WorldWideScience

Sample records for atmospheric surface layer

  1. Acoustic tomography in the atmospheric surface layer

    Directory of Open Access Journals (Sweden)

    A. Ziemann

    Full Text Available Acoustic tomography is presented as a technique for remote monitoring of meteorological quantities. This method and a special algorithm of analysis can directly produce area-averaged values of meteorological parameters. As a result consistent data will be obtained for validation of numerical atmospheric micro-scale models. Such a measuring system can complement conventional point measurements over different surfaces. The procedure of acoustic tomography uses the horizontal propagation of sound waves in the atmospheric surface layer. Therefore, to provide a general overview of sound propagation under various atmospheric conditions a two-dimensional ray-tracing model according to a modified version of Snell's law is used. The state of the crossed atmosphere can be estimated from measurements of acoustic travel time between sources and receivers at different points. Derivation of area-averaged values of the sound speed and furthermore of air temperature results from the inversion of travel time values for all acoustic paths. Thereby, the applied straight ray two-dimensional tomographic model using SIRT (simultaneous iterative reconstruction technique is characterised as a method with small computational requirements, satisfactory convergence and stability properties as well as simple handling, especially, during online evaluation.

    Key words. Meteorology and atmospheric dynamics (turbulence; instruments and techniques.

  2. Turbulent transport in the atmospheric surface layer

    Energy Technology Data Exchange (ETDEWEB)

    Tagesson, Torbern [Dept. of Physical Geography and Ecosystem Science, Lund Univ., Lund (Sweden)

    2012-04-15

    In the modelling of transport and accumulation of the radioactive isotope carbon-14 (C-14) in the case of a potential release from a future repository of radioactive waste, it is important to describe the transport of the isotope in the atmosphere. This report aims to describe the turbulent transport within the lower part of the atmosphere; the inertial surface layer and the roughness sublayer. Transport in the inertial surface layer is dependent on several factors, whereof some can be neglected under certain circumstances. Under steady state conditions, fully developed turbulent conditions, in flat and horizontal homogeneous areas, it is possible to apply an eddy diffusivity approach for estimating vertical transport of C. The eddy diffusivity model assumes that there is proportionality between the vertical gradient and the transport of C. The eddy diffusivity is depending on the atmospheric turbulence, which is affected by the interaction between mean wind and friction of the ground surface and of the sensible heat flux in the atmosphere. In this report, it is described how eddy diffusivity of the inertial surface layer can be estimated from 3-d wind measurements and measurements of sensible heat fluxes. It is also described how to estimate the eddy diffusivity in the inertial surface layer from profile measurements of temperature and wind speed. Close to the canopy, wind and C profiles are influenced by effects of the surface roughness; this section of the atmosphere is called the roughness sublayer. Its height is up to {approx}3 times the height of the plant canopy. When the mean wind interacts with the canopy, turbulence is not only produced by shear stress and buoyancy, it is additionally created by wakes, which are formed behind the plants. Turbulence is higher than it would be over a flat surface, and the turbulent transport is hereby more efficient. Above the plant canopy, but still within the roughness sublayer, a function that compensates for the effect

  3. Exploring Scintillometry in the Stable Atmospheric Surface Layer

    NARCIS (Netherlands)

    Hartogensis, O.K.

    2006-01-01

    The main objective of this thesis is to investigate observation methods of heat and momentum exchange and key variables that characterise turbulence in the atmospheric stable surface layer (SSL), a layer defined as the lower part of the stable boundary layer (SBL) where surface fluxes do not change

  4. Aspects of the atmospheric surface layers on Mars and Earth

    DEFF Research Database (Denmark)

    Larsen, Søren Ejling; Ejsing Jørgensen, Hans; Landberg, L.

    2002-01-01

    and mean flow on Mars is found to obey the same scaling laws as on Earth. The largest micrometeorological differences between the two atmospheres are associated with the low air density of the Martian atmosphere. Together with the virtual absence of water vapour, it reduces the importance......The structures of mean flow and turbulence in the atmospheric surface boundary layer have been extensively studied on Earth, and to a far less extent on Mars, where only the Viking missions and the Pathfinder mission have delivered in-situ data. Largely the behaviour of surface-layer turbulence...

  5. The determination of turbulent structures in the atmospheric surface layer

    NARCIS (Netherlands)

    Schols, J.L.J.

    1984-01-01

    The turbulent flow in the atmospheric surface layer (ASL) contains turbulent structures, which are defined as spatially coherent, organized flow motions. 'Organized' means that characteristic patterns, observed at a point in space, occur almost simultaneously in more than one turbulence signal and

  6. Whirlwinds and hairpins in the atmospheric surface layer

    NARCIS (Netherlands)

    Oncley, Steven P.; Hartogensis, O.K.; Tong, Chenning

    2016-01-01

    Vortices in the atmospheric surface layer are characterized using observations at unprecedented resolution from a fixed array of 31 turbulence sensors. During the day, these vortices likely are dust devils, though no visual observations are available for confirmation. At night, hairpin vortices

  7. Observations of the atmospheric surface layer parameters over a ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    1999-08-11

    Aug 11, 1999 ... ciated cloud cover softened the expected dramatic changes in the ASL. In the present paper we are reporting the eclipse-induced changes observed in the mean, turbulence parameters and spectra in the atmospheric surface layer during the sudden diminution of solar energy associated with the solar.

  8. Characteristics of turbulent structures in the unstable atmospheric surface layer

    Science.gov (United States)

    Schols, J. L. J.; Jansen, A. E.; Krom, J. G.

    1985-10-01

    An atmospheric surface-layer (ASL) experiment conducted at a meteorological site in the Oostelijk-Flevoland polder of the Netherlands is described. Turbulent fluctuations of wind velocity, air temperature and static pressure were measured, using three 10 m towers. Simultaneous turbulent signals at several heights on the towers were used to investigate the properties of the turbulent structures which contribute most significantly to the turbulent vertical transports in the unstable ASL. These turbulent structures produce between 30 and 50% of the mean turbulent vertical transport of horizontal alongwind momentum and they contribute to between 40 and 50% of the mean turbulent vertical heat transport; in both cases this occurs during 15 to 20% of the total observation time. The translation speed of the turbulent structures equals the wind speed averaged over the depth of the ASL, which scales on the surface friction velocity. The inclination angle of the temperature interface at the upstream edge of the turbulent structures to the surface is significantly smaller than that of the internal shear layer, which is associated with the temperature interface. The turbulent structures in the unstable ASL are determined by a large-scale temperature field: Convective motions, which encompass the whole depth of the planetary boundary layer (PBL), penetrate into the ASL. The curvature of the vertical profile of mean horizontal alongwind velocity forces the alignment of the convective cells in the flow direction (Kuettner, 1971), which have an average length of several hundreds of metres and an average width of a few tens of metres. This mechanism leads to the formation of turbulent structures, which extend throughout the depth of the ASL.

  9. Surface layer conditions of the atmosphere over western Bay of Bengal during Monex

    Digital Repository Service at National Institute of Oceanography (India)

    Anto, A.F.; Rao, L.V.G.; Somayajulu, Y.K.

    Based on surface meteorological data and wave data collected from 2 stations in the western Bay of Bengal in July 1979, surface layer (SL) conditions of the atmosphere for different situations of surface circulations and the associated sea surface...

  10. Directional Shear in the Nocturnal Atmospheric Surface Layer

    Science.gov (United States)

    Mahrt, L.

    2017-10-01

    We examine the potential importance of wind-directional shear in the surface layer of the stable nocturnal boundary layer by analyzing two tower datasets with eddy-correlation measurements at multiple levels. Directional shear is a major contributor to the total vector shear for weak winds due primarily to frequent shallow drainage flows at one site and due primarily to non-stationary modes at the second site. For weak winds, the turbulence intensity is more related to the wind-directional shear than to the wind speed or stratification, at least for these two datasets.

  11. Impacts of Ocean Waves on the Atmospheric Surface Layer: Simulations and Observations

    National Research Council Canada - National Science Library

    Sullivan, Peter P; McWilliams, James C; Melville, W. K

    2008-01-01

    .... Our long term scientific objective was to explore the nature of intermittence, coherent structures, and turbulent fluxes and their coupling in the surface layers of the marine atmospheric and oceanic...

  12. Dynamics of the atmospheric boundary layer response to ocean mesoscale sea surface temperatures

    Science.gov (United States)

    Schneider, Niklas; Taguchi, Bunmei; Nonaka, Masami; Kuwano-Yoshida, Akira; Nakamura, Hisashi

    2017-04-01

    A recent theory for the mid-latitude atmospheric response to ocean mesoscale sea surface temperature (SST) variations is tested in the Southern Ocean using an extended integration of an atmospheric general circulation model. The theory is based on a linearization of the steady state, atmospheric boundary-layer dynamics, and yields the atmospheric response as classical Ekman dynamics extended to include advection, and sea surface temperature induced changes of atmospheric mixing and hydrostatic pressure. The theory predicts the response at each horizontal wave number to be governed by spectral transfer function between sea surface temperature and boundary layer variables, that are dependent on large-scale winds and the formulation of boundary layer mixing. The general circulation model, AFES, is shown to reproduce observed regressions between surface wind stress and sea surface temperatures. These 'coupling coefficients' are explained by SST induced changes of the surface stability, that directly impact surface stress, and changes of the surface winds. Estimates of the spectral transfer function between the latter and surface temperature are consistent with the theory, and suggest that it faithfully captures the underlying physics.

  13. The groundwater-land-surface-atmosphere connection: soil moisture effects on the atmospheric boundary layer in fully-coupled simulations

    Energy Technology Data Exchange (ETDEWEB)

    Maxwell, R M; Chow, F K; Kollet, S J

    2007-02-02

    This study combines a variably-saturated groundwater flow model and a mesoscale atmospheric model to examine the effects of soil moisture heterogeneity on atmospheric boundary layer processes. This parallel, integrated model can represent spatial variations in land-surface forcing driven by three-dimensional (3D) atmospheric and subsurface components. The development of atmospheric flow is studied in a series of idealized test cases with different initial soil moisture distributions generated by an offline spin-up procedure or interpolated from a coarse-resolution dataset. These test cases are performed with both the fully-coupled model (which includes 3D groundwater flow and surface water routing) and the uncoupled atmospheric model. The effects of the different soil moisture initializations and lateral subsurface and surface water flow are seen in the differences in atmospheric evolution over a 36-hour period. The fully-coupled model maintains a realistic topographically-driven soil moisture distribution, while the uncoupled atmospheric model does not. Furthermore, the coupled model shows spatial and temporal correlations between surface and lower atmospheric variables and water table depth. These correlations are particularly strong during times when the land surface temperatures trigger shifts in wind behavior, such as during early morning surface heating.

  14. Buoyancy effect on atmospheric surface layer: measurements from the East Coast of Malaysia

    Science.gov (United States)

    Harun, Z.; Reda, E.; Zulkifli, Rozli

    2017-04-01

    The nature and evolution of the atmospheric surface layer is still unresolved completely. Many questions regarding the existence of the z-less layer and trend of the cross correlations still remain open. This research analyzes some of the surface layer ambiguities. In this research temperature, velocity and turbulence data were collected from a weather station facility located in the Marine Ecosystem Research Centre (EKOMAR) Mersing on the East Coast of Malaysia. Two high resolution hotwires were utilized at 3 m and 12 m heights above ground. Both gradient Richardson number and Obukhov stability parameter were calculated. Turbulence spectra were plotted at different stability conditions. The results does not show the existence of the z-less layer at deep stable condition. The buoyancy force, under unstable condition, was found responsible for the increase of vertical correlation factor. The fingerprint of the buoyancy force was detected in the spectra at low frequencies.

  15. Atmospheric surface layer responses to the extreme lightning day in plateau region in India

    Science.gov (United States)

    Dwivedi, Arun K.; Chandra, Sagarika; Kumar, Manoj; Kumar, Sanjay; Kiran Kumar, N. V. P.

    2014-12-01

    This paper discusses the observations of the atmospheric surface layer (ASL) parameters during the lightning event. During this event behaviour of surface layer parameters has been observed. Other derived parameters like Monin-Obukhov stability parameter (z/L), turbulent kinetic energy (TKE), momentum flux (MF) and sensible heat flux (SHF) have also been considered during this stochastic phenomenon. Characteristics of these surface layer parameters have been analysed during lightning period and compared with the clear weather day. During the peak period of the lightning, the incoming solar irradiance was reduced by one third of its normal value, resulting in an air-temperature decrement near the surface in the range of 4 °C to 6 °C. In addition to that a significant reduction in energy exchanges between surface and lower lying atmosphere (viz. TKE, MF and SHF), has also been observed. The rate of instantaneous decay in solar irradiance and SHF from the first strike to its peak strike time was larger than that seen during clear day hours. The normalized standard deviations of wind components during clear day were studied using Monin-Obukhov similarity theory (MOST) and the results have been compared with earlier studies reported in the literature.

  16. the Martian atmospheric boundary layer

    DEFF Research Database (Denmark)

    Petrosyan, A.; Galperin, B.; Larsen, Søren Ejling

    2011-01-01

    The planetary boundary layer (PBL) represents the part of the atmosphere that is strongly influenced by the presence of the underlying surface and mediates the key interactions between the atmosphere and the surface. On Mars, this represents the lowest 10 km of the atmosphere during the daytime...

  17. Relation between the Atmospheric Boundary Layer and Impact Factors under Severe Surface Thermal Conditions

    Directory of Open Access Journals (Sweden)

    Yinhuan Ao

    2017-01-01

    Full Text Available This paper reported a comprehensive analysis on the diurnal variation of the Atmospheric Boundary Layer (ABL in summer of Badain Jaran Desert and discussed deeply the effect of surface thermal to ABL, including the Difference in Surface-Air Temperature (DSAT, net radiation, and sensible heat, based on limited GPS radiosonde and surface observation data during two intense observation periods of experiments. The results showed that (1 affected by topography of the Tibetan Plateau, the climate provided favorable external conditions for the development of Convective Boundary Layer (CBL, (2 deep CBL showed a diurnal variation of three- to five-layer structure in clear days and five-layer ABL structure often occurred about sunset or sunrise, (3 the diurnal variation of DSAT influenced thickness of ABL through changes of turbulent heat flux, (4 integral value of sensible heat which rapidly converted by surface net radiation had a significant influence on the growth of CBL throughout daytime. The cumulative effect of thick RML dominated the role after CBL got through SBL in the development stage, especially in late summer, and (5 the development of CBL was promoted and accelerated by the variation of wind field and distribution of warm advection in high and low altitude.

  18. Airborne Measurement of Insolation Impact on the Atmospheric Surface Boundary Layer

    Science.gov (United States)

    Jacob, Jamey; Chilson, Phil; Houston, Adam; Detweiler, Carrick; Bailey, Sean; Cloud-Map Team

    2017-11-01

    Atmospheric surface boundary layer measurements of wind and thermodynamic parameters are conducted during variable insolation conditions, including the 2017 eclipse, using an unmanned aircraft system. It is well known that the air temperatures can drop significantly during a total solar eclipse as has been previously observed. In past eclipses, these observations have primarily been made on the ground. We present results from airborne measurements of the near surface boundary layer using a small unmanned aircraft with high temporal resolution wind and thermodynamic observations. Questions that motivate the study include: How does the temperature within the lower atmospheric boundary vary during an eclipse? What impact does the immediate removal of radiative heating on the ground have on the lower ABL? Do local wind patterns change during an eclipse event and if so why? Will there be a manifestation of the nocturnal boundary layer wind maximum? Comparisons are made with the DOE ARM SGP site that experiences a lower but still significant insolation. Supported by the National Science Foundation under Award Number 1539070.

  19. CONCENTRATION OF HARMFUL SUBSTANCES REDUCING IN SURFACE LAYER OF ATMOSPHERE AT RHEOSTAT LOCOMOTIVE TESTS

    Directory of Open Access Journals (Sweden)

    E. A. Bondar

    2010-06-01

    Full Text Available It is shown that at present an acceptable way of reducing the concentration of harmful substances in the surface layer of the atmosphere at rheostat tests of locomotives is their dispersion in a large volume of air. Channels, installed above an exhaust pipe of diesel locomotive with a break at the gas flow, work as ejectors. We have solved jointly the equation of aerodynamic characteristics of the ejector device and the equation of diffusion of gases; as a result the calculated dependence for determining the necessary height of ejector device has been obtained.

  20. Experimental investigation of turbulent transport of momentum and heat in the atmospheric surface layer

    Science.gov (United States)

    Han, Guowen; Zheng, X. J.; Bo, Tianli

    2017-11-01

    In our study, turbulent transport of momentum and heat is investigated in the neutral and unstable atmospheric surface layer (ASL) over the edge of a desert. Our results reveal that with the increase of wind speed the transport efficiencies for momentum and heat increased, furthermore, transport efficiency of momentum increases faster than that of heat. In addition, the method of quadrant analysis and turbulent events were used to analyze the moment flux and heat flux. Experimental results show that the influence of wind speed on moment flux and heat flux can be quite different, which maybe has a great impact on the turbulent transport of momentum and heat in ASL.

  1. Retrieving 4-dimensional atmospheric boundary layer structure from surface observations and profiles over a single station

    Energy Technology Data Exchange (ETDEWEB)

    Pu, Zhaoxia [Univ. of Utah, Salt Lake City, UT (United States)

    2015-10-06

    Most routine measurements from climate study facilities, such as the Department of Energy’s ARM SGP site, come from individual sites over a long period of time. While single-station data are very useful for many studies, it is challenging to obtain 3-dimensional spatial structures of atmospheric boundary layers that include prominent signatures of deep convection from these data. The principal objective of this project is to create realistic estimates of high-resolution (~ 1km × 1km horizontal grids) atmospheric boundary layer structure and the characteristics of precipitating convection. These characteristics include updraft and downdraft cumulus mass fluxes and cold pool properties over a region the size of a GCM grid column from analyses that assimilate surface mesonet observations of wind, temperature, and water vapor mixing ratio and available profiling data from single or multiple surface stations. The ultimate goal of the project is to enhance our understanding of the properties of mesoscale convective systems and also to improve their representation in analysis and numerical simulations. During the proposed period (09/15/2011–09/14/2014) and the no-cost extension period (09/15/2014–09/14/2015), significant accomplishments have been achieved relating to the stated goals. Efforts have been extended to various research and applications. Results have been published in professional journals and presented in related science team meetings and conferences. These are summarized in the report.

  2. Aerosol model development for environmental monitoring in the coastal atmosphere surface layer

    Science.gov (United States)

    Kaloshin, Gennady A.; Matvienko, Gennady G.

    2007-06-01

    Extinction of radiation in the marine boundary layer is dominated by scattering and absorption due to atmospheric aerosol. It is known, that the extinction of optical radiation visible and near IR spectra in the marine surface layer is determined mainly by scattering and absorption atmospheric aerosol. It influences on a dependence of spectral transmission and extinction both natural, and artificial light that is of interest for a wide range of problems, in particular for radiating problems at studying laws of climate formation, and for lines of the applications connected to the forecast of a signal power in coastal conditions at an estimation of EO systems characteristics. This is important to optical retrievals from satellite, remote sensing at environmental monitoring, backscatter of light to space (including climate forcing), cloud properties etc. In unpolluted regions the greatest effects on near shore scattering extinction will be a result of sea-salt from breaking waves and variations in relative humidity. The role of breaking waves appears to be modulated by wind, tide, swell, wave spectra and coastal conditions. These influences will be superimposed upon aerosol generated by open ocean sea-salt aerosol that varies with wind speed. The focus of our study is the extinction and optical effects due to aerosol in a specific coastal region. This involves linking coastal physical properties to oceanic and meteorological parameters in order to develop predictive algorithms that describe 3-D aerosol structure and variability. The aerosol microphysical model of the marine and coastal atmosphere surface layer is considered. The model distinctive feature is parameterization of amplitude and width of the modes as functions of fetch and wind speed. In the paper the dN/dr behavior depending at change meteorological parameters, heights above sea level, fetch, wind speed and RH is show. On the basis of the developed model with usage of Mie theory for spheres the

  3. Interactions of the land-surface with the atmospheric boundary layer

    NARCIS (Netherlands)

    Ek, M.B.

    2005-01-01

    We study daytime land-atmosphere interaction using a one-dimensional (column) coupled land-surface - atmospheric boundary-Iayer (ABL) model and data sets gathered at Cabauw (1978, central Netherlands) and during the Hydrological and Atmospheric Pilot Experiment - Modélisation du Bilan Hydrique

  4. Single Column Modeling of Atmospheric Boundary Layers and the Complex Interactions with the Land Surface

    NARCIS (Netherlands)

    Holtslag, A.A.M.; Steeneveld, G.J.

    2009-01-01

    In this paper a summary is given of the basic approaches for the modeling and parameterization of turbulence in the atmospheric boundary layer. The treated approaches are in current use in regional and global-scale models for the forecasting and study of weather, climate and air quality. Here we

  5. Transport and deposition of nitrogen oxides and ozone in the atmospheric surface layer

    Science.gov (United States)

    Li, Yongxian

    Tropospheric ozone is an important photochemical air pollutant, which increases respiratory-related diseases, decreases crop yields, and causes other environmental problems. This research has focused on the measurement of soil biogenic emissions of nitric oxide (NO), one of the precursors for ozone formation, from intensively managed soils in the Southeast US, and examined the transport and deposition of NOx (NO + NO2) and ozone in the atmospheric surface layer, and the effects of NO emissions and its chemical reactions on ozone flux and deposition to the earth's surface. Emissions of nitric oxide were measured from an intensively managed agricultural soil, in the lower coastal plain of North Carolina (near Plymouth, NC), using a dynamic chamber technique. Measurements of soil NO emissions in several crop canopies were conducted at four different sites in North Carolina during late spring and summer of 1994-1996. The turbulent fluxes of NO2 and O3 at 5 m and 10 m above the ground were measured using the eddy-correlation technique near Plymouth, NC during late spring of 1995 and summer of 1996, concurrent with measurements of soil NO emissions using the dynamic chamber system. Soil NO emission from within the corn field was high averaging approximately 35 ng N/m2/s during the measurement period of 1995. In another study, vertical measurements of ozone were made on a 610 m tall tower located 15 km Southeast of Raleigh, NC during the summers of 1993-1997, as part of an effort by the State of North Carolina to develop a State Implementation Plan (SIP) for ozone control in the Raleigh Metropolitan Statistical Area. A strong correlation was observed between the nighttime and early morning ozone concentrations in the residual layer (CR) above the NBL and the maximum ground level concentration (C o max) the following afternoon. Based on this correlation, an empirical regression equation (Co max = 27.67*exp(0.016 CR)) was developed for predicting maximum ground level ozone

  6. Forecasting of aerosol extinction of the sea and coastal atmosphere surface layer

    Science.gov (United States)

    Kaloshin, G. A.

    2010-04-01

    The focus of our study is the extinction and optical effects due to aerosol in a specific coastal region. The aerosol microphysical model of the marine and coastal atmosphere surface layer is considered. The model is made on the basis of the long-term experimental data received at researches of aerosol sizes distribution function (dN/dr) in the band particles sizes in 0.01 - 100 μk. The model is developed by present time for the band of heights is 0 - 25 m. Bands of wind speed is 3 - 18 km/s, sizes fetch is up to 120 km, RH = 40 - 98 %. Key feature of model is parameterization of amplitude and width of the modes as functions of fetch and wind speed. In the paper the dN/dr behavior depending at change meteorological parameters, heights above sea level, fetch (X), wind speed (U) and RH is show. On the basis of the developed model with usage of Mie theory for spheres the description of last version of developed code MaexPro (Marine Aerosol Extinction Profiles) for spectral profiles of aerosol extinction coefficients α(λ) calculations in the wavelength band, equal λ = 0.2 - 12 μm is presented. The received results are compared models NAN and ANAM. Also α(λ) profiles for various wind modes (combinations X and U) calculated by MaexPro code are given. The calculated spectrums of α(λ) profiles are compared with experimental data of α(λ) received by a transmission method in various geographical areas.

  7. The structure of the atmospheric surface layer subject to local advection

    NARCIS (Netherlands)

    Bink, N.J.

    1996-01-01


    For many applications in agriculture, hydrology and meteorology simple methods are needed to determine the surface-atmosphere exchange of momentum, heat and water vapour, i.e to determine the fluxes of momentum, heat and water vapour. Most methods to calculate these

  8. A bulk similarity approach in the atmospheric boundary layer using radiometric skin temperature to determine regional surface fluxes

    Science.gov (United States)

    Brutsaert, Wilfried; Sugita, Michiaki

    1991-01-01

    Profiles of wind velocity and temperature in the outer region of the atmospheric boundary layer (ABL) were used together with surface temperature measurements, to determine regional shear stress and sensible heat flux by means of transfer parameterizations on the basis of bulk similarity. The profiles were measured by means of radiosondes and the surface temperatures by infrared radiation thermometry over hilly prairie terrain in northeastern Kansas during the First ISLSCP Field Experiment (FIFE). In the analysis, the needed similarity functions were determined and tested.

  9. The WELSONS experiment: overview and presentation of first results on the surface atmospheric boundary-layer in semiarid Spain

    Directory of Open Access Journals (Sweden)

    J.-P. Frangi

    Full Text Available This study presents the preliminary results of the local energy budget and dynamic characteristics of the surface atmospheric boundary-layer (SBL during the WELSONS (wind erosion and losses of soil nutrients in semiarid Spain experiment. Some Mediterranean regions suffer land degradation by wind erosion as a consequence of their particular soil and climate conditions and inappropriate agricultural practice. In Spain, where land degradation by water erosion is well known, the lack of field studies to quantify soils losses by wind erosion resulted in the European Community organizing a scientific program for this specific issue. The European programme known as WELSONS was devoted to study the wind erosion process in central Aragon (NE Spain. This multidisciplinary experiment, which began in 1996 and finished in 1998, was carried out over an agricultural soil which was left fallow. Within the experimental field, two plots were delimited where two tillage treatments were applied, a mould-board ploughing (or conventional tillage denoted CT and chisel ploughing (reduced tillage denoted RT. This was to study on bare soil the influence of tillage method on surface conditions, saltation flux, vertical dust flux, erosion rates, dynamics characteristics such as friction velocity, roughness length, etc., and energy budget. The partitioning of the available energy, resulting from the dynamics of the SBL, are quite different over the two plots because of their own peculiar soil and surface properties. The first results show that the RT treatment seems to provide a wind erosion protection. Because of the long data recording time and particular phenomena (formation of a crust at the soil surface, very dry conditions, high wind speed for instance, these microclimatological data acquired during the WELSONS programmes may be helpful to test atmospheric boundary-layer models coupled with soil models.

    Key words: Hydrology (desertification - Meterology and

  10. Scaling properties of velocity and temperature spectra above the surface friction layer in a convective atmospheric boundary layer

    Directory of Open Access Journals (Sweden)

    K. G. McNaughton

    2007-06-01

    Full Text Available We report velocity and temperature spectra measured at nine levels from 1.42 meters up to 25.7 m over a smooth playa in Western Utah. Data are from highly convective conditions when the magnitude of the Obukhov length (our proxy for the depth of the surface friction layer was less than 2 m. Our results are somewhat similar to the results reported from the Minnesota experiment of Kaimal et al. (1976, but show significant differences in detail. Our velocity spectra show no evidence of buoyant production of kinetic energy at at the scale of the thermal structures. We interpret our velocity spectra to be the result of outer eddies interacting with the ground, not "local free convection".

    We observe that velocity spectra represent the spectral distribution of the kinetic energy of the turbulence, so we use energy scales based on total turbulence energy in the convective boundary layer (CBL to collapse our spectra. For the horizontal velocity spectra this scale is (zi εo2/3, where zi is inversion height and εo is the dissipation rate in the bulk CBL. This scale functionally replaces the Deardorff convective velocity scale. Vertical motions are blocked by the ground, so the outer eddies most effective in creating vertical motions come from the inertial subrange of the outer turbulence. We deduce that the appropriate scale for the peak region of the vertical velocity spectra is (z εo2/3 where z is height above ground. Deviations from perfect spectral collapse under these scalings at large and small wavenumbers are explained in terms of the energy transport and the eddy structures of the flow.

    We find that the peaks of the temperature spectra collapse when wavenumbers are scaled using (z1/2 zi1/2. That is, the lengths of the thermal structures depend on both the lengths of the

  11. The Atmospheric Surface Layer in the Polar Regions of the Earth

    Science.gov (United States)

    Kovadlo, P. G.; Shikhovtsev, A. Yu.; Yazev, S. A.

    2017-05-01

    As studies of the Earth history show the energy power and amount of catastrophic events during the planet evolution has been decreasing. Gradually the Earth "was adjusted" under the influence of external factors and internal sources of energy were weakened. The relative stability of climatic characteristics over millions of years indicates this. The modern surface Earth temperature increasing over the past 150 years has been proved by analyzing the series of network instrumental hydrometeorological measurements. The authors of this study proposed a hypothesis to explain the observed warming of the climate. It is supposed that there was a land with enclosed water reservoirs in the past at the Arctic ocean site. Calculations and observations show that there were favorable conditions for the formation and growth of the perennial glaciers` without access of warm ocean waters in the polar region. Further the mass of the Arctic ice sheet increasing led to subsidence of the earth's crust under the influence of its weight. Low-lying plains under the ice were lower than the ocean level. The access of oceanic waters to the ice sheet led to the washing of the base by the waters of the Atlantic and the Pacific oceans. Warm waters largely destroyed the floating part of the ice sheet. Heat which was spent on melting ice in the past warm up the atmosphere and ocean nowadays. Currently, the final stage of this process is observed and the factors discussed are the main cause of the observed warming.

  12. Measurements of mercury in the near-surface layer of the atmosphere of the Russian Arctic.

    Science.gov (United States)

    Golubeva, N; Burtseva, L; Matishov, G

    2003-05-01

    A series of measurements of gaseous elemental mercury concentrations in near-surface air of the Russian Arctic Region were carried out from 1994 to 1997. The measurements were conducted in Murmansk at a stationary site in April-May 1994, on a cruise in Motovsky Bay and Kola Bay during May-June 1996, and along the Russian Northern Sea Route in April-May 1997 on board the nuclear icebreaker 'Soviet Union'. Silver absorption was used for trapping of mercury and the mass of mercury was determined by cold vapour atomic absorption spectrophotometery. Detection limits were approximately 0.3 ng/m(3) (+/- error 46%). Sixty samples were selected and analysed. Sample volumes were 2.2 m(3) ashore, and up to 6.6 m(3) over water. The meteorological conditions, including a wind speed and direction, during the sampling period were typical of the spring-summer period of year, and therefore the concentrations of atmospheric mercury are regarded as representative for this season. The mean concentrations of mercury ranged from 2.2 ng/m(3) for Murmansk city, 1.7 ng/m(3) for Kola Bay, 1.6 ng/m(3) for Motovsky Bay, 1.1 ng/m(3) for the eastern part of the Barents Sea and 0.7 ng/m(3) for the western part of the Kara Sea. The levels of mercury in Murmansk, and over Kola and Motovsky Bays were associated with a primary direction of a near-surface wind from the nearest sources of mercury emission located in the Russian North region. These are the non-ferrous metallurgical plants in Nickel in the case of Motovsky Bay and Murmansk garbage-disposal plant, for sampling points in Murmansk and over Kola Bay. These concentrations of mercury, measured in the spring-summer season, in near-surface air of the Russian North, are more than two-fold lower than the concentrations that are typical of continental background regions in western Russia, and are comparable to the concentrations measured in the Arctic regions of other countries.

  13. Turbulent characteristics of a semiarid atmospheric surface layer from cup anemometers – effects of soil tillage treatment (Northern Spain

    Directory of Open Access Journals (Sweden)

    S. Yahaya

    2003-10-01

    Full Text Available This paper deals with the characteristics of turbulent flow over two agricultural plots with various tillage treatments in a fallow, semiarid area (Central Aragon, Spain. The main dynamic characteristics of the Atmospheric Surface Layer (ASL measured over the experimental site (friction velocity, roughness length, etc., and energy budget, have been presented previously (Frangi and Richard, 2000. The current study is based on experimental measurements performed with cup anemometers located in the vicinity of the ground at 5 different levels (from 0.25 to 4 m and sampled at 1 Hz. It reveals that the horizontal wind variance, the Eulerian integral scales, the frequency range of turbulence and the turbulent kinetic energy dissipation rate are affected by the surface roughness. In the vicinity of the ground surface, the horizontal wind variance logarithmically increases with height, directly in relation to the friction velocity and the roughness length scale. It was found that the time integral scale (and subsequently the length integral scale increased with the surface roughness and decreased with the anemometer height. These variations imply some shifts in the meteorological spectral gap and some variations of the spectral peak length scale. The turbulent energy dissipation rate, affected by the soil roughness, shows a z-less stratification behaviour under stable conditions. In addition to the characterization of the studied ASL, this paper intends to show which turbulence characteristics, and under what conditions, are accessible through the cup anemometer.Key words. Meteorology and atmospheric dynamics (climatology, turbulence, instruments and techniques

  14. Turbulent characteristics of a semiarid atmospheric surface layer from cup anemometers – effects of soil tillage treatment (Northern Spain

    Directory of Open Access Journals (Sweden)

    S. Yahaya

    Full Text Available This paper deals with the characteristics of turbulent flow over two agricultural plots with various tillage treatments in a fallow, semiarid area (Central Aragon, Spain. The main dynamic characteristics of the Atmospheric Surface Layer (ASL measured over the experimental site (friction velocity, roughness length, etc., and energy budget, have been presented previously (Frangi and Richard, 2000. The current study is based on experimental measurements performed with cup anemometers located in the vicinity of the ground at 5 different levels (from 0.25 to 4 m and sampled at 1 Hz. It reveals that the horizontal wind variance, the Eulerian integral scales, the frequency range of turbulence and the turbulent kinetic energy dissipation rate are affected by the surface roughness. In the vicinity of the ground surface, the horizontal wind variance logarithmically increases with height, directly in relation to the friction velocity and the roughness length scale. It was found that the time integral scale (and subsequently the length integral scale increased with the surface roughness and decreased with the anemometer height. These variations imply some shifts in the meteorological spectral gap and some variations of the spectral peak length scale. The turbulent energy dissipation rate, affected by the soil roughness, shows a z-less stratification behaviour under stable conditions. In addition to the characterization of the studied ASL, this paper intends to show which turbulence characteristics, and under what conditions, are accessible through the cup anemometer.

    Key words. Meteorology and atmospheric dynamics (climatology, turbulence, instruments and techniques

  15. Chemical composition of aerosol in the atmospheric surface layer of the East Antarctica coastal zone

    Directory of Open Access Journals (Sweden)

    L. P. Golobokova

    2016-01-01

    Full Text Available Chemical composition of aerosol in the ground layer of the coastal zone in East Antarctica is analyzed in the article. The aerosol samples were taken in 2006–2015 during seasonal works of the Russian Antarctic Expeditions (RAE, namely, these were 52nd–53rd, 55th, and 58th–60th expeditions. Samples were taken in the 200‑km band of the sea-shore zone along routes of the research vessels (REV «Akademik Fedorov» and «Akademik Treshnikov» as well as on territories of the Russian stations Molodezhnaya and Mirny. Although the results obtained did show the wide range of the aerosol concentrations and a certain variability of their chemical composition, some common features of the variability were revealed. Thus, during the period from 2006 to 2014 a decrease of average values of the sums were noted. Spatially, a tendency of decreasing of the ion concentrations was found in the direction from the station Novolazarevskaya to the Molodezhnaya one, but the concentrations increased from the Molodezhnaya to the station Mirny. The sum of ions of the aerosol in the above mentioned coastal zone was, on the average, equal to 2.44 μg/m3, and it was larger than that on the territory of the Antarctic stations Molodezhnaya (0,29 μg/m3 and Mirny (0,50 ág / m3. The main part to the sum of the aerosol ions on the Antarctic stations was contributed by Na+, Ca2+, Cl−, SO4 2−. The main ions in aerosol composition in the coastal zone are ions Na+ and Cl−. The dominant contribution of the sea salt and SO4 2− can be traced in not only the composition of atmospheric aerosols, but also in the chemical composition of the fresh snow in the coastal areas of East Antarctica: at the Indian station Maitri, on the Larsemann Hills, and in a boring located in 55.3 km from the station Progress (K = 1.4÷6.1. It was noted that values of the coefficient of enrichment K of these ions decreases as someone moves from a shore to inland. Estimation of

  16. Surface-layer turbulence, energy balance and links to atmospheric circulations over a mountain glacier in the French Alps

    Science.gov (United States)

    Litt, Maxime; Sicart, Jean-Emmanuel; Six, Delphine; Wagnon, Patrick; Helgason, Warren D.

    2017-04-01

    Over Saint-Sorlin Glacier in the French Alps (45° N, 6.1° E; ˜ 3 km2) in summer, we study the atmospheric surface-layer dynamics, turbulent fluxes, their uncertainties and their impact on surface energy balance (SEB) melt estimates. Results are classified with regard to large-scale forcing. We use high-frequency eddy-covariance data and mean air-temperature and wind-speed vertical profiles, collected in 2006 and 2009 in the glacier's atmospheric surface layer. We evaluate the turbulent fluxes with the eddy-covariance (sonic) and the profile method, and random errors and parametric uncertainties are evaluated by including different stability corrections and assuming different values for surface roughness lengths. For weak synoptic forcing, local thermal effects dominate the wind circulation. On the glacier, weak katabatic flows with a wind-speed maximum at low height (2-3 m) are detected 71 % of the time and are generally associated with small turbulent kinetic energy (TKE) and small net turbulent fluxes. Radiative fluxes dominate the SEB. When the large-scale forcing is strong, the wind in the valley aligns with the glacier flow, intense downslope flows are observed, no wind-speed maximum is visible below 5 m, and TKE and net turbulent fluxes are often intense. The net turbulent fluxes contribute significantly to the SEB. The surface-layer turbulence production is probably not at equilibrium with dissipation because of interactions of large-scale orographic disturbances with the flow when the forcing is strong or low-frequency oscillations of the katabatic flow when the forcing is weak. In weak forcing when TKE is low, all turbulent fluxes calculation methods provide similar fluxes. In strong forcing when TKE is large, the choice of roughness lengths impacts strongly the net turbulent fluxes from the profile method fluxes and their uncertainties. However, the uncertainty on the total SEB remains too high with regard to the net observed melt to be able to

  17. SIMULATION OF SUMMER-TIME DIURNAL BACTERIAL DYNAMICS IN THE ATMOSPHERIC SURFACE LAYER

    Science.gov (United States)

    A model was prepared to simulate the observed concentration dynamics of culturable bacteria in the diurnal summer atmosphere at a Willamette River Valley, Oregon location. The meteorological and bacterial mechanisms included in a dynamic null-dimensional model with one-second tim...

  18. The effect of entrainment through atmospheric boundary layer growth on observed and modeled surface ozone in the Colorado Front Range

    Science.gov (United States)

    Kaser, L.; Patton, E. G.; Pfister, G. G.; Weinheimer, A. J.; Montzka, D. D.; Flocke, F.; Thompson, A. M.; Stauffer, R. M.; Halliday, H. S.

    2017-06-01

    Ozone concentrations at the Earth's surface are controlled by meteorological and chemical processes and are a function of advection, entrainment, deposition, and net chemical production/loss. The relative contributions of these processes vary in time and space. Understanding the relative importance of these processes controlling surface ozone concentrations is an essential component for designing effective regulatory strategies. Here we focus on the diurnal cycle of entrainment through atmospheric boundary layer (ABL) growth in the Colorado Front Range. Aircraft soundings and surface observations collected in July/August 2014 during the DISCOVER-AQ/FRAPPÉ (Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality/Front Range Air Pollution and Photochemistry Éxperiment) campaigns and equivalent data simulated by a regional chemical transport model are analyzed. Entrainment through ABL growth is most important in the early morning, fumigating the surface at a rate of 5 ppbv/h. The fumigation effect weakens near noon and changes sign to become a small dilution effect in the afternoon on the order of -1 ppbv/h. The chemical transport model WRF-Chem (Weather Research and Forecasting Model with chemistry) underestimates ozone at all altitudes during this study on the order of 10-15 ppbv. The entrainment through ABL growth is overestimated by the model in the order of 0.6-0.8 ppbv/h. This results from differences in boundary layer growth in the morning and ozone concentration jump across the ABL top in the afternoon. This implicates stronger modeled fumigation in the morning and weaker modeled dilution after 11:00 LT.

  19. A study of the atmospheric surface layer and roughness lengths on the high-altitude tropical Zongo glacier, Bolivia

    Science.gov (United States)

    Sicart, Jean Emmanuel; Litt, Maxime; Helgason, Warren; Tahar, Vanessa Ben; Chaperon, Thomas

    2014-04-01

    The atmospheric surface layer of high-altitude tropical glaciers is inadequately understood, particularly concerning turbulent fluxes. Measurements have shown that sublimation reduces melt energy in the dry season, but the errors are large when a katabatic wind maximum occurs at a low height. This study analyzed wind and temperature vertical profiles measured by a 6 m mast in the ablation area of the tropical Zongo glacier (16°S, 5060 m above sea level) in the dry seasons of 2005 and 2007. Surface roughness lengths for momentum and temperature were derived from least squares fits of hourly wind and temperature profile data. Measurement errors were explored, focusing on the poorly defined reference level for sensor heights. A katabatic wind maximum at heights between 2 and 3 m was regularly observed during low wind speed and strong inversion conditions, or about 50%of the time, greatly reducing the surface layer depth. The glacier surface, experiencing melting conditions in the early afternoon and strong cooling at night, remained relatively smooth with z0 1 mm and zT 0.1 mm. Sensible heat flux measured at 1 m was not very sensitive to the zero reference level due to two opposite effects: when measurement heights increase, profile-derived roughness lengths increase but temperature and wind gradients decrease. The relation between zT/z0 and the roughness Reynolds number Re* roughly agrees with the surface renewal model. However, this is mostly due to self-correlation because of the shared variable z0 in zT/z0 and Re*, which prevents a sound experimental validation of the model.

  20. A multi - layer land surface energy budget model for implicit coupling with global atmospheric simulations

    NARCIS (Netherlands)

    Ryder, J.; Polcher, J.; Peylin, P.; Ottlé, C.; Chen, Y; van Gorsel, E.; Haverd, V.; McGrath, M.J.; Naudts, K.; Otto, J.; Valade, A; Luyssaert, S

    2014-01-01

    See, stats, and : https : / / www . researchgate . net / publication / 276534648 A - layer for simulations Article DOI : 10 . 5194 / gmdd - 7 - 8649 - 2014 CITATIONS 9 READS 155 12 , including : Some : land Master Jan French 193 , 481 SEE Eva Australian 98 , 225 SEE Vanessa The 85 SEE Juliane

  1. Modelling stable atmospheric boundary layers over snow

    NARCIS (Netherlands)

    Sterk, H.A.M.

    2015-01-01

    Thesis entitled: Modelling Stable Atmospheric Boundary Layers over Snow H.A.M. Sterk Wageningen, 29th of April, 2015 Summary The emphasis of this thesis is on the understanding and forecasting of the Stable Boundary Layer (SBL) over snow-covered surfaces. SBLs typically form at night and in polar

  2. The role of atmospheric boundary layer-surface interactions on the development of coastal fronts

    Directory of Open Access Journals (Sweden)

    D. Malda

    2007-03-01

    Full Text Available Frictional convergence and thermal difference between land and sea surface are the two surface conditions that govern the intensity and evolution of a coastal front. By means of the mesoscale model MM5, we investigate the influence of these two processes on wind patterns, temperature and precipitation amounts, associated with a coastal front, observed on the west coast of The Netherlands in the night between 12 and 13 August 2004. The mesoscale model MM5 is further compared with available observations and the results of two operational models (ECMWF and HIRLAM. HIRLAM is not capable to reproduce the coastal front, whereas ECMWF and MM5 both calculate precipitation for the coastal region. The precipitation pattern, calculated by MM5, agrees satisfactorily with the accumulated radar image. The failure of HIRLAM is mainly due to a different stream pattern at the surface and consequently, a different behaviour of the frictional convergence at the coastline.

    The sensitivity analysis of frictional convergence is carried out with the MM5 model, by varying land surface roughness length (z0. For the sensitivity analysis of thermal difference between sea and land surface, we changed the sea surface temperature (SST. Increasing surface roughness implies stronger convergence near the surface and consequently stronger upward motions and intensification of the development of the coastal front. Setting land surface roughness equal to the sea surface roughness means an elimination of frictional convergence and results in a diminishing coastal front structure of the precipitation pattern. The simulation with a high SST produces much precipitation above the sea, but less precipitation in the coastal area above land. A small increment of the SST results in larger precipitation amounts above the sea; above land increments are calculated for areas near the coast. A decrease of the SST shifts the precipitation maxima inland, although the

  3. Integrating surface, entrainment and mesoscale in the Atmospheric Boundary Layer dynamics: a 10-year study in Cabauw (The Netherlands)

    Science.gov (United States)

    Ander Arrillaga, Jon; Bosveld, Fred; Jiménez, Pedro A.; Baltink, Henk K.; Yagüe, Carlos; Hensen, Arjan; van Dinther, Danielle; Frumau, Arnoud; Dudhia, Jimy; Zhao, Wanjun; Vilà-Guerau de Arellano, Jordi

    2017-04-01

    The diurnal evolution of the Atmospheric Boundary Layer (ABL) in Cabauw (Netherlands) is investigated by considering the role of local and non-local forcings. By local, we understand, the surface fluxes that drive the growing of the ABL in addition to the non-local entrained fluxes. We study potential disruptions occurring in spring and particularly in summer driven by the formation of sea-breeze flows in the form of density currents, due to the proximity of both The North Sea and the Ijsselmeer closed sea. Moreover, this interactive system of surface, boundary layer and mesoscale may play a role in the transport of carbon dioxide and its diurnal variability. Our method is based on the analysis of a comprehensive 10-yr observational database (2001-2010), which gives the opportunity to understand the ABL dynamics from a robust perspective. To support the analysis, modelling results obtained from the WRF mesoscale model are available during the entire 10-year period. The model is run every 48 h to maintain it close to the synoptic conditions calculated by the ERA-Interim state. A fine horizontal resolution of 2 km is used, and the vertical levels are set to match the observational ones (2, 10, 20, 40, 80, 140 and 200 m). In order to identify the sea-breeze arrival, we apply a sea-breeze criteria selection algorithm. It is developed and adapted after a sea-breeze observational study in the Cantabrian Coast (Spain) to filter the sea-breeze events occurring in Cabauw, and consequently analyse their impact in the ABL and the surface fluxes. Preliminary results show that this criteria is able to distinguish between the two main wind directions related to the sea breeze in Cabauw. Our finding shows that the sea-breeze days are characterized by a sharp increment of the wind speed and a noticeable increase of the specific humidity at around 16-17 UTC.

  4. Activity of radon (222Rn) in the lower atmospheric surface layer of a ...

    Indian Academy of Sciences (India)

    E) located in a rural site in Gadanki, south India. The dataset was analysed to understand the behaviour of radon in relation to the surface air temperature and relative humidity at a rural site. It was observed that over a period of the 24 hours in a day, the activity of radon and its progenies reaches a peak in the morning.

  5. Effect of Atmospheric Conditions on Coverage of Fogger Applications in a Desert Surface Boundary Layer

    Science.gov (United States)

    2012-01-01

    Although lidar cannot provide aerosol concentrations directly and only scans above vege - tation, Khot et al. (2011) have provided a method to use it to...about 10 m across the plume (fig. 5a). Convection cells moved it up- ward from the ground surface rather quickly in low wind conditions. This

  6. Characterizing the lower log region of the atmospheric surface layer via large-scale particle tracking velocimetry

    Science.gov (United States)

    Rosi, Giuseppe A.; Sherry, Michael; Kinzel, Matthias; Rival, David E.

    2014-05-01

    As a first step toward characterizing coherent structures within the atmospheric surface layer (ASL), measurements obtained via a large-scale particle tracking velocimetry (LS-PTV) system were validated against wind-measurement station data as well as canonical turbulent boundary layer studies. The LS-PTV system resolves three-dimensional, Lagrangian tracks over a 16 m3 volume. Mean-velocity measurements, as well as vertical and shear Reynolds-stress measurements, generally agreed with wind-measurement station data and Reynolds-stress profiles referenced from literature. The probability distributions for streamwise, spanwise and vertical velocity-fluctuation components appear normally distributed about zero. Furthermore, the probability distributions for all three components of Lagrangian acceleration were exponential and followed the parametrization curve from LaPorta et al. (Lett Nat 409:1017-1019, 2001). Lastly, the vorticity probability distributions were exponential and symmetric about zero, which matches findings from Balint et al. (Fluid Mech 228:53-86, 1991). The vorticity intensity measured by the LS-PTV system was less than values from Priyadarshana et al. (Fluid Mech 570:307-346, 2007), which is attributed to the low spatial resolution. However, the average spacing of 0.5 m between tracer particles is deemed sufficient for the future characterization of vortical structures within the ASL.

  7. Modification of surface layers of copper under the action of the volumetric discharge initiated by an avalanche electron beam in nitrogen and CO2 at atmospheric pressure

    Science.gov (United States)

    Shulepov, M. A.; Akhmadeev, Yu. Kh.; Tarasenko, V. F.; Kolubaeva, Yu. A.; Krysina, O. V.; Kostyrya, I. D.

    2011-05-01

    The results of experimental investigations of the action of the volumetric discharge initiated by an avalanche electron beam on the surface of copper specimens are presented. The volumetric (diffuse) discharge in nitrogen and CO2 at atmospheric pressure was initiated by applying high voltage pulses of nanosecond duration to a tubular foil cathode. It has been found that the treatment of a copper surface by this type of discharge increases the hardness of the surface layer due to oxidation.

  8. 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.

  9. Recent Advances in Modeling of the Atmospheric Boundary Layer and Land Surface in the Coupled WRF-CMAQ Model

    Science.gov (United States)

    Advances in the land surface model (LSM) and planetary boundary layer (PBL) components of the WRF-CMAQ coupled meteorology and air quality modeling system are described. The aim of these modifications was primarily to improve the modeling of ground level concentrations of trace c...

  10. Simulation of the evolution of particle size distributions containing coarse particulate in the atmospheric surface layer with a simple convection-diffusion-sedimentation model

    Science.gov (United States)

    Hubbard, J. A.; Haglund, J. S.; Ezekoye, O. A.

    The Fugitive Dust Model (FDM) and Industrial Source Complex (ISC), widely used coarse particulate dispersion models, have been shown inaccurate due to the neglect of vertical variations in atmospheric wind speed and turbulent diffusivity (Vesovic et al., 2001), omission of the gravitational advection velocity, and an underestimation of the ground deposition velocity (Kim and Larson, 2001). A simple, transient two-dimensional convection-diffusion-sedimentation model is proposed to simulate the evolution in particle size distribution of an aerosol 'puff' containing coarse particulate in the atmospheric surface layer. Monin-Okhubov similarity theory, accompanied by empirical observations made by Businger et al. (1971), is adopted to characterize the surface layer wind speed and turbulent diffusivity profiles over a wide range of atmospheric conditions. A first order analysis of the crossing trajectories effect suggests simulation data presented here are not significantly affected by particle inertia. The model is validated against Suffield experimental data in which coarse particulate deposition was measured out to a distance of 800 m from the source (Walker, 1965). Good agreement is found for the decay in ground deposits with distance from the source for stable atmospheres. Deposition data was also simulated for unstable atmospheric stratification and the current model was determined to modestly underestimate the peak concentration with increasing accuracy further downwind of the release. The current model's effective deposition velocity was compared to that suggested by Kim et al. (2000) and shows improvement with respect to FDM. Lastly, the model was used to simulate the dispersion of nine lognormal aerosol puffs in the lowest 50 m of the atmospheric surface layer for four classes of atmospheric stability. The simulated mass median aerodynamic diameters (MMAD) at multiple downwind sampling locations were calculated and plotted with distance from the source. The

  11. The Impact of Land-Surface Parameter Properties and Resolution on the Simulated Cloud-Topped Atmospheric Boundary Layer

    Science.gov (United States)

    Gantner, Leonhard; Maurer, Vera; Kalthoff, Norbert; Kiseleva, Olga

    2017-12-01

    Sensitivity tests using the `Consortium for Small Scale Modeling' model in large-eddy simulation mode with a grid spacing of 100 m are performed to investigate the impact of the resolution of soil- and vegetation-related parameters on a cloud-topped boundary layer in a real-data environment. The reference simulation uses the highest land-surface parameter resolution available for operational purposes (300 m). The sensitivity experiments were conducted using spatial averaging of about 2.5 km× 2.5 km and 10 km × 10 km for the land-surface parameters and a completely homogeneous distribution for the whole model domain of about 70 km × 70 km. Additionally, one experiment with a higher mean soil moisture and another with six mesoscale patches of enhanced or reduced soil moisture are performed. Boundary-layer clouds developed in all simulations. To assess the deviations of cloud cover on different scales within the model domain, we calculated the root-mean-square deviation ( RMSD) between the sensitivity experiments and the reference simulation. The RMSD depends strongly on the spatial resolution at which cloud fields are compared. Different spatial resolutions of the cloud fields were generated by applying a low-pass filter. For all sensitivity experiments, large RMSD values occur for cut-off wavelengths {}5 km, the RMSD is still pronounced for the simulation with higher mean soil moisture. Additionally, for cut-off wavelengths between 5 and 30 km, considerable differences can be found for the experiment with mesoscale patches and for that with homogeneous land-surface parameters. Spatial averaging of land-surface parameters for areas of 2.5 km × 2.5 km and 10 km × 10 km results in larger patch sizes but simultaneously in reduced amplitudes of land-surface parameter anomalies and shows the lowest RMSD for all cut-off wavelengths.

  12. A Lagrangian stochastic model to demonstrate multi-scale interactions between convection and land surface heterogeneity in the atmospheric boundary layer

    Science.gov (United States)

    Parsakhoo, Zahra; Shao, Yaping

    2017-04-01

    Near-surface turbulent mixing has considerable effect on surface fluxes, cloud formation and convection in the atmospheric boundary layer (ABL). Its quantifications is however a modeling and computational challenge since the small eddies are not fully resolved in Eulerian models directly. We have developed a Lagrangian stochastic model to demonstrate multi-scale interactions between convection and land surface heterogeneity in the atmospheric boundary layer based on the Ito Stochastic Differential Equation (SDE) for air parcels (particles). Due to the complexity of the mixing in the ABL, we find that linear Ito SDE cannot represent convections properly. Three strategies have been tested to solve the problem: 1) to make the deterministic term in the Ito equation non-linear; 2) to change the random term in the Ito equation fractional, and 3) to modify the Ito equation by including Levy flights. We focus on the third strategy and interpret mixing as interaction between at least two stochastic processes with different Lagrangian time scales. The model is in progress to include the collisions among the particles with different characteristic and to apply the 3D model for real cases. One application of the model is emphasized: some land surface patterns are generated and then coupled with the Large Eddy Simulation (LES).

  13. Helicity in the atmospheric boundary layer

    Science.gov (United States)

    Kurgansky, Michael; Koprov, Boris; Koprov, Victor; Chkhetiani, Otto

    2017-04-01

    An overview is presented of recent direct field measurements at the Tsimlyansk Scientific Station of A.M. Obukhov Institute of Atmospheric Physics in Moscow of turbulent helicity (and potential vorticity) using four acoustic anemometers positioned, within the atmospheric surface-adjacent boundary layer, in the vertices of a rectangular tetrahedron, with an approximate 5 m distance between the anemometers and a 5.5 m elevation of the tetrahedron base above the ground surface (Koprov, Koprov, Kurgansky and Chkhetiani. Izvestiya, Atmospheric and Oceanic Physics, 2015, Vol.51, 565-575). The same ideology was applied in a later field experiment in Tsimlyansk with the tetrahedron's size of 0.7 m and variable elevation over the ground from 3.5 to 25 m. It is illustrated with examples of the statistical distribution of instantaneous (both positive and negative) turbulent helicity values. A theory is proposed that explains the measured mean turbulent helicity sign, including the sign of contribution to helicity from the horizontal and vertical velocity & vorticity components, respectively, and the sign of helicity buoyant production term. By considering a superposition of the classic Ekman spiral solution and a jet-like wind profile that mimics a shallow breeze circulation over a non-uniformly heated Earth surface, a possible explanation is provided, why the measured mean turbulent helicity sign is negative. The pronounced breeze circulation over the Tsimlyansk polygon which is located nearby the Tsimlyansk Reservoir was, indeed, observed during the measurements period. Whereas, essentially positive helicity is injected into the boundary layer from the free atmosphere in the Northern Hemisphere.

  14. Effects of Initial Drivers and Land Use on WRF Modeling for Near-Surface Fields and Atmospheric Boundary Layer over the Northeastern Tibetan Plateau

    Directory of Open Access Journals (Sweden)

    Junhua Yang

    2016-01-01

    Full Text Available To improve the simulation performance of mesoscale models in the northeastern Tibetan Plateau, two reanalysis initial datasets (NCEP FNL and ERA-Interim and two MODIS (Moderate-Resolution Imaging Spectroradiometer land-use datasets (from 2001 and 2010 are used in WRF (Weather Research and Forecasting modeling. The model can reproduce the variations of 2 m temperature (T2 and 2 m relative humidity (RH2, but T2 is overestimated and RH2 is underestimated in the control experiment. After using the new initial drive and land use data, the simulation precision in T2 is improved by the correction of overestimated net energy flux at surface and the RH2 is improved due to the lower T2 and larger soil moisture. Due to systematic bias in WRF modeling for wind speed, we design another experiment that includes the Jimenez subgrid-scale orography scheme, which reduces the frequency of low wind speed and increases the frequency of high wind speed and that is more consistent with the observation. Meanwhile, the new drive and land-use data lead to lower boundary layer height and influence the potential temperature and wind speed in both the lower atmosphere and the upper layer, while the impact on water vapor mixing ratio is primarily concentrated in the lower atmosphere.

  15. Vertical variations in the turbulent structure of the surface boundary layer over vineyards under unstable atmospheric conditions

    Science.gov (United States)

    Due to their highly-structured canopy, turbulent characteristics within and above vineyards, may not conform to those typically exhibited by other agricultural and natural ecosystems. Using data collected as a part of the Grape Remote sensing and Atmospheric Profiling and Evapotranspiration Experime...

  16. Variability of the Structure Parameters of Temperature and Humidity Observed in the Atmospheric Surface Layer Under Unstable Conditions

    NARCIS (Netherlands)

    Braam, M.; Moene, A.F.; Beyrich, F.

    2014-01-01

    The structure parameters of temperature and humidity are important in scintillometry as they determine the structure parameter of the refractive index of air, the primary atmospheric variable obtained with scintillometers. In this study, we investigate the variability of the logarithm of the

  17. The Atmospheric boundary layer over Arctic fjords

    Energy Technology Data Exchange (ETDEWEB)

    Kilpelaeinen, Tiina

    2011-07-01

    Arctic fjords represent one of the most challenging environments in the world for weather prediction and climate models. This is due to complex interactions between the large-scale weather conditions, land, sea, sea ice and surrounding topography consisting of mountains, valleys and glaciers. This thesis describes some special characteristics of the lowest part of the atmosphere over fjords in Svalbard. The main research topics are 1) the exchange of energy between the atmosphere and sea, 2) vertical structure of temperature, humidity and wind, 3) spatial variability of the meteorological variables and 4) identifying the main challenges for the weather prediction models. Kilpelaeinen has collected data using weather masts and tethered balloons at the coasts of fjords in Svalbard. In addition, she has made high-resolution simulations of the meteorological conditions over Svalbard fjords with a weather prediction model. Kilpelaeinens investigations show that the vertical profiles of temperature, humidity and wind over Arctic fjords are complex and therefore challenging for the weather prediction models to capture. Layers with a temperature and humidity increase with height are commonly found over Svalbard fjords, often even on multiple levels. A weather prediction model does not realistically capture these layers, which leads to fairly large errors in the modeled surface variables. Further, she found that a wind maximum at a low altitude is also a typical feature over Arctic fjords. The height of this wind maximum depends on the sea-ice conditions, being highest when sea ice is present. The thesis points out that due to the complex topography and the surface types (sea ice and water), spatial variability of meteorological variables within a fjord is very large and can reach levels comparable to the temporal variability. Hence, a high horizontal resolution in the order of 1 km is needed in the weather prediction models to realistically simulate all the significant

  18. Prediction of the (137)Cs activity concentration in the atmospheric surface layer of the Chernobyl exclusion zone.

    Science.gov (United States)

    Garger, E K; Kuzmenko, Yu I; Sickinger, S; Tschiersch, J

    2012-08-01

    The time series of the 10-day average (137)Cs volumetric activity concentration in the lower atmosphere measured from 1987 to 1991 in the town of Pripyat, close to the Chernobyl nuclear power plant, was used to construct a model to predict the airborne activity concentration inside the 30-km exclusion zone. For that purpose, individual components of the observed time series were separated by regression analysis and the Group Method of Data Handling. The measured data in Pripyat were divided in two periods. The long-term prediction by the model established using the measured data of the first period, has been validated with the data in the second period with good agreement. The behaviour of the model parameters depending on the length of the periods was also analysed, and the first period of 4.5 y was shown as sufficient for estimating the parameters. Further increase in the length will not significantly enhance the model parameters and the predictive power. Copyright © 2012 Elsevier Ltd. All rights reserved.

  19. Planar time-resolved PIV for velocity and pressure retrieval in atmospheric boundary layer over surface waves.

    Science.gov (United States)

    Troitskaya, Yuliya; Kandaurov, Alexander; Sergeev, Daniil; Bopp, Maximilian; Caulliez, Guillemette

    2017-04-01

    Air-sea coupling in general is important for weather, climate, fluxes. Wind wave source is crucially important for surface waves' modeling. But the wind-wave growth rate is strongly uncertain. Using direct measurements of pressure by wave-following Elliott probe [1] showed, weak and indefinite dependence of wind-wave growth rate on the wave steepness, while Grare et.al. [2] discuss the limitations of direct measurements of pressure associated with the inability to measure the pressure close to the surface by contact methods. Recently non-invasive methods for determining the pressure on the basis of technology of time-resolved PIV are actively developed [3]. Retrieving air flow velocities by 2D PIV techniques was started from Reul et al [4]. The first attempt for retrieving wind pressure field of waves in the laboratory tank from the time-resolved PIV measurements was done in [5]. The experiments were performed at the Large Air-Sea Interaction Facility (LASIF) - MIO/Luminy (length 40 m, cross section of air channel 3.2 x 1.6 m). For 18 regimes with wind speed up to 14 m/s including presence of puddle waves, a combination of time resolved PIV technique and optical measurements of water surface form was applied to detailed investigation of the characteristics of the wind flow over the water surface. Ammonium chloride smoke was used for flow visualization illuminated by two 6 Wt blue diode lasers combined into a vertical laser plane. Particle movement was captured with high-speed camera using Scheimpflug technique (up to 20 kHz frame rate with 4-frame bursts, spatial resolution about 190 μm, field of view 314x12 mm). Velocity air flow field was retrieved by PIV images processing with adaptive cross-correlation method on the curvilinear grid following surface wave form. The resulting time resolved instantaneous velocity fields on regular grid allowed us to obtain momentum fluxes directly from measured air velocity fluctuations. The average wind velocity patterns were

  20. Surface Temperature and Surface-Layer Turbulence in a Convective Boundary Layer

    NARCIS (Netherlands)

    Garai, A.; Pardyjak, E.; Steeneveld, G.J.; Kleissl, J.

    2013-01-01

    Previous laboratory and atmospheric experiments have shown that turbulence influences the surface temperature in a convective boundary layer. The main objective of this study is to examine land-atmosphere coupled heat transport mechanism for different stability conditions. High frequency infrared

  1. Understanding and prediction of stable atmospheric boundary layers over land

    NARCIS (Netherlands)

    Steeneveld, G.J.

    2007-01-01

    The main objective of this thesis is to contribute to further understanding of the stable boundary layer (SBL) over land, and its representation in atmospheric models. A SBL develops during night due to radiative surface cooling. Observations in the SBL are difficult since many different physical

  2. Surface layers of bacteria.

    Science.gov (United States)

    Beveridge, T J; Graham, L L

    1991-12-01

    Since bacteria are so small, microscopy has traditionally been used to study them as individual cells. To this end, electron microscopy has been a most powerful tool for studying bacterial surfaces; the viewing of macromolecular arrangements of some surfaces is now possible. This review compares older conventional electron-microscopic methods with new cryotechniques currently available and the results each has produced. Emphasis is not placed on the methodology but, rather, on the importance of the results in terms of our perception of the makeup and function of bacterial surfaces and their interaction with the surrounding environment.

  3. Surface layers of bacteria.

    OpenAIRE

    Beveridge, T. J.; Graham, L L

    1991-01-01

    Since bacteria are so small, microscopy has traditionally been used to study them as individual cells. To this end, electron microscopy has been a most powerful tool for studying bacterial surfaces; the viewing of macromolecular arrangements of some surfaces is now possible. This review compares older conventional electron-microscopic methods with new cryotechniques currently available and the results each has produced. Emphasis is not placed on the methodology but, rather, on the importance ...

  4. Inhomogeneities in Molecular Layers of Mira Atmospheres

    Science.gov (United States)

    2011-01-01

    Wood10, and A. A. Zijlstra11 1 ESO, Karl- Schwarzschild -Str. 2, 85748 Garching bei München, Germany e-mail: mwittkow@eso.org 2 US Naval Observatory, 3450...with the predictions of the latest dynamic model atmosphere series based on self-excited pulsation models. The wavelength-dependent radius variations...based on self-excited pulsation models. The wavelength-dependent radius variations are interpreted as the effect of molecular layers lying above the

  5. [Surface layers of methanotrophic bacteria].

    Science.gov (United States)

    Khmelenina, V N; Suzina, N E; Trotsenko, Iu A

    2013-01-01

    Structural and functional characteristics of the regular glycoprotein layers in prokaryotes are analyzed with a special emphasis on aerobic methanotrophic bacteria. S-layers are present at the surfaces of Methylococcus, Methylothermus, and Methylomicrobium cells. Different Methylomicrobium species either synthesize S-layers with planar (p2, p4) symmetry or form cup-shaped or conicalstructures with hexagonal (p6) symmetry. A unique, copper-binding polypeptide 'CorA'/MopE (27/45 kDa), which is coexpressed with the diheme periplasmic cytochrome c peroxidase 'CorB'/Mca (80 kDa) was found in Methylomicrobium album BG8, Methylomicrobium alcaliphilum 20Z, and Methylococcus capsulatus Bath. This tandem of the surface proteins is functionally analogous to a new siderophore, methanobactin. Importantly, no 'CorA'/MopE homologue was found in methanotrophs not forming S-layers. The role of surface proteins in copper metabolism and initial methane oxidation is discussed.

  6. Modelling land surface - atmosphere interactions

    DEFF Research Database (Denmark)

    Rasmussen, Søren Højmark

    related to inaccurate land surface modelling, e.g. enhanced warm bias in warm dry summer months. Coupling the regional climate model to a hydrological model shows the potential of improving the surface flux simulations in dry periods and the 2 m air temperature in general. In the dry periods......The study is investigates modelling of land surfaceatmosphere interactions in context of fully coupled climatehydrological model. With a special focus of under what condition a fully coupled model system is needed. Regional climate model inter-comparison projects as ENSEMBLES have shown bias...

  7. Turbulent Characterization of atmospheric surface layer over non-homogeneous terrain; Caracterizacion turbulenta de la capa superficial atmosferica en un terreno no homogeneo

    Energy Technology Data Exchange (ETDEWEB)

    Artinano Rodriguez de Torres, B.

    1989-07-01

    About 15000 wind and temperature profiles from a 100 m tower located in CEDER (Soria, Spain) have been analyzed. Using profiles in close neutral conditions, two main parameters of surface layer were obtained. Results show a great dependence of these parameters (Z{sub 0} roughness length and u friction velocity) on flow conditions and terrain (tinctures. Difficulty finding neutral conditions in this type of terrain (gently rolling and scattered bush) and in this latitude , is also remarkable. (Author) 91 refs.

  8. Exploring Isothermal Layers in the Stable Atmospheric Boundary Layer

    Science.gov (United States)

    Wilkins, Joseph

    2011-03-01

    Simulating the stable atmospheric boundary-layer presents a significant challenge to numerical models due to the interactions of several processes with widely varying scales. The goal of this project is to more clearly define the cause of isothermal layers observed during the Meteorological Experiment in Arizona's Meteor Crater and to test the National Taiwan University/Purdue University (NTU/P) model in stable environments with complex terrain. The NTU/P model is able to utilize the actual terrain data with minimal smoothing for stability. We have found that isothermal profiles can be generated by the standing wave that develops due to weak wind flowing over the crater. However, the horizontal heterogeneity is greater than observed. Continued effort will explore enhancing horizontal mixing due to turbulence and radiative transfer. Louis Stokes Alliances for Minority Participation Program, Summer Research Opportunities Program.

  9. A model for the estimation of the surface fluxes of momentum, heat and moisture of the cloud topped marine atmospheric boundary layer from satellite measurable parameters. M.S. Thesis

    Science.gov (United States)

    Allison, D. E.

    1984-01-01

    A model is developed for the estimation of the surface fluxes of momentum, heat, and moisture of the cloud topped marine atmospheric boundary layer by use of satellite remotely sensed parameters. The parameters chosen for the problem are the integrated liquid water content, q sub li, the integrated water vapor content, q sub vi, the cloud top temperature, and either a measure of the 10 meter neutral wind speed or the friction velocity at the surface. Under the assumption of a horizontally homogeneous, well-mixed boundary layer, the model calculates the equivalent potential temperature and total water profiles of the boundary layer along with the boundary layer height from inputs of q sub li, q sub vi, and cloud top temperature. These values, along with the 10m neutral wind speed or friction velocity and the sea surface temperature are then used to estimate the surface fluxes. The development of a scheme to parameterize the integrated water vapor outside of the boundary layer for the cases of cold air outbreak and California coastal stratus is presented.

  10. Turbulence Scales Simulations in Atmospheric Boundary Layer Wind Tunnels

    OpenAIRE

    Teleman, Elena-Carmen; Silion, Radu; Axinte, Elena; Pescaru, Radu

    2008-01-01

    The simulation of the air flow over models in atmospheric boundary layer tunnels is a research domain based on advanced scientific technologies imposed by the necessity of studying the turbulent fluid movements in the proximity of the Earth’s surface. The experiment presented herein is developed in the wind tunnel from the Laboratory of Structural Aerodynamics of the Faculty of Civil Engineering and Building Services in Iassy. Measurements necessary for the determination of the turbulence sca...

  11. Enhancement of atmospheric radiation by an aerosol layer

    Science.gov (United States)

    Michelangeli, Diane V.; Yung, Yuk L.; Shia, Run-Lie; Eluszkiewicz, Janusz; Allen, Mark; Crisp, David

    1992-01-01

    The presence of a stratospheric haze layer may produce increases in both the actinic flux and the irradiance below this layer. Such haze layers result from the injection of aerosol-forming material into the stratosphere by volcanic eruptions. Simple heuristic arguments show that the increase in flux below the haze layer, relative to a clear sky case, is a consequence of 'photon trapping'. The magnitude of these flux perturbations, as a function of aerosol properties and illumination conditions, is explored with a new radiative transfer model that can accurately compute fluxes in an inhomogeneous atmosphere with nonconservative scatterers having arbitrary phase function. One calculated consequence of the El Chichon volcanic eruption is an increase in the midday surface actinic flux at 20 deg N latitude, summer, by as much as 45 percent at 2900 A. This increase in flux in the UV-B wavelength range was caused entirely by aerosol scattering, without any reduction in the overhead ozone column.

  12. Introduction to the Third GEWEX Atmospheric Boundary Layer Study (GABLS3)

    NARCIS (Netherlands)

    Holtslag, A.A.M.

    2014-01-01

    The atmospheric boundary layer (ABL) plays a dominant role in the exchange of energy, water vapour, trace gases and momentum between the earth’s surface and the overlying atmosphere. Consequently, the ABL is an important part of any numerical model in use for atmospheric and climate research, for

  13. Simulating dynamics of {delta}{sup 13}C of CO{sub 2} in the planetary boundary layer a boreal forest region: covariation between surface fluxes and atmospheric mixing

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Baozhang; Chen, Jing M. [Univ. of Toronto, ON (Canada). Dept. of Geography; Tans, Pieter P. [National Oceanic and Atmospheric Administration, Boulder, CO (United States). Earth System Research Lab.; Huang, Lin [Environment Canada, Toronto, ON (Canada). Atmospheric Science and Technology Directorate

    2006-11-15

    Stable isotopes of CO{sub 2} contain unique information on the biological and physical processes that exchange CO{sub 2} between terrestrial ecosystems and the atmosphere. Ecosystem exchange of carbon isotopes with the atmosphere is correlated diurnally and seasonally with the planetary boundary layer (PBL) dynamics. The strength of this kind of covariation affects the vertical gradient of {delta}{sup 13}C and thus the global {delta}{sup 13}C distribution pattern. We need to understand the various processes involved in transport/diffusion of carbon isotope ratio in the PBL and between the PBL and the biosphere and the troposphere. In this study, we employ a one-dimensional vertical diffusion/transport atmospheric model (VDS), coupled to an ecosystem isotope model (BEPS-EASS) to simulate dynamics of {sup 13}CO{sub 2} in the PBL over a boreal forest region in the vicinity of the Fraserdale (FRD) tower (49 deg 52 min 29.9 sec N, 81 deg 34 min 12.3 sec W) in northern Ontario, Canada. The data from intensive campaigns during the growing season in 1999 at this site are used for model validation in the surface layer. The model performance, overall, is satisfactory in simulating the measured data over the whole course of the growing season. We examine the interaction of the biosphere and the atmosphere through the PBL with respect to {delta}{sup 13}C on diurnal and seasonal scales. The simulated annual mean vertical gradient of {delta}{sup 13}C in the PBL in the vicinity of the FRD tower was about 0.025% in 1999. The {delta}{sup 13}C vertical gradient exhibited strong diurnal (29%) and seasonal (71%) variations that do not exactly mimic those of CO{sub 2}. Most of the vertical gradient (96.5% {+-}) resulted from covariation between ecosystem exchange of carbon isotopes and the PBL dynamics, while the rest (3.5%{+-}) was contributed by isotopic disequilibrium between respiration and photosynthesis. This disequilibrium effect on {delta}{sup 13}C of CO{sub 2} dynamics in PBL

  14. Simulating dynamics of (delta){sup 13}C of CO{sub 2} in the planetary boundary layer a boreal forest region: covariation between surface fluxes and atmospheric mixing

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Baozhang; Chen, Jing M. [Univ. of Toronto, ON (Canada). Dept. of Geography; Tans, Pieter P. [National Oceanic and Atmospheric Administration, Boulder, CO (United States). Earth System Research Lab.; Huang, Lin [Environment Canada, Toronto, ON (Canada). Atmospheric Science and Technology Directorate

    2006-11-15

    Stable isotopes of CO{sub 2} contain unique information on the biological and physical processes that exchange CO{sub 2} between terrestrial ecosystems and the atmosphere. Ecosystem exchange of carbon isotopes with the atmosphere is correlated diurnally and seasonally with the planetary boundary layer (PBL) dynamics. The strength of this kind of covariation affects the vertical gradient of (delta){sup 13}C and thus the global (delta){sup 13}C distribution pattern. We need to understand the various processes involved in transport/diffusion of carbon isotope ratio in the PBL and between the PBL and the biosphere and the troposphere. In this study, we employ a one-dimensional vertical diffusion/transport atmospheric model (VDS), coupled to an ecosystem isotope model (BEPS-EASS) to simulate dynamics of {sup 13}CO{sub 2} in the PBL over a boreal forest region in the vicinity of the Fraserdale (FRD) tower (49 deg 52 min 29.9 sec N, 81 deg 34 min 12.3 sec W) in northern Ontario, Canada. The data from intensive campaigns during the growing season in 1999 at this site are used for model validation in the surface layer. The model performance, overall, is satisfactory in simulating the measured data over the whole course of the growing season. We examine the interaction of the biosphere and the atmosphere through the PBL with respect to (delta){sup 13}C on diurnal and seasonal scales. The simulated annual mean vertical gradient of (delta){sup 13}C in the PBL in the vicinity of the FRD tower was about 0.025% in 1999. The (delta){sup 13}C vertical gradient exhibited strong diurnal (29%) and seasonal (71%) variations that do not exactly mimic those of CO{sub 2}. Most of the vertical gradient (96.5% {+-}) resulted from covariation between ecosystem exchange of carbon isotopes and the PBL dynamics, while the rest (3.5%{+-}) was contributed by isotopic disequilibrium between respiration and photosynthesis. This disequilibrium effect on (delta){sup 13}C of CO{sub 2} dynamics in PBL

  15. Comparison of slant-path scintillometry, sonic anemometry and high-speed videography for vertical profiling of turbulence in the atmospheric surface layer

    CSIR Research Space (South Africa)

    Griffith, DJ

    2013-09-01

    Full Text Available services for the Rietvlei campaign were provided by the Advanced Fire Information System (AFIS8). REFERENCES [1] Weiss-Wrana, K. and Balfour, L. S., “Statistical analysis of measurements of atmospheric turbulence in different climates,” Optics...

  16. Atmosphere-surface interactions over polar oceans and heterogeneous surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Vihma, T.

    1995-12-31

    Processes of interaction between the atmospheric boundary layer and the planetary surface have been studied with special emphasis on polar ocean surfaces: the open ocean, leads, polynyas and sea ice. The local exchange of momentum, heat and moisture has been studied experimentally both in the Weddell Sea and in the Greenland Sea. Exchange processes over heterogeneous surfaces are addressed by modelling studies. Over a homogeneous surface, the local turbulent fluxes can be reasonably well estimated using an iterative flux-profile scheme based on the Monin-Obukhov similarity theory. In the Greenland Sea, the near-surface air temperature and the generally small turbulent fluxes over the open ocean were affected by the sea surface temperature fronts. Over the sea ice cover in the Weddell Sea, the turbulent sensible heat flux was generally downwards, and together with an upward oceanic heat flux through the ice it compensated the heat loss from the surface via long-wave radiation. The wind dominated on time scales of days, while the current became important on longer time scales. The drift dynamics showed apparent spatial differences between the eastern and western regions, as well as between the Antarctic Circumpolar Current and the rest of the Weddell Sea. Inertial motion was present in regions of low ice concentration. The surface heterogeneity, arising e.g. from roughness or temperature distribution, poses a problem for the parameterization of surface exchange processes in large-scale models. In the case of neutral flow over a heterogeneous terrain, an effective roughness length can be used to parameterize the roughness effects

  17. Atmospheric boundary layers in storms: advanced theory and modelling applications

    Directory of Open Access Journals (Sweden)

    S. S. Zilitinkevich

    2005-01-01

    Full Text Available Turbulent planetary boundary layers (PBLs control the exchange processes between the atmosphere and the ocean/land. The key problems of PBL physics are to determine the PBL height, the momentum, energy and matter fluxes at the surface and the mean wind and scalar profiles throughout the layer in a range of regimes from stable and neutral to convective. Until present, the PBLs typical of stormy weather were always considered as neutrally stratified. Recent works have disclosed that such PBLs are in fact very strongly affected by the static stability of the free atmosphere and must be treated as factually stable (we call this type of the PBL "conventionally neutral" in contract to the "truly neutral" PBLs developed against the neutrally stratified free flow. It is common knowledge that basic features of PBLs exhibit a noticeable dependence on the free-flow static stability and baroclinicity. However, the concern of the traditional theory of neural and stable PBLs was almost without exception the barotropic nocturnal PBL, which develops at mid latitudes during a few hours in the night, on the background of a neutral or slightly stable residual layer. The latter separates this type of the PBL from the free atmosphere. It is not surprising that the nature of turbulence in such regimes is basically local and does not depend on the properties of the free atmosphere. Alternatively, long-lived neutral (in fact only conditionally neutral or stable PBLs, which have much more time to grow up, are placed immediately below the stably stratified free flow. Under these conditions, the turbulent transports of momentum and scalars even in the surface layer - far away from the PBL outer boundary - depend on the free-flow Brunt-Väisälä frequency, N. Furthermore, integral measures of the long-lived PBLs (their depths and the resistance law functions depend on N and also on the baroclinic shear, S. In the traditional PBL models both non-local parameters N and S

  18. Ultrasound enhanced plasma surface modification at atmospheric pressure

    DEFF Research Database (Denmark)

    Kusano, Yukihiro; Singh, Shailendra Vikram; Norrman, Kion

    2012-01-01

    Efficiency of atmospheric pressure plasma treatment can be highly enhanced by simultaneous high power ultrasonic irradiation onto the treating surface. It is because ultrasonic waves with a sound pressure level (SPL) above ∼140 dB can reduce the thickness of a boundary gas layer between the plasm...

  19. Coherence of simulated atmospheric boundary-layer turbulence

    Science.gov (United States)

    Jiadong, Zeng; Zhiguo, Li; Mingshui, Li

    2017-12-01

    The coherences in a plane perpendicular to incoming flow are measured in wind tunnel simulations of atmospheric turbulent flow. The measured coherences are compared with analytical expressions tailored to field measurements and with theoretical coherence models which assume homogeneous turbulence and the von Kármán’s spectrum. The comparison indicates that the simulated atmospheric boundary layer flow is approximately horizontally homogeneous turbulence. Based on the above assumption and the systematic analysis of lateral coherence, it can be concluded that the lateral coherences of simulated atmospheric boundary turbulence can be determined accurately using the von Kármán spectrum and the turbulence parameters measured by a few measurement points. The measured results also show that the spatial characteristics of vertical coherences are closely related to the dimensionless parameter {{Δ }}z/({\\bar{z}}0.3{L}ux 0.7). The vertical coherence at two heights can be roughly estimated by the ratio to {{Δ }}z/({\\bar{z}}0.3{L}ux 0.7). The relationship between the phase angles of u-, v- and w-components and the vertical separation distance and the height from the ground is further analyzed. Finally, the roles of the type of land surface roughness, the height from the ground, the turbulence intensity and the integral length scale in lateral and vertical coherences are also discussed in this study.

  20. Investigation of optical turbulence in the atmospheric surface layer using scintillometer measurements along a slant path and comparison to ultrasonic anemometer measurements

    CSIR Research Space (South Africa)

    Sprung, D

    2014-09-01

    Full Text Available and Industrial Research (CSIR) P O Box 395, Pretoria 0001, South Africa dgriffith@csir.co.za ABSTRACT Optical turbulence represented by the structure function parameter of the refractive index Cn 2 is a relevant parameter for the performance... of these time series Cn 2 was derived. Three instruments were mounted at a portable mast in the center of slant path measurements over a horizontal distance of 1000 m using large aperture scintillometers (Boundary layer scintillometer BLS 900). Averaging over...

  1. Modelling the Arctic Stable boundary layer and its coupling to the surface

    NARCIS (Netherlands)

    Steeneveld, G.J.; Wiel, van de B.J.H.; Holtslag, A.A.M.

    2006-01-01

    The impact of coupling the atmosphere to the surface energy balance is examined for the stable boundary layer, as an extension of the first GABLS (GEWEX Atmospheric Boundary-Layer Study) one-dimensional model intercomparison. This coupling is of major importance for the stable boundary-layer

  2. Turbulence Scales Simulations in Atmospheric Boundary Layer Wind Tunnels

    Directory of Open Access Journals (Sweden)

    Elena-Carmen Teleman

    2008-01-01

    Full Text Available The simulation of the air flow over models in atmospheric boundary layer tunnels is a research domain based on advanced scientific technologies imposed by the necessity of studying the turbulent fluid movements in the proximity of the Earth’s surface. The experiment presented herein is developed in the wind tunnel from the Laboratory of Structural Aerodynamics of the Faculty of Civil Engineering and Building Services in Iassy. Measurements necessary for the determination of the turbulence scales of the wind action in urban environment were conducted. The data obtained were processed and analyzed and interpreted with specific software. The results are used for a synthesis regarding the scales of turbulence of the model of flow and the actual accuracy of measurements. The paper presents some of the important elements of this synthesis.

  3. The turning of the wind in the atmospheric boundary layer

    DEFF Research Database (Denmark)

    Pena Diaz, Alfredo; Gryning, Sven-Erik; Floors, Rogier Ralph

    2014-01-01

    Here we use accurate observations of the wind speed vector to analyze the behavior with height of the wind direction. The observations are a combination of tall meteorological mast and long-range wind lidar measurements covering the entire atmospheric boundary layer. The observations were performed...... winds underpredict the turning of the wind and the boundary-layer winds in general....

  4. Impact of Land Surface Heterogeneity on Mesoscale Atmospheric Dispersion

    Science.gov (United States)

    Wu, Yuling; Nair, Udaysankar S.; Pielke, Roger A., Sr.; McNider, Richard T.; Christopher, Sundar A.; Anantharaj, Valentine G.

    2009-01-01

    Prior numerical modelling studies show that atmospheric dispersion is sensitive to surface heterogeneities, but past studies do not consider the impact of a realistic distribution of surface heterogeneities on mesoscale atmospheric dispersion. While these focussed on dispersion in the convective boundary layer, the present work also considers dispersion in the nocturnal boundary layer and above. Using a Lagrangian particle dispersion model (LPDM) coupled to the Eulerian Regional Atmospheric Modeling System (RAMS), the impact of topographic, vegetation, and soil moisture heterogeneities on daytime and nighttime atmospheric dispersion is examined. In addition, the sensitivity to the use of Moderate Resolution Imaging Spectroradiometer (MODIS)-derived spatial distributions of vegetation characteristics on atmospheric dispersion is also studied. The impact of vegetation and terrain heterogeneities on atmospheric dispersion is strongly modulated by soil moisture, with the nature of dispersion switching from non-Gaussian to near- Gaussian behaviour for wetter soils (fraction of saturation soil moisture content exceeding 40%). For drier soil moisture conditions, vegetation heterogeneity produces differential heating and the formation of mesoscale circulation patterns that are primarily responsible for non-Gaussian dispersion patterns. Nighttime dispersion is very sensitive to topographic, vegetation, soil moisture, and soil type heterogeneity and is distinctly non-Gaussian for heterogeneous land-surface conditions. Sensitivity studies show that soil type and vegetation heterogeneities have the most dramatic impact on atmospheric dispersion. To provide more skillful dispersion calculations, we recommend the utilisation of satellite-derived vegetation characteristics coupled with data assimilation techniques that constrain soil-vegetation-atmosphere transfer (SVAT) models to generate realistic spatial distributions of surface energy fluxes.

  5. Effects of stratification on an ocean surface Ekman layer

    Science.gov (United States)

    Pham, Hieu; Sarkar, Sutanu

    2014-11-01

    Large-eddy simulations are used to investigate the effects of stratification on structural and turbulent dynamics of an upper-ocean Ekman layer that is driven by a constant wind stress (friction velocity u*) at low latitude with Coriolis parameter f. The surface layer evolves in the presence of interior stratification whose buoyancy frequency varies among cases, taking three values: N / f = 19 , 60 and 192. At quasi-steady state, a stratified turbulent Ekman layer forms with a surface current veering to the right of the wind direction. The thickness of the Ekman layer decreases with increasing N and is found to scale with u*, f, and N, similar to the neutral atmospheric boundary layer of Zilitinkevich & Esau (2002) that is capped by a stratified layer with buoyancy frequency, N. As N increases, the speed of the Ekman current increases but the Ekman transport is invariant. The surface veering angle also increases with larger N. The shear rate and buoyancy frequency are elevated at the base of the Ekman layer. The peak of down-wind Reynolds stress occurs near the surface and scales with u*2 in all cases while the peak of cross-wind Reynolds stress occurs in the middle of the Ekman layer and decreases with increasing N.

  6. Model castings with composite surface layer - application

    Directory of Open Access Journals (Sweden)

    J. Szajnar

    2008-10-01

    Full Text Available The paper presents a method of usable properties of surface layers improvement of cast carbon steel 200–450, by put directly in foundingprocess a composite surface layer on the basis of Fe-Cr-C alloy. Technology of composite surface layer guarantee mainly increase inhardness and aberasive wear resistance of cast steel castings on machine elements. This technology can be competition for generallyapplied welding technology (surfacing by welding and thermal spraying. In range of studies was made cast steel test castings withcomposite surface layer, which usability for industrial applications was estimated by criterion of hardness and aberasive wear resistance of type metal-mineral and quality of joint cast steel – (Fe-Cr-C. Based on conducted studies a thesis, that composite surface layer arise from liquid state, was formulated. Moreover, possible is control of composite layer thickness and its hardness by suitable selection of parameters i.e. thickness of insert, pouring temperature and solidification modulus of casting. Possibility of technology application of composite surface layer in manufacture of cast steel slide bush for combined cutter loader is presented.

  7. Atmospheric pressure plasma for surface modification

    CERN Document Server

    Wolf, Rory A

    2012-01-01

    This Book's focus and intent is to impart an understanding of the practical application of atmospheric plasma for the advancement of a wide range of current and emerging technologies. The primary key feature of this book is the introduction of over thirteen years of practical experimental evidence of successful surface modifications by atmospheric plasma methods. It offers a handbook-based approach for leveraging and optimizing atmospheric plasma technologies which are currently in commercial use. It also offers a complete treatment of both basic plasma physics and industrial plasma process

  8. Lower Atmospheric Boundary Layer Experiment (LABLE) Final Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Klein, P [University of Oklahoma - School of Meteorology; Bonin, TA; Newman, JF [National Renewable Energy Laboratory; Turner, DD [National Oceanic and Atmospheric Administration; Chilson, P [University of Oklahoma; Blumberg, WG [University of Oklahoma; Mishra, S; Wainwright, CE; Carney, M [University of Oklahoma - School of Meteorology; Jacobsen, EP [University of Oklahoma; Wharton, S [Lawrence Livermore National Laboratory

    2015-11-01

    The Lower Atmospheric Boundary Layer Experiment (LABLE) included two measurement campaigns conducted at the Atmospheric Radiation Measurement (ARM) Southern Great Plains site in Oklahoma during 2012 and 2013. LABLE was designed as a multi-phase, low-cost collaboration among the University of Oklahoma, the National Severe Storms Laboratory, Lawrence Livermore National Laboratory, and the ARM program. A unique aspect was the role of graduate students in LABLE. They served as principal investigators and took the lead in designing and conducting experiments using different sampling strategies to best resolve boundary-layer phenomena.

  9. Simulation of Wind turbines in the atmospheric boundary layer

    DEFF Research Database (Denmark)

    Chivaee, Hamid Sarlak; Sørensen, Jens Nørkær; Mikkelsen, Robert Flemming

    Large eddy simulation of an arbitrary wind farm is studied in the neutral and thermally stratified atmospheric boundary Layer. Large eddy simulations of industrial flows usually requires full resolution of the flow near the wall and this is believed to be one of the main deficiencies of LES because...... layer. In the current study, another approach has been implemented to simulate the flow in a fully developed wind farm boundary layer. The approach is based on Immersed Boundary Method and involves implementation of an arbitrary prescribed initial boundary layer. An initial boundary layer is enforced...... through the whole domain, without wind turbines included, while the body forces that are required to maintain that flow field is calculated. The body forces are then stored and applied on the domain through the simulation of wind turbine and the boundary layer shape will be modified based on the turbine...

  10. Laser beam propagation through an atmospheric transitional and turbulent boundary layer

    Science.gov (United States)

    Katz, Richard A.; Manzur, Tariq

    2015-05-01

    This study investigates laser beam propagation through an atmospheric boundary layer near the ocean surface. Objectives of this research are to ascertain feasibility limits for achieving maximum energy efficiency at extended ranges in the face of atmospheric and other distortions as the laser beam penetrates through transitional (anisotropic) and turbulent (isotropic) boundary layer regimes. Various aspects of turbulence modeling of laser beam propagation near the ocean surface are discussed including: Kolmogorov's model of atmospheric turbulence, parameterized structure functions (e.g., velocity and temperature gradients, gradients in refractive index) and other important factors affecting near surface propagation such as humidity, aerosols, and wave slap. Various preliminary modeled propagation results are shown, and a new methodology is proposed for improving existing model estimates with new time domain measurement procedures.

  11. On the marine atmospheric boundary layer characteristics over Bay ...

    Indian Academy of Sciences (India)

    Detailed measurements were carried out in the Marine Atmospheric Boundary Layer (MABL) during the Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB) which covered both Arabian Sea and Bay of Bengal during March to May 2006. In this paper, we present the meteorological observations made ...

  12. Atmospheric boundary layer evening transitions over West Texas

    Science.gov (United States)

    A systemic analysis of the atmospheric boundary layer behavior during some evening transitions over West Texas was done using the data from an extensive array of instruments which included small and large aperture scintillometers, net radiometers, and meteorological stations. The analysis also comp...

  13. Characterization of the atmospheric boundary layer from radiosonde ...

    Indian Academy of Sciences (India)

    Abstract. In this paper, a comparison of two methods for the calculation of the height of atmospheric boundary layer (ABL), using balloon-borne GPS radiosonde data is presented. ABL has been characterized using vertical profiles of meteorological parameter. The gradient of virtual potential temperature (v) profile for the ...

  14. Spatial atmospheric atomic layer deposition of alxzn1-xo

    NARCIS (Netherlands)

    Illiberi, A.; Scherpenborg, R.; Wu, Y.; Roozeboom, F.; Poodt, P.

    2013-01-01

    The possibility of growing multicomponent oxides by spatial atmospheric atomic layer deposition has been investigated. To this end, Al xZn1-xO films have been deposited using diethyl zinc (DEZ), trimethyl aluminum (TMA), and water as Zn, Al, and O precursors, respectively. When the metal precursors

  15. Numerical model of a non-steady atmospheric planetary boundary layer, based on similarity theory

    DEFF Research Database (Denmark)

    Zilitinkevich, S.S.; Fedorovich, E.E.; Shabalova, M.V.

    1992-01-01

    A numerical model of a non-stationary atmospheric planetary boundary layer (PBL) over a horizontally homogeneous flat surface is derived on the basis of similarity theory. The two most typical turbulence regimes are reproduced: one corresponding to a convectively growing PBL and another correspon...

  16. Surface-layer gusts for aircraft operation

    DEFF Research Database (Denmark)

    Young, G.S.; Kristensen, L.

    1992-01-01

    We use Monin-Obukhov similarity theory to extend the Kristensen et al. (1991) aviation gust estimation technique from the neutral to the diabatic surface layer. Example calculations demonstrate the importance of this correction. Simple stability class methods using only standard aviation surface...

  17. Surface wave effects on long range IR imaging in the marine surface layer

    Science.gov (United States)

    Francius, M. J.; Kunz, G. J.; van Eijk, A. M. J.

    2005-08-01

    The quality of long range infrared (IR) imaging depends on the effects of atmospheric refraction and other pathintegrated effects (e.g., transmission losses, scintillation and blurring), which are strongly related to the prevailing meteorological conditions. EOSTAR is a PC based computer program to quantify these strong nonlinear effects in the marine atmospheric surface layer and to present a spectrally resolved target image influenced by atmospheric effects using ray tracing techniques for the individual camera pixels. Presently, the propagation is predicted with bulk atmospheric models and the sea surface is idealized by steady regular periodic Stokes' waves. Dynamical wind-waves interactions are not taken into account in this approach, although they may strongly modify the refractive index in the near-surface layer. Nonetheless, the inclusion of the sea surface in the ray tracer module already has a great impact on the near-surface grazing rays and thus influences the images especially in situations of super refraction and mirage. This work aims at improving the description of the sea surface in EOSTAR taking into account the non-uniformity of spatially resolved wind-generated waves and swell. A new surface module is developed to model surface wind-waves and swell in EOSTAR on the basis of meteorological observations and spectral wave modeling. Effects due to these new surfaces will be analyzed and presented.

  18. Surface modification of polyethylene films using atmospheric ...

    African Journals Online (AJOL)

    An atmospheric-pressure plasma jet (APPJ) is used to increase the wettability of polyethylene polymer films. Reduction in contact angle from 94.32 to 58.33 degrees was measured for treatment times of 1 - 5 seconds. Contact angle reductions of PE as a function of treatment time with APPJ and PE surface at various oxygen ...

  19. Surface Modification of Polyethylene Films using Atmospheric

    African Journals Online (AJOL)

    Dr A.B.Ahmed

    ABSTRACT. An atmospheric-pressure plasma jet (APPJ) is used to increase the wettability of polyethylene polymer films. Reduction in contact angle from 94.32 to 58.33 degrees was measured for treatment times of 1 - 5 seconds. Contact angle reductions of PE as a function of treatment time with APPJ and PE surface at ...

  20. The Temporal Behavior of the Atmospheric Boundary Layer in Israel.

    Science.gov (United States)

    Dayan, Uri; Rodnizki, Jacob

    1999-06-01

    Upper-air measurements collected for three consecutive years (1987-89) from the Israel Meteorological Service permanent sounding site, in Beit-Dagan, Israel, enabled the temporal behavior of the atmospheric boundary layer over Israel to be characterized. Data analyzed consisted of the layer depth, the thermal gradient within the layer, and occurrence frequency of radiative and elevated inversions. To adequately represent the multiyear seasonal and diurnal behavior, the 3-yr databases were merged based on the tested hypothesis that the month sample in each individual year comes from the same population. The analysis shows that the depth of the radiative ground-based inversion, its frequency, as well as its thermal profile are maximal during spring and early summer. The upper-inversion layer is well defined during the summer, its lowest base (0.5-1 km MSL) indicating a sharp interface layer formed between the marine turbulent boundary layer at the shallow layer of the atmosphere and the subsiding downward motion caused by the subtropical high pressure system. During the other three seasons a significant temporal variation of the upper-inversion base is observed as a result of the frequent larger-scale synoptic weather systems. The diurnal variation of the mixed-layer depth is most evident during the summer because it is mainly governed by heat fluxes and the daily sea-breeze cycle that are most intensive then. Henceforth, the layer minimal depth, along the coast, usually occurs during late afternoon hours when the wind speed of the cool sea breeze reaches its minimal rate and heat fluxes dissipate rapidly, leading to a decrease of the marine turbulent boundary layer.

  1. A model study of mixing and entrainment in the horizontally evolving atmospheric convective boundary layer

    Energy Technology Data Exchange (ETDEWEB)

    Fedorovich, E.; Kaiser, R. [Univ. Karlsruhe, Inst. fuer Hydrologie und Wasserwirtschaft (Germany)

    1997-10-01

    We present results from a parallel wind-tunnel/large-eddy simulation (LES) model study of mixing and entrainment in the atmospheric convective boundary layer (CBL) longitudinally developing over a heated surface. The advection-type entrainment of warmer air from upper turbulence-free layers into the growing CBL has been investigated. Most of numerical and laboratory model studies of the CBL carried out so far dealt with another type of entrainment, namely the non-steady one, regarding the CBL growth as a non-stationary process. In the atmosphere, both types of the CBL development can take place, often being superimposed. (au)

  2. Fiber optic distributed temperature sensing for the determination of the nocturnal atmospheric boundary layer height

    Directory of Open Access Journals (Sweden)

    C. A. Keller

    2011-02-01

    Full Text Available A new method for measuring air temperature profiles in the atmospheric boundary layer at high spatial and temporal resolution is presented. The measurements are based on Raman scattering distributed temperature sensing (DTS with a fiber optic cable attached to a tethered balloon. These data were used to estimate the height of the stable nocturnal boundary layer. The experiment was successfully deployed during a two-day campaign in September 2009, providing evidence that DTS is well suited for this atmospheric application. Observed stable temperature profiles exhibit an exponential shape confirming similarity concepts of the temperature inversion close to the surface. The atmospheric mixing height (MH was estimated to vary between 5 m and 50 m as a result of the nocturnal boundary layer evolution. This value is in good agreement with the MH derived from concurrent Radon-222 (222Rn measurements and in previous studies.

  3. Black carbon solar absorption suppresses turbulence in the atmospheric boundary layer.

    Science.gov (United States)

    Wilcox, Eric M; Thomas, Rick M; Praveen, Puppala S; Pistone, Kristina; Bender, Frida A-M; Ramanathan, Veerabhadran

    2016-10-18

    The introduction of cloud condensation nuclei and radiative heating by sunlight-absorbing aerosols can modify the thickness and coverage of low clouds, yielding significant radiative forcing of climate. The magnitude and sign of changes in cloud coverage and depth in response to changing aerosols are impacted by turbulent dynamics of the cloudy atmosphere, but integrated measurements of aerosol solar absorption and turbulent fluxes have not been reported thus far. Here we report such integrated measurements made from unmanned aerial vehicles (UAVs) during the CARDEX (Cloud Aerosol Radiative Forcing and Dynamics Experiment) investigation conducted over the northern Indian Ocean. The UAV and surface data reveal a reduction in turbulent kinetic energy in the surface mixed layer at the base of the atmosphere concurrent with an increase in absorbing black carbon aerosols. Polluted conditions coincide with a warmer and shallower surface mixed layer because of aerosol radiative heating and reduced turbulence. The polluted surface mixed layer was also observed to be more humid with higher relative humidity. Greater humidity enhances cloud development, as evidenced by polluted clouds that penetrate higher above the top of the surface mixed layer. Reduced entrainment of dry air into the surface layer from above the inversion capping the surface mixed layer, due to weaker turbulence, may contribute to higher relative humidity in the surface layer during polluted conditions. Measurements of turbulence are important for studies of aerosol effects on clouds. Moreover, reduced turbulence can exacerbate both the human health impacts of high concentrations of fine particles and conditions favorable for low-visibility fog events.

  4. Tracking atmospheric boundary layer dynamics with water vapor D-excess observations

    KAUST Repository

    Parkes, Stephen

    2015-04-01

    Stable isotope water vapor observations present a history of hydrological processes that have impacted on an air mass. Consequently, there is scope to improve our knowledge of how different processes impact on humidity budgets by determining the isotopic end members of these processes and combining them with in-situ water vapor measurements. These in-situ datasets are still rare and cover a limited geographical expanse, so expanding the available data can improve our ability to define isotopic end members and knowledge about atmospheric humidity dynamics. Using data collected from an intensive field campaign across a semi-arid grassland site in eastern Australia, we combine multiple methods including in-situ stable isotope observations to study humidity dynamics associated with the growth and decay of the atmospheric boundary layer and the stable nocturnal boundary layer. The deuterium-excess (D-excess) in water vapor is traditionally thought to reflect the sea surface temperature and relative humidity at the point of evaporation over the oceans. However, a number of recent studies suggest that land-atmosphere interactions are also important in setting the D-excess of water vapor. These studies have shown a highly robust diurnal cycle for the D-excess over a range of sites that could be exploited to better understand variations in atmospheric humidity associated with boundary layer dynamics. In this study we use surface radon concentrations as a tracer of surface layer dynamics and combine these with the D-excess observations. The radon concentrations showed an overall trend that was inversely proportional to the D-excess, with early morning entrainment of air from the residual layer of the previous day both diluting the radon concentration and increasing the D-excess, followed by accumulation of radon at the surface and a decrease in the D-excess as the stable nocturnal layer developed in the late afternoon and early evening. The stable nocturnal boundary layer

  5. Temporal Dynamics of Bacterial and Fungal Community Composition in the Atmospheric Boundary Layer

    Science.gov (United States)

    Emerson, J. B.; Perring, A. E.; Schwarz, J. P.; Fahey, D. W.; Fierer, N.

    2014-12-01

    There is increasing evidence for significant microbial influences on atmospheric chemistry, cloud condensation, and ice nuclei concentrations, with known health impacts, yet we have a limited understanding of the types, abundances, and spatiotemporal dynamics of bacteria and fungi in the atmosphere. Here we use culture-independent molecular approaches, including targeted gene sequencing and quantitative PCR, to characterize bacterial and fungal community composition and abundance in the atmospheric boundary layer. We present results from 32 air samples, collected via vacuum filtration at 10 m and 250 m on the Boulder Atmospheric Observatory tower (Erie, CO) between November 2013 and April 2014. Samples were collected at night, and each sample was integrated over consecutive nights for approximately two weeks. Significant temporal shifts in bacterial and fungal community composition were observed over the course of the study, corresponding to changing bacterial and fungal concentrations. Within the same sampling time periods, bacterial and fungal communities from the near-surface atmosphere (10 m) were generally similar to those aloft (250 m), although coupled temporal and altitudinal effects were observed in some cases, particularly for fungi. Overall, our results indicate that bacterial and fungal communities exhibit minimal vertical stratification throughout the nocturnal atmospheric boundary layer but show a high degree of variability on two-week timescales. This study paves the way for further research into the connections between boundary layer microbiology, atmospheric dynamics, emissions, and local meteorology.

  6. Lidar-Observed Stress Vectors and Veer in the Atmospheric Boundary Layer

    DEFF Research Database (Denmark)

    Berg, Jacob; Mann, Jakob; Patton, Edward G.

    2013-01-01

    This study demonstrates that a pulsed wind lidar is a reliable instrument for measuring angles between horizontal vectors of significance in the atmospheric boundary layer. Three different angles are considered: the wind turning, the angle between the stress vector and the mean wind direction......, and the angle between the stress vector and the vertical gradient of the mean velocity vector. The latter is assumed to be zero by the often applied turbulent-viscosity hypothesis, so that the stress vector can be described through the vertical gradient of velocity. In the atmospheric surface layer, where...... the Coriolis force is negligible, this is supposedly a good approximation. High-resolution large-eddy simulation data show that this is indeed the case even beyond the surface layer. In contrast, through analysis of WindCube lidar measurements supported by sonic measurements, the study shows that it is only...

  7. Impacts of Cosmic Dust on Planetary Atmospheres and Surfaces

    Science.gov (United States)

    Plane, John M. C.; Flynn, George J.; Määttänen, Anni; Moores, John E.; Poppe, Andrew R.; Carrillo-Sanchez, Juan Diego; Listowski, Constantino

    2018-02-01

    Recent advances in interplanetary dust modelling provide much improved estimates of the fluxes of cosmic dust particles into planetary (and lunar) atmospheres throughout the solar system. Combining the dust particle size and velocity distributions with new chemical ablation models enables the injection rates of individual elements to be predicted as a function of location and time. This information is essential for understanding a variety of atmospheric impacts, including: the formation of layers of metal atoms and ions; meteoric smoke particles and ice cloud nucleation; perturbations to atmospheric gas-phase chemistry; and the effects of the surface deposition of micrometeorites and cosmic spherules. There is discussion of impacts on all the planets, as well as on Pluto, Triton and Titan.

  8. Ionic Surface Active Compounds in Atmospheric Aerosols

    Directory of Open Access Journals (Sweden)

    Jariya Sukhapan

    2002-01-01

    Full Text Available Surfactants in the atmosphere have several potential roles in atmospheric chemistry. They can form films on aqueous surfaces, which lowers the surface tension and possibly delays water evaporation and gaseous transportation across the aqueous interface. They can also increase the solubility of organic compounds in the aqueous phase. Recently, the decrease of surface tension in cloud growing droplets has been suggested as relevant to increases in the number of droplets of smaller size, potentially enhancing cloud albedo. Natural surfactants in the lung aid gas transfer and influence the dissolution rate of aerosol particles, so surfactants in atmospheric aerosols, once inhaled, may interact with pulmonary surfactants. Ambient aerosols were collected from the edge of Norwich, a small city in a largely agricultural region of England, and analysed for surfactants. Methylene blue, a conventional dye for detecting anionic surfactants, has been used as a colorimetric agent. The concentration of surfactants expressed as methylene blue active substances (MBAS is in the range of 6–170 pmol m-3(air. A negative correlation with chloride aerosol indicates that these surfactants are probably not the well-known surfactants derived from marine spray. A more positive correlation with aerosol nitrate and gaseous NOx supports an association with more polluted inland air masses. The surfactants found in aerosols seem to be relatively strong acids, compared with weaker acids such as the long-chain carboxylic acids previously proposed as atmospheric surfactants. Surfactants from the oxidation of organic materials (perhaps vegetation- or soil-derived seem a likely source of these substances in the atmosphere.

  9. Surface shear rheology of saponin adsorption layers.

    Science.gov (United States)

    Golemanov, Konstantin; Tcholakova, Slavka; Denkov, Nikolai; Pelan, Edward; Stoyanov, Simeon D

    2012-08-21

    Saponins are a wide class of natural surfactants, with molecules containing a rigid hydrophobic group (triterpenoid or steroid), connected via glycoside bonds to hydrophilic oligosaccharide chains. These surfactants are very good foam stabiliziers and emulsifiers, and show a range of nontrivial biological activities. The molecular mechanisms behind these unusual properties are unknown, and, therefore, the saponins have attracted significant research interest in recent years. In our previous study (Stanimirova et al. Langmuir 2011, 27, 12486-12498), we showed that the triterpenoid saponins extracted from Quillaja saponaria plant (Quillaja saponins) formed adsorption layers with unusually high surface dilatational elasticity, 280 ± 30 mN/m. In this Article, we study the shear rheological properties of the adsorption layers of Quillaja saponins. In addition, we study the surface shear rheological properties of Yucca saponins, which are of steroid type. The experimental results show that the adsorption layers of Yucca saponins exhibit purely viscous rheological response, even at the lowest shear stress applied, whereas the adsorption layers of Quillaja saponins behave like a viscoelastic two-dimensional body. For Quillaja saponins, a single master curve describes the data for the viscoelastic creep compliance versus deformation time, up to a certain critical value of the applied shear stress. Above this value, the layer compliance increases, and the adsorption layers eventually transform into viscous ones. The experimental creep-recovery curves for the viscoelastic layers are fitted very well by compound Voigt rheological model. The obtained results are discussed from the viewpoint of the layer structure and the possible molecular mechanisms, governing the rheological response of the saponin adsorption layers.

  10. Large eddy simulation of atmospheric boundary layer over wind farms using a prescribed boundary layer approach

    Science.gov (United States)

    Sarlak, H.; Sørensen, J. N.; Mikkelsen, R.

    2012-09-01

    Large eddy simulation (LES) of flow in a wind farm is studied in neutral as well as thermally stratified atmospheric boundary layer (ABL). An approach has been practiced to simulate the flow in a fully developed wind farm boundary layer. The approach is based on the Immersed Boundary Method (IBM) and involves implementation of an arbitrary prescribed initial boundary layer (See [1]). A prescribed initial boundary layer profile is enforced through the computational domain using body forces to maintain a desired flow field. The body forces are then stored and applied on the domain through the simulation and the boundary layer shape will be modified due to the interaction of the turbine wakes and buoyancy contributions. The implemented method is capable of capturing the most important features of wakes of wind farms [1] while having the advantage of resolving the wall layer with a coarser grid than typically required for such problems.

  11. Large eddy simulation of atmospheric boundary layer over wind farms using a prescribed boundary layer approach

    DEFF Research Database (Denmark)

    Chivaee, Hamid Sarlak; Sørensen, Jens Nørkær; Mikkelsen, Robert Flemming

    2012-01-01

    Large eddy simulation (LES) of flow in a wind farm is studied in neutral as well as thermally stratified atmospheric boundary layer (ABL). An approach has been practiced to simulate the flow in a fully developed wind farm boundary layer. The approach is based on the Immersed Boundary Method (IBM......) and involves implementation of an arbitrary prescribed initial boundary layer (See [1]). A prescribed initial boundary layer profile is enforced through the computational domain using body forces to maintain a desired flow field. The body forces are then stored and applied on the domain through the simulation...... and the boundary layer shape will be modified due to the interaction of the turbine wakes and buoyancy contributions. The implemented method is capable of capturing the most important features of wakes of wind farms [1] while having the advantage of resolving the wall layer with a coarser grid than typically...

  12. Measurement Science of the Intermittent Atmospheric Boundary Layer

    Science.gov (United States)

    2014-01-01

    investigate intermittency fluxes of clear-air radar reflectivity inthe atmospheric boundary layer, 2013 IEEE International Symposium on Antennas and...meridionally by 40 m), eight ultrasonic anemometers, two low-response thermometers, two low-response hygrometers, three quartz-crystal barometers, and...vertically spaced sonics can be used for post-facto calibration (Muschinski and Ayvazian, 2014) of relative biases in a pair of ultrasonic

  13. Surface state and normal layer effects

    Energy Technology Data Exchange (ETDEWEB)

    Klemm, R.A.; Ledvij, M. [Argonne National Lab., IL (United States); Liu, S.H. [Univ. of California, San Diego, CA (United States). Dept. of Physics

    1995-08-01

    In addition to the conducting CuO{sub 2} (S) layers, most high-T{sub c} superconductors also contain other conducting (N) layers, which are only superconducting due to the proximity effect. The combination of S and N layers can give rise to complicated electronic densities of states, leading to quasilinear penetration depth and NMR relaxation rate behavior at low temperatures. Surface states can also complicate the analysis of tunneling and, photoemission measurements. Moreover, geometrical considerations and in homogeneously trapped flux axe possible explanations of the paramagnetic Meissner effect and of corner and ring SQUID experiments. Hence, all of the above experiments could be consistent with isotropic s-wave superconductivity within the S layers.

  14. The collapse of turbulence in the atmospheric boundary layer

    Energy Technology Data Exchange (ETDEWEB)

    Van de Wiel, B J H; Clercx, H J H [Department of Physics, Eindhoven University of Technology (Netherlands); Moene, A F [Department of Meteorology and Air Quality, Wageningen University and Research Centre (Netherlands); Jonker, H J J, E-mail: b.j.h.v.d.wiel@tue.nl [Department of Multi-scale Pysics, Delft University of Technology (Netherlands)

    2011-12-22

    A well-known phenomenon in the atmospheric boundary layer is the fact that winds may become very weak in the evening after a clear sunny day. In these quiet conditions usually hardly any turbulence is present. Consequently this type of boundary layer is referred to as the quasi-laminar boundary layer. In spite of its relevance, the appearance of laminar boundary layers is poorly understood and forms a long standing problem in meteorological research. Here we investigate an analogue problem in the form of a stably stratified channel flow. The flow is studied with a simplified atmospheric model as well as with Direct Numerical Simulations. Both models show remarkably similar behaviour with respect to the mean variables such as temperature and wind speed. The similarity between both models opens new way for understanding and predicting the laminarization process. Mathematical analysis on the simplified model shows that relaminarization can be understood from the existence of a definite limit in the maximum sustainable heat flux under stably stratified conditions. This fascinating aspect will be elaborated in future work.

  15. On the Structure and Adjustment of Inversion-Capped Neutral Atmospheric Boundary-Layer Flows: Large-Eddy Simulation Study

    DEFF Research Database (Denmark)

    Pedersen, Jesper Grønnegaard; Gryning, Sven-Erik; Kelly, Mark C.

    2014-01-01

    A range of large-eddy simulations, with differing free atmosphere stratification and zero or slightly positive surface heat flux, is investigated to improve understanding of the neutral and near-neutral, inversion-capped, horizontally homogeneous, barotropic atmospheric boundary layer with emphas...

  16. Electronic structure of bacterial surface protein layers

    Science.gov (United States)

    Maslyuk, Volodymyr V.; Mertig, Ingrid; Bredow, Thomas; Mertig, Michael; Vyalikh, Denis V.; Molodtsov, Serguei L.

    2008-01-01

    We report an approach for the calculation of the electronic density of states of the dried two-dimensional crystalline surface protein layer ( S layer) of the bacterium Bacillus sphaericus NCTC 9602. The proposed model is based on the consideration of individual amino acids in the corresponding conformation of the peptide chain which additively contribute to the electronic structure of the entire protein complex. The derived results agree well with the experimental data obtained by means of photoemission (PE), resonant PE, and near-edge x-ray absorption spectroscopy.

  17. Surface Morphology of Fe(III)-Porphyrin Thin Layers as Characterized by Atomic Force Microscopy

    OpenAIRE

    Utari Utari; Kusumandari Kusumandari; Budi Purnama; Mudasir Mudasir; Kamsul Abraha

    2016-01-01

    Surface morphology of Fe(III)–porphyrin thin layers was studied using atomic force microscopy. The thin layer samples used in these experiments were deposited by spin coating methods on indium–tin-oxide substrates at room temperature under atmospheric conditions. Variations of thin layer of Fe(III)-porphyrin were done by modifying the rotational speed and the concentration of the solution. The experimental results demonstrated that the Fe(III)–porphyrin layers were observed as discrete nanomo...

  18. Dynamic air layer on textured superhydrophobic surfaces

    KAUST Repository

    Vakarelski, Ivan Uriev

    2013-09-03

    We provide an experimental demonstration that a novel macroscopic, dynamic continuous air layer or plastron can be sustained indefinitely on textured superhydrophobic surfaces in air-supersaturated water by a natural gas influx mechanism. This type of plastron is an intermediate state between Leidenfrost vapor layers on superheated surfaces and the equilibrium Cassie-Baxter wetting state on textured superhydrophobic surfaces. We show that such a plastron can be sustained on the surface of a centimeter-sized superhydrophobic sphere immersed in heated water and variations of its dynamic behavior with air saturation of the water can be regulated by rapid changes of the water temperature. The simple experimental setup allows for quantification of the air flux into the plastron and identification of the air transport model of the plastron growth. Both the observed growth dynamics of such plastrons and millimeter-sized air bubbles seeded on the hydrophilic surface under identical air-supersaturated solution conditions are consistent with the predictions of a well-mixed gas transport model. © 2013 American Chemical Society.

  19. A Diagnostic Diagram to Understand the Marine Atmospheric Boundary Layer at High Wind Speeds

    Science.gov (United States)

    Kettle, Anthony

    2014-05-01

    Long time series of offshore meteorological measurements in the lower marine atmospheric boundary layer show dynamical regimes and variability that are forced partly by interaction with the underlying sea surface and partly by the passage of cloud systems overhead. At low wind speeds, the dynamics and stability structure of the surface layer depend mainly on the air-sea temperature difference and the measured wind speed at a standard height. The physical processes are mostly understood and the quantified through Monin-Obukhov (MO) similarity theory. At high wind speeds different dynamical regimes become dominant. Breaking waves contribute to the atmospheric loading of sea spray and water vapor and modify the character of air-sea interaction. Downdrafts and boundary layer rolls associated with clouds at the top of the boundary layer impact vertical heat and momentum fluxes. Data from offshore meteorological monitoring sites will typically show different behavior and the regime shifts depending on the local winds and synoptic conditions. However, the regular methods to interpret time series through spectral analysis give only a partial view of dynamics in the atmospheric boundary layer. Also, the spectral methods have limited use for boundary layer and mesoscale modellers whose geophysical diagnostics are mostly anchored in directly measurable quantities: wind speed, temperature, precipitation, pressure, and radiation. Of these, wind speed and the air-sea temperature difference are the most important factors that characterize the dynamics of the lower atmospheric boundary layer and they provide a dynamical and thermodynamic constraint to frame observed processes, especially at high wind speeds. This was recognized in the early interpretation of the Froya database of gale force coastal winds from mid-Norway (Andersen, O.J. and J. Lovseth, Gale force maritime wind. The Froya data base. Part 1: Sites and instrumentation. Review of the data base, Journal of Wind

  20. Layer-by-layer assembly of thin organic films on PTFE activated by cold atmospheric plasma

    Directory of Open Access Journals (Sweden)

    Tóth András

    2014-12-01

    Full Text Available An air diffuse coplanar surface barrier discharge is used to activate the surface of polytetrafluoroethylene (PTFE samples, which are subsequently coated with polyvinylpyrrolidone (PVP and tannic acid (TAN single, bi- and multilayers, respectively, using the dip-coating method. The surfaces are characterized by X-ray Photoelectron Spectroscopy (XPS, Attenuated Total Reflection – Fourier Transform Infrared Spectroscopy (ATR-FTIR and Atomic Force Microscopy (AFM. The XPS measurements show that with plasma treatment the F/C atomic ratio in the PTFE surface decreases, due to the diminution of the concentration of CF2 moieties, and also oxygen incorporation through formation of new C–O, C=O and O=C–O bonds can be observed. In the case of coated samples, the new bonds indicated by XPS show the bonding between the organic layer and the surface, and thus the stability of layers, while the gradual decrease of the concentration of F atoms with the number of deposited layers proves the creation of PVP/TAN bi- and multi-layers. According to the ATR-FTIR spectra, in the case of PVP/TAN multilayer hydrogen bonding develops between the PVP and TAN, which assures the stability of the multilayer. The AFM lateral friction measurements show that the macromolecular layers homogeneously coat the plasma treated PTFE surface.

  1. Evaluating Langmuir turbulence parameterizations in the ocean surface boundary layer

    Science.gov (United States)

    Sutherland, G.; Christensen, K. H.; Ward, B.

    2014-03-01

    It is expected that surface gravity waves play an important role in the dynamics of the ocean surface boundary layer (OSBL), quantified with the turbulent Langmuir number (La=u*/us0, where u* and us0 are the friction velocity and surface Stokes drift, respectively). However, simultaneous measurements of the OSBL dynamics along with accurate measurements of the wave and atmospheric forcing are lacking. Measurements of the turbulent dissipation rate ɛ were collected using the Air-Sea Interaction Profiler (ASIP), a freely rising microstructure profiler. Two definitions for the OSBL depth are used: the mixed layer derived from measurements of density >(hρ>), and the mixing layer >(hɛ>) determined from direct measurements of ɛ. When surface buoyancy forces are relatively small, ɛ∝La-2 only near the surface with no dependency on La at mid-depths of the OSBL when using hρ as the turbulent length scale. However, if hɛ is used then the dependence of ɛ with La-2 is more uniform throughout the OSBL. For relatively high destabilizing surface buoyancy forces, ɛ is proportional to the ratio of the OSBL depth against the Langmuir stability length LL. During destabilizing conditions, the mixed and mixing layer depths are nearly identical, but we have relatively few measurements under these conditions, rather than any physical implications. Observations of epsilon are compared with the OSBL regime diagram of Belcher et al. (2012) and are generally within an order of magnitude, but there is an improved agreement if hɛ is used as the turbulent length scale rather than hρ.

  2. The influence of wind speed on surface layer stability and turbulent ...

    Indian Academy of Sciences (India)

    We found that the surface layer stability derived from the Monin–Obukhov length scale, is well depicted by the magnitude of wind speed, i.e., the atmospheric boundary layer was under unstable regime for wind speeds greater than 4 m s−1; under stable regime for wind speeds less than 2 m s−1 and under neutral regime for ...

  3. Model Simulations of the Arctic Atmospheric Boundary Layer from the SHEBA Year

    Energy Technology Data Exchange (ETDEWEB)

    Tjernstroem, Michael; Zagar, Mark; Svensson, Gunilla [Stockholm Univ. (Sweden). Dept. of Meteorology

    2004-06-01

    We present Arctic atmospheric boundary-layer modeling with a regional model COAMPSTM, for the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment. Model results are compared to soundings, near-surface measurements and forecasts from the ECMWF model. The near-surface temperature is often too high in winter, except in shorter periods when the boundary layer was cloud-capped and well-mixed due to cloud-top cooling. Temperatures are slightly too high also during the summer melt season. Effects are too high boundary-layer moisture and formation of too dense stratocumulus, generating a too deep well-mixed boundary layer with a cold bias at the simulated boundary-layer top. Errors in temperature and therefore moisture are responsible for large errors in heat flux, in particular in solar radiation, by forming these clouds. We conclude that the main problems lie in the surface energy balance and the treatment of the heat conduction through the ice and snow and in how low-level clouds are treated.

  4. Optimized Estimation of Surface Layer Characteristics from Profiling Measurements

    Directory of Open Access Journals (Sweden)

    Doreene Kang

    2016-01-01

    Full Text Available New sampling techniques such as tethered-balloon-based measurements or small unmanned aerial vehicles are capable of providing multiple profiles of the Marine Atmospheric Surface Layer (MASL in a short time period. It is desirable to obtain surface fluxes from these measurements, especially when direct flux measurements are difficult to obtain. The profiling data is different from the traditional mean profiles obtained at two or more fixed levels in the surface layer from which surface fluxes of momentum, sensible heat, and latent heat are derived based on Monin-Obukhov Similarity Theory (MOST. This research develops an improved method to derive surface fluxes and the corresponding MASL mean profiles of wind, temperature, and humidity with a least-squares optimization method using the profiling measurements. This approach allows the use of all available independent data. We use a weighted cost function based on the framework of MOST with the cost being optimized using a quasi-Newton method. This approach was applied to seven sets of data collected from the Monterey Bay. The derived fluxes and mean profiles show reasonable results. An empirical bias analysis is conducted using 1000 synthetic datasets to evaluate the robustness of the method.

  5. Identification of a surface layer structure and analysis of humidity ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    2Atmospheric Science Research Group, Physics Department, Jadavpur University, Kolkata 700 032, India. ∗e-mail: deutpal@hotmail.com. The Monsoon Trough Boundary Layer Experiment held in 1990 was a multi-institutional effort to probe the atmospheric boundary layer over the monsoon trough over northern India.

  6. Electronic Structure of Regular Bacterial Surface Layers

    Science.gov (United States)

    Vyalikh, Denis V.; Danzenbächer, Steffen; Mertig, Michael; Kirchner, Alexander; Pompe, Wolfgang; Dedkov, Yuriy S.; Molodtsov, Serguei L.

    2004-12-01

    We report photoemission and near-edge x-ray absorption fine structure measurements of the occupied and unoccupied valence electronic states of the regular surface layer of Bacillus sphaericus, which is widely used as the protein template for the fabrication of metallic nanostructures. The two-dimensional protein crystal shows a semiconductorlike behavior with a gap value of ˜3.0 eV and the Fermi energy close to the bottom of the lowest unoccupied molecular orbital. We anticipate that these results will open up new possibilities for the electric addressability of biotemplated low-dimensional hybrid structures.

  7. Surface Properties of PEMFC Gas Diffusion Layers

    Energy Technology Data Exchange (ETDEWEB)

    WoodIII, David L [Los Alamos National Laboratory (LANL); Rulison, Christopher [Augustine Scientific; Borup, Rodney [Los Alamos National Laboratory (LANL)

    2010-01-01

    The wetting properties of PEMFC Gas Diffusion Layers (GDLs) were quantified by surface characterization measurements and modeling of material properties. Single-fiber contact-angle and surface energy (both Zisman and Owens-Wendt) data of a wide spectrum of GDL types is presented to delineate the effects of hydrophobic post-processing treatments. Modeling of the basic sessile-drop contact angle demonstrates that this value only gives a fraction of the total picture of interfacial wetting physics. Polar forces are shown to contribute 10-20 less than dispersive forces to the composite wetting of GDLs. Internal water contact angles obtained from Owens-Wendt analysis were measured at 13-19 higher than their single-fiber counterparts. An inverse relationship was found between internal contact angle and both Owens-Wendt surface energy and % polarity of the GDL. The most sophisticated PEMFC mathematical models use either experimentally measured capillary pressures or the standard Young-Laplace capillary-pressure equation. Based on the results of the Owens-Wendt analysis, an advancement to the Young-Laplace equation is proposed for use in these mathematical models, which utilizes only solid surface energies and fractional surface coverage of fluoropolymer. Capillary constants for the spectrum of analyzed GDLs are presented for the same purpose.

  8. The atmospheric boundary layer response to the dynamic new Arctic Ocean

    Science.gov (United States)

    Wu, D. L.; Ganeshan, M.

    2016-12-01

    The increasing ice-free area in the Arctic Ocean has transformed its climate system to one with more dynamic boundary layer clouds and seasonal sea ice. During the fall freeze season, the surface sensible heat flux (SSHF) is a crucial mechanism for the loss of excessive ocean heat to the atmosphere, and it has been speculated to play an important role in the recent cloud cover increase and boundary layer (BL) instability observed in the Beaufort and Chukchi seas. Based on multi-year Japanese cruise ship observations from the ice-strengthened R/V Mirai, we are able to characterize the late summer and early fall ocean-BL interactions in this region. Although the BL is found to be well-mixed more than 90% of the time, the SSHF can explain only 10% of the mixed layer height variability. It is the cloud-generated convective turbulence that apparently dominates BL mixing in this ice-free region, which is similar to previous in-situ observations (SHEBA, ASCOS) over sea ice. The SSHF, however, may contribute to BL instability during conditions of uplift (low-pressure), and the presence of the highly stable stratus cloud regime. The efficiency of sensible heat exchange is low during cold air advection (associated with the stratocumulus cloud regime) despite an enhanced ocean-atmosphere temperature difference (ΔT). In general, surface-generated mixing is favored during episodes of high surface wind speeds as opposed to pronounced ΔT. Our analysis suggests a weak local response of the boundary layer stability to the loss of sea ice cover during late summer, which is masked by the strong influence of the large-scale circulation (and clouds). Apart from the fall season, we also studied the Arctic Ocean BL properties during the cold months (Nov-Apr) using multi-year satellite measurements (COSMIC RO). As the boundary layer is typically stable at this time, one might expect major differences in the nature of surface-atmosphere coupling compared to that observed during late

  9. Preface: GEWEX Atmospheric Boundary-layer Study (GABLS) on Stable Boundary Layers

    NARCIS (Netherlands)

    Holtslag, A.A.M.

    2006-01-01

    The Global Energy and Water Cycle Experiment (GEWEX) is a program initiated by the World Climate Research Programme (WCRP) to observe, understand and model the hydrological cycle and the related energy fluxes in the atmosphere, at the land surface and in the upper oceans. Consequently the

  10. Sulfur processing in the marine atmospheric boundary layer: A review and critical assessment of modeling uncertainties

    Science.gov (United States)

    Faloona, Ian

    Sulfur is an extremely motile and vital element in the Earth's biogeochemical environment, one whose active redox chemistry maintains small reservoirs in the atmosphere and biosphere yet large fluxes through both. Essential for life, intimately linked to the climate state, and an important component of air quality, sulfur and its transport and processing in the atmosphere have been the subject of active research for several decades. This review article describes the current state of our understanding of the atmospheric sulfur cycle, focusing on the marine atmospheric boundary layer, with the aim of identifying the largest roots of uncertainty that most inhibit accurate simulation of sulfur cycling in the atmosphere. An overview of the emissions by phytoplankton and shipping, dispersion and entrainment in the marine boundary layer, and chemical processing by aerosols, clouds, and dry deposition is presented. Analysis of 20 contemporary modeling studies suggests that the greatest ambiguity in global sulfur cycling derives from (in descending order) wet deposition of aerosol sulfate, dry deposition of sulfur dioxide to the Earth's surface, and the heterogeneous oxidation of SO 2 in aerosols and clouds.

  11. Determination of regional surface heat fluxes over heterogeneous landscapes by integrating satellite remote sensing with boundary layer observations

    NARCIS (Netherlands)

    Ma, Y.M.

    2006-01-01

    Keywords: satellite remote sensing, surface layer observations, atmospheric boundary layer observations, land surface variables, vegetation variables, land surface heat fluxes, validation, heterogeneous landscape,

  12. Determination of regional surface heat fluxes over heterogeneous landscapes by integrating satellite remote sensing with boundary layer observations

    NARCIS (Netherlands)

    Ma, Y.M.

    2006-01-01

    Keywords: satellite remote sensing, surface layer observations, atmospheric boundary layer observations, land surface variables, vegetation variables, land surface heat fluxes, validation, heterogeneous landscape,

  13. On the parametrization of the planetary boundary layer of the atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Yordanov, D. [Bulgarian Academy of Sciences, Geophysical Inst., Sofia (Bulgaria); Syrakov, D.; Kolarova, M. [Bulgarian Academy of Sciences, National Inst. of Meteorology and Hydrology, Sofia (United Kingdom)

    1997-10-01

    The investigation of the dynamic processes in the planetary boundary layer presents a definite theoretical challenge and plays a growing role for the solution of a number of practical tasks. The improvement of large-scale atmospheric weather forecast depends, to a certain degree, on the proper inclusion of the planetary boundary layer dynamics in the numerical models. The modeling of the transport and the diffusion of air pollutants is connected with estimation of the different processes in the Planetary Boundary Layer (PBL) and needs also a proper PBL parametrization. For the solution of these practical tasks the following PBL models;(i) a baroclinic PBL model with its barotropic version, and (ii) a convective PBL model were developed. Both models are one dimensional and are based on the similarity theory and the resistance lows extended for the whole PBL. Two different PBL parametrizations under stable and under convective conditions are proposed, on the basis of which the turbulent surface heat and momentum fluxes are estimated using generalized similarity theory. By the proposed parametrizations the internal parameters are calculated from the synoptic scale parameters as geostrophyc wind, potential temperature and humidity given at two levels (ground level and at 850 hPa) and from them - the PBL profiles. The models consists of two layers: a surface layer (SL) with a variable height and a second (Ekman layer) over it with a constant with height turbulent exchange coefficient. (au) 14 refs.

  14. A land surface scheme for atmospheric and hydrologic models: SEWAB (Surface Energy and Water Balance)

    Energy Technology Data Exchange (ETDEWEB)

    Mengelkamp, H.T.; Warrach, K.; Raschke, E. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Atmosphaerenphysik

    1997-12-31

    A soil-vegetation-atmosphere-transfer scheme is presented here which solves the coupled system of the Surface Energy and Water Balance (SEWAB) equations considering partly vegetated surfaces. It is based on the one-layer concept for vegetation. In the soil the diffusion equations for heat and moisture are solved on a multi-layer grid. SEWAB has been developed to serve as a land-surface scheme for atmospheric circulation models. Being forced with atmospheric data from either simulations or measurements it calculates surface and subsurface runoff that can serve as input to hydrologic models. The model has been validated with field data from the FIFE experiment and has participated in the PILPS project for intercomparison of land-surface parameterization schemes. From these experiments we feel that SEWAB reasonably well partitions the radiation and precipitation into sensible and latent heat fluxes as well as into runoff and soil moisture Storage. (orig.) [Deutsch] Ein Landoberflaechenschema wird vorgestellt, das den Transport von Waerme und Wasser zwischen dem Erdboden, der Vegetation und der Atmosphaere unter Beruecksichtigung von teilweise bewachsenem Boden beschreibt. Im Erdboden werden die Diffusionsgleichungen fuer Waerme und Feuchte auf einem Gitter mit mehreren Schichten geloest. Das Schema SEWAB (Surface Energy and Water Balance) beschreibt die Landoberflaechenprozesse in atmosphaerischen Modellen und berechnet den Oberflaechenabfluss und den Basisabfluss, die als Eingabedaten fuer hydrologische Modelle genutzt werden koennen. Das Modell wurde mit Daten des FIFE-Experiments kalibriert und hat an Vergleichsexperimenten fuer Landoberflaechen-Schemata im Rahmen des PILPS-Projektes teilgenommen. Dabei hat sich gezeigt, dass die Aufteilung der einfallenden Strahlung und des Niederschlages in den sensiblen und latenten Waermefluss und auch in Abfluss und Speicherung der Bodenfeuchte in SEWAB den beobachteten Daten recht gut entspricht. (orig.)

  15. Organic light emitting diode with surface modification layer

    Energy Technology Data Exchange (ETDEWEB)

    Basil, John D.; Bhandari, Abhinav; Buhay, Harry; Arbab, Mehran; Marietti, Gary J.

    2017-09-12

    An organic light emitting diode (10) includes a substrate (12) having a first surface (14) and a second surface (16), a first electrode (32), and a second electrode (38). An emissive layer (36) is located between the first electrode (32) and the second electrode (38). The organic light emitting diode (10) further includes a surface modification layer (18). The surface modification layer (18) includes a non-planar surface (30, 52).

  16. X-ray lattice strain determination in surface layers

    DEFF Research Database (Denmark)

    Somers, Marcel A.J.; Pantleon, Karen

    2002-01-01

    The present article describes several aspects of lattice strain determination in surface layers by means of X-ray diffraction analysis. Several possibilities and the origins of stress in surface layers are illustrated by the following three cases: 200 nm thick Mo layers on glass substrates; 5.......5 microns thick TiN layers on heat treatable steel and 21 microns thick gamma prime-Fe4N1-x layers on iron....

  17. Carbides composite surface layers produced by (PTA)

    Energy Technology Data Exchange (ETDEWEB)

    Tajoure, Meloud, E-mail: Tajoore2000@yahoo.com [MechanicalEng.,HIHM,Gharian (Libya); Tajouri, Ali, E-mail: Tajouri-am@yahoo.com, E-mail: dr.mokhtarphd@yahoo.com; Abuzriba, Mokhtar, E-mail: Tajouri-am@yahoo.com, E-mail: dr.mokhtarphd@yahoo.com [Materials and Metallurgical Eng., UOT, Tripoli (Libya); Akreem, Mosbah, E-mail: makreem@yahoo.com [Industrial Research Centre,Tripoli (Libya)

    2013-12-16

    The plasma transferred arc technique was applied to deposit a composite layer of nickel base with tungsten carbide in powder form on to surface of low alloy steel 18G2A type according to polish standard. Results showed that, plasma transferred arc hard facing process was successfully conducted by using Deloro alloy 22 plus tungsten carbide powders. Maximum hardness of 1489 HV and minimum dilution of 8.4 % were achieved by using an arc current of 60 A. However, when the current was further increased to 120 A and the dilution increases with current increase while the hardness decreases. Microstructure of the nickel base deposit with tungsten carbide features uniform distribution of reinforcement particles with regular grain shape half - dissolved in the matrix.

  18. Impact of the Diurnal Cycle of the Atmospheric Boundary Layer on Wind-Turbine Wakes: A Numerical Modelling Study

    Science.gov (United States)

    Englberger, Antonia; Dörnbrack, Andreas

    2017-10-01

    The wake characteristics of a wind turbine for different regimes occurring throughout the diurnal cycle are investigated systematically by means of large-eddy simulation. Idealized diurnal cycle simulations of the atmospheric boundary layer are performed with the geophysical flow solver EULAG over both homogeneous and heterogeneous terrain. Under homogeneous conditions, the diurnal cycle significantly affects the low-level wind shear and atmospheric turbulence. A strong vertical wind shear and veering with height occur in the nocturnal stable boundary layer and in the morning boundary layer, whereas atmospheric turbulence is much larger in the convective boundary layer and in the evening boundary layer. The increased shear under heterogeneous conditions changes these wind characteristics, counteracting the formation of the night-time Ekman spiral. The convective, stable, evening, and morning regimes of the atmospheric boundary layer over a homogeneous surface as well as the convective and stable regimes over a heterogeneous surface are used to study the flow in a wind-turbine wake. Synchronized turbulent inflow data from the idealized atmospheric boundary-layer simulations with periodic horizontal boundary conditions are applied to the wind-turbine simulations with open streamwise boundary conditions. The resulting wake is strongly influenced by the stability of the atmosphere. In both cases, the flow in the wake recovers more rapidly under convective conditions during the day than under stable conditions at night. The simulated wakes produced for the night-time situation completely differ between heterogeneous and homogeneous surface conditions. The wake characteristics of the transitional periods are influenced by the flow regime prior to the transition. Furthermore, there are different wake deflections over the height of the rotor, which reflect the incoming wind direction.

  19. Intercomparison of Martian Lower Atmosphere Simulated Using Different Planetary Boundary Layer Parameterization Schemes

    Science.gov (United States)

    Natarajan, Murali; Fairlie, T. Duncan; Dwyer Cianciolo, Alicia; Smith, Michael D.

    2015-01-01

    We use the mesoscale modeling capability of Mars Weather Research and Forecasting (MarsWRF) model to study the sensitivity of the simulated Martian lower atmosphere to differences in the parameterization of the planetary boundary layer (PBL). Characterization of the Martian atmosphere and realistic representation of processes such as mixing of tracers like dust depend on how well the model reproduces the evolution of the PBL structure. MarsWRF is based on the NCAR WRF model and it retains some of the PBL schemes available in the earth version. Published studies have examined the performance of different PBL schemes in NCAR WRF with the help of observations. Currently such assessments are not feasible for Martian atmospheric models due to lack of observations. It is of interest though to study the sensitivity of the model to PBL parameterization. Typically, for standard Martian atmospheric simulations, we have used the Medium Range Forecast (MRF) PBL scheme, which considers a correction term to the vertical gradients to incorporate nonlocal effects. For this study, we have also used two other parameterizations, a non-local closure scheme called Yonsei University (YSU) PBL scheme and a turbulent kinetic energy closure scheme called Mellor- Yamada-Janjic (MYJ) PBL scheme. We will present intercomparisons of the near surface temperature profiles, boundary layer heights, and wind obtained from the different simulations. We plan to use available temperature observations from Mini TES instrument onboard the rovers Spirit and Opportunity in evaluating the model results.

  20. Laboratory modelling of the transfer processes between the ocean and atmosphere in the boundary layers

    Science.gov (United States)

    Sergeev, Daniil; Kandaurov, Alexander; Troitskaya, Yuliya; Vdovin, Maxim

    The processes of momentum and heat transfer between ocean and atmosphere in the boundary layer were investigated within laboratory modeling for a wide range of wind speed and surface wave including hurricane conditions. Experiments were carried out on the Wind-Wave Flume of the Large Thermostratified Tank of IAP RAS. A special net located under the surface at different depths allows to vary parameters of surface waves independently on wind parameters. Theory of self-similarity of air flow parameters in the flume was used to calculate values aerodynamic and heat transfer coefficients from the measured velocity and temperature profiles by Pito and hotfilm gauges respectively. Simultaneous measurements of surface elevation with system wire allow to obtain spectra and integral parameters of waves. It was demonstrated that in contrast to the drag coefficient, heat transfer coefficient is virtually independent of wind speed and wave parameters to the moment of the beginning of spray generation and then increases rapidly.

  1. Laboratory modelling of the transfer processes between the ocean and atmosphere in the boundary layers

    Directory of Open Access Journals (Sweden)

    Sergeev Daniil

    2017-01-01

    Full Text Available The processes of momentum and heat transfer between ocean and atmosphere in the boundary layer were investigated within laboratory modeling for a wide range of wind speed and surface wave including hurricane conditions. Experiments were carried out on the Wind-Wave Flume of the Large Thermostratified Tank of IAP RAS. A special net located under the surface at different depths allows to vary parameters of surface waves independently on wind parameters. Theory of self-similarity of air flow parameters in the flume was used to calculate values aerodynamic and heat transfer coefficients from the measured velocity and temperature profiles by Pito and hotfilm gauges respectively. Simultaneous measurements of surface elevation with system wire allow to obtain spectra and integral parameters of waves. It was demonstrated that in contrast to the drag coefficient, heat transfer coefficient is virtually independent of wind speed and wave parameters to the moment of the beginning of spray generation and then increases rapidly.

  2. NOAA Climate Data Record (CDR) of Atmospheric Layer Temperatures, Version 3.3

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Atmospheric Layer Temperature Climate Data Record (CDR) dataset is a monthly analysis of the tropospheric and stratospheric data using temperature sounding...

  3. Modelling hazardous surface hoar layers in the mountain snowpack over space and time

    Science.gov (United States)

    Horton, Simon Earl

    Surface hoar layers are a common failure layer in hazardous snow slab avalanches. Surface hoar crystals (frost) initially form on the surface of the snow, and once buried can remain a persistent weak layer for weeks or months. Avalanche forecasters have difficulty tracking the spatial distribution and mechanical properties of these layers in mountainous terrain. This thesis presents numerical models and remote sensing methods to track the distribution and properties of surface hoar layers over space and time. The formation of surface hoar was modelled with meteorological data by calculating the downward flux of water vapour from the atmospheric boundary layer. The timing of surface hoar formation and the modelled crystal size was verified at snow study sites throughout western Canada. The major surface hoar layers over several winters were predicted with fair success. Surface hoar formation was modelled over various spatial scales using meteorological data from weather forecast models. The largest surface hoar crystals formed in regions and elevation bands with clear skies, warm and humid air, cold snow surfaces, and light winds. Field surveys measured similar regional-scale patterns in surface hoar distribution. Surface hoar formation patterns on different slope aspects were observed, but were not modelled reliably. Mechanical field tests on buried surface hoar layers found layers increased in shear strength over time, but had persistent high propensity for fracture propagation. Layers with large crystals and layers overlying hard melt-freeze crusts showed greater signs of instability. Buried surface hoar layers were simulated with the snow cover model SNOWPACK and verified with avalanche observations, finding most hazardous surface hoar layers were identified with a structural stability index. Finally, the optical properties of surface hoar crystals were measured in the field with spectral instruments. Large plate-shaped crystals were less reflective at shortwave

  4. Shallow marine cloud topped boundary layer in atmospheric models

    Science.gov (United States)

    Janjic, Zavisa

    2017-04-01

    A common problem in many atmospheric models is excessive expansion over cold water of shallow marine planetary boundary layer (PBL) topped by a thin cloud layer. This phenomenon is often accompanied by spurious light precipitation. The "Cloud Top Entrainment Instability" (CTEI) was proposed as an explanation of the mechanism controlling this process in reality thereby preventing spurious enlargement of the cloudy area and widely spread light precipitation observed in the models. A key element of this hypothesis is evaporative cooling at the PBL top. However, the CTEI hypothesis remains controversial. For example, a recent direct simulation experiment indicated that the evaporative cooling couldn't explain the break-up of the cloudiness as hypothesized by the CTEI. Here, it is shown that the cloud break-up can be achieved in numerical models by a further modification of the nonsingular implementation of the Mellor-Yamada Level 2.5 turbulence closure model (MYJ) developed at the National Centers for Environmental Prediction (NCEP) Washington. Namely, the impact of moist convective instability is included into the turbulent energy production/dissipation equation if (a) the stratification is stable, (b) the lifting condensation level (LCL) for a particle starting at a model level is below the next upper model level, and (c) there is enough turbulent kinetic energy so that, due to random vertical turbulent motions, a particle starting from a model level can reach its LCL. The criterion (c) should be sufficiently restrictive because otherwise the cloud cover can be completely removed. A real data example will be shown demonstrating the ability of the method to break the spurious cloud cover during the day, but also to allow its recovery over night.

  5. Rocket dust storms and detached layers in the Martian atmosphere

    Science.gov (United States)

    Spiga, A.; Faure, J.; Madeleine, J.; Maattanen, A. E.; Forget, F.

    2012-12-01

    Airborne dust is the main climatic agent in the Martian environment. Local dust storms play a key role in the dust cycle; yet their life cycle is poorly known. Here we use mesoscale modeling with radiatively-active transported dust to predict the evolution of a local dust storm monitored by OMEGA onboard Mars Express. We show that the evolution of this dust storm is governed by deep convective motions. The supply of convective energy is provided by the absorption of incoming sunlight by dust particles, in lieu of latent heating in moist convection on Earth. We propose to use the terminology "rocket dust storm", or conio-cumulonimbus, to describe those storms in which rapid and efficient vertical transport takes place, injecting dust particles at high altitudes in the Martian troposphere (30 to 50 km). Combined to horizontal transport by large-scale winds, rocket dust storms form detached layers of dust reminiscent of those observed with instruments onboard Mars Global Surveyor and Mars Reconnaissance Orbiter. Detached layers are stable over several days owing to nighttime sedimentation being unable to counteract daytime convective transport, and to the resupply of convective energy at sunrise. The peak activity of rocket dust storms is expected in low-latitude regions at clear season, which accounts for the high-altitude tropical dust maximum unveiled by Mars Climate Sounder. Our findings on dust-driven deep convection have strong implications for the Martian dust cycle, thermal structure, atmospheric dynamics, cloud microphysics, chemistry, and robotic and human exploration.ensity-scaled dust optical depth at local times 1400 1600 and 1800 (lat 2.5°S, Ls 135°) hortwave heating rate at local time 1500 and latitude 2.5°S.

  6. Parameterization of a surface drag coefficient in conventionally neutral planetary boundary layer

    Energy Technology Data Exchange (ETDEWEB)

    Esau, I.N. [Nansen Environmental and Remote Sensing Center, Bergen (Norway)

    2004-07-01

    Modern large-scale models (LSMs) rely on surface drag coefficients to parameterize turbulent exchange between surface and the first computational level in the atmosphere. A classical parameterization in an Ekman boundary layer is rather simple. It is based on a robust concept of a layer of constant fluxes. In such a layer (log-layer), the mean velocity profile is logarithmic. It results in an universal dependence of the surface drag coefficient on a single internal non-dimensional parameter, namely the ratio of a height within this layer to a surface roughness length scale. A realistic near-neutral planetary boundary layer (PBL) is usually much more shallow than the idealized Ekman layer. The reason is that the PBL is developing against a stably stratified free atmosphere. The ambient atmospheric stratification reduces the PBL depth and simultaneously the depth of the log-layer. Therefore, the first computational level in the LSMs may be placed above the log-layer. In such a case, the classical parameterization is unjustified and inaccurate. The paper proposes several ways to improve the classical parameterization of the surface drag coefficient for momentum. The discussion is focused on a conventionally neutral PBL, i.e. on the neutrally stratified PBL under the stably stratified free atmosphere. The analysis is based on large eddy simulation (LES) data. This data reveals that discrepancy between drag coefficients predicted by the classical parameterization and the actual drag coefficients can be very large in the shallow PBL. The improved parameterizations provide a more accurate prediction. The inaccuracy is reduced to one-tenth of the actual values of the coefficients. (orig.)

  7. Parameterization of a surface drag coefficient in conventionally neutral planetary boundary layer

    Directory of Open Access Journals (Sweden)

    I. N. Esau

    2004-11-01

    Full Text Available Modern large-scale models (LSMs rely on surface drag coefficients to parameterize turbulent exchange between surface and the first computational level in the atmosphere. A classical parameterization in an Ekman boundary layer is rather simple. It is based on a robust concept of a layer of constant fluxes. In such a layer (log-layer, the mean velocity profile is logarithmic. It results in an universal dependence of the surface drag coefficient on a single internal non-dimensional parameter, namely the ratio of a height within this layer to a surface roughness length scale. A realistic near-neutral planetary boundary layer (PBL is usually much more shallow than the idealized Ekman layer. The reason is that the PBL is developing against a stably stratified free atmosphere. The ambient atmospheric stratification reduces the PBL depth and simultaneously the depth of the log-layer. Therefore, the first computational level in the LSMs may be placed above the log-layer. In such a case, the classical parameterization is unjustified and inaccurate.

    The paper proposes several ways to improve the classical parameterization of the surface drag coefficient for momentum. The discussion is focused on a conventionally neutral PBL, i.e. on the neutrally stratified PBL under the stably stratified free atmosphere. The analysis is based on large eddy simulation (LES data. This data reveals that discrepancy between drag coefficients predicted by the classical parameterization and the actual drag coefficients can be very large in the shallow PBL. The improved parameterizations provide a more accurate prediction. The inaccuracy is reduced to one-tenth of the actual values of the coefficients.

  8. Aerosols in the Convective Boundary Layer: Radiation Effects on the Coupled Land-Atmosphere System

    Science.gov (United States)

    Barbaro, E.; Vila-Guerau Arellano, J.; Ouwersloot, H. G.; Schroter, J.; Donovan, D. P.; Krol, M. C.

    2013-12-01

    We investigate the responses of the surface energy budget and the convective boundary-layer (CBL) dynamics to the presence of aerosols using a combination of observations and numerical simulations. A detailed observational dataset containing (thermo)dynamic variables observed at CESAR (Cabauw Experimental Site for Atmospheric Research) and aerosol information from the European Integrated Project on Aerosol, Cloud, Climate, and Air Quality Interactions (IMPACT/EUCAARI) campaign is employed to design numerical experiments reproducing two prototype clear-sky days characterized by: (i) a well-mixed residual layer above a ground inversion and (ii) a continuously growing CBL. A large-eddy simulation (LES) model and a mixed-layer (MXL) model, both coupled to a broadband radiative transfer code and a land-surface model, are used to study the impacts of aerosol scattering and absorption of shortwave radiation on the land-atmosphere system. We successfully validate our model results using the measurements of (thermo)dynamic variables and aerosol properties for the two different CBL prototypes studied here. Our findings indicate that in order to reproduce the observed surface energy budget and CBL dynamics, information of the vertical structure and temporal evolution of the aerosols is necessary. Given the good agreement between the LES and the MXL model results, we use the MXL model to explore the aerosol effect on the land-atmosphere system for a wide range of optical depths and single scattering albedos. Our results show that higher loads of aerosols decrease irradiance, imposing an energy restriction at the surface. Over the studied well-watered grassland, aerosols reduce the sensible heat flux more than the latent heat flux. As a result, aerosols increase the evaporative fraction. Moreover, aerosols also delay the CBL morning onset and anticipate its afternoon collapse. If also present above the CBL during the morning transition, aerosols maintain a persistent near-surface

  9. Wind instability of a foam layer sandwiched between the atmosphere and the ocean

    CERN Document Server

    Shtemler, Yuri M; Mond, Michael

    2007-01-01

    Kelvin-Helmholtz instability of short gravity waves is examined in order to explain the recent findings of the decrease in momentum transfer from hurricane winds to sea waves. A three-fluid configuration of a foam layer between the atmosphere and the ocean is suggested to provide signifficant stabilization of the system and shifting the marginal critical wavelength to the shortwave part of the spectrum. It is conjectured that such stabilization leads to the observed drag reduction. The high contrasts in three fluid densities provide a universal mechanism for stabilizing surface perturbations.

  10. Modulation mechanisms of marine atmospheric boundary layer at the Brazil-Malvinas Confluence region

    Science.gov (United States)

    de Camargo, Ricardo; Todesco, Enzo; Pezzi, Luciano Ponzi; de Souza, Ronald Buss

    2013-06-01

    The influence of the Brazil-Malvinas Confluence (BMC) region on the marine atmospheric boundary layer (MABL) is investigated through in situ data analysis of five different cruises (2004 to 2008) and numerical experiments with a regional atmospheric model. Two different groups of numerical experiments were performed in order to evaluate the relevance of static stability and hydrostatic balance physical mechanisms for the MABL instability. The first group used monthly climatological sea surface temperature (SST) as bottom boundary condition while the second used daily updated Advanced Microwave Scanning Radiometer-EOS SST data together with radiosondes and surface data assimilation. A reasonable agreement between numerical results and QuikSCAT wind data was observed through correlation coefficients and mean square error values. In terms of the horizontal structure of the MABL, stronger winds were found over the warm side of the BMC region as well as over the thermal front itself, which supports the coexistence of both modulation mechanisms. The analyzed patterns of surface atmospheric thermal advection showed a clear interaction between the synoptic and regional scales. The signature of the oceanic thermal front (almost meridionally oriented) on the air temperature at 2 m makes the temperature advection strongly determined by the zonal component of the wind. The analysis of momentum budget terms did not show a clear and reasonable explanation of the existence or predominance of the modulation mechanisms, and it also suggested the relevance of other effects, such as the idea based on unbalanced Coriolis force and turbulence/friction effects.

  11. How can a dusty cold pool change the diurnal evolution of the Saharan Atmospheric Boundary Layer ?

    Science.gov (United States)

    Kocha, Cécile; Flamant, Cyrille; Berckmans, Julie; Fink, Andreas; Garcia-Carreras, Luis; Knippertz, Peter; Lafore, Jean-Philippe; Marnas, Fabien; Marsham, John; Parker, Doug; Rosenberg, Philip; Ryder, Claire; Tulet, Pierre; Washington, Richard

    2013-04-01

    In the framework of the Fennec 2011 Special Observing period, a large and dusty density current (known as a haboob) was observed on the 21 June to cover half of the western part of the Sahara. Thanks to the AROME high resolution model used to forecast this event in real time, two research aircraft (the SAFIRE Falcon and the FAAM BAe 146) operated over Mauritania and Mali on that day, and we are able to document its characteristics in detail. Particularly large dust particles were observed in this haboob. These particles are known to absorb and scatter solar and thermal radiation. The comparison of AROME simulations with and without coupling with dust shows that the radiative impact of the dust induced a decrease of sensible heat fluxes by 200W/m²/AOD and an increase of the temperature in the atmospheric boundary layer by 1°C. Surface fluxes are one of the principal parameters controlling the growth of the boundary layer. However, during the day, the simulation coupled with dust shows a deeper boundary layer (reaching ~5km high) than the simulation without dust. Here, we explore the competition between surface heating and elevated heating in the boundary-layer development.

  12. 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

  13. Absorption and reflectivity of the lithium niobate surface masked with a graphene layer

    Science.gov (United States)

    Salas, O.; Garcés, E.; Castillo, F. L.; Magaña, L. F.

    2017-01-01

    We performed simulations of the interaction of a graphene layer with the surface of lithium niobate utilizing density functional theory and molecular dynamics at 300K and atmospheric pressure. We found that the graphene layer is physisorbed on the lithium niobate surface with an adsorption energy of -0.8205 eV/(carbon-atom). Subsequently, the energy band structure, the optical absorption and reflectivity of the new system were calculated. We found important changes in these physical properties with respect to the corresponding ones of a graphene layer and of a lithium niobate crystal.

  14. Differences in the efficacy of climate forcings explained by variations in atmospheric boundary layer depth.

    Science.gov (United States)

    Davy, Richard; Esau, Igor

    2016-05-25

    The Earth has warmed in the last century and a large component of that warming has been attributed to increased anthropogenic greenhouse gases. There are also numerous processes that introduce strong, regionalized variations to the overall warming trend. However, the ability of a forcing to change the surface air temperature depends on its spatial and temporal distribution. Here we show that the efficacy of a forcing is determined by the effective heat capacity of the atmosphere, which in cold and dry climates is defined by the depth of the planetary boundary layer. This can vary by an order of magnitude on different temporal and spatial scales, and so we get a strongly amplified temperature response in shallow boundary layers. This must be accounted for to assess the efficacy of a climate forcing, and also implies that multiple climate forcings cannot be linearly combined to determine the temperature response.

  15. Atmospheric Plasma Deposition of SiO2 Films for Adhesion Promoting Layers on Titanium

    Directory of Open Access Journals (Sweden)

    Liliana Kotte

    2014-12-01

    Full Text Available This paper evaluates the deposition of silica layers at atmospheric pressure as a pretreatment for the structural bonding of titanium (Ti6Al4V, Ti15V3Cr3Sn3Al in comparison to an anodizing process (NaTESi process. The SiO2 film was deposited using the LARGE plasma source, a linearly extended DC arc plasma source and applying hexamethyldisiloxane (HMDSO as a precursor. The morphology of the surface was analyzed by means of SEM, while the characterization of the chemical composition of deposited plasma layers was done by XPS and FTIR. The long-term durability of bonded samples was evaluated by means of a wedge test in hot/wet condition. The almost stoichiometric SiO2 film features a good long-term stability and a high bonding strength compared to the films produced with the wet-chemical NaTESi process.

  16. Application of Atmospheric Plasma-Sprayed Ferrite Layers for Particle Accelerators

    CERN Document Server

    Caspers, F; Federmann, S; Taborelli, M; Schulz, C; Bobzin, K; Wu, J

    2013-01-01

    A common problem in all kinds of cavity-like structures in particle accelerators is the occurrence of RF-resonances. Typically, ferrite plates attached to the walls of such structures as diagnostic devices, kickers or collimators, are used to dampen those undesired modes. However, the heat transfer rate from these plates to the walls is rather limited. Brazing ferrite plates to the walls is not possible in most cases due to the different thermal expansion coefficients. To overcome those limitations, atmospheric plasma spraying techniques have been investigated. Ferrite layers with a thickness from 50 μm to about 300 μm can be deposited on metallic surfaces like stainless steel exhibiting good thermal contact and still reasonable absorption properties. In this paper the technological aspects of plasma deposition are discussed and results of specifically developed RF loss measurement procedures for such thin magnetically lossy layers on metal are presented.

  17. Controlled nanostructured silver coated surfaces by atmospheric pressure chemical vapour deposition

    Energy Technology Data Exchange (ETDEWEB)

    Sheel, D.W.; Brook, L.A.; Yates, H.M. [Institute for Materials Research, Salford University, Manchester, M5 4 WT (United Kingdom)

    2008-02-15

    Thin film silver has been widely reported for its interesting properties. In this paper we describe a route to produce controlled nanostructured silver layers. A combination of Flame Assisted Chemical Vapour Deposition at atmospheric pressure, with low cost and a low toxicity silver precursor, was used to generate coatings of structured silver surfaces on glass. This approach gives a high degree of control of surface structure, density and topography. These layers have potential applications in areas such as catalysis, photo-activity and for biocidal surfaces. Our results indicate very high biocidal activity where the nano-structure is proposed as playing a significant role. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

  18. The effect of the Asian Monsoon to the atmospheric boundary layer over the Tibetan Plateau

    Science.gov (United States)

    Li, Maoshan; Su, Zhongbo; Chen, Xuelong; Zheng, Donghai; Sun, Fanglin; Ma, Yaoming; Hu, Zeyong

    2016-04-01

    Modulation of the diurnal variations in the convective activities associated with day-by-day changes of surface flux and soil moisture was observed in the beginning of the monsoon season on the central Tibetan plateau (Sugimoto et al., 2008) which indicates the importance of land-atmosphere interactions in determining convective activities over the Tibetan plateau. Detailed interaction processes need to be studied by experiments designed to evaluate a set of hypotheses on mechanisms and linkages of these interactions. A possible function of vegetation to increase precipitation in cases of Tibetan High type was suggested by Yamada and Uyeda (2006). Use of satellite derived plateau scale soil moisture (Wen et al., 2003) enables the verification of these hypotheses (e.g. Trier et al. 2004). To evaluate these feedbacks, the mesoscale WRF model will be used because several numerical experiments are being conducted to improve the soil physical parameterization in the Noah land surface scheme in WRF so that the extreme conditions on the Tibetan plateau could be adequately represented (Van der Velde et al., 2009) such that the impacts on the structure of the atmospheric boundary layer can be assessed and improved. The Tibetan Observational Research Platform (TORP) operated by the Institute of Tibetan Plateau (Ma et al., 2008) will be fully utilized to study the characteristics of the plateau climate and different aspects of the WRF model will be evaluated using this extensive observation platform (e.g. Su et al., 2012). Recently, advanced studies on energy budget have been done by combining field and satellite measurements over the Tibetan Plateau (e.g. Ma et al., 2005). Such studies, however, were based on a single satellite observation and for a few days over an annual cycle, which are insufficient to reveal the relation between the land surface energy budget and the Asian monsoon over the Tibetan plateau. Time series analysis of satellite observations will provide the

  19. CFD simulation of neutral ABL flows; Atmospheric Boundary Layer

    Energy Technology Data Exchange (ETDEWEB)

    Xiaodong Zhang

    2009-04-15

    This work is to evaluate the CFD prediction of Atmospheric Boundary Layer flow field over different terrains employing Fluent 6.3 software. How accurate the simulation could achieve depend on following aspects: viscous model, wall functions, agreement of CFD model with inlet wind velocity profile and top boundary condition. Fluent employ wall function roughness modifications based on data from experiments with sand grain roughened pipes and channels, describe wall adjacent zone with Roughness Height (Ks) instead of Roughness Length (z{sub 0}). In a CFD simulation of ABL flow, the mean wind velocity profile is generally described with either a logarithmic equation by the presence of aerodynamic roughness length z{sub 0} or an exponential equation by the presence of exponent. As indicated by some former researchers, the disagreement between wall function model and ABL velocity profile description will result in some undesirable gradient along flow direction. There are some methods to improve the simulation model in literatures, some of them are discussed in this report, but none of those remedial methods are perfect to eliminate the streamwise gradients in mean wind speed and turbulence, as EllipSys3D could do. In this paper, a new near wall treatment function is designed, which, in some degree, can correct the horizontal gradients problem. Based on the corrected model constants and near wall treatment function, a simulation of Askervein Hill is carried out. The wind condition is neutrally stratified ABL and the measurements are best documented until now. Comparison with measured data shows that the CFD model can well predict the velocity field and relative turbulence kinetic energy field. Furthermore, a series of artificial complex terrains are designed, and some of the main simulation results are reported. (au)

  20. Surface Morphology of Fe(III-Porphyrin Thin Layers as Characterized by Atomic Force Microscopy

    Directory of Open Access Journals (Sweden)

    Utari Utari

    2016-12-01

    Full Text Available Surface morphology of Fe(III–porphyrin thin layers was studied using atomic force microscopy. The thin layer samples used in these experiments were deposited by spin coating methods on indium–tin-oxide substrates at room temperature under atmospheric conditions. Variations of thin layer of Fe(III-porphyrin were done by modifying the rotational speed and the concentration of the solution. The experimental results demonstrated that the Fe(III–porphyrin layers were observed as discrete nanomolecular islands. Both the number of nano-islands and thickness of the layer increased significantly with increasing concentration. A layer thickness of 15 nm was obtained for low concentrations of 0.00153 M and become 25 nm for dense concentrations of 0.153 M. Conversely, the higher number of islands were deposited on the surface of the substrate at a lower rotational speed.

  1. Scaling Characteristics of Mesoscale Wind Fields in the Lower Atmospheric Boundary Layer: Implications for Wind Energy

    Science.gov (United States)

    Kiliyanpilakkil, Velayudhan Praju

    Atmospheric motions take place in spatial scales of sub-millimeters to few thousands of kilometers with temporal changes in the atmospheric variables occur in fractions of seconds to several years. Consequently, the variations in atmospheric kinetic energy associated with these atmospheric motions span over a broad spectrum of space and time. The mesoscale region acts as an energy transferring regime between the energy generating synoptic scale and the energy dissipating microscale. Therefore, the scaling characterizations of mesoscale wind fields are significant in the accurate estimation of the atmospheric energy budget. Moreover, the precise knowledge of the scaling characteristics of atmospheric mesoscale wind fields is important for the validation of the numerical models those focus on wind forecasting, dispersion, diffusion, horizontal transport, and optical turbulence. For these reasons, extensive studies have been conducted in the past to characterize the mesoscale wind fields. Nevertheless, the majority of these studies focused on near-surface and upper atmosphere mesoscale regimes. The present study attempt to identify the existence and to quantify the scaling of mesoscale wind fields in the lower atmospheric boundary layer (ABL; in the wind turbine layer) using wind observations from various research-grade instruments (e.g., sodars, anemometers). The scaling characteristics of the mesoscale wind speeds over diverse homogeneous flat terrains, conducted using structure function based analysis, revealed an altitudinal dependence of the scaling exponents. This altitudinal dependence of the wind speed scaling may be attributed to the buoyancy forcing. Subsequently, we use the framework of extended self-similarity (ESS) to characterize the observed scaling behavior. In the ESS framework, the relative scaling exponents of the mesoscale atmospheric boundary layer wind speed exhibit quasi-universal behavior; even far beyond the inertial range of turbulence (Delta

  2. Transfer of atmospheric matter through the euphotic layer in the northwestern Mediterranean: seasonal pattern and driving forces

    Science.gov (United States)

    Migon, Christophe; Sandroni, Valérie; Marty, Jean-Claude; Gasser, Beat; Miquel, Juan-Carlos

    The transfer of atmospheric particulate matter through the surface marine layer was studied by comparing atmospheric and marine fluxes. Time series were obtained from the coupling of a coastal atmospheric sampling station (Cap Ferrat, French Riviera) and a marine sampling site (DYFAMED site, central Ligurian Sea). Liquid phase traps were used for measuring total atmospheric fluxes and sediment traps deployed at 200 m depth for measuring marine fluxes. Fluxes of mass, aluminium, and soluble anthropogenic metals (Cd, Pb and Zn) were obtained from both these reservoirs. Physical and biological time series data acquired at the DYFAMED site also were used to describe a three-step seasonal transfer scenario: In summer and autumn, during the period of water stratification, marine fluxes are low and do not account for the transfer of lithogenic material, as revealed by low Al to mass flux ratios and high proportions of organic carbon at 200 m depth. Atmospheric material accumulates along the thermocline, while a series of physico-chemical processes lead to the formation of small (⩽150 μm) non-biogenic organic aggregates. In winter, the sinking of dense water that occurs in the Ligurian Sea is responsible for a rapid downward transfer of the lithogenic matter accumulated in the surface layer. The fact that soluble trace metals (e.g., cadmium) accumulated in the surface layer are only partially found in sediment traps may indicate that sorption processes play a minor role in the formation of organic aggregates, compared with coagulation processes. In spring, nutrients brought to surface waters by the winter vertical mixing allow phytoplanktonic blooms, and the transfer of atmospheric matter is then governed by the temporal variations of biological activity. The seasonal variability of the vertical transfer leads to the concept of seasonal variability of elemental residence times in the euphotic layer.

  3. Analytical solution for the convectively-mixed atmospheric boundary layer

    NARCIS (Netherlands)

    Ouwersloot, H.G.; Vilà-Guerau de Arellano, J.

    2013-01-01

    Based on the prognostic equations of mixed-layer theory assuming a zeroth order jump at the entrainment zone, analytical solutions for the boundary-layer height evolution are derived with different degrees of accuracy. First, an exact implicit expression for the boundary-layer height for a situation

  4. Surface-Atmosphere Moisture Coupling in Eurasian Frozen Ground Regions

    Science.gov (United States)

    Frauenfeld, O. W.; Ford, T.

    2014-12-01

    Permafrost represents an impermeable barrier to moisture, resulting in a saturated or near-saturated surface layer during the warm season in many continuous and discontinuous permafrost zones. These surface conditions could lead to enhanced convection and precipitation during the warm season, and significant local recycling of moisture. In areas underlain by sporadic or isolated permafrost, or in seasonally frozen areas, the moisture can drain away more readily, resulting in much drier soil conditions. As climate change causes frozen ground degradation, this will thus also alter the patterns of atmospheric convection, moisture recycling, and the hydrologic cycle in high-latitude land areas. In this study, we analyze evaporative fraction (EF) as a proxy for evapotranspiration, and precipitation from the Modern-Era Retrospective analysis for Research and Applications (MERRA-land) reanalysis dataset. We focus on 1979-2012 and document patterns and changes in EF over the Eurasian high latitudes. We find strong, positive April EF trends over the study period, particularly in the Lena River Basin, 80% of which is underlain by continuous permafrost. In fact, these significant positive trends in spring EF are strongest over continuous permafrost across the Eurasian high latitudes, but negative for sporadic and isolated permafrost. In addition, we find a strong, statistically significant relationship between EF anomalies and the probability of subsequent precipitation over the Lena Basin during April. This association therefore suggests a potential land-atmosphere coupling between frozen ground and precipitation. As the permafrost and seasonally frozen ground distribution changes in the future, this will likely have repercussions for the Arctic hydrologic cycle.

  5. Formation of a nanocrystalline layer on the surface of stone wool fibers

    DEFF Research Database (Denmark)

    Yue, Yuanzheng; Korsgaard, Martin; Kirkegaard, Lise Frank

    2009-01-01

    In the present paper, we report a simple approach for creating a nanocrystalline layer on the surface of stone wool fibers (SWFs) with a basalt-like composition. The approach is based on a preoxidation process of the SWFs in atmospheric air at a temperature around the glass transition temperature...

  6. Early-time spinodal decomposition in the surface layer

    Science.gov (United States)

    Xiong, G. M.; Gong, C. D.

    1989-05-01

    The early stages of spinodal decomposition in the surface layer of a semi-infinite Ising model are studied by using the theory of Langer, Bar-on, and Miller and the self-consistent method. It is shown that the speed of phase separation in the surface layer is faster than that in the bulk because of the surface enhancement, and the one-point distribution function in the surface is different from that of the bulk. It is inferred that the surface with a negative enhancement (C>0) acts as a two-dimensional ``nucleus'' for the phase separation and for forming a ``wetting layer.''

  7. The atmospheric boundary layer during wintertime persistent inversions in the Grenoble valleys

    Directory of Open Access Journals (Sweden)

    Yann Largeron

    2016-07-01

    Full Text Available This study addresses the atmospheric boundary layer dynamics in the Grenoble valleys during persistent inversions, for 5 months during the 2006-2007 winter. During a persistent inversion, the boundary layer contains a layer with a positive vertical temperature gradient over a few days. Temperature data recorded on the valley sidewalls are first used. A bulk measure of the boundary layer stability, based upon the temperature difference between the valley top and the valley bottom, is introduced and a criterion is proposed to detect persistent inversions. We show that this criterion is equivalently expressed in terms of the heat deficit inside the boundary layer. Nine episodes are detected and coincide with the PM10-polluted periods of the 2006-2007 winter.Secondly, the five strongest and longest persistent inversions are simulated using the MesoNH model. Focus is made on the stagnation stage of the episode, during which the inversion exhibits a diurnal cycle that does not significantly evolve from day to day. Whatever the episode, the inversion develops from the ground over a height of about 1200 m, with a nighttime temperature strength of about 20 K.The boundary-layer dynamics within the inversion layer are fully decoupled from the (anticyclonic, weak synoptic flow, independent from the synoptic-wind direction and similar whatever the episode. This implies that these dynamics are controlled by thermal winds and solely depends upon the geometry of the topography and upon the radiative cooling of the ground.Finally, a two-day high-resolution simulation is made for the strongest case, representative of any persistent inversion. The flow pattern displays a well-defined spatial structure, with a vertical layering resulting from the superposition of the down-valley winds flowing from the different valleys surrounding Grenoble. This pattern persists all day long over a shallow convective layer of about 50 m forming above the ground during the reduced

  8. Shear-horizontal surface waves on piezoelectric ceramics with depolarized surface layer.

    Science.gov (United States)

    Kielczynski, P J; Pajewski, W; Szalewski, M

    1989-01-01

    Theoretical analysis and numerical results describing the propagation of SH (shear-horizontal) surface waves on piezoelectric ceramics with a depolarized surface layer are described. SH surface waves propagating in piezoelectric ceramics with a depolarized surface layer are shown to be a mixture of the Bleustein-Gulyaev surface wave, electrical potential, and the Love surface-wave mechanical displacement. Depolarization of the surface layer in piezoelectric ceramics produces strong dispersion and a multimode structure of the SH surface wave. The penetration depth of the SH surface waves propagating on an electrically free surface of a piezoelectric ceramic with a depolarized surface layer can be significantly smaller than that of the Bleustein-Gulyaev surface waves propagating on a free piezoelectric half-space. It is concluded that piezoelectric ceramics with a depolarized surface layer can be used in hybrid piezoelectric semiconductor convolvers of reduced size.

  9. Corrosion of Metal Films with Defective Surface Protection Layers.

    Science.gov (United States)

    1980-07-01

    A. L. Nicklen and D. R. Gabe, "A. C. Anodizing of Aluminum in Sulphuric Acid ," Surface Technol. 7, 353-359 (1978). 160. K. Nisancioglu and H. Holtan... Dielectric Layers Electrochemical Measurements Aluminum Thin Films Surface pH Measurements Gold Thin Films TRACT (Contfne o- reverse aide Hf nec.eary...12 2. Dielectric Layers..........................................3 3. Metallization

  10. Effect of surface morphology on atmospheric corrosion behaviour of ...

    Indian Academy of Sciences (India)

    Effect of surface morphology on atmospheric corrosion behaviour of Fe-based metallic glass, Fe67Co18Si14B1 ... present in atmospheric rust were analysed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) to be goethite, lepidocrocite, magnetite, cobalt oxide and cobalt hydroxide phases.

  11. Layers of Porous Superhydrophobic Surfaces for Robust Water Repellency

    Science.gov (United States)

    Ahmadi, Farzad; Boreyko, Jonathan; Nature-Inspired Fluids; Interfaces Team

    2015-11-01

    In nature, birds exhibit multiple layers of superhydrophobic feathers that repel water. Inspired by bird feathers, we utilize porous superhydrophobic surfaces and compare the wetting and dewetting characteristics of a single surface to stacks of multiple surfaces. The superhydrophobic surfaces were submerged in water in a closed chamber. Pressurized gas was regulated to measure the critical pressure for the water to fully penetrate through the surfaces. In addition to using duck feathers, two-tier porous superhydrophobic surfaces were fabricated to serve as synthetic mimics with a controlled surface structure. The energy barrier for the wetting transition was modeled as a function of the number of layers and their orientations with respect to each other. Moreover, after partial impalement into a subset of the superhydrophobic layers, it was observed that a full dewetting transition was possible, which suggests that natural organisms can exploit their multiple layers to prevent irreversible wetting.

  12. Contact mechanics for layered materials with randomly rough surfaces.

    Science.gov (United States)

    Persson, B N J

    2012-03-07

    The contact mechanics model of Persson is applied to layered materials. We calculate the M function, which relates the surface stress to the surface displacement, for a layered material, where the top layer (thickness d) has different elastic properties than the semi-infinite solid below. Numerical results for the contact area as a function of the magnification are presented for several cases. As an application, we calculate the fluid leak rate for laminated rubber seals.

  13. Profiles of Wind and Turbulence in the Coastal Atmospheric Boundary Layer of Lake Erie

    KAUST Repository

    Wang, H

    2014-06-16

    Prediction of wind resource in coastal zones is difficult due to the complexity of flow in the coastal atmospheric boundary layer (CABL). A three week campaign was conducted over Lake Erie in May 2013 to investigate wind characteristics and improve model parameterizations in the CABL. Vertical profiles of wind speed up to 200 m were measured onshore and offshore by lidar wind profilers, and horizontal gradients of wind speed by a 3-D scanning lidar. Turbulence data were collected from sonic anemometers deployed onshore and offshore. Numerical simulations were conducted with the Weather Research Forecasting (WRF) model with 2 nested domains down to a resolution of 1-km over the lake. Initial data analyses presented in this paper investigate complex flow patterns across the coast. Acceleration was observed up to 200 m above the surface for flow coming from the land to the water. However, by 7 km off the coast the wind field had not yet reached equilibrium with the new surface (water) conditions. The surface turbulence parameters over the water derived from the sonic data could not predict wind profiles observed by the ZephlR lidar located offshore. Horizontal wind speed gradients near the coast show the influence of atmospheric stability on flow dynamics. Wind profiles retrieved from the 3-D scanning lidar show evidence of nocturnal low level jets (LLJs). The WRF model was able to capture the occurrence of LLJ events, but its performance varied in predicting their intensity, duration, and the location of the jet core.

  14. Change of Surface Roughness and Planetary Boundary Layer

    DEFF Research Database (Denmark)

    Jensen, Niels Otto

    1978-01-01

    The ratio between upstream and far downstream surface friction velocities relative to a change in surface roughness is given on the basis of results from surface Rossby number similarity theory. By simple theories for the internal boundary layer, which are found to compare quite well with recent...... numerical results from higher-order closure models, it is found that, even at a downwind distance such that the internal boundary layer has grown to the full height of the planetary boundary layers, the surface stress still considerably exceeds the equilibrium value...

  15. Meteorological responses in the atmospheric boundary layer over southern England to the deep partial eclipse of 20 March 2015.

    Science.gov (United States)

    Burt, Stephen

    2016-09-28

    A wide range of surface and near-surface meteorological observations were made at the University of Reading's Atmospheric Observatory in central southern England (latitude 51.441° N, longitude 0.938° W, altitude 66 m above mean sea level) during the deep partial eclipse on the morning of 20 March 2015. Observations of temperature, humidity, radiation, wind speed and direction, and atmospheric pressure were made by computerized logging equipment at 1 Hz, supplemented by an automated cloud base recorder sampling at 1 min intervals and a high-resolution (approx. 10 m vertical interval) atmospheric sounding by radiosonde launched from the same location during the eclipse. Sources and details of each instrumental measurement are described briefly, followed by a summary of observed and derived measurements by meteorological parameter. Atmospheric boundary layer responses to the solar eclipse were muted owing to the heavily overcast conditions which prevailed at the observing location, but instrumental records of the event documented a large (approx. 80%) reduction in global solar radiation, a fall in air temperature of around 0.6°C, a decrease in cloud base height, and a slight increase in atmospheric stability during the eclipse. Changes in surface atmospheric moisture content and barometric pressure were largely insignificant during the event.This article is part of the themed issue 'Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse'. © 2016 The Author(s).

  16. Characterization of the atmospheric boundary layer from radiosonde ...

    Indian Academy of Sciences (India)

    moisture) or substances originating from the sur- face. It is usually flatter than the boundary layer, but fills the whole ABL in the deep convective boundary layers ..... Wea. Rev. 92 235–242. Holzworth G C 1967 Mixing depths, wind speeds and air pollution potential for selected locations in the United. States; J. Appl. Meteorol.

  17. Surface Defects and Thermodynamics of Chemisorbed Layers.

    Science.gov (United States)

    1979-09-14

    dimensional layer). For finite repulsions, the transition at esat for a given non-p(lxl) layer represents a true order-disorder transition into the unoccupied...transformation at 0sa t is second-order, and the transformations below esat out of the one-phase region t the lattice vapor phase are most likely also second...is 0 = 0.5. Real phase diagrams are never symmetric about the saturation coverage. (After Binder and Landau, Ref. 23). Figure 5: Schematic diagram of

  18. Harvesting Atmospheric Ions Using Surface Electromagnetic Wave Technologies

    Directory of Open Access Journals (Sweden)

    Louis Wai Yip Liu

    2017-05-01

    Full Text Available For the first time, this paper discloses the use of flowing water for capturing atmospheric ions into a DC electricity. The proposed methodology can be employed to neutralize the positively charged pollutants in air, which are believed to be harmful to our health. Methodology: Atmospheric ions can be collected by a negatively charged antenna which comprises a dielectric layer sandwiched between a top aluminium layer and a bottom lead plate. The top aluminium layer is used to collect the ambient protons, whilst the bottom lead plate is negatively charged by a negative static electricity extracted from flowing water. The voltage has been measured between the top aluminium layer and the bottom lead plate with and without any sunlight. Results: Without any UV light or other electromagnetic disturbance, the generated voltage has rapidly increased from 200 mV to 480 mV within 5 seconds if the bottom lead plate is connected to the negative ion source. Without the negative ion source, however, the output voltage fell to around 10 mV and any significant voltage rise can be observed even in the presence of an UV light. Conclusions: Capturing atmospheric ions is technically feasible. Measured results suggest that, when used in conjunction with a negative ion source, the proposed device can harvest atmospheric ions without any UV light.

  19. Significant Atmospheric Boundary Layer Change Observed above an Agulhas Current Warm Cored Eddy

    Directory of Open Access Journals (Sweden)

    C. Messager

    2016-01-01

    Full Text Available The air-sea impact of a warm cored eddy ejected from the Agulhas Retroflection region south of Africa was assessed through both ocean and atmospheric profiling measurements during the austral summer. The presence of the eddy causes dramatic atmospheric boundary layer deepening, exceeding what was measured previously over such a feature in the region. This deepening seems mainly due to the turbulent heat flux anomaly above the warm eddy inducing extensive deep and persistent changes in the atmospheric boundary layer thermodynamics. The loss of heat by turbulent processes suggests that this kind of oceanic feature is an important and persistent source of heat for the atmosphere.

  20. Laboratory simulations of the atmospheric mixed-layer in flow ...

    Science.gov (United States)

    A laboratory study of the influence of complex terrain on the interface between a well-mixed boundary layer and an elevated stratified layer was conducted in the towing-tank facility of the U.S. Environmental Protection Agency. The height of the mixed layer in the daytime boundary layer can have a strong influence on the concentration of pollutants within this layer. Deflections of streamlines at the height of the interface are primarily a function of hill Froude number (Fr), the ratio of mixed-layer height (zi) to terrain height (h), and the crosswind dimension of the terrain. The magnitude of the deflections increases as Fr increases and zi / h decreases. For mixing-height streamlines that are initially below the terrain top, the response is linear with Fr; for those initially above the terrain feature the response to Fr is more complex. Once Fr exceeds about 2, the terrain related response of the mixed layer interface decreases somewhat with increasing Fr (toward more neutral flow). Deflections are also shown to increase as the crosswind dimensions of the terrain increases. Comparisons with numerical modeling, limited field data and other laboratory measurements reported in the literature are favorable. Additionally, visual observations of dye streamers suggests that the flow structure exhibited for our elevated inversions passing over three dimensional hills is similar to that reported in the literature for continuously stratified flow over two-dimensional h

  1. A unified account of perceptual layering and surface appearance in terms of gamut relativity.

    Science.gov (United States)

    Vladusich, Tony; McDonnell, Mark D

    2014-01-01

    When we look at the world--or a graphical depiction of the world--we perceive surface materials (e.g. a ceramic black and white checkerboard) independently of variations in illumination (e.g. shading or shadow) and atmospheric media (e.g. clouds or smoke). Such percepts are partly based on the way physical surfaces and media reflect and transmit light and partly on the way the human visual system processes the complex patterns of light reaching the eye. One way to understand how these percepts arise is to assume that the visual system parses patterns of light into layered perceptual representations of surfaces, illumination and atmospheric media, one seen through another. Despite a great deal of previous experimental and modelling work on layered representation, however, a unified computational model of key perceptual demonstrations is still lacking. Here we present the first general computational model of perceptual layering and surface appearance--based on a boarder theoretical framework called gamut relativity--that is consistent with these demonstrations. The model (a) qualitatively explains striking effects of perceptual transparency, figure-ground separation and lightness, (b) quantitatively accounts for the role of stimulus- and task-driven constraints on perceptual matching performance, and (c) unifies two prominent theoretical frameworks for understanding surface appearance. The model thereby provides novel insights into the remarkable capacity of the human visual system to represent and identify surface materials, illumination and atmospheric media, which can be exploited in computer graphics applications.

  2. Preservation of Archaeal Surface Layer Structure During Mineralization

    Science.gov (United States)

    Kish, Adrienne; Miot, Jennyfer; Lombard, Carine; Guigner, Jean-Michel; Bernard, Sylvain; Zirah, Séverine; Guyot, François

    2016-05-01

    Proteinaceous surface layers (S-layers) are highly ordered, crystalline structures commonly found in prokaryotic cell envelopes that augment their structural stability and modify interactions with metals in the environment. While mineral formation associated with S-layers has previously been noted, the mechanisms were unconstrained. Using Sulfolobus acidocaldarius a hyperthermophilic archaeon native to metal-enriched environments and possessing a cell envelope composed only of a S-layer and a lipid cell membrane, we describe a passive process of iron phosphate nucleation and growth within the S-layer of cells and cell-free S-layer “ghosts” during incubation in a Fe-rich medium, independently of metabolic activity. This process followed five steps: (1) initial formation of mineral patches associated with S-layer; (2) patch expansion; (3) patch connection; (4) formation of a continuous mineral encrusted layer at the cell surface; (5) early stages of S-layer fossilization via growth of the extracellular mineralized layer and the mineralization of cytosolic face of the cell membrane. At more advanced stages of encrustation, encrusted outer membrane vesicles are formed, likely in an attempt to remove damaged S-layer proteins. The S-layer structure remains strikingly well preserved even upon the final step of encrustation, offering potential biosignatures to be looked for in the fossil record.

  3. Spatial structures in the heat budget of the Antarctic atmospheric boundary layer

    Directory of Open Access Journals (Sweden)

    W. J. van de Berg

    2008-01-01

    Full Text Available Output from the regional climate model RACMO2/ANT is used to calculate the heat budget of the Antarctic atmospheric boundary layer (ABL. The main feature of the wintertime Antarctic ABL is a persistent temperature deficit compared to the free atmosphere. The magnitude of this deficit is controlled by the heat budget. During winter, transport of heat towards the surface by turbulence and net longwave emission are the primary ABL cooling terms. These processes show horizontal spatial variability only on continental scales. Vertical and horizontal, i.e. along-slope, advection of heat are the main warming terms. Over regions with convex ice sheet topography, i.e. domes and ridges, warming by downward vertical advection is enhanced due to divergence of the ABL wind field. Horizontal advection balances excess warming caused by vertical advection, hence the temperature deficit in the ABL weakens over domes and ridges along the prevailing katabatic wind. Conversely, vertical advection is reduced in regions with concave topography, i.e. valleys, where the ABL temperature deficit enlarges along the katabatic wind. Along the coast, horizontal and vertical advection is governed by the inability of the large-scale circulation to adapt to small scale topographic features. Meso-scale topographic structures have thus a strong impact on the ABL winter temperature, besides latitude and surface elevation. During summer, this mechanism is much weaker, and the horizontal variability of ABL temperatures is smaller.

  4. [Characteristics of Winter Atmospheric Mixing Layer Height in Beijing-Tianjin-Hebei Region and Their Relationship with the Atmospheric Pollution].

    Science.gov (United States)

    Li, Meng; Tang, Gui-qian; Huang, Jun; Liu, Zi-rui; An, Jun-lin; Wang, Yue-si

    2015-06-01

    Atmospheric mixing layer height (MLH) is one of the main factors affecting the atmospheric diffusion and plays an important role in air quality assessment and distribution of the pollutants. Based on the ceilometers data, this paper has made synchronous observation on MLH in Beijing-Tianjin-Hebei region (Beijing, Tianjin, Shijiazhuang and Qinhuangdao) in heavy polluted February 2014 and analyzed the respective overall change and its regional features. Results show that in February 2014,the average of mixing layer height in Qinhuangdao is the highest, up to 865 +/- 268 m, and in Shijiazhuang is the lowest (568 +/- 207 m), Beijing's and Tianjin's are in between, 818 +/- 319 m and 834 +/- 334 m respectively; Combined with the meteorological data, we find that radiation and wind speed are main factors of the mixing layer height; The relationship between the particle concentration and mixing layer height in four sites suggests that mixing layer is less than 800 m, concentration of fine particulate matter in four sites will exceed the national standard (GB 3095-2012, 75 microg x m(-3)). During the period of observation, the proportion of days that mixing layer is less than 800 m in Beijing, Tianjin, Shijiazhuang and Qinhuangdao are 50%, 43%, 80% and 50% respectively. Shijiazhuang though nearly formation contaminant concentration is high, within the atmospheric mixed layer pollutant load is not high. Unfavorable atmospheric diffusion conditions are the main causes of heavy pollution in Shijiazhuang for a long time. The results of the study are of great significance for cognitive Beijing-Tianjin-Hebei area pollution distribution, and can provide a scientific reference for reasonable distribution of regional pollution sources.

  5. Study of stable atmospheric boundary layer characterization over highveld region of South Africa

    CSIR Research Space (South Africa)

    Luhunga, P

    2011-09-01

    Full Text Available ATMOSPHERIC BOUNDARY LAYER CHARACTERIZATION OVER HIGHVELD REGION OF SOUTH AFRICA Philbert Luhunga1, 2, 3, George Djolov1, Venkataraman Sivakumar1,4,5 1 University of Pretoria, Department of Geography Geoinformatics and Meterology, Lynnwood road, 0001.... INTRODUCTION The stable atmospheric boundary layer (SBL) study over the Highveld South Africa has a special relevance, since it has the majority of the electric power generating plants located in this region. SBL is characterized by a steady wind near...

  6. Experimental investigation on the wake interference among wind turbines sited in atmospheric boundary layer winds

    Science.gov (United States)

    Tian, W.; Ozbay, A.; Wang, X. D.; Hu, H.

    2017-08-01

    We examined experimentally the effects of incoming surface wind on the turbine wake and the wake interference among upstream and downstream wind turbines sited in atmospheric boundary layer (ABL) winds. The experiment was conducted in a large-scale ABL wind tunnel with scaled wind turbine models mounted in different incoming surface winds simulating the ABL winds over typical offshore/onshore wind farms. Power outputs and dynamic loadings acting on the turbine models and the wake flow characteristics behind the turbine models were quantified. The results revealed that the incoming surface winds significantly affect the turbine wake characteristics and wake interference between the upstream and downstream turbines. The velocity deficits in the turbine wakes recover faster in the incoming surface winds with relatively high turbulence levels. Variations of the power outputs and dynamic wind loadings acting on the downstream turbines sited in the wakes of upstream turbines are correlated well with the turbine wakes characteristics. At the same downstream locations, the downstream turbines have higher power outputs and experience greater static and fatigue loadings in the inflow with relatively high turbulence level, suggesting a smaller effect of wake interference for the turbines sited in onshore wind farms.

  7. Behavior of self-confined spherical layer of light radiation in the air atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Torchigin, V.P.; Torchigin, A.V

    2004-07-26

    Behavior of thin spherical layer of intensive light in an inhomogeneous atmosphere is considered. It is shown that the behavior is similar to puzzling and mysterious behavior of ball lightnings. Under assumption that ball lightning moves along the gradient of atmosphere air density process of ball lightning penetration in a salon of a flying airplane is analyzed.

  8. Turbulent exchange of energy, momentum, and reactive gases between high vegetation and the atmospheric boundary layer

    NARCIS (Netherlands)

    Shapkalijevski, M.M.

    2017-01-01

    This thesis deals with the representation of the exchange of energy, momentum and chemically reactive compounds between the land, covered by high vegetation, and the lowest part of the atmosphere, named as atmospheric boundary layer (ABL). The study presented in this thesis introduces the roughness

  9. Computational Fluid Dynamics model of stratified atmospheric boundary-layer flow

    DEFF Research Database (Denmark)

    Koblitz, Tilman; Bechmann, Andreas; Sogachev, Andrey

    2015-01-01

    transport, are mostly ignored. In order to decrease the uncertainty of wind resource assessment, the present work focuses on atmospheric flows that include stability and Coriolis effects. The influence of these effects on the whole atmospheric boundary-layer are examined using a Reynolds-averaged Navier–Stokes...

  10. Modeling of flow in microchannel with bubbles layer on surface

    Directory of Open Access Journals (Sweden)

    Gluzdov Dmitriy

    2017-01-01

    Full Text Available Results of 2D numerical solution of liquid flow in microchannel with bubbles layers on surface are presented. Bubbles layers are modeled by setting of bubble size and Navier slip condition. Calculations have been done using OpenFoam PISO method. The results of modeling compared with analytical solution.

  11. Surface plasmon polariton modulator with optimized active layer

    DEFF Research Database (Denmark)

    Babicheva, Viktoriia; Lavrinenko, Andrei

    2012-01-01

    A multilayered waveguide, which supports surface plasmon polaritons, is considered as an absorption modulator. The waveguide core consists of a silicon nitride layer and ultrathin layer with the varied carrier density embedded between two silver plates, which also serve as electrodes. Under...

  12. Surface layer temperature inversion in the Arabian Sea during winter

    Digital Repository Service at National Institute of Oceanography (India)

    Pankajakshan, T.; Ghosh, A

    Surface layer temperature inversion in the south eastern Arabian Sea, during winter has been studied using Bathythermograph data collected from 1132 stations. It is found that the inversion in this area is a stable seasonal feature...

  13. On the Nature, Theory, and Modeling of Atmospheric Planetary Boundary Layers

    DEFF Research Database (Denmark)

    Baklanov, Alexander A.; Grisogono, Branko; Bornstein, Robert

    2011-01-01

    The gap between our modern understanding of planetary boundary layer physics and its decades-old representations in current operational atmospheric models is widening, which has stimulated this review of the current state of the art and an analysis of the immediate needs in boundary layer theory......, measurements, and modeling....

  14. Formulation of a Prototype Coupled Atmospheric and Oceanic Boundary Layer Model.

    Science.gov (United States)

    1982-12-01

    layers. The approach will be to compare observed evolutions in the oceanic and atmospheric boundary layers with predictions from bulk modelo wherein...a very complex subject and is beyond the scope of this paper. An excellent review of this sub- ject has beer. published by Fairall (1981). An

  15. Tribological Properties of Surface Layer with Boron in Friction Pairs

    Science.gov (United States)

    Lubas, Janusz

    The aim of the present work is to determine the influence of technologically produced boron surface layers on the friction parameters in the sliding pairs under the conditions of mixed friction. The tribological evaluation included ion nitrided, pack borided, laser borided, quenched and tempered surface layers and TiB2 coating deposited on 38CrAlMo5-10, 46Cr2 and 30MnB4 steels. Modified surface layers of annular samples were matched under test conditions with counter-sample made from AlSn20 bearing alloy. Tested sliding pairs were lubricated with 15 W/40 Lotos mineral engine oil. The tribological tests were conducted on a T-05 block on ring tester. The applied steel surface layer modification with boron allows surface layers to be created with pre-determined tribological characteristics required for the elements of kinematic pairs operating in the conditions of sliding friction. Pack boronizing reduces the friction coefficient during the start-up of the frictional pair and the maximum start-up resistance level is similar to the levels of pairs with nitrided surface layers.

  16. Exploration of Venus' Deep Atmosphere and Surface Environment

    Science.gov (United States)

    Glaze, L. S.; Amato, M.; Garvin, J. B.; Johnson, N. M.

    2017-01-01

    Venus formed in the same part of our solar system as Earth, apparently from similar materials. Although both planets are about the same size, their differences are profound. Venus and Earth experienced vastly different evolutionary pathways resulting in unexplained differences in atmospheric composition and dynamics, as well as in geophysical processes of the planetary surfaces and interiors. Understanding when and why the evolutionary pathways of Venus and Earth diverged is key to understanding how terrestrial planets form and how their atmospheres and surfaces evolve. Measurements made in situ, within the near-surface or surface environment, are critical to addressing unanswered questions. We have made substantial progress modernizing and maturing pressure vessel technologies to enable science operations in the high temperature and pressure near-surface/surfaceenvironment of Venus.

  17. Surface Modification of Nonwoven fabrics by Atmospheric Brush Plasma

    Science.gov (United States)

    Oksuz, Lutfi; Uygun, Emre; Bozduman, Ferhat; Yurdabak Karaca, Gozde; Asan, Orkun Nuri; Uygun Oksuz, Aysegul

    2017-10-01

    Polypropylene nonwoven fabrics (PPNF) are used in disposable absorbent articles, such as diapers, feminine care products, wipes. PPNF need to be wettable by water or aqueous-based liquid. Plasma surface treatment/modification has turned out to be a well-accepted method since it offers superior surface property enhancement than other chemical methods. The cold plasma brush can most efficiently use the discharge power as well as the plasma gas for material and surface treatment. The very low power consumption of such an atmospheric argon plasma brush provides many unique advantages in practical application. The purpose of this study was to reveal the effectiveness of non-thermal atmospheric plasma brush in surface wettability and modification of two different nonwoven surfaces.

  18. Robotic Exploration of the Surface and Atmosphere of Venus

    Science.gov (United States)

    Landis, Geoffrey A.

    2004-01-01

    Venus, the "greenhouse planet", is a scientifically fascinating place. In many ways it can be considered "Earth's evil twin." A huge number of important scientific questions remain to be answered: 1) Before the runaway greenhouse effect, was early Venus temperate? 2) Did Venus once have an ocean? 3) What causes the geological resurfacing of the planet? 4) Is Venus still geologically active? 5) What is the "snow" on Venus mountaintops? 6) Can we learn about Earth's climate from Venus? 7) Is the atmosphere of Venus suitable for life? To address these and other scientific questions, a robotic mission to study the surface and atmosphere of Venus has been designed. The mission includes both surface robots, designed with an operational lifetime of 90 days on the surface of Venus, and also solar-powered airplanes to probe the middle atmosphere. At 450 Celsius, and with 90 atmospheres of pressure of carbon-dioxide atmosphere, the surface of Venus is a hostile place for operation of a probe. This paper will present the mission design, discuss the technology options for materials, power systems, electronics, and instruments, and present a short summary of the mission.

  19. Magnetic field-related heating instabilities in the surface layers of the sun and stars

    Science.gov (United States)

    Ferrari, A.; Rosner, R.; Vaiana, G. S.

    1982-01-01

    The stability of a magnetized low-density plasma to current-driven filamentation instabilities is investigated and the results are applied to the surface layers of stars. Unlike previous studies, the initial (i.e., precoronal) state of the stellar surface atmosphere is taken to be a low-density, optically thin magnetized plasma in radiative equilibrium. The linear analysis shows that the surface layers of main-sequence stars (including the sun) which are threaded by magnetic fields are unstable; the instabilities considered lead to structuring perpendicular to the ambient magnetic fields. These results suggest that relatively modest surface motions, in conjunction with the presence of magnetic fields, suffice to account for the presence of inhomogeneous chromospheric and coronal plasma overlying a star's surface.

  20. Monitoring of the atmospheric ozone layer and natural ultraviolet radiation: Annual report 2011

    Energy Technology Data Exchange (ETDEWEB)

    Svendby, T.M.; Myhre, C.L.; Stebel, K.; Edvardsen, K; Orsolini, Y.; Dahlback, A.

    2012-07-01

    This is an annual report describing the activities and main results of the monitoring programme: Monitoring of the atmospheric ozone layer and natural ultraviolet radiation for 2011. 2011 was a year with generally low ozone values above Norway. A clear decrease in the ozone layer above Norway during the period 1979-1997 stopped after 1998 and the ozone layer above Norway seems now to have stabilized.(Author)

  1. Atomic and molecular layer deposition for surface modification

    Science.gov (United States)

    Vähä-Nissi, Mika; Sievänen, Jenni; Salo, Erkki; Heikkilä, Pirjo; Kenttä, Eija; Johansson, Leena-Sisko; Koskinen, Jorma T.; Harlin, Ali

    2014-06-01

    Atomic and molecular layer deposition (ALD and MLD, respectively) techniques are based on repeated cycles of gas-solid surface reactions. A partial monolayer of atoms or molecules is deposited to the surface during a single deposition cycle, enabling tailored film composition in principle down to molecular resolution on ideal surfaces. Typically ALD/MLD has been used for applications where uniform and pinhole free thin film is a necessity even on 3D surfaces. However, thin - even non-uniform - atomic and molecular deposited layers can also be used to tailor the surface characteristics of different non-ideal substrates. For example, print quality of inkjet printing on polymer films and penetration of water into porous nonwovens can be adjusted with low-temperature deposited metal oxide. In addition, adhesion of extrusion coated biopolymer to inorganic oxides can be improved with a hybrid layer based on lactic acid.

  2. Nanoshells made easy: improving Au layer growth on nanoparticle surfaces.

    Science.gov (United States)

    Brinson, Bruce E; Lassiter, J Britt; Levin, Carly S; Bardhan, Rizia; Mirin, Nikolay; Halas, Naomi J

    2008-12-16

    The growth of a continuous, uniform Au layer on a dielectric nanoparticle is the critical step in the synthesis of nanoparticles such as nanoshells or nanorice, giving rise to their unique geometry-dependent plasmon resonant properties. Here, we report a novel, streamlined method for Au layer metallization on prepared nanoparticle surfaces using carbon monoxide as the reducing agent. This approach consistently yields plasmonic nanoparticles with highly regular shell layers and is immune to variations in precursor or reagent preparation. Single particle spectroscopy combined with scanning electron microscopy reveal that thinner, more uniform shell layers with correspondingly red-shifted optical resonances are achievable with this approach.

  3. Atmospheric Boundary Layer Characteristics during BOBMEX-Pilot ...

    Indian Academy of Sciences (India)

    Pilot experiment are reported. Surface meteorological data were acquired continuously through an automatic weather monitoring system and manually every three hours. High resolution radiosondes were launched to obtain the vertical thermal ...

  4. Some aspects of atmospheric dispersion in the stratified atmospheric boundary layer over homogeneous terrain

    DEFF Research Database (Denmark)

    Gryning, Sven-Erik

    1999-01-01

    The ability to simulate atmospheric dispersion with models developed for applied use under stable atmospheric stability conditions is discussed. The paper is based on model simulations of three experimental data sets reported in the literature. The Hanford data set covered weakly stable conditions......, the Prairie Grass experiments covered both weakly stable and very stable atmospheric conditions, and the Lillestrom experiment was carried out during very stable conditions. Simulations of these experiments reported in the literature for eight different models are discussed. Applied models based...

  5. Heat and Moisture Transport in the Atmospheric Boundary Layer.

    Science.gov (United States)

    1987-01-05

    upwind profile is linea , then it follows from (4. 1Oa) that, if the variation of wind speed over the hill height is small, i.e. (4.23a) HdU,’dz /U(0) o 1...Foldvick (1962), S -S (2.6a) or algebraically : S - SO (h m/Z) where N0 and U are the values at the height hm of the mid- dle layer, and hi is the vertical...systern does not present problems either by hand or by mac hine or b\\ ., n. -hic algebra program, such as MAKCYMA. Our first goal following the Interim I

  6. Whisker Formation On Galvanic Tin Surface Layer

    Directory of Open Access Journals (Sweden)

    Radanyi A.L.

    2015-06-01

    Full Text Available The present work reports the effect of substrate composition, thickness of the tin electroplate and its morphology on pressure-induced tin whisker formation. Pure tin deposits of different thickness were obtained on a copper and brass substrates using methane sulfonic industrial bath. The deposits were compressed by a steel bearing ball forming imprint on the surface. The microstructure of tin whiskers obtained at the boundary of each imprint, their length and number were studied using both light and scanning electron microscopy. It was shown that the most intensive formation and growth of whiskers was observed in the first two hours. In general, brass substrate was shown to be more prone to whisker formation than copper independently of the tin coating thickness. The results have been compared with industrial bright tin finish on control unit socket leads and proposals have been made as to modification of the production process in order to minimize the risk of whiskering.

  7. Variability in the summertime coastal marine atmospheric boundary-layer off California, USA

    Science.gov (United States)

    Ström, Linda; Tjernström, Michael

    2004-01-01

    An analysis of boundary-layer structure and surface-layer turbulence from measurements off the California coast is presented from data collected by research aircraft during two field experiments: the Coastal Waves 1996 (CW96) and the Monterey Area Ship Track (MAST) experiments. CW96 covers the near-coast region, in particular in the vicinity of major headlands, whereas MAST extends offshore. Along the US west coast, coastal modification of the along-coast flow occurs on two main horizontal scales. Firstly, a large-scale variability is due to the interplay between the shallow near-coast marine atmospheric boundary-layer (MABL) and the coastal terrain, typically higher than the MABL depth. The MABL depth decreases smoothly towards the coast while the wind speed increases to a coastal jet in response to the sloping MABL inversion. Secondly, the flow is affected by supercritical flow dynamics. As the wind speed increases and the MABL depth decreases towards the coast, the MABL flow becomes supercritical in a shallow-water sense. As supercritical shallow-water flow interacts with major headlands, expansion fans form, affecting both the wind speed and the MABL depth. The combination of CW96 and MAST data reveals significant differences between the flow along the coast and that far offshore. MABL winds are stronger near the coast whereas aloft the winds are weaker than offshore. The near-coast MABL is also better mixed. Turbulence increases towards the coast while the sensible-heat flux decreases and often changes sign, leading to stable stratification near the coast. A length-scale determining the across-coast influence of the expansion fans is defined from simple inviscid and irrotational shallow-water theory. Data from four days of the CW96 experiment show that this simple theory describes the low-level wind speed adequately. Surface-layer turbulence also scales with this simple length-scale, but the results are complicated by upwelling of cold water, giving rise to

  8. Multitechnique characterisation of 304L surface states oxidised at high temperature in steam and air atmospheres

    Science.gov (United States)

    Mamede, Anne-Sophie; Nuns, Nicolas; Cristol, Anne-Lise; Cantrel, Laurent; Souvi, Sidi; Cristol, Sylvain; Paul, Jean-François

    2016-04-01

    In case of a severe accident occurring in a nuclear reactor, surfaces of the reactor coolant system (RCS), made of stainless steel (304L) rich in Cr (>10%) and Ni (8-12%), are oxidised. Fission products (FPs) are released from melt fuel and flow through the RCS. A part of them is deposited onto surfaces either by vapour condensation or by aerosol deposition mechanisms. To be able to understand the nature of interactions between these FPs and the RCS surfaces, a preliminary step is to characterize the RSC surface states in steam and air atmosphere at high temperatures. Pieces of 304L stainless steel have been treated in a flow reactor at two different temperatures (750 °C and 950 °C) for two different exposition times (24 h and 72 h). After surfaces analysing by a unique combination of surface analysis techniques (XPS, ToF-SIMS and LEIS), for 304L, the results show a deep oxide scale with multi layers and the outer layer is composed of chromium and manganese oxides. Oxide profiles differ in air or steam atmosphere. Fe2O3 oxide is observed but in minor proportion and in all cases no nickel is detected near the surface. Results obtained are discussed and compared with the literature data.

  9. Multitechnique characterisation of 304L surface states oxidised at high temperature in steam and air atmospheres

    Energy Technology Data Exchange (ETDEWEB)

    Mamede, Anne-Sophie, E-mail: anne-sophie.mamede@ensc-lille.fr [University Lille, CNRS, ENSCL, Centrale Lille, University Artois, UMR 8181 – UCCS – Unité de Catalyse et Chimie du Solide, F-59000 Lille (France); Nuns, Nicolas, E-mail: nicolas.nuns@univ-lille1.fr [University Lille, CNRS, ENSCL, Centrale Lille, University Artois, UMR 8181 – UCCS – Unité de Catalyse et Chimie du Solide, F-59000 Lille (France); Cristol, Anne-Lise, E-mail: anne-lise.cristol@ec-lille.fr [University Lille, CNRS, Centrale Lille, Arts et Métiers Paris Tech, FRE 3723 – LML – Laboratoire de Mécanique de Lille, F-59000 Lille (France); Cantrel, Laurent, E-mail: laurent.cantrel@irsn.fr [Institut de Radioprotection et de Sûreté Nucléaire, PSN-RES, Cadarache, Saint Paul lez Durance, 13115 (France); Laboratoire de Recherche Commun IRSN-CNRS-Lille 1: «Cinétique Chimique, Combustion, Réactivité» (C3R), Cadarache, Saint Paul lez Durance, 13115 (France); Souvi, Sidi, E-mail: sidi.souvi@irsn.fr [Institut de Radioprotection et de Sûreté Nucléaire, PSN-RES, Cadarache, Saint Paul lez Durance, 13115 (France); Laboratoire de Recherche Commun IRSN-CNRS-Lille 1: «Cinétique Chimique, Combustion, Réactivité» (C3R), Cadarache, Saint Paul lez Durance, 13115 (France); and others

    2016-04-30

    Graphical abstract: - Highlights: • Mutitechnique characterisation of oxidised 304L. • Oxidation at high temperature under steam and air conditions of 304L stainless steel. • Chromium and manganese oxides formed in the outer layer. • Oxide profiles differ in air or steam atmosphere. - Abstract: In case of a severe accident occurring in a nuclear reactor, surfaces of the reactor coolant system (RCS), made of stainless steel (304L) rich in Cr (>10%) and Ni (8–12%), are oxidised. Fission products (FPs) are released from melt fuel and flow through the RCS. A part of them is deposited onto surfaces either by vapour condensation or by aerosol deposition mechanisms. To be able to understand the nature of interactions between these FPs and the RCS surfaces, a preliminary step is to characterize the RSC surface states in steam and air atmosphere at high temperatures. Pieces of 304L stainless steel have been treated in a flow reactor at two different temperatures (750 °C and 950 °C) for two different exposition times (24 h and 72 h). After surfaces analysing by a unique combination of surface analysis techniques (XPS, ToF-SIMS and LEIS), for 304L, the results show a deep oxide scale with multi layers and the outer layer is composed of chromium and manganese oxides. Oxide profiles differ in air or steam atmosphere. Fe{sub 2}O{sub 3} oxide is observed but in minor proportion and in all cases no nickel is detected near the surface. Results obtained are discussed and compared with the literature data.

  10. Activity of radon ($^{222} $ Rn) in the lower atmospheric surface ...

    Indian Academy of Sciences (India)

    Analysis of one year measurements of in situ radon ( 222 Rn) and its progenies along with surface air temperature, relative humidity and pressure near to the Earth's surface has been carried out for the first time at the National Atmospheric Research Laboratory (NARL, 13.5◦N and 79.2◦E) located in a rural site in Gadanki, ...

  11. 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.

  12. Mechanistic modeling study on process optimization and precursor utilization with atmospheric spatial atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Zhang; He, Wenjie; Duan, Chenlong [State Key Laboratory of Digital Manufacturing Equipment and Technology, School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Chen, Rong, E-mail: rongchen@mail.hust.edu.cn [State Key Laboratory of Digital Manufacturing Equipment and Technology, School of Mechanical Science and Engineering, School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Shan, Bin [State Key Laboratory of Material Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)

    2016-01-15

    Spatial atomic layer deposition (SALD) is a promising technology with the aim of combining the advantages of excellent uniformity and conformity of temporal atomic layer deposition (ALD), and an industrial scalable and continuous process. In this manuscript, an experimental and numerical combined model of atmospheric SALD system is presented. To establish the connection between the process parameters and the growth efficiency, a quantitative model on reactant isolation, throughput, and precursor utilization is performed based on the separation gas flow rate, carrier gas flow rate, and precursor mass fraction. The simulation results based on this model show an inverse relation between the precursor usage and the carrier gas flow rate. With the constant carrier gas flow, the relationship of precursor usage and precursor mass fraction follows monotonic function. The precursor concentration, regardless of gas velocity, is the determinant factor of the minimal residual time. The narrow gap between precursor injecting heads and the substrate surface in general SALD system leads to a low Péclet number. In this situation, the gas diffusion act as a leading role in the precursor transport in the small gap rather than the convection. Fluid kinetics from the numerical model is independent of the specific structure, which is instructive for the SALD geometry design as well as its process optimization.

  13. A methodology for the design and testing of atmospheric boundary layer models for wind energy applications

    Directory of Open Access Journals (Sweden)

    J. Sanz Rodrigo

    2017-02-01

    Full Text Available The GEWEX Atmospheric Boundary Layer Studies (GABLS 1, 2 and 3 are used to develop a methodology for the design and testing of Reynolds-averaged Navier–Stokes (RANS atmospheric boundary layer (ABL models for wind energy applications. The first two GABLS cases are based on idealized boundary conditions and are suitable for verification purposes by comparing with results from higher-fidelity models based on large-eddy simulation. Results from three single-column RANS models, of 1st, 1.5th and 2nd turbulence closure order, show high consistency in predicting the mean flow. The third GABLS case is suitable for the study of these ABL models under realistic forcing such that validation versus observations from the Cabauw meteorological tower are possible. The case consists on a diurnal cycle that leads to a nocturnal low-level jet and addresses fundamental questions related to the definition of the large-scale forcing, the interaction of the ABL with the surface and the evaluation of model results with observations. The simulations are evaluated in terms of surface-layer fluxes and wind energy quantities of interest: rotor equivalent wind speed, hub-height wind direction, wind speed shear and wind direction veer. The characterization of mesoscale forcing is based on spatially and temporally averaged momentum budget terms from Weather Research and Forecasting (WRF simulations. These mesoscale tendencies are used to drive single-column models, which were verified previously in the first two GABLS cases, to first demonstrate that they can produce similar wind profile characteristics to the WRF simulations even though the physics are more simplified. The added value of incorporating different forcing mechanisms into microscale models is quantified by systematically removing forcing terms in the momentum and heat equations. This mesoscale-to-microscale modeling approach is affected, to a large extent, by the input uncertainties of the mesoscale

  14. Formation of oxygen complexes in controlled atmosphere at surface ...

    Indian Academy of Sciences (India)

    cleaned under vacuum up to 1273 K. Specific functional groups, subsequently formed under dry CO2 or O2 atmosphere on the surface of boron-doped and phosphorus-doped glassy carbon samples, were examined using the temperature-programmed desorption method combined with mass spectrometric analysis.

  15. Atmospheric correction for sea surface temperature retrieval from ...

    Indian Academy of Sciences (India)

    An atmospheric correction method has been applied on sea surface temperature (SST) retrieval algorithm using Very High Resolution Radiometer (VHRR) single window channel radiance data onboard Kalpana satellite (K-SAT). The technique makes use of concurrent water vapour fields available from Microwave Imager ...

  16. Dynamical Analysis of the Boundary Layer and Surface Wind Responses to Mesoscale SST Perturbations

    Science.gov (United States)

    2010-02-01

    SST-induced surface wind stress response over the Agul- has Return Current is stronger during the austral winter than during the austral summer...region (Fig. 1). West of here, water enters into the Agulhas Return Current from the Agulhas Current and Agulhas Retroflection south of Africa near...atmospheric boundary layer over the Agulhas Current south of Africa : Composite aircraft observations. J. Geophys. Res., 99, 3297– 3304. ——, and N. Walker, 1988

  17. Double Charged Surface Layers in Lead Halide Perovskite Crystals

    KAUST Repository

    Sarmah, Smritakshi P.

    2017-02-01

    Understanding defect chemistry, particularly ion migration, and its significant effect on the surface’s optical and electronic properties is one of the major challenges impeding the development of hybrid perovskite-based devices. Here, using both experimental and theoretical approaches, we demonstrated that the surface layers of the perovskite crystals may acquire a high concentration of positively charged vacancies with the complementary negatively charged halide ions pushed to the surface. This charge separation near the surface generates an electric field that can induce an increase of optical band gap in the surface layers relative to the bulk. We found that the charge separation, electric field, and the amplitude of shift in the bandgap strongly depend on the halides and organic moieties of perovskite crystals. Our findings reveal the peculiarity of surface effects that are currently limiting the applications of perovskite crystals and more importantly explain their origins, thus enabling viable surface passivation strategies to remediate them.

  18. Atmospheric mercury accumulation and washoff processes on impervious urban surfaces

    Science.gov (United States)

    Eckley, C.S.; Branfireun, B.; Diamond, M.; Van Metre, P.C.; Heitmuller, F.

    2008-01-01

    The deposition and transport of mercury (Hg) has been studied extensively in rural environments but is less understood in urbanized catchments, where elevated atmospheric Hg concentrations and impervious surfaces may efficiently deliver Hg to waterways in stormwater runoff. We determined the rate at which atmospheric Hg accumulates on windows, identified the importance of washoff in removing accumulated Hg, and measured atmospheric Hg concentrations to help understand the relationship between deposition and surface accumulation. The main study location was Toronto, Ontario. Similar samples were also collected from Austin, Texas for comparison of Hg accumulation between cities. Windows provided a good sampling surface because they are ubiquitous in urban environments and are easy to clean/blank allowing the assessment of contemporary Hg accumulation. Hg Accumulation rates were spatially variable ranging from 0.82 to 2.7 ng m-2 d-1 in Toronto and showed similar variability in Austin. The highest accumulation rate in Toronto was at the city center and was 5?? higher than the rural comparison site (0.58 ng m-2 d-1). The atmospheric total gaseous mercury (TGM) concentrations were less than 2?? higher between the rural and urban locations (1.7 ?? 0.3 and 2.7 ?? 1.1 ng m-3, respectively). The atmospheric particulate bound fraction (HgP), however, was more than 3?? higher between the rural and urban sites, which may have contributed to the higher urban Hg accumulation rates. Windows exposed to precipitation had 73 ?? 9% lower accumulation rates than windows sheltered from precipitation. Runoff collected from simulated rain events confirmed that most Hg accumulated on windows was easily removed and that most of the Hg in washoff was HgP. Our results indicate that the Hg flux from urban catchments will respond rapidly to changes in atmospheric concentrations due to the mobilization of the majority of the surface accumulated Hg during precipitation events. ?? 2008 Elsevier

  19. Thin-layer chromatography and mass spectrometry coupled using proximal probe thermal desorption with electrospray or atmospheric pressure chemica lionization

    Energy Technology Data Exchange (ETDEWEB)

    Ovchinnikova, Olga S [ORNL; Van Berkel, Gary J [ORNL

    2010-01-01

    An atmospheric pressure proximal probe thermal desorption sampling method coupled with secondary ionization by electrospray or atmospheric pressure chemical ionization was demonstrated for the mass spectrometric analysis of a diverse set of compounds (dyestuffs, pharmaceuticals, explosives and pesticides) separated on various high-performance thin-layer chromatography plates. Line scans along or through development lanes on the plates were carried out by moving the plate relative to a stationary heated probe positioned close to or just touching the stationary phase surface. Vapors of the compounds thermally desorbed from the surface were drawn into the ionization region of a combined electrospray ionization/atmospheric pressure chemical ionization source where they merged with reagent ions and/or charged droplets from a corona discharge or an electrospray emitter and were ionized. The ionized components were then drawn through the atmospheric pressure sampling orifice into the vacuum region of a triple quadrupole mass spectrometer and detected using full scan, single ion monitoring, or selected reaction monitoring mode. Studies of variable parameters and performance metrics including the proximal probe temperature, gas flow rate into the ionization region, surface scan speed, read-out resolution, detection limits, and surface type are discussed.

  20. Interaction of Atmospheric Turbulence with Blade Boundary Layer Dynamics on a 5MW Wind Turbine using Blade-Boundary-Layer-Resolved CFD with hybrid URANS-LES.

    Energy Technology Data Exchange (ETDEWEB)

    Vijayakumar, Ganesh [National Renewable Energy Lab. (NREL), Golden, CO (United States); Pennsylvania State Univ., University Park, PA (United States); Brasseur, James [Pennsylvania State Univ., University Park, PA (United States); Univ. of Colorado, Boulder, CO (United States); Lavely, Adam; Jayaraman, Balaji; Craven, Brent

    2016-01-04

    We describe the response of the NREL 5 MW wind turbine blade boundary layer to the passage of atmospheric turbulence using blade-boundary-layer-resolved computational fluid dynamics with hybrid URANS-LES modeling.

  1. Multi-parameter detection of atmospheric metal layers by Beijing Na-K lidar

    Science.gov (United States)

    Wang, Jihong; Jiao, Jing; Yang, Guotao

    2017-04-01

    Beijing Na-K lidar has been started running in 2010. This lidar has two laser beams: one dye laser emits a 589-nm laser beam for Na layer detection; the other dye laser emits a 770-nm laser beam for K layer detection. Under similar conditions, the echo signal of K layer is only about 2 orders of magnitude smaller than that of Na layer. This lidar has a sufficient Signal Noise Ratio (SNR). The structure and details of potassium layer can be effectively distinguished from a single original echo. Several examples of co-observation of density of Na and K layer showed some different results with previous studies. This lidar not only can supplement the lack of Na and K layer observation at this latitude region, but also provide evidence for the atmospheric sciences and space environment monitoring.

  2. Initial multi-parameter detection of atmospheric metal layers by Beijing Na-K lidar

    Science.gov (United States)

    Jiao, Jing; Yang, Guotao; Wang, Jihong; Cheng, Xuewu; Du, Lifang; Wang, Zelong; Gong, Wei

    2017-02-01

    Beijing Na-K lidar has been started running in 2010. This lidar has two laser beams: one dye laser emits a 589-nm laser beam for Na layer detection; the other dye laser emits a 770-nm laser beam for K layer detection. Under similar conditions, the echo signal of K layer is only about 2 orders of magnitude smaller than that of Na layer. This lidar has a sufficient Signal Noise Ratio (SNR). The structure and details of potassium layer can be effectively distinguished from a single original echo. Several examples of co-observation of density of Na and K layer showed some different results with previous studies. This lidar not only can supplement the lack of Na and K layer observation at this latitude region, but also provide evidence for the atmospheric sciences and space environment monitoring.

  3. Laser alloying of the plain carbon steel surface layer

    Directory of Open Access Journals (Sweden)

    A. Radziszewska

    2008-07-01

    Full Text Available As an example of the types of features observed after laser alloying, the addition of Ta to mild carbon steel is described. The system is of interest because such alloying is beneficial in improving surface related properties. The paper describes the microstructure and properties (phase and chemical composition, microhardness of the laser alloyed surface layer. In the investigation the optical microscope, the scanning electron microscope (SEM, chemical (EDS microanalysis composition and microhardness testing methods have been used. Specimens of 0,17 %C plain steel were coated with Ta powder layers. The paints containing organic components were used as the binders during deposition of Ta powder layers on the sample surface. The thickness of Ta deposited layers amounted to 0,16 mm. The specimens were then swept through high power (of nominal power 2,5 kW CW CO2 laser radiation at different speeds.The surface alloyed layers varied in microstructure consisted of fiber like Ta2C + γ eutectics, chemical composition and microhardness. The EDS analyses revealed the enrichment of tantalum in the laser alloyed zone (LAZ. The changes of process parameters had an influence on the hardness of alloyed surface layers: by increasing scanning velocity (from 12 mm/s to 20 mm/s and decreasing laser power (from 1,8 kW to 1,35 kW, the hardness diminished. The wear tests were also carried out which showed that laser alloying of plain carbon steel surface layer led to improvement of their wear resistance.

  4. Extreme Vertical Gusts in the Atmospheric Boundary Layer

    Science.gov (United States)

    2015-07-01

    it applies to the Southern hemisphere . Terrain, latitude, surface heating and moisture supply all have major effects on their behaviour. The cold...unrealistically severe at low altitudes. This is thought to be because, outside of specific meteorological phenomena (thunder storms, mountain waves and...paper is to promote discussion within the meteorological and aeronautical research communities as to whether this contention is correct. To facilitate

  5. 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

  6. 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

  7. Surface layer temperature inversion in the Bay of Bengal: Main characteristics and related mechanisms

    Digital Repository Service at National Institute of Oceanography (India)

    Pankajakshan, T.; Suresh, I.; Gautham, S.; PrasannaKumar, S.; Lengaigne, M.; Rao, R.R.; Neetu, S.; Hegde, A.

    as that of the atmospheric forcing, SLTI is a major contributor to the SST variability and strongly contributes to damp the effect of winter cooling in this region. Thus SLTI acts to “warm” the upper ocean layer during “winter cooling” in the northern BoB. 6. Summary... temperature by entrainment and vertical mixing of warm subsurface water into the mixed layer [de Boyer Montégut et al., 2007], and have, therefore, been suggested to have a significant impact on surface temperature during winter, by damping the effect...

  8. Atomic and molecular layer deposition for surface modification

    Energy Technology Data Exchange (ETDEWEB)

    Vähä-Nissi, Mika, E-mail: mika.vaha-nissi@vtt.fi [VTT Technical Research Centre of Finland, PO Box 1000, FI‐02044 VTT (Finland); Sievänen, Jenni; Salo, Erkki; Heikkilä, Pirjo; Kenttä, Eija [VTT Technical Research Centre of Finland, PO Box 1000, FI‐02044 VTT (Finland); Johansson, Leena-Sisko, E-mail: leena-sisko.johansson@aalto.fi [Aalto University, School of Chemical Technology, Department of Forest Products Technology, PO Box 16100, FI‐00076 AALTO (Finland); Koskinen, Jorma T.; Harlin, Ali [VTT Technical Research Centre of Finland, PO Box 1000, FI‐02044 VTT (Finland)

    2014-06-01

    Atomic and molecular layer deposition (ALD and MLD, respectively) techniques are based on repeated cycles of gas–solid surface reactions. A partial monolayer of atoms or molecules is deposited to the surface during a single deposition cycle, enabling tailored film composition in principle down to molecular resolution on ideal surfaces. Typically ALD/MLD has been used for applications where uniform and pinhole free thin film is a necessity even on 3D surfaces. However, thin – even non-uniform – atomic and molecular deposited layers can also be used to tailor the surface characteristics of different non-ideal substrates. For example, print quality of inkjet printing on polymer films and penetration of water into porous nonwovens can be adjusted with low-temperature deposited metal oxide. In addition, adhesion of extrusion coated biopolymer to inorganic oxides can be improved with a hybrid layer based on lactic acid. - Graphical abstract: Print quality of a polylactide film surface modified with atomic layer deposition prior to inkjet printing (360 dpi) with an aqueous ink. Number of printed dots illustrated as a function of 0, 5, 15 and 25 deposition cycles of trimethylaluminum and water. - Highlights: • ALD/MLD can be used to adjust surface characteristics of films and fiber materials. • Hydrophobicity after few deposition cycles of Al{sub 2}O{sub 3} due to e.g. complex formation. • Same effect on cellulosic fabrics observed with low temperature deposited TiO{sub 2}. • Different film growth and oxidation potential with different precursors. • Hybrid layer on inorganic layer can be used to improve adhesion of polymer melt.

  9. Titan's surface-atmosphere system before and after Huygens

    Science.gov (United States)

    Lunine, Jonathan I.

    2015-04-01

    Speculation about the nature of Titan's surface-atmosphere interactions goes back to the discovery of methane in its atmosphere in 1943 but beginning in the early 1970's surface models began to grapple more quantitatively with the source of methane and its instability in the atmosphere. The role of molecular nitrogen in the atmosphere was first quantitatively considered at that time as well. The Voyager 1 flyby put a thick atmosphere of molecular nitrogen and methane on an observational footing, and made an atmospheric descent probe quite feasible. The measured high methane humidity made seas of methane and possibly other constituents an attractive possible source of methane and sink of its photolytic products, influencing the choice of instruments for a descent probe. At the time of Huygens' actual descent to the surface, global seas had been ruled out, and the Cassini Orbiter was just beginning to gather imaging and radar data of the surface. The fluvial nature of the Huygens landing site and presence of volatiles just below the surface were important discoveries of Huygens itself. Together with Cassini, Huygens painted a picture of a cryogenic desert with occasional violent methane rainstorms feeding streams that tumble pebbles of ice and organics downhill, the whole surrounded by dunes whose organic-rich particles are harvested from the chemical conversion of methane to more refractory compounds high in the atmosphere. And yet many mysteries remain. The large bodies of liquid methane are restricted to high latitudes. Most of the river valleys seen in Cassini radar data seem to run down to nowhere. And the ultimate source and replenishment of methane, although seemingly more strongly tied to the interior than before Cassini-Huygens, remain unresolved. Huygens gave us the only imaging of Titan's surface with a resolution good enough to follow fluvial processes all the way from the contextual geology, to channels, to the stream debris washed out into the plains

  10. Atmospheric Microplasma Application for Surface Modification of Biomaterials

    Science.gov (United States)

    Shimizu, Kazuo; Fukunaga, Hodaka; Tatematsu, Shigeki; Blajan, Marius

    2012-11-01

    Atmospheric microplasma has been intensively studied for applications in various fields, since in this technology the generated field is only 1 kV (approx) under atmospheric pressure and a dielectric barrier discharge gap of 10 to 100 µm. A low discharge voltage atmospheric plasma process is an economical and effective solution for various applications such as indoor air control including sterilization, odor removal, and surface treatment, and would be suitable for medical applications in the field of plasma life sciences. In this paper, we present the application of microplasma for the surface treatment of materials used in medical fields. Moreover, a biomaterial composed of L-lactic acid is used in experiments, which can be biodecomposed in the human body after medical operations. The surface modification process was carried out with active species generated between the microplasma electrodes, which were observed by emission spectrometry. Microplasma treatment of a polymer sheet using Ar as the process gas decreased the contact angle of a water droplet at the surface of the polymer from 78.3 to 45.6° in 10 s, indicating improved surface adhesive characteristics.

  11. Application of the Remotely Piloted Aircraft (RPA) 'MASC' in Atmospheric Boundary Layer Research

    Science.gov (United States)

    Wildmann, Norman; Bange, Jens

    2014-05-01

    The remotely piloted aircraft (RPA) MASC (Multipurpose Airborne Sensor Carrier) was developed at the University of Tübingen in cooperation with the University of Stuttgart, University of Applied Sciences Ostwestfalen-Lippe and 'ROKE-Modelle'. Its purpose is the investigation of thermodynamic processes in the atmospheric boundary layer (ABL), including observations of temperature, humidity and wind profiles, as well as the measurement of turbulent heat, moisture and momentum fluxes. The aircraft is electrically powered, has a maximum wingspan of 3.40 m and a total weight of 5-8 kg, depending on battery- and payload. The standard meteorological payload consists of temperature sensors, a humidity sensor, a flow probe, an inertial measurement unit and a GNSS. In normal operation, the aircraft is automatically controlled by the ROCS (Research Onboard Computer System) autopilot to be able to fly predefined paths at constant altitude and airspeed. Since 2010 the system has been tested and improved intensively. In September 2012 first comparative tests could successfully be performed at the Lindenberg observatory of Germany's National Meteorological Service (DWD). In 2013, several campaigns were done with the system, including fundamental boundary layer research, wind energy meteorology and assistive measurements to aerosol investigations. The results of a series of morning transition experiments in summer 2013 will be presented to demonstrate the capabilities of the measurement system. On several convective days between May and September, vertical soundings were done to record the evolution of the ABL in the early morning, from about one hour after sunrise, until noon. In between the soundings, flight legs of up to 1 km length were performed to measure turbulent statistics and fluxes at a constant altitude. With the help of surface flux measurements of a sonic anemometer, methods of similarity theory could be applied to the RPA flux measurements to compare them to

  12. Synthesis and characterization of macromolecular layers grafted to polymer surfaces

    Science.gov (United States)

    Burtovyy, Oleksandr

    The composition and behavior of surfaces and interfaces play a pivotal role in dictating the overall efficiency of the majority of polymeric materials and devices. Surface properties of the materials can be altered using surface modification techniques. It is necessary to highlight that successful methods of surface modification should affect only the upper layer of the polymer material without changing bulk properties. The processes must introduce new functionalities to the surface, optimize surface roughness, lubrication, hydrophobicity, hydrophilicity, adhesion, conductivity, and/or biocompatibility. Research presented in this dissertation is dedicated to the synthesis, characterization, and application of thin macromolecular layers anchored to polymer substrates. Specifically, attachment of functional polymers via a "grafting to" approach has been extensively studied using PET and nylon model substrates. First, poly(glycidyl methacrylate) was used to introduce permanent functionalities to the model substrates by anchoring it to model films. Then, three different functional polymers were grafted on top of the previous layer. As one part of this study, the temperature and time dependence of grafting functional layers were studied. The surface coverage by hydrophobic polymer was determined from experimental data and predicted by a model. In general, the model has a high degree of predictive capability. Next, surface modification of polymeric fibers and membranes is presented as an important application of the polymer thin layers targeted in the study. Specifically, the procedures developed for surface modification of model substrates was employed for modification of PET, nylon, and cotton fabrics as well as PET track-etched membranes. Since epoxy groups are highly reactive in various chemical reactions, the approach becomes virtually universal, allowing both various surfaces and end-functionalized macromolecules to be used in the grafted layer synthesis. PET

  13. Effects of solar eclipses in the surface atmosphere

    Science.gov (United States)

    Chernogor, L. F.

    2008-08-01

    The results of single-type optical observations, analysis, and comparison of dynamic characteristics of the effects in the surface atmosphere that accompanied four partial solar eclipses (August 11, 1999; May 31, 2003; October 3, 2005; March 29, 2006) near the city of Kharkiv (Ukraine) are presented. The effects observed in the morning, near-noon, and afternoon hours differed markedly. During the solar eclipses, the temperature of the surface atmosphere decreased by 1.3 7.3°. It was detected that, when the maximum value of the occultation function changed from 0.24 to 0.73, the standard deviation of solar-limb displacement σ S decreased by 0.14″ and 0.68″, respectively. The time of convection development was found to be 15 16 min. The parameters of dynamic processes in the surface atmosphere have been calculated and the parameters of mechanical and thermal turbulence have been estimated from the results of measurements of the statistical characteristics of the level of solar-limb tremor with invocation of theoretical relations. The solar eclipses were accompanied by quasi-periodic processes in the atmosphere, which were most likely associated with the generation and propagation of internal gravity waves.

  14. The surface layer observed by a high-resolution sodar at DOME C, Antarctica

    Directory of Open Access Journals (Sweden)

    Stefania Argentini

    2014-01-01

    Full Text Available One year field experiment has started on December 2011 at the French - Italian station of Concordia at Dome C, East Antarctic Plateau. The objective of the experiment is the study of the surface layer turbulent processes under stable/very stable stratifications, and the mechanisms leading to the formation of the warming events. A sodar was improved to achieve the vertical/time resolution needed to study these processes. The system, named Surface Layer sodar (SL-sodar, may operate both in high vertical resolution (low range and low vertical resolution (high range modes. In situ turbulence and radiation measurements were also provided in the framework of this experiment. A few preliminary results, concerning the standard summer diurnal cycle, a summer warming event, and unusually high frequency boundary layer atmospheric gravity waves are presented.

  15. Investigation of the atmospheric boundary layer characteristics on gust factor for the calculation of wind load

    Science.gov (United States)

    Ghanadi, Farzin; Emes, Matthew; Yu, Jeremy; Arjomandi, Maziar; Kelso, Richard

    2017-06-01

    Dynamic amplification and gust effects from turbulence can increase wind loads significantly over and above the static wind loads that have been used for heliostat design. This paper presents the results of analyzing the relationship between gust factor and turbulence intensity within the atmospheric boundary layer (ABL) based on the high fidelity measurements of wind velocity at the SLTEST facility in the Utah desert. Results showed that there are distinct characteristics of a low roughness ABL that deviate from semi-empirical relationships derived for open country and urban terrains with larger surface roughness heights. The analysis also indicated that gust factor is increased by 2.4% when lowering the gust period from 3s to 1s in the low roughness field experiment ABL, compared to a 3.6% increase in a suburban terrain at a 10m height. Although 3s gust periods are recommended in AS/NZS 1170.2 [1], comparison of gust factor data with a 1s gust period is recommended particularly in high roughness ABLs such as in urban areas, to ensure that buildings are adequately designed to withstand higher frequency gusts. This research proved the strength of the correlation between gust factor and turbulence intensity is dependent on the surface roughness height of the terrain. It is recommended that the coefficient in the previous semi-empirical equation must be adjusted to be fitted to the low roughness desert terrain in the field experiment ABL.

  16. Degradation of the surface of a metasilicate glass due to atmosphere moisture

    Directory of Open Access Journals (Sweden)

    Ervino Carlos Ziemath

    1998-06-01

    Full Text Available Glasses with low silica content are very susceptible to suffer pronounced degradation when exposed to room atmosphere during short times. In this work the results of the degradation of the surface of a metasilicate glass with composition 2Na2O.1CaO.3SiO2 are presented. Optical and scanning electron microscopy observations, X-ray diffraction, infrared and Raman microprobe spectroscopic measurements of the modified surface of this glass show strong evidences that it is formed essentially by a crystalline carbonate layer.

  17. Surface Modification by Atmospheric Pressure Plasma for Improved Bonding

    Science.gov (United States)

    Williams, Thomas Scott

    An atmospheric pressure plasma source operating at temperatures below 150?C and fed with 1.0-3.0 volume% oxygen in helium was used to activate the surfaces of the native oxide on silicon, carbon-fiber reinforced epoxy composite, stainless steel type 410, and aluminum alloy 2024. Helium and oxygen were passed through the plasma source, whereby ionization occurred and ˜10 16 cm-3 oxygen atoms, ˜1015 cm -3 ozone molecules and ˜1016 cm-3 metastable oxygen molecules (O21Deltag) were generated. The plasma afterglow was directed onto the substrate material located 4 mm downstream. Surface properties of the plasma treated materials have been investigated using water contact angle (WCA), atomic force microscopy (AFM), infrared spectroscopy (IR), and x-ray photoelectron spectroscopy (XPS). The work presented herein establishes atmospheric-pressure plasma as a surface preparation technique that is well suited for surface activation and enhanced adhesive bond strength in a variety of materials. Atmospheric plasma activation presents an environmentally friendly alternative to wet chemical and abrasive methods of surface preparation. Attenuated total internal reflection infrared spectroscopy was used to study the aging mechanism of the native oxide on silicon. During storage at ambient conditions, the water contact angle of a clean surface increased from peel ply. After oxygen plasma activation and joining the materials together with epoxy, one observes 100% cohesive failure within the cured film adhesive. Depending on the material, the lap shear strength can be increased several fold over that achieved by either solvent wiping or abrasion. The trends in adhesion with plasma exposure time do not correlate well with surface wetting or roughness; instead they correlate with the fraction of the polymer surface sites that are converted into carboxylic acid groups.

  18. Rough-to-smooth transition of an equilibrium neutral constant stress layer. [atmospheric flow over rough terrain

    Science.gov (United States)

    Logan, E., Jr.; Fichtl, G. H.

    1975-01-01

    A model is proposed for low-level atmospheric flows over terrains of changing roughness length, such as those found at the windward end of landing strips adjoining rough terrain. The proposed model is used to develop a prediction technique for calculating transition wind and shear-stress profiles in the region following surface roughness discontinuity. The model for the transition region comprises two layers: a logarithmic layer and a buffer layer. The flow is assumed to be steady, two-dimensional, and incompressible, with neutral hydrostatic stability. A diagram is presented for a typical wind profile in the transition region, obtained from the logarithmic and velocity defect profiles using shear stress calculated by relevant equations.

  19. Out of Thin Air: Microbial Utilization of Atmospheric Gaseous Organics in the Surface Ocean

    KAUST Repository

    Arrieta, Jesus

    2016-01-20

    Volatile and semi-volatile gas-phase organic carbon (GOC) is a largely neglected component of the global carbon cycle, with poorly resolved pools and fluxes of natural and anthropogenic GOC in the biosphere. Substantial amounts of atmospheric GOC are exchanged with the surface ocean, and subsequent utilization of specific GOC compounds by surface ocean microbial communities has been demonstrated. Yet, the final fate of the bulk of the atmospheric GOC entering the surface ocean is unknown. Our data show experimental evidence of efficient use of atmospheric GOC by marine prokaryotes at different locations in the NE Subtropical Atlantic, the Arctic Ocean and the Mediterranean Sea. We estimate that between 2 and 27% of the prokaryotic carbon demand was supported by GOC with a major fraction of GOC inputs being consumed within the mixed layer. The role of the atmosphere as a key vector of organic carbon subsidizing marine microbial metabolism is a novel link yet to be incorporated into the microbial ecology of the surface ocean as well as into the global carbon budget.

  20. Assessment of surface turbulent fluxes using geostationary satellite surface skin temperatures and a mixed layer planetary boundary layer scheme

    Science.gov (United States)

    Diak, George R.; Stewart, Tod R.

    1989-01-01

    A method is presented for evaluating the fluxes of sensible and latent heating at the land surface, using satellite-measured surface temperature changes in a composite surface layer-mixed layer representation of the planetary boundary layer. The basic prognostic model is tested by comparison with synoptic station information at sites where surface evaporation climatology is well known. The remote sensing version of the model, using satellite-measured surface temperature changes, is then used to quantify the sharp spatial gradient in surface heating/evaporation across the central United States. An error analysis indicates that perhaps five levels of evaporation are recognizable by these methods and that the chief cause of error is the interaction of errors in the measurement of surface temperature change with errors in the assigment of surface roughness character. Finally, two new potential methods for remote sensing of the land-surface energy balance are suggested which will relay on space-borne instrumentation planned for the 1990s.

  1. Surface tension in plasmas related to double layer formation

    Energy Technology Data Exchange (ETDEWEB)

    Popescu, Sebastian; Lozneanu, Erzilia [Al. I. Cuza University, Dept. of Plasma Physics, Iasi (Romania)

    2001-07-01

    Self-organized space charge configurations bordered by electric double layers appear in plasma as the result of the transition into a state characterized by local minimum of the free energy. Considering the self-assemblage process of such a complex well-confined space-charge configuration in plasma, known by the name of ball of fire, as a nucleation process, it becomes possible to define an equivalent surface tension for the double layer that covers the core of the ball of fire and to make some predictions for its surface tension coefficient and capacitance. (author)

  2. Seasonality in onshore normalized wind profiles above the surface layer

    DEFF Research Database (Denmark)

    Nissen, Jesper Nielsen; Gryning, Sven-Erik

    2010-01-01

    This work aims to study the seasonal difference in normalized wind speed above the surface layer as it is observed at the 160 m high mast at the coastal site Høvsøre at winds from the sea (westerly). Normalized and stability averaged wind speeds above the surface layer are observed to be 20 to 50...... is to reconstruct the seasonal signal in normalized wind speed and identify the physical process behind. The method proved reasonably successful in capturing the relative difference in wind speed between seasons, indicating that the simulated physical processes are likely candidates to the observed seasonal signal...... in normalized wind speed....

  3. A Study of stable Atmospheric Boundary Layer over highveld South Africa

    Energy Technology Data Exchange (ETDEWEB)

    Luhunga, P; Djolov, G [University of Pretoria (South Africa); Esau, I, E-mail: george.djolov@up.ac.z

    2010-08-15

    The study is part of the South African - Norwegian Programme for Research and Co-operation Phase II 'Analysis and Possibility for Control of Atmospheric Boundary Layer Processes to Facilitate Adaptation to Environmental Changes'. The research strategy of the project is based on 4 legged approach. 1) Application and further development of contemporary atmospheric boundary layer theory. 2) Use of modeling based on large eddy simulation techniques. 3) Experimental investigation of turbulent fluxes. 4) Training and developing academics capable of dealing with the present and new challenges. The paper presents some preliminary results on the micrometeorological variability of the basic meteorological parameters and turbulent fluxes.

  4. A Study of stable Atmospheric Boundary Layer over highveld South Africa

    Science.gov (United States)

    Luhunga, P.; Esau, I.; Djolov, G.

    2010-08-01

    The study is part of the South African - Norwegian Programme for Research and Co-operation Phase II "Analysis and Possibility for Control of Atmospheric Boundary Layer Processes to Facilitate Adaptation to Environmental Changes". The research strategy of the project is based on 4 legged approach. 1) Application and further development of contemporary atmospheric boundary layer theory. 2) Use of modeling based on large eddy simulation techniques. 3) Experimental investigation of turbulent fluxes. 4) Training and developing academics capable of dealing with the present and new challenges. The paper presents some preliminary results on the micrometeorological variability of the basic meteorological parameters and turbulent fluxes.

  5. Influence of atmospheric forcing parameters on land surface simulation

    Science.gov (United States)

    Nayak, H. P.; Mandal, M.; Bhattacharya, A.

    2015-12-01

    The quality of atmospheric forcing plays important role on land surface simulation using decoupled land surface modeling system. In the present study, the influence of the various atmospheric forcing parameters on land surface simulation is assessed through sensitivity experiments. Numerical experiments are conducted towards preparation of land surface analysis for the period Jan-2011 - Dec-2013 using offline 2D-Noah land surface model (LSM) based land data assimilation system (LDAS) over Indian region (5 - 39N, 60 - 100E) hereafter referred as LDASI. The surface temperature, specific humidity, horizontal winds and pressure as atmospheric forcing parameters are derived from Modern-Era Retrospective Analysis for Research and Applications (MERRA). The downward (solar and thermal) radiation and precipitation is obtained from European Centre for Medium Range Forecast (ECMWF) and Tropical Rainfall Measuring Mission (TRMM) respectively. The sensitivity experiments are conducted by introducing perturbation in one atmospheric forcing parameter at a time keeping the other parameters unchanged. Influence of temperature, specific humidity, downward (shortwave and long wave) radiation, rain-rate and wind speed is investigated by conducted 13 numerical experiments. It is observed that the land surface analysis from LDASI is most sensitive to the downward longwave radiation and least sensitive to wind speed. The analysis is also substantially influenced by the surface air temperature. The annual mean soil moisture at 5 cm is decreased by 12-15% if the downward long-wave radiation is increased by 20% and it is increased by 15% if the downward long-wave radiation is decreased by 20%. The influence is even more in the Himalayan region but the increase in long-wave radiation leads to increase in soil moisture and similar influence on decrease because downward long-wave radiation leads glacier melting. The annual mean soil temperature in the analysis is increased by 2.2 K if surface

  6. Hypersonic boundary layer stabilization by using a wavy surface

    Science.gov (United States)

    Kirilovskiy, S. V.; Poplavskaya, T. V.

    2017-10-01

    Numerical simulation of hypersonic (M∞=6) flow and evolution of disturbances on a smooth plate and a shallow grooved plate was performed by solving two-dimensional Navier– Stokes equations. Computational soft-ware verification was conducted by comparison with existing data of pressure pulsations on plates surface. It was showed that wavy surface significantly decrease pressure pulsations on plate surface and does not increase the value of mean heat fluxes. Data about effect of wavy surfaces with different form on the disturbances intensity in hypersonic boundary layer was obtained.

  7. LOLAS: an optical turbulence profiler in the atmospheric boundary layer with extreme altitude-resolution

    OpenAIRE

    Avila, R.; Aviles, J. L.; Wilson, R. W.; Chun, M.; Butterley, T.; Carrasco, E.

    2008-01-01

    We report the development and first results of an instrument called Low Layer Scidar (LOLAS) which is aimed at the measurement of optical-turbulence profiles in the atmospheric boundary layer with high altitude-resolution. The method is based on the Generalized Scidar (GS) concept, but unlike the GS instruments which need a 1- m or larger telescope, LOLAS is implemented on a dedicated 40-cm telescope, making it an independent instrument. The system is designed for widely separated double-star...

  8. Towards grid-converged wall-modeled LES of atmospheric boundary layer flows

    Science.gov (United States)

    Yellapantula, Shashank; Vijayakumar, Ganesh; Henry de Frahan, Marc; Churchfield, Matthew; Sprague, Michael

    2017-11-01

    Accurate characterization of incoming atmospheric boundary layer (ABL) turbulence is a critical factor in improving accuracy and predictive nature of simulation of wind farm flows. Modern commercial wind turbines operate in the log layer of the ABL that are typically simulated using wall-modeled large-eddy simulation (WMLES). One of the long-standing issues associated with wall modeling for LES and hybrid RANS-LES for atmospheric boundary layers is the over-prediction of the mean-velocity gradient, commonly referred to as log-layer mismatch. Kawai and Larsson in 2012, identified under-resolution of the near-wall region and the incorrect information received by the wall model as potential causes for the log-layer mismatch in WMLES of smooth-wall boundary-layer flows. To solve the log layer mismatch issue, they proposed linking the wall model to the LES solution at a physical of height of ym, instead of the first grid point. In this study, we extend their wall modeling approach to LES of the rough-wall ABL to investigate issues of log-layer mismatch and grid convergence. This work was funded by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Wind Energy Technologies Office, under Contract No. DE-AC36-08-GO28308 with the National Renewable Energy Laboratory.

  9. Modeling Turbulence Generation in the Atmospheric Surface and Boundary Layers

    Science.gov (United States)

    2015-10-01

    order of kilometers—requiring on the order of 1018 computational cells—would be practically impossible given even today’s supercomputing resources . Thus...fairly easily from web resources . The mnemonics for these variables were selected as follows: LATTNE is latitude of the site of interest in degrees north...w(t)] = ∞∫ 0 e− stw (t) dt = W (s). (4.4) Standard transform and inverse-transform tables will be used to provide the results needed to express the

  10. Observations of the atmospheric surface layer parameters over a ...

    Indian Academy of Sciences (India)

    The spectra of the wind components and temperature indicated decrease in spectral power by one order in magnitude during the eclipse period. The rate of dissipation of turbulent kinetic energy is found to decrease by more than one order during the eclipse period. The stability parameter showed a change from unstable to ...

  11. The composition of the atmosphere at the surface of Mars

    Science.gov (United States)

    Owen, T.; Biemann, K.; Biller, J. E.; Lafleur, A. L.; Rushneck, D. R.; Howarth, D. W.

    1977-01-01

    The current status is summarized of investigations of the composition of the Martian atmosphere, in which use was made of the mass spectrometers that function as the analytical component of the molecular analysis experiments on the two Viking landers. The following points seem well established: N2, Ar-40, Ne, Kr, Xe, and the primordial isotope of Ar are present. The present atmosphere of Mars represents only a small fraction of the total amount of volatiles outgassed by the planet, so that high surface pressure and abundant water may have been present. The noble gases in the Martian atmosphere exhibit a relative abundance pattern similar to that in the earth's atmosphere and (except for Xe) to that in the primordial component of meteorites. The existence of a 'planetary component' is thus proven, supporting the arguments of those who favor a fractionation of noble gases prior to the formation of the planets. In spite of these similarities, the isotopic ratios of nitrogen, argon, and xenon indicate that the histories of the Martian and the earth's atmospheres have been very different.

  12. An Estimation of Turbulent Kinetic Energy and Energy Dissipation Rate Based on Atmospheric Boundary Layer Similarity Theory

    Science.gov (United States)

    Han, Jongil; Arya, S. Pal; Shaohua, Shen; Lin, Yuh-Lang; Proctor, Fred H. (Technical Monitor)

    2000-01-01

    Algorithms are developed to extract atmospheric boundary layer profiles for turbulence kinetic energy (TKE) and energy dissipation rate (EDR), with data from a meteorological tower as input. The profiles are based on similarity theory and scalings for the atmospheric boundary layer. The calculated profiles of EDR and TKE are required to match the observed values at 5 and 40 m. The algorithms are coded for operational use and yield plausible profiles over the diurnal variation of the atmospheric boundary layer.

  13. An observational investigation of transitory turbulence in the atmospheric boundary layer

    Science.gov (United States)

    Jensen, Derek D.

    Within the atmospheric boundary layer (ABL), atmospheric fluid flow is in a constant state of transition in both time and space. Under calm conditions through the mid-daytime hours and over quasi-uniform terrain, the temporal and spatial evolution of the atmosphere is gradual. The structure and governing equations are well understood, allowing for numerical models to accurately forecast the evolution of the ABL. Under nocturnal conditions, the atmospheric processes are more complicated, yet numerical models still perform reasonably well. When changes in the state of the atmosphere occur abruptly, whether in time or space, the fidelity of most numerical weather models diminishes appreciably. This occurs because many of the simplifying assumptions intrinsic in most numerical models are no longer valid. The objective of this dissertation is to use observational data collected within such transitions to gain more insight into the mechanisms responsible for the evolution of the rapidly evolving ABL. First, near-surface turbulence data are used to study countergradient heat fluxes that occur through the evening transition. The countergradient heat flux may be produced by the sign change of the sensible heat flux preceding the sign change of the local temperature gradient and vice versa. The phenomenon is studied by considering the budget equations of both temperature and sensible heat flux. The behaviour of the countergradient heat flux is governed by the surface and subsurface characteristics. The duration of the countergradient flux may be prognosed by considering a ratio of terms in the heat flux budget equation evaluated during the mid- to late afternoon. Next, data collected over an arid shallow slope (2-4°) are used to study the structure and onset of katabatic flow through the evening transition. The katabatic onset, jet velocity and jet height all show a large degree of interdiurnal variability. The slope-aligned budgets of momentum and potential temperature are

  14. Formation of oxygen complexes in controlled atmosphere at surface ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 29; Issue 5. Formation of oxygen complexes in controlled atmosphere at surface of doped glassy carbon. Aleksandra A Perić-Grujić Tatjana M Vasiljević Olivera M Nešković Miomir V Veljković Zoran V Laušević Mila D Laušević. Ceramics and Glasses Volume 29 Issue ...

  15. Atmospheric Water Harvesting: Role of Surface Wettability and Edge Effect

    KAUST Repository

    Jin, Yong

    2017-06-23

    Atmospheric water is emerging as an important potable water source. The present work experimentally and theoretically investigates water condensation and collection on flat surfaces with contrasting contact angles and contact angle hysteresis (CAH) to elucidate their roles on water mass collection efficiency. The experimental results indicate that a hydrophilic surface promotes nucleation and individual droplets growth, and a surface with a low CAH tends to let a smaller droplet to slide down, but the overall water mass collection efficiency is independent of both surface contact angle and CAH. The experimental results agree well with our theoretical calculations. During water condensation, a balance has to be struck between single droplet growth and droplet density on a surface so as to maintain a constant water droplet surface coverage ratio, which renders the role of both surface wettability and hysteresis insignificant to the ultimate water mass collection. Moreover, water droplets on the edges of a surface grow much faster than those on the non-edge areas and thus dominate the contribution to the water mass collection by the entire surface, directly pointing out the very important role of edge effect on water condensation and collection.

  16. Non-steady dynamics of atmospheric turbulence interaction with wind turbine loadings through blade-boundary-layer-resolved CFD

    Science.gov (United States)

    Vijayakumar, Ganesh

    Modern commercial megawatt-scale wind turbines occupy the lower 15-20% of the atmospheric boundary layer (ABL), the atmospheric surface layer (ASL). The current trend of increasing wind turbine diameter and hub height increases the interaction of the wind turbines with the upper ASL which contains spatio-temporal velocity variations over a wide range of length and time scales. Our interest is the interaction of the wind turbine with the energetic integral-scale eddies, since these cause the largest temporal variations in blade loadings. The rotation of a wind turbine blade through the ABL causes fluctuations in the local velocity magnitude and angle of attack at different sections along the blade. The blade boundary layer responds to these fluctuations and in turn causes temporal transients in local sectional loads and integrated blade and shaft bending moments. While the integral scales of the atmospheric boundary layer are ˜ O(10--100m) in the horizontal with advection time scales of order tens of seconds, the viscous surface layer of the blade boundary layer is ˜ O(10 -- 100 mum) with time scales of order milliseconds. Thus, the response of wind turbine blade loadings to atmospheric turbulence is the result of the interaction between two turbulence dynamical systems at extremely disparate ranges of length and time scales. A deeper understanding of this interaction can impact future approaches to improve the reliability of wind turbines in wind farms, and can underlie future improvements. My thesis centers on the development of a computational framework to simulate the interaction between the atmospheric and wind turbine blade turbulence dynamical systems using a two step one-way coupled approach. Pseudo-spectral large eddy simulation (LES) is used to generate a true (equilibrium) atmospheric boundary layer over a flat land with specified surface roughness and heating consistent with the stability state of the daytime lower troposphere. Using the data from the

  17. Discovery of Cellulose Surface Layer Conformation by Nonlinear Vibrational Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Libing; Fu, Li; Wang, Hong-fei; Yang, Bin

    2017-03-14

    Significant questions remain with respect to the structure and polymorphs of cellulose. These include the cellulose surface layers and the bulk crystalline core as well as the conformational differences. The Total Internal Reflection Sum Frequency Generation Vibrational Spectroscopy (TIR-SFG-VS) combined with the conventional SFG-VS (non-TIR) can help to resolve these questions by selectively characterizing the molecular structures of surface layers and the crystalline core of cellulose. From the SFG spectra in the C-H and O-H regions, we found that the surface layers of Avicel are essentially amorphous; while the surface layers of Iβ cellulose are crystalline but with different structural and spectroscopic signatures than that of its crystalline core. This work demonstrates the capacity of TIR and Non-TIR SFG-VS tools in selectively studying the structures and polymorphs of cellulose. In addition, these results also suggest that the assignments of major vibrational peaks for cellulose need to be further determined.

  18. DESIGN AND CALCULATION OF AERODROMECOAING WITH HEATED SURFACE LAYERS

    Directory of Open Access Journals (Sweden)

    Vadim G. Piskunov

    2009-04-01

    Full Text Available  The developed constructions with heated by surface layers for aerodromes and auto roads when developed composition of electroconductive concrete reinforced with chemical electrical conductive fibres being used was researched. The experimentally obtained characteristics of ended conductive concrete reinforced with fibers were presented. Calculation by developed heated construction of shell was made.

  19. Influences of the boundary layer evolution on surface ozone ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 121; Issue 4. Influences of the boundary layer evolution on surface ozone variations at a tropical rural site in India. K K Reddy M Naja N Ojha P Mahesh S Lal. Volume 121 Issue 4 August 2012 pp 911-922 ...

  20. Body surface adaptations to boundary-layer dynamics

    NARCIS (Netherlands)

    Videler, J.J.

    1995-01-01

    Evolutionary processes have adapted nektonic animals to interact efficiently with the water that surrounds them. Not all these adaptations serve the same purpose. This paper concentrates on reduction of drag due to friction in the boundary layer close to the body surface. Mucus, compliant skins,

  1. Measurement of grassland evaporation using a surface-layer ...

    African Journals Online (AJOL)

    A dual-beam surface-layer scintillometer (SLS) was used to estimate sensible heat flux (H) every 2 min for a path length of either 50 or 101 m, for more than 30 months in a mesic grassland in eastern South Africa. The SLS method relies on Monin-Obukhov similarity theory, the correlation between the laser beam signal ...

  2. Time variant layer control in atmospheric pressure chemical vapor deposition based growth of graphene

    KAUST Repository

    Qaisi, Ramy M.

    2013-04-01

    Graphene is a semi-metallic, transparent, atomic crystal structure material which is promising for its high mobility, strength and transparency - potentially applicable for radio frequency (RF) circuitry and energy harvesting and storage applications. Uniform (same number of layers), continuous (not torn or discontinuous), large area (100 mm to 200 mm wafer scale), low-cost, reliable growth are the first hand challenges for its commercialization prospect. We show a time variant uniform (layer control) growth of bi- to multi-layer graphene using atmospheric chemical vapor deposition system. We use Raman spectroscopy for physical characterization supported by electrical property analysis. © 2013 IEEE.

  3. Layer-by-layer assembly surface modified microbial biomass for enhancing biorecovery of secondary gold.

    Science.gov (United States)

    Zhou, Ying; Zhu, Nengwu; Kang, Naixin; Cao, Yanlan; Shi, Chaohong; Wu, Pingxiao; Dang, Zhi; Zhang, Xiaoping; Qin, Benqian

    2017-02-01

    Enhancement of the biosorption capacity for gold is highly desirable for the biorecovery of secondary gold resources. In this study, polyethylenimine (PEI) was grafted on Shewanella haliotis surface through layer-by-layer assembly approach so as to improve the biosorption capacity of Au(III). Results showed that the relative contribution of amino group to the biosorption of Au(III) was the largest one (about 44%). After successful grafting 1, 2 and 3-layer PEI on the surface of biomass, the biosorption capacity significantly enhanced from 143.8mg/g to 597.1, 559.1, and 536.8mg/g, respectively. Interestingly, the biomass modified with 1-layer PEI exhibited 4.2 times higher biosorption capacity than the untreated control. When 1-layer modified biomass was subjected to optimizing the various conditions by response surface methodology, the theoretical maximum adsorption capacity could reach up to 727.3mg/g. All findings demonstrated that PEI modified S. haliotis was effective for enhancing gold biorecovery. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Atmospheric spatial atomic layer deposition of in-doped ZnO

    NARCIS (Netherlands)

    Illiberi, A.; Scherpenborg, R.; Roozeboom, F.; Poodt, P.

    2014-01-01

    Indium-doped zinc oxide (ZnO:In) has been grown by spatial atomic layer deposition at atmospheric pressure (spatial-ALD). Trimethyl indium (TMIn), diethyl zinc (DEZ) and deionized water have been used as In, Zn and O precursor, respectively. The metal content of the films is controlled in the range

  5. Impact of aerosol heat radiation absorption on the dynamics of an atmospheric boundary layer in equilibrium

    NARCIS (Netherlands)

    Barbaro, E.W.; Vilà-Guerau de Arellano, J.; Krol, M.C.; Holtslag, A.A.M.

    2012-01-01

    The objective of this work is to investigate the influence of the shortwave radiation (SW) absorption by aerosols on the dynamics and heat budget of the atmospheric boundary layer (ABL). This study is relevant for areas characterized by large concentrations of light-absorbing aerosol, which are

  6. Impacts of Aerosol Shortwave Radiation Absorption on the Dynamics of an Idealized Convective Atmospheric Boundary Layer

    NARCIS (Netherlands)

    Wilde Barbaro, E.; Vilà-Guerau de Arellano, J.; Krol, M.C.; Holtslag, A.A.M.

    2013-01-01

    We investigated the impact of aerosol heat absorption on convective atmospheric boundary-layer (CBL) dynamics. Numerical experiments using a large-eddy simulation model enabled us to study the changes in the structure of a dry and shearless CBL in depthequilibrium for different vertical profiles of

  7. Wind Energy-Related Atmospheric Boundary Layer Large-Eddy Simulation Using OpenFOAM: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Churchfield, M.J.; Vijayakumar, G.; Brasseur, J.G.; Moriarty, P.J.

    2010-08-01

    This paper develops and evaluates the performance of a large-eddy simulation (LES) solver in computing the atmospheric boundary layer (ABL) over flat terrain under a variety of stability conditions, ranging from shear driven (neutral stratification) to moderately convective (unstable stratification).

  8. Approximate analytical solution to diurnal atmospheric boundary-layer growth under well-watered conditions

    Science.gov (United States)

    The system of governing equations of a simplified slab model of the uniformly-mixed, purely convective, diurnal atmospheric boundary layer (ABL) is shown to allow immediate solutions for the potential temperature and specific humidity as functions of the ABL height and net radiation when expressed i...

  9. Application of a commercial lidar-ceilometer to studies of aerosols in the atmospheric boundary layer

    CSIR Research Space (South Africa)

    Ramkilowan, A

    2015-09-01

    Full Text Available has therefore become of great interest. CSIR/DPSS has acquired and deployed a Vaisala CL51 ceilometer chiefly for the purpose of investigating the vertical distribution of aerosols in the Atmospheric Boundary Layer (ABL) and cloud base height...

  10. Spatial atmospheric atomic layer deposition of InxGayZnzO for thin film transistors

    NARCIS (Netherlands)

    Illiberi, A.; Cobb, B.; Sharma, A.; Grehl, T.; Brongersma, H.; Roozeboom, F.; Gelinck, G.; Poodt, P.

    2015-01-01

    We have investigated the nucleation and growth of InGaZnO thin films by spatial atmospheric atomic layer deposition. Diethyl zinc (DEZ), trimethyl indium (TMIn), triethyl gallium (TEGa), and water were used as Zn, In, Ga and oxygen precursors, respectively. The vaporized metal precursors have been

  11. Stable Atmospheric Boundary Layer Experiment in Spain (SABLES 98) : a report

    NARCIS (Netherlands)

    Cuxart, J.; Yague, C.; Morales, G.; Terradelles, E.; Orbe, J.; Calvo, J.; Vilu-Guerau, de J.; Soler, M.R.; Infante, C.; Buenestado, P.; Espinalt, A.; Jorgensem, H.E.

    2000-01-01

    This paper describes the Stable Atmospheric Boundary Layer Experiment in Spain (SABLES 98), which took place over the northern Spanish plateau comprising relatively flat grassland, in September 1998. The main objectives of the campaign were to study the properties of the mid-latitude stable boundary

  12. Stabilization of Leidenfrost vapour layer by textured superhydrophobic surfaces

    KAUST Repository

    Vakarelski, Ivan Uriev

    2012-09-12

    In 1756, Leidenfrost observed that water drops skittered on a sufficiently hot skillet, owing to levitation by an evaporative vapour film. Such films are stable only when the hot surface is above a critical temperature, and are a central phenomenon in boiling. In this so-called Leidenfrost regime, the low thermal conductivity of the vapour layer inhibits heat transfer between the hot surface and the liquid. When the temperature of the cooling surface drops below the critical temperature, the vapour film collapses and the system enters a nucleate-boiling regime, which can result in vapour explosions that are particularly detrimental in certain contexts, such as in nuclear power plants. The presence of these vapour films can also reduce liquid-solid drag. Here we show how vapour film collapse can be completely suppressed at textured superhydrophobic surfaces. At a smooth hydrophobic surface, the vapour film still collapses on cooling, albeit at a reduced critical temperature, and the system switches explosively to nucleate boiling. In contrast, at textured, superhydrophobic surfaces, the vapour layer gradually relaxes until the surface is completely cooled, without exhibiting a nucleate-boiling phase. This result demonstrates that topological texture on superhydrophobic materials is critical in stabilizing the vapour layer and thus in controlling-by heat transfer-the liquid-gas phase transition at hot surfaces. This concept can potentially be applied to control other phase transitions, such as ice or frost formation, and to the design of low-drag surfaces at which the vapour phase is stabilized in the grooves of textures without heating. © 2012 Macmillan Publishers Limited. All rights reserved.

  13. On the role of large-scale forcings on the development of the atmospheric boundary layer during the BLLAST field campaign

    NARCIS (Netherlands)

    Pietersen, H.P.; Vilà-Guerau de Arellano, J.; Coster, de O.; Boer, van de A.; Hartogensis, O.K.; Pino, D.; Gioli, B.; Durand, P.; Lothon, M.; Lohou, F.; Reuder, J.; Jonassen, M.; Faloona, I.

    2012-01-01

    Guided and constrained by a complete data set of surface and upper-air observations taken during the fifth Intensive Observational Period (IOP-05, 25th June 2011) of the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) experiment, we reconstruct the evolution of the atmospheric boundary

  14. Sensitivity of nocturnal boundary layer temperature to tropospheric aerosol surface radiative forcing under clear-sky conditions

    Science.gov (United States)

    Nair, Udaysankar S.; McNider, Richard; Patadia, Falguni; Christopher, Sundar A.; Fuller, Kirk

    2011-01-01

    Since the middle of the last century, global surface air temperature exhibits an increasing trend, with nocturnal temperatures increasing at a much higher rate. Proposed causative mechanisms include the radiative impact of atmospheric aerosols on the nocturnal boundary layer (NBL) where the temperature response is amplified due to shallow depth and its sensitivity to potential destabilization. A 1-D version of the Regional Atmospheric Modeling System is used to examine the sensitivity of the nocturnal boundary layer temperature to the surface longwave radiative forcing (SLWRF) from urban aerosol loading and doubled atmospheric carbon dioxide concentrations. The analysis is conducted for typical midlatitude nocturnal boundary layer case days from the CASES-99 field experiment and is further extended to urban sites in Pune and New Delhi, India. For the cases studied, locally, the nocturnal SLWRF from urban atmospheric aerosols (2.7-47 W m-2) is comparable or exceeds that caused by doubled atmospheric carbon dioxide (3 W m-2), with the surface temperature response ranging from a compensation for daytime cooling to an increase in the nocturnal minimum temperature. The sensitivity of the NBL to radiative forcing is approximately 4 times higher compared to the daytime boundary layer. Nighttime warming or cooling may occur depending on the nature of diurnal variations in aerosol optical depth. Soil moisture also modulates the magnitude of SLWRF, decreasing from 3 to 1 W m-2 when soil saturation increases from 37% to 70%. These results show the importance of aerosols on the radiative balance of the climate system.

  15. Nucleation and Early Stages of Layer-by-Layer Growth of Metal Organic Frameworks on Surfaces

    Science.gov (United States)

    2015-01-01

    High resolution atomic force microscopy (AFM) is used to resolve the evolution of crystallites of a metal organic framework (HKUST-1) grown on Au(111) using a liquid-phase layer-by-layer methodology. The nucleation and faceting of individual crystallites is followed by repeatedly imaging the same submicron region after each cycle of growth and we find that the growing surface is terminated by {111} facets leading to the formation of pyramidal nanostructures for [100] oriented crystallites, and triangular [111] islands with typical lateral dimensions of tens of nanometres. AFM images reveal that crystallites can grow by 5–10 layers in each cycle. The growth rate depends on crystallographic orientation and the morphology of the gold substrate, and we demonstrate that under these conditions the growth is nanocrystalline with a morphology determined by the minimum energy surface. PMID:26709359

  16. Neutralized wettability effect of superhydrophilic Cr-layered surface on pool boiling critical heat flux

    Energy Technology Data Exchange (ETDEWEB)

    Son, Hong Hyun; Jeong, Ui Ju; Seo, Gwang Hyeok; Jeun, Gyoo Dong; Kim, Sung Joong [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    The former method is deemed challenging due to longer development period and license issue. In this regard, FeCrAl, Cr, and SiC have been received positive attention as ATF coating materials because they are highly resistant to high temperature steam reaction causing massive hydrogen generation. In this study, Cr was selected as a target deposition material on the metal substrate because we found that Cr-layered surface becomes superhydrophilic, favorable to delaying the triggering of the critical heat flux (CHF). Thus in order to investigate the effect of Cr-layered superhydrophilic surfaces (under explored coating conditions) on pool boiling heat transfer, pool boiling experiment was conducted in the saturated deionized water under atmospheric pressure. As a physical vapor deposition (PVD) method, the DC magnetron sputtering technique was introduced to develop Cr-layered nanostructure. As a control variable of DC sputtering, substrate temperature was selected. Surface wettability and nanostructure were analyzed as major surface parameters on the CHF. We believe that highly dense micro/nano structure without nucleation cavities and inner pores neutralized the wettability effect on the CHF. Moreover, superhydrophilic surface with deficient cavity density rather hinders active nucleation. This emphasizes the importance of micro/nano structure surface for enhanced boiling heat transfer.

  17. Double layer of platinum electrodes: Non-monotonic surface charging phenomena and negative double layer capacitance.

    Science.gov (United States)

    Huang, Jun; Zhou, Tao; Zhang, Jianbo; Eikerling, Michael

    2018-01-28

    In this study, a refined double layer model of platinum electrodes accounting for chemisorbed oxygen species, oriented interfacial water molecules, and ion size effects in solution is presented. It results in a non-monotonic surface charging relation and a peculiar capacitance vs. potential curve with a maximum and possibly negative values in the potential regime of oxide-formation.

  18. An observational study of the evolution of the atmospheric boundary-layer over Cabo Frio, Brazil

    Directory of Open Access Journals (Sweden)

    S. H. Franchito

    2007-08-01

    Full Text Available The effect of coastal upwelling on the evolution of the atmospheric boundary layer (ABL in Cabo Frio (Brazil is investigated. For this purpose, radiosounding data collected in two experiments made during the austral summer (upwelling case and austral winter (no upwelling case are analysed. The results show that during the austral summer, cold waters that crop up near the Cabo Frio coast favour the formation of an atmospheric stable layer, which persists during the upwelling episode. Due to the low SSTs, the descending branch of the sea-breeze circulation is located close to the coast, inhibiting the development of a mixed layer mainly during the day. At night, with the reduction of the land-sea thermal contrast the descending motion is weaker, allowing a vertical mixing. The stable ABL favours the formation of a low level jet, which may also contribute to the development of a nocturnal atmospheric mixed layer. During the austral winter, due to the higher SSTs observed near the coast, the ABL is less stable compared with that in the austral summer. Due to warming, a mixed layer is observed during the day. The observed vertical profiles of the zonal winds show that the easterlies at low levels are stronger in the austral summer, indicating that the upwelling modulates the sea-breeze signal, thus confirming model simulations.

  19. Towards wafer-size graphene layers by atmospheric pressure graphitization of silicon carbide.

    Science.gov (United States)

    Emtsev, Konstantin V; Bostwick, Aaron; Horn, Karsten; Jobst, Johannes; Kellogg, Gary L; Ley, Lothar; McChesney, Jessica L; Ohta, Taisuke; Reshanov, Sergey A; Röhrl, Jonas; Rotenberg, Eli; Schmid, Andreas K; Waldmann, Daniel; Weber, Heiko B; Seyller, Thomas

    2009-03-01

    Graphene, a single monolayer of graphite, has recently attracted considerable interest owing to its novel magneto-transport properties, high carrier mobility and ballistic transport up to room temperature. It has the potential for technological applications as a successor of silicon in the post Moore's law era, as a single-molecule gas sensor, in spintronics, in quantum computing or as a terahertz oscillator. For such applications, uniform ordered growth of graphene on an insulating substrate is necessary. The growth of graphene on insulating silicon carbide (SiC) surfaces by high-temperature annealing in vacuum was previously proposed to open a route for large-scale production of graphene-based devices. However, vacuum decomposition of SiC yields graphene layers with small grains (30-200 nm; refs 14-16). Here, we show that the ex situ graphitization of Si-terminated SiC(0001) in an argon atmosphere of about 1 bar produces monolayer graphene films with much larger domain sizes than previously attainable. Raman spectroscopy and Hall measurements confirm the improved quality of the films thus obtained. High electronic mobilities were found, which reach mu=2,000 cm (2) V(-1) s(-1) at T=27 K. The new growth process introduced here establishes a method for the synthesis of graphene films on a technologically viable basis.

  20. Inversion effects on wind and surface pressure in atmospheric front propagation simulation with a hyperbolic model

    Science.gov (United States)

    Yudin, M. S.

    2017-11-01

    In this paper the effects of an inversion layer in a stratified atmosphere on the surface wind speed and pressure are investigated with models based on the compressible Navier-Stokes equations in two dimensions. Artificial compressibility is introduced into the models in order to make the governing equations hyperbolic. For comparison with available simulation data, the physical processes under study are assumed to be adiabatic. Plain orography is considered in surface pressure simulations with a finite-difference version of the model, while surface wind speed effects are estimated in artificial cold front propagation over a hill with a finite-element version of the model. The front surface is described in both models by an equation for advection of a scalar substance, which is solved with a third-order semi-Lagrangian procedure. The results of simulations show various meteorological effects in agreement with observations and in accordance with a theory proposed by Charba [3].

  1. Measurements of atmospheric hydrocarbons and biogenic emission fluxes in the Amazon boundary layer

    Science.gov (United States)

    Zimmerman, P. R.; Greenberg, J. P.; Westberg, C. E.

    1988-01-01

    Tropospheric mixing ratios of methane, C2-C10 hydrocarbons, and carbon monoxide were measured over the Amazon tropical forest near Manaus, Amazonas, Brazil, in July and August 1985. The measurements, consisting mostly of altitude profiles of these gases, were all made within the atmospheric boundary layer up to an altitude of 1000 m above ground level. Data characterize the diurnal hydrocarbon composition of the boundary layer. Biogenic emissions of isoprene control hydroxyl radical concentrations over the forest. Biogenic emission fluxes of isoprene and terpenes are estimated to be 25,000 micrograms/sq m per day and 5600 micrograms/sq m per day, respectively. This isoprene emission is equivalent to 2 percent of the net primary productivity of the tropical forest. Atmospheric oxidation of biogenic isoprene and terpenes emissions from the Amazon forest may account for daily increases of 8-13 ppb for carbon monoxide in the planetary boundary layer.

  2. The Characterization of Atmospheric Boundary Layer Depth and Turbulence in a Mixed Rural and Urban Convective Environment

    Science.gov (United States)

    Hicks, Micheal M.

    A comprehensive analysis of surface-atmosphere flux exchanges over a mixed rural and urban convective environment is conducted at Howard University Beltsville, MD Research Campus. This heterogeneous site consists of rural, suburban and industrial surface covers to its south, east and west, within a 2 km radius of a flux sensor. The eddy covariance method is utilized to estimate surface-atmosphere flux exchanges of momentum, heat and moisture. The attributes of these surface flux exchanges are contrasted to those of classical homogeneous sites and assessed for accuracy, to evaluate the following: (I) their similarity to conventional convective boundary layer (CBL) processes and (II) their representativeness of the surrounding environment's turbulent properties. Both evaluations are performed as a function of upwind surface conditions. In particular, the flux estimates' obedience to spectrum power laws and similarity theory relationships is used for performing the first evaluation, and their ability to close the surface energy balance and accurately model CBL heights is used for the latter. An algorithm that estimates atmospheric boundary layer heights from observed lidar extinction backscatter was developed, tested and applied in this study. The derived lidar based CBL heights compared well with those derived from balloon borne soundings, with an overall Pearson correlation coefficient and standard deviation of 0.85 and 223 m, respectively. This algorithm assisted in the evaluation of the response of CBL processes to surface heterogeneity, by deriving high temporal CBL heights and using them as independent references of the surrounding area averaged sensible heat fluxes. This study found that the heterogeneous site under evaluation was rougher than classical homogeneous sites, with slower dissipation rates of turbulent kinetic energy. Flux measurements downwind of the industrial complexes exhibited enhanced efficiency in surface-atmosphere momentum, heat, and

  3. Atmospheric-Pressure Plasma Cleaning of Contaminated Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Robert F. Hicks; Hans W. Herrmann

    2003-12-15

    The purpose of this project was to demonstrate a practical, environmentally benigh technology for the surface decontamination and decommissioning of radioactive waste. A low temperature, atmospheric pressure plasma has been developed with initial support from the DOE, Environmental Management Sciences Program. This devise selectively etches radioactive metals from surfaces, rendering objects radiation free and suitable for decommissioning. The volatile reaction products are captured on filters, which yields a tremendous reduction in the volume of the waste. The technology shows a great potential for accelerating the clean-up effort for the equipment and structures contaminated with radioactive materials within the DOE complex. The viability of this technology has been demonstrated by selectively and rapidly stripping uranium from stainless steel surfaces at low temperature. Studies on uranium oxide have shown that etch rates of 4.0 microns per minute can be achieved at temperature below 473 K. Over the past three years, we have made numerous improvements in the design of the atmospheric pressure plasma source. We are now able to scale up the plasma source to treat large surface areas.

  4. Nocturnal surface ozone enhancement over Portugal during winter: Influence of different atmospheric conditions

    KAUST Repository

    Kulkarni, Pavan S.

    2016-09-24

    Four distinct nocturnal surface ozone (NSO) enhancement events were observed, with NSO concentration exceeding 80μg/m3, at multiple ozone (O3) monitoring stations (32 sites) in January, November and December between year 2000–2010, in Portugal. The reasonable explanation for the observed bimodal pattern of surface ozone with enhanced NSO concentration during nighttime has to be transport processes, as the surface ozone production ceases at nighttime. Simultaneous measurements of O3 at multiple stations during the study period in Portugal suggest that horizontal advection alone cannot explain the observed NSO enhancement. Thus, detailed analysis of the atmospheric conditions, simulated with the Weather Research and Forecasting (WRF) model, were performed to evaluate the atmospheric mechanisms responsible for NSO enhancement in the region. Simulations revealed that each event occurred as a result of one or the combination of different atmospheric processes such as, passage of a cold front followed by a subsidence zone; passage of a moving surface trough, with associated strong horizontal wind speed and vertical shear; combination of vertical and horizontal transport at the synoptic scale; formation of a low level jet with associated vertical mixing below the jet stream. The study confirmed that large-scale flow pattern resulting in enhanced vertical mixing in the nocturnal boundary layer, plays a key role in the NSO enhancement events, which frequently occur over Portugal during winter months. © 2016 Elsevier Ltd

  5. Surface characterization of the atmospheric contamination of hydrogenated amorphous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Charenton, J.C.; Sacher, E.; McIntyre, N.S.

    1988-01-01

    Hydrogenated amorphous silicon (a-Si:H), plasma deposited under positive substrate bias, is shown to undergo atmospheric contamination after removal from the preparation chamber. The contamination rate follows complex-order kinetics and is over within 10/sup 4/ s. Auger spectroscopy depth profiles, obtained through Ar ion etching, are different than those for substrates self-biased during deposition. The same chemical structures appear to exist as are found on crystalline Si surfaces, as is evident from the fact that, when the a-Si:H surface is etched to the point where the Si:C:O ratios are the same as found on crystalline Si, the surface tensions are identical.

  6. Fourier transform spectrometers for remote sensing of planetary atmospheres and surfaces

    Science.gov (United States)

    Shakun, Alexey; Korablev, Oleg; Moshkin, Boris; Grigoriev, Alexey; Ignatiev, Nikolay; Maslov, Igor; Sazonov, Oleg; Patsaev, Dmitry; Kungurov, Andrey; Santos-Skripko, Alexander; Zharkov, Alexander; Stupin, Igor; Merzlyakov, Dmitry; Makarov, Vladislav; Martinovich, Fedor; Nikolskiy, Yuri; Shashkin, Victor

    2017-12-01

    In planetary research, Fourier transform infrared spectrometers (FTIR) solve a number of important scientific goals related both to the atmosphere and to the surface sounding. For remote orbital measurements, these goals are the thermal sounding of the atmosphere using, in particular, the 15-µm CO2 band, sensitive detections of minor gaseous species and aerosol characterization. FTIR can address similar atmospheric science goals when observing from a planetary surface allowing for better-resolved boundary layer and achieving greater accuracy (longer integration) for minor species detection. For studies of planetary surfaces, characterization of mineralogical composition in a wide IR range including sensitive measurements of hydration of the soil on airless bodies can be done. We outline a family of FTIR instruments dedicated to studies of Mars and the Moon. TIRVIM is a channel of ACS on ExoMars TGO (in orbit around Mars since October 2016). It is a 2-inch interferometer for nadir and solar occultation measurements of Mars' atmosphere. It covers a spectral range of 1.7-17 µm with spectral resolution up to 0.13 cm-1. LUMIS is a similar instrument for Luna-Resource Orbiter (Luna-26) Roscosmos mission dedicated to the search for hydration of the lunar regolith in the 6-µm band. The spectral range of LUMIS is broad (1.7-17 µm), but its sensitivity is optimized for the 4-8 µm region. The spectral resolution is 50 cm-1. We also describe recent developments focused on technical solutions for miniaturized FTIR instruments with a very high spectral resolution (0.05 cm-1 and higher). The prototype targets measurements of minor atmospheric species from the surface of Mars using the Sun tracking. One important task is to provide a high precision of interferometer's mirror movement. Another task is the development of a precise two-coordinate mechanism to seek for and follow the Sun.

  7. Improving Wind Predictions in the Marine Atmospheric Boundary Layer through Parameter Estimation in a Single-Column Model

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jared A.; Hacker, Joshua P.; Delle Monache, Luca; Kosović, Branko; Clifton, Andrew; Vandenberghe, Francois; Rodrigo, Javier Sanz

    2016-12-14

    A current barrier to greater deployment of offshore wind turbines is the poor quality of numerical weather prediction model wind and turbulence forecasts over open ocean. The bulk of development for atmospheric boundary layer (ABL) parameterization schemes has focused on land, partly due to a scarcity of observations over ocean. The 100-m FINO1 tower in the North Sea is one of the few sources worldwide of atmospheric profile observations from the sea surface to turbine hub height. These observations are crucial to developing a better understanding and modeling of physical processes in the marine ABL. In this study, we use the WRF single column model (SCM), coupled with an ensemble Kalman filter from the Data Assimilation Research Testbed (DART), to create 100-member ensembles at the FINO1 location. The goal of this study is to determine the extent to which model parameter estimation can improve offshore wind forecasts.

  8. Strain Relaxation of Graphene Layers by Cu Surface Roughening.

    Science.gov (United States)

    Kang, Jin Hyoun; Moon, Joonhee; Kim, Dong Jin; Kim, Yooseok; Jo, Insu; Jeon, Cheolho; Lee, Jouhahn; Hong, Byung Hee

    2016-10-03

    The surface morphology of copper (Cu) often changes after the synthesis of graphene by chemical vapor deposition (CVD) on a Cu foil, which affects the electrical properties of graphene, as the Cu step bunches induce the periodic ripples on graphene that significantly disturb electrical conduction. However, the origin of the Cu surface reconstruction has not been completely understood yet. Here, we show that the compressive strain on graphene induced by the mismatch of thermal expansion coefficient with Cu surface can be released by forming periodic Cu step bunching that depends on graphene layers. Atomic force microscopy (AFM) images and the Raman analysis show the noticeably longer and higher step bunching of Cu surface under multilayer graphene and the weaker biaxial compressive strain on multilayer graphene compared to monolayer. We found that the surface areas of Cu step bunches under multilayer and monolayer graphene are increased by ∼1.41% and ∼0.77% compared to a flat surface, respectively, indicating that the compressive strain on multilayer graphene can be more effectively released by forming the Cu step bunching with larger area and longer periodicity. We believe that our finding on the strain relaxation of graphene layers by Cu step bunching formation would provide a crucial idea to enhance the electrical performance of graphene electrodes by controlling the ripple density of graphene.

  9. CURIE: A low power X-band, low atmospheric boundary layer doppler radar

    Energy Technology Data Exchange (ETDEWEB)

    Al-Sakka, Hassan; Weill, Alain; Le Gac, Christophe; Ney, Richard; Chardenal, Laurent; Vinson, Jean Paul; Barthes, Laurent [Lab. Atmospheres, Milieux, Observations Spatiales, LATMOS/IPSL, Velizy (France); Dupont, Eric [EDF, R and D, CEREA, Chatou (France)

    2009-06-15

    A new X-band Doppler miniradar, the CURIE radar (Canopy Urban Research on Interactions and Exchanges), mainly adapted to low Atmospheric Boundary Layer ABL sounding has been developed at LATMOS (Laboratoire Atmospheres, Milieux, Observations Spatiales) formerly CETP (Centre d'etude des Environnements Terrestre et Planetaires). After a brief description of the measurement conditions in a turbulent atmosphere, the main characteristics of the new sensor are presented. As an example, we compare CURIE vertical velocity fluctuations with UHF observations to show the vertical velocity measurement validity. As a prospective area of application in clear air, we focus on a first observation of vertical velocity variance which is supposed to be related to entrainment across the inversion layer. As our objective is to study low boundary layers during different atmospheric conditions and since the radar works in the presence of precipitation (as all X-band radar do), we also show vertical rain soundings in the lower part of the ABL and illustrate our findings with results demonstrating comparable reflectivity and precipitation rates as estimated with a disdrometer and with a rain gauge. (orig.)

  10. Surface irregularities of MBE grown cubic GaN layers

    Science.gov (United States)

    Lima, A. P.; Frey, T.; Köhler, U.; Wang, C.; As, D. J.; Schöttker, B.; Lischka, K.; Schikora, D.

    1999-02-01

    Cubic GaN layers are grown by molecular beam epitaxy on (0 0 1)GaAs substrates. The influence of intentional deviations from stoichiometric growth conditions on the structural homogeneity of the epitaxial layers and the GaN/GaAs interface was studied. Optical micrographs and AFM-images of the epilayers grown in a Ga-stabilised regime reveal the existence of different types of surface irregularities. We conclude that the irregularities observed are the result of successively melt-back etching in GaN and GaAs and solution growth within Ga-droplets due to the change of the saturation conditions of the liquid Ga-phase on the surface of the growing film.

  11. The studies of scale surface produced on outer diffusion layers

    Directory of Open Access Journals (Sweden)

    J. Augustyn-Pieniążek

    2011-04-01

    Full Text Available In this study at attempt was made to examine the scale formed on ferritic-austenitic duplex type steel subjected to previous thermochemical treatment. The treatment consisted in diffusion aluminising in a metallising mixture composed of Fe-Al powder. As an activator, ammonium chloride (NH4Cl added in an amount of 2 wt.% was used. Then, both the base material and samples with the diffusiondeposited surface layers were oxidised at 1000°C in the air. Thus formed scales were identified by light microscopy, SEM and X-ray phase analysis. The aim of the oxidation tests carried out under isothermal conditions was to compare the scale morphology when obtained on untreated substrate material and on the surface layers rich in aluminium.

  12. Tracking near-surface atmospheric conditions using an infrasound network.

    Science.gov (United States)

    Marcillo, O; Johnson, J B

    2010-07-01

    Continuous volcanic infrasound signal was recorded on a three-microphone network at Kilauea in July 2008 and inverted for near-surface horizontal winds. Inter-station phase delays, determined by signal cross-correlation, vary by up to 4% and are attributable to variable atmospheric conditions. The results suggest two predominant weather regimes during the study period: (1) 6-9 m/s easterly trade winds and (2) lower-intensity 2-5 m/s mountain breezes from Mauna Loa. The results demonstrate the potential of using infrasound for tracking local averaged meteorological conditions, which has implications for modeling plume dispersal and quantifying gas flux.

  13. Site-specific electronic structure of bacterial surface protein layers

    Science.gov (United States)

    Vyalikh, D. V.; Kummer, K.; Kade, A.; Blüher, A.; Katzschner, B.; Mertig, M.; Molodtsov, S. L.

    2009-03-01

    We applied resonant photoemission and X-ray absorption spectroscopy for a detailed characterization of the valence electronic structure of the regular two-dimensional bacterial surface protein layer of Bacillus sphaericus NCTC 9602. Using this approach, we detected valence electron emission from specific chemical sites. In particular, it was found that electrons from the π clouds of aromatic systems make large contributions to the highest occupied molecular orbitals.

  14. First-order chemistry in the surface-flux layer

    DEFF Research Database (Denmark)

    Kristensen, L.; Andersen, C.E.; Ejsing Jørgensen, Hans

    1997-01-01

    We have discussed the behavior of a non-conserved scalar in the stationary, horizontally homogeneous, neutral surface-flux layer and, on the basis of conventional second-order closure, derived analytic expressions for flux and for mean concentration of a gas, subjected to a first-order removal pr...... on the validity of our predictions. The agreement seemed such that a falsification of our model was impossible. It is shown how the model can be used to predict the surface flux of Rn-220 from measured concentration profiles....

  15. Surface analysis of 316 stainless steel treated with cold atmospheric plasma

    Science.gov (United States)

    Williams, David F.; Kellar, Ewen J. C.; Jesson, David A.; Watts, John F.

    2017-05-01

    The surface of 316 stainless steel has been modified using cold atmospheric plasma (CAP) to increase the surface free energy (by cleaning the and chemically activating the surface)IN preparation for subsequent processes such as painting, coating or adhesive bonding. The analyses carried out, on CAP treated 316 stainless steel surfaces, includes X-ray photoelectron spectroscopy (XPS), imaging XPS (iXPS), and surface free energy (SFE) analysis using contact angle measurements. The CAP treatment is shown to increase the SFE of as-received 316 stainless steel from ∼39 mJ m-1 to >72 mJ m-1 after a short exposure to the plasma torch. This was found to correlate to a reduction in adventitious carbon, as determined by XPS analysis of the surface. The reduction from ∼90 at% to ∼30% and ∼39 at%, after being plasma treated for 5 min and 15 s respectively, shows that the process is relatively quick at changing the surface. It is suggested that the mechanism that causes the increase in surface free energy is chain scission of the hydrocarbon contamination triggered by free electrons in the plasma plume followed by chemical functionalisation of the metal oxide surface and some of the remaining carbon contamination layer.

  16. Effect of atmospheric-pressure plasma treatment on the adhesion properties of a thin adhesive layer in a selective transfer process

    Science.gov (United States)

    Yoon, Min-Ah; Kim, Chan; Hur, Min; Kang, Woo Seok; Kim, Jaegu; Kim, Jae-Hyun; Lee, Hak-Joo; Kim, Kwang-Seop

    2018-01-01

    The adhesion between a stamp and thin film devices is crucial for their transfer on a flexible substrate. In this paper, a thin adhesive silicone layer on the stamp was treated by atmospheric pressure plasma to locally control the adhesion strength for the selective transfer. The adhesion strength of the silicone layer was significantly reduced after the plasma treatment, while its surface energy was increased. To understand the inconsistency between the adhesion strength and surface energy changes, the surface properties of the silicone layer were characterized using nanoindentation and X-ray photoelectron spectroscopy. These techniques revealed that a thin, hard, silica-like layer had formed on the surface from plasma-enhanced oxidation. This layer played an important role in decreasing the contact area and increasing the interfacial slippage, resulting in decreased adhesion. As a practical application, the transfer process was demonstrated on GaN LEDs that had been previously delaminated by a laser lift-off (LLO) process. Although the LEDs were not transferred onto the treated adhesive layer due to the reduced adhesion, the untreated adhesive layer could readily pick up the LEDs. It is expected that this simple method of controlling the adhesion of a stamp with a thin adhesive layer would enable a continuous, selective and large-scale roll-to-roll selective transfer process and thereby advance the development of flexible, stretchable and wearable electronics.

  17. Manufacturing of Electrolyte and Cathode Layers SOFC Using Atmospheric Spraying Method and Its Characterization

    Directory of Open Access Journals (Sweden)

    S. Sulistyo

    2012-12-01

    Full Text Available The use of Solid Oxide Fuel Cell (SOFC has created various interest in many parties, due to its capability to convert gases into electricity. The main requirement of SOFC cell components is to be produced as thin as possible to minimize the losses of electrical resistance, as well as able to support internal and external loads. This paper discusses the procedure of making a thin electrolyte layer, as well as a porous thin layer cathode using atmospheric spraying technique. The procedure of spraying was in room temperature with the process of sintering at temperature of 13500 C held for 3 hours. The SOFC characterization of electrolyte and cathode microstructure was determined by using the SEM, FESEM, XRD and impedance spectroscopy, to measure the impedance of SOFC cells. The results show that the thickness of thin layer electrolyte and porous cathode obtained of about 20 µm and 4 µm, respectively. Also the SOFC cell impedance was measured of 2.3726 x 106 Ω at room temperature. The finding also demonstrated that although the materials (anode, cathode and electrolyte possess different coefficient thermal expansion, there was no evidence of flaking layers which seen the materials remain intact. Thus, the atmospheric spraying method can offer an alternative method to manufacturing of SOFC thin layer electrolyte and cathode. [Key words: SOFC; spraying method; electrolyte; cathode

  18. LDPE Surface Modifications Induced by Atmospheric Plasma Torches with Linear and Showerhead Configurations

    CERN Document Server

    Rich, Sami Abou; Leroy, Perrine; Reniers, François; Nittler, Laurent; Pireaux, Jean-Jacques

    2016-01-01

    Low density polyethylene (LDPE) surfaces have been plasma modified to improve their nanostructural and wettability properties. These modifications can significantly improve the deposition of subsequent layers such as films with specific barrier properties. For this purpose, we compare the treatments induced by two atmospheric plasma torches with different configurations (showerhead vs. linear). The modifications of LDPE films in terms of chemical surface composition and surface morphology are evidenced by X-ray photoelectron spectro-scopy, water contact angles measurements, and atomic force microscopy. A comparison between the two post-discharge treatments is achieved for several torch-to-substrate distances (gaps), treatment times, and oxygen flow rates in terms of etching rate, roughening rate, diffusion of oxygen into the subsur-face and hydrophilicity. By correlating these results with the chemical composition of the post-discharges, we identify and compare the 'species which are responsible for the chemi...

  19. Surface Treatment of PET Nonwovens with Atmospheric Plasma

    Science.gov (United States)

    Li, Shufang

    2013-01-01

    In this study, polyethylene-terephthalate (PET) nonwovens are treated using an atmospheric plasma and the effects of the treatment time, treatment power and discharge distance on the ability of water-penetration into the nonwovens are investigated. The result indicates that the method can improve the wettability of PET nonwovens remarkably, but the aging decay of the sample's wettability is found to be notable as a function of the storage time after treatment due to the internal rotation of the single bond of surface macromolecules. As shown by SEM and XPS analysis, the etching and surface reaction are significant, and water-penetration weight is found to increase remarkably with the increasing power. This variation can be attributed to momentum transfer and enhanced higher-energy particle excitation.

  20. Virtual ellipsometry on layered micro-facet surfaces.

    Science.gov (United States)

    Wang, Chi; Wilkie, Alexander; Harcuba, Petr; Novosad, Lukas

    2017-09-18

    Microfacet-based BRDF models are a common tool to describe light scattering from glossy surfaces. Apart from their wide-ranging applications in optics, such models also play a significant role in computer graphics for photorealistic rendering purposes. In this paper, we mainly investigate the computer graphics aspect of this technology, and present a polarisation-aware brute force simulation of light interaction with both single and multiple layered micro-facet surfaces. Such surface models are commonly used in computer graphics, but the resulting BRDF is ultimately often only approximated. Recently, there has been work to try to make these approximations more accurate, and to better understand the behaviour of existing analytical models. However, these brute force verification attempts still emitted the polarisation state of light and, as we found out, this renders them prone to mis-estimating the shape of the resulting BRDF lobe for some particular material types, such as smooth layered dielectric surfaces. For these materials, non-polarising computations can mis-estimate some areas of the resulting BRDF shape by up to 23%. But we also identified some other material types, such as dielectric layers over rough conductors, for which the difference turned out to be almost negligible. The main contribution of our work is to clearly demonstrate that the effect of polarisation is important for accurate simulation of certain material types, and that there are also other common materials for which it can apparently be ignored. As this required a BRDF simulator that we could rely on, a secondary contribution is that we went to considerable lengths to validate our software. We compare it against a state-of-art model from graphics, a library from optics, and also against ellipsometric measurements of real surface samples.

  1. Physical modeling of the atmospheric boundary layer in the UNH Flow Physics Facility

    Science.gov (United States)

    Taylor-Power, Gregory; Gilooly, Stephanie; Wosnik, Martin; Klewicki, Joe; Turner, John

    2016-11-01

    The Flow Physics Facility (FPF) at UNH has test section dimensions W =6.0m, H =2.7m, L =72m. It can achieve high Reynolds number boundary layers, enabling turbulent boundary layer, wind energy and wind engineering research with exceptional spatial and temporal instrument resolution. We examined the FPF's ability to experimentally simulate different types of the atmospheric boundary layer (ABL) using upstream roughness arrays. The American Society for Civil Engineers defines standards for simulating ABLs for different terrain types, from open sea to dense city areas (ASCE 49-12). The standards require the boundary layer to match a power law shape, roughness height, and power spectral density criteria. Each boundary layer type has a corresponding power law exponent and roughness height. The exponent and roughness height both increase with increasing roughness. A suburban boundary layer was chosen for simulation and a roughness element fetch was created. Several fetch lengths were experimented with and the resulting boundary layers were measured and compared to standards in ASCE 49-12: Wind Tunnel Testing for Buildings and Other Structures. Pitot tube and hot wire anemometers were used to measure average and fluctuating flow characteristics. Velocity profiles, turbulence intensity and velocity spectra were found to compare favorably.

  2. Effect of impurities in the description of surface nanobubbles: Role of nonidealities in the surface layer

    NARCIS (Netherlands)

    Das, S.

    2011-01-01

    In a recent study [ S. Das, J. H. Snoeijer and D. Lohse Phys. Rev. E 82 056310 (2010)], we provided quantitative demonstration of the conjecture [ W. A. Ducker Langmuir 25 8907 (2009)] that the presence of impurities at the surface layer (or the air-water interface) of surface nanobubbles can

  3. 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

  4. Helium atmospheric pressure plasma jets touching dielectric and metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Norberg, Seth A., E-mail: norbergs@umich.edu; Johnsen, Eric, E-mail: ejohnsen@umich.edu [Department of Mechanical Engineering, University of Michigan, 2350 Hayward Street, Ann Arbor, Michigan 48109-2125 (United States); Kushner, Mark J., E-mail: mjkush@umich.edu [Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Avenue, Ann Arbor, Michigan 48109-2122 (United States)

    2015-07-07

    Atmospheric pressure plasma jets (APPJs) are being investigated in the context plasma medicine and biotechnology applications, and surface functionalization. The composition of the surface being treated ranges from plastics, liquids, and biological tissue, to metals. The dielectric constant of these materials ranges from as low as 1.5 for plastics to near 80 for liquids, and essentially infinite for metals. The electrical properties of the surface are not independent variables as the permittivity of the material being treated has an effect on the dynamics of the incident APPJ. In this paper, results are discussed from a computational investigation of the interaction of an APPJ incident onto materials of varying permittivity, and their impact on the discharge dynamics of the plasma jet. The computer model used in this investigation solves Poisson's equation, transport equations for charged and neutral species, the electron energy equation, and the Navier-Stokes equations for the neutral gas flow. The APPJ is sustained in He/O{sub 2} = 99.8/0.2 flowing into humid air, and is directed onto dielectric surfaces in contact with ground with dielectric constants ranging from 2 to 80, and a grounded metal surface. Low values of relative permittivity encourage propagation of the electric field into the treated material and formation and propagation of a surface ionization wave. High values of relative permittivity promote the restrike of the ionization wave and the formation of a conduction channel between the plasma discharge and the treated surface. The distribution of space charge surrounding the APPJ is discussed.

  5. Surface Modification of Electrospun PVDF/PAN Nanofibrous Layers by Low Vacuum Plasma Treatment

    Directory of Open Access Journals (Sweden)

    Fatma Yalcinkaya

    2016-01-01

    Full Text Available Nanofibres are very promising for water remediation due to their high porosity and small pore size. Mechanical properties of nanofibres restrict the application of pressure needed water treatments. Various PAN, PVDF, and PVDF/PAN nanofibre layers were produced, and mechanical properties were improved via a lamination process. Low vacuum plasma treatment was applied for the surface modification of nanofibres. Atmospheric air was used to improve hydrophilicity while sulphur hexafluoride gas was used to improve hydrophobicity of membranes. Hydrophilic membranes showed higher affinity to attach plasma particles compared to hydrophobic membranes.

  6. Characteristics of aerosol at a lower atmospheric layer in DRAGON field campaign

    Science.gov (United States)

    KUJI, M.; Azuma, Y.; Kitakoga, S.; Sano, I.; Holben, B. N.

    2013-12-01

    Air pollution arises severely over East Asia with the rapid economic development nowadays. Monitoring the atmospheric environment, as one of the purposes, an intensive field campaign, Distributed Regional Aerosol Gridded Observation Networks (DRAGON), was carried out in the spring of year 2012, led by National Aeronautics and Space Administration (NASA). At that time, atmospheric phenomena such as Yellow sand and haze events were observed at Nara in the western part of Japan, as one of the DRAGON observation sites. The atmospheric events were characterized with the AErosol RObotic NETwork (AERONET) data. As a result of the data analysis, it was found that more light-absorbing and smaller particles dominated at the lower than upper atmospheric layer for the Kosa event in particular. A backward trajectory analysis suggested that the Yellow sand event traveled over the East Asian industrial cities, which could lead to a mixture of sand and air pollutants with moderate particle size and light-absorptivity. In addition, visibility observation was evaluated quantitatively with AERONET data in the DRAGON campaign since eye observation was inherently semi-quantitative. The extinction coefficient estimated from visibility was compared to that from AERONET. As a result, it was found that the extinction coefficients were generally consistent to each other. But there were some discrepancies, which could be caused with the atmospheric phenomena or aerosol types. It is confirmed that visibility is strongly influenced with aerosols in the case of severe atmospheric phenomena in particular.

  7. Reply to comment by Igor Esau on “Do stable atmospheric layers exist?”

    Science.gov (United States)

    Lovejoy, S.; Tuck, A. F.; Schertzer, D.; Hovde, S. J.

    2009-06-01

    We would like to thank Esau (2009) for attempting to save the classical notion of stable layers; his argument is very close to one raised up by an anonymous reviewer of Lovejoy et al. (2008b). Since a similar argument is often invoked to justify atmospheric applications of linear gravity wave theories, it appears to be widespread in the community. We therefore hope this debate will clarify the issue.

  8. Key features of the atmospheric boundary layer measurement by small unmanned aerial vehicles

    Science.gov (United States)

    Polivanov, P. A.; Sidorenko, A. A.

    2017-10-01

    A review of the current state of the methods for measuring the atmospheric boundary layer is carried out. It is shown that the use of small unmanned vehicles can improve the quality of measurements. The paper discusses the problems associated with the data processing of air speed sensors of small aircraft. To restore data on wind speed and its pulsations, the use of algorithms using accelerometers and GPS sensors was suggested.

  9. Fluxes of nitrates between snow surfaces and the atmosphere in the European high Arctic

    Directory of Open Access Journals (Sweden)

    H. J. Beine

    2003-01-01

    Full Text Available Measurements of atmospheric and snow mixing ratios of nitrates and nitrites and their fluxes above the snow surface were made during two intensive campaigns during spring time 2001 at Ny-Ålesund, Svalbard as part of the EU project  "`The NItrogen Cycle and Effects on the oxidation of atmospheric trace species at high latitudes' (NICE. At this coastal site close to the unseasonably unfrozen fjord, of the measured nitrogen species, only HNO3 showed a significant flux on to the snow surface; a mean deposition of -8.7 nmol h-1 m-2 was observed in late April / early May 2001. These fluxes may be due to the reaction of HNO3 with sea salt, and especially NaCl, or may be simply uptake of HNO3 by ice, which is alkaline because of the sea salt in our marine environment. During snowfall periods dry deposition of HNO3 may contribute up to 10% of the N budget in the snow; however, the main source for N is wet deposition in falling snow. The surface snow at Ny-Ålesund showed very complex stratigraphy; the NO3- mixing ratio in snow varied between 65 and 520 ng g-1, the total NO3- content of the snowpack was on the order of 2700 ng cm-2. In comparison the atmospheric boundary layer column showed a NO3- content of only 8 ng cm-2. The limited exchange, however, between the snow and the atmosphere was attributed to low mobility of NO3- in the observed snow. Contrary to other Arctic sites (i.e. Alert, Nunavut or Summit, Greenland deposition of sea salt and crustal aerosols in this marine environment made the surface snow alkaline; snow NO3- was associated with heavier cations and was not readily available for physical exchange or photochemical reactions.

  10. A comprehensive investigation on afternoon transition of the atmospheric boundary layer over a tropical rural site

    Science.gov (United States)

    Sandeep, A.; Rao, T. N.; Rao, S. V. B.

    2015-07-01

    The transitory nature of the atmospheric boundary layer (ABL) a few hours before and after the time of sunset has been studied comprehensively over a tropical station, Gadanki (13.45° N, 79.18° E), using a suite of in situ and remote sensing devices. This study addresses the following fundamental and important issues related to the afternoon transition (AT): which state variable first identifies the AT? Which variable best identifies the AT? Does the start time of the AT vary with season and height? If so, which physical mechanism is responsible for the observed height variation in the start time of the transition? At the surface, the transition is first seen in temperature (T) and wind variance (σ2WS), ~ 100 min prior to the time of local sunset, then in the vertical temperature gradient and finally in water vapor mixing ratio variations. Aloft, both signal-to-noise ratio (SNR) and spectral width (σ) show the AT nearly at the same time. The T at the surface and SNR aloft are found to be the best indicators of transition. Their distributions for the start time of the AT with reference to time of sunset are narrow and consistent in both total and seasonal plots. The start time of the transition shows some seasonal variation, with delayed transitions occurring mostly in the rainy and humid season of the northeast monsoon. Interestingly, in contrast to the general perception, the signature of the transition is first seen in the profiler data, then in the sodar data, and finally in the surface data. This suggests that the transition follows a top-to-bottom evolution. It indicates that other processes, like entrainment, could also play a role in altering the structure of the ABL during the AT, when the sensible heat flux decreases progressively. These mechanisms are quantified using a unique high-resolution data set to understand their variation in light of the intriguing height dependency of the start time of the AT.

  11. Design of Meteorological Element Detection Platform for Atmospheric Boundary Layer Based on UAV

    Directory of Open Access Journals (Sweden)

    Yonghong Zhang

    2017-01-01

    Full Text Available Among current detection methods of the atmospheric boundary layer, sounding balloon has disadvantages such as low recovery and low reuse rate, anemometer tower has disadvantages such as fixed location and high cost, and remote sensing detection has disadvantages such as low data accuracy. In this paper, a meteorological element sensor was carried on a six-rotor UAV platform to achieve detection of meteorological elements of the atmospheric boundary layer, and the influence of different installation positions of the meteorological element sensor on the detection accuracy of the meteorological element sensor was analyzed through many experiments. Firstly, a six-rotor UAV platform was built through mechanical structure design and control system design. Secondly, data such as temperature, relative humidity, pressure, elevation, and latitude and longitude were collected by designing a meteorological element detection system. Thirdly, data management of the collected data was conducted, including local storage and real-time display on ground host computer. Finally, combined with the comprehensive analysis of the data of automatic weather station, the validity of the data was verified. This six-rotor UAV platform carrying a meteorological element sensor can effectively realize the direct measurement of the atmospheric boundary layer and in some cases can make up for the deficiency of sounding balloon, anemometer tower, and remote sensing detection.

  12. Near-Surface Boundary Layer Turbulence Along a Horizontally-Moving, Surface-Piercing Vertical Wall

    CERN Document Server

    Washuta, Nathan; Duncan, James H

    2016-01-01

    The complex interaction between turbulence and the free surface in boundary layer shear flow created by a vertical surface-piercing wall is considered. A laboratory-scale device was built that utilizes a surface-piercing stainless steel belt that travels in a loop around two vertical rollers, with one length of the belt between the rollers acting as a horizontally-moving flat wall. The belt is accelerated suddenly from rest until reaching constant speed in order to create a temporally-evolving boundary layer analogous to the spatially-evolving boundary layer that would exist along a surface-piercing towed flat plate. Surface profiles are measured with a cinematic laser-induced fluorescence system and sub-surface velocity fields are recorded using a high-speed planar particle image velocimetry system. It is found that the belt initially travels through the water without creating any significant waves, before the free surface bursts with activity close to the belt surface. These free surface ripples travel away...

  13. A novel surface cleaning method for chemical removal of fouling lead layer from chromium surfaces

    Science.gov (United States)

    Gholivand, Kh.; Khosravi, M.; Hosseini, S. G.; Fathollahi, M.

    2010-10-01

    Most products especially metallic surfaces require cleaning treatment to remove surface contaminations that remain after processing or usage. Lead fouling is a general problem which arises from lead fouling on the chromium surfaces of bores and other interior parts of systems which have interaction with metallic lead in high temperatures and pressures. In this study, a novel chemical solution was introduced as a cleaner reagent for removing metallic lead pollution, as a fouling metal, from chromium surfaces. The cleaner aqueous solution contains hydrogen peroxide (H 2O 2) as oxidizing agent of lead layer on the chromium surface and acetic acid (CH 3COOH) as chelating agent of lead ions. The effect of some experimental parameters such as acetic acid concentration, hydrogen peroxide concentration and temperature of the cleaner solution during the operation on the efficiency of lead cleaning procedure was investigated. The results of scanning electron microscopy (SEM) showed that using this procedure, the lead pollution layer could be completely removed from real chromium surfaces without corrosion of the original surface. Finally, the optimum conditions for the complete and fast removing of lead pollution layer from chromium surfaces were proposed. The experimental results showed that at the optimum condition (acetic acid concentration 28% (V/V), hydrogen peroxide 8% (V/V) and temperature 35 °C), only 15-min time is needed for complete removal of 3 g fouling lead from a chromium surface.

  14. Vertical Sampling Scales for Atmospheric Boundary Layer Measurements from Small Unmanned Aircraft Systems (sUAS

    Directory of Open Access Journals (Sweden)

    Benjamin L. Hemingway

    2017-09-01

    Full Text Available The lowest portion of the Earth’s atmosphere, known as the atmospheric boundary layer (ABL, plays an important role in the formation of weather events. Simple meteorological measurements collected from within the ABL, such as temperature, pressure, humidity, and wind velocity, are key to understanding the exchange of energy within this region, but conventional surveillance techniques such as towers, radar, weather balloons, and satellites do not provide adequate spatial and/or temporal coverage for monitoring weather events. Small unmanned aircraft, or aerial, systems (sUAS provide a versatile, dynamic platform for atmospheric sensing that can provide higher spatio-temporal sampling frequencies than available through most satellite sensing methods. They are also able to sense portions of the atmosphere that cannot be measured from ground-based radar, weather stations, or weather balloons and have the potential to fill gaps in atmospheric sampling. However, research on the vertical sampling scales for collecting atmospheric measurements from sUAS and the variabilities of these scales across atmospheric phenomena (e.g., temperature and humidity is needed. The objective of this study is to use variogram analysis, a common geostatistical technique, to determine optimal spatial sampling scales for two atmospheric variables (temperature and relative humidity captured from sUAS. Results show that vertical sampling scales of approximately 3 m for temperature and 1.5–2 m for relative humidity were sufficient to capture the spatial structure of these phenomena under the conditions tested. Future work is needed to model these scales across the entire ABL as well as under variable conditions.

  15. The role of snow-surface coupling, radiation, and turbulent mixing in modeling a stable boundary layer over Arctic sea ice

    NARCIS (Netherlands)

    Sterk, H.A.M.; Steeneveld, G.J.; Holtslag, A.A.M.

    2013-01-01

    To enhance the understanding of the impact of small-scale processes in the polar climate, this study focuses on the relative role of snow-surface coupling, radiation and turbulent mixing in an Arctic stable boundary layer. We extend the GABLS1 (GEWEX Atmospheric Boundary-Layer Study 1) model

  16. Hierarchical Composite Membranes with Robust Omniphobic Surface Using Layer-By-Layer Assembly Technique

    KAUST Repository

    Woo, Yun Chul

    2018-01-17

    In this study, composite membranes were fabricated via layer-by-layer (LBL) assembly of negatively-charged silica aerogel (SiA) and 1H, 1H, 2H, 2H – Perfluorodecyltriethoxysilane (FTCS) on a polyvinylidene fluoride phase inversion membrane, and interconnecting them with positively-charged poly(diallyldimethylammonium chloride) (PDDA) via electrostatic interaction. The results showed that the PDDA-SiA-FTCS coated membrane had significantly enhanced the membrane structure and properties. New trifluoromethyl and tetrafluoroethylene bonds appeared at the surface of the coated membrane, which led to lower surface free energy of the composite membrane. Additionally, the LBL membrane showed increased surface roughness. The improved structure and property gave the LBL membrane an omniphobic property, as indicated by its good wetting resistance. The membrane performed a stable air gap membrane distillation (AGMD) flux of 11.22 L/m2h with very high salt rejection using reverse osmosis brine from coal seam gas produced water as feed with the addition of up to 0.5 mM SDS solution. This performance was much better compared to those of the neat membrane. The present study suggests that the enhanced membrane properties with good omniphobicity via LBL assembly make the porous membranes suitable for long-term AGMD operation with stable permeation flux when treating challenging saline wastewater containing low surface tension organic contaminants.

  17. Soil moisture sensor calibration for organic soil surface layers

    Science.gov (United States)

    Bircher, Simone; Andreasen, Mie; Vuollet, Johanna; Vehviläinen, Juho; Rautiainen, Kimmo; Jonard, François; Weihermüller, Lutz; Zakharova, Elena; Wigneron, Jean-Pierre; Kerr, Yann H.

    2016-04-01

    This paper's objective is to present generic calibration functions for organic surface layers derived for the soil moisture sensors Decagon ECH2O 5TE and Delta-T ThetaProbe ML2x, using material from northern regions, mainly from the Finnish Meteorological Institute's Arctic Research Center in Sodankylä and the study area of the Danish Center for Hydrology (HOBE). For the Decagon 5TE sensor such a function is currently not reported in the literature. Data were compared with measurements from underlying mineral soils including laboratory and field measurements. Shrinkage and charring during drying were considered. For both sensors all field and lab data showed consistent trends. For mineral layers with low soil organic matter (SOM) content the validity of the manufacturer's calibrations was demonstrated. Deviating sensor outputs in organic and mineral horizons were identified. For the Decagon 5TE, apparent relative permittivities at a given moisture content decreased for increased SOM content, which was attributed to an increase of bound water in organic materials with large specific surface areas compared to the studied mineral soils. ThetaProbe measurements from organic horizons showed stronger nonlinearity in the sensor response and signal saturation in the high-level data. The derived calibration fit functions between sensor response and volumetric water content hold for samples spanning a wide range of humus types with differing SOM characteristics. This strengthens confidence in their validity under various conditions, rendering them highly suitable for large-scale applications in remote sensing and land surface modeling studies. Agreement between independent Decagon 5TE and ThetaProbe time series from an organic surface layer at the Sodankylä site was significantly improved when the here-proposed fit functions were used. Decagon 5TE data also well-reflected precipitation events. Thus, Decagon 5TE network data from organic surface layers at the Sodankylä and

  18. Development and evaluation of airborne microwave refractometer for studies on atmospheric tropical boundary layer radiorefractive index

    Directory of Open Access Journals (Sweden)

    S. B. S. S. Sarma

    Full Text Available Observations of high-resolution data on radio refractivity were obtained by the airborne microwave refractometer over the Indian sub-continent (a tropical country from 1971 to 1988. Detailed vertical and horizontal distributions of radio refractivity on a near-real-time basis in the atmospheric boundary layer were determined . Radiosonde observations cannot detect the thin refractivity gradients which characterize the propagation environment in this low-altitude region. This knowledge is required to design reliable and efficient communication systems for strategic, tactical and operational needs. However, the results demonstrate the layer structures and the variability of the boundary layer in time and space. The radio refractive effects on electromagnetic propagation and the future direction of radio refractivity fine-structure measurements are discussed.

  19. Engineering Particle Surface Chemistry and Electrochemistry with Atomic Layer Deposition

    Science.gov (United States)

    Jackson, David Hyman Kentaro

    Atomic layer deposition (ALD) is a vapor phase thin film coating technique that relies on sequential pulsing of precursors that undergo self-limited surface reactions. The self- limiting reactions and gas phase diffusion of the precursors together enable the conformal coating of microstructured particles with a high degree of thickness and compositional control. ALD may be used to deposit thin films that introduce new functionalities to a particle surface. Examples of new functionalities include: chemical reactivity, a mechanically strong protective coating, and an electrically resistive layer. The coatings properties are often dependent on the bulk properties and microstructure of the particle substrate, though they usually do not affect its bulk properties or microstructure. Particle ALD finds utility in the ability to synthesize well controlled, model systems, though it is expensive due to the need for costly metal precursors that are dangerous and require special handling. Enhanced properties due to ALD coating of particles in various applications are frequently described empirically, while the details of their enhancement mechanisms often remain the focus of ongoing research in the field. This study covers the various types of particle ALD and attempts to describe them from the unifying perspective of surface science.

  20. Long-term record of atmospheric and snow surface nitrate from Dome C (Central Antarctica)

    Science.gov (United States)

    Traversi, Rita; Becagli, Silvia; Brogioni, Marco; Caiazzo, Laura; Ciardini, Virginia; Giardi, Fabio; Legrand, Michel; Macelloni, Giovanni; Petkov, Boyan; Preunkert, Suzanne; Scarchilli, Claudio; Severi, Mirko; Vitale, Vito; Udisti, Roberto

    2017-04-01

    Nitrate is the end product of the oxidation of atmospheric nitrogen oxides and one of the most abundant ions present in polar ice and snow, mainly as nitric acid in present-climate conditions. Nitrate stratigraphies from snow and ice layers have the potential to provide records of past changes in atmospheric composition, including atmospheric NOx cycling and oxidative capacity, as well as past solar activity or major variations in Earth's magnetic field. Nevertheless, in order to exploit such a potential, chemical concentrations in the air, snow, firn and ice core need to be correlated. Hence, the knowledge of the link between atmosphere and snow composition at the time of deposition is basic to reconstruct past climate and past atmospheric chemical composition. The extent of such knowledge depends on whether the species of interest are gaseous or in the condensed phase, and if they are reversible and/or irreversibly deposited to snow. In order to provide a contribution to their air-to-snow exchange in the Antarctic plateau, as well as to the understanding of dominant sources and sinks of nitrate, we present here nitrate records in atmospheric aerosol and surface snow sampled at high resolution, all year-round, at Dome C along 9 years (November 2004 - November 2013). This represents the longest and most highly resolved record from continental Antarctica, where continuous and long-term atmosphere and snow samplings are particularly difficult due to the extreme meteorological conditions and, at the same time, need of extra-care in avoiding contamination due to the low level of ion concentrations. Results confirm, on a larger statistical data set with respect to previous observations, nitrate seasonal pattern with summer maxima both for aerosol and surface snow, in-phase with UV solar irradiance. Such a temporal pattern is likely a combination of nitrate sources and post-depositional processes that enhance during summer. Moreover, a case study of synoptic analysis for

  1. An Investigation on the role of Planetary Boundary Layer Parameterization scheme on the performance of a hydrostatic atmospheric model over a Coastal Region

    Science.gov (United States)

    Anurose, J. T.; Subrahamanyam, Bala D.

    2012-07-01

    As part of the ocean/land-atmosphere interaction, more than half of the total kinetic energy is lost within the lowest part of atmosphere, often referred to as the planetary boundary layer (PBL). A comprehensive understanding of the energetics of this layer and turbulent processes responsible for dissipation of kinetic energy within the PBL require accurate estimation of sensible and latent heat flux and momentum flux. In numerical weather prediction (NWP) models, these quantities are estimated through different surface-layer and PBL parameterization schemes. This research article investigates different factors influencing the accuracy of a surface-layer parameterization scheme used in a hydrostatic high-resolution regional model (HRM) in the estimation of surface-layer turbulent fluxes of heat, moisture and momentum over the coastal regions of the Indian sub-continent. Results obtained from this sensitivity study of a parameterization scheme in HRM revealed the role of surface roughness length (z_{0}) in conjunction with the temperature difference between the underlying ground surface and atmosphere above (ΔT = T_{G} - T_{A}) in the estimated values of fluxes. For grid points over the land surface where z_{0} is treated as a constant throughout the model integration time, ΔT showed relative dominance in the estimation of sensible heat flux. In contrast to this, estimation of sensible and latent heat flux over ocean were found to be equally sensitive on the method adopted for assigning the values of z_{0} and also on the magnitudes of ΔT.

  2. Moored surface buoy observations of the diurnal warm layer

    KAUST Repository

    Prytherch, J.

    2013-09-01

    An extensive data set is used to examine the dynamics of diurnal warming in the upper ocean. The data set comprises more than 4700 days of measurements at five sites in the tropics and subtropics, obtained from surface moorings equipped to make comprehensive meteorological, incoming solar and infrared radiation, and high-resolution subsurface temperature (and, in some cases, velocity) measurements. The observations, which include surface warmings of up to 3.4°C, are compared with a selection of existing models of the diurnal warm layer (DWL). A simple one-layer physical model is shown to give a reasonable estimate of both the magnitude of diurnal surface warming (model-observation correlation 0.88) and the structure and temporal evolution of the DWL. Novel observations of velocity shear obtained during 346 days at one site, incorporating high-resolution (1 m) upper ocean (5-15 m) acoustic Doppler current profile measurements, are also shown to be in reasonable agreement with estimates from the physical model (daily maximum shear model-observation correlation 0.77). Physics-based improvements to the one-layer model (incorporation of rotation and freshwater terms) are discussed, though they do not provide significant improvements against the observations reported here. The simplicity and limitations of the physical model are used to discuss DWL dynamics. The physical model is shown to give better model performance under the range of forcing conditions experienced across the five sites than the more empirical models. ©2013. American Geophysical Union. All Rights Reserved.

  3. Ground-based satellite-type images of the upper-atmosphere emissive layer

    Science.gov (United States)

    Pautet, Dominique; Moreels, Guy

    2002-02-01

    With the introduction of infrared (IR) retina sensors used as focal-plane arrays in large telescopes, astronomical observations are now frequently located in the near-IR part of the spectrum. In this region the upper atmosphere introduces in the 0.7-3-μm range an additional component due to the OH vibrational band emission that should be subtracted from the astronomical data. Observations of this upper-atmosphere emission performed at the Pic de Cha‸teaurenard (altitude of 2989 m) are presented here. A panoramic image of the emission is constructed by use of a set of 48 images obtained with a CCD camera mounted on an alt-azimuthal platform. After a numerical filter is used to suppress the star images, the atmospheric emission shows two distinct sets of arches vanishing at two opposite points in the WNW and ESE azimuths. The emissive layer, caused by the ozone-hydrogen reaction, is thin and located at the altitude of 85 km. By use of these data, the perspective effect that produces the panoramic arches is inverted in introducing the concept of a virtual camera. The Van Rhijn effect and the refraction correction are taken into account. The three punctual transformations that use matrix algorithms are analyzed. The result is a satellite-type view of the emissive layer that appears as a disk having a radius of ~1100 km. This disk is limited by the summit line of the Alps surrounding the Pic de Cha‸teaurenard. The field of view covers a large part of Europe, the Mediterranean Sea, and North Africa. It shows an extended wave system. The images presented show that the upper-atmospheric layer is an efficient tracer of the dynamic processes at that level. Satellite-type views can be calculated without the drawback of looking downward from a satellite and measuring the numerous emissions from cities, oil fields, and other luminous sources.

  4. Towards fully predictive large-eddy simulation of the atmospheric boundary layer

    Science.gov (United States)

    Matheou, G.; Chung, D.; Teixeira, J.

    2012-12-01

    The atmospheric boundary layer is host to a plethora of physical processes that strongly affect the energy balance of Earth, and consequently weather and climate. Large-eddy Simulation (LES) is an invaluable technique in the study and prediction of the boundary layer mainly because it can capture detailed flow structure including clouds. In spite of the widespread use of LES, predictions of atmospheric flows lack fidelity. We discuss the development of a novel state-of-the-art LES framework suitable for the simulation of atmospheric flows and focus on the effects of turbulent transport, including stable stratification and multi-phase/latent heat exchange physics. The main components of the LES framework are a high-order fully conservative finite difference discretization and the buoyancy-adjusted stretched-vortex subgrid-scale (SGS) model. The new stability correction of the SGS model accounts of the increasing anisotropy of turbulence motions as stratification increases in a way that is consistent with the physics of stratified turbulence. Moreover, the SGS model employs no flow adjustable parameters. Our aim is twofold: (i) using identical LES setup (e.g. advection scheme and SGS-model parameters), perform simulations of diverse boundary layers, including stable, convectively unstable, cumulus and stratocumulus convection; and (ii) investigate grid convergence of flow statistics. We show that the new LES framework accurately predicts a diverse set of atmospheric conditions and in all cases the statistics exhibit good grid resolution independence, even for resolutions that are typically considered coarse. Grid convergence criteria are also discussed.

  5. Nanofilms of hyaluronan/chitosan assembled layer-by-layer: An antibacterial surface for Xylella fastidiosa.

    Science.gov (United States)

    Hernández-Montelongo, Jacobo; Nascimento, Vicente F; Murillo, Duber; Taketa, Thiago B; Sahoo, Prasana; de Souza, Alessandra A; Beppu, Marisa M; Cotta, Monica A

    2016-01-20

    In this work, nanofilms of hyaluronan/chitosan (HA/CHI) assembled layer by layer were synthesized; their application as a potential antimicrobial material was demonstrated for the phytopathogen Xylella fastidiosa, a gram-negative bacterium, here used as a model. For the synthesis, the influence of pH and ionic strength of these natural polymer stem-solutions on final characteristics of the HA/CHI nanofilms was studied in detail. The antibacterial effect was evaluated using widefield fluorescence microscopy. These results were correlated with the chemical properties of the nanofilms, studied by FTIR and Raman spectroscopy, as well as with their morphology and surface properties characterized using SEM and AFM. The present findings can be extended to design and optimize HA/CHI nanofilms with enhanced antimicrobial behavior for other type of phytopathogenic gram-negative bacteria species, such as Xanthomonas citri, Xanthomas campestri and Ralstonia solanacearum. Copyright © 2015 Elsevier Ltd. All rights reserved.

  6. Monodisperse gold nanoparticles formed on bacterial crystalline surface layers (S-layers) by electroless deposition

    Energy Technology Data Exchange (ETDEWEB)

    Dieluweit, S. [Center for Nanobiotechnology, University of Natural Resources and Applied Life Sciences (BOKU), Gregor Mendel-Strasse 33, A-1180 Vienna (Austria); Pum, D. [Center for Nanobiotechnology, University of Natural Resources and Applied Life Sciences (BOKU), Gregor Mendel-Strasse 33, A-1180 Vienna (Austria); Sleytr, U.B. [Center for Nanobiotechnology, University of Natural Resources and Applied Life Sciences (BOKU), Gregor Mendel-Strasse 33, A-1180 Vienna (Austria); Kautek, W. [Department for Physical Chemistry, University of Vienna, Waehringer Strasse 42, A-1090 Vienna (Austria)]. E-mail: wolfgang.kautek@univie.ac.at

    2005-12-15

    The fabrication of patterned arrays of nanoparticles whose electronic, optical and magnetic properties will find technological applications, such as ultra-high-density memories, is currently one of the most important objectives of inorganic material research. In this study, the in situ electroless nucleation of ordered two-dimensional arrays of gold nanoparticles (5 nm in size) by using bacterial S-layers as molecular templates and their characterization by small spot X-ray photoelectron emission spectroscopy (XPS) is presented. This yielded the elemental composition of the nanoclusters, which consisted of almost entirely elemental gold, and possible side reactions on the cluster and protein surface. The preferential deposition of the gold nanoparticles on the S-layer suggests that topography and functional groups are important for superlattice formation.

  7. Atmospheric pressure dielectric barrier discharges for sterilization and surface treatment

    Energy Technology Data Exchange (ETDEWEB)

    Chin, O. H.; Lai, C. K.; Choo, C. Y.; Wong, C. S.; Nor, R. M. [Plasma Technology Research Centre, Physics Department, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Thong, K. L. [Microbiology Division, Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2015-04-24

    Atmospheric pressure non-thermal dielectric barrier discharges can be generated in different configurations for different applications. For sterilization, a parallel-plate electrode configuration with glass dielectric that discharges in air was used. Gram-negative bacteria (Escherichia coli and Salmonella enteritidis) and Gram-positive bacteria (Bacillus cereus) were successfully inactivated using sinusoidal high voltage of ∼15 kVp-p at 8.5 kHz. In the surface treatment, a hemisphere and disc electrode arrangement that allowed a plasma jet to be extruded under controlled nitrogen gas flow (at 9.2 kHz, 20 kVp-p) was applied to enhance the wettability of PET (Mylar) film.

  8. Atomic and molecular layer activation of dielectric surfaces

    Science.gov (United States)

    Senkevich, John Joseph

    Strong interaction between the material deposit and substrate is critical to stable deposits and interfaces. The work presented here focuses on the surface activation of dielectric surfaces and oxidized metal surfaces to promote the chemisorption of palladium (II) hexafluoroacetylacetonate (PdII (hfac)2). The goal is to develop reliable, robust metallization protocols, which enable strong interactions between the metal and substrate. SiO2, air exposed Ta, Trikon, and SiLK were activated with sulfur or phosphorus. Two types of activations were developed; one based on self-assembled chemistry, and the other a plasma-assisted process. Activation of the surface using self-assembly techniques was carried out using mercaptan-terminated silane and tetrasulfide silane. The resulting films were characterized by variable angle spectroscopic ellipsometry, contact angle goniometry, and X-ray photoelectron spectroscopy. Tetrasulfide silane sources films exhibit self-limiting behavior, even in the presence of water vapor; whereas mercaptan-terminated silane sourced films tend to be thicker. The surface activations using atomic layers of sulfur and phosphorus were carried out in a rf plasma chamber using hydrogen sulfide and phosphine sources, respectively. The activations were studied as functions of rf power, system pressure, and substrate material. Results show that higher rf powers and lower system pressures promote greater surface coverages by sulfur with a reduced oxidation state. The activated dielectrics show evidence of PdII(hfac)2 chemisorption, in contrast to non-activated surfaces. The binding energy shift of the Pd3d 5/2 XPS peak towards elemental Pd provides evidence for the dissociative chemisorption of PdII(hfac)2. The extent of dissociation depends on the substrate temperature and the activation method used. The conclusions of the work presented here have implications for metallization using highly polarizable transition metals. Specifically, it can be applied to

  9. Sterilization of Surfaces with a Handheld Atmospheric Pressure Plasma

    Science.gov (United States)

    Hicks, Robert; Habib, Sara; Chan, Wai; Gonzalez, Eleazar; Tijerina, A.; Sloan, Mark

    2009-10-01

    Low temperature, atmospheric pressure plasmas have shown great promise for decontaminating the surfaces of materials and equipment. In this study, an atmospheric pressure, oxygen and argon plasma was investigated for the destruction of viruses, bacteria, and spores. The plasma was operated at an argon flow rate of 30 L/min, an oxygen flow rate of 20 mL/min, a power density of 101.0 W/cm^3 (beam area = 5.1 cm^2), and at a distance from the surface of 7.1 mm. An average 6log10 reduction of viable spores was obtained after only 45 seconds of exposure to the reactive gas. By contrast, it takes more than 35 minutes at 121^oC to sterilize anthrax in an autoclave. The plasma properties were investigated by numerical modeling and chemical titration with nitric oxide. The numerical model included a detailed reaction mechanism for the discharge as well as for the afterglow. It was predicted that at a delivered power density of 29.3 W/cm^3, 30 L/min argon, and 0.01 volume% O2, the plasma generated 1.9 x 10^14 cm-3 O atoms, 1.6 x 10^12 cm-3 ozone, 9.3 x 10^13 cm-3 O2(^1δg), and 2.9 x 10^12 cm-3 O2(^1σ^+g) at 1 cm downstream of the source. The O atom density measured by chemical titration with NO was 6.0 x 10^14 cm-3 at the same conditions. It is believe that the oxygen atoms and the O2(^1δg) metastables were responsible for killing the anthrax and other microorganisms.

  10. Interaction of Convective Organization and Monsoon Precipitation, Atmosphere, Surface and Sea (INCOMPASS)

    Science.gov (United States)

    Turner, A. G.; Bhat, G. S.; Evans, J. G.; Madan, R.; Marsham, J. H.; Martin, G.; Mitra, A. K.; Mrudula, G.; Parker, D. J.; Pattnaik, S.; Rajagopal, E. N.; Taylor, C.; Tripathi, S. N.

    2016-12-01

    INCOMPASS will build on a field and aircraft measurement campaign from the 2016 monsoon onset to better understand and predict monsoon rainfall. The monsoon supplies the majority of water in South Asia, however modelling and forecasting the monsoon from days to the season ahead is limited by large model errors that develop quickly. Likely problems lie in physical parametrizations such as convection, the boundary layer and land surface. At the same time, lack of detailed observations prevents more thorough understanding of monsoon circulation and its interaction with the land surface; a process governed by boundary layer and convective cloud dynamics. From May to July 2016, INCOMPASS used a modified BAe-146 jet aircraft operated by the UK Facility for Airborne Atmospheric Measurements (FAAM), for the first project of this scale in India. The India and UK team flew around 100 hours of science sorties from bases in northern and southern India. Flights from Lucknow in the northern plains took measurements to the west and southeast to allow sampling of the complete contrast from dry desert air to the humid environment over the north Bay of Bengal. These routes were repeated in the pre-monsoon and monsoon phases, measuring contrasting surface and boundary layer structures. In addition, flights from the southern base in Bengaluru measured contrasts from the Arabian Sea, across the intense rains of the Western Ghats mountains, over the rain shadow in southeast India and over the southern Bay of Bengal. Flight planning was performed with the aid of forecasts from a new UK Met Office 4km limited area model. INCOMPASS also installed a network of surface flux towers, as well as operating a cloud-base ceilometer and performing intensive radiosonde launches from a supersite in Kanpur. This presentation will outline preliminary results from the field campaign including new observations of the surface, boundary layer structure and atmospheric profiles together with detailed

  11. Sensitivity analysis of radiative transfer for atmospheric remote sensing in thermal IR: atmospheric weighting functions and surface partials

    Science.gov (United States)

    Ustinov, E. A.

    2003-01-01

    In this presentation, we apply the adjoint sensitivity analysis of radiative transfer in thermal IR to the general case of the analytic evaluation of the weighting functions of atmospheric parameters together with the partial derivatives for the surface parameters. Applications to remote sensing of atmospheres of Mars and Venus are discussed.

  12. Modeling the distribution of ammonia across Europe including bi-directional surface-atmosphere exchange

    NARCIS (Netherlands)

    Wichink Kruit, R.J.; Schaap, M.; Sauter, F.J.; Zanten, M.C. van; Pul, W.A.J. van

    2012-01-01

    A large shortcoming of current chemistry transport models (CTM) for simulating the fate of ammonia in the atmosphere is the lack of a description of the bi-directional surface-atmosphere exchange. In this paper, results of an update of the surface-atmosphere exchange module DEPAC, i.e. DEPosition of

  13. Layer by Layer, Nano-particle "Only" Surface Modification of Filtration Membranes

    Science.gov (United States)

    Escobar-Ferrand, Luis

    Layer by Layer (LbL) deposition using primarily inorganic silica nanoparticles is employed for the modification of polymeric micro and ultrafiltration (MF/UF) membranes to produce thin film composites (TFC) with potential nanofiltration (NF) and reverse osmosis (RO) capabilities.. A variety of porous substrate membranes with different membrane surface characteristics are employed, but exhibiting in common that wicking of water does not readily occur into the pore structure, including polycarbonate track etched (PCTE), polyethersulfone (PES) and sulfonated PES (SPEES) MF/UF membranes. Both spherical (cationic/anionic) and eccentric elongated (anionic) silica nanoparticles are deposited using conditions similar to those reported by Lee et al. Appropriate selection of the pH's for anionic and cationic particle deposition enables the construction of nanoparticle only layers 100--1200 nm in thickness atop the original membrane substrates. The surface layer thickness varies monotonically with the number of bilayers (anionic/cationic deposition cycles) as expected. The deposition process is optimized to eliminate drying induced cracking and to improve mechanical durability via thickness control and post-deposition hydro-thermal treatment. The hydrodynamic permeability of these TFC membranes is measured to evaluate their performance under typical NF operating conditions using dead-end permeation experiments and their performance compared quantitatively with realistic hydrodynamic models, with favorable results. For track etched polycarbonate MF substrates, surface modification causes a permeability reduction of approximately two orders of magnitude with respect to the bare substrates, to values comparable to those for typical commercial NF membranes. Good quantitative agreement with hydrodynamic models with no adjustable parameters was also established for this case, providing indirect confirmation that the LbL deposited surface layers are largely defect (crack) free

  14. Intermittency and energy fluxes in the surface layer of free-surface turbulence

    CERN Document Server

    Troiani, Guido; Olivieri, Angelo; Casciola, Carlo Massimo

    2016-01-01

    By analyzing hot-wire velocity data taken in an open channel flow, an unambiguous definition of surface-layer thickness is here provided in terms of the cross-over scale between backward and forward energy fluxes. It is shown that the turbulence in the surface layer does not conform to the classical description of two-dimensional turbulence, since the direct energy cascade persists at scales smaller than the cross-over scale, comparable with the distance from the free-surface. The multifractal analysis of the one-dimensional surrogate of the turbulent kinetic energy dissipation rate in terms of generalized dimensions and singularity spectrum indicates that intermittency is strongly depleted in the surface layer, as shown by the singularity spectrum contracted to a single point. The combination of intermittency indicators and energy fluxes allowed to identify the specific nature of the surface layer as alternative to classical paradigms of three- and two-dimensional turbulence which cannot fully capture the gl...

  15. Controlled meteorological (CMET) balloon profiling of the Arctic atmospheric boundary layer

    Science.gov (United States)

    Roberts, Tjarda; Hole, Lars; Voss, Paul

    2017-04-01

    We demonstrate profiling of the atmospheric boundary layer over Arctic ice-free and sea-ice covered regions by free-floating controllable CMET balloons. The CMET observations (temperature, humidity, wind-speed, pressure) provide in-situ meteorological datasets in very remote regions for comparison to atmospheric models. Controlled Meteorological (CMET) balloons are small airborne platforms that use reversible lift-gas compression to regulate altitude. These balloons have approximately the same payload mass as standard weather balloons but can float for many days, change altitude on command, and transmit meteorological and system data in near-real time via satellite. Five Controlled Meteorological (CMET) balloons were launched from Ny-Ålesund in Svalbard (Spitsbergen) over 5-12 May 2011 and measured vertical atmospheric profiles (temperature, humidity, wind) over coastal and remote areas to both the east and west. One notable CMET flight achieved a suite of 18 continuous soundings that probed the Arctic atmospheric boundary layer (ABL) over a period of more than 10 h. Profiles from two CMET flights are compared to model output from ECMWF Era-Interim reanalysis (ERA-I) and to a high-resolution (15 km) Arctic System Reanalysis (ASR) product. To the east of Svalbard over sea-ice, the CMET observed a stable ABL profile with a temperature inversion that was reproduced by ASR but not captured by ERA-I. In a coastal ice-free region to the west of Svalbard, the CMET observed a stable ABL with strong wind-shear. The CMET profiles document increases in ABL temperature and humidity that are broadly reproduced by both ASR and ERA-I. The ASR finds a more stably stratified ABL than observed but captured the wind shear in contrast to ERA-I. Detailed analysis of the coastal CMET-automated soundings identifies small-scale temperature and humidity variations with a low-level flow and provides an estimate of local wind fields. We show that CMET balloons are a valuable approach for

  16. Effects of the surface stoichiometry of seeds on GaN layer growth by hydride vapour phase epitaxy.

    Science.gov (United States)

    Wang, B; Zhao, Z D; Xu, W; Sui, Y P; Yu, G H

    2015-05-07

    The effect of the atmosphere in a reactor prior to hydride vapour phase epitaxy on the surface stoichiometry of both the GaN template and layer growth was studied. The surface stoichiometry of metallic Ga layers was clarified by X-ray photoelectron spectroscopy using templates without NH3 protection. The metallic Ga layer acted as a mask and exerted a significant effect on the subsequent epitaxial layer growth mode. GaN grown on the template without protection followed island growth in the initial growth stage. In contrast, GaN epitaxy on the template with NH3 protection quickly converts to pseudo-2D growth. The images of CL illustrate that the GaN epilayer on the template without protection has a lower dislocation density than the GaN epilayer grown on the template with NH3 protection. Reasons behind this effect have been discussed.

  17. Characterization of wake turbulence in a wind turbine array submerged in atmospheric boundary layer flow

    Science.gov (United States)

    Jha, Pankaj Kumar

    Wind energy is becoming one of the most significant sources of renewable energy. With its growing use, and social and political awareness, efforts are being made to harness it in the most efficient manner. However, a number of challenges preclude efficient and optimum operation of wind farms. Wind resource forecasting over a long operation window of a wind farm, development of wind farms over a complex terrain on-shore, and air/wave interaction off-shore all pose difficulties in materializing the goal of the efficient harnessing of wind energy. These difficulties are further amplified when wind turbine wakes interact directly with turbines located downstream and in adjacent rows in a turbulent atmospheric boundary layer (ABL). In the present study, an ABL solver is used to simulate different atmospheric stability states over a diurnal cycle. The effect of the turbines is modeled by using actuator methods, in particular the state-of-the-art actuator line method (ALM) and an improved ALM are used for the simulation of the turbine arrays. The two ALM approaches are used either with uniform inflow or are coupled with the ABL solver. In the latter case, a precursor simulation is first obtained and data saved at the inflow planes for the duration the turbines are anticipated to be simulated. The coupled ABL-ALM solver is then used to simulate the turbine arrays operating in atmospheric turbulence. A detailed accuracy assessment of the state-of-the-art ALM is performed by applying it to different rotors. A discrepancy regarding over-prediction of tip loads and an artificial tip correction is identified. A new proposed ALM* is developed and validated for the NREL Phase VI rotor. This is also applied to the NREL 5-MW turbine, and guidelines to obtain consistent results with ALM* are developed. Both the ALM approaches are then applied to study a turbine-turbine interaction problem consisting of two NREL 5-MW turbines. The simulations are performed for two ABL stability

  18. Investigation of the atmospheric boundary layer dynamics during the ESCOMPTE campaign

    Directory of Open Access Journals (Sweden)

    F. Saïd

    2007-03-01

    Full Text Available This paper presents some results about the behavior of the atmospheric boundary layer observed during the ESCOMPTE experiment. This campaign, which took place in south-eastern France during summer 2001, was aimed at improving our understanding of pollution episodes in relation to the dynamics of the lower troposphere. Using a large data set, as well as a simulation from the mesoscale non-hydrostatic model Meso-NH, we describe and analyze the atmospheric boundary layer (ABL development during two specific meteorological conditions of the second Intensive Observation Period (IOP. The first situation (IOP2a, from 22 June to 23 June corresponds to moderate, dry and cold northerly winds (end of Mistral event, coupled with a sea-breeze in the lower layer, whereas sea-breeze events with weak southerly winds occurred during the second part of the period (IOP2b, from 24 June to 26 June. In this study, we first focus on the validation of the model outputs with a thorough comparison of the Meso-NH simulations with fields measurements on three days of the IOP: 22 June, 23 June and 25 June. We also investigate the structure of the boundary layer on IOP2a when the Mistral is superimposed on a sea breeze. Then, we describe the spatial and diurnal variability of the ABL depths over the ESCOMPTE domain during the whole IOP. This step is essential if one wants to know the depth of the layer where the pollutants can be diluted or accumulated. Eventually, this study intends to describe the ABL variability in relation to local or mesoscale dynamics and/or induced topographic effects, in order to explain pollution transport processes in the low troposphere.

  19. Investigation of the atmospheric boundary layer dynamics during the ESCOMPTE campaign

    Energy Technology Data Exchange (ETDEWEB)

    Said, F.; Campistron, B. [Centre de Recherches Atmospheriques, UMR CNRS 5560, Campistrous (France); Brut, A. [Centre d' Etudes Spatiales de la BIOsphere UMR 5126, Toulouse (France); Cousin, F. [Lab. d' Aerologie, UMR CNRS 5560, Toulouse (France)

    2007-07-01

    This paper presents some results about the behavior of the atmospheric boundary layer observed during the ESCOMPTE experiment. This campaign, which took place in south-eastern France during summer 2001, was aimed at improving our understanding of pollution episodes in relation to the dynamics of the lower troposphere. Using a large data set, as well as a simulation from the mesoscale non-hydrostatic model Meso-NH, we describe and analyze the atmosphere boundary layer (ABL) development during two specific meteorological conditions of the second Intensive Observation Period (IOP). The first situation (IOP2a, from 22 June to 23 June) corresponds to moderate, dry and cold northerly winds (end of Mistral event), coupled with a sea-breeze in the lower layer, whereas sea-breeze events with weak southerly winds occurred during the second part of the period (IOP2b, from 24 June to 26 June). In this study, we first focus on the validation of the model outputs with a thorough comparison of the Meso-NH simulations with fields measurements on three days of the IOP: 22 June, 23 June and 25 June. We also investigate the structure of the boundary layer on IOP2a when the Mistral is superimposed on a sea breeze. Then, we describe the spatial and diurnal variability of the ABL depths over the ESCOMPTE domain during the whole IOP. This step is essential if one wants to know the depth of the layer where the pollutants can be diluted or accumulated. Eventually, this study intends to describe the ABL variability in relation to local or mesoscale dynamics and/or induced topographic effects, in order to explain pollution transport processes in the low troposphere. (orig.)

  20. Investigation of the atmospheric boundary layer dynamics during the ESCOMPTE campaign

    Directory of Open Access Journals (Sweden)

    F. Saïd

    2007-03-01

    Full Text Available This paper presents some results about the behavior of the atmospheric boundary layer observed during the ESCOMPTE experiment. This campaign, which took place in south-eastern France during summer 2001, was aimed at improving our understanding of pollution episodes in relation to the dynamics of the lower troposphere. Using a large data set, as well as a simulation from the mesoscale non-hydrostatic model Meso-NH, we describe and analyze the atmospheric boundary layer (ABL development during two specific meteorological conditions of the second Intensive Observation Period (IOP. The first situation (IOP2a, from 22 June to 23 June corresponds to moderate, dry and cold northerly winds (end of Mistral event, coupled with a sea-breeze in the lower layer, whereas sea-breeze events with weak southerly winds occurred during the second part of the period (IOP2b, from 24 June to 26 June.

    In this study, we first focus on the validation of the model outputs with a thorough comparison of the Meso-NH simulations with fields measurements on three days of the IOP: 22 June, 23 June and 25 June. We also investigate the structure of the boundary layer on IOP2a when the Mistral is superimposed on a sea breeze. Then, we describe the spatial and diurnal variability of the ABL depths over the ESCOMPTE domain during the whole IOP. This step is essential if one wants to know the depth of the layer where the pollutants can be diluted or accumulated. Eventually, this study intends to describe the ABL variability in relation to local or mesoscale dynamics and/or induced topographic effects, in order to explain pollution transport processes in the low troposphere.

  1. Lens epithelial cell response to atmospheric pressure plasma modified poly(methylmethacrylate) surfaces.

    Science.gov (United States)

    D'Sa, Raechelle A; Burke, George A; Meenan, Brian J

    2010-05-01

    Selective control of cellular response to polymeric biomaterials is an important consideration for many ocular implant applications. In particular, there is often a need to have one surface of an ophthalmic implant capable of promoting cell attachment while the other needs to be resistant to this effect. In this study, an atmospheric pressure dielectric barrier discharge (DBD) has been used to modify the surface region of poly(methyl methacrylate) (PMMA), a well established ocular biomaterial, with the aim of promoting a controlled response to human lens epithelial cells (LEC) cultured thereon. The DBD plasma discharge environment has also been employed to chemically graft a layer of poly(ethylene glycol) methyl ether methacrylate (PEGMA) onto the PMMA and the response to LEC likewise determined. Two different molecular weights of PEGMA, namely 1000 and 2000 MW were used in these experiments. The LEC response to DBD treated polystyrene (PS) samples has also been examined as a positive control and to help to further elucidate the nature of the modified surfaces. The LEC adhered and proliferated readily on the DBD treated PMMA and PS surfaces when compared to the pristine polymer samples which showed little or no cell response. The PMMA and PS surfaces that had been DBD grafted with the PEGMA(1000) layer were found to have some adhered cells. However, on closer inspection, these cells were clearly on the verge of detaching. In the case of the PEGMA(2000) grafted surfaces no cells were observed indicating that the higher molecular weight PEGMA has been able to attain a surface conformation that is capable of resisting cell attachment in vitro.

  2. NOAA Climate Data Record (CDR) of Ocean Near Surface Atmospheric Properties, Version 2

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Ocean Surface Bundle (OSB) Climate Data Record (CDR) consist of three parts: sea surface temperature; near-surface wind speed, air temperature, and specific...

  3. 3D Dynamics of Freshwater Lenses in the Near-Surface Layer of the Tropical Ocean

    Science.gov (United States)

    Soloviev, Alexander; Dean, Cayla

    2015-04-01

    Convective rains in the Intertropical Convergence Zone (ITCZ) produce lenses of freshened water on the ocean surface. These lenses are localized in space and typically involve both salinity and temperature anomalies. Due to significant density anomalies, strong pressure gradients develop, which result in lateral spreading of freshwater lenses in a form resembling gravity currents. Gravity currents inherently involve three-dimensional dynamics. As a type of organized structure, gravity currents in the upper layer of the ocean may also interact with, and be shaped by, the ambient oceanic environment and atmospheric conditions. Among the important factors are the background stratification, wind stress, wind/wave mixing and spatially coherent organized motions in the near-surface layer of the ocean. Under certain conditions, a resonant interaction between a propagating freshwater lens and internal waves in the underlying pycnocline (e.g., barrier layer) may develop, whereas interaction with wind stress may produce an asymmetry in the freshwater lens and associated mixing. These two types of interactions working in concert may explain the series of sharp frontal interfaces, which have been observed in association with freshwater lenses during TOGA COARE. In this work, we have conducted a series of numerical experiments using computational fluid dynamics tools. These numerical simulations were designed to elucidate the relationship between vertical mixing and horizontal advection of salinity under various environmental conditions and potential impact on the Aquarius and SMOS satellite image formation. Available near-surface data from field experiments served as a guidance for numerical simulations. The results of this study indicate that 3D dynamics of freshwater lenses are essential within a certain range of wind/wave conditions and the freshwater influx in the surface layer of the ocean.

  4. An Edge-Referenced Surface Fresh Layer in the Seasonal Ice Zone

    Science.gov (United States)

    Dewey, S.; Morison, J.

    2016-02-01

    Seasonal Ice Zone Reconnaissance Surveys (SIZRS) of the Beaufort Sea aboard U.S. Coast Guard Arctic Domain Awareness flights were made monthly from June to October, 2012 to 2015. The seasonal ice zone (SIZ), where ice melts and reforms annually, encompasses the marginal ice zone (MIZ). Thus SIZRS tracks interannual MIZ conditions, providing a regional context for smaller-scale MIZ processes. Observations with Air eXpendable CTDs (AXCTDs) reveal a salinity pattern associated with large-scale gyre circulation as well as the seasonal formation of a 20m-deep fresh layer relative to the ice edge. Repeat occupations of the SIZRS lines from 72°N to 76°N on 140°W and 150°W allow us to relate observed hydrography to atmospheric indices. Using this relationship, we separate basin-wide salinity signals from the fresh layer associated with the ice edge. While this layer extends under the ice edge as the melt season progresses, its presence is independent of year and absolute latitude north. Within this fresh layer, we correlate average salinity to distance from the ice edge. To test a formation mechanism for this layer, a 1-D Price-Weller-Pinkel (PWP) model adapted for ice-covered seas simulates mixing processes in the top 100 meters of the ocean. Surface forcing fluxes are taken from the Marginal Ice Zone Modeling and Assimilation System (MIZMAS). PWP output supports local formation of the layer by ice melt. This layer may have implications for the behavior of freshwater in the Beaufort Gyre as the local SIZ grows and persists.

  5. Secondary flows in turbulent boundary layers over longitudinal surface roughness

    Science.gov (United States)

    Hwang, Hyeon Gyu; Lee, Jae Hwa

    2018-01-01

    Direct numerical simulations of turbulent boundary layers over longitudinal surface roughness are performed to investigate the impact of the surface roughness on the mean flow characteristics related to counter-rotating large-scale secondary flows. By systematically changing the two parameters of the pitch (P) and width (S) for roughness elements in the ranges of 0.57 ≤P /δ ≤2.39 and 0.15 ≤S /δ ≤1.12 , where δ is the boundary layer thickness, we find that the size of the secondary flow in each case is mostly determined by the value of P - S, i.e., the valley width, over the ridge-type roughness. However, the strength of the secondary flows on the cross-stream plane relative to the flow is increased when the value of P increases or when the value of S decreases. In addition to the secondary flows, additional tertiary and quaternary flows are observed both above the roughness crest and in the valley as the values of P and S increase further. Based on an analysis using the turbulent kinetic energy transport equation, it is shown that the secondary flow over the ridge-type roughness is both driven and sustained by the anisotropy of turbulence, consistent with previous observations of a turbulent boundary layer over strip-type roughness [Anderson et al., J. Fluid Mech. 768, 316 (2015), 10.1017/jfm.2015.91]. Careful inspection of the turbulent kinetic energy budget reveals that the opposite rotational sense of the secondary flow between the ridge- and strip-type roughness elements is primarily attributed to the local imbalance of energy budget created by the strong turbulent transport term over the ridge-type roughness. The active transport of the kinetic energy over the ridge-type roughness is closely associated with the upward deflection of spanwise motions in the valley, mostly due to the roughness edge.

  6. Filtering of cyclical surface forcings in a layered vadose zone

    Science.gov (United States)

    Dickinson, J.; Ferre, T. P. A.

    2016-12-01

    Infiltration and downward percolation of water in the vadose zone are important processes that may limit availability of water resources in many areas around the world. However, estimates of these fluxes are often uncertain. Climate projections can include changes in both the timing and magnitude of rainfall, which increases the importance of understanding how the vadose zone filters these infiltration signals to better predict the impacts of climate change on groundwater resources. In this presentation, we present a simplified analytical approach that provides insight into how cyclical infiltration forcings at land surface are filtered in a layered vadose zone in terms of changes in the timing and magnitude of hydrologic responses. Our approach provides an alternative to simulating vadose zone flow using computationally-expensive numerical models that solve the Richards equation in investigations of the possible impact of climatic forcings. We use superposition of one-dimensional analytical solutions for sinusoidal infiltration where each solution represents a single soil in a layered profile. The analytical solution uses a linearization of the Richards equation and assumes that the effects of transitioning soil-water properties between layers on flow interfaces are negligible. We evaluate the limit of these approximations by comparing of results from the unsaturated flow numerical model HYDRUS-1D which uses the full Richards equation. We compare (1) the depth at which flux variations become steady, and (2) the travel time of wetting fronts to reach a depth of 10 m. We tested our solution with periods from 30 days to 365 days and fluxes common in arid and semiarid environments (0 mm/d to 2 mm/d) and found that the solution is reasonably accurate (error less than a factor of 2). Using the analytical solution, we investigate the filtering properties of the vadose zone in Central Valley, California and identify areas where surface forcings are essentially damped and

  7. Investigation of Turbulence Parametrization Schemes with Reference to the Atmospheric Boundary Layer Over the Aegean Sea During Etesian Winds

    Science.gov (United States)

    Dandou, A.; Tombrou, M.; Kalogiros, J.; Bossioli, E.; Biskos, G.; Mihalopoulos, N.; Coe, H.

    2017-08-01

    The spatial structure of the marine atmospheric boundary layer (MABL) over the Aegean Sea is investigated using the Weather Research and Forecasting (WRF) mesoscale model. Two `first-order' non-local and five `1.5-order' local planetary boundary-layer (PBL) parametrization schemes are used. The predictions from the WRF model are evaluated against airborne observations obtained by the UK Facility for Airborne Atmospheric Measurements BAe-14 research aircraft during the Aegean-GAME field campaign. Statistical analysis shows good agreement between measurements and simulations especially at low altitude. Despite the differences between the predicted and measured wind speeds, they reach an agreement index of 0.76. The simulated wind-speed fields close to the surface differ substantially among the schemes (maximum values range from 13 to 18 m s^{-1} at 150-m height), but the differences become marginal at higher levels. In contrast, all schemes show similar spatial variation patterns in potential temperature fields. A warmer (1-2 K) and drier (2-3 g kg^{-1}) layer than is observed, is predicted by almost all schemes under stable conditions (eastern Aegean Sea), whereas a cooler (up to 2 K) and moister (1-2 g kg^{-1}) layer is simulated under near-neutral to nearly unstable conditions (western Aegean Sea). Almost all schemes reproduce the vertical structure of the PBL and the shallow MABL (up to 300 m) well, including the low-level jet in the eastern Aegean Sea, with non-local schemes being closer to observations. The simulated PBL depths diverge (up to 500 m) due to the different criteria applied by the schemes for their calculation. Under stable conditions, the observed MABL depth corresponds to the height above the sea surface where the simulated eddy viscosity reaches a minimum; under neutral to slightly unstable conditions this is close to the top of the simulated entrainment layer. The observed sensible heat fluxes vary from -40 to 25 W m^{-2}, while the simulated

  8. Crystalline Bacterial Surface Layer (S-Layer) Opens Golden Opportunities for Nanobiotechnology in Textiles.

    Science.gov (United States)

    Asadi, Narges; Chand, Nima; Rassa, Mehdi

    2015-12-01

    This study focuses on the successful recrystallization of bacterial S-layer arrays of the Lactobacillus acidophilus ATCC 4356 at textile surfaces to create a novel method and material. Optimum bacterial growth was obtained at approximately 45 °C, pH 5.0, and 14 h pi. The cells were resuspended in guanidine hydrochloride and the 43 kDa S-protein was dialyzed and purified. The optimum reassembly on the polypropylene fabric surface in terms of scanning electron microscopy (SEM), reflectance, and uniformity (spectrophotometry) was obtained at 30 °C, pH 5.0 for 30 minutes in the presence of 2 gr/l (liquor ratio; 1:40) of the S-protein. Overall, our data showed that the functional aspects and specialty applications of the fabric would be very attractive for the textile and related sciences, and result in advanced technical textiles.

  9. Aspects of atmospheric turbulence related to scintillometry

    NARCIS (Netherlands)

    Braam, M.

    2014-01-01

    Aspects of atmospheric turbulence related to scintillometry Atmospheric turbulence is the main vertical transport mechanism in the atmospheric boundary layer. The surface fluxes related to this turbulent transport are the sensible (

  10. Aluminum metal surface cleaning and activation by atmospheric-pressure remote plasma

    Energy Technology Data Exchange (ETDEWEB)

    Muñoz, J., E-mail: jmespadero@uco.es; Bravo, J.A.; Calzada, M.D.

    2017-06-15

    Highlights: • Atmospheric-pressure postdischarges have been applied on aluminium surfaces. • The outer hydrocarbon layer is reduced by the action of the postdischarge. • The treatment promotes the appearance of hydrophilic OH radicals in the surface. • Effectivity for distances up to 5 cm allows for treating irregular surfaces. • Ageing in air due to the disappearance of OH radicals has been reported. - Abstract: The use of the remote plasma (postdischarge) of argon and argon-nitrogen microwave plasmas for cleaning and activating the surface of metallic commercial aluminum samples has been studied. The influence of the nitrogen content and the distance between the treated samples and the end of the discharge on the hydrophilicity and the surface energy has been analyzed by means of the sessile drop technique and the Owens-Wendt method. A significant increase in the hydrophilicity has been noted in the treated samples, together with an increase in the surface energy from values around 37 mJ/m{sup 2} to 77 mJ/m{sup 2}. Such increase weakly depends on the nitrogen content of the discharge, and the effectivity of the treatment extends to distances up to 5 cm from the end of the discharge, much longer than those reported in other plasma-based treatments. The analysis of the treated samples using X-ray photoelectron spectroscopy reveals that such increase in the surface energy takes place due to a reduction of the carbon content and an increase in the amount of OH radicals in the surface. These radicals tend to disappear within 24–48 h after the treatment when the samples are stored in contact with ambient air, resulting in the ageing of the treated surface and a partial retrieval of the hydrophobicity of the surface.

  11. Deposition rates of viruses and bacteria above the atmospheric boundary layer.

    Science.gov (United States)

    Reche, Isabel; D'Orta, Gaetano; Mladenov, Natalie; Winget, Danielle M; Suttle, Curtis A

    2018-01-29

    Aerosolization of soil-dust and organic aggregates in sea spray facilitates the long-range transport of bacteria, and likely viruses across the free atmosphere. Although long-distance transport occurs, there are many uncertainties associated with their deposition rates. Here, we demonstrate that even in pristine environments, above the atmospheric boundary layer, the downward flux of viruses ranged from 0.26 × 10 9 to >7 × 10 9  m -2 per day. These deposition rates were 9-461 times greater than the rates for bacteria, which ranged from 0.3 × 10 7 to >8 × 10 7  m -2 per day. The highest relative deposition rates for viruses were associated with atmospheric transport from marine rather than terrestrial sources. Deposition rates of bacteria were significantly higher during rain events and Saharan dust intrusions, whereas, rainfall did not significantly influence virus deposition. Virus deposition rates were positively correlated with organic aerosols 0.7 μm, implying that viruses could have longer residence times in the atmosphere and, consequently, will be dispersed further. These results provide an explanation for enigmatic observations that viruses with very high genetic identity can be found in very distant and different environments.

  12. A consistent turbulence formulation for the dynamic wake meandering model in the atmospheric boundary layer

    DEFF Research Database (Denmark)

    Keck, Rolf-Erik; Veldkamp, Dick; Wedel-Heinen, Jens Jakob

    evolution 4. atmospheric stability effects on wake deficit evolution and meandering The conducted research is to a large extent based on detailed wake investigations and reference data generated through computational fluid dynamics simulations, where the wind turbine rotor has been represented...... as a standalone flow-solver for the velocity and turbulence distribution, and power production in a wind farm. The performance of the standalone implementation is validated against field data, higher-order computational fluid dynamics models, as well as the most common engineering wake models in the wind industry....... 2. The EllipSys3D actuator line model, including the synthetic methods used to model atmospheric boundary layer shear and turbulence, is verified for modelling the evolution of wind turbine wake turbulence by comparison to field data and wind tunnel experiments. 3. A two-dimensional eddy viscosity...

  13. A detailed look beneath the surface: Evidence of a surface reconstruction beneath a capping layer

    Energy Technology Data Exchange (ETDEWEB)

    Krull, D., E-mail: dominique.krull@tu-dortmund.de [Lehrstuhl für Experimentelle Physik I and DELTA, Dortmund University of Technology, Otto-Hahn-Str. 4, 44221 Dortmund (Germany); Tesch, M.F. [University of Applied Sciences Münster, Stegerwaldstr. 39, 48565 Steinfurt (Germany); Schönbohm, F.; Lühr, T.; Keutner, C.; Berges, U. [Lehrstuhl für Experimentelle Physik I and DELTA, Dortmund University of Technology, Otto-Hahn-Str. 4, 44221 Dortmund (Germany); Mertins, H.-Ch. [University of Applied Sciences Münster, Stegerwaldstr. 39, 48565 Steinfurt (Germany); Westphal, C. [Lehrstuhl für Experimentelle Physik I and DELTA, Dortmund University of Technology, Otto-Hahn-Str. 4, 44221 Dortmund (Germany)

    2016-03-30

    Highlights: • Demonstration of a detailed look into internal interface structures. • Close-up view to an internal surface beneath a capping layer. • Resolving of inter-diffusion layers. • Imaging of phase-transition (local layers). • Demonstration of achieving magnetic information of an interlayer. - Abstract: Many physical effects are strongly depending on the composition of the interfaces between separating layers. Hence, the knowledge of the interfacial characteristics such as structure, chemical bonds, or magnetic properties of the corresponding materials is essential for an understanding and optimization of these effects. This study reports on a combined magnetic and structural analysis using X-ray photoelectron diffraction (XPD) and transverse magneto-optical Kerr effect (T-MOKE). The information depth of these methods is demonstrated by investigating the uppermost GaAs(001) layer beneath a Fe-film and the interfacial regimes of Fe/GaAs(001) beneath an MgO capping layer. Iron was prepared on a clean GaAs(001) surface and a GaAs(001)-(4 × 2)-reconstructed surface. Beneath the Fe-film, the (4 × 2)-reconstruction is not lifted, which is clearly shown by the diffraction pattern of the GaAs(4 × 2)-Fe surface. It is shown that Fe inter-diffusion, resulting in an amorphous interface, is almost prevented by the Ga-rich reconstruction. The magneto-optical measurements with T-MOKE clearly demonstrated the Fe-interlayer in a ferromagnetic state. We find no evidence for magnetic properties neither within the signal of the GaAs-substrate nor the MgO-film.

  14. Translation of Land Surface Model Accuracy and Uncertainty into Coupled Land-Atmosphere Prediction

    Science.gov (United States)

    Santanello, Joseph A.; Kumar, Sujay; Peters-Lidard, Christa D.; Harrison, Kenneth W.; Zhou, Shuija

    2012-01-01

    Land-atmosphere (L-A) Interactions playa critical role in determining the diurnal evolution of both planetary boundary layer (PBL) and land surface heat and moisture budgets, as well as controlling feedbacks with clouds and precipitation that lead to the persistence of dry and wet regimes. Recent efforts to quantify the strength of L-A coupling in prediction models have produced diagnostics that integrate across both the land and PBL components of the system. In this study, we examine the impact of improved specification of land surface states, anomalies, and fluxes on coupled WRF forecasts during the summers of extreme dry (2006) and wet (2007) land surface conditions in the U.S. Southern Great Plains. The improved land initialization and surface flux parameterizations are obtained through the use of a new optimization and uncertainty estimation module in NASA's Land Information System (US-OPT/UE), whereby parameter sets are calibrated in the Noah land surface model and classified according to a land cover and soil type mapping of the observation sites to the full model domain. The impact of calibrated parameters on the a) spinup of the land surface used as initial conditions, and b) heat and moisture states and fluxes of the coupled WRF Simulations are then assessed in terms of ambient weather and land-atmosphere coupling along with measures of uncertainty propagation into the forecasts. In addition, the sensitivity of this approach to the period of calibration (dry, wet, average) is investigated. Finally, tradeoffs of computational tractability and scientific validity, and the potential for combining this approach with satellite remote sensing data are also discussed.

  15. Chemical grafting of poly(ethylene glycol) methyl ether methacrylate onto polymer surfaces by atmospheric pressure plasma processing.

    Science.gov (United States)

    D'Sa, Raechelle A; Meenan, Brian J

    2010-02-02

    This article reports the use of atmospheric pressure plasma processing to induce chemical grafting of poly(ethylene glycol) methyl ether methacrylate (PEGMA) onto polystyrene (PS) and poly(methyl methacrylate) (PMMA) surfaces with the aim of attaining an adlayer conformation which is resistant to protein adsorption. The plasma treatment was carried out using a dielectric barrier discharge (DBD) reactor with PEGMA of molecular weights (MW) 1000 and 2000, PEGMA(1000) and PEGMA(2000), being grafted in a two step procedure: (1) reactive groups are generated on the polymer surface followed by (2) radical addition reactions with the PEGMA. The surface chemistry, coherency, and topography of the resulting PEGMA grafted surfaces were characterized by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and atomic force microscopy (AFM), respectively. The most coherently grafted PEGMA layers were observed for the 2000 MW PEGMA macromolecule, DBD processed at an energy dose of 105.0 J/cm(2) as indicated by ToF-SIMS images. The effect of the chemisorbed PEGMA layer on protein adsorption was assessed by evaluating the surface response to bovine serum albumin (BSA) using XPS. BSA was used as a model protein to determine the grafted macromolecular conformation of the PEGMA layer. Whereas the PEGMA(1000) surfaces showed some protein adsorption, the PEGMA(2000) surfaces appeared to absorb no measurable amount of protein, confirming the optimum surface conformation for a nonfouling surface.

  16. Surface Modification of Dental Titanium Implant by Layer-by-Layer Electrostatic Self-Assembly

    Directory of Open Access Journals (Sweden)

    Quan Shi

    2017-08-01

    Full Text Available In vivo implants that are composed of titanium and titanium alloys as raw materials are widely used in the fields of biology and medicine. In the field of dental medicine, titanium is considered to be an ideal dental implant material. Good osseointegration and soft tissue closure are the foundation for the success of dental implants. Therefore, the enhancement of the osseointegration and antibacterial abilities of titanium and its alloys has been the focus of much research. With its many advantages, layer-by-layer (LbL assembly is a self-assembly technique that is used to develop multilayer films based on complementary interactions between differently charged polyelectrolytes. The LbL approach provides new methods and applications for the surface modification of dental titanium implant. In this review, the application of the LbL technique to surface modification of titanium including promoting osteogenesis and osseointegration, promoting the formation and healing of soft tissues, improving the antibacterial properties of titanium implant, achieving local drug delivery and sustained release is summarized.

  17. Atmospheric correction for sea surface temperature retrieval from ...

    Indian Academy of Sciences (India)

    using Very High Resolution Radiometer (VHRR) single window channel radiance data onboard Kalpana satellite .... Atmospheric correction (WV in equation 1) is ... Atmospheric correction for SST retrieval. 341. Table 2. Characteristics of VHRR sensor onboard Kalpana satellite. Channel wavelength. Resolution. Sensor.

  18. Impact of the atmospheric boundary layer profile on the ventilation of a cubic building with two large opposite openings

    OpenAIRE

    Bastide, Alain; Lucas, Franck; Boyer, Harry

    2014-01-01

    International audience; The aim of this paper is to show the influence of the atmospheric boundary layer profile on the distribution of velocity in a building having two large openings. The knowledge of the flow form inside a building is useful to define a thermal environment favourable with thermal comfort and good air quality. In computational fluid dynamics, several profiles of atmospheric boundary layer can be used like logarithmic profiles or power profiles. This paper shows the impact o...

  19. Two-dimensional modeling of thermal inversion layers in the middle atmosphere of Mars

    Science.gov (United States)

    Theodore, B.; Chassefiere, E.

    1993-01-01

    There is some evidence that the thermal structure of the martian middle atmosphere may be altered in a significant way by the general circulation motions. Indeed, while it is well known that the circulation in the meridional plane is responsible for the reversal of the latitudinal thermal gradient at the solstice through the adiabatic heating due to sinking motions above the winter pole, here we want to emphasize that a likely by-product effect could be the formation of warm layers, mainly located in the winter hemisphere, and exhibiting an inversion of the vertical thermal gradient.

  20. Atmospheric boundary layer measurements during summer MONEX 79 at Digha, India

    Energy Technology Data Exchange (ETDEWEB)

    SethuRaman, S.; Michael, P.; Tuthill, W.A.; McNeil, J.

    1979-11-01

    Marine boundary layer experiments conducted over the Bay of Bengal at Digha Beach, West Bengal, India, as part of the International Monsoon Experiments (MONEX 79) are described. The experiments consisted of measurements of atmospheric turbulence and fluxes of momentum, heat, and water vapor from a 10-m-high coastal meteorological tower. Mean meteorological parameters were measured with an automated electronic weather station. Wind speed and direction profiles were obtained with pilot balloon soundings. Some typical tropical meteorological features photographed during the experiment are also presented.

  1. The study of the effects of sea-spray drops on the marine atmospheric boundary layer by direct numerical simulation

    Science.gov (United States)

    Druzhinin, Oleg A.; Troitskaya, Yuliya I.; Zilitinkevich, Sergej S.

    2017-04-01

    Detailed knowledge of the interaction of wind with surface water waves is necessary for correct parameterization of turbulent exchange at the air-sea interface in prognostic models. At sufficiently strong winds, sea-spray-generated droplets interfere with the wind-waves interaction. The results of field experiments and laboratory measurements (Andreas et al., JGR 2010) show that mass fraction of air-borne spume water droplets increases with the wind speed and their impact on the carrier air-flow may become significant. Phenomenological models of droplet-laden marine atmospheric boundary layer (Kudryavtsev & Makin, Bound.-Layer Met. 2011) predict that droplets significantly increase the wind velocity and suppress the turbulent air stress. The results of direct numerical simulation (DNS) of a turbulent particle-laden Couette flow over a flat surface show that inertial particles may significantly reduce the carrier flow vertical momentum flux (Richter & Sullivan, GRL 2013). The results also show that in the range of droplet sizes typically found near the air-sea interface, particle inertial effects are significant and dominate any particle-induced stratification effects. However, so far there has been no attempt to perform DNS of a droplet-laden air-flow over waved water surface. The objective of the present paper is to elucidate possible effects of sea spray on the momentum transfer in marine boundary layer under strong wind-forcing conditions by performing direct numerical simulation (DNS) of turbulent, droplet-laden air-flow over a waved water surface. Three-dimensional, turbulent Couette air-flow is considered in DNS as a model of a constant-flux layer in the atmospheric surface layer. Two-dimensional stationary waves at the water surface are prescribed and assumed to be unaffected by the air-flow and/or droplets. Droplets are considered as non-deformable spheres and tracked in a Lagrangian framework, and their impact on the carrier flow is modeled with the use of

  2. Statistical-mechanical approach to study the hydrodynamic stability of the stably stratified atmospheric boundary layer

    Science.gov (United States)

    Nevo, G.; Vercauteren, N.; Kaiser, A.; Dubrulle, B.; Faranda, D.

    2017-08-01

    We study the hydrodynamic equilibrium properties of the stably stratified atmospheric boundary layer from measurements obtained in the Snow-Horizontal Array Turbulence Study campaign at the Plaine Morte Glacier in the Swiss Alps. Our approach is based on a combination of dynamical systems techniques and statistical analysis. The main idea is to measure the deviations from the behavior expected by a turbulent observable when it is close to a transition between different metastable states. We first assess the performance of our method on the Lorenz attractor, then on a turbulent flow. The results show that the method recognizes subtle differences among different stable boundary layer turbulence regimes and may be used to help characterize their transitions.

  3. Differences of atmospheric boundary layer characteristics between pre-monsoon and monsoon period over the Erhai Lake

    Science.gov (United States)

    Xu, Lujun; Liu, Huizhi; Du, Qun; Wang, Lei; Yang, Liu; Sun, Jihua

    2018-01-01

    The differences in planetary boundary layer characteristics, in particular atmospheric boundary layer height (ABLH), humidity, and local circulations in pre-monsoon and monsoon period over the Erhai Lake, were simulated by the lake-atmosphere coupled model WRF v3.7.1. No lake simulations were also conducted to investigate lake effects over complex topography. During pre-monsoon period, local circulation was fully developed under weak synoptic system. The ABLH ran up to 2300 m or so. During monsoon period, temperature difference between land and lake became smaller, resulting in weaker local circulations. The height of circulation reduced by 500 m, and ABLH ran up to 1100 m during the day. Enhanced soil moisture and low surface temperature due to monsoon rainfalls in July could be the main reason for the slightly lower ABLH over the Erhai Lake area. Specific humidity of the boundary layer increased 8.8 g kg-1 or so during monsoon period. The Erhai Lake enlarged thermal contrast between valley and mountain slope in the Dali Basin. The lake reduced air temperature by 2 3 °C during daytime and increased air temperature by nearly 2 °C in the evening. Due to its small roughness length and large thermal capacity, the Erhai Lake enlarged lake-land temperature difference and local wind speed. A cyclonic circulation was maintained by the combination of mountain breeze and land breeze in the south of the lake. The lake decreased air temperature, increased specific humidity, and reduced ABLH during daytime, whereas the opposite effect is presented at night.

  4. Periodic bedforms generated by sublimation on terrestrial and martian ice sheets under the influence of the turbulent atmospheric boundary layer

    Science.gov (United States)

    Bordiec, Maï; Carpy, Sabrina; Perret, Laurent; Bourgeois, Olivier; Massé, Marion

    2017-04-01

    The redistribution of surface ice induced the wind flow may lead to the development and migration of periodic bedforms, or "ice ripples", at the surface of ice sheets. In certain cold and dry environments, this redistribution need not involve solid particle transport but may be dominated by sublimation and condensation, inducing mass transfers between the ice surface and the overlying steady boundary layer turbulent flow. These mass transfers diffuse the water vapour sublimated from the ice into the atmosphere and become responsible for the amplification and propagation of ripples in a direction perpendicular to their crests. Such ice ripples, 24 cm in wavelength, have been described in the so-called Blue Ice Areas of Antarctica. In order to understand the mechanisms that generate and develop these periodic bedforms on terrestrial glaciers and to evaluate the plausibility that similar bedforms may develop on Mars, we performed a linear stability analysis applied to a turbulent boundary layer flow perturbed by a wavy ice surface. The model is developed as follow. We first solve the flow dynamics using numerical methods analogous to those used in sand wave models assuming that the airflow is similar in both problems. We then add the transport/diffusion equation of water vapour following the same scheme. We use the Reynolds-averaged description of the equation with a Prandtl-like closure. We insert a damping term in the exponential formula of the Van Driest mixing length, depending on the pressure gradient felt by the flow and related to the thickness of the viscous sublayer at the ice-atmosphere interface. This formulation is an efficient way to properly represent the transitional regime under which the ripples grow. Once the mass flux of water vapour is solved, the phase shift between the ripples crests and the maximum of the flux can be deduced for different environments. The temporal evolution of the ice surface can be expressed from these quantities to infer the

  5. Trends in surface engineering of biomaterials: atmospheric pressure plasma deposition of coatings for biomedical applications

    Science.gov (United States)

    da Ponte, G.; Sardella, E.; Fanelli, F.; D'Agostino, R.; Favia, P.

    2011-11-01

    Cold plasma processes for surface engineering of biomaterials and biomedical devices are traditionally performed at low pressure; more and more, though, surface modification plasma processes at atmospheric pressure are also gaining popularity. This short review is aimed to list briefly atmospheric pressure plasma processes reported, in the last decade, for adapting the surface of materials to the best interactions with cells, bacteria and biomolecules.

  6. Characteristics of the atmospheric boundary layer over a scots pine forest

    Energy Technology Data Exchange (ETDEWEB)

    Schindler, D.

    2004-06-01

    The atmospheric boundary layer is structured vertically into several conceptual sublayers because the main airflow characteristics, e.g. the velocity field, air temperature, and air moisture, show different height dependent features. To investigate mean airflow characteristics over a Scots pine forest up to several stand heights, remote sensing and in situ measurements (profile and eddy covariance method) were conducted at the forest meteorological experimental site Hartheim in the Upper Rhine Valley. This methodological combination enables the continuous measurement of the main airflow characteristics exceeding the measuring range of tower-based measurements. Up to now airflow characteristics of the atmospheric boundary layer over forests exceeding the range of tower-based instrumentation are little experimentally studied because - remote sensing devices for operational use are available only for a short time, - of the extensive infrastructure and the problematic experimental setup. Therefore, airflow characteristics above and within forests were often studied based on selected time series and in a narrow range of atmospheric stability conditions when air-flow characteristics were most pronounced (Lu and Fitzjarrald, 1994; Brunet and Irvine, 2000). Furthermore, most of the knowledge of turbulent airflow characteristics and air mass exchange processes between tall plant canopies and the atmosphere has been gained of studies in relatively dense plant canopies (Green et al., 1995; Poggi et al., 2004). Few studies investigated turbulence characteristics in thinly stocked plant canopies such as the Hartheim Scots pine forest. Starting from these deficits the aim of this study is to examine airflow characteristics above and within the Hartheim Scots pine forest the under more general conditions as a function of - atmospheric stability conditions, - seasonal dynamics, up to a height of 200 m a.g.l. Target quantities are variables, which are suitable to describe the

  7. New Concepts for Studying Land-Surface-Atmosphere Feedback Based on a new Lidar Synergy and Grey Zone Simulations

    Science.gov (United States)

    Wulfmeyer, Volker

    2015-04-01

    Improved understanding and simulations of land-surface-atmosphere feedback processes are essential for predicting extreme weather events and the changes of the water cycle in the era of climate change. This requires observations of the surface energy balance closure and of the structure of the atmospheric boundary layer simultaneously. In this presentation, a new strategy is introduced for studying land-surface exchange and entrainment processes in the convective boundary layer (CBL) over complex terrain combining a new generation of remote sensing and model systems. The sensor synergy consists of combination of scanning Doppler lidar (DL), water-vapor differential absorption lidar (WVDIAL), and temperature rotational Raman lidar (TRRL) systems, which are capable of measuring 2D fields of surface and entrainment fluxes, supported by surface in-situ measurements. It is demonstrated that the WVDIAL and the TRRL have currently worldwide the highest resolution and accuracy of water-vapor and temperature profiling using remote sensing systems during daytime. Based on recent and upcoming field efforts, particularly the Surface Atmospheric Boundary Layer Exchange (SABLE) campaign in August 2014, it is shown that with these active remote sensing systems, both sensible and latent heat flux profiles in the convective boundary layer can be measured, what is to our knowledge for the first time. Furthermore, by a sophisticated combination of surface scans, surface momentum, heat, and latent heat fluxes can be determined. These observations will be complemented with a hierarchy of simulations based on the WRF-NOAH-MP-HYDRO model system, which includes new dynamic parameterizations for crop roots and leaf areas as well as a consistent simulation of the water cycle through all compartments of the soil-vegetation-atmosphere continuum. For comparisons with field data, the model system is operated with a rapid update cycle using 3D variational data assimilation (3DVAR). Model

  8. Surface analysis of 316 stainless steel treated with cold atmospheric plasma

    Energy Technology Data Exchange (ETDEWEB)

    Williams, David F., E-mail: david.williams@surrey.ac.uk [Department of Mechanical Engineering Sciences, University Of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); TWI Ltd Granta Park Great Abington, Cambridge CB21 6AL (United Kingdom); Kellar, Ewen J.C. [TWI Ltd Granta Park Great Abington, Cambridge CB21 6AL (United Kingdom); Jesson, David A.; Watts, John F. [Department of Mechanical Engineering Sciences, University Of Surrey, Guildford, Surrey GU2 7XH (United Kingdom)

    2017-05-01

    Highlights: • Reduction in carbon contamination from ∼80 at.% to 40 at.% after 15 s treatment. • Associated carbon thickness reduction from 4.5 nm to 0.5 nm. • Area treated by torch has a diameter of 11 mm measured using imaging XPS. - Abstract: The surface of 316 stainless steel has been modified using cold atmospheric plasma (CAP) to increase the surface free energy (by cleaning the and chemically activating the surface)IN preparation for subsequent processes such as painting, coating or adhesive bonding. The analyses carried out, on CAP treated 316 stainless steel surfaces, includes X-ray photoelectron spectroscopy (XPS), imaging XPS (iXPS), and surface free energy (SFE) analysis using contact angle measurements. The CAP treatment is shown to increase the SFE of as-received 316 stainless steel from ∼39 mJ m{sup −1} to >72 mJ m{sup −1} after a short exposure to the plasma torch. This was found to correlate to a reduction in adventitious carbon, as determined by XPS analysis of the surface. The reduction from ∼90 at% to ∼30% and ∼39 at%, after being plasma treated for 5 min and 15 s respectively, shows that the process is relatively quick at changing the surface. It is suggested that the mechanism that causes the increase in surface free energy is chain scission of the hydrocarbon contamination triggered by free electrons in the plasma plume followed by chemical functionalisation of the metal oxide surface and some of the remaining carbon contamination layer.

  9. A Novel Concept for Observing Land-Surface-Atmosphere Feedback Based on a Synergy of Scanning Lidar Systems

    Science.gov (United States)

    Wulfmeyer, V.; Turner, D. D.; Mauder, M.; Behrendt, A.; Ingwersen, J.; Streck, T.

    2015-12-01

    Improved simulations of land-surface-atmosphere interaction are fundamental for improving weather forecast and climate models. This requires observations of 2D fields of surface fluxes and the 3D structure of the atmospheric boundary layer simultaneously. A novel strategy is introduced for studying land-surface exchange and entrainment processes in the convective boundary layer (CBL) over complex terrain by means of a new generation of remote sensing systems. The sensor synergy consists of scanning Doppler lidar (DL), water-vapor differential absorption lidar (WVDIAL), and temperature rotational Raman lidar (TRRL) systems supported by surface in-situ measurements. The 2D measurements of surface fluxes are realized by the operation of a DL, a WVDIAL, and a TRRL along the same line-of-sight (LOS) in a range-height-indicator (RHI) mode whereas the other DL is performing a series of cross track RHI scans along this LOS. This new setup enables us to determine the friction velocity as well as surface sensible and latent heat fluxes by closing the complete set of Monin-Obukhov similarity relationships under a variety of surface layer stability conditions and different land cover and soil properties. As this closure is performed at all DL crossing points along the LOS, this is a strategy towards a 2D mapping of surface fluxes entirely based on remote sensing systems. Further details are presented at the conference. The second configuration is the simultaneous vertical profiling of vertical wind, humidity and temperature by DL, WVDIAL and TRRL so that latent heat and sensible heat flux profiles as well as a variety of different turbulent moments can be measured in the CBL. Consequently, by alternating of RHI scanning and vertical pointing modes, entrainment fluxes and surface fluxes can be measured almost simultaneously. This novel strategy has been realized for the first time during the Surface Atmospheric Boundary Layer Exchange (SABLE) campaign in the Kraichgau region

  10. Thin hydroxyapatite surface layers on titanium produced by ion implantation

    CERN Document Server

    Baumann, H; Bilger, G; Jones, D; Symietz, I

    2002-01-01

    In medicine metallic implants are widely used as hip replacement protheses or artificial teeth. The biocompatibility is in all cases the most important requirement. Hydroxyapatite (HAp) is frequently used as coating on metallic implants because of its high acceptance by the human body. In this paper a process is described by which a HAp surface layer is produced by ion implantation with a continuous transition to the bulk material. Calcium and phosphorus ions are successively implanted into titanium under different vacuum conditions by backfilling oxygen into the implantation chamber. Afterwards the implanted samples are thermally treated. The elemental composition inside the implanted region was determined by nuclear analysis methods as (alpha,alpha) backscattering and the resonant nuclear reaction sup 1 H( sup 1 sup 5 N,alpha gamma) sup 1 sup 2 C. The results of X-ray photoelectron spectroscopy indicate the formation of HAp. In addition a first biocompatibility test was performed to compare the growing of m...

  11. Elipsometry of surface layers on lead and lithium

    Energy Technology Data Exchange (ETDEWEB)

    Peters, R.D.

    1978-10-01

    An automatic self-compensating ellipsometer was used to study anodic and corrosion films on lead exposed to sulfuric acid and lithium to water. Acid concentrations were 1.3, 3.1 and 5 M. Anodic current densities for lead ranged from 0.01 mA/cm/sup 2/ to 1.3 mA/cm/sup 2/, and mass transport conditions included free convection and forced convection. Scanning electron micrographs of the resulting surfaces were also made. A computer interpretation of ellipsometer measurements assumes the formation of up to six layers and applies a continuous mass balance. Seven to nine parameters describing the mechanism and structure of surface layers are derived by multidimensional fitting of the measurements. A solution mechanism of film formation on lead is indicated by the dependence of film properties on factors that influence the interfacial concentration of reaction products. A colloidal or polymerized phase of PbSO/sub 4/ suspended in the solution is postulated on the basis of observed mass balances and interfacial solution refractive indices. Kinetic parameters describing the corrosion of lead, evaluated from ellipsometer measurements, are consistent with those reported in the literature. The lead electrode was found to be protected from corrosion during an open circuit potential of -.6 V vs Hg/HgSO/sub 4/ (basic sulfate). Cathodic reduction of PbSO/sub 4/ films terminates with the onset of H2 evolution before complete conversion of the sulfate. Changes in kinetic parameters of cathodic electrode reactions which result in preferred H2 evolution are indicated by this observation. The formation of optically absorbing films was observed in the reaction of lithium with water vapor. 44 figures, 16 tables.

  12. New Setup of the UAS ALADINA for Measuring Boundary Layer Properties, Atmospheric Particles and Solar Radiation

    Directory of Open Access Journals (Sweden)

    Konrad Bärfuss

    2018-01-01

    Full Text Available The unmanned research aircraft ALADINA (Application of Light-weight Aircraft for Detecting in situ Aerosols has been established as an important tool for boundary layer research. For simplified integration of additional sensor payload, a flexible and reliable data acquisition system was developed at the Institute of Flight Guidance, Technische Universität (TU Braunschweig. The instrumentation consists of sensors for temperature, humidity, three-dimensional wind vector, position, black carbon, irradiance and atmospheric particles in the diameter range of ultra-fine particles up to the accumulation mode. The modular concept allows for straightforward integration and exchange of sensors. So far, more than 200 measurement flights have been performed with the robustly-engineered system ALADINA at different locations. The obtained datasets are unique in the field of atmospheric boundary layer research. In this study, a new data processing method for deriving parameters with fast resolution and to provide reliable accuracies is presented. Based on tests in the field and in the laboratory, the limitations and verifiability of integrated sensors are discussed.

  13. Wind Turbine Performance in an Atmospheric Boundary Layer: Betz Analysis Revisited

    Science.gov (United States)

    West, Jacob; Lele, Sanjiva

    2017-11-01

    Using large eddy simulation of an infinite (periodic in x and y) wind farm, we compute momentum and mean mechanical energy budgets. We focus on the control volume defined by a streamtube of the mean flow that intersects with a turbine actuator disk, in a similar way as traditional Betz analysis is done for a streamtube in inviscid, irrotational flow through an actuator disk. This analysis reveals that many of the same phenomena from Betz analysis are found in the atmospheric boundary layer case. The streamtube expands as the fluid decelerates through the turbine, and the pressure increases and then drops sharply across the actuator disk. However, away from the turbine, the downstream streamtube shrinks and fluid accelerates due to turbulent mixing. In this way, turbulence alters the idealization of the Betz streamtube. We anticipate that the Betz analysis can be applied most effectively to a wind turbine in the atmospheric boundary layer by focusing on the immediate vicinity around the turbine, where inviscid, potential flow effects dominate. Adjustments can be made to account for the vertical energy flux in wind farms, as well as the energy contained in velocity fluctuations.

  14. Simulation and modeling of the turbulent katabatic flow along a hyperbolic tangent slope for stably stratified atmospheric boundary layer

    Science.gov (United States)

    Brun, Ch.; Chollet, J. P.

    2009-04-01

    The behaviour of the Atmospheric Boundary layer (ABL) along alpine valleys is strongly dependent on the day-night thermodynamic cycle and might impact meteorology and air pollution prediction. At night, the ABL is stably stratified and the radiative cooling of the surface yields the development of a katabatic flow (Doran and Horst 1983, Monti et al. 2002). This flow consists of a downslope wall-jet which has the structure of both wall turbulence in the inner-layer zone and shear layer turbulence in the outer-layer zone and enhances a relative mixing eventhough stable stratification is considered (Baines 2005). A full 3D description of such flow by mean of Large Eddy Simulation of turbulence (LES) has not yet been achieved, except recently on relatively simple slopes (Skyllingstad 2003, Smith and Skyllingstad 2005) or including geostrophic wind forcing (Cuxart et al. 2006, Cuxart and Jimenez 2006). This is the purpose of the present study to accurately describe the ABL on a hyperbolic tangent slope with stable stratification. The numerical code used, Meso-NH, has been developed in CNRM/Meteo-France and Laboratoire d'Aérologie Toulouse, and consists of an anelastic non-hydrostatic model solving the pseudo-incompressible Navier-Stokes equations with a Boussinesq approximation. About 5 million grid points are necessary to afford a relatively precise description of the flow in the vicinity of the surface, with a special refinement in the vertical direction to capture the wall-jet developing along the slope. The setting of initial and boundary conditions is crucial for the simulation of stable ABL. Initial conditions consist of air at rest following a stable temperature profile with a constant Brunt-Väisälä frequency N=0.013. At the surface two sets of boundary conditions have been considered, first a rough surface condition, second an ideal case with slip conditions. A constant surface cooling q_w=-30 W/m2 is applied on the stably stratified fluid initially at rest

  15. The North Atlantic surface layer and the shallow overturning circulation

    Science.gov (United States)

    Busecke, Julius; Gordon, Arnold L.

    2014-05-01

    gradient might be a mechanism for seasonally enhanced mesoscale turbulence, which could be important for the seasonal mixed layer budget as well as interannual variability in surface properties within the SSS-max.

  16. Analysis of atmospheric flow over a surface protrusion using the turbulence kinetic energy equation

    Science.gov (United States)

    Frost, W.; Harper, W. L.; Fichtl, G. H.

    1975-01-01

    Atmospheric flow fields resulting from a semi-elliptical surface obstruction in an otherwise horizontally homogeneous statistically stationary flow are modelled with the boundary-layer/Boussinesq-approximation of the governing equation of fluid mechanics. The turbulence kinetic energy equation is used to determine the dissipative effects of turbulent shear on the mean flow. Mean-flow results are compared with those given in a previous paper where the same problem was attacked using a Prandtl mixing-length hypothesis. Iso-lines of turbulence kinetic energy and turbulence intensity are plotted in the plane of the flow. They highlight regions of high turbulence intensity in the stagnation zone and sharp gradients in intensity along the transition from adverse to favourable pressure gradient.

  17. Micropatterned Surfaces for Atmospheric Water Condensation via Controlled Radical Polymerization and Thin Film Dewetting.

    Science.gov (United States)

    Wong, Ian; Teo, Guo Hui; Neto, Chiara; Thickett, Stuart C

    2015-09-30

    Inspired by an example found in nature, the design of patterned surfaces with chemical and topographical contrast for the collection of water from the atmosphere has been of intense interest in recent years. Herein we report the synthesis of such materials via a combination of macromolecular design and polymer thin film dewetting to yield surfaces consisting of raised hydrophilic bumps on a hydrophobic background. RAFT polymerization was used to synthesize poly(2-hydroxypropyl methacrylate) (PHPMA) of targeted molecular weight and low dispersity; spin-coating of PHPMA onto polystyrene films produced stable polymer bilayers under appropriate conditions. Thermal annealing of these bilayers above the glass transition temperature of the PHPMA layer led to complete dewetting of the top layer and the formation of isolated PHPMA domains atop the PS film. Due to the vastly different rates of water nucleation on the two phases, preferential dropwise nucleation of water occurred on the PHPMA domains, as demonstrated by optical microscopy. The simplicity of the preparation method and ability to target polymers of specific molecular weight demonstrate the value of these materials with respect to large-scale water collection devices or other materials science applications where patterning is required.

  18. Responses of the corroded surface layer of austenitic stainless steel to different corrosive conditions under cavitation

    Energy Technology Data Exchange (ETDEWEB)

    Yong, Xingyue, E-mail: yongxy@mail.buct.edu.cn; Xiao, Ning; Shen, Hanjie; Song, Yili

    2016-08-01

    Nanoindentation was used to measure the nano-mechanical properties of the corroded surface layer of austenitic stainless steel after cavitation corrosion tests. The phase structures and chemical compositions of the corroded surface layer were analysed using X-ray diffraction and X-ray Photoelectron Spectroscopy. The results show that corrosion caused a decrement of the nano-mechanical properties of the corroded surface layer. Once corrosion was weakened, the formation of a work-hardened layer resulted from the transformation of austenite into martensite. The synergistic effect caused the more rapid dissolution of Fe hydroxides, resulting in the enrichment of Cr and property changes of the corroded surface layer under cavitation.

  19. LOLAS: an optical turbulence profiler in the atmospheric boundary layer with extreme altitude resolution

    Science.gov (United States)

    Avila, R.; Avilés, J. L.; Wilson, R. W.; Chun, M.; Butterley, T.; Carrasco, E.

    2008-07-01

    We report the development and first results of an instrument called Low Layer SCIDAR (Scintillation Detection and Ranging) (LOLAS) which is aimed at the measurement of optical-turbulence profiles in the atmospheric boundary layer with high altitude resolution. The method is based on the Generalized SCIDAR (GS) concept, but unlike the GS instruments which need a 1-m or larger telescope, LOLAS is implemented on a dedicated 40-cm telescope, making it an independent instrument. The system is designed for widely separated double-star targets, which enables the high altitude resolution. Using a 200-arcsec-separation double star, we have obtained turbulence profiles with unprecedented 12-m resolution. The system incorporates necessary novel algorithms for autoguiding, autofocus and image stabilization. The results presented here were obtained at Mauna Kea Observatory. They show LOLAS capabilities but cannot be considered as representative of the site. A forthcoming paper will be devoted to the site characterization. The instrument was built as part of the Ground Layer Turbulence Monitoring Campaign on Mauna Kea for Gemini Observatory.

  20. A Surface-to-Environment Synoptic Typing Approach to Classify Cyclone Forcing of Ocean-Sea Ice-Atmosphere Coupling within the Cape Bathurst Flaw Lead

    Science.gov (United States)

    Asplin, M. G.; Barber, D. G.; Candlish, L. M.; Raddatz, R.

    2010-12-01

    The Circumpolar Flaw Lead (CFL) system represents a key dynamic physical and biophysical interface between the atmosphere, ocean, and sea ice in the Arctic Basin. The CFL system is an area of open water and thin ice, and is formed where the mobile central pack ice moves away from coastal fast ice. This process can release large heat and moisture fluxes to the atmosphere throughout the winter and spring, thus modifying the regional boundary layer climate. This process was monitored throughout the eleven-month long International Polar Year Circumpolar Flaw Lead System Study, which involved over-wintering the Canadian Research Icebreaker CCGS Amundsen from September 2007 to August 2008 in the Cape Bathurst Flaw Lead. In this paper, we propose a technique to generate a surface-to-environment synoptic climatology for the Cape Bathurst Flaw Lead region using gridded ice concentration data, and link it to an existing environment-to-surface synoptic climatology based upon sea level pressure to examine dynamic and thermodynamic cyclone forcing of the atmosphere-sea ice interface in the Banks Island flaw lead. The existing environment-to-surface synoptic climatology characterizes atmospheric forcing of sea ice motion well, and it is expected that the surface-to-environment synoptic climatology will be effective at classifying how sea ice concentration forces seasonal boundary layer atmospheric profiles over the Cape Bathurst flaw lead. Cyclone-driven heat and moisture coupling between the ocean and atmosphere within the boundary layer can then be assessed.

  1. Progress in Understanding Land-Surface-Atmosphere Coupling from LBA Research

    Directory of Open Access Journals (Sweden)

    Alan K Betts

    2010-06-01

    Full Text Available LBA research has deepened our understanding of the role of soil water storage, clouds and aerosols in land-atmosphere coupling. We show how the reformulation of cloud forcing in terms of an effective cloud albedo per unit area of surface gives a useful measure of the role of clouds in the surface energy budget over the Amazon. We show that the diurnal temperature range has a quasi-linear relation to the daily mean longwave cooling; and to effective cloud albedo because of the tight coupling between the near-surface climate, the boundary layer and the cloud field. The coupling of surface and atmospheric processes is critical to the seasonal cycle: deep forest rooting systems make water available throughout the year, whereas in the dry season the shortwave cloud forcing is reduced by regional scale subsidence, so that more light is available for photosynthesis. At sites with an annual precipitation above 1900 mm and a dry season length less than 4 months, evaporation rates increased in the dry season, coincident with increased radiation. In contrast, ecosystems with precipitation less than 1700 mm and a longer dry season showed clear evidence of reduced evaporation in the dry season coming from water stress. In all these sites, the seasonal variation of the effective cloud albedo is a major factor in determining the surface available energy. Dry season fires add substantial aerosol to the atmosphere. Aerosol scattering and absorption both reduce the total downward surface radiative flux, but increase the diffuse/direct flux ratio, which increases photosynthetic efficiency. Convective plumes produced by fires enhance the vertical transport of aerosols over the Amazon, and effectively inject smoke aerosol and gases directly into the middle troposphere with substantial impacts on mid- tropospheric dispersion. In the rainy season in Rondônia, convection in low-level westerly flows with low aerosol content resembles oceanic convection with

  2. Rapid exchange between atmospheric CO2 and carbonate anion intercalated within magnesium rich layered double hydroxide.

    Science.gov (United States)

    Sahoo, Pathik; Ishihara, Shinsuke; Yamada, Kazuhiko; Deguchi, Kenzo; Ohki, Shinobu; Tansho, Masataka; Shimizu, Tadashi; Eisaku, Nii; Sasai, Ryo; Labuta, Jan; Ishikawa, Daisuke; Hill, Jonathan P; Ariga, Katsuhiko; Bastakoti, Bishnu Prasad; Yamauchi, Yusuke; Iyi, Nobuo

    2014-10-22

    The carbon cycle, by which carbon atoms circulate between atmosphere, oceans, lithosphere, and the biosphere of Earth, is a current hot research topic. The carbon cycle occurring in the lithosphere (e.g., sedimentary carbonates) is based on weathering and metamorphic events so that its processes are considered to occur on the geological time scale (i.e., over millions of years). In contrast, we have recently reported that carbonate anions intercalated within a hydrotalcite (Mg0.75Al0.25(OH)2(CO3)0.125·yH2O), a class of a layered double hydroxide (LDH), are dynamically exchanging on time scale of hours with atmospheric CO2 under ambient conditions. (Ishihara et al., J. Am. Chem. Soc. 2013, 135, 18040-18043). The use of (13)C-labeling enabled monitoring by infrared spectroscopy of the dynamic exchange between the initially intercalated (13)C-labeled carbonate anions and carbonate anions derived from atmospheric CO2. In this article, we report the significant influence of Mg/Al ratio of LDH on the carbonate anion exchange dynamics. Of three LDHs of various Mg/Al ratios of 2, 3, or 4, magnesium-rich LDH (i.e., Mg/Al ratio = 4) underwent extremely rapid exchange of carbonate anions, and most of the initially intercalated carbonate anions were replaced with carbonate anions derived from atmospheric CO2 within 30 min. Detailed investigations by using infrared spectroscopy, scanning electron microscopy, powder X-ray diffraction, elemental analysis, adsorption, thermogravimetric analysis, and solid-state NMR revealed that magnesium rich LDH has chemical and structural features that promote the exchange of carbonate anions. Our results indicate that the unique interactions between LDH and CO2 can be optimized simply by varying the chemical composition of LDH, implying that LDH is a promising material for CO2 storage and/or separation.

  3. Complementary nature of surface and atmospheric parameters associated with Haiti earthquake of 12 January 2010

    Directory of Open Access Journals (Sweden)

    Ramesh P. Singh

    2010-06-01

    Full Text Available The present paper describes surface (surface air temperature and atmospheric parameters (relative humidity, surface latent heat flux over the epicenter (18°27´25´´ N 72°31´59´´ W of Haiti earthquake of 12 January 2010. Our analysis shows pronounced changes in surface and atmospheric parameters few days prior to the main earthquake event. Changes in relative humidity are found from the surface up to an altitude of 500 hPa clearly show atmospheric perturbations associated with the earthquake event. The purpose of this paper is to show complementary nature of the changes observed in surface, atmospheric and meteorological parameters. The total ozone concentration is found to be lowest on the day of earthquake and afterwards found to be increased within a week of earthquake. The present results show existence of coupling between lithosphere-atmosphere associated with the deadly Haiti earthquake.

  4. Surface Pressure Measurements of Atmospheric Tides Using Smartphones

    Science.gov (United States)

    Price, Colin; Maor, Ron

    2017-04-01

    Similar to the oceans, the atmosphere also has tides that are measured in variations of atmospheric pressure. However, unlike the gravitational tides in the oceans, the atmospheric tides are caused primarily in the troposphere and stratosphere when the atmosphere is periodically heated by the sun, due to tropospheric absorption by water vapor and stratospheric absorption by ozone. Due to the forcing being always on the day side of the globe, the tides migrate around the globe following the sun (migrating tides) with a dominant periodicity of 12 hours (and less so at 24 hours). In recent years smartphones have been equipped with sensitive, cheap and reliable pressure sensors that can easily detect these atmospheric tides. By 2020 it is expected that there will be more than 6 billion smartphones globally, each measuring continuously atmospheric pressure at 1Hz temporal resolution. In this presentation we will present some control experiments we have performed with smartphones to monitor atmospheric tides, while also using random pressure data from more than 50,000 daily users via the WeatherSignal application. We conclude that smartphones are a useful tool for studying atmospheric tides on local and global scales.

  5. Influence of atmospheric and sea surface temperature on the size of hurricane Catarina

    National Research Council Canada - National Science Library

    Radu, Raluca; Toumi, Ralf; Phau, Jared

    2014-01-01

    ...‐resolution numerical simulations of hurricane Catarina in the South Atlantic indicate that the TC size increases proportionally to the surface latent heat flux, when atmospheric and sea surface temperature ( SST ) are increased...

  6. Land Surface Model (LSM 1.0) for Ecological, Hydrological, Atmospheric Studies

    Data.gov (United States)

    National Aeronautics and Space Administration — The NCAR LSM 1.0 is a land surface model developed to examine biogeophysical and biogeochemical land-atmosphere interactions, especially the effects of land surfaces...

  7. A detailed look beneath the surface: Evidence of a surface reconstruction beneath a capping layer

    Science.gov (United States)

    Krull, D.; Tesch, M. F.; Schönbohm, F.; Lühr, T.; Keutner, C.; Berges, U.; Mertins, H.-Ch.; Westphal, C.

    2016-03-01

    Many physical effects are strongly depending on the composition of the interfaces between separating layers. Hence, the knowledge of the interfacial characteristics such as structure, chemical bonds, or magnetic properties of the corresponding materials is essential for an understanding and optimization of these effects. This study reports on a combined magnetic and structural analysis using X-ray photoelectron diffraction (XPD) and transverse magneto-optical Kerr effect (T-MOKE). The information depth of these methods is demonstrated by investigating the uppermost GaAs(001) layer beneath a Fe-film and the interfacial regimes of Fe/GaAs(001) beneath an MgO capping layer. Iron was prepared on a clean GaAs(001) surface and a GaAs(001)-(4 × 2)-reconstructed surface. Beneath the Fe-film, the (4 × 2)-reconstruction is not lifted, which is clearly shown by the diffraction pattern of the GaAs(4 × 2)-Fe surface. It is shown that Fe inter-diffusion, resulting in an amorphous interface, is almost prevented by the Ga-rich reconstruction. The magneto-optical measurements with T-MOKE clearly demonstrated the Fe-interlayer in a ferromagnetic state. We find no evidence for magnetic properties neither within the signal of the GaAs-substrate nor the MgO-film.

  8. Land surface and atmospheric conditions associated with heat waves in the South Central United States

    Science.gov (United States)

    Lee, Eungul; Bieda, Rahama; Shanmugasundaram, Jothiganesh; Richter, Heather

    2017-04-01

    Exposure to extreme heat was reconstructed based on regional land-atmosphere processes from 1979 to 2010 in the South Central U.S. The study region surrounds the Chickasaw Nation (CN), a predominantly Native American population with a highly prevalent burden of climate-sensitive chronic diseases. Land surface and atmospheric conditions for summer heat waves were analyzed during spring (March-April-May, MAM) and summer (June-July-August, JJA) based on the Climate and Ocean: Variability, Predictability, and Change maximum temperature definition for heat wave frequency (HWF). The spatial-temporal pattern of HWF was determined using empirical orthogonal function (EOF) analysis and the corresponding principle component time series of the first EOF of HWF. Statistically significant analyses of observed conditions indicated that sensible heat increased and latent heat fluxes decreased with high HWF in the South Central U.S. The largest positive correlations of sensible heat flux to HWF and the largest negative correlations of latent heat flux to HWF were specifically observed over the CN. This is a significantly different energy transfer regime due to less available soil moisture during the antecedent MAM and JJA. The higher sensible heat from dry soil could cause significant warming from the near surface (> 2.0°C) to the lower troposphere (> 1.5°C), and accumulated boundary layer heat could induce the significant patterns of higher geopotential height and enhance anticyclonic circulations (negative vorticity anomaly) at the midtroposphere. Results suggested a positive land-atmosphere feedback associated with heat waves and called attention to the need for region-specific climate adaptation planning.

  9. Dry Deposition, Surface Production and Dynamics of Aerosols in the Marine Boundary Layer

    DEFF Research Database (Denmark)

    Fairall, C.W.; Larsen, Søren Ejling

    1984-01-01

    A model of downward aerosol panicle flux characterized by dry deposition velocity, Vd, due to Slinn and Slinn (1980) is generalized to the case of nonzero surface concentration (absorbing surface with a surface source). A more general expression for the flux at some reference height is developed...... which includes Vd and an effective surface source strength, Si, which is a function of the true surface source strength, Si, and the particle transport properties below the reference height. The general expression for the surface flux is incorporated into a dynamic mixed layer model of the type...... developed by Davidson et al. (1983). This three layer model (diffusion sublayer, turbulent surface layer and mixed layer) is applied to an open ocean marine regime where boundary layer advection is ignored. The aerosol concentration in the boundary layer is considered to consist of sea salt particles...

  10. On the influence of atmospheric super-saturation layer on China's heavy haze-fog events

    Science.gov (United States)

    Wang, Jizhi; Yang, Yuanqin; Zhang, Xiaoye; Liu, Hua; Che, Huizheng; Shen, Xiaojing; Wang, Yaqiang

    2017-12-01

    With the background of global change, the air quality in Earth's atmosphere has significantly decreased. The North China Plain (NCP), Yangtze River Delta (YRD), Pearl River Delta (PRD) and Si-Chuan Basin (SCB) are the major areas suffering the decreasing air quality and frequent pollution events in recent years. Studying the effect of meteorological conditions on the concentration of pollution aerosols in these pollution sensitive regions is a hot focus now. This paper analyses the characteristics of atmospheric super-saturation and the corresponding H_PMLs (height of supersaturated pollution mixing layer), investigating their contribution to the frequently-seen heavy haze-fog weather. The results suggest that: (1) in the above-mentioned pollution sensitive regions in China, super-saturated layers repeatedly appear in the low altitude and the peak value of supersaturation S can reach 6-10%, which makes pollution particles into the wet adiabatic uplift process in the stable-static atmosphere. After low-level atmosphere reaches the super-saturation state below the H_PMLs, meteorological condition contributes to humidification and condensation of pollution particles. (2) Caculation of condensation function Fc, one of PLAM sensetive parameter, indicates that super-saturation state helps promote condensation, beneficial to the formation of Condensational Kink (CK) in the pollution sensitive areas. This favors the formation of new aerosol particles and intensities the cumulative growth of aerosol concentration. (3) By calculating the convective inhibition energy on average │CIN│ > 1.0 × 104 J kg-1, we found the value is about 100 times higher than the stable critical value. The uplifting diffusion of the particles is inhibited by the ambient airflow. So, this is the important reason for the aggravation and persistence of aerosol pollutants in local areas. (4) H_PMLs is negatively correlated to the pollution meteorological condition index PLAM which can describe the

  11. New Material Development for Surface Layer and Surface Technology in Tribology Science to Improve Energy Efficiency

    Science.gov (United States)

    Ismail, R.; Tauviqirrahman, M.; Jamari, Jamari; Schipper, D. J.

    2009-09-01

    This paper reviews the development of new material and surface technology in tribology and its contribution to energy efficiency. Two examples of the economic benefits, resulted from the optimum tribology in the transportation sector and the manufacturing industry are discussed. The new materials are proposed to modify the surface property by laminating the bulk material with thin layer/coating. Under a suitable condition, the thin layer on a surface can provide a combination of good wear, a low friction and corrosion resistance for the mechanical components. The innovation in layer technology results molybdenum disulfide (MoS2), diamond like carbon (DLC), cubic boron nitride (CBN) and diamond which perform satisfactory outcome. The application of the metallic coatings to carbon fibre reinforced polymer matrix composites (CFRP) has the capacity to provide considerable weight and power savings for many engineering components. The green material for lubricant and additives such as the use of sunflower oil which possesses good oxidation resistance and the use of mallee leaves as bio-degradable solvent are used to answer the demand of the environmentally friendly material with good performance. The tribology research implementation for energy efficiency also touches the simple things around us such as: erasing the laser-print in a paper with different abrasion techniques. For the technology in the engineering surface, the consideration for generating the suitable surface of the components in running-in period has been discussed in order to prolong the components life and reduce the machine downtime. The conclusion, tribology can result in reducing manufacturing time, reducing the maintenance requirements, prolonging the service interval, improving durability, reliability and mechanical components life, and reducing harmful exhaust emission and waste. All of these advantages will increase the energy efficiency and the economic benefits.

  12. New Material Development for Surface Layer and Surface Technology in Tribology Science to Improve Energy Efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Ismail, R., E-mail: rifky-mec@yahoo.com; Tauviqirrahman, M., E-mail: rifky-mec@yahoo.com [Laboratory for Engineering Design and Tribology, Department of Mechanical Engineering, University of Diponegoro, Semarang, Indonesia and Jl. Prof. Sudharto, Kampus UNDIP Tembalang, Semarang (Indonesia); Laboratory for Surface Technology and Tribology, Faculty of Engineering Technology, University of Twente, Enschede (Netherlands); Jamari, E-mail: rifky-mec@yahoo.com [Laboratory for Engineering Design and Tribology, Department of Mechanical Engineering, University of Diponegoro, Semarang, Indonesia and Jl. Prof. Sudharto, Kampus UNDIP Tembalang, Semarang (Indonesia); Schipper, D. J., E-mail: rifky-mec@yahoo.com [Laboratory for Surface Technology and Tribology, Faculty of Engineering Technology, University of Twente, Enschede (Netherlands)

    2009-09-14

    This paper reviews the development of new material and surface technology in tribology and its contribution to energy efficiency. Two examples of the economic benefits, resulted from the optimum tribology in the transportation sector and the manufacturing industry are discussed. The new materials are proposed to modify the surface property by laminating the bulk material with thin layer/coating. Under a suitable condition, the thin layer on a surface can provide a combination of good wear, a low friction and corrosion resistance for the mechanical components. The innovation in layer technology results molybdenum disulfide (MoS2), diamond like carbon (DLC), cubic boron nitride (CBN) and diamond which perform satisfactory outcome. The application of the metallic coatings to carbon fibre reinforced polymer matrix composites (CFRP) has the capacity to provide considerable weight and power savings for many engineering components. The green material for lubricant and additives such as the use of sunflower oil which possesses good oxidation resistance and the use of mallee leaves as bio‐degradable solvent are used to answer the demand of the environmentally friendly material with good performance. The tribology research implementation for energy efficiency also touches the simple things around us such as: erasing the laser‐print in a paper with different abrasion techniques. For the technology in the engineering surface, the consideration for generating the suitable surface of the components in running‐in period has been discussed in order to prolong the components life and reduce the machine downtime. The conclusion, tribology can result in reducing manufacturing time, reducing the maintenance requirements, prolonging the service interval, improving durability, reliability and mechanical components life, and reducing harmful exhaust emission and waste. All of these advantages will increase the energy efficiency and the economic benefits.

  13. 78 FR 70076 - Aging Management of Internal Surfaces, Fire Water Systems, Atmospheric Storage Tanks, and...

    Science.gov (United States)

    2013-11-22

    ... COMMISSION Aging Management of Internal Surfaces, Fire Water Systems, Atmospheric Storage Tanks, and... Guidance (LR-ISG), LR-ISG-2012-02, ``Aging Management of Internal Surfaces, Fire Water Systems, Atmospheric... aging management programs (AMPs), aging management review (AMR) items, and definitions in NUREG- 1801...

  14. Surface Composition of Mars: Results from a New Atmospheric Compensation Technique Applied to TES

    Science.gov (United States)

    Kirkland, L. E.; Herr, K. C.; Ward, J.; Keim, E. R.; Hackwell, J. H.; McAfee, J. M.

    2002-01-01

    Before TES (Thermal Emission Spectrometry) spectra can be used to model surface compositions, they must have a strong atmospheric compensation applied. We explore a very different atmospheric retrieval process, and compare results and implications for the derived surface composition. Additional information is contained in the original extended abstract.

  15. Oxidation of the Martian surface - Constraints due to chemical processes in the atmosphere

    Science.gov (United States)

    Mcelroy, M. B.; Kong, T. Y.

    1976-01-01

    Dissociation of water in the Martian atmosphere may supply oxygen to the surface and may result in the formation of minerals such as goethite, as proposed by Huguenin. The supply rate is limited by chemical processes in the atmosphere which regulate the abundance of O2. The net surface sink for atmospheric oxygen can be as large as 33 million atoms per sq cm per sec which compares to the escape rate of 60 million atoms per sq cm per sec.

  16. Leaf Area Influence on Surface Layer in a Deciduous Forest. Part I; Site Description

    Science.gov (United States)

    Sakai, Ricardo K.; Fitzjarrald, David R.; Moore, Kathleen E.; Sicker, John W.; Munger, William; Goulden, Michael L.; Wofsy, Steven C.

    1996-01-01

    A study over a deciduous forest located in middle Massachusetts (USA) has been performed to examine the role of leaves in the forest-atmosphere interaction. Due to the seasonal presence of leaves, a deciduous forest is a 'good laboratory' to study this interaction. In this first part, a description of a 30 m micrometeorological tower as well a qualitative description of some meteorological parameters are presented. The presence of leaves affects the forest in several ways. There is a decrease of upward PAR (Photosynthetically Active Radiation) due to absorption of visible light in the canopy. Water vapor concentration increases, and the CO2 concentration decreases in the surface layer as the canopy starts to be foliated. The physical presence of the leaves is felt in other quantities such as the global albedo and the subcanopy environment.

  17. Surface modification of polylactic acid films by atmospheric pressure plasma treatment

    Science.gov (United States)

    Kudryavtseva, V. L.; Zhuravlev, M. V.; Tverdokhlebov, S. I.

    2017-09-01

    A new approach for the modification of polylactic acid (PLA) materials using atmospheric pressure plasma (APP) is described. PLA films plasma exposure time was 20, 60, 120 s. The surface morphology and wettability of the obtained PLA films were investigated by atomic force microscopy (AFM) and the sitting drop method. The atmospheric pressure plasma increased the roughness and surface energy of PLA film. The wettability of PLA has been improved with the application of an atmospheric plasma surface treatment. It was shown that it is possible to obtain PLA films with various surface relief and tunable wettability. Additionally, we demonstrated that the use of cold atmospheric pressure plasma for surface activation allows for the immobilization of bioactive compounds like hyaluronic acid (HA) on the surface of obtained films. It was shown that composite PLA-HA films have an increased long-term hydrophilicity of the films surface.

  18. Climate change and atmospheric chemistry: how will the stratospheric ozone layer develop?

    Science.gov (United States)

    Dameris, Martin

    2010-10-25

    The discovery of the ozone hole over Antarctica in 1985 was a surprise for science. For a few years the reasons of the ozone hole was speculated about. Soon it was obvious that predominant meteorological conditions led to a specific situation developing in this part of the atmosphere: Very low temperatures initiate chemical processes that at the end cause extreme ozone depletion at altitudes of between about 15 and 30 km. So-called polar stratospheric clouds play a key role. Such clouds develop at temperatures below about 195 K. Heterogeneous chemical reactions on cloud particles initiate the destruction of ozone molecules. The future evolution of the ozone layer will not only depend on the further development of concentrations of ozone-depleting substances, but also significantly on climate change.

  19. Spatial atmospheric atomic layer deposition of InxGayZnzO for thin film transistors.

    Science.gov (United States)

    Illiberi, A; Cobb, B; Sharma, A; Grehl, T; Brongersma, H; Roozeboom, F; Gelinck, G; Poodt, P

    2015-02-18

    We have investigated the nucleation and growth of InGaZnO thin films by spatial atmospheric atomic layer deposition. Diethyl zinc (DEZ), trimethyl indium (TMIn), triethyl gallium (TEGa), and water were used as Zn, In, Ga and oxygen precursors, respectively. The vaporized metal precursors have been coinjected in the reactor. The metal composition of InGaZnO has been controlled by varying the TMIn or TEGa flow to the reactor, for a given DEZ flow and exposure time. The morphology of the films changes from polycrystalline, for ZnO and In-doped ZnO, to amorphous for In-rich IZO and InGaZnO. The use of these films as the active channel in TFTs has been demonstrated and the influence of In and Ga cations on the electrical characteristics of the TFTs has been studied.

  20. Acid-base chemical reaction model for nucleation rates in the polluted atmospheric boundary layer.

    Science.gov (United States)

    Chen, Modi; Titcombe, Mari; Jiang, Jingkun; Jen, Coty; Kuang, Chongai; Fischer, Marc L; Eisele, Fred L; Siepmann, J Ilja; Hanson, David R; Zhao, Jun; McMurry, Peter H

    2012-11-13

    Climate models show that particles formed by nucleation can affect cloud cover and, therefore, the earth's radiation budget. Measurements worldwide show that nucleation rates in the atmospheric boundary layer are positively correlated with concentrations of sulfuric acid vapor. However, current nucleation theories do not correctly predict either the observed nucleation rates or their functional dependence on sulfuric acid concentrations. This paper develops an alternative approach for modeling nucleation rates, based on a sequence of acid-base reactions. The model uses empirical estimates of sulfuric acid evaporation rates obtained from new measurements of neutral molecular clusters. The model predicts that nucleation rates equal the sulfuric acid vapor collision rate times a prefactor that is less than unity and that depends on the concentrations of basic gaseous compounds and preexisting particles. Predicted nucleation rates and their dependence on sulfuric acid vapor concentrations are in reasonable agreement with measurements from Mexico City and Atlanta.

  1. The warmer the ocean surface, the shallower the mixed layer. How much of this is true?

    Science.gov (United States)

    Somavilla, R.; González-Pola, C.; Fernández-Diaz, J.

    2017-09-01

    Ocean surface warming is commonly associated with a more stratified, less productive, and less oxygenated ocean. Such an assertion is mainly based on consistent projections of increased near-surface stratification and shallower mixed layers under global warming scenarios. However, while the observed sea surface temperature (SST) is rising at midlatitudes, the concurrent ocean record shows that stratification is not unequivocally increasing nor is MLD shoaling. We find that while SST increases at three study areas at midlatitudes, stratification both increases and decreases, and MLD deepens with enhanced deepening of winter MLDs at rates over 10 m decade-1. These results rely on the estimation of several MLD and stratification indexes of different complexity on hydrographic profiles from long-term hydrographic time-series, ocean reanalysis, and Argo floats. Combining this information with estimated MLDs from buoyancy fluxes and the enhanced deepening/attenuation of the winter MLD trends due to changes in the Ekman pumping, MLD variability involves a subtle interplay between circulation and atmospheric forcing at midlatitudes. Besides, it is highlighted that the density difference between the surface and 200 m, the most widely used stratification index, should not be expected to reliably inform about changes in the vertical extent of mixing.

  2. Investigation of chemical properties and transport phenomena associated with pollutants in the atmospheric boundary layer

    Science.gov (United States)

    Holmes, Heather A.

    Under the Clean Air Act, the U.S. Environmental Protection Agency is required to determine which air pollutants are harmful to human health, then regulate, monitor and establish criteria levels for these pollutants. To accomplish this and for scientific advancement, integration of knowledge from several disciplines is required including: engineering, atmospheric science, chemistry and public health. Recently, a shift has been made to establish interdisciplinary research groups to better understand the atmospheric processes that govern the transport of pollutants and chemical reactions of species in the atmospheric boundary layer (ABL). The primary reason for interdisciplinary collaboration is the need for atmospheric processes to be treated as a coupled system, and to design experiments that measure meteorological, chemical and physical variables simultaneously so forecasting models can be improved (i.e., meteorological and chemical process models). This dissertation focuses on integrating research disciplines to provide a more complete framework to study pollutants in the ABL. For example, chemical characterization of particulate matter (PM) and the physical processes governing PM distribution and mixing are combined to provide more comprehensive data for source apportionment. Data from three field experiments were utilized to study turbulence, meteorological and chemical parameters in the ABL. Two air quality field studies were conducted on the U.S./Mexico border. The first was located in Yuma, AZ to investigate the spatial and temporal variability of PM in an urban environment and relate chemical properties of ambient aerosols to physical findings. The second border air quality study was conducted in Nogales, Sonora, Mexico to investigate the relationship between indoor and outdoor air quality in order to better correlate cooking fuel types and home activities to elevated indoor PM concentrations. The final study was executed in southern Idaho and focused on

  3. Gas Hydrates of Coal Layers as a Methane Source in the Atmosphere and Mine Working

    Directory of Open Access Journals (Sweden)

    Dyrdin Valery

    2017-01-01

    Full Text Available Living conditions of gas hydrates of a methane in a coal matrix as one of possible forms of finding of molecules of a methane in coal layers are considered. However, gas hydrates are formed not in all mineral coals even under the thermobaric conditions corresponding to their equilibrium state as the minimum humidity and the corresponding pore width are necessary for each brand of coal for formation of gas hydrate. It is shown that it depends on electric electrical dipole moment of a macromolecule of coal. Coals of brands K, D, Zh were considered. The electric field created by the surface of coal does not allow molecules of water to carry out threedimensional driving, and they keep on an internal surface of a time. By means of theoretical model operation a dipole - dipole interaction of molecules of water with the steam surface of coal values of energy of fiber interaction for various functional groups located in coal “fringe” which size for the first and second layers does not allow molecules of water to participate in formation of gas hydrates are received. For coals of brands K, Zh, D, considering distribution of a time on radiuses, the percent of moisture, which cannot share in education solid coal of gas solutions, is calculated.

  4. Gas Hydrates of Coal Layers as a Methane Source in the Atmosphere and Mine Working

    Science.gov (United States)

    Dyrdin, Valery; Shepeleva, Sofya; Kim, Tatiana

    2017-11-01

    Living conditions of gas hydrates of a methane in a coal matrix as one of possible forms of finding of molecules of a methane in coal layers are considered. However, gas hydrates are formed not in all mineral coals even under the thermobaric conditions corresponding to their equilibrium state as the minimum humidity and the corresponding pore width are necessary for each brand of coal for formation of gas hydrate. It is shown that it depends on electric electrical dipole moment of a macromolecule of coal. Coals of brands K, D, Zh were considered. The electric field created by the surface of coal does not allow molecules of water to carry out threedimensional driving, and they keep on an internal surface of a time. By means of theoretical model operation a dipole - dipole interaction of molecules of water with the steam surface of coal values of energy of fiber interaction for various functional groups located in coal "fringe" which size for the first and second layers does not allow molecules of water to participate in formation of gas hydrates are received. For coals of brands K, Zh, D, considering distribution of a time on radiuses, the percent of moisture, which cannot share in education solid coal of gas solutions, is calculated.

  5. Acoustic pulse propagation through a fluctuating stably stratified atmospheric boundary layer

    Science.gov (United States)

    Chunchuzov, Igor; Kulichkov, Sergey; Otrezov, Alexander; Perepelkin, Vitaly

    2005-04-01

    Mesoscale wind speed and temperature fluctuations with periods from 1 min to a few hours significantly affect temporal variability and turbulent regime of the stable atmospheric boundary layer (ABL). Their statistical characteristics are still poorly understood, although the knowledge of such statistics is required when modeling sound propagation through the stable ABL. Several field experiments have been conducted to study the influence of mesoscale wind speed fluctuations on acoustic pulse propagation through the stable ABL. Some results of these experiments are described in this paper. A special acoustic source was used to generate acoustic pulses by the detonation of an air-propane mixture with a repetition period 30 s. The mean wind speed and temperature profiles were continuously measured by Doppler sodar and temperature profiler, whereas mesoscale wind fluctuations were measured by anemometers placed on a 56-m mast. From the measurements of the pulse travel time fluctuations at different distances from the source, the statistical characteristics of the mesoscale wind fluctuations, such as frequency spectra, coherences, horizontal phase speeds and scales, have been obtained. Some of the obtained results are interpreted with the use of a recently developed model for the internal wave spectrum in a stably stratified atmosphere. .

  6. Acoustic pulse propagation through stable atmospheric boundary layer: Theory and experiment

    Science.gov (United States)

    Chunchuzov, Igor; Kulichkov, Sergey; Otrezov, Alexander; Perepelkin, Vitaly

    2004-05-01

    Mesoscale wind speed and temperature fluctuations with periods from 1 min to a few hours significantly affect a variability and turbulent regime of stable atmospheric boundary layer (ABL). Their statistical characteristics are still poorly understood, although the knowledge of such statistics is required when modeling sound propagation through stable ABL. Several field experiments have been conducted to study the influence of mesoscale wind speed fluctuations on acoustic pulse propagation in stable ABL. The results of these experiments are presented in this work. A special acoustic source was used to generate acoustic pulses due to a detonation of air-propane mixture with a repetition period of 1 min or 30 s. The mean wind speed profiles and mesoscale wind fluctuations were measured by Doppler sodar up to a height of 300 m, and by anemometers placed on a 56-mast. From the measurements of the pulse travel time fluctuations at different distances from the source the statistical characteristics of the mesoscale wind fluctuations such as frequency spectra, coherences, horizontal phase speeds and scales have been obtained. Some of the obtained results are interpreted with a recently developed model of internal wave spectrum in a stably stratified atmosphere.

  7. Stability and turbulence in the atmospheric boundary layer: A comparison of remote sensing and tower observations

    Science.gov (United States)

    Friedrich, Katja; Lundquist, Julie K.; Aitken, Matthew; Kalina, Evan A.; Marshall, Robert F.

    2012-02-01

    When monitoring winds and atmospheric stability for wind energy applications, remote sensing instruments present some advantages to in-situ instrumentation such as larger vertical extent, in some cases easy installation and maintenance, measurements of vertical humidity profiles throughout the boundary layer, and no restrictions on prevailing wind directions. In this study, we compare remote sensing devices, Windcube lidar and microwave radiometer, to meteorological in-situ tower measurements to demonstrate the accuracy of these measurements and to assess the utility of the remote sensing instruments in overcoming tower limitations. We compare temperature and wind observations, as well as calculations of Brunt-Väisälä frequency and Richardson numbers for the instrument deployment period in May-June 2011 at the U.S. Department of Energy National Renewable Energy Laboratory's National Wind Technology Center near Boulder, Colorado. The study reveals that a lidar and radiometer measure wind and temperature with the same accuracy as tower instruments, while also providing advantages for monitoring stability and turbulence. We demonstrate that the atmospheric stability is determined more accurately when the liquid-water mixing ratio derived from the vertical humidity profile is considered under moist-adiabatic conditions.

  8. Untangling the Chemical Evolution of Titan's Atmosphere and Surface -- From Homogeneous to Heterogeneous Chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Kaiser, Ralf I.; Maksyutenko, Pavlo; Ennis, Courtney; Zhang, Fangtong; Gu, Xibin; Krishtal, Sergey P.; Mebel, Alexander M.; Kostko, Oleg; Ahmed, Musahid

    2010-03-16

    The arrival of the Cassini-Huygens probe at Saturn's moon Titan - the only Solar System body besides Earth and Venus with a solid surface and a thick atmosphere with a pressure of 1.4 atm at surface level - in 2004 opened up a new chapter in the history of Solar System exploration. The mission revealed Titan as a world with striking Earth-like landscapes involving hydrocarbon lakes and seas as well as sand dunes and lava-like features interspersed with craters and icy mountains of hitherto unknown chemical composition. The discovery of a dynamic atmosphere and active weather system illustrates further the similarities between Titan and Earth. The aerosol-based haze layers, which give Titan its orange-brownish color, are not only Titan's most prominent optically visible features, but also play a crucial role in determining Titan's thermal structure and chemistry. These smog-like haze layers are thought to be very similar to those that were present in Earth's atmosphere before life developed more than 3.8 billion years ago, absorbing the destructive ultraviolet radiation from the Sun, thus acting as 'prebiotic ozone' to preserve astrobiologically important molecules on Titan. Compared to Earth, Titan's low surface temperature of 94 K and the absence of liquid water preclude the evolution of biological chemistry as we know it. Exactly because of these low temperatures, Titan provides us with a unique prebiotic 'atmospheric laboratory' yielding vital clues - at the frozen stage - on the likely chemical composition of the atmosphere of the primitive Earth. However, the underlying chemical processes, which initiate the haze formation from simple molecules, have been not understood well to date.

  9. The Influence of High Aerosol Concentration on Atmospheric Boundary Layer Temperature Stratification

    Energy Technology Data Exchange (ETDEWEB)

    Khaykin, M.N.; Kadygrove, E.N.; Golitsyn, G.S.

    2005-03-18

    Investigations of the changing in the atmospheric boundary layer (ABL) radiation balance as cased by natural and anthropogenic reasons is an important topic of the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) program. The influence of aerosol on temperature stratification of ABL while its concentration was extremely high within a long period of time was studied experimentally. The case was observed in Moscow region (Russia) with the transport of combustion products from peat-bog and forest fires in July-September, 2002. At this time the visibility was some times at about 100-300 m. Aerosol concentration measured by Moscow University Observatory and A.M. Obukhov Institute of Atmospheric Physics field station in Zvenigorod (55.7 N; 36.6 E) for several days was in 50-100 times more than background one (Gorchakov at al 2003). The high aerosol concentration can change the radiation balance at ABL, and so to change thermal stratification in ABL above the mega lopolis. For the analysis the data were used of synchronous measurements by MTP-5 (Microwave Temperature Profiler operating at wavelength 5 mm) in two locations, namely: downtown Moscow and country-side which is 50 km apart to the West (Zvenigorod station). (Kadygrov and Pick 1998; Westwater at al 1999; Kadygrov at al 2002). Zvenigorod station is located in strongly continental climate zone which is in between of the climates of ARM sites (NSANorth Slope of Alaska and SGP-Southern Great Plains). The town of Zvenigorod has little industry, small traffic volume and topography conductive to a good air ventilation of the town. For these reasons Zvenigorod can be considered as an undisturbed rural site. For the analysis some days were chosen with close meteorological parameters (average temperature, humidity, wind, pressure and cloud form) but strongly differing in aerosol concentration level.

  10. Influence of Evaporating Droplets in the Turbulent Marine Atmospheric Boundary Layer

    Science.gov (United States)

    Peng, Tianze; Richter, David

    2017-08-01

    Sea-spray droplets ejected into the marine atmospheric boundary layer take part in a series of complex transport processes. By capturing the air-droplet coupling and feedback, we focus on how droplets modify the total heat transfer across a turbulent boundary layer. We implement a high-resolution Eulerian-Lagrangian algorithm with varied droplet size and mass loading in a turbulent open-channel flow, revealing that the influence from evaporating droplets varies for different dynamic and thermodynamic characteristics of droplets. Droplets that both respond rapidly to the ambient environment and have long suspension times are able to modify the latent and sensible heat fluxes individually, however the competing signs of this modification lead to an overall weak effect on the total heat flux. On the other hand, droplets with a slower thermodynamic response to the environment are less subjected to this compensating effect. This indicates a potential to enhance the total heat flux, but the enhancement is highly dependent on the concentration and suspension time.

  11. Atmospheric Feedback of Urban Boundary Layer with Implications for Climate Adaptation.

    Science.gov (United States)

    Liang, Marissa S; Keener, Timothy C

    2015-09-01

    Atmospheric structure changes in response to the urban form, land use, and the type of land cover (LULC). This interaction controls thermal and air pollutant transport and distribution. The interrelationships among LULC, ambient temperature, and air quality were analyzed and found to be significant in a case study in Cincinnati, Ohio, U.S.A. Within the urban canopy layer (UCL), traffic-origin PM2.5 and black carbon followed Gaussian dispersion in the near road area in the daytime, while higher concentrations, over 1 order of magnitude, were correlated to the lapse rate under nocturnal inversions. In the overlying urban boundary layer (UBL), ambient temperature and PM2.5 variations were correlated among urban-wide locations indicating effective thermal and mass communications. Beyond the spatial correlation, LULC-related local urban heat island effects are noteworthy. The high-density urbanized zone along a narrow highway-following corridor is marked by higher nighttime temperature by ∼1.6 °C with a long-term increase by 2.0 °C/decade, and by a higher PM2.5 concentration, than in the low-density residential LULC. These results indicate that the urban LULC may have contributed to the nocturnal thermal inversion affecting urban air circulation and air quality in UCL and UBL. Such relationships point to the potentials of climate adaptation through urban planning.

  12. Analytical Reduced Models for the Non-stationary Diabatic Atmospheric Boundary Layer

    Science.gov (United States)

    Momen, Mostafa; Bou-Zeid, Elie

    2017-09-01

    Geophysical boundary-layer flows feature complex dynamics that often evolve with time; however, most current knowledge centres on the steady-state problem. In these atmospheric and oceanic boundary layers, the pressure gradient, buoyancy, Coriolis, and frictional forces interact to determine the statistical moments of the flow. The resulting equations for the non-stationary mean variables, even when succinctly closed, remain challenging to handle mathematically. Here, we derive a simpler physical model that reduces these governing unsteady Reynolds-averaged Navier-Stokes partial differential equations into a single first-order ordinary differential equation with non-constant coefficients. The reduced model is straightforward to solve under arbitrary forcing, even when the statistical moments are non-stationary and the viscosity varies in time and space. The model is successfully validated against large-eddy simulation for, (1) time-variable pressure gradients, and (2) linearly time-variable buoyancy. The new model is shown to have a superior performance compared to the classic Blackadar solutions (and later improvements on these solutions), and it covers a much wider range of conditions.

  13. Mars Thermal History: Core, Atmosphere, Mantle, Phobos and Surface (MaTH CAMPS)

    Science.gov (United States)

    Wicks, J. K.; Weller, M. B.; Towles, N. J.; Thissen, C.; Knezek, N. R.; Johnston, S.; Hongsresawat, S.; Duncan, M. S.; Black, B. A.; Schmerr, N. C.; Panning, M. P.; Montesi, L.; Manga, M.; Lognonne, P. H.

    2014-12-01

    The death of the Martian dynamo ~4.1 Ga and sustained volcanism throughout Martian history place fundamental constraints on the thermal history of the planet. To explore the implications for mantle structure, we constructed holistic models of Mars that include the core, mantle, lithosphere/surface, atmosphere, and an atmospheric capture of Phobos in a collaborative effort begun at the CIDER 2014 summer program. For our thermal model of the core, we employ an iterative solver and parameterized phase diagram to compute pressure, density, and temperature in the core for a variety of initial accretion temperatures and bulk compositions. We use this model to constrain core-mantle boundary (CMB) temperature and heat flow. We couple this model for the evolution of the core with a one-dimensional parameterized convection model for the mantle. The upper boundary condition is set by the state of the Martian atmosphere. We consider the effect of a distinct compositional layer at the base of the mantle that may represent dense magma ocean crystallization products or a primitive layer untouched by magma ocean processes. We find successful models that allow sufficient CMB heat flow to power an early dynamo and the potential of melt generation through extended periods of Mars' history. In addition to dynamo and magmatism timing, other diagnostics allow us to compare model outputs to modern observables. The mass, moment of inertia, and tidal Love number of our model planet are compared directly to measured values. Additionally, deformation and stress on the lithosphere due to internal volume changes and changes in surface loading predicted by our thermal evolution models could be recorded in the Martian crust. Finally, coupling temperature-dependent tidal dissipation affects Phobos' orbital secular evolution and gives constraint on mantle temperatures. These constraints are discussed for the different scenarios of Phobos capture. We present a suite of models that satisfy the

  14. Atmospheric boundary layer characteristics over the Pearl River Delta, China during summer 2006: measurement and model results

    Science.gov (United States)

    Fan, S. J.; Fan, Q.; Yu, W.; Luo, X. Y.; Wang, B. M.; Song, L. L.; Leong, K. L.

    2011-02-01

    Atmospheric conditions are often connected with the occurrence of high pollution episodes especially in urban areas. As part of the PRIDE-PRD2006 intensive campaign, atmospheric boundary layer (ABL) measurements were carried out at Qingyuan, Panyu and Xinken in the Pearl River Delta (PRD) from 1 July to 30 July of 2006. It was found that in summer, the surface winds in PRD are more controlled by the south, and there usually is vertical wind shear at the height of 800 m or so, therefore, PRD is often influenced by the tropical cyclone/typhoon. The subsidence and precipitation from a tropical cyclone will affect the air quality of PRD. Under the subsidence, the wind speed in ABL and the height of ABL will decrease and result in high level concentrations. When the background wind speed is small or calm, the wind profile at Panyu and Xinken change dramatically with height, which is perhaps caused by the local circulations, such as the sea land breeze. For more understanding about the ABL of PRD, the simulations by the WRF mesoscale model were used to analyse the ABL characteristics in PRD. From three kinds of weather condition simulations (subsidence days, rainy days and sunny days) by WRF model, it was found that the simulated temperature, wind fields in these three cases were moderately consistent with the measurements. The results show that the diurnal variation of ABL in subsidence days and sunny days are obvious, but the diurnal variation of ABL on rainy days is not obvious. The ABL is obviously affected by the local circulation and the features of ABL are different in various stations. A simulation focus on high pollution episode during the subsidence days from 12-15 July 2006, occurred under high pressure conditions, accompanied by a tropical cyclone "Bilis". Comparing the simulated vertical wind fields and temperature structure with the ABL measurements at Xinken, Panyu and Qingyuan station, it was found that, the modelled and measured atmospheric fields reveal

  15. Sum-Frequency Generation Spectroscopy for Studying Organic Layers at Water-Air Interfaces: Microlayer Monitoring and Surface Reactivity

    Science.gov (United States)

    Laß, Kristian; Kleber, Joscha; Bange, Hermann; Friedrichs, Gernot

    2015-04-01

    The sea surface microlayer, according to commonly accepted terminology, comprises the topmost millimetre of the oceanic water column. It is often enriched with organic matter and is directly influenced by sunlight exposure and gas exchange with the atmosphere, hence making it a place for active biochemistry and photochemistry as well as for heterogeneous reactions. In addition, surface active material either is formed or accumulates directly at the air-water interface and gives rise to very thin layers, sometimes down to monomolecular thickness. This "sea surface nanolayer" determines the viscoelastic properties of the seawater surface and thus may impact the turbulent air-sea gas exchange rates. To this effect, this small scale layer presumably plays an important role for large scale changes of atmospheric trace gas concentrations (e.g., by modulating the ocean carbon sink characteristics) with possible implications for coupled climate models. To date, detailed knowledge about the composition, structure, and reactivity of the sea surface nanolayer is still scarce. Due to its small vertical dimension and the small amount of material, this surfactant layer is very difficult to separate and analyse. A way out is the application of second-order nonlinear optical methods, which make a direct surface-specific and background-free detection of this interfacial layer possible. In recent years, we have introduced the use of vibrational sum frequency generation (VSFG) spectroscopy to gain insight into natural and artificial organic monolayers at the air-water interface. In this contribution, the application of VSFG spectroscopy for the analysis of the sea surface nanolayer will be illustrated. Resulting spectra are interpreted in terms of layer composition and surfactant classes, in particular with respect to carbohydrate-containing molecules such as glycolipids. The partitioning of the detected surfactants into soluble and non-soluble ("wet" and "dry") surfactants will be

  16. Future surface mass balance of the Antarctic ice sheet and its influence on sea level change, simulated by a regional atmospheric climate model

    NARCIS (Netherlands)

    Ligtenberg, S.R.M.|info:eu-repo/dai/nl/32821177X; van de Berg, W.J.|info:eu-repo/dai/nl/304831611; van den Broeke, M.R.|info:eu-repo/dai/nl/073765643; Rae, J.G.L.; van Meijgaard, E.

    2013-01-01

    A regional atmospheric climate model with multi-layer snow module (RACMO2) is forced at the lateral boundaries by global climate model (GCM) data to assess the future climate and surface mass balance (SMB) of the Antarctic ice sheet (AIS). Two different GCMs (ECHAM5 until 2100 and HadCM3 until 2200)

  17. Rocket dust storms and detached dust layers in the Martian atmosphere

    Science.gov (United States)

    Spiga, Aymeric; Faure, Julien; Madeleine, Jean-Baptiste; Määttänen, Anni; Forget, François

    2013-04-01

    Airborne dust is the main climatic agent in the Martian environment. Local dust storms play a key role in the dust cycle; yet their life cycle is poorly known. Here we use mesoscale modeling that includes the transport of radiatively active dust to predict the evolution of a local dust storm monitored by OMEGA on board Mars Express. We show that the evolution of this dust storm is governed by deep convective motions. The supply of convective energy is provided by the absorption of incoming sunlight by dust particles, rather than by latent heating as in moist convection on Earth. We propose to use the terminology "rocket dust storm," or conio-cumulonimbus, to describe those storms in which rapid and efficient vertical transport takes place, injecting dust particles at high altitudes in the Martian troposphere (30-50 km). Combined to horizontal transport by large-scale winds, rocket dust storms produce detached layers of dust reminiscent of those observed with Mars Global Surveyor and Mars Reconnaissance Orbiter. Since nighttime sedimentation is less efficient than daytime convective transport, and the detached dust layers can convect during the daytime, these layers can be stable for several days. The peak activity of rocket dust storms is expected in low-latitude regions at clear seasons (late northern winter to late northern summer), which accounts for the high-altitude tropical dust maxima unveiled by Mars Climate Sounder. Dust-driven deep convection has strong implications for the Martian dust cycle, thermal structure, atmospheric dynamics, cloud microphysics, chemistry, and robotic and human exploration.

  18. Applications of the Remotely Piloted Aircraft (RPA) 'MASC' in Atmospheric Boundary Layer Research

    Science.gov (United States)

    Wildmann, Norman; Platis, Andreas; Tupman, David-James; Bange, Jens

    2015-04-01

    The remotely piloted aircraft (RPA) MASC (Multipurpose Airborne Sensor Carrier) was developed at the University of Tübingen in cooperation with the University of Stuttgart, University of Applied Sciences Ostwestfalen-Lippe and 'ROKE-Modelle'. Its purpose is the investigation of thermodynamic processes in the atmospheric boundary layer (ABL), including observations of temperature, humidity and wind profiles, as well as the measurement of turbulent heat, moisture and momentum fluxes. The aircraft is electrically powered, has a maximum wingspan of 3.40~m and a total weight of 5-8~kg, depending on the battery- and payload. The standard meteorological payload consists of two temperature sensors, a humidity sensor, a flow probe, an inertial measurement unit and a GNSS. The sensors were optimized for the resolution of small-scale turbulence down to length scales in the sub-meter range. In normal operation, the aircraft is automatically controlled by the ROCS (Research Onboard Computer System) autopilot to be able to fly predefined paths at constant altitude and airspeed. Only take-off and landing are carried out by a human RC pilot. Since 2012, the system is operational and has since then been deployed in more than ten measurement campaigns, with more than 100 measurement flights. The fields of research that were tackled in these campaigns include sensor validation, fundamental boundary-layer research and wind-energy research. In 2014, for the first time, two MASC have been operated at the same time within a distance of a few kilometres, in order to investigate the wind field over an escarpment in the Swabian Alb. Furthermore, MASC was first deployed off-shore in October 2014, starting from the German island Heligoland in the North Sea, for the purpose of characterization of the marine boundary layer for offshore wind parks. Detailed descriptions of the experimental setup and first preliminary results will be presented.

  19. High-Resolution Profiling of Richardson Number Across the Surface Boundary Layer Using Heated Fiber Optics

    Science.gov (United States)

    Sayde, C.; Higgins, C. W.; Perdosa, R.; Mahaffee, W.; Selker, J. S.

    2016-12-01

    Most critical atmospheric processes are a balance between buoyancy and shear, typically measured with the Richardson number. The fine scale motions associated with critical or near critical valued of Richardson number are understudied because the location and timing of these events are not known a-priori. To study these motions and quantify their importance for transport of heat momentum and water vapor in the atmospheric boundary layer, a distributed measurement approach for temperature and wind speed is required. Here we present the results of 12.5 cm resolution distributed profiling of wind speed and temperature for the first 37 m of the surface boundary layer. Distributed Temperature Sensing (DTS) technology was employed to measure temperature every 5 s and 12.5 cm along two Fiber Optics (FO) cables suspended from 37 m elevation to ground by a blimp anchored above a vineyard in the Willamette Valley, Oregon. 3D printed FO holders installed every 3 m along the suspended FO cables insured constant spacing of 7.5 cm between the two cables. The first FO cable was 0.9mm in diameter and reported ambient air temperature. The second FO cable was embedded in a thin stainless steel tube (1.3 mm OD) continuously heated by an electrical current to provide continuous wind speed measurements every 12.5 cm along the heated cable. Analogous to a hot-wire anemometer, this approach is based on the principal of velocity-dependent heat transfer from a heated surface. The co-located wind speed and ambient temperature measurements are used to calculate Richardson number with a spatial and temporal resolution of 12.5 cm and 5 s respectively for the first 37 m of the surface boundary layer. The equipment employed, including the heating system, which is available to all US scientists, was provided by CTEMPs.org thanks to the generous grant support from the National Science Foundation under Grant Number EAR 0930061. Any opinions, findings, and conclusions or recommendations expressed in

  20. Surface conductivity dependent dynamic behaviour of an ultrafine atmospheric pressure plasma jet for microscale surface processing

    Energy Technology Data Exchange (ETDEWEB)

    Abuzairi, Tomy [Graduate School of Science and Technology, Shizuoka University, Hamamatsu 432-8561 (Japan); Department of Electrical Engineering, Faculty of Engineering, Universitas Indonesia, Depok 16424 (Indonesia); Okada, Mitsuru [Department of Engineering, Shizuoka University, Hamamatsu 432-8561 (Japan); Bhattacharjee, Sudeep [Department of Physics, Indian Institute of Technology, Kanpur 208016 (India); Nagatsu, Masaaki, E-mail: nagatsu.masaaki@shizuoka.ac.jp [Graduate School of Science and Technology, Shizuoka University, Hamamatsu 432-8561 (Japan); Department of Engineering, Shizuoka University, Hamamatsu 432-8561 (Japan); Research Institute of Electronics, Shizuoka University, Hamamatsu 432-8561 (Japan)

    2016-12-30

    Highlights: • Spatio-temporal behaviors of capillary APPJs are studied for various substrates. • Plasma irradiation area depended on the substrate conductivity and permittivity. • Surface irradiation area was significantly broadened in polymer-like substrate. • Effect of applying a substrate bias on the APPJ irradiation area was investigated. - Abstract: An experimental study on the dynamic behaviour of microcapillary atmospheric pressure plasma jets (APPJs) with 5 μm tip size for surfaces of different conductivity is reported. Electrical and spatio-temporal characteristics of the APPJs are monitored using high voltage probe, current monitor and high speed intensified charge couple device camera. From these experimental results, we presented a simple model to understand the electrical discharge characteristics of the capillary APPJs with double electrodes, and estimated the velocity of the ionization fronts in the jet and the electron density to be 3.5–4.2 km/s and 2–7 × 10{sup 17} m{sup −3}. By analyzing the dynamics of the microcapillary APPJs for different substrate materials, it was found that the surface irradiation area strongly depended on the substrate conductivity and permittivity, especially in the case of polymer-like substrate, surface irradiation area was significantly broadened probably due to the repelling behaviour of the plasma jets from the accumulated electrical charges on the polymer surface. The effect of applying a substrate bias in the range from −900 V to +900 V on the plasma irradiation onto the substrates was also investigated. From the knowledge of the present results, it is helpful for choosing the substrate materials for microscale surface modification.

  1. 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

  2. Cell surface hydrophobicity is conveyed by S-layer proteins - A study in recombinant lactobacilli

    NARCIS (Netherlands)

    Mei, H.C. van der; Belt-Gritter, B. van de; Pouwels, P.H.; Martinez, B.; Busscher, H.J.

    2003-01-01

    Cell surface hydrophobicity is one of the most important factors controlling adhesion of microorganisms to surfaces. In this paper, cell surface properties of lactobacilli and recombinant lactobacilli with and without a surface layer protein (SLP) associated with cell surface hydrophobicity were

  3. Cell surface hydrophobicity is conveyed by S-layer proteins - a study in recombinant lactobacilli

    NARCIS (Netherlands)

    van der Mei, HC; van de Belt-Gritter, B; Pouwels, PH; Martinez, B; Busscher, HJ

    2003-01-01

    Cell surface hydrophobicity is one of the most important factors controlling adhesion of microorganisms to surfaces. In this paper, cell surface properties of lactobacilli and recombinant lactobacilli with and without a surface layer protein (SLP) associated with cell surface hydrophobicity were

  4. Comparison of some effects of modification of a polylactide surface layer by chemical, plasma, and laser methods

    Energy Technology Data Exchange (ETDEWEB)

    Moraczewski, Krzysztof, E-mail: kmm@ukw.edu.pl [Department of Materials Engineering, Kazimierz Wielki University, Department of Materials Engineering, ul. Chodkiewicza 30, 85-064 Bydgoszcz (Poland); Rytlewski, Piotr [Department of Materials Engineering, Kazimierz Wielki University, Department of Materials Engineering, ul. Chodkiewicza 30, 85-064 Bydgoszcz (Poland); Malinowski, Rafał [Institute for Engineering of Polymer Materials and Dyes, ul. M. Skłodowskiej–Curie 55, 87-100 Toruń (Poland); Żenkiewicz, Marian [Department of Materials Engineering, Kazimierz Wielki University, Department of Materials Engineering, ul. Chodkiewicza 30, 85-064 Bydgoszcz (Poland)

    2015-08-15

    Highlights: • We modified polylactide surface layer with chemical, plasma or laser methods. • We tested selected properties and surface structure of modified samples. • We stated that the plasma treatment appears to be the most beneficial. - Abstract: The article presents the results of studies and comparison of selected properties of the modified PLA surface layer. The modification was carried out with three methods. In the chemical method, a 0.25 M solution of sodium hydroxide in water and ethanol was utilized. In the plasma method, a 50 W generator was used, which produced plasma in the air atmosphere under reduced pressure. In the laser method, a pulsed ArF excimer laser with fluency of 60 mJ/cm{sup 2} was applied. Polylactide samples were examined by using the following techniques: scanning electron microscopy (SEM), atomic force microscopy (AFM), goniometry and X-ray photoelectron spectroscopy (XPS). Images of surfaces of the modified samples were recorded, contact angles were measured, and surface free energy was calculated. Qualitative and quantitative analyses of chemical composition of the PLA surface layer were performed as well. Based on the survey it was found that the best modification results are obtained using the plasma method.

  5. Seasonal cycles of surface layer salinity in the Pacific Ocean

    Directory of Open Access Journals (Sweden)

    F. M. Bingham

    2010-08-01

    Full Text Available The seasonal variability of surface layer salinity (SLS is examined in the Pacific Ocean between 40° S and 60° N using a variety of data sources. Significant seasonal cycles were found in 5 regions: 1 The western North Pacific, 2 The northeastern North Pacific and Alaska gyre, 3 the intertropical convergence zone (ITCZ, 4 an area of the central North Pacific north of the Hawaiian Islands, 5 the central South Pacific along 10–20° S. Amplitudes range from 0.1 to > 0.5. The largest amplitudes are in the tropical band and the western North Pacific. Maximum salinity is obtained in late (northern winter in the western North Pacific, late winter and early spring in the northeastern North Pacific, early summer in the ITCZ area, late summer and early fall in the central North Pacific area and (austral winter in the central South Pacific. Large areas of the Pacific have no significant seasonal variation in SLS.

    Seasonal variability of evaporation rate, precipitation rate and the difference between them (E-P were calculated from the OAFlux and Global Precipitation Climatology Project datasets. Typical amplitudes of E-P are 0.1–1 × 10−4 kg m−2 s−1. The seasonal variability of E-P is largely dominated by variability in evaporation in the western North Pacific and precipitation elsewhere. The largest amplitudes are in areas along the edge of the western North Pacific and in the far eastern tropical Pacific around 10° N. Phases in these areas indicate maximum E-P in mid- to late winter in these areas of large amplitude. The closest correspondence between E-P and SLS is in the ITCZ. E-P was combined with seasonal variation of the mixed-layer depth to calculate the freshwater flux forcing term of the SLS balance equation. The term was found to be similar in magnitude and distribution to E-P. Some other terms of the SLS balance were calculated. Horizontal advection was found to have seasonal cycles in a

  6. A micro-meteorological experiment in the atmospheric boundary layer in Highveld region

    Energy Technology Data Exchange (ETDEWEB)

    Esau, I N; Zilitinkevich, S S [G.C. Rieber Climate Institute of Nansen Environmental and Remote Sensing Center, Thoermohlensgate 47, 5006, Bergen (Norway); Djolov, G; Rautenbach, C J deW, E-mail: igor.ezau@nersc.n [University of Pretoria (South Africa)

    2010-08-15

    Meteorology of the planetary boundary layer (PBL) is to large extent determined by turbulent processes. Those processes and their interaction with surface properties are not well understood. The processes over heterogeneous land surfaces are understood even less. To progress in the understanding simultaneous observations with a network of meteorological stations are needed. A joint project between Norwegian and South African research foundations funded a micrometeorological experiment in the Highveld area of the South Africa (MMEH). The experiment has been organized to collect data from 5 automatic meteorological stations placed at 7 km to 23 km separation distances from each other. The data were collected continuously over 2 years. This paper presents the idea, the theoretical background and the organization of the MMEH.

  7. A micro-meteorological experiment in the atmospheric boundary layer in Highveld region

    Science.gov (United States)

    Esau, I. N.; Zilitinkevich, S. S.; Djolov, G.; deW Rautenbach, C. J.

    2010-08-01

    Meteorology of the planetary boundary layer (PBL) is to large extent determined by turbulent processes. Those processes and their interaction with surface properties are not well understood. The processes over heterogeneous land surfaces are understood even less. To progress in the understanding simultaneous observations with a network of meteorological stations are needed. A joint project between Norwegian and South African research foundations funded a micrometeorological experiment in the Highveld area of the South Africa (MMEH). The experiment has been organized to collect data from 5 automatic meteorological stations placed at 7 km to 23 km separation distances from each other. The data were collected continuously over 2 years. This paper presents the idea, the theoretical background and the organization of the MMEH.

  8. Towards a fundamentally new understanding of the marine atmospheric boundary layer

    DEFF Research Database (Denmark)

    Smedman, Ann-Sofi; Högström, U.; Larsén, Xiaoli Guo

    2004-01-01

    measurements of the wave field, Donelan et al. (1997), Drennan et al. (1999), Rieder and Smith (1998) and our own studies (see below), that effects from waves are of fundamental importance for the turbulent exchange processes in the marine boundary layer and should be included in parameterizations in models....... This contribution summarizes results from measurements during an eight-year period (May, 1995 – present) at the air-sea interaction station Östergarnsholm in the Baltic Sea. It illustrates vividly that the ‘classical’ concept of the sea surface as an analogue to a solid surface with moving roughness elements...... is valid only for the much studied case of growing waves and that understanding the role of relatively long waves, which travel faster than the wind, is crucial for a correct treatment of the air-sea exchange processes....

  9. Strain relaxation induced surface morphology of heterogeneous GaInNAs layers grown on GaAs substrate

    Science.gov (United States)

    Gelczuk, Ł.; Jóźwiak, G.; Moczała, M.; Dłużewski, P.; Dąbrowska-Szata, M.; Gotszalk, T. P.

    2017-07-01

    The partially-relaxed heterogeneous GaInNAs layers grown on GaAs substrate by atmospheric pressure vapor phase epitaxy (AP-MOVPE) were investigated by transmission electron microscopy (TEM) and atomic force microscopy (AFM). The planar-view TEM image shows a regular 2D network of misfit dislocations oriented in two orthogonal crystallographic directions at the (0 0 1) layer interface. Moreover, the cross-sectional view TEM image reveals InAs-rich and V-shaped precipitates in the near surface region of the GaInNAs epitaxial layer. The resultant undulating surface morphology, known as a cross-hatch pattern, is formed as observed by AFM. The numerical analysis of the AFM image of the GaInNAs layer surface with the well-defined cross-hatch morphology enabled us to determine a lower bound of actual density of misfit dislocations. However, a close correspondence between the asymmetric distribution of interfacial misfit dislocations and undulating surface morphology is observed.

  10. Erosion processes in molassic cliffs: the role of the rock surface temperature and atmospheric conditions

    Science.gov (United States)

    Carrea, Dario; Abellán, Antonio; Guerin, Antoine; Jaboyedoff, Michel; Voumard, Jérémie

    2014-05-01

    The morphology of the Swiss Plateau is modeled by numerous steep cliffs of Molasse. These cliffs are mainly composed of sub-horizontal alternated layers of sandstone, shale and conglomerates deposed in the Alps foreland basin during the Tertiary period. These Molasse cliffs are affected by erosion processes inducing numerous rockfall events. Thus, it is relevant to understand how different external factors influence Molasse erosion rates. In this study, we focus on analyzing temperature variation during a winter season. As pilot study area we selected a cliff which is formed by a sub-horizontal alternation of outcropping sandstone and shale. The westward facing test site (La Cornalle, Vaud, Switzerland), which is a lateral scarp of a slow moving landslide area, is currently affected by intense erosion. Regarding data acquisition, we monitored both in-situ rock and air temperatures at 15 minutes time-step since October 2013: (1) on the one hand we measured Ground Surface Temperature (GST) at near-surface (0.1 meter depth) using a GST mini-datalogger M-Log5W-Rock model; (2) On the other hand we monitored atmospheric conditions using a weather station (Davis Vantage pro2 plus) collecting numerous parameters (i.e. temperature, irradiation, rain, wind speed, etc.). Furthermore, the area was also seasonally monitored by Ground-Based (GB) LiDAR since 2010 and monthly monitored since September 2013. In order to understand how atmospheric conditions (such as freeze and thaw effect) influence the erosion of the cliff, we modeled the temperature diffusion through the rock mass. To this end, we applied heat diffusion and radiation equation using a 1D temperature profile, obtaining as a result both temperature variations at different depths together with the location of the 0°C isotherm. Our model was calibrated during a given training set using both in-situ rock temperatures and atmospheric conditions. We then carried out a comparison with the rockfall events derived from the

  11. OASIS-CANADA: observations of boundary layer ozone and mercury depletion from the Arctic Ocean surface

    Science.gov (United States)

    Bottenheim, J. W.; Netcheva, S.; Staebler, R.; Steffen, A.

    2009-04-01

    Dramatic depletion of ozone (O3) and gaseous elementary mercury (GEM) from the marine boundary layer during the spring in Polar Regions is known to be driven by bromine atoms originating from activation of seasalt bromide. Almost all surface based measurements have been made at coastal observatories, but much of the active processing of the air is believed to occur near or at the surface of the Arctic Ocean itself. A major objective of the OASIS (Ocean Atmosphere Sea Ice and Snow) program during the International Polar Year (IPY) was therefore to make observations directly over the frozen Arctic Ocean. In the context of the OASIS-CANADA program, sponsored by the Canadian Federal Program Office of the IPY, several ocean bound campaigns were joined including the French TARA expedition (2006-2008), the CFL campaign on the Canadian ice breaker CCGS Amundsen (February-April 2008), the COBRA campaign over the Hudson Bay near Kuujjuaraapik/Whapmagoostui, Quebec (February-March 2008), the ASCOS campaign on the Swedish polar class ice breaker Oden to the North Pole (August-September 2008), and the OASIS-09 campaign at Barrow Alaska (February-March 2009). In this presentation I will summarize the observations and explore what has been learned regarding the drivers for the depletion process, such as the influence of the ambient temperature, the nature of the underlying surface, and the atmospheric stability. An important question is whether depletion in progress was observed, rather than the arrival of previously depleted air, as is generally the case at Arctic coastal observatories.

  12. Identification of a surface layer structure and analysis of humidity ...

    Indian Academy of Sciences (India)

    Author Affiliations. N Das1 M Bose2 U K De1. Environmental Science Programme, Jadavpur University, Kolkata 700 032, India; Atmospheric Science Research Group, Physics Department, Jadavpur University, Kolkata 700 032, India ...

  13. Superconductivity of the surface layers of the doped PbTe:Eu crystals

    Energy Technology Data Exchange (ETDEWEB)

    Zayachuk, D.M., E-mail: zayachuk@polynet.lviv.ua [Lviv Polytechnic National University, 12 Bandera St., 79013 Lviv (Ukraine); Mikityuk, V.I.; Shlemkevych, V.V. [Yuriy Fedkovych Chernivtsy National University, 2 Kotsyubynsky St., 58012 Chernivtsy (Ukraine); Kaczorowski, D. [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wroclaw 2 (Poland); Ilyina, O.S. [Lviv Polytechnic National University, 12 Bandera St., 79013 Lviv (Ukraine)

    2012-12-14

    We present evidence of superconductivity of the surface layers of PbTe crystals grown from melt and doped with Eu during growth. We have studied two different type of the powder samples made out of the surface layer and from bulk of the PbTe:Eu ingots. The magnetization in the range of magnetic field 0-5 T and the magnetic susceptibility (MS) in the temperature range 1.7-400 K were investigated. At low temperatures, a strong diamagnetism of the surface layers of the PbTe:Eu ingot is observed whereas at high temperatures a transition to strong paramagnetism takes place. This effect is attributed to the transition of the PbTe:Eu surface layers to state of superconductivity at low temperature. The superconductivity of the doped surface layers is explained by formation of the Pb-based inclusions within the ingot surface.

  14. Massive-scale aircraft observations of giant sea-salt aerosol particle size distributions in atmospheric marine boundary layers

    Science.gov (United States)

    Jensen, J. B.

    2015-12-01

    iant sea-salt aerosol particles (dry radius, rd > 0.5 μm) occur nearly everywhere in the marine boundary layer and frequently above. This study presents observations of atmospheric sea-salt size distributions in the range 0.7 Chile and the 2011 ICE-T in the Caribbean. In each deployment, size distributions using hundreds of slides are used to relate fitted log-normal size distributions parameters to wind speed, altitude and other atmospheric conditions. The size distributions provide a unique observational set for initializing cloud models with coarse-mode aerosol particle observations for marine atmospheres.

  15. Surface heterogeneity impacts on boundary layer dynamics via energy balance partitioning

    Science.gov (United States)

    The role of land-atmosphere interactions under heterogeneous surface conditions is investigated in order to identify mechanisms responsible for altering surface heat and moisture fluxes. Twelve coupled land surface – large eddy simulation scenarios with four different length scales of surface variab...

  16. Influence of the surface layer characteristics on the regularities of the cutting process

    Directory of Open Access Journals (Sweden)

    Krainev Dmitriy V.

    2017-01-01

    Full Text Available The article considers the influence of the surface layer characteristics on the regularities of the cutting process and the formation of the quality of the surface machined. This effect has been confirmed by the study results of the combined cutting method with advanced plastic deformation (APD. The work estimates the impact of the change in the surface layer properties on the forces and temperature of cutting, stability of the chip formation and quality parameters of the surface machined.

  17. Arctic summertime measurements of ammonia in the near-surface atmosphere

    Science.gov (United States)

    Moravek, A.; Murphy, J. G.; Wentworth, G.; Croft, B.; Martin, R.

    2016-12-01

    Measurements of gas-phase ammonia (NH3) in the summertime Arctic are rare, despite the impact NH3 can have on new particle formation rates and nitrogen deposition. The presence of NH3 can also increase the ratio of particulate-phase ammonium (NH4+) to non-sea salt sulphate (nss-SO42-) which decreases particle acidity. Known regional sources of NH3in the Arctic summertime include migratory seabird colonies and northern wildfires, whereas the Arctic Ocean is a net sink. In the summer of 2016, high time resolution measurements were collected in the Arctic to improve our understanding of the sources, sinks and impacts of ammonia in this remote region. A four week study was conducted at Alert, Canada (82.5º N, 62.3 º W) from June 23 to July 19, 2016 to examine the magnitude and sources of NH3 and SO42-. The Ambient Ion Monitor-Ion Chromatography system (AIM-IC) provided on-line, hourly averaged measurements of NH3, NH4+, SO42- and Na+. Measurements of NH3 ranged between 50 and 700 pptv (campaign mean of 240 pptv), consistent with previous studies in the summertime Arctic boundary layer. Levels of NH4+ and nss-SO42- were near or below detection limits ( 20 ng m-3) for the majority of the study. Tundra and lake samples were collected to investigate whether these could be important local sources of NH3 at Alert. These surface samples were analyzed for NH4+, pH and temperature and a compensation point (χ) for each sample was calculated to determine if these surface reservoirs can act as net NH3 sources. Precipitation samples were also collected throughout the study to better constrain our understanding of wet NH4+deposition in the summertime Arctic. From mid-July through August, 2016, NH3 was measured continuously using a laser spectroscopy technique onboard the Canadian Coast Guard Ship Amundsen in the eastern Arctic Ocean. Ocean-atmosphere exchange of NH3 was quantified using measurements of sea surface marine NH4+ concentrations. In addition, wet deposition of

  18. Decadal Arctic surface atmosphere/ocean heat budgets and mass transport estimates from several atmospheric and oceanic reanalyses

    Science.gov (United States)

    Chepurin, gennaday; Carton, James

    2017-04-01

    The Arctic is undergoing dramatic changes associated with the loss of seasonal and permanent ice pack. By exposing the surface ocean to the atmosphere these changes dramatically increase surface exchange processes. In contrast, increases in freshwater and heat input decreases turbulent exchanges within the ocean. In this study we present results from an examination of changing ocean heat flux, storage, and transport during the 36 year period 1980-2015. To identify changes in the surface atmosphere we examine three atmospheric reanalyses: MERRA2, ERA-I, and JRA55. Significant differences in fluxes from these reanalyses arise due to the representation of clouds and water vapor. These differences provide an indication of the uncertainties in the historical record. Next we turn to the Simple Ocean Data Assimilation version 3 (SODA3) global ocean/sea ice reanalysis system to allow us to infer the full ocean circulation from the limited set of historical record of ocean observations. SODA3 has 10 km horizontal resolution in the Arctic and assimilates the full suite of historical marine temperature and salinity observations. To account for the uncertainties in atmospheric forcing, we repeat our analysis with each of the three atmospheric reanalyses. In the first part of the talk we review the climatological seasonal surface fluxes resulting from our reanalysis system, modified for consistency with the ocean observations, and the limits of what we can learn from the historical record. Next we compare the seasonal hydrography, heat, and mass transports with direct estimates from moorings. Finally we examine the impact on the Arctic climate of the changes in sea ice cover and variability and trends of ocean/sea ice heat storage and transport and their contributions to changes in the seasonal stratification of the Arctic Ocean.

  19. Surface analysis of topmost layer of epitaxial layered oxide thin film: Application to delafossite oxide for oxygen evolution reaction

    Science.gov (United States)

    Toyoda, Kenji; Adachi, Hideaki; Miyata, Nobuhiro; Hinogami, Reiko; Orikasa, Yuki; Uchimoto, Yoshiharu

    2018-02-01

    Delafossite oxides (ABO2) have a layered structure with alternating layers of A and B elements, the topmost layer of which appears to determine their performance, such as the oxygen evolution reaction (OER) activity. In this study, we investigated the topmost layer of single-domain (0 0 1)-oriented AgCoO2 epitaxial thin film for potential use as an OER catalyst. The thin film was confirmed to possess OER activity at a level comparable to the catalyst in powder form. Atomic scattering spectroscopy revealed the topmost layer to be composed of CoO6 octahedra. In situ X-ray absorption spectroscopy showed that the oxidation of Co at the surface did not change under different potentials, which suggests that there is no valence fluctuation of Co in the stable CoO6 octahedral structure. However, the oxidation number of Co at the surface was lower than that in the bulk. Our density functional theoretical calculations also showed the Co atoms at the surface to have a slightly higher electron occupancy than those in the bulk, and suggests that the unoccupied t2g states of Co at the surface have an influence on OER activity.

  20. Atmospheric boundary layer dynamics in the Grenoble valley during strongly stable episodes

    Science.gov (United States)

    Staquet, C.; Largeron, Y.; Chollet, J.

    2013-12-01

    This paper addresses the dynamics of the atmospheric boundary layer in the Grenoble valley under strongly stable and polluted conditions. Numerical modeling is used for this purpose, along with available ground temperature measurements. Though the Grenoble valley is the most populated area in the Alps and is subjected to serious pollution episodes in winter, no such study had been conducted previously. We first analyzed ground temperature data within the valley at altitudes ranging between 220 m (valley bottom) and 1730 m during 5 months of winter 2006-2007. These data were provided by Meteo-France et by Air Rhône-Alpes, the air quality agency of Région Rhône-Alpes. Our purpose was to detect strongly stable episodes, these being defined by the episode-averaged vertical gradient of the absolute temperature being larger than the winter average during at least three days. Five episodes were selected from this criterion. We also analyzed air quality data recorded by Air Rhône-Alpes during the same winter to detect strongly polluted events for PM10 and found that the five episodes were also strongly polluted ones. To perform a more detailed analysis of these five episodes, we used the numerical code Meso-NH developed by Météo-France and the Laboratory of Aérology in Toulouse and simulated the dynamics of the atmospheric boundary layer during each episode. Four nested domains were used, the horizontal resolution of the innermost (and smallest) domain, containing the Grenoble valley, being 333 m; from comparison with the ground temperature data, we found that the vertical resolution above ground level had to be as low as 4 meters. As expected, the boundary layer dynamics in the numerical simulation for each episode was found to be decoupled from the (anticyclonic, weak) synoptic flow, consistent with the value of the Froude number associated with the inversion layer. These dynamics are controlled by thermal (mostly katabatic) winds flowing from the higher altitude

  1. SAFARI 2000 Surface Atmospheric Radiative Transfer (SMART), Dry Season 2000

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: Surface-sensing Measurements for Radiative Transfer (SMART) and Chemical, Optical, and Microphysical Measurements of In-situ Troposphere (COMMIT) consist...

  2. Surface modification of layered zirconium phosphates: a novel pathway to multifunctional materials.

    Science.gov (United States)

    Mosby, Brian M; Díaz, Agustín; Clearfield, Abraham

    2014-07-21

    The intercalation of inorganic layered materials has resulted in a wide range of applicability. In such cases the applicability of the material is largely dependent upon the species intercalated within the layer, and the layered material acts largely as a host. Recently, the surface modification of inorganic layered materials has been investigated and it has been shown that the exterior layers can be exclusively functionalized. The advent of surface chemistry allows for the synthesis of particles with both a controlled interlayer and surface. This approach can be used to tailor nanoparticles for specific applications. Herein we review the surface chemistry of α-zirconium bis(monohydrogen orthophosphate) monohydrate (Zr(HPO4)2·H2O, α-ZrP) along with some applications of recent interest. Not only can these reactions be applied to α-ZrP, but similar chemistry can also be expanded to other layered materials and systems.

  3. Climatology of wintertime long-distance transport of surface-layer air masses arriving urban Beijing in 2001-2012

    Science.gov (United States)

    Chen, Bin; Xiang-De, XU

    2017-02-01

    In this study, the FLEXPART-WRF coupled modeling system is used to conduct 12-year Lagrangian modeling over Beijing, China, for the winters of 2001-2012. Based on large trajectory tracking ensembles, the long-range air transport properties, in terms of geographic source regions within the atmospheric planetary boundary layer (PBL) and large-scale ventilation, and its association with air quality levels were quantified from a climatological perspective. The results show the following: (1) The air masses residing in the near-surface layer over Beijing potentially originate from broader atmospheric boundary-layer regions, which cover vast areas with the backward tracking time elapsed. However, atmospheric transport from northeastern China and, to a lesser extent, from the surrounding regions of Beijing is important. (2) The evolution of air quality over Beijing is negatively correlated with large-scale ventilation conditions, particularly at a synoptic timescale. Thus, the simple but robust backward-trajectory ventilation (BV) index defined in this study could facilitate operational forecasting of severe air pollution events. (3) By comparison, the relatively short-range transport occurring over transport timescales of less than 3 days from southern and southeastern Beijing and its surrounding areas plays a vital role in the formation of severe air pollution events during the wintertime. (4) Additionally, an interannual trend analysis suggests that the geographic sources and ventilation conditions also changed, at least over the last decade, corresponding to the strength variability of the winter East Asian monsoon.

  4. Interactions between dry-air entrainment, surface evaporation and convective boundary-layer development

    NARCIS (Netherlands)

    Heerwaarden, van C.C.; Vilà-Guerau de Arellano, J.; Moene, A.F.; Holtslag, A.A.M.

    2009-01-01

    The influence of dry-air entrainment on surface heat fluxes and the convective boundary-layer (CBL) properties is studied for vegetated land surfaces, using a mixed-layer CBL model coupled to the Penman¿Monteith equation under a wide range of conditions. In order to address the complex behaviour of

  5. Surface measurements of global warming causing atmospheric constituents in Korea.

    Science.gov (United States)

    Oh, S N; Youn, Y H; Park, K J; Min, H K; Schnell, R C

    2001-07-01

    The expansion of the industrial economy and the increase of population in Northeast Asian countries have caused much interest in climate monitoring related to global warming. However, new techniques and better platforms for the measurement of global warming and regional databases are still old-fashioned and are not being developed sufficiently. With respect to this agenda, since 1993, at the request of the World Meteorological Organization (WMO), to monitor functions of global warming, the Korea Meteorological Administration (KMA) has set up a Global Atmospheric Watch (GAW) Station on the western coast of Korea (Anmyun-do) and has been actively monitoring global warming over Northeast Asia. In addition, atmospheric carbon dioxide (CO2) has been measured for a similar KMA global warming program at Kosan, Cheju Island since 1990. Aerosol and radiation have also been measured at both sites as well as in Seoul. The observations have been analyzed using diagnostics of climate change in Northeast Asia and also have been internationally compared. Results indicate that greenhouse gases are in good statistic agreement with the NOAA/Climate Monitoring and Diagnostics Laboratory (CMDL) long-term trends of monthly mean concentrations and seasonal cycles. Atmospheric particulate matter has also been analyzed for particular Asian types in terms of optical depth, number concentration and size distribution.

  6. Cosmic rays intensity and atmosphere humidity at near earth surface

    Science.gov (United States)

    Oskomov, V. V.; Sedov, A. N.; Saduyev, N. O.; Kalikulov, O. A.; Naurzbayeva, A. Zh; Alimgazinova, N. Sh; Kenzhina, I. E.

    2016-08-01

    Experimental studies of estimation the mutual influence of humidity and flux of cosmic rays in first approximation were carried out. Normalized cross-correlation function of time series of neutron monitors count rate and level of relative atmosphere humidity near cosmic rays registration point is studied. Corrected and uncorrected on pressure minute and hour data of 6NM64 neutron monitor count rate were used for the study. Neutron monitor is located in Al-Farabi Kazakh National University, at an altitude of 850 m above sea level. Also, data from NM64 neutron monitor of Tien Shan mountain research station of Institute of Ionosphere, located at an altitude of 3340 m above sea level were used. Uncorrected on pressure cosmic rays intensity better reflects the changes in relative atmosphere humidity. Average and sometimes strong relationship is often observed by time changes of atmosphere humidity near the point of cosmic rays detection and their intensity: the value of normalized cross-correlation function of respective signals, even in case of their long duration and a large number of data (eg, for minute changes at intervals of up to several months) covers 0.5 - 0.75 range, sometimes falling to ∼⃒ 0.4.

  7. Exploring atmospheric boundary layer characteristics in a severe SO2 episode in the north-eastern Adriatic

    Directory of Open Access Journals (Sweden)

    Z. B. Klaić

    2009-07-01

    Full Text Available Stable atmospheric conditions are often connected with the occurrence of high pollution episodes especially in urban or industrial areas. In this work we investigate a severe SO2 episode observed on 3–5 February 2002 in a coastal industrial town of Rijeka, Croatia, where very high daily mean concentrations (up to 353.5 μg m−3 were measured. The episode occurred under high air pressure conditions, which were accompanied with a fog and low wind speeds. Three air quality models (50-km EMEP model, 10-km EMEP4HR model and 1-km CAMx model were used to simulate SO2 concentrations fields and to evaluate the relative contribution of distant and local pollution sources to observed concentrations. Results suggest that the episode was caused predominately by local sources. Furthermore, using three-dimensional, higher-order turbulence closure mesoscale meteorological model (WRF, the wind regimes and thermo-dynamical structure of the lower troposphere above the greater Rijeka area (GRA were examined in detail. Modelled atmospheric fields suggest several factors whose simultaneous acting was responsible for elevated SO2 concentrations. Established small scale wind directions supported the transport of air from nearby industrial areas with major pollution sources towards Rijeka. This transport was associated with strong, ground-based temperature inversion and correspondingly, very low mixing layer (at most up to about 140 m. Additionally, the surface winds in Rijeka were light or almost calm thus, preventing ventilation of polluted air. Finally, a vertical circulation cell formed between the mainland and a nearby island, supported the air subsidence and the increase of static stability.

  8. Layer-by-Layer Method for the Synthesis and Growth of Surface Mounted Metal-Organic Frameworks (SURMOFs

    Directory of Open Access Journals (Sweden)

    Osama Shekhah

    2010-02-01

    Full Text Available A layer-by-layer method has been developed for the synthesis of metal-organic frameworks (MOFs and their deposition on functionalized organic surfaces. The approach is based on the sequential immersion of functionalized organic surfaces into solutions of the building blocks of the MOF, i.e., the organic ligand and the inorganic unit. The synthesis and growth of different types of MOFs on substrates with different functionalization, like COOH, OH and pyridine terminated surfaces, were studied and characterized with different surface characterization techniques. A controlled and highly oriented growth of very homogenous films was obtained using this method. The layer-by-layer method offered also the possibility to study the kinetics of film formation in more detail using surface plasmon resonance and quartz crystal microbalance. In addition, this method demonstrates the potential to synthesize new classes of MOFs not accessible by conventional methods. Finally, the controlled growth of MOF thin films is important for many applications like chemical sensors, membranes and related electrodes.

  9. Dynamics of altered surface layer formation on dissolving silicates

    Science.gov (United States)

    Daval, Damien; Bernard, Sylvain; Rémusat, Laurent; Wild, Bastien; Guyot, François; Micha, Jean Sébastien; Rieutord, François; Magnin, Valérie; Fernandez-Martinez, Alejandro

    2017-07-01

    The extrapolation of mineral dissolution kinetics experiments to geological timescales has frequently been challenged by the observation that mineral dissolution rates decrease with time. In the present study, we report a detailed investigation of the early stages of wollastonite dissolution kinetics, linking time-resolved measurements of wollastonite dissolution rate as a function of crystallographic orientation to the evolution of physicochemical properties (i.e., diffusivity, density, and thickness) of amorphous silica-rich layers (ASSLs) that developed on each surface. Batch dissolution experiments conducted at room temperature and at far-from-equilibrium conditions revealed that the initial (i.e., ASSL-free) dissolution rate of wollastonite (R(hkl)) based on Ca release observe the following trend: R(010) ≈R(100) >R(101) >R(001) . A gradual decrease of the dissolution rate of some faces by up to one order of magnitude resulted in a modification of this trend after two days: R(010) ≫R(100) ⩾R(101) ≈R(001) . In parallel, the diffusivity of ASSLs developed on each face was estimated based on the measurement of the concentration profile of a conservative tracer (methylene blue) across the ASSL using nanoSIMS. The apparent diffusion coefficients of methylene blue as a function of the crystallographic orientation (Dapp(hkl)) observe the following trend: Dapp(010) ⩾Dapp(100) >Dapp(101) ≫Dapp(001) , and decreases as a function of time for the (1 0 0) and (1 0 1) faces. Finally, the density of ASSL was estimated based on the modeling of X-ray reflectivity patterns acquired as a function of time. The density of ASSLs developed on the (0 1 0) faces remains low and constant, whereas it increases for the ASSLs developed on the (0 0 1) faces. On the whole, our results suggest that the impact of the formation of ASSLs on the wollastonite dissolution rate is anisotropic: while some crystal faces are weakly affected by the formation of non-passivating ASSLs (e

  10. Surface boundary layer evolution and near-inertial wind power input

    Science.gov (United States)

    Kilbourne, B. F.; Girton, J. B.

    2015-11-01

    Deep weakly stratified surface layers in the Southern Ocean complicate the identification of the mixed-layer base, which is critical in estimating the wind power input through the ocean surface. Typically used mixed-layer depth criteria often ignore weak stratification, which traps momentum near the surface and significantly enhances the near-inertial-band wind power input. The thickness of the active mixing-layer, the turbulent layer in contact with wind stress, is needed to accurately estimate wind power input. A fine-density-threshold criterion of 0.005 kg m-3, just above the noise floor of most autonomous instruments, was applied to observed profiles of potential density to estimate the thickness of the actively mixing-layer. Vertical shear, Langmuir cells, and buoyant convection are investigated as possible mechanisms maintaining turbulence within the mixing-layer. Over 90% of the observed variance of the mixing-layer thickness is explained by either shear-driven entrainment, which is simulated using the Price-Weller-Pinkel model, or by a parameterization of downwelling plumes due to Langmuir cell convergence. In general, surface buoyancy fluxes are too weak to drive mixed-layer turbulence. Comparison of National Oceanographic Data Center (NODC) climatological mixed-layer thickness to those determined using the 0.005 kg m-3 density threshold suggests a multiplicative seasonally varying correction of 1.5-3.5 should be applied to wind work estimates made using the NODC climatological mixed-layer thickness in the Southern Ocean.

  11. Evolving research directions in Surface Ocean-Lower Atmosphere (SOLAS) science

    NARCIS (Netherlands)

    Law, Cliff S.; Breviere, Emilie; de Leeuw, Gerrit; Garcon, Veronique; Guieu, Cecile; Kieber, David J.; Kontradowitz, Stefan; Paulmier, Aurelien; Quinn, Patricia K.; Saltzman, Eric S.; Stefels, Jacqueline; von Glasow, Roland

    2013-01-01

    This review focuses on critical issues in ocean-atmosphere exchange that will be addressed by new research strategies developed by the international Surface Ocean-Lower Atmosphere Study (SOLAS) research community. Eastern boundary upwelling systems are important sites for CO2 and trace gas emission

  12. Atmospheric boundary layer characteristics over the Pearl River Delta, China, during the summer of 2006: measurement and model results

    Directory of Open Access Journals (Sweden)

    S. J. Fan

    2011-07-01

    Full Text Available As part of the PRIDE-PRD2006 intensive campaign, atmospheric boundary layer (ABL measurements were performed in Qingyuan, Panyu, and Xinken over the Pearl River Delta (PRD on 1–30 July 2006. During the summer, the surface winds over the PRD are generally controlled by the south, usually with vertical wind shear at a height of approximately 800 m. Subsidence and precipitation from a tropical cyclone affects the air quality of the PRD. Under subsidence, wind speed in the ABL and the height of the ABL decrease and result in high-level concentrations. When the background wind speed is small or calm, the wind profile in Panyu and Xinken changes dramatically with height, which is perhaps caused by local circulation, such as sea-land breezes. To better understand the ABL of the PRD, simulations that used the Weather Research and Forecasting (WRF mesoscale model were utilized to analyze the ABL characteristics over the PRD. Based on three types of weather condition simulations (i.e., subsidence days, rainy days, and sunny days, the WRF model revealed that the simulated temperature and wind fields in these three cases were moderately consistent with the measurements. The results showed that diurnal variations of the ABL height on subsidence days and sunny days were obvious, but diurnal variations of the ABL height on rainy days were not apparent. The ABL is obviously affected by local circulation, and the ABL features are different at various stations. A simulation focused on a high pollution episode during the subsidence days on 12–15 July 2006, occurred under high-pressure conditions, accompanied by the tropical cyclone "Bilis". A comparison of the simulated vertical wind fields and temperature structure with the ABL measurements at Xinken, Panyu, and Qingyuan stations found that the modeled and measured atmospheric fields revealed two different types of ABL characteristics over the PRD. When the surface winds over the PRD were light or nearly calm

  13. Surface layer temperature inversion in the Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Pankajakshan, T.; Gopalakrishna, V.V.; Muraleedharan, P.M.; Reddy, G.V.; Araligidad, N.

    super (-1). The role of net surface heat flux in generating the observed inversions are examined from the climatological monthly estimates of the same derived from ISCCP (International Satellite Cloud Climatology Program), SRB (Surface Radiation Budget...

  14. Observed near-surface atmospheric moisture content changes affected by irrigation development in Xinjiang, Northwest China

    Science.gov (United States)

    Han, Songjun; Tang, Qiuhong; Xu, Di; Wang, Shaoli; Yang, Zhiyong

    2017-10-01

    The effects of irrigation development on observed near-surface atmospheric moisture changes remain unclear in arid Xinjiang. In this study, cultivated land fractions (CFs) within a 4-km radius of 90 meteorological stations over Xinjiang, which are inferred from the 2000 land use map, are used as a quantitative indicator of irrigation intensity. Trends of observed water vapor pressure and relative humidity during the growing season (May to September) from 1959 to 2006 are significantly positively correlated with CFs of the meteorological stations. Stations with larger CFs experience a more rapid increase in near-surface atmospheric moisture than stations with small CFs. Results indicate that growing season near-surface atmospheric moisture wetting is enhanced by irrigation development for stations with high levels of cultivated land uses. The land use around stations should be considered when analyzing the observed near-surface atmospheric moisture changes in Xinjiang.

  15. Land Surface Model (LSM 1.0) for Ecological, Hydrological, Atmospheric Studies

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: The NCAR LSM 1.0 is a land surface model developed to examine biogeophysical and biogeochemical land-atmosphere interactions, especially the effects of...

  16. Convergence of Extreme Value Statistics in a Two-Layer Quasi-Geostrophic Atmospheric Model

    Directory of Open Access Journals (Sweden)

    Vera Melinda Gálfi

    2017-01-01

    Full Text Available We search for the signature of universal properties of extreme events, theoretically predicted for Axiom A flows, in a chaotic and high-dimensional dynamical system. We study the convergence of GEV (Generalized Extreme Value and GP (Generalized Pareto shape parameter estimates to the theoretical value, which is expressed in terms of the partial information dimensions of the attractor. We consider a two-layer quasi-geostrophic atmospheric model of the mid-latitudes, adopt two levels of forcing, and analyse the extremes of different types of physical observables (local energy, zonally averaged energy, and globally averaged energy. We find good agreement in the shape parameter estimates with the theory only in the case of more intense forcing, corresponding to a strong chaotic behaviour, for some observables (the local energy at every latitude. Due to the limited (though very large data size and to the presence of serial correlations, it is difficult to obtain robust statistics of extremes in the case of the other observables. In the case of weak forcing, which leads to weaker chaotic conditions with regime behaviour, we find, unsurprisingly, worse agreement with the theory developed for Axiom A flows.

  17. The formation of snow streamers in the turbulent atmosphere boundary layer

    Science.gov (United States)

    Huang, Ning; Wang, Zheng-Shi

    2016-12-01

    The drifting snow in the turbulent atmosphere boundary layer is an important type of aeolian multi-phase flow. Current theoretical and numerical studies of drifting snow mostly consider the flow field as steady wind velocity. Whereas, little is known about the effects of turbulent wind structures on saltating snow particles. In this paper, a 3-D drifting snow model based on Large Eddy Simulation is established, in which the trajectory of every snow grain is calculated and the coupling effect between wind field and snow particles is considered. The results indicate that the saltating snow particles are re-organized by the suction effect of high-speed rotating vortexes, which results in the local convergence of particle concentration, known as snow streamers. The turbulent wind leads to the spatial non-uniform of snow particles lifted by aerodynamic entrainment, but this does not affect the formation of snow streamers. Whereas the stochastic grain-bed interactions make a great contribution to the final shapes of snow streamers. Generally, snow streamers display a characteristic length about 0.5 m and a characteristic width of approximately 0.16 m, and their characteristic sizes are not sensitive to the wind speed. Compared to the typical sand streamer, snow streamer is slightly narrower and the occurrence of other complex streamer patterns is later than that of sand streamers due to the better follow performance of snow grains with air flow.

  18. Validation of the simpleFoam (RANS solver for the atmospheric boundary layer in complex terrain

    Directory of Open Access Journals (Sweden)

    Peralta C.

    2014-01-01

    Full Text Available We validate the simpleFoam (RANS solver in OpenFOAM (version 2.1.1 for simulating neutral atmospheric boundary layer flows in complex terrain. Initial and boundary conditions are given using Richards and Hoxey proposal [1]. In order to obtain stable simulation of the ABL, modified wall functions are used to set the near-wall boundary conditions, following Blocken et al remedial measures [2]. A structured grid is generated with the new library terrainBlockMesher [3,4], based on OpenFOAM's blockMesh native mesher. The new tool is capable of adding orographic features and the forest canopy. Additionally, the mesh can be refined in regions with complex orography. We study both the classical benchmark case of Askervein hill [5] and the more recent Bolund island data set [6]. Our purpose is two-folded: to validate the performance of OpenFOAM steady state solvers, and the suitability of the new meshing tool to generate high quality structured meshes, which will be used in the future for performing more computationally intensive LES simulations in complex terrain.

  19. Evaluation of Low-Cost Multi-Hole Probes for Atmospheric Boundary Layer Investigation

    Science.gov (United States)

    Azartash-Namin, Solmoz; Jacob, Jamey; Canter, Caleb; Bailey, Sean; Cloud-Map Team

    2017-11-01

    Low-cost multi-hole probes (MHPs) for atmospheric boundary layer (ABL) studies are investigated. Probes are designed using rapid prototyping methods through FDM, SLA, and other techniques for evaluation through calibration testing and comparison with probes manufactured through more traditional methods. Each probe is tested and validated to develop calibration curves and PIV is used to examine the flow field around the probe during both attached and separated conditions. Standard non-nulling calibration and data reduction methods were used showing performance characteristics of each probe. Impact of probe tip geometry and internal duct arrangements are examined. Multiple geometries, including hemispherical and pyramid, as well as multiple sizes are evaluated for both accuracy and sensitivity. Of the two primary geometric designs evaluated, the hemisphere 5HPs produced the most symmetric calibration curves with linearity between +/-25° . Further issues related to optimized probe designs, manufacturing quality consistency, and sensor development are discussed. A custom weather data sensor package has been developed for flight testing in ABL studies and preliminary results are presented. Supported in part by National Science Foundation Award Numbers 1351411 and 1539070.

  20. Simulations of Vertical Axis Wind Turbine Farms in the Atmospheric Boundary Layer

    Science.gov (United States)

    Hezaveh, Seyed Hossein; Bou-Zeid, Elie; Lohry, Mark; Martinelli, Luigi

    2014-11-01

    Wind power is an abundant and clean source of energy that is increasingly being tapped to reduce the environmental footprint of anthropogenic activities. The vertical axis wind turbine (VAWT) technology is now being revisited due to some important advantages over horizontal axis wind turbines (HAWTS) that are particularly important for farms deployed offshore or in complex terrain. In this talk, we will present the implementation and testing of an actuator line model (ALM) for VAWTs in a large eddy simulation (LES) code for the atmospheric boundary layer, with the aim of optimizing large VAWT wind farm configurations. The force coefficients needed for the ALM are here obtained from blade resolving RANS simulations of individual turbines for each configuration. Comparison to various experimental results show that the model can very successfully reproduce observed wake characteristic. The influence of VAWT design parameters such as solidity, height to radius ratio, and tip speed ratio (TSR) on these wake characteristics, particularly the velocity deficit profile, is then investigated.

  1. Interaction Between the Atmospheric Boundary Layer and Wind Energy: From Continental-Scale to Turbine-Scale

    Science.gov (United States)

    St. Martin, Clara Mae

    Wind turbines and groups of wind turbines, or "wind plants", interact with the complex and heterogeneous boundary layer of the atmosphere. We define the boundary layer as the portion of the atmosphere directly influenced by the surface, and this layer exhibits variability on a range of temporal and spatial scales. While early developments in wind energy could ignore some of this variability, recent work demonstrates that improved understanding of atmosphere-turbine interactions leads to the discovery of new ways to approach turbine technology development as well as processes such as performance validation and turbine operations. This interaction with the atmosphere occurs at several spatial and temporal scales from continental-scale to turbine-scale. Understanding atmospheric variability over continental-scales and across plants can facilitate reliance on wind energy as a baseload energy source on the electrical grid. On turbine scales, understanding the atmosphere's contribution to the variability in power production can improve the accuracy of power production estimates as we continue to implement more wind energy onto the grid. Wind speed and directional variability within a plant will affect wind turbine wakes within the plants and among neighboring plants, and a deeper knowledge of these variations can help mitigate effects of wakes and possibly even allow the manipulation of these wakes for increased production. Herein, I present the extent of my PhD work, in which I studied outstanding questions at these scales at the intersections of wind energy and atmospheric science. My work consists of four distinct projects. At the coarsest scales, I analyze the separation between wind plant sites needed for statistical independence in order to reduce variability for grid-integration of wind. At lower wind speeds, periods of unstable and more turbulent conditions produce more power than periods of stable and less turbulent conditions, while at wind speeds closer to

  2. State of adsorption layers of fatty acids on the surfaces of iron, manganese, and copper ferrites

    Science.gov (United States)

    Balmasova, O. V.; Ramazanova, A. G.; Korolev, V. V.

    2012-07-01

    States of adsorbed substances in surface layers arising during the adsorption of oleic, linoleic, and linolenic acids from carbon tetrachloride, heptane, and cyclohexane solutions on the surfaces of iron, manganese, and copper ferrites, are investigated. Adsorption isotherms and two-dimensional state diagrams of surface layers of iron, manganese, and copper ferrites are obtained experimentally. It is shown that the adsorption of fatty acids from solutions in organic solvents proceeds via filling the volume of the ferrites' porous space with adsorption solutions, while the state of ferrite surface layers changes due to the structural rearrangement of adsorption solutions upon an increase in solute concentration.

  3. Stable Boundary Layer Issues

    NARCIS (Netherlands)

    Steeneveld, G.J.

    2012-01-01

    Understanding and prediction of the stable atmospheric boundary layer is a challenging task. Many physical processes are relevant in the stable boundary layer, i.e. turbulence, radiation, land surface coupling, orographic turbulent and gravity wave drag, and land surface heterogeneity. The

  4. Surface modification of polylactic acid (PLA) by air atmospheric plasma treatment

    OpenAIRE

    Jordá Vilaplana, Amparo; Fombuena Borrás, Vicent; García García, Daniel; Samper Madrigal, María Dolores; Sánchez Nacher, Lourdes

    2014-01-01

    The main objective of this experimental study is the validation of the technique of atmospheric plasma with the aim of improving the surface energy of the polylactic acid (PLA) for further adhesion uses. The wettability of PLA has been improved with the application of an atmospheric plasma surface treatment. This method provides good adhesion properties with the optimizing the process parameters in terms of the nozzle substrate distance and sample advance rate. In order to achieve that goal, ...

  5. SAFARI 2000 Surface Atmospheric Radiative Transfer (SMART), Dry Season 2000

    Data.gov (United States)

    National Aeronautics and Space Administration — Surface-sensing Measurements for Radiative Transfer (SMART) and Chemical, Optical, and Microphysical Measurements of In-situ Troposphere (COMMIT) consist of a suite...

  6. Anticorrosive behaviour of lumefantrine hydrophobic layer on mild steel surface

    Directory of Open Access Journals (Sweden)

    Pavithra M. Krishnegowda

    2016-06-01

    Full Text Available The surface modification of mild steel was achieved by chemical treatment in lumefantrine (LF solution. The surface morphology and wettability of modified surface was analysed by 3D profilometer and contact angle goniometer. The corrosion inhibition performance of modified mild steel surface in 1.0 M HCl solution was investigated by potentiodynamic polarization and electrochemical impedance techniques.Electroche­mical measurements illustrate that the corrosion of mild steel in acidic chloride medium get substantially reduced by introducing LF film on its surface (94 % efficiency. Quantum chemical parameters were evaluated by ab initio method and they confer appropriate theoretical support to the experimental findings.

  7. Dunes on Titan: A major landform revealing atmospheric and surface processes

    Science.gov (United States)

    Radebaugh, Jani; Lorenz, Ralph; Arnold, Karl; Savage, Christopher; Williams, Brigitte

    The surface of Saturn’s moon Titan is covered in features that herald an active atmosphere and perhaps interior, such as dunes, rivers, lakes, mountain chains, and possible cryovolcanoes. Examining the geomorphology of these features helps us approach an understanding of the processes that are occurring or have occurred in the atmosphere and subsurface. A major landform on Titan is dunes, composed of organic sands ultimately derived from upper atmospheric processing of methane, subsequently perhaps eroded from organic sedimentary layers by methane rainfall and fluvial flow. Dunes fill vast fields, termed sand seas, similar to those observed in the Sahara, Namibia, and the Arabian peninsula. The equatorial region of Titan contains five separate sand seas as observed by the Cassini Synthetic Aperture Radar (SAR), Imaging Science Subsystem (ISS) and Visual and Infrared Mapping Spectrometer (VIMS) instruments. Together these sand seas cover 14 percent of the surface, totaling 12 million km2, and each have areas on the scale of the Saharan Great Sand Sea. They adjoin each other through sediment pathways around landmasses, and these large-scale connections as well as individual dune interactions with topography indicate a general transport of sediment from west to east. Measurements of dune height, width and spacing in Cassini SAR images reveal all of Titan’s thousands of linear dunes are of the same population. This indicates there was general uniformity in the wind and sediment supply conditions that led to the current dune forms. Variations in the parametric values result from deviations from these conditions, in some locations where elevated terrains have deflected winds. Dunes and sand seas are among the stratigraphically youngest features on Titan, showing little evidence of being affected by impact cratering or fluvial flow. However, individual dunes may be relatively stable, as the reorganization time scale for these features on Earth can be tens to hundreds

  8. Sensitivity of Turbine-Height Wind Speeds to Parameters in Planetary Boundary-Layer and Surface-Layer Schemes in the Weather Research and Forecasting Model

    Science.gov (United States)

    Yang, Ben; Qian, Yun; Berg, Larry K.; Ma, Po-Lun; Wharton, Sonia; Bulaevskaya, Vera; Yan, Huiping; Hou, Zhangshuan; Shaw, William J.

    2017-01-01

    We evaluate the sensitivity of simulated turbine-height wind speeds to 26 parameters within the Mellor-Yamada-Nakanishi-Niino (MYNN) planetary boundary-layer scheme and MM5 surface-layer scheme of the Weather Research and Forecasting model over an area of complex terrain. An efficient sampling algorithm and generalized linear model are used to explore the multiple-dimensional parameter space and quantify the parametric sensitivity of simulated turbine-height wind speeds. The results indicate that most of the variability in the ensemble simulations is due to parameters related to the dissipation of turbulent kinetic energy (TKE), Prandtl number, turbulent length scales, surface roughness, and the von Kármán constant. The parameter associated with the TKE dissipation rate is found to be most important, and a larger dissipation rate produces larger hub-height wind speeds. A larger Prandtl number results in smaller nighttime wind speeds. Increasing surface roughness reduces the frequencies of both extremely weak and strong airflows, implying a reduction in the variability of wind speed. All of the above parameters significantly affect the vertical profiles of wind speed and the magnitude of wind shear. The relative contributions of individual parameters are found to be dependent on both the terrain slope and atmospheric stability.

  9. Sensitivity of Turbine-Height Wind Speeds to Parameters in Planetary Boundary-Layer and Surface-Layer Schemes in the Weather Research and Forecasting Model

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ben; Qian, Yun; Berg, Larry K.; Ma, Po-Lun; Wharton, Sonia; Bulaevskaya, Vera; Yan, Huiping; Hou, Zhangshuan; Shaw, William J.

    2016-07-21

    We evaluate the sensitivity of simulated turbine-height winds to 26 parameters applied in a planetary boundary layer (PBL) scheme and a surface layer scheme of the Weather Research and Forecasting (WRF) model over an area of complex terrain during the Columbia Basin Wind Energy Study. An efficient sampling algorithm and a generalized linear model are used to explore the multiple-dimensional parameter space and quantify the parametric sensitivity of modeled turbine-height winds. The results indicate that most of the variability in the ensemble simulations is contributed by parameters related to the dissipation of the turbulence kinetic energy (TKE), Prandtl number, turbulence length scales, surface roughness, and the von Kármán constant. The relative contributions of individual parameters are found to be dependent on both the terrain slope and atmospheric stability. The parameter associated with the TKE dissipation rate is found to be the most important one, and a larger dissipation rate can produce larger hub-height winds. A larger Prandtl number results in weaker nighttime winds. Increasing surface roughness reduces the frequencies of both extremely weak and strong winds, implying a reduction in the variability of the wind speed. All of the above parameters can significantly affect the vertical profiles of wind speed, the altitude of the low-level jet and the magnitude of the wind shear strength. The wind direction is found to be modulated by the same subset of influential parameters. Remainder of abstract is in attachment.

  10. Immersed Boundary Methods for High-Resolution Simulation of Atmospheric Boundary-Layer Flow Over Complex Terrain

    Energy Technology Data Exchange (ETDEWEB)

    Lundquist, K A [Univ. of California, Berkeley, CA (United States)

    2010-05-12

    use of flux (non-zero) boundary conditions. This anabatic flow set-up is further coupled to atmospheric physics parameterizations, which calculate surface fluxes, demonstrating that the IBM can be coupled to various land-surface parameterizations in atmospheric models. Additionally, the IB method is extended to three dimensions, using both trilinear and inverse distance weighted interpolations. Results are presented for geostrophic flow over a three-dimensional hill. It is found that while the IB method using trilinear interpolation works well for simple three-dimensional geometries, a more flexible and robust method is needed for extremely complex geometries, as found in three-dimensional urban environments. A second, more flexible, immersed boundary method is devised using inverse distance weighting, and results are compared to the first IBM approach. Additionally, the functionality to nest a domain with resolved complex geometry inside of a parent domain without resolved complex geometry is described. The new IBM approach is used to model urban terrain from Oklahoma City in a one-way nested configuration, where lateral boundary conditions are provided by the parent domain. Finally, the IB method is extended to include wall model parameterizations for rough surfaces. Two possible implementations are presented, one which uses the log law to reconstruct velocities exterior to the solid domain, and one which reconstructs shear stress at the immersed boundary, rather than velocity. These methods are tested on the three-dimensional canonical case of neutral atmospheric boundary layer flow over flat terrain.

  11. Modifying of Cotton Fabric Surface with Nano-ZnO Multilayer Films by Layer-by-Layer Deposition Method

    Directory of Open Access Journals (Sweden)

    Sarıışık Merih

    2010-01-01

    Full Text Available Abstract ZnO nanoparticle–based multilayer nanocomposite films were fabricated on cationized woven cotton fabrics via layer-by-layer molecular self-assembly technique. For cationic surface charge, cotton fabrics were pretreated with 2,3-epoxypropyltrimethylammonium chloride (EP3MAC by pad-batch method. XPS and SEM were used to examine the deposited nano-ZnO multilayer films on the cotton fabrics. The nano-ZnO films deposited on cotton fabrics exhibited excellent antimicrobial activity against Staphylococcus aureus bacteria. The results also showed that the coated fabrics with nano-ZnO multilayer films enhanced the protection of cotton fabrics from UV radiation. Physical tests (tensile strength of weft and warp yarns, air permeability and whiteness values were performed on the fabrics before and after the treatment with ZnO nanoparticles to evaluate the effect of layer-by-layer (LbL process on cotton fabrics properties.

  12. The effect of boundary layer and surface characteristics on non-Gaussian turbulent fluctuations of temperature

    Science.gov (United States)

    Graf, A.; Schüttemeyer, D.; Geiß, H.; Knaps, A.; Möllmann-Coers, M.; Schween, J. H.; Kollet, S.; Neininger, B.; Herbst, M.; Vereecken, H.

    2009-04-01

    We use simultaneously measured near-ground micrometeorological and boundary layer data to examine the relation between the probability density function (PDF) of a turbulent scalar such as temperature and its vertical profile. Turbulent temperature time series of 10 to 20 s-1 resolution are taken from eddy covariance stations measuring at 1.45 to 120 m above ground level, and vertical profiles of potential temperature were composed of tower and aircraft measurements. The relation between skewness and kurtosis of the turbulent near-ground data was evaluated using the Pearson system of distributions, and indicates that a part of their non-Gaussianity is due to the existence of a well-defined lower limit to fluctuations. To a lesser extend, an upper limit is also indicated. During unstable situations, the lower limit could be related to the minimum of potential temperature available in the boundary layer. During stable situations, it was related to the effective surface temperature at the measurement site estimated from outgoing longwave radiation. The upper limit could be related with considerably less rigidity and a systematic underestimation, which we attribute to well mixing by small-scale turbulence, to the surface temperature during unstable situations. Two types of theoretical PDFs are compared to the turbulent histograms. The first type, the beta distribution was empirically chosen from classical statistics based on matching the first four sample moments and has already been used to empirically model scalar concentrations in plumes. The second type was theoretically derived from simplified assumptions on atmospheric dispersion. Both support the assumption that turbulent scalar PDFs in horizontally homogeneous conditions have finite tails.

  13. Surface layering at the mercury-electrolyte interface.

    Science.gov (United States)

    Elsen, A; Murphy, B M; Ocko, B M; Tamam, L; Deutsch, M; Kuzmenko, I; Magnussen, O M

    2010-03-12

    X-ray reflectometry reveals atomic layering at a liquid-liquid interface--mercury in a 0.01 M NaF solution. The interface width exceeds capillary wave theory predictions and displays an anomalous dependence on the voltage applied across it, displaying a minimum positive of the potential of zero charge. The latter is explained by electrocapillary effects and an additional intrinsic broadening of the interface profile, tentatively assigned to polarization of the conduction electrons due to the electric field of the electrochemical double layer at the interface.

  14. Surface Layering at the Mercury-Electrolyte Interface

    Energy Technology Data Exchange (ETDEWEB)

    Ocko, B.M.; Elsen, A.; Murphy, B.M.; Tamam, L.; Deutsch, M.; Kuzmenko, I.; Magnussen, O.M.

    2010-03-12

    X-ray reflectometry reveals atomic layering at a liquid-liquid interface--mercury in a 0.01 M NaF solution. The interface width exceeds capillary wave theory predictions and displays an anomalous dependence on the voltage applied across it, displaying a minimum positive of the potential of zero charge. The latter is explained by electrocapillary effects and an additional intrinsic broadening of the interface profile, tentatively assigned to polarization of the conduction electrons due to the electric field of the electrochemical double layer at the interface.

  15. Influence of stripping and cooling atmospheres on surface properties and corrosion of zinc galvanizing coatings

    Science.gov (United States)

    Yasakau, K. A.; Giner, I.; Vree, C.; Ozcan, O.; Grothe, R.; Oliveira, A.; Grundmeier, G.; Ferreira, M. G. S.; Zheludkevich, M. L.

    2016-12-01

    In this work the influence of stripping/cooling atmospheres used after withdrawal of steel sheet from Zn or Zn-alloy melt on surface properties of Zn (Z) and Zn-Al-Mg (ZM) hot-dip galvanizing coatings has been studied. The aim was to understand how the atmosphere (composed by nitrogen (N2) or air) affects adhesion strength to model adhesive and corrosive behaviour of the galvanized substrates. It was shown that the surface chemical composition and Volta potential of the galvanizing coatings prepared under the air or nitrogen atmosphere are strongly influenced by the atmosphere. The surface chemistry Z and ZM surfaces prepared under N2 contained a higher content of metal atoms and a richer hydroxide density than the specimens prepared under air atmosphere as assessed by X-ray photoelectron spectroscopy (XPS). The induced differences on the microstructure of the galvanized coatings played a key role on the local corrosion induced defects as observed by means of in situ Atomic force microscopy (AFM). Peel force tests performed on the substrates coated by model adhesive films indicate a higher adhesive strength to the surfaces prepared under nitrogen atmosphere. The obtained results have been discussed in terms of the microstructure and surface chemical composition of the galvanizing coatings.

  16. Amendment to "Analytical Solution for the Convectively-Mixed Atmospheric Boundary Layer": Inclusion of Subsidence

    NARCIS (Netherlands)

    Ouwersloot, H.G.; Arellano, de J.V.G.

    2013-01-01

    In Ouwersloot and Vila-Guerau de Arellano (Boundary-Layer Meteorol. doi: 10. 1007/s10546-013-9816-z, 2013, this issue), the analytical solutions for the boundary-layer height and scalar evolutions are derived for the convective boundary layer, based on the prognostic equations of mixed-layer slab

  17. Anticoagulant surface modification of titanium via layer-by-layer assembly of collagen and sulfated chitosan multilayers.

    Science.gov (United States)

    Li, Quan-Li; Huang, Nan; Chen, Jialong; Wan, Guojiang; Zhao, Ansa; Chen, Junying; Wang, Jin; Yang, Ping; Leng, Yongxiang

    2009-06-01

    Extracellular matrix (ECM)-like biomimetic surface modification of cardiovascular implants is a promising method for improving hemocompatibility. In the present work, collagen (Col) and sulfated chitosan (SCS) multilayers were coated on pure titanium using a layer-by-layer (LBL) self-assembly technique. The Col-SCS multilayer growth was carried out by first depositing a single layer of positively charged poly-L-lysine (PLL) on the NaOH-treated titanium substrate (negatively charged surface), followed by alternate deposition of negatively charged SCS and positively charged Col, and terminated by an outermost layer of SCS. Platelet adhesion in vitro, partial activated thromboplastin time (APTT) and prothrombin time (PT) assays were used to evaluate the hemocompatibility of the Col-SCS multilayer coated titanium. The multilayer processed surfaces displayed reduced platelet adhesion and activation, and prolonged clotting time of APTT and PT compared with untreated titanium. Thus, the approach described here may provide a basis for the preparation of modified titanium surfaces for application in cardiovascular implants. 2008 Wiley Periodicals, Inc.

  18. Surface modification of the titanium implant using TEA CO 2 laser pulses in controllable gas atmospheres - Comparative study

    Science.gov (United States)

    Ciganovic, J.; Stasic, J.; Gakovic, B.; Momcilovic, M.; Milovanovic, D.; Bokorov, M.; Trtica, M.

    2012-01-01

    Interaction of a TEA CO2 laser, operating at 10.6 μm wavelength and pulse duration of 100 ns (FWHM), with a titanium implant in various gas atmospheres was studied. The Ti implant surface modification was typically studied at the moderate laser beam energy density/fluence of 28 J/cm2 in the surrounding of air, N2, O2 or He. The energy absorbed from the TEA CO2 laser beam is partially converted to thermal energy, which generates a series of effects, such as melting, vaporization of the molten material, shock waves, etc. The following titanium implant surface changes and phenomena were observed, depending on the gas used: (i) creation of cone-like surface structures in the atmospheres of air, N2 and O2, and dominant micro-holes/pores in He ambient; (ii) hydrodynamic features, most prominent in air; (iii) formation of titanium nitride and titanium oxide layers, and (iv) occurrence of plasma in front of the implant. It can be concluded from this study that the reported laser fluence and gas ambiences can effectively be applied for enhancing the titanium implant roughness and creation of titanium oxides and nitrides on the strictly localized surface area. The appearance of plasma in front of the implants indicates relatively high temperatures created above the surface. This offers a sterilizing effect, facilitating contaminant-free conditions.

  19. Effect of post weld heat treatment on wear resistance of hot forging cast steel die coated with surfacing layer

    Directory of Open Access Journals (Sweden)

    Xu Wujiao

    2015-01-01

    Full Text Available The wear resistance capability of die surfacing layer under different Post Weld Heat Treatments (PWHT was analysed by Finite Element Method (FEM simulation and experiments. Taking the hot forging process of crankshaft as example, a wear model of hot forging die coated with surfacing layer was established by the software DEFORM-3D. The simulation results indicate that the wear resistance capability of the die surfacing layer is optimal when tempering temperature and holding time are 550 ∘C and 4h respectively. To verify the wear calculation result, 16 groups of different PWHT orthogonal wear tests were performed under atmospheric condition at 400 ∘C. The wear test result shows a good agreement with the FEM simulation result. SEM observation of the wear debris shows that oxidative wear plays a dominant role in 400 ∘C among 16 specimens. Furthermore, when tempering temperature and holding time are 550 ∘C and 4h respectively, the alloy carbide dispersively distributes in the metallographic structure, which can improve the wear resistance of the surfacing.

  20. The Data Base for the May 1979 Marine Surface Layer Micrometeorological Experiment at San Nicolas Island, California.

    Science.gov (United States)

    1982-05-07

    NOTES 19. KEY WORDS (Continue on reverse aide If neceeeary and Identify by block nuniber) Marine atmospheric surface layer Air-sea interaction Marine...ENGINEERING; UNITS: AIR TEMP.I WINS SiPEEDI DEW POINTI TtMPUTIRUTI WIND DIR.) LR .FPRES. I VKYR ND.) BU(.R aT TEMP ( lEAN AIR TEMP (Clis trse(Clus l~ i-2...IRM FUX FIUX FLUX PLUX FLUX RATIO VELOCITY HUMIDITY TEMP. LERGTM rOEF. 78% 76% 24% 4% 53% R% 1% 5?z 12% 8 55% 42% 31x ENS an O tA Bim 209 MA4RINE

  1. Influence of stripping and cooling atmospheres on surface properties and corrosion of zinc galvanizing coatings

    Energy Technology Data Exchange (ETDEWEB)

    Yasakau, K.A., E-mail: kyasakau@ua.pt [Department of Materials and Ceramic Engineering, CICECO—Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro (Portugal); Giner, I. [Universität Paderborn, Fakultät NW—Department Chemie, Technische und Makromolekulare Chemie, Warburger Strasse 100, D-33098 Paderborn (Germany); Vree, C. [Salzgitter Mannesmann Forschung, GmbH Division Surface Technology, Eisenhüttenstrasse 99, 38239 Salzgitter (Germany); Ozcan, O.; Grothe, R. [Universität Paderborn, Fakultät NW—Department Chemie, Technische und Makromolekulare Chemie, Warburger Strasse 100, D-33098 Paderborn (Germany); Oliveira, A. [Department of Materials and Ceramic Engineering, CICECO—Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro (Portugal); Grundmeier, G. [Universität Paderborn, Fakultät NW—Department Chemie, Technische und Makromolekulare Chemie, Warburger Strasse 100, D-33098 Paderborn (Germany); Ferreira, M.G.S. [Department of Materials and Ceramic Engineering, CICECO—Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro (Portugal); Zheludkevich, M.L. [Department of Materials and Ceramic Engineering, CICECO—Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro (Portugal); Department of Corrosion and Surface Technology, Institute of Materials Research Helmholtz-Zentrum Geesthacht, Max-Planck Str. 1, 21502 Geesthacht (Germany)

    2016-12-15

    Highlights: • Stripping/cooling atmosphere affects surfaces chemical composition of Zn and Zn-Al-Mg galvanized coatings. • Higher peel forces of model adhesive films were obtained on zinc alloys samples prepared under nitrogen atmosphere. • Localized corrosion attack originates at grain boundaries on Zn galvanized coating. • Visible dissolution of MgZn{sub 2} phase was observed by in situ AFM only at binary eutectics and not at ternary ones. - Abstract: In this work the influence of stripping/cooling atmospheres used after withdrawal of steel sheet from Zn or Zn-alloy melt on surface properties of Zn (Z) and Zn-Al-Mg (ZM) hot-dip galvanizing coatings has been studied. The aim was to understand how the atmosphere (composed by nitrogen (N{sub 2}) or air) affects adhesion strength to model adhesive and corrosive behaviour of the galvanized substrates. It was shown that the surface chemical composition and Volta potential of the galvanizing coatings prepared under the air or nitrogen atmosphere are strongly influenced by the atmosphere. The surface chemistry Z and ZM surfaces prepared under N{sub 2} contained a higher content of metal atoms and a richer hydroxide density than the specimens prepared under air atmosphere as assessed by X-ray photoelectron spectroscopy (XPS). The induced differences on the microstructure of the galvanized coatings played a key role on the local corrosion induced defects as observed by means of in situ Atomic force microscopy (AFM). Peel force tests performed on the substrates coated by model adhesive films indicate a higher adhesive strength to the surfaces prepared under nitrogen atmosphere. The obtained results have been discussed in terms of the microstructure and surface chemical composition of the galvanizing coatings.

  2. Competing Atmospheric and Surface-Driven Impacts of Absorbing Aerosols on the East Asian Summer Monsoon

    Science.gov (United States)

    Persad, G.; Paynter, D.; Ming, Y.; Ramaswamy, V.

    2015-12-01

    Absorbing aerosols, by attenuating shortwave radiation within the atmosphere and reemitting it as longwave radiation, redistribute energy both vertically within the surface-atmosphere column and horizontally between polluted and unpolluted regions. East Asia has the largest concentrations of anthropogenic absorbing aerosols globally, and these, along with the region's scattering aerosols, have both reduced the amount of solar radiation reaching the Earth's surface regionally ("solar dimming") and increased shortwave absorption within the atmosphere, particularly during the peak months of the East Asian Summer Monsoon (EASM). We here analyze how atmospheric absorption and surface solar dimming compete in driving the response of EASM circulation to anthropogenic absorbing aerosols, which dominates, and why—issues of particular importance for predicting how the EASM will respond to projected changes in absorbing and scattering aerosol emissions in the future. We probe these questions in a state-of-the-art general circulation model (GCM) using a combination of realistic and idealized aerosol perturbations that allow us to analyze the relative influence of absorbing aerosols' atmospheric and surface-driven impacts on EASM circulation. In combination, our results make clear that, although absorption-driven dimming has a less detrimental effect on EASM circulation than purely scattering-driven dimming, aerosol absorption is still a net impairment to EASM strength when both its atmospheric and surface effects are considered. Because atmospheric heating is not efficiently conveyed to the surface, the surface dimming and associated cooling from even a pure absorber is sufficient to counteract its atmospheric heating, resulting in a net reduction in EASM strength. These findings elevate the current understanding of the impacts of aerosol absorption on the EASM, improving our ability to diagnose EASM responses to current and future regional changes in aerosol emissions.

  3. The nanostructure and microstructure of SiC surface layers deposited by MWCVD and ECRCVD

    Science.gov (United States)

    Dul, K.; Jonas, S.; Handke, B.

    2017-12-01

    Scanning electron microscopy (SEM) and Atomic force microscopy (AFM) have been used to investigate ex-situ the surface topography of SiC layers deposited on Si(100) by Microwave Chemical Vapour Deposition (MWCVD) -S1,S2 layers and Electron Cyclotron Resonance Chemical Vapor Deposition (ECRCVD) - layers S3,S4, using silane, methane, and hydrogen. The effects of sample temperature and gas flow on the nanostructure and microstructure have been investigated. The nanostructure was described by three-dimensional surface roughness analysis based on digital image processing, which gives a tool to quantify different aspects of surface features. A total of 13 different numerical parameters used to describe the surface topography were used. The scanning electron image (SEM) of the microstructure of layers S1, S2, and S4 was similar, however, layer S3 was completely different; appearing like grains. Nonetheless, it can be seen that no grain boundary structure is present in the AFM images.

  4. Etching Processes of Polytetrafluoroethylene Surfaces Exposed to He and He-O2 Atmospheric Post-discharges

    CERN Document Server

    Hubert, J; Vandencasteele, Nicolas; Desbief, Simon; Lazzaroni, Roberto; Reniers, F

    2016-01-01

    A comparative study of polytetrafluoroethylene (PTFE) surfaces treated by the post-discharge of He and He-O2 plasmas at atmospheric pressure is presented. The characterization of treated PTFE surfaces and the species involved in the surface modification are related. In pure He plasmas, no significant change of the surface has been observed by X-ray photoelectron spectroscopy (XPS), dynamic water contact angles (dWCA) and atomic force microscopy (AFM), in spite of important mass losses recorded. According to these observations, a layer-by-layer physical etching without any preferential orientation is proposed, where the highly energetic helium metastables are the main species responsible for the scission of --(CF2)n-- chains. In He--O 2 plasmas, as the density of helium metastables decreases as a function of the oxygen flow rate, the treatment leads to fewer species ejected from the PTFE surfaces (in agreement with mass loss measurements and the detection of fluorinated species onto aluminum foil). However, th...

  5. Cleaning of niobium surface by plasma of diffuse discharge at atmospheric pressure

    Science.gov (United States)

    Tarasenko, V. F.; Erofeev, M. V.; Shulepov, M. A.; Ripenko, V. S.

    2017-07-01

    Elements composition of niobium surface before and after plasma treatment by runaway electron preionized diffuse discharge was investigated in atmospheric pressure nitrogen flow by means of an Auger electron spectroscopy. Surface characterizations obtained from Auger spectra show that plasma treatment by diffuse discharge after exposure of 120000 pulses provides ultrafine surface cleaning from carbon contamination. Moreover, the surface free energy of the treated specimens increased up to 3 times, that improve its adhesion property.

  6. Application of remotely piloted aircraft systems in observing the atmospheric boundary layer over Antarctic sea ice in winter

    Directory of Open Access Journals (Sweden)

    Marius O. Jonassen

    2015-10-01

    Full Text Available The main aim of this paper is to explore the potential of combining measurements from fixed- and rotary-wing remotely piloted aircraft systems (RPAS to complement data sets from radio soundings as well as ship and sea-ice-based instrumentation for atmospheric boundary layer (ABL profiling. This study represents a proof-of-concept of RPAS observations in the Antarctic sea-ice zone. We present first results from the RV Polarstern Antarctic winter expedition in the Weddell Sea in June–August 2013, during which three RPAS were operated to measure temperature, humidity and wind; a fixed-wing small unmanned meteorological observer (SUMO, a fixed-wing meteorological mini-aerial vehicle, and an advanced mission and operation research quadcopter. A total of 86 RPAS flights showed a strongly varying ABL structure ranging from slightly unstable temperature stratification near the surface to conditions with strong surface-based temperature inversions. The RPAS observations supplement the regular upper air soundings and standard meteorological measurements made during the campaign. The SUMO and quadcopter temperature profiles agree very well and, excluding cases with strong temperature inversions, 70% of the variance in the difference between the SUMO and quadcopter temperature profiles can be explained by natural, temporal, temperature fluctuations. Strong temperature inversions cause the largest differences, which are induced by SUMO's high climb rates and slow sensor response. Under such conditions, the quadcopter, with its slower climb rate and faster sensor, is very useful in obtaining accurate temperature profiles in the lowest 100 m above the sea ice.

  7. Atmospheric Transference of the Toxic Burden of Atmosphere-Surface Exchangeable Pollutants to the Great Lakes Region

    Science.gov (United States)

    Kumar, A.; Perlinger, J. A.; Giang, A.; Zhang, H.; Selin, N. E.; Wu, S.

    2016-12-01

    Toxic pollutants that share certain chemical properties undergo repeated emission and deposition between Earth's surfaces and the atmosphere. Following their emission through anthropogenic activities, they are transported locally, regionally or globally through the atmosphere, are deposited, and impact local ecosystems, in some cases as a result of bioaccumulation in food webs. We call them atmosphere-surface exchangeable pollutants or "ASEPs", wherein this group is comprised of thousands of chemicals. We are studying potential future contamination in the Great Lakes region by modeling scenarios of the future for three compounds/compound classes, mercury, polychlorinated biphenyl compounds, and polycyclic aromatic hydrocarbons. In this presentation we focus on mercury and future scenarios of contamination of the Great Lake region. The atmospheric transport of mercury under specific scenarios will be discussed. The global 3-D chemical transport model GEOS-Chem has been applied to estimate future atmospheric concentrations and deposition rates of mercury in the Great Lakes region for selected future scenarios of emissions and climate. We find that, assuming no changes in climate, annual mean net deposition flux of mercury to the Great Lakes Region may increase by approximately 50% over 2005 levels by 2050, without global or regional policies addressing mercury, air pollution, and climate. In contrast, we project that the combination of global and North American action on mercury could lead to a 21% reduction in deposition from 2005 levels by 2050. US action alone results in a projected 18% reduction over 2005 levels by 2050. We also find that, assuming no changes in anthropogenic emissions, climate change and biomass burning emissions would, respectively, cause annual mean net deposition flux of mercury to the Great Lakes Region to increase by approximately 5% and decrease by approximately 2% over 2000 levels by 2050.

  8. Atmospheres – Through Projections on a Living Surface

    DEFF Research Database (Denmark)

    Steijn, Arthur

    2013-01-01

    In this paper I present my on-going work on a design model aimed at the design of motion graphics applied in spatial contexts.1 In this work I integrate various design elements and components as e.g. line and shape, tone and colour, time and timing, rhythm and movement with conceptualizations...... of space, liveness and atmosphere. With the development of this model I wish to contribute to the on-going development of the use of video projections and motion graphics as important visual, spatial and narrative elements within the field of spatial experience design, e.g. in performance, exhibition...... design and events. The model is being designed with two purposes in mind. One is a tool for analyzing empirical examples or cases where video projections are used in spatial experience design. The second is to create a tool that can be useful in actual design processes. In this paper I describe a case...

  9. The Surface and Atmosphere of Venus: Evolution and Present State

    Science.gov (United States)

    Grinspoon, David

    Most models of atmospheric evolution start with the reasonable but unverified assumption that the original atmospheric inventories of Venus and Earth were similar. Although the two planets have similar overall abundances of nitrogen and carbon, the present day water inventory of Venus is lower than that of Earth by a factor of 105. The original water abundance of Venus is highly unconstrained. The high D/H ratio observed, 2.5 ×10- 2 or ≈ 150 times terrestrial (Donahue et al. 1997) has been cited as evidence of a large primordial water endowment (Donahue et al. 1982). Yet, given the likelihood of geologically recent water sources and the large uncertainty in the modern and past hydrogen and deuterium escape fluxes, the large D/H may not reflect the primordial water abundance but rather may result from the history of escape and resupply in the most recent ≈ 109 years of planetary evolution (Donahue et al. 1997, Grinspoon 1993, 1997). Thus, at present the best arguments for a sizable early Venusian water endowment remain dependent on models of planet formation and early volatile delivery. Most models of water delivery to early Earth involve impact processes that would have also supplied Venus with abundant water (Grinspoon 1987, Ip et al. 1998, Morbidelli et al. 2000). Stochastic processes could have created large inequities in original volatile inventory among neighboring planets (Morbidelli et al. 2000). However, given the great similarity in bulk densities and their close proximity in the Solar System the best assumption at present is that Venus and Earth started with similar water abundances.

  10. Sputtering layers of different materials on tungsten surface by light ions of medium energy bombardment

    Science.gov (United States)

    Manukhin, V. V.

    2017-11-01

    There is an analytical formula allows to calculate the sputtering yields of heterogonous solid targets with light ions, based on the model of sputtering layered surfaces with light ions. Of particular interest is the sputtering of layers of different materials with the tungsten surface, which can be a material for the first wall of fusion reactor. The results of the calculations are in good agreement with the data of computer simulation, and show that the sputtering yields layers with a certain thickness, higher than the sputtering yields of homogeneous material layer targets (“mirror effect”).

  11. Ultrasound enhanced plasma surface modification at atmospheric pressure

    DEFF Research Database (Denmark)

    Kusano, Yukihiro; Singh, Shailendra Vikram; Norrman, Kion

    irradiation, the water contact angle dropped markedly, and tended to decrease furthermore at higher power. The ultrasonic irradiation during the plasma treatment consistently improved the wettability. Oxygen containing polar functional groups were introduced at the surface by the plasma treatment......, and the oxidation was enhanced by the ultrasonic irradiation, indicating that the adhesive property would be improved....

  12. Atmospheric Polarization Imaging with Variable Aerosols, Clouds, and Surface Albedo

    Science.gov (United States)

    2013-07-01

    imager to the Mauna Loa Observatory ( MLO ) on the island of Hawaii to measure clear-sky polarization under the cleanest possible conditions that...polarization. We used satellite imagery to determine the effective surface reflectance for the area surrounding the MLO , and processed clear-sky

  13. Wind-tunnel experiments of turbulent flow over a surface-mounted 2-D block in a thermally-stratified boundary layer

    Science.gov (United States)

    Zhang, Wei; Markfort, Corey; Porté-Agel, Fernando

    2014-11-01

    Turbulent flows over complex surface topography have been of great interest in the atmospheric science and wind engineering communities. The geometry of the topography, surface roughness and temperature characteristics as well as the atmospheric thermal stability play important roles in determining momentum and scalar flux distribution. Studies of turbulent flow over simplified topography models, under neutrally stratified boundary-layer conditions, have provided insights into fluid dynamics. However, atmospheric thermal stability has rarely been considered in laboratory experiments, e.g., wind-tunnel experiments. Series of wind-tunnel experiments of thermally-stratified boundary-layer flow over a surface-mounted 2-D block, in a well-controlled boundary-layer wind tunnel, will be presented. Measurements using high-resolution PIV, x-wire/cold-wire anemometry and surface heat flux sensors were conducted to quantify the turbulent flow properties, including the size of the recirculation zone, coherent vortex structures and the subsequent boundary layer recovery. Results will be shown to address thermal stability effects on momentum and scalar flux distribution in the wake, as well as dominant mechanism of turbulent kinetic energy generation and consumption. The authors gratefully acknowledge funding from the Swiss National Foundation (Grant 200021-132122), the National Science Foundation (Grant ATM-0854766) and NASA (Grant NNG06GE256).

  14. Quantized layer growth at liquid-crystal surfaces

    DEFF Research Database (Denmark)

    Ocko, B. M.; Braslau, A.; Pershan, P. S.

    1986-01-01

    The authors report X-ray reflectivity measurements on the free surface of dodecylcyanobiphenyl (12CB) at the isotropic to smectic-A phase transition. At about 10°C above TIA, smectic-A-like ordering develops at the surface while the bulk phase remains isotropic. The angular dependence of the spec...

  15. Impact of atmospheric boundary layer depth variability and wind reversal on the diurnal variability of aerosol concentration at a valley site

    Energy Technology Data Exchange (ETDEWEB)

    Pal, S., E-mail: sp5hd@Virginia.EDU; Lee, T.R.; Phelps, S.; De Wekker, S.F.J.

    2014-10-15

    The development of the atmospheric boundary layer (ABL) plays a key role in affecting the variability of atmospheric constituents such as aerosols, greenhouse gases, water vapor, and ozone. In general, the concentration of any tracers within the ABL varies due to the changes in the mixing volume (i.e. ABL depth). In this study, we investigate the impact on the near-surface aerosol concentration in a valley site of 1) the boundary layer dilution due to vertical mixing and 2) changes in the wind patterns. We use a data set obtained during a 10-day field campaign in which a number of remote sensing and in-situ instruments were deployed, including a ground-based aerosol lidar system for monitoring of the ABL top height (z{sub i}), a particle counter to determine the number concentration of aerosol particles at eight different size ranges, and tower-based standard meteorological instruments. Results show a clearly visible decreasing trend of the mean daytime z{sub i} from 2900 m AGL (above ground level) to 2200 m AGL during a three-day period which resulted in increased near-surface pollutant concentrations. An inverse relationship exists between the z{sub i} and the fine fraction (0.3–0.7 μm) accumulation mode particles (AMP) on some days due to the dilution effect in a well-mixed ABL. These days are characterized by the absence of daytime upvalley winds and the presence of northwesterly synoptic-driven winds. In contrast, on the days with an onset of an upvalley wind circulation after the morning transition, the wind-driven local transport mechanism outweighs the ABL-dilution effect in determining the variability of AMP concentration. The interplay between the ABL depth evolution and the onset of the upvalley wind during the morning transition period significantly governs the air quality in a valley and could be an important component in the studies of mountain meteorology and air quality. - Highlights: • Role of atmospheric boundary layer depth on particle

  16. Assessing State-of-the-Art Capabilities for Probing the Atmospheric Boundary Layer: The XPIA Field Campaign

    Energy Technology Data Exchange (ETDEWEB)

    Lundquist, Julie K. [Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, and National Renewable Energy Laboratory, Golden, Colorado; Wilczak, James M. [National Oceanic and Atmospheric Administration/Earth System Research Laboratory, Boulder, Colorado; Ashton, Ryan [The University of Texas at Dallas, Dallas, Texas; Bianco, Laura [Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, Colorado; Brewer, W. Alan [National Oceanic and Atmospheric Administration/Earth System Research Laboratory, Boulder, Colorado; Choukulkar, Aditya [National Oceanic and Atmospheric Administration/Earth System Research Laboratory, Boulder, Colorado; Clifton, Andrew [National Renewable Energy Laboratory, Golden, Colorado; Debnath, Mithu [The University of Texas at Dallas, Dallas, Texas; Delgado, Ruben [University of Maryland, Baltimore County, Baltimore, Maryland; Friedrich, Katja [Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, Colorado; Gunter, Scott [Texas Tech University, Lubbock, Texas; Hamidi, Armita [The University of Texas at Dallas, Dallas, Texas; Iungo, Giacomo Valerio [The University of Texas at Dallas, Dallas, Texas; Kaushik, Aleya [Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, Colorado; Kosović, Branko [National Center for Atmospheric Research, Boulder, Colorado; Langan, Patrick [University of Maryland, Baltimore County, Baltimore, Maryland; Lass, Adam [University of Maryland, Baltimore County, Baltimore, Maryland; Lavin, Evan [University of Maryland, Baltimore County, Baltimore, Maryland; Lee, Joseph C. -Y. [Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, Colorado; McCaffrey, Katherine L. [National Oceanic and Atmospheric Administration/Earth System Research Laboratory, Boulder, Colorado; Newsom, Rob K. [Pacific Northwest National Laboratory, Richland, Washington; Noone, David C. [College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, Oregon; Oncley, Steven P. [National Center for Atmospheric Research, Boulder, Colorado; Quelet, Paul T. [Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, Colorado; Sandberg, Scott P. [National Oceanic and Atmospheric Administration/Earth System Research Laboratory, Boulder, Colorado; Schroeder, John L. [Texas Tech University, Lubbock, Texas; Shaw, William J. [Pacific Northwest National Laboratory, Richland, Washington; Sparling, Lynn [University of Maryland, Baltimore County, Baltimore, Maryland; Martin, Clara St. [Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, Colorado; Pe, Alexandra St. [University of Maryland, Baltimore County, Baltimore, Maryland; Strobach, Edward [University of Maryland, Baltimore County, Baltimore, Maryland; Tay, Ken [Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, Colorado; Vanderwende, Brian J. [Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, Colorado; Weickmann, Ann [National Oceanic and Atmospheric Administration/Earth System Research Laboratory, Boulder, Colorado; Wolfe, Daniel [Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, Colorado; Worsnop, Rochelle [Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, Colorado

    2017-02-01

    The synthesis of new measurement technologies with advances in high performance computing provides an unprecedented opportunity to advance our understanding of the atmosphere, particularly with regard to the complex flows in the atmospheric boundary layer. To assess current measurement capabilities for quantifying features of atmospheric flow within wind farms, the U.S. Dept. of Energy sponsored the eXperimental Planetary boundary layer Instrumentation Assessment (XPIA) campaign at the Boulder Atmospheric Observatory (BAO) in spring 2015. Herein, we summarize the XPIA field experiment design, highlight novel approaches to boundary-layer measurements, and quantify measurement uncertainties associated with these experimental methods. Line-of-sight velocities measured by scanning lidars and radars exhibit close agreement with tower measurements, despite differences in measurement volumes. Virtual towers of wind measurements, from multiple lidars or dual radars, also agree well with tower and profiling lidar measurements. Estimates of winds over volumes,conducted with rapid lidar scans, agree with those from scanning radars, enabling assessment of spatial variability. Microwave radiometers provide temperature profiles within and above the boundary layer with approximately the same uncertainty as operational remote sensing measurements. Using a motion platform, we assess motion-compensation algorithms for lidars to be mounted on offshore platforms. Finally, we highlight cases that could be useful for validation of large-eddy simulations or mesoscale numerical weather prediction, providing information on accessing the archived dataset. We conclude that modern remote Lundquist et al. XPIA BAMS Page 4 of 81 sensing systems provide a generational improvement in observational capabilities, enabling resolution of refined processes critical to understanding 61 inhomogeneous boundary-layer flows such as those found in wind farms.

  17. Microporous structure with layered interstitial surface treatment, and method and apparatus for preparation thereof

    Science.gov (United States)

    Koontz, Steven L. (Inventor)

    1994-01-01

    A microporous structure with layered interstitial surface treatments, and method and apparatus for preparation thereof is presented. The structure is prepared by sequentially subjecting a uniformly surface-treated structure to atomic oxygen treatment to remove an outer layer of surface treatment to a generally uniform depth, and then surface treating the so exposed layer with another surface treating agent. The atomic oxygen/surface treatment steps may optionally be repeated, each successive time to a lesser depth, to produce a microporous structure having multilayered surface treatments. The apparatus employs at least one side arm from a main atomic oxygen-containing chamber. The side arm has characteristic relaxation times such that a uniform atomic oxygen dose rate is delivered to a specimen positioned transversely in the side arm spaced from the main gas chamber.

  18. Surface-Engineered Fire Protective Coatings for Fabrics through Sol-Gel and Layer-by-Layer Methods: An Overview

    Directory of Open Access Journals (Sweden)

    Giulio Malucelli

    2016-07-01

    Full Text Available Fabric flammability is a surface-confined phenomenon: in fact, the fabric surface represents the most critical region, through which the mass and heat transfers, responsible for fueling the flame, are controlled and exchanged with the surroundings. More specifically, the heat the fabric surface is exposed to is transferred to the bulk, from which volatile products of thermal degradation diffuse toward the surface and the gas phase, hence feeding the flame. As a consequence, the chemical and physical characteristics of the fabric surface considerably affect the ignition and combustion processes, as the surface influences the flux of combustible volatile products toward the gas phase. In this context, it is possible to significantly modify (and improve the fire performance of textile materials by “simply” tailoring their surface: currently, one of the most effective approaches exploits the deposition of tailored coatings able to slow down the heat and mass transfer phenomena occurring during the fire stages. This paper reviews the current state of the art related to the design of inorganic, hybrid, or organic flame-retardant coatings suitable for the fire protection of different fabric substrates (particularly referring to cotton, polyester, and their blends. More specifically, the use of sol-gel and layer-by-layer (LbL methods is thoroughly discussed; then, some recent examples of flame retardant coatings are presented, showing their potential advances and their current limitations.

  19. Double Compressions of Atmospheric Depth by Geopotential Tendency, Vorticity, and Atmospheric Boundary Layer Affected Abrupt High Particulate Matter Concentrations at a Coastal City for a Yellow Dust Period in October

    Directory of Open Access Journals (Sweden)

    Hyo Choi

    2014-01-01

    Full Text Available Using GRIMM-aerosol sampler, NOAA-HYSPLIT model, and 3D-WRF-3.3 model, the transportation of dusts from Gobi Desert toward Gangneung city, Korea was investigated from 09:00 LST October 27 to 04:00 LST October 28, 2003. Maximum PM10 (PM2.5, PM1 concentration was detected with 3.8 (3.4, 14.1 times higher magnitude than one in non-Yellow Dust period. The combination of dusts transported from the desert under westerly wind with particulate matters and gases from vehicles on the road of the city caused high PM concentrations near the ground surface at 09:00 LST and their maxima at 17:00 LST near sunset with further pollutants from heating boilers in the resident area. Positive geopotential tendency at the 500 hPa level of the city (∂Φ/∂t; m day−1 corresponding to negative vorticity of -4×10-5 sec−1 (-2.5×10-5 sec−1 at 0900 LST (21:00 LST; at night was +83 m day−1 (+30 m day−1 and it caused atmospheric depth between 500 hPa level and the ground surface to be vertically expanded. However, its net reduction to −53 m/12 hrs until 21:00 LST indicated synoptic-scale atmospheric layer to be vertical shrunken, resulting in the increase of PM concentrations at 17:00 LST. Simultaneously, much shallower microscale stable nocturnal surface inversion layer (NSIL than daytime thermal internal boundary layer induced particulate matters to be merged inside the NSIL, resulting in maximum PM concentrations at 17:00 LST.

  20. Shear-induced surface alignment of polymer dispersed liquid crystal microdroplets on the boundary layer

    Science.gov (United States)

    Parmar, D. S.; Singh, J. J.

    1993-01-01

    Polymer dispersed liquid crystal thin films have been deposited on a glass substrate, utilizing the processes of polymerization and solvent evaporation induced phase separation. Liquid crystal microdroplets trapped on the upper surface of the thin film respond to the shear stress due to air or gas flow on the surface layer. Response to an applied step shear stress input on the surface layer has been measured by measuring the time response of the transmitted light intensity. Initial results on the measurements of the light transmission as a function of the air flow differential pressure indicate that these systems offer features suitable for boundary layer and gas flow sensors.