the atmospheric muon flux is based on a Monte-Carlo simulation program CORSIKA, in which we simulate the development in the atmosphere of the extensive air showers, using different models for the description of the hadronic interaction. Atmospheric muons are produced in the interactions of primary cosmic rays particle with Earth's atmosphere, mainly by the decay of pions and kaons generated in hadronic interactions. They decay further in electrons and positrons and electron and muon neutrinos. Being the penetrating cosmic rays component, the muons manage to pass entirely through the atmosphere and can pass even larger absorbers before they interact with the material at the Earth's surface, and due to cosmogenic production of isotopes by atmospheric muons, information of astrophysical, environmental and material research interest can be obtained. Up to now, mainly semi-analytical approximations have been used to calculate the muon flux for estimating the cosmogenic isotope production, necessary for different applications. Our estimation of the atmospheric muon flux is based on a Monte-Carlo simulation program CORSIKA, in which we simulates the development in the

Poynting flux measurements on a satellite: A diagnostic tool for space research

International Nuclear Information System (INIS)

Kelley, M.C.; Knudsen, D.J.; Vickery, J.F.

1991-01-01

The first satellite observations of the total field-aligned component of the quasi-dc Poynting flux are presented for two passes over the polar region, one in the noon sector and one in the afternoon. The energy input due to electron precipitation is also presented. In the noon pass the downward Poynting flux in the auroral oval was comparable to the kinetic energy input rate. The peak electromagnetic energy input rate of 6 ergs/(cm 2 s) equaled the peak particle input while the integrated electromagnetic value along the trajectory was 60% that of the particles. In the afternoon pass the peak electromagnetic energy input was also about 6 ergs/(cm 2 s), but the peak particle energy was 6 times this value. The average electromagnetic input was 10% of the particle input for the pass. In this study, the authors can measure the Poynting flux only over a limited range of scale sizes; thus the contribution to the total energy budget in the polar cap cannot be determined. Both passes show small regions characterized by upward Poynting flux suggesting a neutral wind dynamo. There is also evidence during part of the noontime pass that the external generator acted in opposition to an existing wind field since the Poynting flux was greater than the estimate of Joule heating from the electric field measurement alone (i.e., from Σ p E 2 ). In the course of deriving Poynting's theorem for the geophysical case they also present a proof that ground magnetometer systems respond primarily to the Hall current which does not depend upon geometric cancellation between the field generated by Pedersen and field-aligned currents

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).

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 ...

Explosive emission as a process involving a plasma flux

International Nuclear Information System (INIS)

Smirnov, B.M.

1995-01-01

Investigating the character of an intense emission in electric discharges, G.A. Mesyats has discovered in 1966 the phenomenon of explosive emission. This Phenomenon consists in heating of some cathode region under the influence of discharge currents. As a result, a plasm of a high conductivity is formed near the cathode, and the discharge current passes through this plasm during its existence. This phenomenon is studied in detail from different standpoints. Below we consider one more aspect of this phenomenon by using its analogy with a plasm which results fran irradiation of a surface. Estimates for a copper cathode will be made. A schematic character of the phenomenon under consideration is as follows. An electric field near a cathode creates an electric current. which is concentrated bi a small region of the cathode and heat it. Evaporating atoms with admixture of electrons and ions form a flux which is transformed to a fully ionized plasma under the influence of external fields. This plasm has a high conductivity and provides passing of electric currents of a high intensity. Note that for simplicity we omit different peculiarities of this phenomenon because here a plasma flux is of interest as a conductive matter

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.

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.

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.

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...

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

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)

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...

The transport characteristics of passing fast ions produced by nonlocal overlapping of drift island surfaces and magnetic island surfaces

Energy Technology Data Exchange (ETDEWEB)

Cao, Jinjia; Gong, Xueyu, E-mail: gongxueyu-usc@163.com; Xiang, Dong; Huang, Qianhong [School of Nuclear Science and Technology, University of South China, Hengyang 421001 (China); Yu, Jun [School of Mathematics and Physics, University of South China, Hengyang 421001 (China)

2016-08-15

The structure of the drift-island surface of passing fast ions (PFIs) is investigated in the presence of the resonant interaction with a magnetic island. Two overlapping regions of the drift-island surface and the magnetic island surface are found, one corresponding to local overlapping region and the other to non-local one. Here, the word “nonlocal” denotes that the resonances in the core plasma can have effects on the PFIs near the plasma boundary, while the “local” represents that the PFIs just near the resonant location are influenced. The nonlocal overlapping constructs a transport path along which the PFIs can become losses. There are three kinds of drift-island surfaces to join in forming the transport paths. A pitch angle region, which is called pitch angle gap, is found near the plasma boundary, where the drift-island surface cannot be formed and few PFIs are lost. The pitch-angle selective features of PFI losses are obtained by analyzing the three kinds of drift-island surfaces. The coupling between the crowd drift island surfaces and the collision can induce the prompt losses of PFIs and rapidly slowing down of PFI energy. The time of the prompt losses and the slowing down rate are calculated. Qualitatively, the theoretical results are in well agreement with the experimental observations in ASDEX Upgrade [M. García-Muñoz et al., Nucl. Fusion 47, L10 (2007)].

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

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

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.

A systematic study of ball passing frequencies based on dynamic modeling of rolling ball bearings with localized surface defects

Science.gov (United States)

Niu, Linkai; Cao, Hongrui; He, Zhengjia; Li, Yamin

2015-11-01

Ball passing frequencies (BPFs) are very important features for condition monitoring and fault diagnosis of rolling ball bearings. The ball passing frequency on outer raceway (BPFO) and the ball passing frequency on inner raceway (BPFI) are usually calculated by two well-known kinematics equations. In this paper, a systematic study of BPFs of rolling ball bearings is carried out. A novel method for accurately calculating BPFs based on a complete dynamic model of rolling ball bearings with localized surface defects is proposed. In the used dynamic model, three-dimensional motions, relative slippage, cage effects and localized surface defects are all considered. Moreover, localized surface defects are modeled accurately with consideration of the finite size of the ball, the additional clearance due to material absence, and changes of contact force directions. The reasonability of the proposed method for the prediction of dynamic behaviors of actual ball bearings with localized surface defects and for the calculation of BPFs is discussed by investigating the motion characteristics of a ball when it rolls through a defect. Parametric investigation shows that the shaft speed, external loads, the friction coefficient, raceway groove curvature factors, the initial contact angle, and defect sizes have great effects on BPFs. For a loaded ball bearing, the combination of rolling and sliding in contact region occurs, and the BPFs calculated by simple kinematical relationships are inaccurate, especially for high speed, low external load, and large initial contact angle conditions where severe skidding occurs. The hypothesis that the percentage variation of the spacing between impulses in a defective ball bearing was about 1-2% reported in previous investigations can be satisfied only for the conditions where the skidding effect in a bearing is slight. Finally, the proposed method is verified with two experiments.

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

Time Series of SO2 Flux from Popocatépetl Volcano by an Ultra-Violet Camera with a Set of Different Band-Pass Filters

Science.gov (United States)

Schiavo, B.; Stremme, W.; Grutter, M.; Campion, R.; Rivera, C. I.; Inguaggiato, S.

2017-12-01

The measurement of SO2flux from active volcanoes are of great importance, for monitoring and hazard of volcanic activity, environmental impact and flux emissions related to changes of magmatic activity. Sulfur dioxide total flux from Popocatépetl volcano was determinad using a ultra-violet camera (or SO2 camera) with different band-pass filter. The flux is obteined from the product of the gas concentration over integrated the plume cross-section (slant column in molec/cm2 or ppm*m) and wind velocity data. Model of plume altitude and wind speed measurement are used to calculate a wind velocity, but a new method of sequential images is widely used in several years for this calculation. Volcanic plume measurements, for a total of about 60 days from from January to March 2017, were collected and utilized to generate the SO2 time series. The importance of monitoring and the time series of volcanic gas emissions is described and proven by many scientific studies. A time series of the Popocatépetl volcano will allow us to detect the volcanic gas as well as anomalies in volcanic processes and help to estimate the average SO2 flux of the volcano. We present a detailed description of the posterior correction of the dilution effect, which occurs due to a simplification of the radiative transfer equation. The correction scheme is especial applicable for long term monitoring from a permanent observation site. Images of volcanic SO2 plumes from the active Popocatépetl volcano in Mexico are presented, showing persistent passive degassing. The measurment are taken from the Altzomoni Atmospheric Observatory (19.12N, -98.65W, 3,985 m.a.s.l.), which forms part of the RUOA (www.ruoa.unam.mx) and NDACC (https://www2.acom.ucar.edu/irwg) networks. It is located north of the crater at 11 km distance. The data to calculate SO2 flux (t/d or kg/s) were recorded with the QSI UV camera and processed using Python scripts.

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...

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.

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

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

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.

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

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.

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

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.

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

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.

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

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

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

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.

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

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.

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.

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.

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.

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

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)

Proposal of a fluid flow layout to improve the heat transfer in the active absorber surface of solar central cavity receivers

International Nuclear Information System (INIS)

Montes, M.J.; Rovira, A.; Martínez-Val, J.M.; Ramos, A.

2012-01-01

The main objective of concentrated solar power is to increase the thermal energy of a fluid, for the fluid to be used, for example, in a power cycle to generate electricity. Such applications present the requirement of appropriately designing the receiver active absorber surface, as the incident radiation flux can be very high. Besides that, the solar image in the receiver is not uniform, so conventional boilers designs are not well suited for these purposes. That point is particularly critical in solar central receivers systems (CRS), where concentrated solar flux is usually above 500 kW/m 2 , causing thermal and mechanical stress in the absorber panels. This paper analyzes a new thermofluidynamic design of a solar central receiver, which optimizes the heat transfer in the absorber surface. This conceptual receiver presents the following characteristics: the fluid flow pattern is designed according to the radiation flux map symmetry, so more uniform fluid temperatures at the receiver outlet are achieved; the heat transfer irreversibilities are reduced by circulating the fluid from the lower temperature region to the higher temperature region of the absorber surface; the width of each pass is adjusted to the solar flux gradient, to get lower temperature differences between the side tubes of the same pass; and the cooling requirement is ensured by means of adjusting the fluid flow velocity per tube, taking into account the pressure drop. This conceptual scheme has been applied to the particular case of a molten salt single cavity receiver, although the configuration proposed is suitable for other receiver designs and working fluids. - Highlights: ► The solar receiver design proposed optimizes heat transfer in the absorber surface. ► The fluid flow pattern is designed according to the solar flux map symmetry at noon. ► The fluid circulates from the lower to the higher temperature regions. ► The width of each pass is adjusted to the solar flux gradient. �

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

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...

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.

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.

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.

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.

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.

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

Repeated sharp flux dropouts observed at 6.6 R/subE/ during a geomagnetic storm

International Nuclear Information System (INIS)

Su, S.; Fritz, T.A.; Konradi, A.

1976-01-01

A number of repeated rapid flux dropouts have been observed at 6.6 R/subE/ by the NOAA low-energy proton detectors on board the ATS 6 satellite during the July 4--6, 1974, geomagnetic storm period. These rapid flux changes are caused by the fact that the outer boundary of the trapped radiation region moves back and forth past the satellite. Although a tilting field line configuration can cause the boundary to pass the satellite, as has frequently been reported in the literature, the boundary is shown to be distorted by a large surface wave traveling eastward around the earth. The maximum velocity of the wave was observed to be approx. =40 km/s

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

Identification of radio emission from the Io flux tube

International Nuclear Information System (INIS)

Riddle, A.C.

1983-01-01

Many theories and observations suggest that Jovian decametric radio emission is generated in flux tubes that pass close to Io's orbit. However, comparison of theory and observation is hindered by lack of knowledge as to which specific flux tube is responsible for a particular emission. In this note, emission from the instantaneous Io flux tube is identified. This makes possible a mapping of emissions onto the causative flux tubes for a significant range of Jovian longitudes (240 0 --360 0 )

Sea ice local surface topography from single-pass satellite InSAR measurements: a feasibility study

Directory of Open Access Journals (Sweden)

W. Dierking

2017-08-01

Full Text Available Quantitative parameters characterizing the sea ice surface topography are needed in geophysical investigations such as studies on atmosphere–ice interactions or sea ice mechanics. Recently, the use of space-borne single-pass interferometric synthetic aperture radar (InSAR for retrieving the ice surface topography has attracted notice among geophysicists. In this paper the potential of InSAR measurements is examined for several satellite configurations and radar frequencies, considering statistics of heights and widths of ice ridges as well as possible magnitudes of ice drift. It is shown that, theoretically, surface height variations can be retrieved with relative errors  ≤  0.5 m. In practice, however, the sea ice drift and open water leads may contribute significantly to the measured interferometric phase. Another essential factor is the dependence of the achievable interferometric baseline on the satellite orbit configurations. Possibilities to assess the influence of different factors on the measurement accuracy are demonstrated: signal-to-noise ratio, presence of a snow layer, and the penetration depth into the ice. Practical examples of sea surface height retrievals from bistatic SAR images collected during the TanDEM-X Science Phase are presented.

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

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

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.

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.

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.

TREEDE, Point Fluxes and Currents Based on Track Rotation Estimator by Monte-Carlo Method

International Nuclear Information System (INIS)

Dubi, A.

1985-01-01

1 - Description of problem or function: TREEDE is a Monte Carlo transport code based on the Track Rotation estimator, used, in general, to calculate fluxes and currents at a point. This code served as a test code in the development of the concept of the Track Rotation estimator, and therefore analogue Monte Carlo is used (i.e. no importance biasing). 2 - Method of solution: The basic idea is to follow the particle's track in the medium and then to rotate it such that it passes through the detector point. That is, rotational symmetry considerations (even in non-spherically symmetric configurations) are applied to every history, so that a very large fraction of the track histories can be rotated and made to pass through the point of interest; in this manner the 1/r 2 singularity in the un-collided flux estimator (next event estimator) is avoided. TREEDE, being a test code, is used to estimate leakage or in-medium fluxes at given points in a 3-dimensional finite box, where the source is an isotropic point source at the centre of the z = 0 surface. However, many of the constraints of geometry and source can be easily removed. The medium is assumed homogeneous with isotropic scattering, and one energy group only is considered. 3 - Restrictions on the complexity of the problem: One energy group, a homogeneous medium, isotropic scattering

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

Just passing through --- high Hg deposition to Puerto Rico forest moves quickly off the landscape

Science.gov (United States)

Shanley, J. B.; Willenbring, J. K.; Kaste, J. M.; Occhi, M.; McDowell, W. H.

2012-12-01

Atmospheric mercury (Hg) in wet deposition at the Luquillo Experimental Forest in northeastern Puerto Rico, averages 28 μg m-2 yr-1, higher than any site in the USA Mercury Deposition Network. Despite the high deposition, Hg content of soils, vegetation, and biota are below global averages. The low Hg content of watershed surfaces, coupled with exceptionally high stream total Hg flux, suggest that most of the Hg passes through the watershed with minimal retention. We assessed Hg dynamics in two adjacent watersheds, Rio Icacos underlain by quartz diorite, and Rio Mameyes underlain by volcaniclastic rocks. At both sites, high-flow Hg concentrations approached 100 ng L-1, dominated by particulate Hg. In order to assess the apparent pass-through nature of Hg in this tropical forest, we measured 7Be and 10Be isotopes from natural, cosmogenic fallout adsorbed on stream suspended particles to constrain the Hg age /residence time and source (atmospheric vs. geogenic or legacy Hg from 19th century gold mining). Ubiquitous 7Be (half-life 53 days) and relatively high 7Be/10Be ratios on suspended particles suggest that stream Hg was dominated by erosion from exposed surfaces, supporting a short residence time. The low watershed retention of the high Hg throughput limits adverse biological effects in this tropical ecosystem.

Common pass decentered annular ring resonator

Energy Technology Data Exchange (ETDEWEB)

Holmes, D. A.; Waite, T. R.

1985-04-30

An optical resonator having an annular cylindrical gain region for use in a chemical laser or the like in which two ring-shaped mirrors having substantially conical reflecting surfaces are spaced apart along a common axis of revolution of the respective conical surfaces. A central conical mirror reflects incident light directed along said axis radially outwardly to the reflecting surface of a first one of the ring-shaped mirrors. The radial light rays are reflected by the first ring mirror to the second ring mirror within an annular cylindrical volume concentric with said common axis and forming a gain region. Light rays impinging on the second ring mirror are reflected to diametrically opposite points on the same conical mirror surfaces and back to the first ring mirror through the same annular cylindrical volume. The return rays are then reflected by the conical mirror surface of the first ring mirror back to the central conical mirror. The mirror surfaces are angled such that the return rays are reflected back along the common axis by the central mirror in a concentric annular cylindrical volume. A scraper mirror having a central opening centered on said axis and an offset opening reflects all but the rays passing through the two openings in an output beam. The rays passing through the second opening are reflected back through the first opening to provide feedback.

9 CFR 310.6 - Carcasses and parts passed for cooking; marking.

Science.gov (United States)

2010-01-01

... 9 Animals and Animal Products 2 2010-01-01 2010-01-01 false Carcasses and parts passed for cooking... INSPECTION AND CERTIFICATION POST-MORTEM INSPECTION § 310.6 Carcasses and parts passed for cooking; marking. Carcasses and parts passed for cooking shall be marked conspicuously on the surface tissues thereof by a...

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....

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.

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.

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.

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

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

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.

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.)

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.

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....

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

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

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.

STUDY OF UREMIC TOXIN FLUXES ACROSS NANOFABRICATED HEMODIALYSIS MEMBRANES USING IRREVERSIBLE THERMODYNAMICS

Directory of Open Access Journals (Sweden)

Assem Hedayat

2013-03-01

Conclusions: Nanofabricated hemodialysis membranes with a reduced thickness and an applied electric potential can enhance the effective diffusivity and electro-migration flux of the respective uremic toxins by 3 orders of magnitude as compared to those passing through the high flux hemodialyzer.

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

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

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.

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.

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...

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)

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.

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

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

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.

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

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

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.

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.

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)

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)

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.

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.

Spotted star light curve numerical modeling technique and its application to HII 1883 surface imaging

Science.gov (United States)

Kolbin, A. I.; Shimansky, V. V.

2014-04-01

We developed a code for imaging the surfaces of spotted stars by a set of circular spots with a uniform temperature distribution. The flux from the spotted surface is computed by partitioning the spots into elementary areas. The code takes into account the passing of spots behind the visible stellar limb, limb darkening, and overlapping of spots. Modeling of light curves includes the use of recent results of the theory of stellar atmospheres needed to take into account the temperature dependence of flux intensity and limb darkening coefficients. The search for spot parameters is based on the analysis of several light curves obtained in different photometric bands. We test our technique by applying it to HII 1883.

The use of large surface area for particle and power deposition

International Nuclear Information System (INIS)

Seigneur, A.; Guilhem, D.; Hogan, J.

1993-01-01

Since the parallel heat flux passing through the LCFS has increased dramatically with the size of machines one has to cope with very large particle and power fluxes on the limiters. Thus the size of the limiters has been increased by the use of inner bumper limiters (for example in JET, TFTR, TORE-SUPRA and JT60). The 'exponential-sine' model is widely used to estimate the heat flux (Q) to a wall for a plasma flux surface with incident angle θ. The model predict Q = q || (0) sinθ e -ρ/λ q + q(0) cosθ e -ρ/λ q , (where θ=0 o when the flux surface is exactly tangential to the limiting surface), ρ is the minor radius measured from the last closed flux surface (LCFS), λ q is the SOL decay length of the heat flux density and q(0) is the heat flux density at the last closed surface. If we approximate the heat flux as Q = q || (0) e -ρ/λ q sin(θ+α), with α ≡ tan -1 [q(0)/q || (0)], then α can be interpreted as an effective 'minimum angle of incidence'. Under conditions where the geometric angle θ has been made almost grazing (below 5 o ) the predictions of the simplest model (with α=0 o ) is not adequate to represent the observation made in TORE-SUPRA; a similar result is found in TFTR. Experimental observations of heat and particle deposition on the large area limiter on the inner wall of TORE-SUPRA are presented. These results have been analyzed with a Monte Carlo code (THOR) describing the diffusion of hydrogenic particles across the LCFS to the limiting objects in the Scrape Off Layer (SOL), and by impurity generation calculations using the full 'exponential-sine' model (α ≠ 0) used as input to an impurity (carbon) Monte Carlo code (BBQ). (author) 6 refs., 3 figs., 1 tab

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.

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

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.

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.

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

Rotating flux compressor for energy conversion

International Nuclear Information System (INIS)

Chowdhuri, P.; Linton, T.W.; Phillips, J.A.

1983-01-01

The rotating flux compressor (RFC) converts rotational kinetic energy into an electrical output pulse which would have higher energy than the electrical energy initially stored in the compressor. An RFC has been designed in which wedge-shaped rotor blades pass through the air gaps between successive turns of a solenoid, the stator. Magnetic flux is generated by pulsing the stator solenoids when the inductance is a maximum, i.e., when the flux fills the stator-solenoid volume. Connecting the solenoid across a load conserves the flux which is compressed within the small volume surrounding the stator periphery when the rotor blades cut into the free space between the stator plates, creating a minimum-inductance condition. The unique features of this design are: (1) no electrical connections (brushes) to the rotor; (2) no conventional windings; and (3) no maintenance. The device has been tested up to 5000 rpm of rotor speed

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.

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.

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.

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.

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...

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...

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.

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

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

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.

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

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

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.

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.

A Hybrid Circuit for Spoof Surface Plasmons and Spatial Waveguide Modes to Reach Controllable Band-Pass Filters.

Science.gov (United States)

Zhang, Qian; Zhang, Hao Chi; Wu, Han; Cui, Tie Jun

2015-11-10

We propose a hybrid circuit for spoof surface plasmon polaritons (SPPs) and spatial waveguide modes to develop new microwave devices. The hybrid circuit includes a spoof SPP waveguide made of two anti-symmetric corrugated metallic strips and a traditional substrate integrated waveguide (SIW). From dispersion relations, we show that the electromagnetic waves only can propagate through the hybrid circuit when the operating frequency is less than the cut-off frequency of the SPP waveguide and greater than the cut-off frequency of SIW, generating efficient band-pass filters. We demonstrate that the pass band is controllable in a large range by designing the geometrical parameters of SPP waveguide and SIW. Full-wave simulations are provided to show the large adjustability of filters, including ultra wideband and narrowband filters. We fabricate a sample of the new hybrid device in the microwave frequencies, and measurement results have excellent agreements to numerical simulations, demonstrating excellent filtering characteristics such as low loss, high efficiency, and good square ratio. The proposed hybrid circuit gives important potential to accelerate the development of plasmonic integrated functional devices and circuits in both microwave and terahertz frequencies.

Contact conditions in skin-pass rolling

DEFF Research Database (Denmark)

Kijima, Hideo; Bay, Niels

2007-01-01

The special contact conditions in skin-pass rolling of steel strip is analysed by studying plane strain upsetting of thin sheet with low reduction applying long narrow tools and dry friction conditions. An extended sticking region is estimated by an elasto-plastic FEM analysis of the plane strain...... upsetting. This sticking region causes a highly inhomogeneous elasto-plastic deformation with large influence of work-hardening and friction. A numerical analysis of skin-pass rolling shows the same contact conditions, i.e. an extended sticking region around the center of the contact zone. The calculated...... size of the sticking region with varying contact length and pressure/reduction is experimentally verified by plane strain upsetting tests measuring the local surface deformation of the work pieces after unloading....

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.

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.

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

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).

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.

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.

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.

Virtual disjunct eddy covariance measurements of organic compound fluxes from a subalpine forest using proton transfer reaction mass spectrometry

Directory of Open Access Journals (Sweden)

T. G. Karl

2002-01-01

Full Text Available A `virtual' disjunct eddy covariance (vDEC device was tested with field measurements of biogenic VOC fluxes at a subalpine forest site in the Rocky Mountains of the USA. A PTR-MS instrument was used as the VOC sensor. Daily peak emission fluxes of 2-methyl-3-buten-2-ol (MBO, methanol, acetone and acetaldehyde were around 1.5, 1, 0.8 and 0.4 mg m-2 h-1, respectively. High pass filtering due to long sampling lines was investigated in laboratory experiments, and suggested that VOC losses in PTFA lines are generally governed by diffusion laws. Memory effects and surface reactions did not seem to play a dominant role. Model estimates of MBO fluxes compared well with measured fluxes. The results also suggest that latent heat and sensible heat fluxes are reasonably well correlated with VOC fluxes and could be used to predict variations in VOC emissions. The release of MBO, methanol, acetone and acetaldehyde resulted in significant change of tropospheric oxidant levels and a 10--40% increase in ozone levels, as inferred from a photochemical box model. We conclude that vDEC with a PTR-MS instrument is a versatile tool for simultaneous field analysis of multiple VOC fluxes.

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

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

Experimental investigation of the characteristics of a laser beam passing through a fluid layer for surface quality in-process measurement

International Nuclear Information System (INIS)

Guo, Ruipeng; Tao, Zhengsu

2010-01-01

The optical characteristics of a laser beam passing through a fluid parallel layer are examined through a series of experimental tests in this project. The experimental apparatus consists of a bare surface quality measurement system and a fluid-supporting system. In the case of laser beam propagation through the static fluid layer, a modified Beckmann–Kirchhoff scattering model has been developed. Based on this model, the results of the surface quality in-process optical measurement can be amended. By extracting a ratio parameter from the image of the scattered light pattern to estimate surface roughness, the modified model can be verified quantitatively in the experimental system. As far as laser beam propagation through the flowing fluid layer is concerned, the deflection of the laser beam caused by fluid flow is small. The experiments are conducted to investigate the characteristics, and the results show that the resulting measurement error for surface quality optical measurement is in an acceptable range

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.

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.

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...

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.

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)

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.

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.

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

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.

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.

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

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

The ion environment near Europa and its role in surface energetics

Science.gov (United States)

Paranicas, C.; Ratliff, J. M.; Mauk, B. H.; Cohen, C.; Johnson, R. E.

2002-03-01

This paper gives the composition, energy spectra, and time variability of energetic ions measured just upstream of Europa. From 100 keV to 100 MeV, ion intensities vary by less than a factor of ~5 among Europa passes considered between 1997 and 2000. We use the data to estimate the radiation dose rate into Europa's surface for depths 0.01 mm - 1 m. We find that in a critical fraction of the upper layer on Europa's trailing hemisphere, energetic electrons are the principal agent for radiolysis, and their bremsstrahlung photon products, not included in previous studies, dominate the dose below about 1 m. Because ion bombardment is more uniform across Europa's surface, the radiation dose on the leading hemisphere is dominated by the proton flux. Differences exist between this calculation and published doses based on the E4 wake pass. For instance, proton doses presented here are much greater below 1 mm.

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.

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.

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)

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.

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

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

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

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.

Experimental evidence for multi-pass extraction with a bent crystal

CERN Document Server

Dehning, Bernd; Fidecaro, Giuseppe; Gyr, Marcel; Herr, Werner; Klem, J T; Scandale, Walter; Vuagnin, G; Weisse, E; Weisz, S; Møller, S P; Uggerhøj, Erik; Freund, A; Hustache, R; Carboni, G; Bussa, M P; Tosello, F

1996-01-01

The feasibility of extracting particles from the halo of a circulating proton beam using a bent silicon crystal has been demonstrated experimentally at the SPS for a beam energy of 120 GeV. Presently studies are conducted to understand the extraction mechanisms and the measured efficiencies. In particular the contribution of multi-pass extraction, where the particles can pass through the crystal many times before being channelled and extracted, is investigated. In a recent experiment, using a crystal especially fabricated with a finite amorphous layer on its surface, it has been proven that multi-pass extraction plays an important role. The experiment is described and the implication for further studies are discussed.

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.

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

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)

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.

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.

Passing and Catching in Rugby.

Science.gov (United States)

Namudu, Mike M.

This booklet contains the fundamentals for rugby at the primary school level. It deals primarily with passing and catching the ball. It contains instructions on (1) holding the ball for passing, (2) passing the ball to the left--standing, (3) passing the ball to the left--running, (4) making a switch pass, (5) the scrum half's normal pass, (6) the…

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.

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

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....

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.

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

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.

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

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....

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.

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.

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

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...

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.

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

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

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.

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...

Structural Controls of the Emerson Pass Geothermal System, Washoe County, Nevada

Energy Technology Data Exchange (ETDEWEB)

Anderson, Ryan B [Nevada Bureau of Mines and Geology, University of Nevada, Reno; Faulds, James E [Nevada Bureau of Mines and Geology, University of Nevada, Reno

2012-09-30

We have conducted a detailed geologic study to better characterize a blind geothermal system in Emerson Pass on the Pyramid Lake Paiute Tribe Reservation, western Nevada. A thermal anomaly was discovered in Emerson Pass by use of 2 m temperature surveys deployed within a structurally favorable setting and proximal to surface features indicative of geothermal activity. The anomaly lies at the western edge of a broad left step at the northeast end of Pyramid Lake between the north- to north-northeast-striking, west-dipping, Fox and Lake Range normal faults. The 2-m temperature surveys have defined a N-S elongate thermal anomaly that has a maximum recorded temperature of ~60°C and resides on a north- to north-northeaststriking fault. Travertine mounds, chalcedonic silica veins, and silica cemented Pleistocene lacustrine gravels in Emerson Pass indicate a robust geothermal system active at the surface in the recent past. Structural complexity and spatial heterogeneities of the strain and stress field have developed in the step-over region, but kinematic data suggest a WNW-trending (~280° azimuth) extension direction. The geothermal system is likely hosted in Emerson Pass as a result of enhanced permeability generated by the intersection of two oppositely dipping, southward terminating north- to north-northwest-striking (Fox Range fault) and northnortheast- striking faults.

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%.

Eddy covariance carbonyl sulfide flux measurements with a quantum cascade laser absorption spectrometer

Directory of Open Access Journals (Sweden)

K. Gerdel

2017-09-01

Full Text Available The trace gas carbonyl sulfide (COS has lately received growing interest from the eddy covariance (EC community due to its potential to serve as an independent approach for constraining gross primary production and canopy stomatal conductance. Thanks to recent developments of fast-response high-precision trace gas analysers (e.g. quantum cascade laser absorption spectrometers, QCLAS, a handful of EC COS flux measurements have been published since 2013. To date, however, a thorough methodological characterisation of QCLAS with regard to the requirements of the EC technique and the necessary processing steps has not been conducted. The objective of this study is to present a detailed characterisation of the COS measurement with the Aerodyne QCLAS in the context of the EC technique and to recommend best EC processing practices for those measurements. Data were collected from May to October 2015 at a temperate mountain grassland in Tyrol, Austria. Analysis of the Allan variance of high-frequency concentration measurements revealed the occurrence of sensor drift under field conditions after an averaging time of around 50 s. We thus explored the use of two high-pass filtering approaches (linear detrending and recursive filtering as opposed to block averaging and linear interpolation of regular background measurements for covariance computation. Experimental low-pass filtering correction factors were derived from a detailed cospectral analysis. The CO2 and H2O flux measurements obtained with the QCLAS were compared with those obtained with a closed-path infrared gas analyser. Overall, our results suggest small, but systematic differences between the various high-pass filtering scenarios with regard to the fraction of data retained in the quality control and flux magnitudes. When COS and CO2 fluxes are combined in the ecosystem relative uptake rate, systematic differences between the high-pass filtering scenarios largely cancel out, suggesting that

Eddy covariance carbonyl sulphide flux measurements with a quantum cascade laser absorption spectrometer.

Science.gov (United States)

Gerdel, Katharina; Spielmann, Felix Maximilian; Hammerle, Albin; Wohlfahrt, Georg

2017-09-26

The trace gas carbonyl sulphide (COS) has lately received growing interest in the eddy covariance (EC) community due to its potential to serve as an independent approach for constraining gross primary production and canopy stomatal conductance. Thanks to recent developments of fast-response high-precision trace gas analysers (e.g. quantum cascade laser absorption spectrometers (QCLAS)), a handful of EC COS flux measurements have been published since 2013. To date, however, a thorough methodological characterisation of QCLAS with regard to the requirements of the EC technique and the necessary processing steps has not been conducted. The objective of this study is to present a detailed characterization of the COS measurement with the Aerodyne QCLAS in the context of the EC technique, and to recommend best EC processing practices for those measurements. Data were collected from May to October 2015 at a temperate mountain grassland in Tyrol, Austria. Analysis of the Allan variance of high-frequency concentration measurements revealed sensor drift to occur under field conditions after an averaging time of around 50 s. We thus explored the use of two high-pass filtering approaches (linear detrending and recursive filtering) as opposed to block averaging and linear interpolation of regular background measurements for covariance computation. Experimental low-pass filtering correction factors were derived from a detailed cospectral analysis. The CO 2 and H 2 O flux measurements obtained with the QCLAS were compared against those obtained with a closed-path infrared gas analyser. Overall, our results suggest small, but systematic differences between the various high-pass filtering scenarios with regard to the fraction of data retained in the quality control and flux magnitudes. When COS and CO 2 fluxes are combined in the so-called ecosystem relative uptake rate, systematic differences between the high-pass filtering scenarios largely cancel out, suggesting that this

Multi-pass spectroscopic ellipsometry

International Nuclear Information System (INIS)

Stehle, Jean-Louis; Samartzis, Peter C.; Stamataki, Katerina; Piel, Jean-Philippe; Katsoprinakis, George E.; Papadakis, Vassilis; Schimowski, Xavier; Rakitzis, T. Peter; Loppinet, Benoit

2014-01-01

Spectroscopic ellipsometry is an established technique, particularly useful for thickness measurements of thin films. It measures polarization rotation after a single reflection of a beam of light on the measured substrate at a given incidence angle. In this paper, we report the development of multi-pass spectroscopic ellipsometry where the light beam reflects multiple times on the sample. We have investigated both theoretically and experimentally the effect of sample reflectivity, number of reflections (passes), angles of incidence and detector dynamic range on ellipsometric observables tanΨ and cosΔ. The multiple pass approach provides increased sensitivity to small changes in Ψ and Δ, opening the way for single measurement determination of optical thickness T, refractive index n and absorption coefficient k of thin films, a significant improvement over the existing techniques. Based on our results, we discuss the strengths, the weaknesses and possible applications of this technique. - Highlights: • We present multi-pass spectroscopic ellipsometry (MPSE), a multi-pass approach to ellipsometry. • Different detectors, samples, angles of incidence and number of passes were tested. • N passes improve polarization ratio sensitivity to the power of N. • N reflections improve phase shift sensitivity by a factor of N. • MPSE can significantly improve thickness measurements in thin films

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

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.

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.

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

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.

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.

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.

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.

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.

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.

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

Planetary cores, their energy flux relationship, and its implications

Science.gov (United States)

Johnson, Fred M.

2018-02-01

Integrated surface heat flux data from each planet in our solar system plus over 50 stars, including our Sun, was plotted against each object's known mass to generate a continuous exponential curve at an R-squared value of 0.99. The unexpected yet undeniable implication of this study is that all planets and celestial objects have a similar mode of energy production. It is widely accepted that proton-proton reactions require hydrogen gas at temperatures of about 15 million degrees, neither of which can plausibly exist inside a terrestrial planet. Hence, this paper proposes a nuclear fission mechanism for all luminous celestial objects, and uses this mechanism to further suggest a developmental narrative for all celestial bodies, including our Sun. This narrative was deduced from an exponential curve drawn adjacent to the first and passing through the Earth's solid core (as a known prototype). This trend line was used to predict the core masses for each planet as a function of its luminosity.

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.

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.

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.

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)

Ultrastructural evaluation of multiple pass low energy versus single pass high energy radio-frequency treatment.

Science.gov (United States)

Kist, David; Burns, A Jay; Sanner, Roth; Counters, Jeff; Zelickson, Brian

2006-02-01

The radio-frequency (RF) device is a system capable of volumetric heating of the mid to deep dermis and selective heating of the fibrous septa strands and fascia layer. Clinically, these effects promote dermal collagen production, and tightening of these deep subcutaneous structures. A new technique of using multiple low energy passes has been described which results in lower patient discomfort and fewer side effects. This technique has also been anecdotally described as giving more reproducible and reliable clinical results of tissue tightening and contouring. This study will compare ultrastructural changes in collagen between a single pass high energy versus up to five passes of a multiple pass lower energy treatment. Three subjects were consented and treated in the preauricular region with the RF device using single or multiple passes (three or five) in the same 1.5 cm(2) treatment area with a slight delay between passes to allow tissue cooling. Biopsies from each treatment region and a control biopsy were taken immediately, 24 hours or 6 months post treatment for electron microscopic examination of the 0-1 mm and 1-2 mm levels. Sections of tissue 1 mm x 1 mm x 80 nm were examined with an RCA EMU-4 Transmission Electron Microscope. Twenty sections from 6 blocks from each 1 mm depth were examined by 2 blinded observers. The morphology and degree of collagen change in relation to area examined was compared to the control tissue, and estimated using a quantitative scale. Ultrastructural examination of tissue showed that an increased amount of collagen fibril changes with increasing passes at energies of 97 J (three passes) and 122 J (five passes), respectively. The changes seen after five multiple passes were similar to those detected after much more painful single pass high-energy treatments. This ultrastructural study shows changes in collagen fibril morphology with an increased effect demonstrated at greater depths of the skin with multiple low-fluence passes

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.

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...

TPG bus passes

CERN Multimedia

Staff Association

2013-01-01

The CERN Staff Association will stop selling TPG bus passes. All active and retired members of the CERN personnel will be able to purchase Unireso bus passes from the CERN Hostel - Building 39 (Meyrin site) from 1st February 2013. For more information: https://cds.cern.ch/journal/CERNBulletin/2013/04/Announcements/1505279?ln=en

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.

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

Message-passing-interface-based parallel FDTD investigation on the EM scattering from a 1-D rough sea surface using uniaxial perfectly matched layer absorbing boundary.

Science.gov (United States)

Li, J; Guo, L-X; Zeng, H; Han, X-B

2009-06-01

A message-passing-interface (MPI)-based parallel finite-difference time-domain (FDTD) algorithm for the electromagnetic scattering from a 1-D randomly rough sea surface is presented. The uniaxial perfectly matched layer (UPML) medium is adopted for truncation of FDTD lattices, in which the finite-difference equations can be used for the total computation domain by properly choosing the uniaxial parameters. This makes the parallel FDTD algorithm easier to implement. The parallel performance with different processors is illustrated for one sea surface realization, and the computation time of the parallel FDTD algorithm is dramatically reduced compared to a single-process implementation. Finally, some numerical results are shown, including the backscattering characteristics of sea surface for different polarization and the bistatic scattering from a sea surface with large incident angle and large wind speed.

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.

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...

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...

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

Surface modifications of AISI 420 stainless steel by low energy Yttrium ions

Science.gov (United States)

Nassisi, Vincenzo; Delle Side, Domenico; Turco, Vito; Martina, Luigi

2018-01-01

In this work, we study surface modifications of AISI 420 stainless steel specimens in order to improve their surface properties. Oxidation resistance and surface micro-hardness were analyzed. Using an ion beam delivered by a Laser Ion Source (LIS) coupled to an electrostatic accelerator, we performed implantation of low energy yttrium ions on the samples. The ions experienced an acceleration passing through a gap whose ends had a potential difference of 60 kV. The gap was placed immediately before the samples surface. The LIS produced high ions fluxes per laser pulse, up to 3x1011 ions/cm2, resulting in a total implanted flux of 7x1015 ions/cm2. The samples were characterized before and after ion implantation using two analytical techniques. They were also thermally treated to investigate the oxide scale. The crystal phases were identified by an X-ray diffractometer, while the micro-hardness was assayed using the scratch test and a profilometer. The first analysis was applied to blank, implanted and thermally treated sample surface, while the latter was applied only to blank and implanted sample surfaces. We found a slight increase in the hardness values and an increase to oxygen resistance. The implantation technique we used has the advantages, with respect to conventional methods, to modify the samples at low temperature avoiding stray diffusion of ions inside the substrate bulk.

Surface modifications of AISI 420 stainless steel by low energy Yttrium ions

Directory of Open Access Journals (Sweden)

Nassisi Vincenzo

2018-01-01

Full Text Available In this work, we study surface modifications of AISI 420 stainless steel specimens in order to improve their surface properties. Oxidation resistance and surface micro-hardness were analyzed. Using an ion beam delivered by a Laser Ion Source (LIS coupled to an electrostatic accelerator, we performed implantation of low energy yttrium ions on the samples. The ions experienced an acceleration passing through a gap whose ends had a potential difference of 60 kV. The gap was placed immediately before the samples surface. The LIS produced high ions fluxes per laser pulse, up to 3x1011 ions/cm2, resulting in a total implanted flux of 7x1015 ions/cm2. The samples were characterized before and after ion implantation using two analytical techniques. They were also thermally treated to investigate the oxide scale. The crystal phases were identified by an X-ray diffractometer, while the micro-hardness was assayed using the scratch test and a profilometer. The first analysis was applied to blank, implanted and thermally treated sample surface, while the latter was applied only to blank and implanted sample surfaces. We found a slight increase in the hardness values and an increase to oxygen resistance. The implantation technique we used has the advantages, with respect to conventional methods, to modify the samples at low temperature avoiding stray diffusion of ions inside the substrate bulk.

Heat Flux Tests of the ITER FWQMs at KoHLT-1

International Nuclear Information System (INIS)

Bae, Young Dug; Kim, Suk Kwon; Shin, Hee Yun; Lee, Dong Won; Hong, Bong Guen

2009-05-01

As a party of the ITER, especially as a procurement party of the ITER blanket, we have designed the First Wall Qualification Mockup (FWQM) and fabricated five FWQMs. Two of them have been tested up to 12,690/12,020 cycles at a heat flux higher than 0.625 MW/m 2 at the KoHLT-1 facility established in the Korea Atomic Energy Research Institute (KAERI). Two KO FWQMs successfully passed the normal heat flux tests, and there was no indication of defect in the Be-to-CuCrZr joints

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

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

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.

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.

WebPASS Explorer (HR Personnel Management)

Data.gov (United States)

US Agency for International Development — WebPass Explorer (WebPASS Framework): USAID is partnering with DoS in the implementation of their WebPass Post Personnel (PS) Module. WebPassPS does not replace...

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.

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...

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)

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.

Near-surface monitoring strategies for geologic carbon dioxide storage verification

Energy Technology Data Exchange (ETDEWEB)

Oldenburg, Curtis M.; Lewicki, Jennifer L.; Hepple, Robert P.

2003-10-31

Geologic carbon sequestration is the capture of anthropogenic carbon dioxide (CO{sub 2}) and its storage in deep geologic formations. Geologic CO{sub 2} storage verification will be needed to ensure that CO{sub 2} is not leaking from the intended storage formation and seeping out of the ground. Because the ultimate failure of geologic CO{sub 2} storage occurs when CO{sub 2} seeps out of the ground into the atmospheric surface layer, and because elevated concentrations of CO{sub 2} near the ground surface can cause health, safety, and environmental risks, monitoring will need to be carried out in the near-surface environment. The detection of a CO{sub 2} leakage or seepage signal (LOSS) in the near-surface environment is challenging because there are large natural variations in CO{sub 2} concentrations and fluxes arising from soil, plant, and subsurface processes. The term leakage refers to CO{sub 2} migration away from the intended storage site, while seepage is defined as CO{sub 2} passing from one medium to another, for example across the ground surface. The flow and transport of CO{sub 2} at high concentrations in the near-surface environment will be controlled by its high density, low viscosity, and high solubility in water relative to air. Numerical simulations of leakage and seepage show that CO{sub 2} concentrations can reach very high levels in the shallow subsurface even for relatively modest CO{sub 2} leakage fluxes. However, once CO{sub 2} seeps out of the ground into the atmospheric surface layer, surface winds are effective at dispersing CO{sub 2} seepage. In natural ecological systems with no CO{sub 2} LOSS, near-surface CO{sub 2} fluxes and concentrations are controlled by CO{sub 2} uptake by photosynthesis, and production by root respiration, organic carbon biodegradation in soil, deep outgassing of CO{sub 2}, and by exchange of CO{sub 2} with the atmosphere. Existing technologies available for monitoring CO{sub 2} in the near-surface environment

Full Coupling Between the Atmosphere, Surface, and Subsurface for Integrated Hydrologic Simulation

Science.gov (United States)

Davison, Jason Hamilton; Hwang, Hyoun-Tae; Sudicky, Edward A.; Mallia, Derek V.; Lin, John C.

2018-01-01

An ever increasing community of earth system modelers is incorporating new physical processes into numerical models. This trend is facilitated by advancements in computational resources, improvements in simulation skill, and the desire to build numerical simulators that represent the water cycle with greater fidelity. In this quest to develop a state-of-the-art water cycle model, we coupled HydroGeoSphere (HGS), a 3-D control-volume finite element surface and variably saturated subsurface flow model that includes evapotranspiration processes, to the Weather Research and Forecasting (WRF) Model, a 3-D finite difference nonhydrostatic mesoscale atmospheric model. The two-way coupled model, referred to as HGS-WRF, exchanges the actual evapotranspiration fluxes and soil saturations calculated by HGS to WRF; conversely, the potential evapotranspiration and precipitation fluxes from WRF are passed to HGS. The flexible HGS-WRF coupling method allows for unique meshes used by each model, while maintaining mass and energy conservation between the domains. Furthermore, the HGS-WRF coupling implements a subtime stepping algorithm to minimize computational expense. As a demonstration of HGS-WRF's capabilities, we applied it to the California Basin and found a strong connection between the depth to the groundwater table and the latent heat fluxes across the land surface.

"Which pass is better?" Novel approaches to assess passing effectiveness in elite soccer.

Science.gov (United States)

Rein, Robert; Raabe, Dominik; Memmert, Daniel

2017-10-01

Passing behaviour is a key property of successful performance in team sports. Previous investigations however have mainly focused on notational measurements like total passing frequencies which provide little information about what actually constitutes successful passing behaviour. Consequently, this has hampered the transfer of research findings into applied settings. Here we present two novel approaches to assess passing effectiveness in elite soccer by evaluating their effects on majority situations and space control in front of the goal. Majority situations are assessed by calculating the number of defenders between the ball carrier and the goal. Control of space is estimated using Voronoi-diagrams based on the player's positions on the pitch. Both methods were applied to position data from 103 German First division games from the 2011/2012, 2012/2013 and 2014/2015 seasons using a big data approach. The results show that both measures are significantly related to successful game play with respect to the number of goals scored and to the probability of winning a game. The results further show that on average passes from the mid-field into the attacking area are most effective. The presented passing efficiency measures thereby offer new opportunities for future applications in soccer and other sports disciplines whilst maintaining practical relevance with respect to tactical training regimes or game performances analysis. Copyright © 2017 Elsevier B.V. All rights reserved.

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.

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

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

Retrieving SW fluxes from geostationary narrowband radiances for the NASA-CERES SYN1deg product

Science.gov (United States)

Wrenn, F. J., IV; Doelling, D. R.; Liang, L.

2017-12-01

The CERES mission was designed to measure the natural variability of the net TOA flux over long time scales relevant to climate monitoring. To achieve this goal, CERES provides the level-3 SSF1deg, SYN1deg, and EBAF monthly 1° by 1° regional TOA flux. The single satellite (Terra or Aqua) SSF1deg 24-hour shortwave flux is based on one daytime measurements and assumes constant meteorology to model the diurnal change in albedo. To accurately describe regions with a prominent diurnal signal, the SYN1deg Edition4 dataset employs hourly geostationary (GEO) measurements. This improves upon Edition3, which used 3-hourly GEO measurements and with temporal interpolation. The EBAF product combines the temporal stability of the SSF1deg product with the diurnal information from SYN1deg and removes the CERES instrument calibration bias by constraining the net flux balance to the ocean heat storage term. The SYN-1deg product retrieves hourly SW fluxes from GEO measurements. Over regions with large diurnal cycles, such as maritime stratus and land afternoon convective locations, the GEO derived SW fluxes will capture the diurnal flux not observed with Terra or Aqua sun-synchronous satellites. Obtaining fluxes from geostationary satellite radiance is a multistep process. First, most GEO visible imagers lack calibration and must be calibrated to MODIS and VIIRS. Second, the GEO imager visible channel radiances are converted to broadband radiances using empirical and theoretical models. The lack of coincident, collocated, and co-angled GEO and CERES measurements makes building an empirical model difficult. The narrowband to broadband models are a function of surface and cloud conditions, which are difficult to identify due to the inconsistent cloud retrievals between the 16 GEO imagers used in the CERES record. Third, the GEO derived broadband radiances are passed through the CERES angular distribution model (ADM) to convert the radiances to fluxes. Lastly, the GEO derived

Vertical distribution and fluxes of ammonia at Great Dun Fell

Science.gov (United States)

Sutton, M. A.; Perthue, E.; Fowler, D.; Storeton-West, R. L.; Cape, J. N.; Arends, B. G.; Möls, J. J.

As part of the study of the ammonia budget over Great Dun Fell, measurements of fluxes of gaseous ammonia (NH 3) with the hill surface (grass moorland and blanket bog) were made using micrometeorological techniques, to provide information on NH 3 removal by the hill surface and on vertical concentration gradients. Measurements of vertical concentration, χ, profiles of NH 3 concentration were coupled with turbulent diffusivities to determine fluxes, Fg deposition velocities, and canopy resistances, Rc to uptake by the ground. Consistent with published measurements for this site, NH 3 was generally found to deposit efficiently to the vegetation canopy, with mean Rc of 5 and 27 s m - for example days shown. However, short periods of NH 3 emission from the moorland were also observed at small χ (cloud processing: depletion of χ by in-cloud reaction would be expected to favour NH 3 emission from down-wind agricultural land and moorland, though emission from the hill itself during immersion in cloud is unlikely. Comparison of two measurement techniques to determine air concentrations (batch wet rotating denuder, inlet 0.5 m height; continuous wet denuder, inlets 0.3, 2 m heights) showed acceptable agreement, although because vertical concentration gradients were large (small Rc) the height of sampling had a substantial effect. Vertical gradients are also relevant to the use of the measured concentrations as estimates of NH 3 in the air mass passing over the hill, for modelling atmospheric budgets. Where NH 3 deposition occurs at the maximum rate, concentrations measured at 1 m require a 35% correction in neutral conditions when scaling to a reference height of 10 m.

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 ...

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...

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.

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.

The inverse Numerical Computer Program FLUX-BOT for estimating Vertical Water Fluxes from Temperature Time-Series.