WorldWideScience

Sample records for atmospheric surface layer

  1. Characteristics of the Martian atmosphere surface layer

    Science.gov (United States)

    Clow, G. D.; Haberle, R. M.

    1991-01-01

    Researchers extend elements of various terrestrial boundary layer models to Mars in order to estimate sensible heat, latent heat, and momentum fluxes within the Martian atmospheric surface layer. To estimate the molecular viscosity and thermal conductivity of a CO2-H2O gas mixture under Martian conditions, parameterizations were developed. Parameterizations for specific heat and and binary diffusivity were also determined. The Prandtl and Schmidt numbers derived from these thermophysical properties were found to range from 0.78 - 1.0 and 0.47 - 0.70, respectively, for Mars. Brutsaert's model for sensible and latent heat transport within the interfacial sublayer for both aerodynamically smooth and rough airflow was experimentally tested under similar conditions, validating its application to Martian conditions. For the surface sublayer, the researchers modified the definition of the Monin-Obukhov length to properly account for the buoyancy forces arising from water vapor gradients in the Martian atmospheric boundary layer. This length scale was then utilized with similarity theory turbulent flux profiles with the same form as those used by Businger et al. and others. It was found that under most Martian conditions, the interfacial and surface sublayers offer roughly comparable resistance to sensible heat and water vapor transport and are thus both important in determining the associated fluxes.

  2. 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.

  3. 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

  4. 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

  5. Atmospheric boundary layer over steep surface waves

    Science.gov (United States)

    Troitskaya, Yuliya; Sergeev, Daniil A.; Druzhinin, Oleg; Kandaurov, Alexander A.; Ermakova, Olga S.; Ezhova, Ekaterina V.; Esau, Igor; Zilitinkevich, Sergej

    2014-08-01

    Turbulent air-sea interactions coupled with the surface wave dynamics remain a challenging problem. The needs to include this kind of interaction into the coupled environmental, weather and climate models motivate the development of a simplified approximation of the complex and strongly nonlinear interaction processes. This study proposes a quasi-linear model of wind-wave coupling. It formulates the approach and derives the model equations. The model is verified through a set of laboratory (direct measurements of an airflow by the particle image velocimetry (PIV) technique) and numerical (a direct numerical simulation (DNS) technique) experiments. The experiments support the central model assumption that the flow velocity field averaged over an ensemble of turbulent fluctuations is smooth and does not demonstrate flow separation from the crests of the waves. The proposed quasi-linear model correctly recovers the measured characteristics of the turbulent boundary layer over the waved water surface.

  6. Interaction between surface and atmosphere in a convective boundary layer /

    OpenAIRE

    Garai, Anirban

    2013-01-01

    Solar heating of the surface causes the near surface air to warm up and with sufficient buoyancy it ascends through the atmosphere as surface-layer plumes and thermals. The cold fluid from the upper part of the boundary layer descends as downdrafts. The downdrafts and thermals form streamwise roll vortices. All these turbulent coherent structures are important because they contribute most of the momentum and heat transport. While these structures have been studied in depth, their imprint on t...

  7. 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

    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 of the...... for the same surface features. The scaling laws have been validated analysing the Martian surface-layer data for the relations between the power spectra of wind and temperature turbulence and the corresponding mean values of wind speed and temperature. Usual spectral formulations were used based on...... the scaling laws ruling the Earth atmospheric surface layer, whereby the Earth's atmosphere is used as a standard for the Martian atmosphere....

  8. The theoretical model of atmospheric turbulence spectrum in surface layer

    Science.gov (United States)

    Liu, Shida; Liu, Shikuo; Xin, Guojun; Liang, Fuming

    1994-12-01

    It is shown that the slope of energy spectrum obtained from the velocity solution of Kdv—Burgers equation lies between —5/3 and—2 in the dilogarithmic coordinates paper. The spectrum is very close to one of Kolmogorov's isotropic turbulence and Frisch's intermittent turbulence in inertial region. In this paper, the Kdv-Burgers equation to describe atmospheric boundary layer turbulence is obtained. In the equation, the 1 / R e corresponds to dissipative coefficient v, R /2 t to dispersive coefficient β, then ( v/2 β)2 corresponds to 1 / R 2 e • Ri. We prove that the wave number corresponding to maximum energy spectrum S(k) decreases with the decrease of stability (i.e., the increase of ( v / 2 β)2 in eddy—containing region. And the spectrim amplitude decreases with the increase of ( v / 2 β)2 (i.e., the decrease of stability). These results are consistent with actual turbulence spectrum of atmospheric surface layer from turbulence data.

  9. Diurnal Variation of Air Temperature in the Atmospheric Surface Layer

    Directory of Open Access Journals (Sweden)

    Tanja Likso

    2006-09-01

    Full Text Available In order to illustrate the nature of the diurnal temperature variations in the atmospheric surface layer in all seasons a set of hourly observations at the Zagreb-Maksimir Observatory (Croatia, measured at three different levels (5 cm, 50 cm and 2 m above ground during the year 2005, was used. An approximate method for calculating air temperature at 5 cm, using the air temperature at 2 m, is presented. For this purpose, hourly data (screen height temperature, cloudiness, air pressure at barometer level and wind speed at 2 m collected at the Zagreb-Maksimir Observatory during the summer season of 2005 have been used. Th is method is based on the Monin-Obukhov similarity theory. Estimated values have been compared with observations. The results obtained are the most accurate for cloudy weather, and the least accurate in the case of clear sky. A systematic error of this approach was discovered using a clustering procedure and is briefly discussed.

  10. Diurnal Variation of Air Temperature in the Atmospheric Surface Layer

    Directory of Open Access Journals (Sweden)

    Tanja Likso

    2006-12-01

    Full Text Available In order to illustrate the nature of the diurnal temperature variations in the atmospheric surface layer in all seasons a set of hourly observations at the Zagreb-Maksimir Observatory (Croatia, measured at three different levels (5 cm, 50 cm and 2 m above ground during the year 2005, was used. An approximate method for calculating air temperature at 5 cm, using the air temperature at 2 m, is presented. For this purpose, hourly data (screen height temperature, cloudiness, air pressure at barometer level and wind speed at 2 m collected at the Zagreb-Maksimir Observatory during the summer season of 2005 have been used. Th is method is based on the Monin-Obukhov similarity theory. Estimated values have been compared with observations. The results obtained are the most accurate for cloudy weather, and the least accurate in the case of clear sky. A systematic error of this approach was discovered using a clustering procedure and is briefly discussed.

  11. Dual Nature of Heat Flux in Stable Atmospheric Surface Layer

    Science.gov (United States)

    Srivastava, P.; Sharan, M.

    2015-12-01

    The behavior of heat flux (H) with respect to the stability parameter (ζ) in stable surface layer (SSL) is analyzed with in the framework of Monin-Obukhov similarity (MOS) theory. The analytical expressions of H are obtained as functions of wind speed (U) and wind shear (dU/dz) using the linear similarity functions and accordingly two cases, (i) U = δ (constant) and (ii) dU/dz = δ are considered. The mathematical analysis shows that the magnitude of H increases with ζ till it attains a maximum value at ζ =ζc and then starts decreasing with increasing stability suggesting the dual characteristic of heat flux with stability parameter. The point of maximum heat flux is found to be dependent on the roughness length (z0) as well as the height above the surface. An attempt has been made to analyze the sensitivity of this dual characteristic of H with ζ using the non-linear similarity functions. The analysis shows that the dual nature of H persists in the case of linear as well as non-linear similarity functions. However, the point of extremum appears to be dependent on the nature of the similarity functions. Turbulent data over a tropical site Ranchi (India) is analyzed to validate the observed nature of H with the theoretical nature as predicted by MOS. The analysis of observational data reveals the non-existence of any preferred stability state in SSL as speculated by Wang and Bras (2010, 2011) and supports the conclusions of Malhi 1995, Derbyshire 1999, van de Wiel et al. 2007, Basu et al. 2008, and van de Wiel et al. 2011. Thus, the non-uniqueness of MOS equations does not appear to be a mathematical artifact and it is consistent with the observations as far as the nature of heat flux with respect to stability parameter in SSL is concerned.

  12. 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.

  13. Marine Atmospheric Surface Layer and Its Application to Electromagnetic Wave Propagation

    Science.gov (United States)

    Wang, Q.

    2015-12-01

    An important application of the atmospheric surface layer research is to characterize the near surface vertical gradients in temperature and humidity in order to predict radar and radio communication conditions in the environment. In this presentation, we will give an overview of a new research initiative funded under the Office of Naval Research (ONR) Multi-University Research Initiative (MURI): the Coupled Air-Sea Processes and EM Ducting Research (CASPER). The objective is to fully characterize the marine atmospheric boundary layer (MABL) as an electromagnetic (EM) propagation environment with the emphasis of spatial and temporal heterogeneities and surface wave/swell effects, both of which contravene the underlying assumptions of Monin-Obukhov Similarity Theory (MOST) used in coupled environmental forecast models. Furthermore, coastal variability in the inversion atop the MABL presents a challenge to forecast models and also causes practical issues in EM prediction models. These issues are the target of investigation of CASPER. CASPER measurement component includes two major field campaigns: CASPER-East (2015 Duck, NC) and CASPER-West (2018 southern California). This presentation will show the extensive measurements to be made during the CASPER -East field campaign with the focus on the marine atmospheric surface layer measurements with two research vessels, two research aircraft, surface flux buoy, wave gliders, ocean gliders, tethered balloons, and rawinsondes. Unlike previous research on the marine surface layer with the focus on surface fluxes and surface flux parameterization, CASPER field campaigns also emphasize of the surface layer profiles and the validation of the surface layer flux-profile relationship originally derived over land surfaces. Results from CASPER pilot experiment and preliminary results from CASPER-East field campaign will be discussed.

  14. Flux-Profile Relationship for Dust Concentration in the Stratified Atmospheric Surface Layer

    Science.gov (United States)

    Freire, L. S.; Chamecki, M.; Gillies, J. A.

    2016-08-01

    Flux-profile relationships are usually obtained under the assumption that the mean field of interest is in equilibrium with the associated surface fluxes. In this study, the existence of an equilibrium state for dust concentration in the atmospheric surface layer above sources and sinks is evaluated using large-eddy simulation. Results show that for steady-state turbulence and negligible horizontal advection, an equilibrium mean vertical profile of dust concentration is reached after one boundary-layer eddy turnover time. This is true for cases over a source or sink, under different atmospheric stabilities, and for particles with negligible or significant settling velocity. A new model relating the net surface flux to the vertical concentration profile that accounts for both atmospheric stability and particle settling velocity is proposed. The model compares well with the simulation results for all particle sizes and atmospheric stability conditions evaluated, and it can be used to estimate the concentration profile based on the surface flux, and also to estimate the surface flux by fitting the vertical concentration profile. The resulting equation can be considered as an extension of Monin-Obukhov similarity theory to the concentration of settling particles, such as mineral dust, sea-salt, pollen and other suspended aerosols.

  15. Observational study of atmospheric surface layer and coastal weather in northern Qatar

    Science.gov (United States)

    Samanta, Dhrubajyoti; Sadr, Reza

    2016-04-01

    Atmospheric surface layer is the interaction medium between atmosphere and Earth's surface. Better understanding of its turbulence nature is essential in characterizing the local weather, climate variability and modeling of turbulent exchange processes. The importance of Middle East region, with its unique geographical, economical and weather condition is well recognized. However, high quality micrometeorological observational studies are rare in this region. Here we show experimental results from micrometeorological observations from an experimental site in the coastal region of Qatar during August-December 2015. Measurements of winds are obtained from three sonic anemometers installed on a 9 m tower placed at Al Ghariyah beach in northern Qatar (26.08 °N, 51.36 °E). Different surface layer characteristics is analyzed and compared with earlier studies in equivalent weather conditions. Monthly statistics of wind speed, wind direction, temperature, humidity and heat index are made from concurrent observations from sonic anemometer and weather station to explore variations with surface layer characteristics. The results also highlights potential impact of sea breeze circulation on local weather and atmospheric turbulence. The observed daily maximum temperature and heat index during morning period may be related to sea breeze circulations. Along with the operational micrometeorological observation system, a camera system and ultrasonic wave measurement system are installed recently in the site to study coastline development and nearshore wave dynamics. Overall, the complete observational set up is going to provide new insights about nearshore wind dynamics and wind-wave interaction in Qatar.

  16. 222Rn and 14CO2 concentrations in the surface layer of the atmosphere

    International Nuclear Information System (INIS)

    Long-term monitoring of the Δ14C in the atmospheric near-ground CO2 has been realized in Bratislava and Zlkovce, situated near the nuclear power plant Jaslovske Bohunice. Until 1993, the monthly mean Δ14C values showed a high variability. The annual means of Δ14C were about 30 per mille higher at Zlkovce than in highly industrialised Bratislava. An important change in the behaviour of the 14C data has occurred since 1993. The records from both stations show the similar course, mainly due to the fact that there do not occur deep winter minima in Bratislava. This behaviour corresponds to the lower values of the total fossil fuel CO2 emissions in the years after 1993 when compared to the previous years. At present, both sets of data show that the 14C concentration is about 10% above the natural level. Since 1987 also the 222 Rn concentration in the surface layer of the atmosphere has been measured in Bratislava. These measurements provided an extensive set of the 222 Rn data characteristic for the inland environment with high level of atmospheric pollution. The seasonal and daily variations of the 222 Rn concentration were observed. The investigation of the relation between the monthly mean diurnal courses of the 222 Rn concentration and the atmospheric stability proved a high correlation between them. The 222 Rn data were used to interpret the anomalous Δ14C values in the surface layer of the atmosphere. (author)

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

    Science.gov (United States)

    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.

    2016-01-01

    In Earth system modelling, a description of the energy budget of the vegetated surface layer is fundamental as it determines the meteorological conditions in the planetary boundary layer and as such contributes to the atmospheric conditions and its circulation. The energy budget in most Earth system models has been based on a big-leaf approach, with averaging schemes that represent in-canopy processes. Furthermore, to be stable, that is to say, over large time steps and without large iterations, a surface layer model should be capable of implicit coupling to the atmospheric model. Surface models with large time steps, however, have difficulties in reproducing consistently the energy balance in field observations. Here we outline a newly developed numerical model for energy budget simulation, as a component of the land surface model ORCHIDEE-CAN (Organising Carbon and Hydrology In Dynamic Ecosystems - CANopy). This new model implements techniques from single-site canopy models in a practical way. It includes representation of in-canopy transport, a multi-layer long-wave radiation budget, height-specific calculation of aerodynamic and stomatal conductance, and interaction with the bare-soil flux within the canopy space. Significantly, it avoids iterations over the height of the canopy and so maintains implicit coupling to the atmospheric model LMDz (Laboratoire de Météorologie Dynamique Zoomed model). As a first test, the model is evaluated against data from both an intensive measurement campaign and longer-term eddy-covariance measurements for the intensively studied Eucalyptus stand at Tumbarumba, Australia. The model performs well in replicating both diurnal and annual cycles of energy and water fluxes, as well as the vertical gradients of temperature and of sensible heat fluxes.

  18. A coupled atmosphere and multi-layer land surface model for improving heavy rainfall simulation

    Directory of Open Access Journals (Sweden)

    M. Haggag

    2008-04-01

    Full Text Available A multi-layer land surface model (SOLVEG is dynamically coupled to the non-hydrostatic atmospheric model (MM5 in order to represent better spatial variations and changes in land surface characteristics compared with the land surface parameterization schemes included in the MM5. In this coupling, calculations of the atmosphere and land surface models are carried out as independent tasks of different processors; a model coupler controls these calculations and data exchanges among models using Message Passing Interface (MPI. This coupled model is applied to the record-breaking heavy rain events occurred in Kyushu Island, the southernmost of Japan's main islands, from 20 July to 25 July in 2006. The test computations are conducted by using both the developed coupled model and the original land surface parameterization of MM5. The result of these computations shows that SOLVEG reproduce higher ground temperature than land surface parameterization schemes in the MM5. This result indicates the feedback of land surface processes between MM5 and SOLVEG plays an important role in the computation. The most pronounced difference is in the rainfall simulation that shows the importance of coupling SOLVEG and MM5. The coupled model accurately reproduces the heavy rainfall events observed in Kyushu Island compared to the original MM5 from both the spatial and temporal point of view. This paper clearly shows that realistic simulation of rainfall event strongly depends on land-surface processes interacting with cloud development that depends on surface heat and moisture fluxes, which in turn are mainly determined by land surface vegetation and soil moisture storage. Soil temperature/moisture changes significantly affect the localized precipitation and modest improvement in the land surface representation can enhance the heavy rain simulation. MM5-SOLVEG coupling shows a clear image of land surface-atmosphere interactions and the dynamic feedback on

  19. An Experimental Study of the Statistical Scaling of Turbulent Surface Pressure in the Atmospheric Boundary Layer

    Science.gov (United States)

    Lyons, G. W.; Murray, N. E.

    2015-12-01

    Turbulence in the atmospheric boundary layer (ABL) produces fluctuations in the static pressure. The instantaneous pressure at a point depends on an integral over the entire flow; therefore, the effects from turbulence far aloft may be felt at the earth's surface. The statistics of fluctuating pressure at the surface have been studied extensively in the context of wall-bounded engineering-type flows. At best, these neutral flows are a special case of the thermally-stratified ABL, but relatively few experimental studies have considered pressure at the ground under various stability conditions. Here the scaling of pressure statistics at the surface, particularly the spectral density, is reported over a range of convective and stable conditions for both inner and outer turbulence parameters. Measurements of turbulent surface pressure were made using low-frequency microphones buried flush to the ground in a field near Laramie, Wyoming. Simultaneous measurements from three near-surface sonic anemometers and a 50-meter wind tower give estimates of the mean surface-layer parameters. The normalization of the pressure spectrum with the inner scales collapses the spectra along the high-frequency viscous power-law band. The wall shear stress, Obukhov length, L, and horizontal integral scale, λ, are identified as outer scaling parameters for the surface pressure spectrum from an integral solution employing a Monin-Obukhov-similar profile and a simple model of inhomogeneous surface-layer turbulence. Normalization with the outer scales collapses the spectra at low frequencies. Spectral scaling also reveals trends with λ/L in the low-frequency region for both convective and stable boundary layers.

  20. THERMODYNAMIC MODELING OF THE SURFACE LAYER STRUCTURE ON INCONEL 600 OXIDIZED IN A CONTROLLED ATMOSPHERE

    Directory of Open Access Journals (Sweden)

    Abdallah Haouam

    2012-03-01

    Full Text Available Samples of Inconel 600 were isothermally oxidized in a controlled atmosphere with a special mounting at high-temperature oxidation. Along with this experimental study, a simulation of thermodynamic behavior of the material in the same oxidation conditions was carried out using the Thermo-Calc code. The thermodynamic modeling is able to predict the phase nature and its distribution in the structure of the surface layer resulting from the corrosion of the material in thermodynamic equilibrium in the absence of mechanical stress. The results of this simulation are supplemented to results obtained from the analysis by glow discharge spectrometry (GDS which is performed on the samples tested.

  1. Recent progress in acoustic travel-time tomography of the atmospheric surface layer

    Directory of Open Access Journals (Sweden)

    Vladimir E. Ostashev

    2009-05-01

    Full Text Available Acoustic tomography of the atmospheric surface layer (ASL is based on measurements of the travel times of sound propagation between sources and receivers which constitute a tomography array. Then, the temperature and wind velocity fields inside the tomographic volume or area are reconstructed using different inverse algorithms. Improved knowledge of these fields is important in many practical applications. Tomography has certain advantages in comparison with currently used instrumentation for measurement of the temperature and wind velocity. In this paper, a short historical overview of acoustic tomography of the atmosphere is presented. The main emphasis is on recent progress in acoustic tomography of the ASL. The tomography arrays that have been used so far are discussed. Inverse algorithms for reconstruction of the temperature and wind velocity fields from the travel times are reviewed. Some results in numerical simulations of acoustic tomography of the ASL and reconstruction of the turbulence fields in tomography experiments are presented and discussed.

  2. Using of standard marine radar for determination of a water surface and an atmosphere near-surface layer parameters

    Science.gov (United States)

    Bogatov, Nikolay A.; Bakhanov, Victor V.; Ermoshkin, Aleksei V.; Kazakov, Vasily I.; Kemarskaya, Olga N.; Titov, Victor I.; Troitskaya, Yulia I.

    2014-10-01

    At present time radar methods of the seas and oceans diagnostics are actively developing. Using of the radar stations based on satellites and planes allows to receive information on a sea surface and a atmosphere near-surface layer with coverage of big water surface areas independently of day time. The developed methods of satellite radio images processing can be applied to marine radar stations. In Institute of Applied Physics RAS works on sea surface diagnostics systems development on the basis of standard marine radar are actively conducted. Despite smaller coverage of the territory in comparison with satellite data, marine radar have possibility to record spatially temporary radar images and to receive information on a surrounding situation quickly. This work deals with results of the researches which were conducted within the international expedition in the Atlantic Ocean in the autumn of 2012 on a route Rotterdam (Netherlands) - Ushuaya (Argentina) - Antarctica — Ushuaya. During this expedition a complex measurements of a sea surface, a atmosphere near-surface layer parameters and subsurface currents in the wide range of hydroweather conditions, including the storm were carried out. The system developed in IAP RAS on the basis of a marine radar ICOM MR-1200RII and the ADC (Analog Digital Converter) block for data recording on the personal computer was used. Display of a non-uniform near-surface current on sea surface radar images in storm conditions is shown. By means of the high-speed anemometer and meteorological station the measurements of the atmosphere parameters were carried out. Comparison of the anemometer data with calculated from radar images is carried out. Dependence of radar cross section from wind speed in the wide range of wind speeds, including storm conditions is investigated. Possibility of marine radar using for surface waves intensity and ice situation estimates also as icebergs detection is shown.

  3. The Analyses of Turbulence Characteristics in the Atmospheric Surface Layer Using Arbitrary-Order Hilbert Spectra

    Science.gov (United States)

    Wei, W.; Schmitt, F. G.; Huang, Y. X.; Zhang, H. S.

    2016-05-01

    Turbulent characteristics in the atmospheric surface layer are investigated using a data-driven method, Hilbert spectral analysis. The results from empirical mode decomposition display a set of intrinsic mode functions whose characteristic scales suggest a dyadic filter-bank property. It can be concluded from the joint probability density function of the intrinsic mode functions that the turbulent properties are totally different under different stratifications: the amplitudes (or energies) are arranged according to the stability parameter [InlineEquation not available: see fulltext.] for stable conditions, but tend to cluster randomly for unstable cases. The intermittency analyses reveal that second-order Hilbert marginal spectra display a power-law behaviour in the inertial subrange, and that the scaling exponent functions deviate from the theoretical values due to the strong intermittency in the stable boundary layer.

  4. 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.

  5. New expressions for the surface roughness length and displacement height in the atmospheric boundary layer

    Institute of Scientific and Technical Information of China (English)

    Lin Jian-Zhong; Li Hui-Jun; Zhang Kai

    2007-01-01

    An alternative model for the prediction of surface roughness length is developed. In the model a new factor is introduced to compensate for the effects of wake diffusion and interactions between the wake and roughness obstacles.The experiments are carried out by the use of the hot wire anemometry in the simulated atmospheric boundary layer in a wind tunnel. Based on the experimental data, a new expression for the zero-plane displacement height is proposed for the square arrays of roughness elements, which highlights the influence of free-stream speed on the roughness length. It appears that the displacement height increases with the wind speed while the surface roughness length decreases with Reynolds number increasing. It is shown that the calculation results based on the new expressions are in reasonable agreement with the experimental data.

  6. Forecast of surface layer meteorological parameters at Cerro Paranal with a mesoscale atmospherical model

    CERN Document Server

    Lascaux, Franck; Fini, Luca

    2015-01-01

    This article aims at proving the feasibility of the forecast of all the most relevant classical atmospherical parameters for astronomical applications (wind speed and direction, temperature) above the ESO ground-base site of Cerro Paranal with a mesoscale atmospherical model called Meso-Nh. In a precedent paper we have preliminarily treated the model performances obtained in reconstructing some key atmospherical parameters in the surface layer 0-30~m studying the bias and the RMSE on a statistical sample of 20 nights. Results were very encouraging and it appeared therefore mandatory to confirm such a good result on a much richer statistical sample. In this paper, the study was extended to a total sample of 129 nights between 2007 and 2011 distributed in different parts of the solar year. This large sample made our analysis more robust and definitive in terms of the model performances and permitted us to confirm the excellent performances of the model. Besides, we present an independent analysis of the model p...

  7. Vertical concentration profiles of dust particles in the atmospheric surface layer

    Science.gov (United States)

    Souza Freire Grion, Livia; Chamecki, Marcelo

    2013-11-01

    The study of the emission of dust particles from soil surfaces into the atmospheric boundary layer (ABL) has important applications to different environmental problems, from local air quality to large-scale aerosol transport and its interaction with climate. Due to the difficulty of measuring surface dust flux, a model relating it to the vertical profile of mean concentration is needed. In this study, we use Large-Eddy Simulation of the ABL to evaluate the effects of particle size and turbulence on the relationship between dust flux and concentration profiles. Results show that for very small particles (less than 5 micrometers) the settling velocity is usually negligible and the mean concentration displays a logarithmic profile. For large particles (more than 30 micrometers), there is an approximate balance between vertical turbulent diffusion and gravitational settling, so that Prandtl's power-law solution holds. However, a more general solution including non-zero net fluxes and gravitational settling exists, and it is in agreement with LES results for all particle sizes. Effects of atmospheric stability are also investigated. Funding from the Science Without Borders program (CNPq, Brazil) is gratefully acknowledged.

  8. On the '-1' scaling of air temperature spectra in atmospheric surface layer flows

    Science.gov (United States)

    Li, D.; Katul, G. G.; Gentine, P.

    2015-12-01

    The spectral properties of scalar turbulence at high wavenumbers have been extensively studied in turbulent flows, and existing theories explaining the k-5/3 scaling within the inertial subrange appear satisfactory at high Reynolds numbers. Equivalent theories for the low wavenumber range have been comparatively lacking because boundary conditions prohibit attainment of such universal behavior. A number of atmospheric surface layer (ASL) experiments reported a k-1 scaling in air temperature spectra ETT(k) at low wavenumbers but other experiments did not. Here, the occurrence of a k-1 scaling in ETT(k) in an idealized ASL flow across a wide range of atmospheric stability regimes is investigated theoretically and experimentally. Experiments reveal a k-1 scaling persisted across different atmospheric stability parameter values (ζ) ranging from mildly unstable to mildly stable conditions (-0.1budget models and upon using a Heisenberg eddy viscosity as a closure to the spectral flux transfer term, conditions promoting a k-1 scaling are identified. Existence of a k-1 scaling is shown to be primarily linked to an imbalance between the production and dissipation rates of half the temperature variance. The role of the imbalance between the production and dissipation rates of half the temperature variance in controlling the existence of a '-1' scaling suggests that the '-1' scaling in ETT(k) does not necessarily concur with the '-1' scaling in the spectra of longitudinal velocity Euu(k). This finding explains why some ASL experiments reported k-1 in Euu(k) but not ETT(k). It also differs from prior arguments derived from directional-dimensional analysis that lead to simultaneous k-1 scaling in Euu(k) and ETT(k) at low wavenumbers in a neutral ASL.

  9. One year of 222Rn concentration in the atmospheric surface layer

    Directory of Open Access Journals (Sweden)

    S. Galmarini

    2006-01-01

    Full Text Available A one-year time series of 222Rn measured in a rural area in the North of Italy in 1997 is analyzed. The scope of the investigation is to better understand the behavior of this common atmospheric tracer in relation to the meteorological conditions at the release site. Wavelet analysis is used as one of the investigation tools of the time series. The measurements and scalograms of 222Rn are compared to those of wind-speed, pressure, relative humidity, temperature and NOx. The use of wavelet analysis allows the identification of the various scales controlling the influence of the meteorological variables on 222Rn dispersion in the surface layer that are not visible through classical Fourier analysis or direct time series inspection. The analysis of the time series has identified specific periods during which the usual diurnal variation of radon is superimposed to a linear growth thus indicating the build up of concentration at the measurement level. From these specific cases an estimate of the surface flux of 222Rn is made. By means of a simple model these special cases are reproduced.

  10. Large eddies modulating flux convergence and divergence in a disturbed unstable atmospheric surface layer

    Science.gov (United States)

    Gao, Zhongming; Liu, Heping; Russell, Eric S.; Huang, Jianping; Foken, Thomas; Oncley, Steven P.

    2016-02-01

    The effects of large eddies on turbulence structures and flux transport were studied using data collected over a flat cotton field during the Energy Balance Experiment 2000 in the San Joaquin Valley of California in August 2000. Flux convergence (FC; larger fluxes at 8.7 m than 2.7 m) and divergence (FD) in latent heat flux (LE) were observed in a disturbed, unstable atmospheric surface layer, and their magnitudes largely departed from the prediction of Monin-Obukhov similarity theory. From our wavelet analysis, it was identified that large eddies affected turbulence structures, scalar distribution, and flux transport differently at 8.7 m and 2.7 m under the FC and FD conditions. Using the ensemble empirical mode decomposition, time series data were decomposed into large eddies and small-scale background turbulence, the time-domain characteristics of large eddies were examined, and the flux contribution by large eddies was also determined quantitatively. The results suggest that large eddies over the frequency range of 0.002 Hz < f < 0.02 Hz (predominantly 300-400 m) enhanced the vertical velocity spectra more significantly at 8.7 m than 2.7 m, leading to an increased magnitude of the cospectra and thus LE at 8.7 m. In the FD case, however, these large eddies were not present and even suppressed in the vertical velocity spectra at 8.7 m. Consequently, the cospectra divergence over the low-frequency ranges primarily caused the LE divergence. This work implies that large eddies may either improve or degrade the surface energy balance closure by increasing or decreasing turbulent fluxes, respectively.

  11. Using a Modified Soil-Plant-Atmosphere Scheme (MSPAS) to Simulate the Interaction between Land Surface Processes and Atmospheric Boundary Layer in Semi-Arid Regions

    Institute of Scientific and Technical Information of China (English)

    刘树华; 乐旭; 胡非; 刘辉志

    2004-01-01

    This paper uses a Modified Soil-Plant-Atmosphere Scheme (MSPAS) to study the interaction between land surface and atmospheric boundary layer processes. The scheme is composed of two main parts:atmospheric boundary layer processes and land surface processes. Compared with SiB and BATS, which are famous for their detailed parameterizations of physical variables, this simplified model is more convenient and saves much more computation time. Though simple, the feasibility of the model is well proved in this paper. The numerical simulation results from MSPAS show good agreement with reality. The scheme is used to obtain reasonable simulations for diurnal variations of heat balance, potential temperature of boundary layer, and wind field, and spatial distributions of temperature, specific humidity, vertical velocity,turbulence kinetic energy, and turbulence exchange coefficient over desert and oasis. In addition, MSPAS is used to simulate the interaction between desert and oasis at night, and again it obtains reasonable results.This indicates that MSPAS can be used to study the interaction between land surface processes and the atmospheric boundary layer over various underlying surfaces and can be extended for regional climate and numerical weather prediction study.

  12. 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.

  13. Accelerated formation of sodium depletion layer on soda lime glass surface by corona discharge treatment in hydrogen atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Kawaguchi, Keiga; Ikeda, Hiroshi; Sakai, Daisuke [Research Institute for Electronic Science, Hokkaido University, N20 W10, Kita-ku, Sapporo, Hokkaido 001-0020 (Japan); Funatsu, Shiro; Uraji, Keiichiro [Production Technology Center, Asahi Glass Co., Ltd. , 1-1 Suehiro-cyo, Tsurumiku, Yokohama, Kanagawa, 230-0045 (Japan); Yamamoto, Kiyoshi; Suzuki, Toshio [Research Center, Asahi Glass Co., Ltd., 1150 Hazawa-cho, Kanagawa-ku, Yokohama, Kanagawa, 221-8755 (Japan); Harada, Kenji [Department of Computer Science, Kitami Institute of Technology, 165 Koen-cho, Kitami, Hokkaido 090-8507 (Japan); Nishii, Junji, E-mail: nishii@es.hokudai.ac.jp [Research Institute for Electronic Science, Hokkaido University, N20 W10, Kita-ku, Sapporo, Hokkaido 001-0020 (Japan)

    2014-05-01

    Highlights: • Corona discharge formed an alkali depletion layer on a glass surface. • Introduction of hydrogen accelerated the depletion layer thickness. • Thickness was doubled compared with that in air. • Efficient formation of proton at an anode needle end was one cause. • Applied voltage across the glass plate in hydrogen was 2.7 times that in air. - Abstract: Formation of a sodium depletion layer on a soda lime glass surface was accelerated efficiently using a corona discharge treatment in H{sub 2} atmosphere. One origin of such acceleration was the preferential generation of H{sup +} with a larger mobility at an anode needle end with a lower applied voltage than that in air. The second origin was the applied voltage across the glass plate during the corona discharge treatment, which was estimated theoretically as 2.7 times higher than that in air. These two effects doubled the depletion layer thickness compared with that in air.

  14. Accelerated formation of sodium depletion layer on soda lime glass surface by corona discharge treatment in hydrogen atmosphere

    International Nuclear Information System (INIS)

    Highlights: • Corona discharge formed an alkali depletion layer on a glass surface. • Introduction of hydrogen accelerated the depletion layer thickness. • Thickness was doubled compared with that in air. • Efficient formation of proton at an anode needle end was one cause. • Applied voltage across the glass plate in hydrogen was 2.7 times that in air. - Abstract: Formation of a sodium depletion layer on a soda lime glass surface was accelerated efficiently using a corona discharge treatment in H2 atmosphere. One origin of such acceleration was the preferential generation of H+ with a larger mobility at an anode needle end with a lower applied voltage than that in air. The second origin was the applied voltage across the glass plate during the corona discharge treatment, which was estimated theoretically as 2.7 times higher than that in air. These two effects doubled the depletion layer thickness compared with that in air

  15. Study of Near-Surface Models in Large-Eddy Simulations of a Neutrally Stratified Atmospheric Boundary Layer

    Science.gov (United States)

    Senocak, I.; Ackerman, A. S.; Kirkpatrick, M. P.; Stevens, D. E.; Mansour, N. N.

    2004-01-01

    Large-eddy simulation (LES) is a widely used technique in armospheric modeling research. In LES, large, unsteady, three dimensional structures are resolved and small structures that are not resolved on the computational grid are modeled. A filtering operation is applied to distinguish between resolved and unresolved scales. We present two near-surface models that have found use in atmospheric modeling. We also suggest a simpler eddy viscosity model that adopts Prandtl's mixing length model (Prandtl 1925) in the vicinity of the surface and blends with the dynamic Smagotinsky model (Germano et al, 1991) away from the surface. We evaluate the performance of these surface models by simulating a neutraly stratified atmospheric boundary layer.

  16. Estimating the atmospheric boundary layer height over sloped, forested terrain from surface spectral analysis during BEARPEX

    Directory of Open Access Journals (Sweden)

    W. Choi

    2010-11-01

    Full Text Available In this study the atmospheric boundary layer (ABL height (zi over complex, forested terrain is estimated based on the power spectra and the integral length scale of horizontal winds obtained from a three-axis sonic anemometer during the BEARPEX (Biosphere Effects on Aerosol and Photochemistry Experiment. The zi values estimated with this technique showed very good agreement with observations obtained from balloon tether sonde (2007 and rawinsonde (2009 measurements under unstable conditions (z/L < 0 at the coniferous forest in the California Sierra Nevada. The behavior of the nocturnal boundary layer height (h and power spectra of lateral winds and temperature under stable conditions (z/L > 0 is also presented. The nocturnal boundary layer height is found to be fairly well predicted by a recent interpolation formula proposed by Zilitinkevich et al. (2007, although it was observed to only vary from 60–80 m during the experiment. Finally, significant directional wind shear was observed during both day and night with winds backing from the prevailing west-southwesterlies in the ABL (anabatic cross-valley circulation to consistent southerlies in a layer ~1 km thick just above the ABL before veering to the prevailing westerlies further aloft. We show that this is consistent with the forcing of a thermal wind driven by the regional temperature gradient directed due east in the lower troposphere.

  17. Improving the Representation of the Nocturnal Near-Neutral Surface Layer in the Urban Environment with a Mesoscale Atmospheric Model

    Science.gov (United States)

    Husain, Syed Zahid; Bélair, Stéphane; Mailhot, Jocelyn; Leroyer, Sylvie

    2013-06-01

    A new approach to improve the representation of surface processes in the Global Environmental Multiscale (GEM) atmospheric model associated with the exchanges between the urban canopy and the atmosphere is presented. Effects of the urban canopy on the evolution of surface-layer wind, temperature, moisture, and turbulence are directly parametrized in order to allow realistic interactions between the canopy elements (i.e., roofs, roads, and walls) and the atmosphere at GEM's multiple vertical levels that are positioned inside the canopy. Surface energy budgets as implemented in the Town Energy Balance (TEB) scheme have been used to determine temperatures of the urban canopy elements for the proposed multilayer scheme. Performance of the multilayer scheme is compared against standard implementations of the TEB scheme for one nighttime intensive observation period of the Joint Urban 2003 experiment held in Oklahoma City, USA. Although the new approach is found to have a negligible impact on urban surface-layer wind profiles, it improves the prediction of near-neutral nocturnal profiles of potential temperature close to the surface. The urban heat island effect is simulated with a better accuracy by the multilayer approach. The horizontal temperature gradient across the central business district of the city along the direction of flow is also reasonably well captured by the proposed scheme.

  18. Accelerated formation of sodium depletion layer on soda lime glass surface by corona discharge treatment in hydrogen atmosphere

    Science.gov (United States)

    Kawaguchi, Keiga; Ikeda, Hiroshi; Sakai, Daisuke; Funatsu, Shiro; Uraji, Keiichiro; Yamamoto, Kiyoshi; Suzuki, Toshio; Harada, Kenji; Nishii, Junji

    2014-05-01

    Formation of a sodium depletion layer on a soda lime glass surface was accelerated efficiently using a corona discharge treatment in H2 atmosphere. One origin of such acceleration was the preferential generation of H+ with a larger mobility at an anode needle end with a lower applied voltage than that in air. The second origin was the applied voltage across the glass plate during the corona discharge treatment, which was estimated theoretically as 2.7 times higher than that in air. These two effects doubled the depletion layer thickness compared with that in air.

  19. Turbulent Characterization of atmospheric surface layer over non-homogeneous terrain

    International Nuclear Information System (INIS)

    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 (Z0 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

  20. Estimating Intermittency Exponent in Neutrally Stratified Atmospheric Surface Layer Flows: A Robust Framework based on Magnitude Cumulant and Surrogate Analyses

    CERN Document Server

    Basu, S; Lashermes, B; Arnéodo, A; Basu, Sukanta; Foufoula-Georgiou, Efi; Lashermes, Bruno; Arneodo, Alain

    2007-01-01

    This study proposes a novel framework based on magnitude cumulant and surrogate analyses to reliably detect and estimate the intermittency coefficient from short-length coarse-resolution turbulent time series. Intermittency coefficients estimated from a large number of neutrally stratified atmospheric surface layer turbulent series from various field campaigns are shown to remarkably concur with well-known laboratory experimental results. In addition, a surrogate-based hypothesis testing framework is proposed and shown to significantly reduce the likelihood of detecting a spurious non-zero intermittency coefficient from non-intermittent series. The discriminatory power of the proposed framework is promising for addressing the unresolved question of how atmospheric stability affects the intermittency properties of boundary layer turbulence.

  1. The relationship between ozone formation and air temperature in the atmospheric surface layer

    Science.gov (United States)

    Belan, Boris D.; Savkin, Denis; Tolmachev, Gennadii

    2016-04-01

    Studying the formation and dynamics of ozone in the atmosphere is important due to several reasons. First, the contribution of tropospheric ozone to the global greenhouse effect is only slightly less than that of water vapor, carbon dioxide, and methane. Second, tropospheric ozone acts as a strong poison that has negative effects on human health, animals, and vegetation. Third, being a potent oxidizer, ozone destroys almost all materials, including platinum group metals and compounds. Fourthly, ozone is formed in situ from precursors as a result of photochemical processes, but not emitted into the atmosphere by any industrial enterprises directly. In this work, we present some results of the study aimed at the revealing relationship between ozone formation rate and surface air temperature in the background atmosphere. It has been found that this relationship is nonlinear. Analysis of the possible reasons showed that the nonlinear character of this relationship may be due to a nonlinear increase in the reaction constants versus air temperature and a quadratic increase in the concentration of hydrocarbons with increasing temperature. This work was supported by the Ministry of Education and Science contract no.14.613.21.0013 (ID: RFMEFI61314X0013).

  2. 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

  3. MOSE: optical turbulence and atmospherical parameters operational forecast at ESO ground-based sites. II: atmospherical parameters in the surface layer [0-30] m

    CERN Document Server

    Lascaux, Franck; Fini, Luca

    2013-01-01

    This article is the second of a series of articles aiming at proving the feasibility of the forecast of all the most relevant classical atmospherical parameters for astronomical applications (wind speed and direction, temperature, relative humidity) and the optical turbulence (Cn2 and the derived astro-climatic parameters like seeing, isoplanatic angle, wavefront coherence time...). This study is done in the framework of the MOSE project, and focused above the two ESO ground-bases sites of Cerro Paranal and Cerro Armazones. In this paper we present the results related to the Meso-Nh model ability in reconstructing the surface layer atmospherical parameters (wind speed intensity, wind direction and absolute temperature, [0-30] m a.g.l.). The model reconstruction of all the atmospherical parameters in the surface layer is very satisfactory. For the temperature, at all levels, the RMSE (Root Mean Square Error) is inferior to 1{\\deg}C. For the wind speed, it is ~2 m/s, and for the wind direction, it is in the ran...

  4. 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

  5. The Role of Large-Coherent-Eddy Transport in the Atmospheric Surface Layer Based on CASES-99 Observations

    Science.gov (United States)

    Sun, Jielun; Lenschow, Donald H.; LeMone, Margaret A.; Mahrt, Larry

    2016-07-01

    The analysis of momentum and heat fluxes from the Cooperative Atmosphere-Surface Exchange Study 1999 (CASES-99) field experiment is extended throughout the diurnal cycle following the investigation of nighttime turbulence by Sun et al. (J Atmos Sci 69:338-351, 2012). Based on the observations, limitations of Monin-Obukhov similarity theory (MOST) are examined in detail. The analysis suggests that strong turbulent mixing is dominated by relatively large coherent eddies that are not related to local vertical gradients as assumed in MOST. The HOckey-Stick Transition (HOST) hypothesis is developed to explain the generation of observed large coherent eddies over a finite depth and the contribution of these eddies to vertical variations of turbulence intensity and atmospheric stratification throughout the diurnal cycle. The HOST hypothesis emphasizes the connection between dominant turbulent eddies and turbulence generation scales, and the coupling between the turbulence kinetic energy and the turbulence potential energy within the turbulence generation layer in determining turbulence intensity. For turbulence generation directly influenced by the surface, the HOST hypothesis recognizes the role of the surface both in the vertical variation of momentum and heat fluxes and its boundary effect on the size of the dominant turbulence eddies.

  6. The Estimation of Surface Latent Heat Flux over the Ocean and its Relationship to Marine Atmospheric Boundary Layer (MABL) Structure

    Science.gov (United States)

    Palm, Stephen P.; Schwemmer, Geary K.; Vandemark, Doug; Evans, Keith; Miller, David O.; Demoz, Belay B.; Starr, David OC. (Technical Monitor)

    2001-01-01

    A new technique combining active and passive remote sensing instruments for the estimation of surface latent heat flux over the ocean is presented. This synergistic method utilizes aerosol lidar backscatter data, multi-channel infrared radiometer data, and microwave scatterometer data acquired onboard the NASA P-313 research aircraft during an extended field campaign over the Atlantic ocean in support of the Lidar In-space Technology Experiment (LITE) in September of 1994. The 10 meter wind speed derived from scatterometers and lidar-radiometer inferred near-surface moisture are used to obtain an estimate of the surface flux of moisture via a bulk aerodynamic formula. The results are compared with the Special Sensor Microwave Imager (SSM/I) daily average latent heat flux and show reasonable agreement. However, the SSM/I values are biased low by about 15 W/sq m. In addition, the Marine Atmospheric Boundary Layer (MABL) height, entrainment zone thickness and integrated lidar backscatter intensity are computed from the lidar data and compared with the magnitude of the surface fluxes. The results show that the surface latent heat flux is most strongly correlated with entrainment zone depth, MABL height and the integrated MABL lidar backscatter, with corresponding correlation coefficients of 0.39, 0.43 and 0.71, respectively.

  7. Modeling the Evolution of the Atmospheric Boundary Layer Coupled to the Land Surface for Three Contrasting Nights in CASES-99

    NARCIS (Netherlands)

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

    2006-01-01

    The modeling and prediction of the stable boundary layer over land is a persistent, problematic feature in weather. climate, and air quality topics. Here, the performance of a state-of-the-art single-column boundary layer model is evaluated with observations from the 1999 Cooperative Atmosphere-Surf

  8. 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

  9. Characteristics of particulate radionuclides in the atmospheric surface layer of the 30-km zone of Chernobyl

    International Nuclear Information System (INIS)

    For the inhalation dose assessment, reliable estimations are necessary of the average volume concentration of particle bound radionuclides in the atmosphere specifying the nuclide composition, the activity distribution in the different particle size ranges and the solubility characteristics of the nuclides. For that purpose, the analysis of measurement series is presented of the daily average activity concentrations of 137Cs and 144Ce and their temporal and spatial variability. From 1986 till 1994, samples were taken with high-volume samplers and multicascade impactors; the number concentrations of aerosol particles and the number concentrations of 'hot' particles were determined for different conditions with an Aerosol Particle Sizer and a Rotating Arm Impactor. The data demonstrate a decrease the atmospheric concentrations of 137Cs and 144Ce with time larger than caused by radioactive decay alone. A statistical analysis showed a high level of fluctuations in the concentration of radionuclides in air with maxima exceeding the annual average by 10 to 20 times. The analysis of 88 experimental radioactivity size distributions at Zapolie and Pripyat for winddriven resuspension conditions have shown that the measured distributions are generally very wide and differ from the log-normal distribution in the most cases. At Zapolie, the mean air concentrations of 137Cs, discriminated in four size ranges, showed an increasing part of inhalable particles with time since the accident. In 1993, the inhalable fraction was about 48% of the total concentration. The size distribution of atmospheric 137Cs particulate activity during these periods of enhanced resuspension showed a similar common shape with two maxima, the first in the 2-4 μm range, and the second in the 12-20 μm range. The estimated radioactive loading of particles showed an enrichment of resuspended radionuclides compared with soil particles. The highest enrichment factor was found for large particles, the lowest

  10. Diurnal and vertical variability of the sensible heat and carbon dioxide budgets in the atmospheric surface layer

    International Nuclear Information System (INIS)

    The diurnal and vertical variability of heat and carbon dioxide (CO2) in the atmospheric surface layer are studied by analyzing measurements from a 213 m tower in Cabauw (Netherlands). Observations of thermodynamic variables and CO2 mixing ratio as well as vertical profiles of the turbulent fluxes are used to retrieve the contribution of the budget terms in the scalar conservation equation. On the basis of the daytime evolution of turbulent fluxes, we calculate the budget terms by assuming that turbulent fluxes follow a linear profile with height. This assumption is carefully tested and the deviation from linearity is quantified. The budget calculation allows us to assess the importance of advection of heat and CO2 during day hours for three selected days. It is found that, under nonadvective conditions, the diurnal variability of temperature and CO2 is well reproduced from the flux divergence measurements. Consequently, the vertical transport due to the turbulent flux plays a major role in the daytime evolution of both scalars and the advection is a relatively small contribution. During the analyzed days with a strong contribution of advection of either heat or carbon dioxide, the flux divergence is still an important contribution to the budget. For heat, the quantification of the advection contribution is in close agreement with results from a numerical model. For carbon dioxide, we qualitatively corroborate the results with a Lagrangian transport model. Our estimation of advection is compared with traditional estimations based on the Net Ecosystem-atmosphere Exchange (NEE)

  11. Scaling Of Turbulence In The Atmospheric Surface-Layer: Which Anisotropy?

    International Nuclear Information System (INIS)

    This paper aims to provide an insight into the fundamental relationships between large and small scale wind velocity fluctuations within the boundary layer through careful analysis of measuring mast wind velocities. The measuring mast was in a wind farm on top of a mountain (with steep inclines of about 30°) on an island surrounded by the sea which meant the horizontal mean flow fluctuations were dominated by buoyancy forces and vertical shears at large scales (above 500m). Thus using a variety of methods including spectral, integrated spectral, integrated cospectral and multifractal analysis we were able to clearly dispel the relevance of 2D turbulence and give on the contrary some credence to the multifractal anisotropic model.

  12. Near-Surface Wind Predictions in Complex Terrain with a CFD Approach Optimized for Atmospheric Boundary Layer Flows

    Science.gov (United States)

    Wagenbrenner, N. S.; Forthofer, J.; Butler, B.; Shannon, K.

    2014-12-01

    Near-surface wind predictions are important for a number of applications, including transport and dispersion, wind energy forecasting, and wildfire behavior. Researchers and forecasters would benefit from a wind model that could be readily applied to complex terrain for use in these various disciplines. Unfortunately, near-surface winds in complex terrain are not handled well by traditional modeling approaches. Numerical weather prediction models employ coarse horizontal resolutions which do not adequately resolve sub-grid terrain features important to the surface flow. Computational fluid dynamics (CFD) models are increasingly being applied to simulate atmospheric boundary layer (ABL) flows, especially in wind energy applications; however, the standard functionality provided in commercial CFD models is not suitable for ABL flows. Appropriate CFD modeling in the ABL requires modification of empirically-derived wall function parameters and boundary conditions to avoid erroneous streamwise gradients due to inconsistences between inlet profiles and specified boundary conditions. This work presents a new version of a near-surface wind model for complex terrain called WindNinja. The new version of WindNinja offers two options for flow simulations: 1) the native, fast-running mass-consistent method available in previous model versions and 2) a CFD approach based on the OpenFOAM modeling framework and optimized for ABL flows. The model is described and evaluations of predictions with surface wind data collected from two recent field campaigns in complex terrain are presented. A comparison of predictions from the native mass-consistent method and the new CFD method is also provided.

  13. The use of kite observations to study air-sea interaction-controlled atmospheric surface layer profiles during the red experiment

    OpenAIRE

    DAVIDSON, KENNETH L.; Guest, Peter S.; Mabey, Deborah L.; Frederickson, Paul A.; Anderson, Kenneth D.

    2003-01-01

    The Roughness and Evaporation Duct (RED) experiment was designed to relate the effect of atmospheric boundary layer (ABL) features as well as ocean surface roughness to near-surface high frequency electromagnetic propagation. For this, ABL and ocean surface data, as well as propagation data, were collected at mid-path locations in August and September 2001 off the windward coast of Oahu, Hawaii. The Naval Postgraduate School (NPS) and SPAWAR Systems Center, San Diego (SSC-SD) performed collab...

  14. 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.

  15. Diurnal and vertical variability of the sensible heat and carbon dioxide budgets in the atmospheric surface layer

    Science.gov (United States)

    Casso-Torralba, P.; de Arellano, J. V. -G.; Bosveld, F.; Soler, M.R.; Vermeulen, A.; Werner, C.; Moors, E.

    2008-01-01

    The diurnal and vertical variability of heat and carbon dioxide (CO2) in the atmospheric surface layer are studied by analyzing measurements from a 213 in tower in Cabauw (Netherlands). Observations of thermodynamic variables and CO2 mixing ratio as well as vertical profiles of the turbulent fluxes are used to retrieve the contribution of the budget terms in the scalar conservation equation. On the basis of the daytime evolution of turbulent fluxes, we calculate the budget terms by assuming that turbulent fluxes follow a linear profile with height. This assumption is carefully tested and the deviation ftom linearity is quantified. The budget calculation allows us to assess the importance of advection of heat and CO2 during day hours for three selected days. It is found that, under nonadvective conditions, the diurnal variability of temperature and CO2 is well reproduced from the flux divergence measurements. Consequently, the vertical transport due to the turbulent flux plays a major role in the daytime evolution of both scalars and the advection is a relatively small contribution. During the analyzed days with a strong contribution of advection of either heat or carbon dioxide, the flux divergence is still an important contribution to the budget. For heat, the quantification of the advection contribution is in close agreement with results from a numerical model. For carbon dioxide, we qualitatively corroborate the results with a Lagrangian transport model. Our estimation of advection is compared with, traditional estimations based on the Net Ecosystem-atmosphere Exchange (NEE). Copyright 2008 by the American Geophysical Union.

  16. the Martian atmospheric boundary layer

    DEFF Research Database (Denmark)

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

    2011-01-01

    . This portion of the atmosphere is extremely important, both scientifically and operationally, because it is the region within which surface lander spacecraft must operate and also determines exchanges of heat, momentum, dust, water, and other tracers between surface and subsurface reservoirs and the free...

  17. Impact of atmospheric forcing on heat content variability in the sub-surface layer in the Japan/East Sea, 1948-2009

    Science.gov (United States)

    Stepanov, Dmitry; Gusev, Anatoly; Diansky, Nikolay

    2016-04-01

    Based on numerical simulations the study investigates impact of atmospheric forcing on heat content variability of the sub-surface layer in Japan/East Sea (JES), 1948-2009. We developed a model configuration based on a INMOM model and atmospheric forcing extracted from the CORE phase II experiment dataset 1948-2009, which enables to assess impact of only atmospheric forcing on heat content variability of the sub-surface layer of the JES. An analysis of kinetic energy (KE) and total heat content (THC) in the JES obtained from our numerical simulations showed that the simulated circulation of the JES is being quasi-steady state. It was found that the year-mean KE variations obtained from our numerical simulations are similar those extracted from the SODA reanalysis. Comparison of the simulated THC and that extracted from the SODA reanalysis showed significant consistence between them. An analysis of numerical simulations showed that the simulated circulation structure is very similar that obtained from the PALACE floats in the intermediate and abyssal layers in the JES. Using empirical orthogonal function analysis we studied spatial-temporal variability of the heat content of the sub-surface layer in the JES. Based on comparison of the simulated heat content variations with those obtained from natural observations an assessment of the atmospheric forcing impact on the heat content variability was obtained. Using singular value decomposition analysis we considered relationships between the heat content variability and wind stress curl as well as sensible heat flux in winter. It was established the major role of sensible heat flux in decadal variability of the heat content of the sub-surface layer in the JES. The research was supported by the Russian Foundation for Basic Research (grant N 14-05-00255) and the Council on the Russian Federation President Grants (grant N MK-3241.2015.5)

  18. Observations of the atmospheric surface layer parameters over a semi arid region during the solar eclipse of August 11th, 1999

    Indian Academy of Sciences (India)

    Praveena Krishnan; P K Kunhikrishnan; S Muraleedharan Nair; Sudha Ravindran; Radhika Ramachandran; D B Subrahamanyam; M Venkata Ramana

    2004-09-01

    This paper discusses the observations of the Atmospheric Surface Layer (ASL) parameters during the solar eclipse of August 11th, 1999. Intensive surface layer experiments were conducted at Ahmedabad (23° 21′N, 72° 36′E), the western part of India, which was close to the totality path. This rare event provided by nature is utilised to document the surface layer effects during the eclipse period using measurements of high frequency fluctuations of temperature, tri-axial wind components as well as mean parameters such as temperature, humidity, wind speed and subsoil temperature. Analysis showed that during the eclipse period, the turbulence parameters were affected leading to the suppression of the turbulence process, the main dynamic process in the atmospheric boundary layer, while the mean parameters showed variations within the natural variability of the observational period. 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 stable condition during the period of eclipse and back to unstable condition by the end of eclipse.

  19. Titan's surface and atmosphere

    Science.gov (United States)

    Hayes, Alexander G.; Soderblom, Jason M.; Ádámkovics, Máté

    2016-05-01

    Since its arrival in late 2004, the NASA/ESA Cassini-Huygens mission to Saturn has revealed Titan to be a world that is both strange and familiar. Titan is the only extraterrestrial body known to support standing bodies of stable liquid on its surface and, along with Earth and early Mars, is one of three places in the Solar System known to have had an active hydrologic cycle. With atmospheric pressures of 1.5 bar and temperatures of 90-95 K at the surface, methane and ethane condense out of Titan's nitrogen-dominated atmosphere and flow as liquids on the surface. Despite vast differences in environmental conditions and materials from Earth, Titan's methane-based hydrologic cycle drives climatic and geologic processes which generate landforms that are strikingly similar to their terrestrial counterparts, including vast equatorial dunes, well-organized channel networks that route material through erosional and depositional landscapes, and lakes and seas of liquid hydrocarbons. These similarities make Titan a natural laboratory for studying the processes that shape terrestrial landscapes and drive climates, probing extreme conditions impossible to recreate in earthbound laboratories. Titan's exotic environment ensures that even rudimentary measurements of atmospheric/surface interactions, such as wind-wave generation or aeolian dune development, provide valuable data to anchor physical models.

  20. Estimating the surface layer refractive index structure constant over snow and sea ice using Monin-Obukhov similarity theory with a mesoscale atmospheric model.

    Science.gov (United States)

    Qing, Chun; Wu, Xiaoqing; Huang, Honghua; Tian, Qiguo; Zhu, Wenyue; Rao, Ruizhong; Li, Xuebin

    2016-09-01

    Since systematic direct measurements of refractive index structure constant ( Cn2) for many climates and seasons are not available, an indirect approach is developed in which Cn2 is estimated from the mesoscale atmospheric model outputs. In previous work, we have presented an approach that a state-of-the-art mesoscale atmospheric model called Weather Research and Forecasting (WRF) model coupled with Monin-Obukhov Similarity (MOS) theory which can be used to estimate surface layer Cn2 over the ocean. Here this paper is focused on surface layer Cn2 over snow and sea ice, which is the extending of estimating surface layer Cn2 utilizing WRF model for ground-based optical application requirements. This powerful approach is validated against the corresponding 9-day Cn2 data from a field campaign of the 30th Chinese National Antarctic Research Expedition (CHINARE). We employ several statistical operators to assess how this approach performs. Besides, we present an independent analysis of this approach performance using the contingency tables. Such a method permits us to provide supplementary key information with respect to statistical operators. These methods make our analysis more robust and permit us to confirm the excellent performances of this approach. The reasonably good agreement in trend and magnitude is found between estimated values and measurements overall, and the estimated Cn2 values are even better than the ones obtained by this approach over the ocean surface layer. The encouraging performance of this approach has a concrete practical implementation of ground-based optical applications over snow and sea ice. PMID:27607648

  1. Surface and optical properties of indium tin oxide layer deposition by RF magnetron sputtering in argon atmosphere

    Science.gov (United States)

    Yudar, H. Hakan; Korkmaz, Şadan; Özen, Soner; Şenay, Volkan; Pat, Suat

    2016-08-01

    This study focused on the characterization and properties of transparent and conductive indium tin oxide (ITO) thin films deposited in argon atmosphere. ITO thin films were coated onto glass substrates by radio frequency (RF) magnetron sputtering technique at 75 and 100 W RF powers. Structural characteristics of producing films were investigated through X-ray diffraction analysis. UV-Vis spectrophotometer and interferometer were used to determine transmittance, absorbance and reflectance values of samples. The surface morphology of the films was characterized by atomic force microscope. The calculated band gaps were 3.8 and 4.1 eV for the films at 75 and 100 W, respectively. The effect of RF power on crystallinity of prepared films was explored using mentioned analysis methods. The high RF power caused higher poly crystallinity in the produced samples. The thickness and refractive index values for all samples increased respect to an increment of RF power and were calculated as 20, 50 nm and 1.71, 1.86 for samples at 75 and 100 W, respectively. Finally, the estimated grain sizes for all prepared films decreased with increasing of 2 θ degrees, and the number of crystallite per unit volume was calculated. It was found that nearly all properties including sheet resistance and resistivity depend on the RF power.

  2. 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.

  3. Coupled Ocean Atmosphere Mesoscale Prediction System modeled surface layer refractivity in the Roughness and Evaporation Duct experiment 2001

    OpenAIRE

    Newton, D. Adam

    2003-01-01

    Approved for public release, distribution is unlimited A study of the performance of the Coupled Ocean Atmosphere Mesoscale Prediction System (COAMPS) was performed based on collected METOC properties affecting radar propagation during the Roughness and Evaporation Duct (RED) experiment conducted off the windward coast of Oahu, HI. The measured refractivity influencing parameters (SST, air temperature, humidity, and wind speed) were compared to COAMPS predicted values. Using the NPS bulk e...

  4. Estimates of regional surface carbon dioxide exchange and carbon and oxygen isotope discrimination during photosynthesis from concentration profiles in the atmospheric boundary layer

    International Nuclear Information System (INIS)

    The integrating properties of the atmospheric boundary layer allow the influence of surface exchange processes on the atmosphere to be quantified and estimates of large-scale fluxes of trace gases and plant isotopic discrimination to be made. Five flights were undertaken over two days in and above the convective boundary layer (CBL) in a vegetated region in central Siberia. Vertical profiles of CO2 and H2O concentrations, temperature and pressure were obtained during each flight. Air flask samples were taken at various heights for carbon and oxygen isotopic analysis of CO2. Two CBL budget methods were compared to estimate regional surface fluxes of CO2 and plant isotopic discrimination against 13CO2 and C18O16O. Flux estimates were compared to ground-based eddy covariance measurements. The fluxes obtained for CO2 using the first method agreed to within 10% of fluxes measured in the forest at the study site by eddy covariance. Those obtained from the second method agreed to within 35% when a correction was applied for air loss out of the integrating column and for subsidence. The values for 13C discrimination were within the range expected from knowledge of C3 plant discriminations during photosynthesis, while the inferred 18O discrimination varied considerably over the two-day period. This variation may in part be explained by the enrichment of chloroplast water during the day due to evaporation from an initial signature in the morning close to source water. Additional potential complications arising from the heterogeneous nature of the landscape are discussed

  5. Low-frequency modulation of the atmospheric surface layer over Amazonian rain forest and its implication for similarity relationships

    NARCIS (Netherlands)

    Randow, von C.; Kruijt, B.; Holtslag, A.A.M.

    2006-01-01

    The application of Monin-Obukhov similarity theory (MOS) is based on empirical relationships derived over uniform surfaces in flat terrain. It is not clear to what extent these relationships hold for complex surfaces such as tropical forest or hilly terrain. This study investigates the influence of

  6. Influence of small-scale North Atlantic sea surface temperature patterns on the marine boundary layer and free troposphere: a study using the atmospheric ARPEGE model

    Science.gov (United States)

    Piazza, Marie; Terray, Laurent; Boé, Julien; Maisonnave, Eric; Sanchez-Gomez, Emilia

    2016-03-01

    A high-resolution global atmospheric model is used to investigate the influence of the representation of small-scale North Atlantic sea surface temperature (SST) patterns on the atmosphere during boreal winter. Two ensembles of forced simulations are performed and compared. In the first ensemble (HRES), the full spatial resolution of the SST is maintained while small-scale features are smoothed out in the Gulf Stream region for the second ensemble (SMTH). The model shows a reasonable climatology in term of large-scale circulation and air-sea interaction coefficient when compared to reanalyses and satellite observations, respectively. The impact of small-scale SST patterns as depicted by differences between HRES and SMTH shows a strong meso-scale local mean response in terms of surface heat fluxes, convective precipitation, and to a lesser extent cloudiness. The main mechanism behind these statistical differences is that of a simple hydrostatic pressure adjustment related to increased SST and marine atmospheric boundary layer temperature gradient along the North Atlantic SST front. The model response to small-scale SST patterns also includes remote large-scale effects: upper tropospheric winds show a decrease downstream of the eddy-driven jet maxima over the central North Atlantic, while the subtropical jet exhibits a significant northward shift in particular over the eastern Mediterranean region. Significant changes are simulated in regard to the North Atlantic storm track, such as a southward shift of the storm density off the coast of North America towards the maximum SST gradient. A storm density decrease is also depicted over Greenland and the Nordic seas while a significant increase is seen over the northern part of the Mediterranean basin. Changes in Rossby wave breaking frequencies and weather regimes spatial patterns are shown to be associated to the jets and storm track changes.

  7. Variability of refractivity in the surface layer

    OpenAIRE

    Mabey, Deborah L.

    2002-01-01

    The author and members of the Boundary Layer Studies Group collected atmospheric surface layer profile properties affecting RF propagation during the Roughness and Evaporation Duct experiment off the windward coast of Oahu. We measured temperature, humidity and pressure profiles from the surface and up to 100 m by multi-level buoy-mounted sensors and a rawinsonde attached to a kite flown from a small vessel. We obtained the profiles concurrently with S-, X- and Ku-Band propagation measurement...

  8. Quantifying Aerial Concentrations of Maize Pollen in the Atmospheric Surface Layer Using Remote-Piloted Airplanes and Lagrangian Stochastic Modeling

    Science.gov (United States)

    Aylor, Donald E.; Boehm, Matthew T.; Shields, Elson J.

    2006-07-01

    The extensive adoption of genetically modified crops has led to a need to understand better the dispersal of pollen in the atmosphere because of the potential for unwanted movement of genetic traits via pollen flow in the environment. The aerial dispersal of maize pollen was studied by comparing the results of a Lagrangian stochastic (LS) model with pollen concentration measurements made over cornfields using a combination of tower-based rotorod samplers and airborne radio-controlled remote-piloted vehicles (RPVs) outfitted with remotely operated pollen samplers. The comparison between model and measurements was conducted in two steps. In the first step, the LS model was used in combination with the rotorod samplers to estimate the pollen release rate Q for each sampling period. In the second step, a modeled value for the concentration Cmodel, corresponding to each RPV measured value Cmeasure, was calculated by simulating the RPV flight path through the LS model pollen plume corresponding to the atmospheric conditions, field geometry, wind direction, and source strength. The geometric mean and geometric standard deviation of the ratio Cmodel/Cmeasure over all of the sampling periods, except those determined to be upwind of the field, were 1.42 and 4.53, respectively, and the lognormal distribution corresponding to these values was found to fit closely the PDF of Cmodel/Cmeasure. Model output was sensitive to the turbulence parameters, with a factor-of-100 difference in the average value of Cmodel over the range of values encountered during the experiment. In comparison with this large potential variability, it is concluded that the average factor of 1.4 between Cmodel and Cmeasure found here indicates that the LS model is capable of accurately predicting, on average, concentrations over a range of atmospheric conditions.

  9. Momentum and buoyancy transfer in atmospheric turbulent boundary layer over wavy water surface - Part 1: Harmonic wave

    OpenAIRE

    Troitskaya, Yu. I.; Ezhova, E. V.; Zilitinkevich, S. S.

    2013-01-01

    The surface-drag and mass-transfer coefficients are determined within a self-consistent problem of wave-induced perturbations and mean fields of velocity and density in the air, using a quasi-linear model based on the Reynolds equations with down-gradient turbulence closure. Investigation of a harmonic wave propagating along the wind has disclosed that the surface drag is generally larger for shorter waves. This effect is more pronounced in the unstable and neutral stratification. The stable ...

  10. The Estimation Surface Latent Heat Flux Over the Ocean and its Relationship to Marine Atmospheric Boundary Layer (MABL) Structure

    Science.gov (United States)

    Palm, Stephen P.; Schwemmer, Geary K.; Vandemark, Doug; Evans, Keith; Miller, David O.

    1999-01-01

    A new technique combining active and passive remote sensing instruments for the estimation of surface latent heat flux over the ocean is presented. This synergistic method utilizes aerosol lidar backscatter data, multi-channel infrared radiometer data and microwave scatterometer data acquired onboard the NASA P-3B research aircraft during an extended field campaign over the Atlantic ocean in support of the Lidar In-space Technology Experiment (LITE) in September of 1994. The 10 meter wind speed derived from the scatterometers and the lidar-radiometer inferred near-surface moisture are used to obtain an estimate of the surface flux of moisture via bulk aerodynamic formulae. The results are compared with the Special Sensor Microwave Imager (SSM/I) daily average latent heat flux and show reasonable agreement. However, the SSM/I values are biased high by about 30 W/sq m. In addition, the MABL height, entrainment zone thickness and integrated lidar backscatter intensity are computed from the lidar data and compared with the magnitude of the surface fluxes. The results show that the surface latent heat flux is most strongly correlated with entrainment zone top, bottom and the integrated MABL lidar backscatter, with corresponding correlation coefficients of 0.62, 0.67 and 0.61, respectively.

  11. Momentum and buoyancy transfer in atmospheric turbulent boundary layer over wavy water surface – Part 1: Harmonic wave

    Directory of Open Access Journals (Sweden)

    Yu. I. Troitskaya

    2013-10-01

    Full Text Available The surface-drag and mass-transfer coefficients are determined within a self-consistent problem of wave-induced perturbations and mean fields of velocity and density in the air, using a quasi-linear model based on the Reynolds equations with down-gradient turbulence closure. Investigation of a harmonic wave propagating along the wind has disclosed that the surface drag is generally larger for shorter waves. This effect is more pronounced in the unstable and neutral stratification. The stable stratification suppresses turbulence, which leads to weakening of the momentum and mass transfer.

  12. On Monin–Obukhov Scaling in and Above the Atmospheric Surface Layer: The Complexities of Elevated Scintillometer Measurements

    NARCIS (Netherlands)

    Braam, M.; Bosveld, F.C.; Moene, A.F.

    2012-01-01

    In scintillometry Monin–Obukhov similarity theory (MOST) is used to calculate the surface sensible heat flux from the structure parameter of temperature (CT2)(CT2) . In order to prevent saturation a scintillometer can be installed at an elevated level. However, in that case the observation level mig

  13. Simulation of aerosol substance transfer in the atmospheric boundary layer

    Science.gov (United States)

    Lezhenin, A. A.; Raputa, V. F.; Shlychkov, V. Ð. ń.

    2014-11-01

    A model for the reconstruction of the surface concentration of a heavy non-homogeneous substance transfered in the atmosphere is proposed. The model is used to simulate the snow surface contamination by benzo(a)pyren in the vicinity of Power Station-3 in the city of Barnaul. The effects of wind rotation in the atmospheric boundary layer on the field of long-term aerosol substance are assessed.

  14. 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 im

  15. CFD Modeling of Non-Neutral Atmospheric Boundary Layer Conditions

    DEFF Research Database (Denmark)

    Koblitz, Tilman

    For wind resource assessment, the wind industry is increasingly relying on Computational Fluid Dynamics models that focus on modeling the airflow in a neutrally stratified surface-layer. Physical processes like the Coriolis force, buoyancy forces and heat transport, that are important to the...... atmospheric boundary-layer, are mostly ignored so far. In order to decrease the uncertainty of wind resource assessment, the present work focuses on atmospheric flows that include atmospheric stability and the Coriolis effect. Within the present work a RANS model framework is developed and implemented into...

  16. Impact of storm-induced cooling of sea surface temperature on large turbulent eddies and vertical turbulent transport in the atmospheric boundary layer of Hurricane Isaac

    Science.gov (United States)

    Zhu, Ping; Wang, Yuting; Chen, Shuyi S.; Curcic, Milan; Gao, Cen

    2016-01-01

    Roll vortices in the atmospheric boundary layer (ABL) are important to oil operation and oil spill transport. This study investigates the impact of storm-induced sea surface temperature (SST) cooling on the roll vortices generated by the convective and dynamic instability in the ABL of Hurricane Isaac (2012) and the roll induced transport using hindcasting large eddy simulations (LESs) configured from the multiply nested Weather Research & Forecasting model. Two experiments are performed: one forced by the Unified Wave INterface - Coupled Model and the other with the SST replaced by the NCEP FNL analysis that does not include the storm-induced SST cooling. The simulations show that the roll vortices are the prevalent eddy circulations in the ABL of Isaac. The storm-induced SST cooling causes the ABL stability falls in a range that satisfies the empirical criterion of roll generation by dynamic instability, whereas the ABL stability without considering the storm-induced SST cooling meets the criterion of roll generation by convective instability. The ABL roll is skewed and the increase of convective instability enhances the skewness. Large convective instability leads to large vertical transport of heat and moisture; whereas the dominant dynamic instability results in large turbulent kinetic energy but relatively weak heat and moisture transport. This study suggests that failure to consider roll vortices or incorrect initiation of dynamic and convective instability of rolls in simulations may substantially affect the transport of momentum, energy, and pollutants in the ABL and the dispersion/advection of oil spill fume at the ocean surface.

  17. Numerical modelling of the atmospheric mixing-layer diurnal evolution

    International Nuclear Information System (INIS)

    This paper introduce a numeric procedure to determine the temporal evolution of the height, potential temperature and mixing ratio in the atmospheric mixing layer. The time and spatial derivatives were evaluated via forward in time scheme to predict the local evolution of the mixing-layer parameters, and a forward in time, upstream in space scheme to predict the evolution of the mixing-layer over a flat region with a one-dimensional advection component. The surface turbulent fluxes of sensible and latent heat were expressed using a simple sine wave that is function of the hour day and kind of the surface (water or country). (author)

  18. Surface strains in iron oxide heterogeneous layer

    International Nuclear Information System (INIS)

    Recently the oxidation study at high temperature, have been glance to examine the influence of the surface strains. The samples of the pure iron were oxidized among 850 and 1050 deg C, under argon-water vapor atmosphere. The oxide layer was analyzed by optics and scanning electrons microscopy, and X-ray diffraction. The results showed a heterogeneous layer consisting of three distinct oxides. On the other hand it was possible to observe the presence of the strains on the mentioned layer. (author)

  19. Atmospheric Boundary Layer Characteristics during BOBMEX-Pilot Experiment

    Indian Academy of Sciences (India)

    G S Bhat; S Ameenulla; M Venkataramana; K Sengupta

    2000-06-01

    The atmospheric boundary layer characteristics observed during the BOBMEX-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 structure of the atmosphere. The study area was convectively active, the SSTs were high, surface air was warm and moist, and the surface air moist static energy was among the highest observed over the tropical oceans. The mean sea air temperature difference was about 1.25°C and the sea skin temperature was cooler than bucket SST by 0.5°C. The atmospheric mixed layer was shallow, fluctuated in response to synoptic conditions from 100 m to 900 m with a mean around 500 m.

  20. Coupled groundwater-atmosphere modeling: effects on atmospheric boundary layer development

    Science.gov (United States)

    Chow, F. K.; Maxwell, R. M.; Kollet, S. J.; Daniels, M. H.; Rihani, J. F.

    2007-12-01

    Newly-developed coupled land-atmosphere models which incorporate both subsurface and atmospheric moisture dynamics have the potential to change our understanding of the hydrologic cycle. This presentation describes the effects of coupled groundwater-atmosphere modeling on simulations of the atmospheric boundary layer. Both field observations and simulations indicate strong sensitivity of atmospheric dynamics to land-surface conditions, in particular surface soil moisture. Simulations of atmospheric flow in Owens Valley (California) and in the Riviera Valley (Switzerland) show strong sensitivity to land-surface conditions, thus motivating the need for more accurate representations of soil moisture. In addition to influences from weather and seasonal changes, soil moisture dynamics respond to diurnal heat fluxes on the land surface. Using our new fully-coupled groundwater-atmosphere model, we have demonstrated correlations of soil moisture and land-surface heat fluxes with groundwater fluctuations on short, diurnal time scales. By explicitly calculating groundwater dynamics for our domain of interest, we are able to produce realistic time- and space-varying soil moisture distributions that naturally correspond to variations in topography and surface evaporation. Simulations in idealized and real watersheds are shown to illustrate these effects. The observed variations in surface moisture distribution have large impacts on the moisture and temperature structure in the atmosphere, leading to changes in boundary layer depth and convective motions as compared to standard soil moisture representations. Our coupled model framework will allow detailed investigation of the complex cycle of land-atmosphere processes affecting moisture distributions in the subsurface and the atmosphere.

  1. Uncertainties in Surface Layer Modeling

    Science.gov (United States)

    Pendergrass, W.

    2015-12-01

    A central problem for micrometeorologists has been the relationship of air-surface exchange rates of momentum and heat to quantities that can be predicted with confidence. The flux-gradient profile developed through Monin-Obukhov Similarity Theory (MOST) provides an integration of the dimensionless wind shear expression where is an empirically derived expression for stable and unstable atmospheric conditions. Empirically derived expressions are far from universally accepted (Garratt, 1992, Table A5). Regardless of what form of these relationships might be used, their significance over any short period of time is questionable since all of these relationships between fluxes and gradients apply to averages that might rarely occur. It is well accepted that the assumption of stationarity and homogeneity do not reflect the true chaotic nature of the processes that control the variables considered in these relationships, with the net consequence that the levels of predictability theoretically attainable might never be realized in practice. This matter is of direct relevance to modern prognostic models which construct forecasts by assuming the universal applicability of relationships among averages for the lower atmosphere, which rarely maintains an average state. Under a Cooperative research and Development Agreement between NOAA and Duke Energy Generation, NOAA/ATDD conducted atmospheric boundary layer (ABL) research using Duke renewable energy sites as research testbeds. One aspect of this research has been the evaluation of legacy flux-gradient formulations (the ϕ functions, see Monin and Obukhov, 1954) for the exchange of heat and momentum. At the Duke Energy Ocotillo site, NOAA/ATDD installed sonic anemometers reporting wind and temperature fluctuations at 10Hz at eight elevations. From these observations, ϕM and ϕH were derived from a two-year database of mean and turbulent wind and temperature observations. From this extensive measurement database, using a

  2. Modelling land surface - atmosphere interactions

    DEFF Research Database (Denmark)

    Rasmussen, Søren Højmark

    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...

  3. Numerical Simulation of the Atmospheric Boundary Layer

    Czech Academy of Sciences Publication Activity Database

    Bauer, Petr

    Praha : Česká technika - nakladatelství ČVUT, 2006 - (Ambrož, P.; Masáková, Z.), s. 11-18 [Doktorandské dny 2006. Katedra matematiky FJFI ČVUT, Praha (CZ), 10.11.2006-24.11.2006] Institutional research plan: CEZ:AV0Z20760514 Keywords : atmospheric boundary layer * numerical simulation * finite element method Subject RIV: DI - Air Pollution ; Quality

  4. 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.

  5. Turbulence Scales Simulations in Atmospheric Boundary Layer Wind Tunnels

    OpenAIRE

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

    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...

  6. 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

    periods of analysis, that under both barotropic and baroclinic conditions, the model predicts the gradient and geostrophic wind well, explaining for a particular case an 'unusual' backing of the wind. The observed conditions at the surface, on the other hand, explain the differences in wind veering. The......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...... simulated winds underpredict the turning of the wind and the boundary-layer winds in general....

  7. Optimized Estimation of Surface Layer Characteristics from Profiling Measurements

    OpenAIRE

    Doreene Kang; Qing Wang

    2016-01-01

    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 fluxe...

  8. Simulation of atmospheric turbulence layers with phase screens by JAVA

    Science.gov (United States)

    Zhang, Xiaofang; Chen, Wenqin; Yu, Xin; Yan, Jixiang

    2008-03-01

    In multiconjugate Adaptive Optics (MCAO), the phase screens are used to simulate atmospheric turbulence layers to study the optimal turbulence delamination and the determination of layer boundary position. In this paper, the method of power spectrum inversion and sub-harmonic compensation were used to simulate atmospheric turbulence layers and results can be shown by grey map. The simulation results showed that, with the increase of turbulence layers, the RMS of adaptive system decreased, but the amplitude diminished. So the atmospheric turbulence can be split into 2-3 layers and be modeled by phase screens. Otherwise, a small simulation atmospheric turbulence delamination system was realized by JAVA.

  9. Behaviour of tracer diffusion in simple atmospheric boundary layer models

    Directory of Open Access Journals (Sweden)

    P. S. Anderson

    2007-10-01

    Full Text Available 1-D profiles and time series from an idealised atmospheric boundary layer model are presented, which show agreement with boundary layer measurements of polar NOx. Diffusion models are increasingly being used as the framework for studying tropospheric air chemistry dynamics. Models based on standard boundary layer diffusivity profiles have an intrinsic behaviour that is not necessarily intuitive, due to the variation of turbulent diffusivity with height. The simple model presented captures the essence of the evolution of a trace gas released at the surface, and thereby provides both a programming and a conceptual tool in the analysis of observed trace gas evolution. A time scale inherent in the model can be tuned by fitting model time series to observations. This scale is then applicable to the more physically simple but chemically complex zeroth order or box models of chemical interactions.

  10. Clear-air radar observations of the atmospheric boundary layer

    Science.gov (United States)

    Ince, Turker

    2001-10-01

    This dissertation presents the design and operation of a high-resolution frequency-modulated continuous-wave (FM- CW) radar system to study the structure and dynamics of clear-air turbulence in the atmospheric boundary layer (ABL). This sensitive radar can image the vertical structure of the ABL with both high spatial and temporal resolutions, and provide both qualitative information about the morphology of clear-air structures and quantitative information on the intensity of fluctuations in refractive-index of air. The principles of operation and the hardware and data acquisition characteristics of the radar are described in the dissertation. In October 1999, the radar participated in the Cooperative Atmosphere-Surface Exchange Study (CASES'99) Experiment to characterize the temporal structure and evolution of the boundary-layer features in both convective and stable conditions. The observed structures include clear-air convection, boundary layer evolution, gravity waves, Kelvin-Helmholtz instabilities, stably stratified layers, and clear-air turbulence. Many of the S-band radar images also show high- reflectivity returns from Rayleigh scatterers such as insects. An adaptive median filtering technique based on local statistics has, therefore, been developed to discriminate between Bragg and Rayleigh scattering in clear-air radar observations. The filter is tested on radar observations of clear air convection with comparison to two commonly used image processing techniques. The dissertation also examines the statistical mean of the radar-measured C2n for clear-air convection, and compares it with the theoretical predictions. The study also shows that the inversion height, local thickness of the inversion layer, and the height of the elevated atmospheric layers can be estimated from the radar reflectivity measurements. In addition, comparisons to the radiosonde-based height estimates are made. To examine the temporal and spatial structure of C2n , the dissertation

  11. The height of the atmospheric boundary layer during unstable conditions

    Energy Technology Data Exchange (ETDEWEB)

    Gryning, S.E.

    2005-11-01

    The height of the convective atmospheric boundary layer, also called the mixed-layer, is one of the fundamental parameters that characterise the structure of the atmosphere near the ground. It has many theoretical and practical applications such as the prediction of air pollution concentrations, surface temperature and the scaling of turbulence. However, as pointed out by Builtjes (2001) in a review paper on Major Twentieth Century Milestones in Air Pollution Modelling and Its Application, the weakest point in meteorology data is still the determination of the height of the mixed-layer, the so-called mixing height. A simple applied model for the height of the mixed-layer over homogeneous terrain is suggested in chapter 2. It is based on a parameterised budget for the turbulent kinetic energy. In the model basically three terms - the spin-up term and the production of mechanical and convective turbulent kinetic energy - control the growth of the mixed layer. The interplay between the three terms is related to the meteorological conditions and the height of the mixed layer. A stable layer, the so-called entrainment zone, which is confined between the mixed layer and the free air above, caps the mixed layer. A parameterisation of the depth of the entrainment zone is also suggested, and used to devise a combined model for the height of the mixed layer and the entrainment zone. Another important aspect of the mixed layer development exists in coastal areas where an internal boundary layer forms downwind from the coastline. A model for the growth of the internal boundary layer is developed in analogy with the model for mixed layer development over homogeneous terrain. The strength of this model is that it can operate on a very fine spatial resolution with minor computer resources. Chapter 3 deals with the validation of the models. It is based in parts on data from the literature, and on own measurements. For the validation of the formation of the internal boundary layer

  12. Effects of Vegetation on Subsurface-Surface-Atmosphere interactions

    Science.gov (United States)

    Lu, Yen-Sen; Rihani, Jehan; Langensiepen, Matthias; Simmer, Clemens

    2013-04-01

    The aim of this project is to investigate the effect of vegetation on the coupling between groundwater, surface energy fluxes, and the atmospheric boundary layer. Literature demonstrates that conditions at the land surface can affect water table dynamics and development of the atmospheric boundary layer. Leaf Area Index (LAI) in particular is shown to have an important effect on land surface processes such as interception, albedo, evaporation, and transpiration. In this work, we perform a sensitivity analysis on a range of LAI values within a real catchment to investigate the role of vegetation on transition zones of strongest coupling between water table and energy fluxes at the land surface on one hand, and between water table dynamics and the atmospheric boundary layer on the other hand. In the first phase of this work, integrated groundwater-surface water simulations using the coupled model ParFlow-CLM are performed for different LAI values. These will be based on ranges obtained from observations for specific vegetation types within the real catchment. The subsurface-surface simulations are used to obtain the equilibrium soil moisture field given a specific set of atmospheric forcing conditions. Furthermore, results are analyzed to investigate LAI effects on the hydrologic and energy balance at the land surface, and how this affects the regions and times of strongest feedbacks between energy fluxes and water table depth. In the second phase, the equilibrium soil moisture field obtained from ParFlow-CLM will be used to initialize a second set of sensitivity analysis simulations using the fully coupled subsurface-surface-atmospheric model ParFlow-CLM-COSMO. Results will help draw conclusions on which regions within a watershed exhibit stronger vegetation effects on the two-way feedbacks between water table and atmospheric boundary layer on both diurnal and seasonal timescales.

  13. Friction contact mechanisms of layered surface

    Institute of Scientific and Technical Information of China (English)

    Fan Xue; Diao Dongfeng

    2013-01-01

    In this paper,we firstly review the carbon layered surface prepared with electron cyclotron resonance (ECR) plasma sputtering.Secondly,the friction behavior of carbon layered surface under pin-on-disk testing is described.Furthermore,the contact stress evolution processes of layered surface with and without transfer layer during wear are given for understanding the contact mechanisms.Finally,a three-dimension (3D) local yield map of layered surface is introduced,which is useful to predict the possible contact mechanisms.

  14. The influence of the mechanisms of transfer in carburizing atmospheres on the surface metal layer; Einfluss der Uebertragungsmechanismen von Aufkohlungsatmosphaeren auf die Metallrandschicht

    Energy Technology Data Exchange (ETDEWEB)

    Kuehn, F. [LOI Thermprocess GmbH, Essen (Germany)

    1996-12-01

    The influence of the mechanism of transfer in carburizing atmospheres is discussed using examples of carburization. It became apparent that a direct relationship between mass transfer and the product of partial pressures p{sub CO}xp{sub H2} could not be disproved, since the H{sub 2} content of the atmospheres had not been stated. (orig.) [Deutsch] Der Einfluss der Uebertragungsmechanismen von Aufkohlungsatmosphaeren an Aufkohlungsbeispielen wird diskutiert. Dabei stellte sich heraus, dass die direkte Abhaengigkeit des Stoffueberganges vom Partialdruckprodukt p{sub CO}xp{sub H2} nicht widerlegt werden konnte, zumal der H{sub 2}-Gehalt der Atmosphaeren nicht genannt wurde. (orig.)

  15. 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

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

    DEFF Research Database (Denmark)

    Koblitz, Tilman; Bechmann, Andreas; Sogachev, Andrey;

    2015-01-01

    For wind resource assessment, the wind industry is increasingly relying on computational fluid dynamics models of the neutrally stratified surface-layer. So far, physical processes that are important to the whole atmospheric boundary-layer, such as the Coriolis effect, buoyancy forces and heat...... 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...

  17. Using a Modified Soil-Plant-Atmosphere Scheme (MSPAS) to Study the Sensitivity of Land Surface and Boundary Layer Processes to Soil and Vegetation Conditions

    Institute of Scientific and Technical Information of China (English)

    刘树华; 乐旭; 刘辉志; 胡非

    2004-01-01

    A series of sensitivity tests are performed to test the stability and sensibility of the Modified Soil-PlantAtmosphere Scheme (MSPAS), which was wholly introduced in a previous paper. The numerical simulation results from the experiments show good agreement with physical reality. Besides, some of the results are illuminating. Together with the first paper, it is concluded that MSPAS is a simple but effective model,and it is practically valuable in the research work of desertification control and reforestation in China

  18. 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

  19. Similarity Relations for C_T^2 in the Unstable Atmospheric Surface Layer: Dependence on Regression Approach, Observation Height and Stability Range

    NARCIS (Netherlands)

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

    2014-01-01

    A great variety of similarity functions for the structure parameter of temperature ( C 2 T ) have been proposed in the literature. They differ in the way they were derived from the data and in the characteristics of the dataset used for their derivation (surface type, observation level, stability ra

  20. Surface-induced layer formation in polyelectrolytes

    OpenAIRE

    Solis, F. J.; de la Cruz, M. Olvera

    1998-01-01

    We analyze, by means of an RPA calculation, the conditions under which a mixture of oppositely charged polyelectrolytes can micro-segregate in the neighborhood of a charged surface creating a layered structure. A number of stable layers can be formed if the surface is sufficiently strongly charged even at temperatures at which the bulk of the mixture is homogeneous.

  1. Convection and Chemistry in the Atmospheric Boundary Layer

    OpenAIRE

    A. C. Petersen

    1999-01-01

    The earth’s troposphere is the lowest layer of the atmosphere and has a thickness of about 10 km. It is the layer that contains most of the mass (80%) of the atmosphere. All weather phenomena that we experience have their origin in the troposphere. It is the stage for some well-known environmental problems: climate change, ozone smog, and acidification. These problems are related to the trace amount of gases that are emitted into the troposphere from anthropogenic sources. Alth...

  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. Triton's surface-atmosphere energy balance

    Science.gov (United States)

    Stansberry, John A.; Yelle, Roger V.; Lunine, Jonathan I.; Mcewen, Alfred S.

    1992-01-01

    A model encompassing the turbulent transfer of sensible heat as well as insolation, reradiation, and latent heat transport is presently used to investigate the energetics of the surface-atmosphere system of Triton. Under the assumption of a physically plausible range of heat transfer coefficients, the atmospheric temperature 1 km above the surface is found to be 1-3 K hotter than the Triton surface. The observed N2 frosts must have an emissivity lower than unity in order to match a frost temperature at the surface of about 38 K.

  4. Water molecules orientation in surface layer

    Science.gov (United States)

    Klingo, V. V.

    2000-08-01

    The water molecules orientation has been investigated theoretically in the water surface layer. The surface molecule orientation is determined by the direction of a molecule dipole moment in relation to outward normal to the water surface. Entropy expressions of the superficial molecules in statistical meaning and from thermodynamical approach to a liquid surface tension have been found. The molecules share directed opposite to the outward normal that is hydrogen protons inside is equal 51.6%. 48.4% water molecules are directed along to surface outward normal that is by oxygen inside. A potential jump at the water surface layer amounts about 0.2 volts.

  5. On the modeling of electrical boundary layer (electrode layer) and derivation of atmospheric electrical profiles, eddy diffusion coeffcient and scales of electrode layer

    Indian Academy of Sciences (India)

    Madhuri N Kulkarni

    2010-02-01

    Electrode layer or electrical boundary layer is one of the charge generators in the global atmospheric electric circuit. In spite of this we find very few model studies and few measurements of it in the literature. Using a new technique it is shown that in this layer, the space charge density varies exponentially in vertical. A new experimental method based on the surface measurements is discussed to determine all the characteristic scales and an average electrical and meteorological state of an electrode layer. The results obtained are in good agreement with the previous studies. So, it is suggested that an exponential space charge density profile will no longer be an assumption in the case of electrode layer studies. The profiles of atmospheric electric field and electrical conductivity are also derived and a new term named as electrode layer constant is introduced.

  6. Producing of multicomponent and composite surface layers

    International Nuclear Information System (INIS)

    The paper presents a new method of producing multicomponent and composite layers on steel substrate. The combination of nickel plating with glow-discharge bordering or impulse-plasma deposition method gives an opportunity to obtain good properties of surface layers. The results of examinations of carbon 45 (0.45%C) steel, nickel plated and then borided under glow discharge conditions or covered with TiN layers are presented. The corrosion and friction wear resistance of such layers are markedly higher than for layer produced on non nickel plated substrates. (author). 19 refs, 5 figs

  7. Contaminated concrete surface layer removal

    International Nuclear Information System (INIS)

    Equipment is being developed to economically remove contaminated concrete surfaces in nuclear facilities. To be effective this equipment should minimize personnel radiation exposure, minimize the volume of material removed, and perform the operation quickly with the least amount of energy. Several methods for removing concrete surfaces are evaluated for use in decontaminating such facilities. Two unique methods especially suited for decontamination are described: one, the water cannon, is a device that fires a high-velocity jet of fluid causing spallation of the concrete surface; the other, a concrete spaller, is a tool that exerts radial pressure agains the sides of a pre-dilled shallow cylindrical hole causing spallation to occur. Each method includes a means for containing airborne contamination. Results of tests show that these techniques can rapidly and economically remove surfaces, and leave minimal rubble for controlled disposal

  8. Inhomogeneities in molecular layers of Mira atmospheres

    CERN Document Server

    Wittkowski, M; Ireland, M; Karovicova, I; Ohnaka, K; Scholz, M; van Wyk, F; Whitelock, P; Wood, P R; Zijlstra, A A

    2011-01-01

    We obtained K-band spectro-interferometric observations of the Miras R Cnc, X Hya, W Vel, and RW Vel with a spectral resolution of 1500 using the VLTI/AMBER instrument. We obtained concurrent JHKL photometry using the the Mk II instrument at the SAAO. Our sources have wavelength-dependent visibility values that are consistent with earlier low-resolution AMBER observations of S Ori and with the predictions of dynamic model atmosphere series based on self-excited pulsation models. The wavelength-dependent UD diameters show a minimum near the near-continuum bandpass at 2.25 um. They increase by up to 30% toward the H2O band at 2.0 um and by up to 70% at the CO bandheads. The dynamic model atmosphere series show a consistent wavelength-dependence, and their parameters such as the visual phase, effective temperature, and distances are consistent with independent estimates. The closure phases have significantly wavelength-dependent non-zero values indicating deviations from point symmetry. For example, the R Cnc cl...

  9. Triton's surface-atmosphere energy balance

    Science.gov (United States)

    Stansberry, J.A.; Yelle, R.V.; Lunine, J.I.; McEwen, A.S.

    1992-01-01

    We explore the energetics of Triton's surface-atmosphere system using a model that includes the turbulent transfer of sensible heat as well as insolation, reradiation, and latent heat transport. The model relies on a 1?? by 1?? resolution hemispheric bolometric albedo map of Triton for determining the atmospheric temperature, the N2 frost emissivity, and the temperatures of unfrosted portions of the surface consistent with a frost temperature of ???38 K. For a physically plausible range of heat transfer coefficients, we find that the atmospheric temperature roughly 1 km above the surface is approximately 1 to 3 K hotter than the surface. Atmospheric temperatures of 48 K suggested by early analysis of radio occultation data cannot be obtained for plausible values of the heat transfer coefficients. Our calculations indicate that Triton's N2 frosts must have an emissivity well below unity in order to have a temperature of ???38 K, consistent with previous results. We also find that convection over small hot spots does not significantly cool them off, so they may be able to act as continous sources of buoyancy for convective plumes, but have not explored whether the convection is vigorous enough to entrain particulate matter thereby forming a dust devil. Our elevated atmospheric temperatures make geyser driven plumes with initial upward velocities ???10 m s-1 stagnate in the lower atmosphere. These "wimpy" plumes provide a possible explanation for Triton's "wind streaks.". ?? 1992.

  10. Surface layer similarity in the nocturnal boundary layer: the application of Hilbert-Huang transform

    Directory of Open Access Journals (Sweden)

    J. Hong

    2009-10-01

    Full Text Available Turbulence statistics such as flux-variance relationship is critical information in measuring and modeling carbon, water, energy, and momentum exchanges at the biosphere-atmosphere interface. Using a recently proposed mathematical technique, the Hilbert-Huang transform (HHT, this study highlights its possibility to quantify impacts of non-turbulent flows on turbulence statistics in the stable surface layer. The HHT is suitable for the analysis of non-stationary and intermittent data and thus very useful for better understanding of the interplay of the surface layer similarity with complex nocturnal environment. Our analysis showed that the HHT can successfully sift non-turbulent components and be used as a tool to estimate the relationships between turbulence statistics and atmospheric stability in complex environment such as nocturnal stable boundary layer.

  11. Surface layer similarity in the nocturnal boundary layer: the application of Hilbert-Huang transform

    Directory of Open Access Journals (Sweden)

    J. Hong

    2010-04-01

    Full Text Available Turbulence statistics such as flux-variance relationship are critical information in measuring and modeling ecosystem exchanges of carbon, water, energy, and momentum at the biosphere-atmosphere interface. Using a recently proposed mathematical technique, the Hilbert-Huang transform (HHT, this study highlights its possibility to quantify impacts of non-turbulent flows on turbulence statistics in the stable surface layer. The HHT is suitable for the analysis of non-stationary and intermittent data and thus very useful for better understanding the interplay of the surface layer similarity with complex nocturnal environment. Our analysis showed that the HHT can successfully sift non-turbulent components and be used as a tool to estimate the relationships between turbulence statistics and atmospheric stability in complex environments such as nocturnal stable boundary layer.

  12. Stable water layers on solid surfaces.

    Science.gov (United States)

    Hong, Ying-Jhan; Tai, Lin-Ai; Chen, Hung-Jen; Chang, Pin; Yang, Chung-Shi; Yew, Tri-Rung

    2016-02-17

    Liquid layers adhered to solid surfaces and that are in equilibrium with the vapor phase are common in printing, coating, and washing processes as well as in alveoli in lungs and in stomata in leaves. For such a liquid layer in equilibrium with the vapor it faces, it has been generally believed that, aside from liquid lumps, only a very thin layer of the liquid, i.e., with a thickness of only a few nanometers, is held onto the surface of the solid, and that this adhesion is due to van der Waals forces. A similar layer of water can remain on the surface of a wall of a microchannel after evaporation of bulk water creates a void in the channel, but the thickness of such a water layer has not yet been well characterized. Herein we showed such a water layer adhered to a microchannel wall to be 100 to 170 nm thick and stable against surface tension. The water layer thickness was measured using electron energy loss spectroscopy (EELS), and the water layer structure was characterized by using a quantitative nanoparticle counting technique. This thickness was found for channel gap heights ranging from 1 to 5 μm. Once formed, the water layers in the microchannel, when sealed, were stable for at least one week without any special care. Our results indicate that the water layer forms naturally and is closely associated only with the surface to which it adheres. Our study of naturally formed, stable water layers may shed light on topics from gas exchange in alveoli in biology to the post-wet-process control in the semiconductor industry. We anticipate our report to be a starting point for more detailed research and understanding of the microfluidics, mechanisms and applications of gas-liquid-solid systems. PMID:26856872

  13. Implementation of a boundary layer heat flux parameterization into the Regional Atmospheric Modeling System (RAMS

    Directory of Open Access Journals (Sweden)

    E. L. McGrath-Spangler

    2008-07-01

    Full Text Available The response of atmospheric carbon dioxide to a given amount of surface flux is inversely proportional to the depth of the boundary layer. Overshooting thermals that entrain free tropospheric air down into the boundary layer modify the characteristics and depth of the lower layer through the insertion of energy and mass. This alters the surface energy budget by changing the Bowen ratio and thereby altering the vegetative response and the surface boundary conditions. Although overshooting thermals are important in the physical world, their effects are unresolved in most regional models. A parameterization to include the effects of boundary layer entrainment was introduced into a coupled ecosystem-atmosphere model (SiB-RAMS. The parameterization is based on a downward heat flux at the top of the boundary layer that is proportional to the heat flux at the surface. Results with the parameterization show that the boundary layer simulated is deeper, warmer, and drier than when the parameterization is turned off. These results alter the vegetative stress factors thereby changing the carbon flux from the surface. The combination of this and the deeper boundary layer change the concentration of carbon dioxide in the boundary layer.

  14. Europa's near-surface O2 atmosphere

    Science.gov (United States)

    Cassidy, T. A.; Johnson, R. E.

    The surfaces of 'airless' bodies in our solar system are covered by porous regoliths; granular, porous surfaces generated by micrometeor impact. Europa's tenuous neutral atmosphere (composed primarily of O2 ) is generated by UV and plasma irradiation of, and sublimation from, this regolith. Hubble Space Telescope (HST) observation by McGrath et al. (2004) suggested that Europa's O2 atmosphere is spatially nonuniform. Previous simulations (e.g. Shematovich et al., Icarus, 2005), which assumed that O2 could only be lost by pickup and escape, found that a spatially nonuniform source could not produce the morphology suggested by the HST observations. It is shown here that a nonuniform surface/O2 interaction, treated here as surface reactivity, results in a spatially nonuniform O2 atmosphere with the highest column density above the regions of lowest reactivity. We can reproduce this nonuniformity even with very slight reactivity. Slight reactivity makes a difference because of the many interactions an O2 molecule experiences with the surface during its lifetime; for which there are two reasons: (1) the many returns to the surface experienced by a thermal molecule; desorption followed by ballistic arc followed by desorption and so on. (2) the regolith structure: each time an O2 molecule returns to the surface it interacts not just once, but many times due to the porous nature of the regolith (Cassidy and Johnson, Icarus, 2005). Thus, in addition to the atmosphere above the surface, there is a substantial amount of gas in the porous regolith. This "regolith atmosphere" may resolve a question surrounding CO2 condensed on Europa's surface.

  15. 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

  16. Layering of ionic liquids on rough surfaces

    Science.gov (United States)

    Sheehan, Alexis; Jurado, L. Andres; Ramakrishna, Shivaprakash N.; Arcifa, Andrea; Rossi, Antonella; Spencer, Nicholas D.; Espinosa-Marzal, Rosa M.

    2016-02-01

    Understanding the behavior of ionic liquids (ILs) either confined between rough surfaces or in rough nanoscale pores is of great relevance to extend studies performed on ideally flat surfaces to real applications. In this work we have performed an extensive investigation of the structural forces between two surfaces with well-defined roughness (force microscopy. Statistical studies of the measured layer thicknesses, layering force, and layering frequency reveal the ordered structure of the rough IL-solid interface. Our work shows that the equilibrium structure of the interfacial IL strongly depends on the topography of the contact.Understanding the behavior of ionic liquids (ILs) either confined between rough surfaces or in rough nanoscale pores is of great relevance to extend studies performed on ideally flat surfaces to real applications. In this work we have performed an extensive investigation of the structural forces between two surfaces with well-defined roughness (force microscopy. Statistical studies of the measured layer thicknesses, layering force, and layering frequency reveal the ordered structure of the rough IL-solid interface. Our work shows that the equilibrium structure of the interfacial IL strongly depends on the topography of the contact. Electronic supplementary information (ESI) available: Optimized geometries and sizes for [HMIM] Ntf2, SEM images of the smooth and rough colloids, frequency of occurrence of layering in the resolved force-distance curves for all investigated systems with [HMIM] Ntf2, layer size and layering force measured with a sharp tip on mica for the same IL, and results of the kinetics experiments. See DOI: 10.1039/c5nr07805a

  17. Combined effects of surface conditions, boundary layer dynamics and chemistry on diurnal SOA evolution

    NARCIS (Netherlands)

    Janssen, R.H.H.; Vilà-Guerau de Arellano, J.; Ganzeveld, L.N.; Kabat, P.; Jimenez, J.L.; Farmer, D.K.; Heerwaarden, van C.C.; Mammarella, I.

    2012-01-01

    We study the combined effects of land surface conditions, atmospheric boundary layer dynamics and chemistry on the diurnal evolution of biogenic secondary organic aerosol in the atmospheric boundary layer, using a model that contains the essentials of all these components. First, we evaluate the mod

  18. 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.

  19. 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 ...

  20. Impact of Different Aerosols on the Evolution of the Atmospheric Boundary Layer

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    The present work analyzes the effect of aerosols on the evolution of the atmospheric boundary layer (ABL) over Shangdianzi in Beijing.A one-dimensional ABL model and a radiative transfer scheme are incorporated to develop the structure of the ABL.The diurnal variation of the atmospheric radiative budget,atmospheric heating rate,sensible and latent heat fluxes,surface and the 2 m air temperatures as well as the ABL height,and its perturbations due to the aerosols with different single-scattering albedo (SSA) are studied by comparing the aerosol-laden atmosphere to the clean atmosphere.The results show that the absorbing aerosols cause less reduction in surface evaporation relative to that by scatting aerosols,and both surface temperature and 2 m temperature decrease from the clean atmosphere to the aerosol-laden atmosphere.The greater the aerosol absorption,the more stable the surface layer.After 12:00 am,the 2 m temperature increases for strong absorption aerosols.In the meantime,there is a slight decrease in the 2 m temperature for purely scattering aerosols due to radiative cooling.The purely scattering aerosols decrease the ABL temperature and enhance the capping inversion,further reducing the ABL height.

  1. Numerical simulation of turbulent atmospheric boundary layer flows

    Energy Technology Data Exchange (ETDEWEB)

    Bennes, L.; Bodnar, T.; Kozel, K.; Sladek, I. [Czech Technical Univ., Prague (Czech Republic). Dept. of Technical Mathematics; Fraunie, P. [Universite Toulon et du Var, La Garde (France). Lab. de Sondages Electromagnetiques de l' Environment Terrestre

    2001-07-01

    The work deals with the numerical solution of viscous turbulent steady flows in the atmospheric boundary layer including pollution propagation. For its description we use two different mathematical models: - a model based on the Reynolds averaged Navier-Stokes equations for incompressible flows - a model based on a system of boundary layer equations. These systems are completed by two transport equations for the concentration of passive pollutants and the potential temperature in conservative form, respectively, and by an algebraic turbulence model. (orig.)

  2. Review of wave-turbulence interactions in the stable atmospheric boundary layer

    OpenAIRE

    Yagüe Anguis, Carlos; otros, ...

    2015-01-01

    Flow in a stably stratified environment is characterized by anisotropic and intermittent turbulence and wavelike motions of varying amplitudes and periods. Understanding turbulence intermittency and wave-turbulence interactions in a stably stratified flow remains a challenging issue in geosciences including planetary atmospheres and oceans. The stable atmospheric boundary layer (SABL) commonly occurs when the ground surface is cooled by longwave radiation emission such as at night over land s...

  3. Fluxes and Mixing Processes in the Marine Atmospheric Boundary Layer

    OpenAIRE

    Nilsson, Erik Olof

    2013-01-01

    Atmospheric models are strongly dependent on the turbulent exchange of momentum, sensible heat and moisture (latent heat) at the surface. Oceans cover about 70% of the Earth’s surface and understanding the processes that control air-sea exchange is of great importance in order to predict weather and climate. In the atmosphere, for instance, hurricane development, cyclone intensity and track depend on these processes. Ocean waves constitute an obvious example of air-sea interaction and can cau...

  4. UK-ADMS - a new approach to modelling dispersion in the earth's atmospheric boundary layer

    International Nuclear Information System (INIS)

    The UK Atmospheric Dispersion Modelling System is described in considerable detail. The principle modules are dealt with. A key to the methodology is that vertical profiles of mean velocity, temperature and turbulence in the boundary layer depend on the relative values of the height above the ground, the height of the boundary layer, and a length scale determined by the friction velocity and the heat flux and air temperature at the surface. The models can be used at any location. (AB) (15 refs.)

  5. The role of surface waves in the ocean mixed layer

    Institute of Scientific and Technical Information of China (English)

    QIAO Fangli; YANG Yongzeng; XIA Changshui; YUAN Yeli

    2008-01-01

    Previously, most ocean circulation models have overlooked the role of the surface waves. As a result, these models have produced insufficient vertical mixing, with an under- prediction of the mixing layer (ML) depth and an over- prediction of the sea surface temperature (SST), particularly during the summer season. As the ocean surface layer determines the lower boundary conditions of the atmosphere, this deficiency has severely limited the performance of the coupled ocean-atmospheric models and hence the cli-mate studies. To overcome this shortcoming, a new parameterization for the wave effects in the ML model that will correct this sys-tematic error of insufficient mixing. The new scheme has enabled the mixing layer to deepen, the surface excessive heating to be cor-rected, and an excellent agreement with observed global climatologic data. The study indicates that the surface waves are essential for ML formation, and that they are the primer drivers of the upper ocean dynamics; therefore, they are critical for climate studies.

  6. 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...... in the boundary 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...... based on the turbine wakes and buoyancy contributions. The implemented method is capable of capturing the most important features of wakes of wind farms [2] while having the advantage of resolving the wall layer with a coarser grid than a typical required grid size for such problems. LES simulations are...

  7. Boundary Layer Flow Over a Moving Wavy Surface

    Science.gov (United States)

    Hendin, Gali; Toledo, Yaron

    2016-04-01

    Boundary Layer Flow Over a Moving Wavy Surface Gali Hendin(1), Yaron Toledo(1) January 13, 2016 (1)School of Mechanical Engineering, Tel-Aviv University, Israel Understanding the boundary layer flow over surface gravity waves is of great importance as various atmosphere-ocean processes are essentially coupled through these waves. Nevertheless, there are still significant gaps in our understanding of this complex flow behaviour. The present work investigates the fundamentals of the boundary layer air flow over progressive, small-amplitude waves. It aims to extend the well-known Blasius solution for a boundary layer over a flat plate to one over a moving wavy surface. The current analysis pro- claims the importance of the small curvature and the time-dependency as second order effects, with a meaningful impact on the similarity pattern in the first order. The air flow over the ocean surface is modelled using an outer, inviscid half-infinite flow, overlaying the viscous boundary layer above the wavy surface. The assumption of a uniform flow in the outer layer, used in former studies, is now replaced with a precise analytical solution of the potential flow over a moving wavy surface with a known celerity, wavelength and amplitude. This results in a conceptual change from former models as it shows that the pressure variations within the boundary layer cannot be neglected. In the boundary layer, time-dependent Navier-Stokes equations are formulated in a curvilinear, orthogonal coordinate system. The formulation is done in an elaborate way that presents additional, formerly neglected first-order effects, resulting from the time-varying coordinate system. The suggested time-dependent curvilinear orthogonal coordinate system introduces a platform that can also support the formulation of turbulent problems for any surface shape. In order to produce a self-similar Blasius-type solution, a small wave-steepness is assumed and a perturbation method is applied. Consequently, a

  8. 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)

  9. Robotized PTA surfacing of nanomaterial layers

    Directory of Open Access Journals (Sweden)

    A. Klimpel

    2009-12-01

    Full Text Available Purpose: of this research was to investigate the influence of heat input in robotized surfacing on quality and properties of nanomaterial layers.Design/methodology/approach: quality of single and multilayer, stringer and weave beads was assessed by abrasion resistance tests according to ASTMG65 standard, erosion resistance tests according to G76 standard, metallographic examinations and hardness tests.Findings: due to the fact that the robotized surfacing stand was used, the analysis of properties of the deposits was performed for single and multilayer, stringer and weave beads.Research limitations/implications: for complete information about tested deposits it is needed to compare deposits properties PTA surfaced with other technologies of nanomaterial layers manufacturing products.Practical implications: Results of this paper is an optimal range of parameters of surfacing of single and multilayer, stringer and weave beads of nanomaterial layers.Originality: tests, abrasion and erosion resistance tests were provided for surfacing of single and multilayer, stringer and weave beads, and the results were compared. The influence of heat input on layers properties and theirs structure was defined.

  10. 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 plasma....... The ultrasonic irradiation during the plasma treatment consistently enhanced the treatment efficiency. The principal effect of ultrasonic irradiation can be attributed to enhancing surface oxidation during plasma treatment. In addition, ultrasonic irradiation can suppress arcing, and the uniformity of...... and the material surface, and thus, many reactive species generated in the plasma can reach the surface before they are inactivated and can be efficiently utilised for surface modification. In the present work, glass fibre reinforced polyester plates were treated using a dielectric barrier discharge...

  11. 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......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......-surface values of heat, water vapor and momentum fluxes. The internal structure of the PBL is considered self-similar. This allows one to represent the interaction between the air flow and the underlying surface by means of universal heat/mass transfer and resistance laws. Numerical experiments on the diurnal...

  12. Land-Surface-Atmosphere Coupling in Observations and Models

    Directory of Open Access Journals (Sweden)

    Alan K Betts

    2009-07-01

    Full Text Available The diurnal cycle and the daily mean at the land-surface result from the coupling of many physical processes. The framework of this review is largely conceptual; looking for relationships and information in the coupling of processes in models and observations. Starting from the surface energy balance, the role of the surface and cloud albedos in the shortwave and longwave fluxes is discussed. A long-wave radiative scaling of the diurnal temperature range and the night-time boundary layer is summarized. Several aspects of the local surface energy partition are presented: the role of soilwater availability and clouds; vector methods for understanding mixed layer evolution, and the coupling between surface and boundary layer that determines the lifting condensation level. Moving to larger scales, evaporation-precipitation feedback in models is discussed; and the coupling of column water vapor, clouds and precipitation to vertical motion and moisture convergence over the Amazon. The final topic is a comparison of the ratio of surface shortwave cloud forcing to the diabatic precipitation forcing of the atmosphere in ERA-40 with observations.

  13. Simulation of sea surface temperatures with the surface heat fluxes from an atmospheric circulation model

    OpenAIRE

    Karaca, Mehmet; MÜLLER, DETLEV

    2011-01-01

    The global fields of the surface heat fluxes for the December-February period are calculated with the UCLA atmospheric circulation model (ACM). This model operates on a global grid net. The planetary boundary layer (PBL), as the decisive subsystem for the surface fluxes, is parameterized in terms of its bulk properties. For several locations in the north Atlantic, the model heat fluxes are incorporated into the forcing of a simple ocean mixed-layer (OML) model. The OML-model uses a slight gen...

  14. Robotized GMA surfacing of cermetalic layers

    OpenAIRE

    Klimpel, A; L.A. Dobrzański; T. Kik; A. Rzeźnikiewicz

    2006-01-01

    Purpose: Purpose of these researches was to investigate of influence of heat input in robotized surfacing on quality and properties of cermetalic layers.Design/methodology/approach: The quality of single and multilayer, stringer and weave beads was assessed by abrasion resistance tests according to ASTMG65 standard, erosion resistance tests according to G76 standard, metallographic examinations and hardness tests. Findings: Due to the fact that the it was used robotized surfacing stand, the a...

  15. 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

    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......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...

  16. 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

  17. The surface layer of cleaved bilayer manganites

    International Nuclear Information System (INIS)

    Recently, several informative reports have been published on spectroscopy experiments performed on cleaved surfaces of the bilayered colossal magnetoresistive manganite La2-2xSr1+2xMn2O7 (Konoto et al 2004 Phys. Rev. Lett. 93 107201, Freeland et al 2005 Nat. Mater. 4 62, Mannella et al 2005 Nature 438 474, Roennow et al 2006 Nature 440 1025). For the detailed interpretation of these results, it is of importance to know exactly which layer within the crystal structure is exposed to the surface upon cleavage. Here we combine crystal structure arguments, scanning tunnelling microscopy and x-ray photoelectron spectroscopy measurements to demonstrate that the crystals cleave between the rare-earth rock-salt oxide layers, leaving one outermost rare-earth oxide layer before the first electronically active MnO bilayer

  18. Power Absorption of High Frequency Electromagnetic Waves in a Partially Ionized Plasma Layer in Atmosphere Conditions

    Institute of Scientific and Technical Information of China (English)

    郭斌; 王晓钢

    2005-01-01

    We have studied the absorption, reflection, and transmission of electromagnetic waves in an unmagnetized uniform plasma layer covering a metal surface in atmosphere conditions.Instead of the absorption of the electromagnetic wave propagating only once in previous work on the plasma layer, a general formula of total power absorption by the plasma layer with an infinite time of reflections between the atmosphere-plasma interface and the metal surface has been derived for the first time. Effects of plasma parameters, especially the dependence of the fraction of positive ions, negative ions and electrons in plasmas on the power absorption processes are discussed. The results show that the existence of negative ions significantly reduces the power absorption of the electromagnetic wave. Absorptions of electromagnetic waves are calculated.

  19. Laboratory simulation of rotating atmospheric boundary layer flows over obstacles

    International Nuclear Information System (INIS)

    The present study fits in the frame of a research program concerning in general the dynamics of airflow in the atmospheric boundary layer and in particular the influence of terrestrial rotation on the movements of air masses interacting with natural extended obstacles (mountains). The experiment has been performed by the method of hydraulic simulation, using schematic models at reduced scale in a channel placed on a rotating platform. Only the case of a neutral atmosphere was considered; the wake of an obstacle with semi-circular section and the reciprocal interaction of two obstacles of this kind placed perpendicular to the flow were studied

  20. Ultrasound enhanced plasma surface modification at atmospheric pressure

    DEFF Research Database (Denmark)

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

    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 approximately 140 dB can reduce the thickness of a boundary gas layer between the plasma...... air are separated using a polyethylene film. The gliding arc was extended by a high speed air flow into ambient air, directed the polyester surface at an angle of approximately 30o. The ultrasonic waves were introduced vertically to the surface. After the plasma treatment using each plasma source...... without ultrasonic 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...

  1. Experimental Study of the EM Transmission Properties of the Marine Atmospheric Boundary Layer

    Science.gov (United States)

    Hristov, T.; Friehe, C.; Anderson, K.

    2003-04-01

    The propagation of electro-magnetic signals over the ocean is primarily affected by atmospheric refraction and scattering from the rough ocean surface. Wave-guides (also known as refractive ducts) occurring in the first tens of meters above the sea surface have been modeled extensively, as they influence communications. However, discrepancies between models and measurements have been detected. Here we study experimentally the structure of the atmospheric refractive index and the ocean surface statistics, pertinent to EM signals scattering. The structure and the dynamics the marine atmospheric boundary layer is profoundly affected by the ocean surface waves, which deform the mean wind flow streamlines. In the presence of gradients of the atmospheric humidity and temperature, the deformation of the streamlines displaces the sheared profiles of these quantities and leads to wave-induced fluctuations of the atmospheric refractive index. As a result, radio and optical signals propagating over the ocean encounter a semi-periodic refractive structure, which along with the turbulence can degrade signal's energy. The wave-induced fluctuations of the refractive index are unique to the oceanic environment. Their structure function does not follow the power 2/3 scaling law, valid for turbulent fluctuations, and thus their influence should be studied separately. We analyze data of atmospheric turbulence, humidity, temperature, and sea surface temperature and waves from the Rough Evaporation Duct experiment, conducted in part from the instrument platform FLIP in the open ocean North of Oahu, Hawaii.

  2. Computation of 2D stratified flows in atmospheric boundary layer

    Czech Academy of Sciences Publication Activity Database

    Tauer, M.; Šimonek, J.; Kozel, Karel; Jaňour, Zbyněk

    Praha : Ústav termomechaniky AV ČR, v. v. i., 2009 - (Jonáš, P.; Uruba, V.), s. 47-48 ISBN 978-80-87012-21-5. [Colloquium Fluid Dynamics 2009. Praha (CZ), 21.10.2009-23.10.2009] R&D Projects: GA ČR GA103/09/0977 Institutional research plan: CEZ:AV0Z20760514 Keywords : computation stratified flows * Navier-Stokes equations * atmospheric boundary layer Subject RIV: DG - Athmosphere Sciences, Meteorology

  3. Numerical solution of 2D flows in atmospheric boundary layer

    Czech Academy of Sciences Publication Activity Database

    Šimonek, J.; Tauer, J.; Kozel, K.; Jaňour, Zbyněk; Příhoda, Jaromír

    Praha : Ústav termomechaniky AV ČR, v. v. i., 2008 - (Jonáš, P.; Uruba, V.), s. 51-52 ISBN 978-80-87012-14-7. [Colloquium FLUID DYNAMICS 2008. Praha (CZ), 22.10.2008-24.10.2008] R&D Projects: GA AV ČR 1ET400760405 Institutional research plan: CEZ:AV0Z20760514 Keywords : numerical simulation * atmospheric boundary layer * stratified flow Subject RIV: BK - Fluid Dynamics

  4. Albedo muons in upper layers of the atmosphere

    International Nuclear Information System (INIS)

    The albedo muon fluxes are calculated in the energy range 50≤E≤1000 MeV in the upper atmospheric layers. It is shown that the anisotropy degree of albedo muon flux in the stratosphere increases with the muon energy increase, and according to the absolute values the albedo muon flux becomes comparable with the direct albedo proton fluxes at energies > 200 MeV. 8 refs.; 2 figs

  5. On the Impact of Wind Farms on a Convective Atmospheric Boundary Layer

    Science.gov (United States)

    Lu, Hao; Porté-Agel, Fernando

    2015-10-01

    With the rapid growth in the number of wind turbines installed worldwide, a demand exists for a clear understanding of how wind farms modify land-atmosphere exchanges. Here, we conduct three-dimensional large-eddy simulations to investigate the impact of wind farms on a convective atmospheric boundary layer. Surface temperature and heat flux are determined using a surface thermal energy balance approach, coupled with the solution of a three-dimensional heat equation in the soil. We study several cases of aligned and staggered wind farms with different streamwise and spanwise spacings. The farms consist of Siemens SWT-2.3-93 wind turbines. Results reveal that, in the presence of wind turbines, the stability of the atmospheric boundary layer is modified, the boundary-layer height is increased, and the magnitude of the surface heat flux is slightly reduced. Results also show an increase in land-surface temperature, a slight reduction in the vertically-integrated temperature, and a heterogeneous spatial distribution of the surface heat flux.

  6. 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.

  7. 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...

  8. Wind Tunnel Simulation of the Atmospheric Boundary Layer

    Science.gov (United States)

    Hohman, Tristen; Smits, Alexander; Martinelli, Luigi

    2013-11-01

    To simulate the interaction of large Vertical Axis Wind Turbines (VAWT) with the Atmospheric Boundary Layer (ABL) in the laboratory, we implement a variant of Counihan's technique [Counihan 1969] in which a combination of a castellated barrier, elliptical vortex generators, and floor roughness elements is used to create an artificial ABL profile in a standard closed loop wind tunnel. To examine the development and formation of the artificial ABL hotwire and SPIV measurements were taken at various downstream locations with changes in wall roughness, wall type, and vortex generator arrangements. It was found possible to generate a boundary layer at Reθ ~106 , with a mean velocity that followed the 1/7 power law of a neutral ABL over rural terrain and longitudinal turbulence intensities and power spectra that compare well with the data obtained for high Reynolds number flat plate turbulent boundary layers [Hultmark et al. 2010]. Supported by Hopewell Wind Power Ltd., and the Princeton Grand Challenges Program.

  9. 用SA雷达测量近地面层大气折射率场%Using SA radar for measurement of atmospheric refractive index fields of near-surface layer

    Institute of Scientific and Technical Information of China (English)

    胡帆; 王凌震; 周文嫣; 喜度; 徐芬

    2011-01-01

    通过测量近地面层的水汽变化,可以研究中小尺度雷暴系统的初生和发展,进而可以根据水汽数据帮助作出未来中小尺度天气过程的临近预报.因此,水汽探测具有重要的研究和应用价值.研究和实验证明,目前我国大量布网的SA多谱勒天气雷达,能够开展大气折射率场的探测,并用探测到的折射率场反演水汽的变化.本文对用SA雷达实现这种探测的一些关键性技术问题进行了论述.通过这项研究,将扩大sA雷达的探测能力,弥补近地面水汽资料的不足,帮助研究对流性中小尺度天气系统的生消演变与水汽场变化的关系,有望改善数值模式对中小尺度系统的预报能力.%Through the survey of the change of surface layer water vapor, we may investigate newborn and developing process of meso-microscale thunderstorm system, furthermore, we may carry out the short-period forecast of meso-microscale synoptic process according to the water vapor data.Therefore,the water vapor survey is of great value to the research and application.Our research and experiment have shown that widely deployed SA radar can be utilized for measurement of atmospheric refraction index field and further can infer the change of water vapor.This article discuses some key technology of the detection by SA radar.This research may extend detecting capability of SA radar which compensates the insufficiency of ground water vapor information and help study the relationship of meso-microscale convection system evolution to water vapour field change.It can also be expected to improve forecast capability of meso-microscale system in numerical model.

  10. Conditionally Averaged Large-Scale Motions in the Neutral Atmospheric Boundary Layer: Insights for Aeolian Processes

    Science.gov (United States)

    Jacob, Chinthaka; Anderson, William

    2016-06-01

    Aeolian erosion of flat, arid landscapes is induced (and sustained) by the aerodynamic surface stress imposed by flow in the atmospheric surface layer. Conceptual models typically indicate that sediment mass flux, Q (via saltation or drift), scales with imposed aerodynamic stress raised to some exponent, n, where n > 1 . This scaling demonstrates the importance of turbulent fluctuations in driving aeolian processes. In order to illustrate the importance of surface-stress intermittency in aeolian processes, and to elucidate the role of turbulence, conditional averaging predicated on aerodynamic surface stress has been used within large-eddy simulation of atmospheric boundary-layer flow over an arid, flat landscape. The conditional-sampling thresholds are defined based on probability distribution functions of surface stress. The simulations have been performed for a computational domain with ≈ 25 H streamwise extent, where H is the prescribed depth of the neutrally-stratified boundary layer. Thus, the full hierarchy of spatial scales are captured, from surface-layer turbulence to large- and very-large-scale outer-layer coherent motions. Spectrograms are used to support this argument, and also to illustrate how turbulent energy is distributed across wavelengths with elevation. Conditional averaging provides an ensemble-mean visualization of flow structures responsible for erosion `events'. Results indicate that surface-stress peaks are associated with the passage of inclined, high-momentum regions flanked by adjacent low-momentum regions. Fluid in the interfacial shear layers between these adjacent quasi-uniform momentum regions exhibits high streamwise and vertical vorticity.

  11. Characterization of the Martian Surface Layer

    OpenAIRE

    Martínez, Germán; Valero Rodríguez, Francisco; Vázquez Martínez, Luis

    2009-01-01

    We have estimated the diurnal evolution of Monin- Obukhov length, friction velocity, temperature scale, surface heat flux, eddy-transfer coefficients for momentum and heat, and turbulent viscous dissipation rate on the Martian surface layer for a complete Sol belonging to the Pathfinder mission. All these magnitudes have been derived from in situ wind and temperature measurements at around 1.3 m height, and simulated ground temperature (from 6 a.m. Sol 25 to 6 a.m. Sol 26). Up to the momen...

  12. 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.

  13. Implementation of a convective atmospheric boundary layer scheme in a tropospheric chemistry transport model

    Science.gov (United States)

    Wang, K.-Y.; Pyle, J. A.; Sanderson, M. G.; Bridgeman, C.

    1999-10-01

    A convective atmospheric boundary layer (ABL) scheme for the transport of trace gases in the lower troposphere has been implemented from the Community Climate Model, Version 2 [Hack et al., 1993] into a tropospheric chemistry transport model [Wang, 1998]. The atmospheric boundary layer scheme includes the calculation of atmospheric radiative transfer, surface energy balance, and land surface temperature and has a specified annual variation of sea surface temperature. The calculated diurnal variation of the height of the boundary layer is similar to the results of Troen and Mahrt [1986] and is in a good agreement with Holtslag and Boville [1993]. The modeled height of the boundary layer shows a seasonal shift between land and sea in the Northern Hemisphere. In summer (June-July-August), the height of the boundary layer is deeper over land (850-2250 m) and shallower over sea (50-850 m); while in winter (December-January-February), it is shallower over land (50-850 m) and deeper over sea (850-2850 m). The coupled ABL-chemical transport model is verified against measurements of radon 222 and methane. Comparison of the coupled model with a non-ABL model indicates significant differences between these model simulations and a better agreement between the coupled model and measurements. There is a significant effect on the trace gas distribution when the ABL model is compared with the non-ABL schemes. For example, the ABL scheme shows more O3 transported from the middle troposphere down to the surface, while more CO is pumped up from the surface into the middle troposphere. The seasonal cycle of modeled CH4 is significantly improved with the inclusion of the new ABL scheme, especially in regions which are not remote from methane sources.

  14. Radiative instabilities of atmospheric jets and boundary layers

    International Nuclear Information System (INIS)

    Complex flows occur in the atmosphere and they can be source of internal gravity waves. We focus here on the sources associated with radiative and shear (or Kelvin-Helmholtz) instabilities. Stability studies of shear layers in a stably stratified fluid concern mainly cases where shear and stratification are aligned along the same direction. In these cases, Miles (1961) and Howard (1961) found a necessary condition for stability based on the Richardson number: Ri ≥ 1/4. In this thesis, we show that this condition is not necessary when shear and stratification are not aligned: we demonstrate that a two-dimensional planar Bickley jet can be unstable for all Richardson numbers. Although the most unstable mode remains 2D, we show there exists an infinite family of 3D unstable modes exhibiting a radiative structure. A WKBJ theory is found to provide the main characteristics of these modes. We also study an inviscid and stratified boundary layer over an inclined wall with non-Boussinesq and compressible effects. We show that this flow is unstable as soon as the wall is not horizontal for all Froude numbers and that strongly stratified 3D perturbations behave exactly like compressible 2D perturbations. Applications of the results to the jet stream and the atmospheric boundary layer are proposed. (author)

  15. Problems in the simulation of atmospheric boundary layer flows. [natural wind environment in atmospheric boundary layer for aerospace and aeronautical applications

    Science.gov (United States)

    Fichtl, G. H.

    1973-01-01

    The realistic simulation of flow in the atmospheric boundary layers at heights greater than two kilometers is discussed. Information concerning horizontally homogeneous and statistically stationary atmospheric boundary layer flows is presented. The problems related to the incorporation of the information into atmospheric wind simulation programs are analyzed. The information which the meteorologist must acquire in order to provide a basis for improving the simulation of atmospheric boundary flows is explained.

  16. Atmospheric corrosion evaluation of galvanised steel by thin layer activation

    International Nuclear Information System (INIS)

    The release of certain metals, such as zinc, from outdoor constructions due to atmospheric corrosion is of some concern. For risk assessments the evaluation of the amount of released metal is of importance. Various methods can be used to study the release of metals. These include those using radiotracers, such as thin layer activation (TLA). To verify the reliability of TLA with respect to conventional techniques in the evaluation of atmospheric corrosion, galvanised steel was exposed to a mild marine environment. The amount of zinc in the corrosion products, released through artificial leaching, at different time intervals was evaluated by TLA and atomic absorption spectroscopy (AAS). A good correlation between the results was found indicating the feasibility of TLA for these release studies

  17. Segregation in the Atmospheric Boundary Layer - A Discussion

    Science.gov (United States)

    Dlugi, Ralph; Berger, Martina; Zelger, Michael; Hofzumahaus, Andreas; Rohrer, Franz; Holland, Frank; Lu, Keding; Tsokankunku, Anywhere; Sörgel, Matthias; Kramm, Gerhard; Mölders, Nicole

    2016-04-01

    Segregation is a well known topic in technical chemistry and means an incomplete mixing of the reactants. Incomplete mixing reduces the rate of reaction which is of utmost importance in technical chemistry but has been payed less attention in atmospheric chemistry. Different observational and modelling studies on chemical reactions in the turbulent and convective atmospheric boundary layer are analysed for the influences of segregation in the systems NO ‑ NO2 ‑ O3 and OH + V OCs (with main focus on isoprene). Also some estimates on reactions like HO2 + NO (an important recycling mechanism for OH) will be given. Especially, different terms of the intensity of segregation IS (correlation coefficients, standard deviations of mixing ratios) are compared and are related to characteristics of the flow regimes, such as mixing conditions and Damköhler numbers. Also influences of fluctuations of actinic fluxes are discussed which influence the mostly photo chemically driven reactions that were investigated.

  18. Coherent structures in the Es layer and neutral middle atmosphere

    Czech Academy of Sciences Publication Activity Database

    Mošna, Zbyšek; Koucká Knížová, Petra; Potužníková, Kateřina

    Sofia: Space Research and Technologies Institute, Bulgarian Academy of Sciences, 2015 - (Georgieva, K.; Kirov, B.; Danov, D.), s. 73-76 ISSN 2367-7570. [Workshop “Solar Influences on the Magnetosphere, Ionosphere and Atmosphere” /7th/. Sunny Beach (BG), 01.06.2015-05.06.2015] R&D Projects: GA MŠk(CZ) LG13042; GA ČR(CZ) GAP209/12/2440; GA ČR(CZ) GA15-24688S Institutional support: RVO:68378289 Keywords : coherent structures * ionospheric Es layer * neutral middle atmosphere Subject RIV: DG - Athmosphere Sciences, Meteorology http://ws-sozopol.stil.bas.bg/2015Sunny/Proceedings2015.pdf

  19. A wavenumber-frequency spectral model for atmospheric boundary layers

    International Nuclear Information System (INIS)

    Motivated by the need to characterize power fluctuations in wind farms, we study spatio-temporal correlations of a neutral atmospheric boundary layer in terms of the joint wavenumber-frequency spectrum of the streamwise velocity fluctuations. To this end, we perform a theoretical analysis of a simple advection model featuring the advection of small- scale velocity fluctuations by the mean flow and large-scale velocity fluctuations. The model is compared to data from large-eddy simulations (LES). We find that the model captures the trends observed in LES, specifically a Doppler shift of frequencies due to the mean flow as well as a Doppler broadening due to random sweeping effects

  20. Study of atmospheric aerosols and mixing layer by LIDAR

    International Nuclear Information System (INIS)

    The LIDAR (laser radar) is an active remote sensing technique, which allows for the altitude-resolved observation of several atmospheric constituents. A typical application is the measurement of the vertically resolved aerosol optical properties. By using aerosol particles as a marker, continuous determination of the mixing layer height (MLH) can also be obtained by LIDAR. Some examples of aerosol extinction coefficient profiles and MLH extracted from a 1-year LIDAR data set collected in Milan (Italy) are discussed and validated against in situ data (from a balloon-borne optical particle counter). Finally a comparison of the observation-based MLH with relevant numerical simulations (mesoscale model MM5) is provided. (authors)

  1. Numerical simulation of 3D flows in atmospheric boundary layer

    Czech Academy of Sciences Publication Activity Database

    Šimonek, Jiří; Kozel, K.; Jaňour, Zbyněk

    Praha : Ústav termomechaniky AV ČR, v. v. i, 2012 - (Šimurda, D.; Kozel, K.), s. 93-96 ISBN 978-80-87012-40-6. [Topical Problems of Fluid Mechanics 2012 . Praha (CZ), 15.02. 2012 -17.02. 2012 ] R&D Projects: GA ČR GAP101/12/1271 Institutional research plan: CEZ:AV0Z20760514 Keywords : numerical solution * atmospheric boundary layer * Navier-Stokes equation s Subject RIV: DG - Athmosphere Sciences, Meteorology

  2. Behaviour of tracer diffusion in simple atmospheric boundary layer models

    Directory of Open Access Journals (Sweden)

    P. S. Anderson

    2006-12-01

    Full Text Available 1-D profiles and time series from an idealised atmospheric boundary layer model are presented, which show agreement with measurements of polar photogenic NO and NO2. Diffusion models are increasingly being used as the framework for studying tropospheric air chemistry dynamics. Models based on standard boundary layer diffusivity profiles have an intrinsic behaviour that is not necessarily intuitive, due to the variation of turbulent diffusivity with height. The relatively simple model provides both a programming and a conceptual tool in the analysis of observed trace gas evolution. A time scale inherent in the model can be tuned by fitting model time series to observations. This scale is then applicable to the more physically simple but chemically complex zeroth order or box models of chemical interactions.

  3. 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

  4. 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.

  5. Total Solar Eclipses and Atmospheric Boundary Layer Response

    Science.gov (United States)

    Stoev, A.; Stoeva, P.; Kuzin, S.

    2012-11-01

    The effect of three total solar eclipses on meteorological parameters is discussed in the paper. Measurements were conducted at the village of Ravnets,General Toshevo municipality, Bulgaria, 1999,in Manavgat, near Antalya, Turkey, 2006 and in Tian Huang Ping, China, 2009. The observed decrease of the sky illumination (incoming solar radiation) during the eclipses was proportional to the percentage of solar coverage. The after eclipse sky illumination level is due to the effect of the natural change of the solar elevation angle. For the 1999 TSE it did not regain its pre eclipse value, it has exactly the same value for the 2006 TSE, and, It is three times larger than the pre eclipse value for the 2009 TSE. This fact can be easily explained by the Local Time of the maximum of the eclipses: LT 13:12, LT 12:58, and LT 09:34, respectively. Measurements showed significant changes in the surface air temperature. The minimum of the air temperature during the 2009 TSE (Tmin=4.5°C) was measured 6 min after the end of the total phase. This minimal temperature drop and larger time lag can be explained with the huge artificial lake near the place of observation, which minimizes the temperature response due to its larger heat capacity. During the 1999 TSE, minimal temperature (Tmin=6.4°C) is measured 7 min 30 s after the total phase, and for the 2006 TSE (Tmin=5°C) - 5 min. It is in accordance with the fact that the temperature minima at residential/commercial stations occurred in general, before the minima at stations in agricultural terrains. In 2006 we were at the yard of the hotel, and in 1999 in the countryside. The wind velocity drops during the total phase as a result of the cooling and stabilization of the atmospheric boundary layer. The wind direction during the total phase changes and the wind begins to blow in the same direction as the direction of motion of the lunar shadow on the earth. Cirrus and cirrostratus clouds were observed during the 2006 total solar

  6. Simultaneous profiling of the Arctic Atmospheric Boundary Layer

    Science.gov (United States)

    Mayer, S.; Jonassen, M.; Reuder, J.

    2009-09-01

    The structure of the Arctic atmospheric boundary layer (AABL) and the heat and moisture fluxes between relatively warm water and cold air above non-sea-ice-covered water (such as fjords, leads and polynyas) are of great importance for the sensitive Arctic climate system (e.g. Andreas and Cash, 1999). So far, such processes are not sufficiently resolved in numerical weather prediction (NWP) and climate models (e.g. Tjernström et al., 2005). Especially for regions with complex topography as the Svalbard mountains and fjords the state and diurnal evolution of the AABL is not well known yet. Knowledge can be gained by novel and flexible measurement techniques such as the use of an unmanned aerial vehicle (UAV). An UAV can perform vertical profiles as well as horizontal surveys of the mean meteorological parameters: temperature, relative humidity, pressure and wind. A corresponding UAV, called Small Unmanned Meteorological Observer (SUMO), has been developed at the Geophysical Institute at the University of Bergen in cooperation with Müller Engineering (www.pfump.org) and the Paparazzi Project (http://paparazzi.enac.fr). SUMO has been used under Arctic conditions at Longyear airport, Spitsbergen in March/April 2009. Besides vertical profiles up to 1500 m and horizontal surveys at flight levels of 100 and 200 m, SUMO could measure vertical profiles for the first time simultaneously in a horizontal distance of 1 km; one over the ice and snow-covered land surface and the other one above the open water of Isfjorden. This has been the first step of future multiple UAV operations in so called "swarms” or "flocks”. With this, corresponding measurements of the diurnal evolution of the AABL can be achieved with minimum technical efforts and costs. In addition, the Advanced Research Weather Forecasting model (AR-WRF version 3.1) has been run in high resolution (grid size: 1 km). First results of a sensitivity study where ABL schemes have been tested and compared with

  7. Neutral atmosphere near the icy surface of Jupiter's moon Ganymede

    Science.gov (United States)

    Shematovich, V. I.

    2016-07-01

    The paper discusses the formation and dynamics of the rarefied gas envelope near the icy surface of Jupiter's moon Ganymede. Being the most massive icy moon, Ganymede can form a rarefied exosphere with a relatively dense near-surface layer. The main parent component of the gas shell is water vapor, which enters the atmosphere due to thermal degassing, nonthermal radiolysis, and other active processes and phenomena on the moon's icy surface. A numerical kinetic simulation is performed to investigate, at the molecular level, the formation, chemical evolution, and dynamics of the mainly H2O- and O2-dominant rarefied gas envelopes. The ionization processes in these rarefied gas envelopes are due to exposure to ultraviolet radiation from the Sun and the magnetospheric plasma. The chemical diversity of the icy moon's gas envelope is attributed to the primary action of ultraviolet solar photons and plasma electrons on the rarefied gas in the H2O- or O2-dominant atmosphere. The model is used to calculate the formation and development of the chemical diversity in the relatively dense near-surface envelope of Ganymede, where an important contribution comes from collisions between parent molecules and the products of their photolysis and radiolysis.

  8. 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

    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......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...

  9. 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.

  10. Bioactive surfaces with atomic layer deposition

    OpenAIRE

    Kvalvik, Julie Nitsche

    2015-01-01

    The overall goal of this work has been to make bioactive surfaces with atomic layer deposition (ALD). To do this, a new ALD system with titanium tetraisopropoxide (TTIP) and lysine as precursors was developed with emphasis on studying the effects of pulsing times and deposition temperatures. TTIP was chosen as titanium is regarded to be biocompatible and lysine was chosen as poly-L-lysine is a part of the extra-cellular matrix (ECM) and hence affects cell adhesion. The effect of a water pulse...

  11. Scaling of the asymptotic entropy jump in the superadiabatic layers of stellar atmospheres

    CERN Document Server

    Magic, Zazralt

    2016-01-01

    Stellar structure calculations are able to predict precisely the properties of stars during their evolution. However, convection is still modelled by the mixing length theory; therefore, the upper boundary conditions near the optical surface do not agree with asteroseismic observations. We want to improve how the outer boundary conditions are determined in stellar structure calculations. We study realistic 3D stellar atmosphere models to find alternative properties. We find that the asymptotic entropy run of the superadiabatic convective surface layers exhibit a distinct universal stratification when normalised by the entropy minimum and jump. The normalised entropy can be represented by a 5th order polynomial very accurately, and a 3rd order polynomial also yields accurate coefficients. This generic entropy stratification or the solar stratification, when scaled by the entropy jump and minimum, can be used to improve the modelling of superadiabatic surface layers in stellar structure calculations. Furthermor...

  12. Isolating Effects of Water Table Dynamics, Terrain, and Soil Moisture Heterogeneity on the Atmospheric Boundary Layer Using Coupled Models

    Science.gov (United States)

    Rihani, Jehan Fouad

    Previous observational and modeling studies have demonstrated the sensitivity of atmospheric processes to land surface and subsurface conditions. The extent of the connection between these processes, however, is not yet fully understood. A sufficient understanding is needed of the circumstances under which these coupled processes might play a more significant role and when they might be simplified into the decoupled systems so frequently modeled in practice. This work focuses on the effects of terrain and soil moisture heterogeneity in changing water table depth and energy fluxes at the land surface, and how this might impact the development and structure of the atmospheric boundary layer. A three-dimensional, variably saturated groundwater model coupled to a three dimensional mesoscale atmospheric model (PF.ARPS) is used here to study the two-way feedback between the subsurface, land-surface, and atmosphere for both idealized cases and a real watershed. This is done by addressing the following key questions: How do terrain, soil moisture heterogeneity, and subsurface properties affect the planetary boundary layer? What are the effects of water table depth on land surface fluxes and boundary layer development and depth? What times of the diurnal cycle and which locations within a watershed demonstrate stronger feedbacks between the subsurface and the atmosphere? These questions are first addressed for idealized simulations designed to illustrate subsurface-surface feedbacks on one hand, and land-atmosphere feedbacks on the other hand. The coupled hydrologic model is then used to simulate real conditions over the Little Washita watershed in Oklahoma with the goal of addressing the above questions for a real watershed, and exploring the two-way feedback between the atmospheric boundary layer and the water table. The coupled simulations are compared to non-coupled atmospheric simulations initialized with simplified and realistic soil moisture profiles. Effects of a

  13. 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.)

  14. 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.

  15. Surface-atmosphere decoupling limits accumulation at Summit, Greenland.

    Science.gov (United States)

    Berkelhammer, Max; Noone, David C; Steen-Larsen, Hans Christian; Bailey, Adriana; Cox, Christopher J; O'Neill, Michael S; Schneider, David; Steffen, Konrad; White, James W C

    2016-04-01

    Despite rapid melting in the coastal regions of the Greenland Ice Sheet, a significant area (~40%) of the ice sheet rarely experiences surface melting. In these regions, the controls on annual accumulation are poorly constrained owing to surface conditions (for example, surface clouds, blowing snow, and surface inversions), which render moisture flux estimates from myriad approaches (that is, eddy covariance, remote sensing, and direct observations) highly uncertain. Accumulation is partially determined by the temperature dependence of saturation vapor pressure, which influences the maximum humidity of air parcels reaching the ice sheet interior. However, independent proxies for surface temperature and accumulation from ice cores show that the response of accumulation to temperature is variable and not generally consistent with a purely thermodynamic control. Using three years of stable water vapor isotope profiles from a high altitude site on the Greenland Ice Sheet, we show that as the boundary layer becomes increasingly stable, a decoupling between the ice sheet and atmosphere occurs. The limited interaction between the ice sheet surface and free tropospheric air reduces the capacity for surface condensation to achieve the rate set by the humidity of the air parcels reaching interior Greenland. The isolation of the surface also acts to recycle sublimated moisture by recondensing it onto fog particles, which returns the moisture back to the surface through gravitational settling. The observations highlight a unique mechanism by which ice sheet mass is conserved, which has implications for understanding both past and future changes in accumulation rate and the isotopic signal in ice cores from Greenland. PMID:27386509

  16. Aeroelectric structures and turbulence in the atmospheric boundary layer

    Directory of Open Access Journals (Sweden)

    S. V. Anisimov

    2013-10-01

    Full Text Available Complex electrical measurements with the use of sodar data show that electric field pulsation analysis is useful for electrodynamics/turbulence monitoring under different conditions. In particular, the number of aeroelectric structures (AES generated per hour is a convenient measure of the turbulence intensity. During convectively unstable periods, as many as 5–10 AES form per hour. Under stable conditions, AES occasionally form as well, indicating the appearance of occasional mixing events reflected in the electric field perturbations. AES magnitudes under stable conditions are relatively small, except in special cases such as high humidity and fog. The analysis of electric field (EF spectra gives additional useful information on the parameters of the atmospheric boundary layer and its turbulence. A rather sharp change in the spectrum slope takes place in the vicinity of 0.02 Hz under stable conditions. The characteristic slope of the spectrum and its change are reproduced in a simple model of EF formation.

  17. Coherent structures in the Es layer and neutral middle atmosphere

    Science.gov (United States)

    Mošna, Zbyšek; Knížová, Petra Koucká; Potužníková, Kateřina

    2015-12-01

    The present paper shows results from the summer campaign performed during geomagnetically quiet period from June 1 to August 31, 2009. Within time-series of stratospheric and mesospheric temperatures at pressure levels 10-0.1 hPa, mesospheric winds measured in Collm, Germany, and the sporadic E-layer parameters foEs and hEs measured at the Pruhonice station we detected specific coherent wave-bursts in planetary wave domain. Permanent wave-like activity is observed in all analyzed data sets. However, the number of wave-like structures persistent in large range of height from the stratosphere to lower ionosphere is limited. The only coherent modes that are detected on consequent levels of the atmosphere are those corresponding to eigenmodes of planetary waves.

  18. 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.

  19. 3-D water vapor field in the atmospheric boundary layer observed with scanning differential absorption lidar

    Science.gov (United States)

    Späth, Florian; Behrendt, Andreas; Muppa, Shravan Kumar; Metzendorf, Simon; Riede, Andrea; Wulfmeyer, Volker

    2016-04-01

    High-resolution three-dimensional (3-D) water vapor data of the atmospheric boundary layer (ABL) are required to improve our understanding of land-atmosphere exchange processes. For this purpose, the scanning differential absorption lidar (DIAL) of the University of Hohenheim (UHOH) was developed as well as new analysis tools and visualization methods. The instrument determines 3-D fields of the atmospheric water vapor number density with a temporal resolution of a few seconds and a spatial resolution of up to a few tens of meters. We present three case studies from two field campaigns. In spring 2013, the UHOH DIAL was operated within the scope of the HD(CP)2 Observational Prototype Experiment (HOPE) in western Germany. HD(CP)2 stands for High Definition of Clouds and Precipitation for advancing Climate Prediction and is a German research initiative. Range-height indicator (RHI) scans of the UHOH DIAL show the water vapor heterogeneity within a range of a few kilometers up to an altitude of 2 km and its impact on the formation of clouds at the top of the ABL. The uncertainty of the measured data was assessed for the first time by extending a technique to scanning data, which was formerly applied to vertical time series. Typically, the accuracy of the DIAL measurements is between 0.5 and 0.8 g m-3 (or < 6 %) within the ABL even during daytime. This allows for performing a RHI scan from the surface to an elevation angle of 90° within 10 min. In summer 2014, the UHOH DIAL participated in the Surface Atmosphere Boundary Layer Exchange (SABLE) campaign in southwestern Germany. Conical volume scans were made which reveal multiple water vapor layers in three dimensions. Differences in their heights in different directions can be attributed to different surface elevation. With low-elevation scans in the surface layer, the humidity profiles and gradients can be related to different land cover such as maize, grassland, and forest as well as different surface layer

  20. Surface interactions in a cold plasma atmosphere

    International Nuclear Information System (INIS)

    The formation of pyrocoating on conmercial grade graphite in a cold plasma atmosphere of argon and propylene mixtures was investigated. The experiments were performed in an evacuated glass tube at low pressure (6 Hz), and in some experiments by micro-wave frequency irradiation (2.45x106 Hz) through an external antenna that was located around the middle of the tube. The research was performed in four complementary directions: (a) Characterization of the plasma. The effect of various experimental parameters on the composition of the plasma was investigated; the density of the positive ions; the temperature of the electrons. The following parameters were investigated: the concentration of the hydrocarbon in the feed mixture; the total gas pressure in the tube; the induced power; the location of the sampling position in relation to the location of the antenna and the direction of the gas flow. (b) Measurements of the deposition rate as a function of the concentration of the propylene in the feed mixture and of the total gas pressure in the tube. (c) Characterization of the coating. The characterization included structure and morphology analysis, and measurements of microporosity, composition, optical anisotropy and density. (d) Development of a theoretical model of the deposition process which is based on the plasma-surface interactions, and relates the characteristics of the plasma to those of the deposited coating. The values for the composition of the coating and its rate of deposition that were calculated using the model agree well with those that were measured experimentally

  1. Surface Characterization for Land-Atmosphere Studies of CLASIC

    Science.gov (United States)

    Jackson, T. J.; Kustas, W.; Torn, M. S.; Meyers, T.; Prueger, J.; Fischer, M. L.; Avissar, R.; Yueh, S.; Anderson, M.; Miller, M.

    2006-12-01

    The Cloud and Land Surface Interaction Campaign will focus on interactions between the land surface, convective boundary layer, and cumulus clouds. It will take place in the Southern Great Plains (SGP) area of the U.S, specifically within the US DOE ARM Climate Research Facility. The intensive observing period will be June of 2007, which typically covers the winter wheat harvest in the region. This region has been the focus of several related experiments that include SGP97, SGP99, and SMEX03. For the land surface, some of the specific science questions include 1) how do spatial variations in land cover along this trajectory modulate the cloud structure and the low-level water vapor budget, 2) what are the relationships between land surface characteristics (i.e., soil texture, vegetation type and fractional cover) and states (particularly soil moisture and surface temperature) and the resulting impact of the surface energy balance on boundary layer and cloud structure and dynamics and aerosol loading; and 3) what is the interplay between cumulus cloud development and surface energy balance partitioning between latent and sensible heat, and implications for the carbon flux? Most of these objectives will require flux and state measurements throughout the dominant land covers and distributed over the geographic domain. These observations would allow determining the level of up- scaling/aggregation required in order to understand the impact of landscape changes affecting energy balance/flux partitioning and impact on cloud/atmospheric dynamics. Specific contributions that are planned to be added to CLASIC include continuous tower-based monitoring of surface fluxes for key land cover types prior to, during, and post-IOP, replicate towers to quantify flux variance within each land cover, boundary layer properties and fluxes from a helicopter-based system, airplane- and satellite-based flux products throughout the region, aircraft- and tower-based concentration data for

  2. Processes affecting the stable isotope composition of calcite during precipitation on the surface of stalagmites: Laboratory experiments investigating the isotope exchange between DIC in the solution layer on top of a speleothem and the CO2 of the cave atmosphere

    Science.gov (United States)

    Dreybrodt, Wolfgang; Hansen, Maximilian; Scholz, Denis

    2016-02-01

    We present a theoretical derivation of the exchange time, τex, needed to establish isotopic equilibrium between atmospheric CO2 in a cave and HCO3- dissolved in a thin water film covering the surface of a speleothem. The result is τex = τredex · [HCO3-]/ (KH · pCO2 cave) , where τredex depends on the depth, a, of the water film and on temperature. [HCO3-] is the concentration of bicarbonate, pCO2 cave the partial pressure of CO2, and KH is Henry's constant. To test the theory we prepared stagnant or flowing thin films of a NaHCO3 solution and exposed them at 20 °C to an CO2 containing atmosphere of pCO2 500, 12,500, or 25,000 ppmV and defined isotope composition. The δ13C and δ18O values of the DIC in the solution were measured as a function of the exposure time. For stagnant films with depths between 0.06 and 0.2 cm the δ13C values exhibit an exponential approach towards isotope equilibrium with the atmospheric CO2 with exchange time, τex. The δ18O values first evolve towards isotopic equilibrium with atmospheric CO2, reach a minimum value and then drift away from the isotopic equilibrium with atmospheric CO2 approaching a steady state caused by isotopic exchange of oxygen with water. The experimental findings are in satisfactory agreement with the theoretical predictions. To further investigate isotope evolution in cave analogue conditions, a water film containing 5 mmol/L of NaHCO3 with a depth of 0.013 cm flowing down an inclined borosilicate glass plate was exposed to an atmosphere with pCO2 = 500 ppmV at a temperature of 20 °C. The δ13C and δ18O values were measured as a function of flow (exposure) time, t. The isotope compositions in the DIC of the water film decrease linear in time by δDIC (t) =δDIC (0) - (δDIC (0) -δDIC (∞)) · t /τex where δDIC (0) is the initial isotope composition of dissolved inorganic carbon (DIC) in the water film and δDIC (∞) its final value. From these data an exchange time τex of ca. 7000 s was obtained

  3. Isolating effects of terrain and soil moisture heterogeneity on the atmospheric boundary layer: Idealized simulations to diagnose land-atmosphere feedbacks

    Science.gov (United States)

    Rihani, Jehan F.; Chow, Fotini K.; Maxwell, Reed M.

    2015-06-01

    The effects of terrain, soil moisture heterogeneity, subsurface properties, and water table dynamics on the development and behavior of the atmospheric boundary layer are studied through a set of idealized numerical experiments. The mesoscale atmospheric model Advanced Regional Prediction System (ARPS) is used to isolate the effects of subsurface heterogeneity, terrain, and soil moisture initialization. The simulations are initialized with detailed soil moisture distributions obtained from offline spin-ups using a coupled surface-subsurface model (ParFlow-CLM). In these idealized simulations, we observe that terrain effects dominate the planetary boundary layer (PBL) development during early morning hours, while the soil moisture signature overcomes that of terrain during the afternoon. Water table and subsurface properties produce a similar effect as that of soil moisture as their signatures (reflected in soil moisture profiles, energy fluxes, and evaporation at the land surface) can also overcome that of terrain during afternoon hours. This is mostly clear for land surface energy fluxes and evaporation at the land surface. We also observe the coupling between water table depth and planetary boundary layer depth in our cases is strongest within wet-to-dry transition zones. This extends the findings of previous studies which demonstrate the subsurface connection to surface energy fluxes is strongest in such transition zones. We investigate how this connection extends into the atmosphere and can affect the structure and development of the convective boundary layer.

  4. Surface layer characterisation of bearing rings

    Directory of Open Access Journals (Sweden)

    S.J. Skrzypek

    2007-11-01

    Full Text Available austenite. Theoretical calculation of residual macro-stresses due to volume fraction of transformed austenite in bearing rings and following measurements of residual stresses were carried out as well. The bearing elements were made of 100Cr6 steel and they were smoothed and grinded.Design/methodology/approach: Particular features of diffraction patterns like angle position; shape and intensity are used to characterize phase composition, residual micro and macro-stresses, crystallographic texture, lattice parameter, defects density and crystalline size.Findings: Machining by micro-deformation causes microstructural changes i.e. mechanically induced phase transformation of retained austenite and residual macrostresses. E.g. grinding cased tension and small compression whereas the mechanical smoothing of bearing rings caused high compresive residual stresses about -713 MPa.Research limitations/implications: For precise interpretation of differences between following results needs another investigations: i.e. measurement of retained austenite and residual stresses in rings after heat treatment before any mechanical treatment.Practical implications: The non-destructive character and large number of structural informations contained in diffraction pattern are the beneficial feature of diffraction methods. Therefore they have potential ability in application to technological operations and to diagnostic during fatigue.Originality/value: The non-destructive structure characterisation of surface layers for various kinds of bearing rings can be powerful method in surface characterization and in quality control. This results contribute in general relations between microstructure and properties.

  5. Investigating the Source, Transport, and Isotope Composition of Water in the Atmospheric Boundary Layer

    Science.gov (United States)

    Griffis, T. J.; Schultz, N. M.; Lee, X.

    2011-12-01

    The isotope composition of water (liquid and vapor phases) can provide important insights regarding the source of water used by plants, the origins of atmospheric water vapor, and the sources of carbon dioxide. In recent years there have been significant advances in the ability to quantify the isotope composition of water and water vapor using optical isotope techniques. We have used and helped develop some of these techniques to determine the isotope composition of soil and plant waters, to measure the isoflux of water vapor between the land surface and atmosphere, and to examine the isotope composition of water vapor and deuterium excess in the atmospheric boundary layer. In this presentation we will discuss three related issues: 1) Identification and correction of spectral contamination in soil and plant water samples using optical techniques; 2) The benefits and practical limitations of quantifying the isotope composition of evapotranspiration using the eddy covariance approach; and 3) The scientific value and feasibility of tracking the long-term (seasonal and interannual) behavior of the isotope composition of water vapor and deuterium excess in the atmospheric boundary layer. A few short stories will be provided from experiments conducted in the lab, at the field scale, and from a very tall tower at the University of Minnesota from 2008 to 2011.

  6. NOAA Climate Data Record (CDR) of Upper Atmospheric Temperature 4 Layer Microwave, Version 3.3

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The 4 Layer Upper Atmosphere Temperature (UAT) Climate Data Record (CDR) dataset is a monthly analysis of the tropospheric and stratospheric data using temperature...

  7. Momentum Transfer Between an Atmospheric and an Oceanic Layer at the Synoptic and the Mesoscale: An Idealized Numerical Study

    Science.gov (United States)

    Moulin, A.; Wirth, A.

    2016-04-01

    We consider air-sea interaction at the (atmospheric) synoptic and the mesoscale due to momentum transfer only. Two superposed one-layer fine-resolution shallow-water models are numerically integrated, where the upper layer represents the atmosphere and the lower layer the ocean. The frictional force between the two layers is implemented using a quadratic drag law and experiments with different values of the surface drag coefficient are performed. The actual energy loss of the atmosphere and the energy gain by the ocean, due to the interfacial shear, is determined and compared to estimates based on average speeds. The correlation between the vorticity in the atmosphere and the ocean is determined. Results differ from previous investigations where the exchange of momentum was considered at basin scale. It is shown that the ocean has a passive role, absorbing kinetic energy at nearly all times and locations, results showing that the energy input to the ocean increases almost quadratically with the value of the drag coefficient. Due to the feeble velocities in the ocean, the energy transfer depends only weakly on the oceanic velocity. The ocean dynamics leave nevertheless their imprint on atmospheric dynamics, leading to a quenched disordered state of the atmosphere-ocean system for the highest value of the drag coefficient considered. This finding questions the ergodic hypothesis for the idealized configuration studied here. The ergodic hypothesis is at the basis of a large number of experimental, observational and numerical results in ocean, atmosphere and climate dynamics.

  8. Influence of carbon monoxide to the surface layer of uranium metal and its oxides

    International Nuclear Information System (INIS)

    The surface structures of uranium metal and triuranium octaoxide (U3O8) and the influence of carbon monoxide to the surface layers have been studied by X-ray photoelectron spectroscopy (XPS). After exposure to carbon monoxide, contents of oxygen in the surface oxides of uranium metal and U3O8 are decreased and O/U ratios decrease 7.2%, 8.0% respectively. The investigation indicated the surface layers of uranium metal and its oxides were forbidden to further oxidation in the atmosphere of carbon monoxide. (11 refs., 9 figs., 2 tabs.)

  9. 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

  10. Estimation of atmospheric mixing layer height from radiosonde data

    Directory of Open Access Journals (Sweden)

    X. Y. Wang

    2014-02-01

    Full Text Available Mixing layer height (h is an important parameter for understanding the transport process in the troposphere, air pollution, weather and climate change. Many methods have been proposed to determine h by identifying the turning point of the radiosonde profile. However, substantial differences have been observed in the existing methods (e.g., the potential temperature (θ, relative humidity (RH, specific humidity (q and atmospheric refractivity (N methods. These differences are associated with the inconsistency of the temperature and humidity profiles in a boundary layer that is not well mixed, the changing measurability of the specific humidity and refractivity with height, the measurement error of humidity instruments within clouds, and the general existence of clouds. This study proposes a method to integrate the information of temperature, humidity and cloud to generate a consistent estimate of h. We apply this method to high vertical resolution (~ 30 m radiosonde data that were collected at 79 stations over North America during the period from 1998 to 2008; the data are obtained from the Stratospheric Processes and their Role in Climate Data Center (SPARC. The results show good agreement with those from N method as the information of temperature and humidity contained in N; however cloud effects that are included in our method increased the reliability of h. Furthermore, our results agree well with the independent h that was determined from lidar observations. From 1988 to 2008, the climatological h over North America was 1675± 303 m with a strong east–west gradient: higher values (generally greater than 1800 m occurred over the Midwest US, and lower values (usually less than 1400 m occurred over Alaska and the US west coast.

  11. 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.

  12. CVD diamond deposition under atmospheric conditions on steel with a silicon intermediate layer

    OpenAIRE

    Prieske, Markus

    2016-01-01

    In order to realize dry metal forming, the requirements of the surface layer, e.g. to load-bearing capacity and tribological properties are increasing. Therefore, the feasibility of chemical vapour deposition (CVD) of diamond onto tool steel 1.2379 under atmospheric conditions without a vacuum chamber is investigated, so that there is no limit according to the size of the tool. For the deposition of CVD diamond coatings, a laser-based plasma CVD process combined with a physical vapour dep-osi...

  13. 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.

  14. Transfer of radioactive aerosol from unit shelter in boundary atmosphere layer

    International Nuclear Information System (INIS)

    The evaluation of transfer of radioactive aerosol in boundary atmosphere layer in case of normal conditions of unit Shelter and in ceases of different emergency scenarios was performed. In cases of normal condition of unit Shelter the additional radioactive contamination of surface air in close ChNPP zone is the result of simultaneous activities of two sources: unorganized removal of radioactive aerosols from 'Shelter' gaps and release of aerosol particles through ventilating duct of power block 3 and 4. A software shell was created to implement computation mathematical models to evaluate transfer of radioactive aerosol from unit 'Shelter'

  15. 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

  16. Large-eddy simulation of an infinitely large wind farm in a stable atmospheric boundary layer

    Science.gov (United States)

    Lu, H.; Porté-Agel, F.

    2010-09-01

    When deployed as large arrays, wind turbines interact among themselves and with atmospheric boundary layer. To optimize their geometric arrangements, accurate knowledge of wind-turbine array boundary layer is of great importance. In this study, we integrated large eddy simulation with an actuator line technique, and used it to study the characteristics of wind-turbine wake in an idealized wind farm inside a stably stratified atmospheric boundary layer (SBL). The wind turbines, with a rotor diameter of 112m and a tower height of 119m, were placed in a well-known SBL turbulent case that has a boundary layer height of approximately 180m. The super-geostrophic nocturnal jet near the top of the boundary layer was eliminated due to the energy extraction and the enhanced mixing of momentum. Non-axisymmetric behavior of wake structure was observed in response to the non-uniform incoming turbulence, the Coriolis effects, and the rotational effects induced by blade motions. The turbulence intensity in the simulated turbine wakes was found to reach a maximum at the top-tip level and a downwind distance of approximately 3-5 rotor diameters from the turbines. The Coriolis effects caused a skewed spatial structure and drove certain amount of turbulent energy away from the center of the wake. The SBL height was increased, while the magnitudes of the surface momentum flux and the surface buoyancy flux were reduced by approximately 30%. The wind farm was also found to have a strong effect on area-averaged vertical turbulent fluxes of momentum and heat, which highlights the potential impact of wind farms on local meteorology.

  17. Composition of the earth's atmosphere by shock-layer radiometry during the PAET entry probe experiment.

    Science.gov (United States)

    Whiting, E. E.; Arnold, J. O.; Page, W. A.; Reynolds, R. M.

    1973-01-01

    A determination of the composition of the earth's atmosphere obtained from onboard radiometer measurements of the spectra emitted from the bow shock layer of a high-speed entry probe is reported. The N2, O2, CO2, and noble gas concentrations in the earth's atmosphere were determined to good accuracy by this technique. The results demonstrate unequivocally the feasibility of determining the composition of an unknown planetary atmosphere by means of a multichannel radiometer viewing optical emission from the heated atmospheric gases in the region between the bow shock wave and the vehicle surface. The spectral locations in this experiment were preselected to enable the observation of CN violet, N2(+) first negative and atomic oxygen emission at 3870, 3910, and 7775 A, respectively. The atmospheric gases were heated and compressed by the shock wave to a peak temperature of about 6100 K and a corresponding pressure of 0.4 atm. Complete descriptions of the data analysis technique and the onboard radiometer and its calibration are given.

  18. Numerical simulation of small-scale mixing processes in the upper ocean and atmospheric boundary layer

    Science.gov (United States)

    Druzhinin, O.; Troitskaya, Yu; Zilitinkevich, S.

    2016-02-01

    The processes of turbulent mixing and momentum and heat exchange occur in the upper ocean at depths up to several dozens of meters and in the atmospheric boundary layer within interval of millimeters to dozens of meters and can not be resolved by known large- scale climate models. Thus small-scale processes need to be parameterized with respect to large scale fields. This parameterization involves the so-called bulk coefficients which relate turbulent fluxes with large-scale fields gradients. The bulk coefficients are dependent on the properties of the small-scale mixing processes which are affected by the upper-ocean stratification and characteristics of surface and internal waves. These dependencies are not well understood at present and need to be clarified. We employ Direct Numerical Simulation (DNS) as a research tool which resolves all relevant flow scales and does not require closure assumptions typical of Large-Eddy and Reynolds Averaged Navier-Stokes simulations (LES and RANS). Thus DNS provides a solid ground for correct parameterization of small-scale mixing processes and also can be used for improving LES and RANS closure models. In particular, we discuss the problems of the interaction between small-scale turbulence and internal gravity waves propagating in the pycnocline in the upper ocean as well as the impact of surface waves on the properties of atmospheric boundary layer over wavy water surface.

  19. Some peculiarities of steel surface layer after electron beam superheating

    International Nuclear Information System (INIS)

    Fractographic investigations of a carbon steel surface layer subjected to electron beam hardening are made. It is found that the surface hardened layer of the steel is substantially nonuniform in depth. Undesirable markings of metal superheating are observed to a depth of 50-100 μm. Superheated zone fracture is shown to be of clearly defined intercrystalline nature. The superheating of surface layer results in increased brittleness, in degradation of contact fatigue and abrasive resistance

  20. Atmospheres and radiating surfaces of neutron stars with strong magnetic fields

    CERN Document Server

    Potekhin, A Y; Chabrier, G

    2016-01-01

    We review the current status of the theory of thermal emission from the surface layers of neutron stars with strong magnetic fields $B\\sim 10^{10}-10^{15}$ G, including formation of the spectrum in a partially ionized atmosphere and at a condensed surface. In particular, we describe recent progress in modeling partially ionized atmospheres of central compact objects in supernova remnants, which may have moderately strong fields $B\\sim 10^{10}-10^{11}$ G. Special attention is given to polarization of thermal radiation emitted by a neutron star surface. Finally, we briefly describe applications of the theory to observations of thermally emitting isolated neutron stars.

  1. The vertical structure of the atmospheric boundary layer over the central Arctic Ocean

    Institute of Scientific and Technical Information of China (English)

    BIAN Lingen; MA Yongfeng; LU Changgui; LIN Xiang

    2013-01-01

    The tropopause height and the atmospheric boundary layer (PBL) height as well as the variation of inversion layer above the floating ice surface are presented using GPS (global position system ) radiosonde sounding data and relevant data obtained by China’s fourth arctic scientific expedition team over the central Arctic Ocean (86◦-88◦N, 144◦-170◦W ) during the summer of 2010. The tropopause height is from 9.8 to 10.5 km, with a temperature range between-52.2 and-54.1◦C in the central Arctic Ocean. Two zones of maximum wind (over 12 m/s) are found in the wind profile, namely, low-and upper-level jets, located in the middle troposphere and the tropopause, respectively. The wind direction has a marked variation point in the two jets from the southeast to the southwest. The average PBL height determined by two methods is 341 and 453 m respectively. These two methods can both be used when the inversion layer is very low, but the results vary significantly when the inversion layer is very high. A significant logarithmic relationship exists between the PBL height and the inversion intensity, with a correlation coefficient of 0.66, indicating that the more intense the temperature inversion is, the lower the boundary layer will be. The observation results obviously differ from those of the third arctic expedition zone (80◦-85◦N). The PBL height and the inversion layer thickness are much lower than those at 87◦-88◦N, but the inversion temperature is more intense, meaning a strong ice-atmosphere interaction in the sea near the North Pole. The PBL structure is related to the weather system and the sea ice concentration, which affects the observation station.

  2. 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.

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

    Science.gov (United States)

    Davy, Richard; Esau, Igor

    2016-01-01

    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. PMID:27221757

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

    Science.gov (United States)

    Davy, Richard; Esau, Igor

    2016-01-01

    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. PMID:27221757

  5. 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

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

    DEFF Research Database (Denmark)

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

    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...

  7. Atmospheric effects on remote sensing of surface reflectance

    Science.gov (United States)

    Kaufman, Y. J.

    1984-01-01

    This paper reviews the atmospheric effects on remote sensing of surface reflectance. The scattering and absorption of sunlight by atmospheric molecules and aerosols affects the quality of images of the surface remotely sensed from satellites and aircrafts. The concentration and characteristics of the atmospheric aerosols vary from place to place and vary with time. The effect of atmospheric aerosols on the upward radiance depends on their optical thickness, scattering phase function and absorption. These parameters result from the aerosol concentration, composition, and the relative humidity. For high resolution images the aerosol scale height is also of importance. The radiative transfer theory that predicts the atmospheric radiances for a given surface and atmosphere is a well established theory for the case of uniform surfaces (or low resolution data). Some radiative transfer models exist for nonuniform surfaces and others are being developed. Recent field experiment and laboratory simulation data confirm the need for these models and can be used for their testing. It is shown that the atmospheric effect reduces the apparent resolution of satellite imagery and causes errors in the classification of surface fields. Suggestions for correction procedures are given. Such corrections can be based on ground observations, on satellite radiances above dark areas, or on climatologic information, depending on the accuracy of the corrections needed. The chosen correction algorithm depends also on the image resolution and the specific remote sensing application.

  8. Improving Hydrophobicity of Glass Surface Using Dielectric Barrier Discharge Treatment in Atmospheric Air

    International Nuclear Information System (INIS)

    Non-thermal plasmas under atmospheric pressure are of great interest in industrial applications, especially in material surface treatment. In this paper, the treatment of a glass surface for improving hydrophobicity using the non-thermal plasma generated by dielectric barrier discharge (DBD) at atmospheric pressure in ambient air is conducted, and the surface properties of the glass before and after the DBD treatment are studied by using contact angle measurement, surface resistance measurement and wet flashover voltage tests. The effects of the applied voltage and time duration of DBD on the surface modification are studied, and the optimal conditions for the treatment are obtained. It is found that a layer of hydrophobic coating is formed on the glass surface after spraying a thin layer of silicone oil and undergoing the DBD treatment, and the improvement of hydrophobicity depends on DBD voltage and treating time. It seems that there exists an optimum treating time for a certain applied voltage of DBD during the surface treatment. The test results of thermal aging and chemical aging show that the hydrophobic layer has quite stable characteristics. The interaction mechanism between the DBD plasma and the glass surface is discussed. It is concluded that CH3 and large molecule radicals can react with the radicals in the glass surface to replace OH, and the hydrophobicity of the glass surface is improved accordingly

  9. Improving Hydrophobicity of Glass Surface Using Dielectric Barrier Discharge Treatment in Atmospheric Air

    Institute of Scientific and Technical Information of China (English)

    FANG Zhi; QIU Yuchang; WANG Hui; E. KUFFEL

    2007-01-01

    Non-thermal plasmas under atmospheric pressure are of great interest in industrial applications, especially in material surface treatment. In this paper, the treatment of a glass surface for improving hydrophobicity using the non-thermal plasma generated by dielectric barrier discharge (DBD) at atmospheric pressure in ambient air is conducted, and the surface properties of the glass before and after the DBD treatment are studied by using contact angle measurement, surface resistance measurement and wet flashover voltage tests. The effects of the applied voltage and time duration of DBD on the surface modification are studied, and the optimal conditions for the treatment are obtained. It is found that a layer of hydrophobic coating is formed on the glass surface after spraying a thin layer of silicone oil and undergoing the DBD treatment, and the improvement of hydrophobicity depends on DBD voltage and treating time. It seems that there exists an optimum treating time for a certain applied voltage of DBD during the surface treatment. The test results of thermal aging and chemical aging show that the hydrophobic layer has quite stable characteristics. The interaction mechanism between the DBD plasma and the glass surface is discussed. It is concluded that CH3 and large molecule radicals can react with the radicals in the glass surface to replace OH, and the hydrophobicity of the glass surface is improved accordingly.

  10. Study on the surface oxidation of uranium in different gaseous atmospheres

    International Nuclear Information System (INIS)

    The studying for the surface oxidation of uranium and oxide by X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), secondary ion mass spectroscopy (SIMS), and the surface oxidation of uranium in different gaseous atmospheres such as O2, H2, CO, CO2, H2O(v) and air were reviewed. The surface oxidation of uranium is greatly influenced by a number of parameters including atmospheric temperature, pressure, diffusion of adsorbed gas atoms through the oxide layer, surface and interface chemical component, and defect structure and electron nature of the oxide layer. The initial oxidation mechanism and kinetics have been discussed. Suggestions for future work have also been presented. (32 refs., 7 figs., 5 tabs.)

  11. White Layer of Hard Turned Surface by Sharp CBN Tool

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xue-ping; SONG He-chuan; C.Richard Liu

    2005-01-01

    White layers in hard turned surfaces were identified and measured as a function of turning parameters based on the Taguchi method. It reveals that white layers generate on the machine surface in the absence of tool flank wear, and white layer depth varies with the different combinations of hard turning parameters. Turning speed has the most important impact on white layer depth, feed rate follows, and cutting depth at last. The white layer generation consequently suggests a strong couple relation to the heat generation and thermal process of hard turning operation. White layer disappears under an optimal combination of turning parameters by Taguchi method. It suggests that a superior surface integrity without white layer is feasible under some selected combinations of turning parameters by a sharp CBN cutting tool.

  12. 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......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...

  13. Height of layer of intense turbulent heat exchange under conditions of stable atmospheric stratification

    Science.gov (United States)

    Kamardin, A. P.; Nevzorova, I. V.; Odintsov, S. L.

    2015-11-01

    In the work, we consider estimates of the height of layer of intense turbulent heat exchange in stably stratified atmospheric boundary layer, made with the use of meteorological acoustic radar (sodar). Dependence of this height on temperature gradient is analyzed. Current temperature stratification of the atmosphere in the layer with height up to 1 000 m was determined with the help of MTP-5 meteorological temperature profiler.

  14. Gradient Ni-Cr-Mo-Nb surface alloying layer

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Xu [Key Lab. of Beam Technology and Material Modification of Ministry of Education, Inst. of Low Energy Nuclear Physics, Beijing Normal Univ., Beijing Radiation Center, Beijing, BJ (China); Xie Xishan [School of Materials Science and Technology, Univ. of Science and Technology Beijing (China); Xu Zhong [Research Inst. of Surface Engineering, Taiyuan Univ. of Technology (China)

    2003-07-01

    In this paper the gradient surface-alloying layer similar to superalloy Inconel 625 is obtained at the surface of three kind steels (low carbon steel, industrial pure iron, stainless steel 304) by using Double Glow Plasma Surface Alloying Technique. These gradient superalloy surface alloying layers are formed by high temperature diffusion of alloy elements at Double Glow Plasma Surface Alloying. The chemical composition of surface layer can be controlled by source electrode material and technological parameters such as power of source electrode and cathode and processing times etc. The microstructures analyzed by XRD show that the alloying layer consists of {gamma} matrix and some precipitates (Laves intermetallic phase etc.) which depends on the local area composition. The corrosion resistance of nickel base surface alloying layer has been investigated by electrochemical method in 3.5%NaCl and 5%HCl solution. The results indicate: the corrosion resistance of surface alloying layer formed at pure iron substrate is better than that of nickel base superalloy Inconel 625. The results of 200 h exposure tests in 20%H{sub 2}SO{sub 4} and 20%HCl solution show that the corrosion rates of surface alloying layer on pure iron are also equal to that of nickel base alloy Inconel 625 and one order of magnitude lower than that of AISI304 stainless steel. (orig.)

  15. Surface influence on the marine and coastal Antarctic atmosphere

    OpenAIRE

    Valkonen, Teresa

    2013-01-01

    The Antarctic region plays an important role in the global climate system, and it contributes to the future of global climate through changes in regional factors, such as sea ice, atmospheric circulation patterns and moisture distribution. The aim of this thesis is to improve the understanding of the influence of the Earth surface on the marine and coastal Antarctic atmosphere. The thesis outlines the characteristics of typical phenomena of the Antarctic environment both near the surface and ...

  16. The Mobile Buoy: An Autonomous Surface Vehicle for Integrated Ocean-Atmosphere Studies

    Science.gov (United States)

    Orton, P. M.; McGillis, W. R.; Moisan, J. R.; Higinbotham, J. R.; Schirtzinger, C.

    2009-05-01

    A solar-powered Autonomous Surface Vessel (ASV) called OASIS (Ocean-Atmosphere Sensor Integration System) has been developed that makes measurements spanning the ocean mixed layer and lower atmospheric surface layer. An OASIS ASV can be remotely commanded to act as a boat, drifter, or untethered buoy (when programmed to keep at a station). OASIS has performed cross-shelf transect surveys within the mid-Atlantic Bight (63 km), Gulf of Maine, and additional field tests to develop techniques to map harmful algal blooms. One example of the utility of the OASIS ASV is with carbon dioxide (CO2) fluxes - predicting future climate change will require that scientists understand what controls exchanges of carbon dioxide between the atmosphere and ocean interior. OASIS measurements from the Gulf of Maine transect included surface ocean CO2 partial pressures from 320 to 670 μatm, air-sea CO2 sea-to-air fluxes from -3.2 to +12.2 mmol m2 d-1, upper ocean currents (0-50 m depth), surface ocean fluorescence, temperature and salinity, and several additional measurements. We are also installing a cabled, autonomous ocean mixed- layer hydrographic profiling system for future deployments. The complete integration of atmosphere and ocean measurements onboard an autonomous navigating vehicle is a key advance for ocean observation technology and observational science programs. ASVs have great potential for ocean and climate studies, and can become a major component of earth observation systems in the coming decades.

  17. Ion doping of surface layers in conducting electrical materials

    International Nuclear Information System (INIS)

    The presented article gives basic component elements of an implanter MKPCz-99, its parameters and methods for doping surface layers of conducting electrical materials. The discussed device makes possible to dope the materials with ions of gaseous elements. At the application of cones made of solid-element sheets it is possible to perform doping with atoms that do not chemically react with the modified material. By performing voltage drop measurements with a specialized circuit between a movable testing electrode and the modified sample the dependence of transition resistance on pressure force of the testing electrode on the sample can be determined. The testing can be performed at the current passage of a determined value for surfaces modified with ions of gaseous elements or atoms of solid elements. A computer stand for switch testing makes possible to measure temperature of switch contacts and voltage drop at the contact and thereby to determine contact resistance of a switch depending on the number of switch cycles (ON-OFF). Pattern recording of current and voltage at the switch contacts and the application of an adequate computer software makes possible to determined the value of energy between fixed and moving contacts at their getting apart. In order to eliminate action of the environment onto the switch operation measurements can be performed at placing the tested switch together with the driving system in an atmosphere of noble gas like argon. (authors)

  18. Large Eddy Simulation of Pollen Transport in the Atmospheric Boundary Layer

    Science.gov (United States)

    Chamecki, Marcelo; Meneveau, Charles; Parlange, Marc B.

    2007-11-01

    The development of genetically modified crops and questions about cross-pollination and contamination of natural plant populations enhanced the importance of understanding wind dispersion of airborne pollen. The main objective of this work is to simulate the dispersal of pollen grains in the atmospheric surface layer using large eddy simulation. Pollen concentrations are simulated by an advection-diffusion equation including gravitational settling. Of great importance is the specification of the bottom boundary conditions characterizing the pollen source over the canopy and the deposition process everywhere else. The velocity field is discretized using a pseudospectral approach. However the application of the same discretization scheme to the pollen equation generates unphysical solutions (i.e. negative concentrations). The finite-volume bounded scheme SMART is used for the pollen equation. A conservative interpolation scheme to determine the velocity field on the finite volume surfaces was developed. The implementation is validated against field experiments of point source and area field releases of pollen.

  19. The role of interfacial water layer in atmospherically relevant charge separation

    Science.gov (United States)

    Bhattacharyya, Indrani

    Charge separation at interfaces is important in various atmospheric processes, such as thunderstorms, lightning, and sand storms. It also plays a key role in several industrial processes, including ink-jet printing and electrostatic separation. Surprisingly, little is known about the underlying physics of these charging phenomena. Since thin films of water are ubiquitous, they may play a role in these charge separation processes. This talk will focus on the experimental investigation of the role of a water adlayer in interfacial charging, with relevance to meteorologically important phenomena, such as atmospheric charging due to wave actions on oceans and sand storms. An ocean wave generates thousands of bubbles, which upon bursting produce numerous large jet droplets and small film droplets that are charged. In the 1960s, Blanchard showed that the jet droplets are positively charged. However, the charge on the film droplets was not known. We designed an experiment to exclusively measure the charge on film droplets generated by bubble bursting on pure water and aqueous salt solution surfaces. We measured their charge to be negative and proposed a model where a slight excess of hydroxide ions in the interfacial water layer is responsible for generating these negatively charged droplets. The findings from this research led to a better understanding of the ionic disposition at the air-water interface. Sand particles in a wind-blown sand layer, or 'saltation' layer, become charged due to collisions, so much so, that it can cause lightning. Silica, being hydrophilic, is coated with a water layer even under low-humidity conditions. To investigate the importance of this water adlayer in charging the silica surfaces, we performed experiments to measure the charge on silica surfaces due to contact and collision processes. In case of contact charging, the maximum charge separation occurred at an optimum relative humidity. On the contrary, in collisional charging process, no

  20. Three-Dimensional Motion Estimation of Atmospheric Layers From Image Sequences

    OpenAIRE

    Héas, Patrick; Memin, Etienne

    2008-01-01

    International audience In this paper, we address the problem of estimating three-dimensional motions of a stratified atmosphere from satellite image sequences. The analysis of three-dimensional atmospheric fluid flows associated with incomplete observation of atmospheric layers due to the sparsity of cloud systems is very difficult. This makes the estimation of dense atmospheric motion field from satellite images sequences very difficult. The recovery of the vertical component of fluid mot...

  1. STAMPI, Application to the Coupling of Atmosphere Model (MM5) and Land-surface Model (SOLVEG)

    International Nuclear Information System (INIS)

    Description of program or function: A new method to couple atmosphere and land-surface models using the message passing interface (MPI) was proposed to develop an atmosphere-land model for studies on heat, water, and material exchanges around the land surface. A non-hydrostatic atmospheric dynamic model of Pennsylvania State University and National Center for Atmospheric Research (PUS/NCAR-MM5) and a detailed land surface model (SOLVEG) including the surface-layer atmosphere, soil, and vegetation developed at Japan Atomic Energy Research Institute (JAERI) are used as the atmosphere and land-surface models, respectively. Concerning the MPI, a message passing library named STAMPI developed at JAERI that can be used between different parallel computers is used. The models are coupled by exchanging calculation results by using MPI on their independent parallel calculations. The modifications for this model coupling are easy, simply adding some modules for data exchanges to each model code without changing each model's original structure. Moreover, this coupling method is flexible and allows the use of independent time step and grid interval for each model

  2. Turbulence Generation in the Atmospheric Boundary Layer and Limitations of the Monin-Obukhov Similarity Theory

    Science.gov (United States)

    Sun, Jielun; Lenschow, Donald; LeMone, Margaret; Mahrt, Larry

    2015-04-01

    Turbulent fluxes from the Cooperative Atmosphere-Surface Exchange Study in 1999 (CASES-99) field experiment are further analyzed for both day- and nighttime as a follow-on to the investigation of the nighttime turbulence in Sun et al. (2012). The behavior of momentum and heat fluxes is investigated as functions of wind speed and the bulk temperature difference between observation heights and the surface. Vertical variations of momentum and heat flux at a given height z are correlated and are explained in terms of the energy and heat balance in a layer above the ground surface in which the surface heating/cooling and momentum sink need to be included. In addition, the surface also plays an important role in constraining the size of the dominant turbulent eddies, which is directly related to turbulence strength and the length scale of turbulence generation. The turbulence generation is not related to local vertical gradients especially under neutral condition as assumed in Monin-Obukhov similarity theory. Based on the observed relationships between momentum and heat fluxes, a new bulk formula for turbulence parameterization is developed to mainly examine the above-mentioned surface effects on vertical variation of turbulent momentum and heat fluxes. The new understanding of the observed relationships between these turbulent variables and mean variables explains the observed nighttime turbulence regime change observed in Sun et al. (2012) as well as the daytime momentum and heat flux variations with height up to the maximum observation height of 55 m.

  3. Surface layer response to topographic solar shading in Antarctica's dry valleys

    Science.gov (United States)

    Katurji, Marwan; Zawar-Reza, Peyman; Zhong, Shiyuan

    2013-11-01

    The effects of topographic shading on local flow transitioning and atmospheric surface layer properties are investigated using observational data from the Miers Valley, one of the dry valleys of Antarctica. A unique data set was collected during a 9 day period in the summer of 2012 using an eddy covariance system and a sound detection and ranging that provided vertical profiles of wind and turbulence characteristics in the surface layer and the lower part of the boundary layer within the Miers Valley. This data set is ideal for investigating the dynamics of flow transitioning due to topographic shading, without the atmosphere experiencing complete darkness. The lack of atmospheric humidity, soil moisture, and surface vegetation in the dry valleys creates an atmosphere within which the microclimatic responses are amplified, and as a result, the valley atmosphere is extremely sensitive to solar radiation. The entire measured valley boundary layer (up to 250 m above ground level) feels the transition from an unstable to a stable stratification as the surface temperature drops by 10°C in response to the topographic shading. Wavelet analysis reveals the dynamics of flow deceleration, stagnation, and oscillations as the flow transitions from an unstable to a stable boundary layer. The larger air mass (along valley) scales to the longer terrain fetch, and as the shade is cast over the valley, it retains some of the longer wavelengths of the flow. The cross-valley component influenced by the slopes is quicker to adjust to short-period oscillations and takes around three more hours before it couples with the oscillatory pattern of the along-valley flow.

  4. 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.

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

    International Nuclear Information System (INIS)

    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

  6. Robotic exploration of the surface and atmosphere of Venus

    Science.gov (United States)

    Landis, Geoffrey A.

    2006-10-01

    Venus, the “greenhouse planet,” is a scientifically fascinating place. The US National Academies of Sciences listed a Venus surface in situ explorer as one of the highest priority planetary science missions. A mission concept for 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 50 days on the surface of Venus, and also solar-powered airplanes to probe the middle atmosphere. At 450C, and with 90 atmospheres of pressure of carbon-dioxide atmosphere, the surface of Venus is a hostile place for operation of a probe. The mission design trade-off looked at three options for surface operation: developing technology to operate at Venus surface temperatures, using an active refrigeration system to lower the temperature inside a “cool electronics enclosure,” or developing a hybrid system, where the computer system and the most temperature-sensitive electronics are on an aerial platform at lower temperature, and less sophisticated surface electronics operate at the ambient surface temperature. This paper presents the mission objectives, discusses the technology options for materials, power systems, electronics, and instruments, and presents a short summary of the mission.

  7. Wind tunnel experiment of drag of isolated tree models in surface boundary layer

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    For very sparse tree land individual tree was the basic element of interaction between atmosphere and the surface. Drag of isolated tree was preliminary aerodynamic index for analyzing the atmospheric boundary layer of this kind of surface. A simple pendulum method was designed and carried out in wind tunnel to measure drag of isolated tree models according to balance law of moment of force. The method was easy to conduct and with small error. The results showed that the drag and drag coefficient of isolated tree increased with decreasing of its permeability or porosity. Relationship between drag coefficient and permeability of isolated tree empirically was expressed by quadric curve.

  8. Thin surface layers of SiO2 obtained from tetraethoxysilane (TEOS) in electric discharges stabilized by a dielectric barrier

    International Nuclear Information System (INIS)

    The reported research was devoted to the process of thin layer deposition in a discharge at atmospheric pressure stabilized by a dielectric barrier. Thin surface layers composed mainly of silicon dioxide were produced by polycondensation of tetraethoxysilane vapor in mixtures with helium gas with a small amount of oxygen. The influence was studied of the voltage applied and of the time elapsed in the deposition process, on the thickness of the layer, as were the changes of composition of the deposited layers during and after storage. It is shown that good passivating pinhole-free silicon oxide layers can be produced in surface barrier discharges. (J.U.)

  9. Wettability of terminally anchored polymer brush layers on a polyamide surface.

    Science.gov (United States)

    Varin, Kari J Moses; Cohen, Yoram

    2014-12-15

    Surface wettability of terminally anchored hydrophilic polymer brush layers on polyamide-silicon (PA-Si) surfaces was evaluated with respect to surface topography at the nanoscale. Hydrophilic polyvinylpyrrolidone (PVP) and polyacrylamide (PAAm) brush layers were synthesized via graft polymerization onto a PA-Si surface previously activated by surface treatment with atmospheric pressure plasma. Hydrophilicity (or wettability) of the PA substrate, as quantified by the free energy of hydration, was increased upon surface coverage with the PVP and PAAm brush layers by 13-24% (-101.4 to -111.3 mJ/m(2)) and 19-37% (-106.1 to -122.4 mJ/m(2)), respectively. Surface hydrophilicity increased with both increasing surface roughness (0.55-2.89 nm and 1.54-5.84 nm for PVP and PAAm, respectively) and polymer volume (1.3×10(6)-7.3×10(6) nm(3)/μm(2) and 3.3×10(6)-2.8×10(7) nm(3)/μm(2) for PVP and PAAm surfaces, respectively). The present study suggests that a specific level of surface wettability can be attained by tailor-designing the polymer brush layer's physicochemical characteristics (e.g., surface roughness, wettability, and polymer water affinity) by adjusting surface topography and surface chemistry, which are controlled by surface activation and polymerization conditions. The above indicates that there is merit in structuring various surfaces with hydrophilic brush layers to increase surface wettability in membrane filtration, biomedical devices, and lubrication applications. PMID:25305445

  10. Detection of CO in Triton's atmosphere and the nature of surface-atmosphere interactions

    CERN Document Server

    Lellouch, E; Sicardy, B; Ferron, S; Käufl, H -U

    2010-01-01

    Triton possesses a thin atmosphere, primarily composed of nitrogen, sustained by the sublimation of surface ices. The goal is to determine the composition of Triton's atmosphere and to constrain the nature of surface-atmosphere interactions. We perform high-resolution spectroscopic observations in the 2.32-2.37 $\\mu$m range, using CRIRES at the VLT. From this first spectroscopic detection of Triton's atmosphere in the infrared, we report (i) the first observation of gaseous methane since its discovery in the ultraviolet by Voyager in 1989 and (ii) the first ever detection of gaseous CO in the satellite. The CO atmospheric abundance is remarkably similar to its surface abundance, and appears to be controlled by a thin, CO-enriched, surface veneer resulting from seasonal transport and/or atmospheric escape. The CH$_4$ partial pressure is several times larger than inferred from Voyager. This confirms that Triton's atmosphere is seasonally variable and is best interpreted by the warming of CH$_4$-rich icy grains ...

  11. TEM studies of the nitrided Ni-Ti surface layer.

    Science.gov (United States)

    Lelatko, J; Paczkowski, P; Wierzchoń, T; Morawiec, H

    2006-09-01

    The structure of surface layer, obtained on the nearly equiatomic Ni-Ti alloy after nitriding under glow discharge conditions at temperatures 700 or 800 degrees C, was investigated. The structural characterization of the intruded layer was performed on cross-sectional thin foils by the use of the transmission and scanning electron microscopes. The obtained results show that the nitrided layers consist mainly of the nanocrystalline TiN phase and small amount of Ti(2)N. Between the nitrided layers and beta-NiTi matrix an intermediate Ti(2)Ni phase layer was observed. PMID:17059538

  12. Tunable hybrid surface waves supported by a graphene layer

    CERN Document Server

    Iorsh, Ivan; Belov, Pavel; Kivshar, Yuri

    2012-01-01

    We study surface waves localized near a surface of a semi-infinite dielectric medium covered by a layer of graphene in the presence of a strong external magnetic field. We demonstrate that both TE-TM hybrid surface plasmons can propagate along the graphene surface. We analyze the effect of the Hall conductivity on the disper- sion of hybrid surface waves and suggest a possibility to tune the plasmon dispersion by the magnetic field.

  13. On the marine atmospheric boundary layer characteristics over Bay of Bengal and Arabian Sea during the Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB)

    Indian Academy of Sciences (India)

    Denny P Alappattu; D Bala Subrahamanyam; P K Kunhikrishnan; K M Somayaji; G S Bhat; R Venkatesan; C B S Dutt; A Bagavath Singh; V K Soni; A S Tripathi

    2008-07-01

    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 during this campaign. The latitudinal variation of the surface layer turbulent fluxes is also described in detail.

  14. A Method for Deriving the Boundary Layer Mixing Height from MODIS Atmospheric Profile Data

    Directory of Open Access Journals (Sweden)

    Xueliang Feng

    2015-09-01

    Full Text Available The planetary boundary layer is the medium of energy, moisture, momentum and pollutant exchange between the surface and the atmosphere. In this paper, a method to derive the boundary layer mixing height (MH was introduced and applied over the Heihe river basin. Atmospheric profiles from the MODerate Resolution Imaging Sepctroradiometer (MODIS instrument onboard the NASA-Aqua satellite were used for the high spatial resolution of this method. A gap-filling method was used to replace missing MODIS data. In situ MH data were also calculated from HIWATER (Heihe Watershed Allied Telemetry Experimental Research and WATER (Watershed Allied Telemetry Experimental Research observational radiosonde sounding data from 2008 and 2012 using the Richardson number method combined with a subjective method. The MH occurs where there is an abrupt decrease in the MR (water vapor mixing ratio. The minimum vertical gradient of the MR is used to determine the MH. The method has an average RMSE of 370 m under clear skies and convective conditions. The seasonal variation in the MH at the Gaoya radiosonde station is also presented. The study demonstrates that remote sensing methodologies can successfully estimate the MH without the help of field measurements.

  15. Flow around new wind fence with multi-scale fractal structure in an atmospheric boundary layer

    Science.gov (United States)

    McClure, Sarah; Lee, Sang-Joon; Zhang, Wei

    2015-11-01

    Understanding and controlling atmospheric boundary-layer flows with engineered structures, such as porous wind fences or windbreaks, has been of great interest to the fluid mechanics and wind engineering community. Previous studies found that the regular mono-scale grid fence of 50% porosity and a bottom gap of 10% of the fence height are considered to be optimal over a flat surface. Significant differences in turbulent flow structure have recently been noted behind multi-scale fractal wind fences, even with the same porosity. In this study, wind-tunnel tests on the turbulent flow and the turbulence kinetic energy transport of 1D and 2D multi-scale fractal fences under atmospheric boundary-layer were conducted. Velocity fields around the fractal fences were systematically measured using Particle Image Velocimetry to uncover effects of key parameters on turbulent flows around the fences at a Reynolds number of approximately 3.6x104 based on the free-stream speed and fence height. The turbulent flow structures induced by specific 1D/2D multi-scale fractal wind fences were compared to those of a conventional grid fence. The present results would contribute to the design of new-generation wind fences to reduce snow/sand deposition on critical infrastructure such as roads and bridges.

  16. THE SIMULATION OF FINE SCALE NOCTURNAL BOUNDARY LAYER MOTIONS WITH A MESO-SCALE ATMOSPHERIC MODEL

    Energy Technology Data Exchange (ETDEWEB)

    Werth, D.; Kurzeja, R.; Parker, M.

    2009-04-02

    A field project over the Atmospheric Radiation Measurement-Clouds and Radiation Testbed (ARM-CART) site during a period of several nights in September, 2007 was conducted to explore the evolution of the low-level jet (LLJ). Data was collected from a tower and a sodar and analyzed for turbulent behavior. To study the full range of nocturnal boundary layer (NBL) behavior, the Regional Atmospheric Modeling System (RAMS) was used to simulate the ARM-CART NBL field experiment and validated against the data collected from the site. This model was run at high resolution, and is ideal for calculating the interactions among the various motions within the boundary layer and their influence on the surface. The model reproduces adequately the synoptic situation and the formation and dissolution cycles of the low-level jet, although it suffers from insufficient cloud production and excessive nocturnal cooling. The authors suggest that observed heat flux data may further improve the realism of the simulations both in the cloud formation and in the jet characteristics. In a higher resolution simulation, the NBL experiences motion on a range of timescales as revealed by a wavelet analysis, and these are affected by the presence of the LLJ. The model can therefore be used to provide information on activity throughout the depth of the NBL.

  17. Generation and characterization of surface layers on acoustically levitated drops.

    Science.gov (United States)

    Tuckermann, Rudolf; Bauerecker, Sigurd; Cammenga, Heiko K

    2007-06-15

    Surface layers of natural and technical amphiphiles, e.g., octadecanol, stearic acid and related compounds as well as perfluorinated fatty alcohols (PFA), have been investigated on the surface of acoustically levitated drops. In contrast to Langmuir troughs, traditionally used in the research of surface layers at the air-water interface, acoustic levitation offers the advantages of a minimized and contact-less technique. Although the film pressure cannot be directly adjusted on acoustically levitated drops, it runs through a wide pressure range due to the shrinking surface of an evaporating drop. During this process, different states of the generated surface layer have been identified, in particular the phase transition from the gaseous or liquid-expanded to the liquid-condensed state of surface layers of octadecanol and other related amphiphiles. Characteristic parameters, such as the relative permeation resistance and the area per molecule in a condensed surface layer, have been quantified and were found comparable to results obtained from surface layers generated on Langmuir troughs. PMID:17376468

  18. Validation of technique to hyperspectrally characterize the lower atmosphere with limited surface observations

    Science.gov (United States)

    Randall, Robb M.; Fiorino, Steven T.; Via, Michelle F.; Downs, Adam D.

    2011-06-01

    This paper demonstrates the capability of AFIT/CDE's Laser Environmental Effects Definition and Reference (LEEDR) model to accurately characterize the meteorological parameters and radiative transfer effects of the atmospheric boundary layer with only surface observations of temperature, pressure, and humidity. The LEEDR model is a fastcalculating, first principles, worldwide surface to 100 km, atmospheric propagation and characterization package. This package enables the creation of profiles of temperature, pressure, water vapor content, optical turbulence, atmospheric particulates and hydrometeors as they relate to line-by-line layer transmission, path and background radiance at wavelengths from the ultraviolet to radio frequencies. Physics-based cloud and precipitation characterizations are coupled with a probability of cloud free line of sight (CFLOS) algorithm for air-to-air, air-to-surface, and surface-to-air (or space) look angles. In general, LEEDR defines the well-mixed atmospheric boundary layer with a worldwide, probabilistic surface climatology based on season and time of day, and then computes the radiative transfer and propagation effects from the vertical profile of meteorological variables. However, the LEEDR user can also directly input surface observations. This research compares the LEEDR vertical profiles created from input surface observations to actual observations from balloon launches. Results are then compared to the LEEDR ExPERT climatological sounding for the same time of day and season. RMSE are calculated and it was found that closer for those profiles made from surface observations than those made from climatological data for the same season and time. Impacts of those differences are shown with a relevant tactical scenario in AFIT/CDE HELEEOS program.

  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. Improve oxidation resistance at high temperature by nanocrystalline surface layer

    Science.gov (United States)

    Xia, Z. X.; Zhang, C.; Huang, X. F.; Liu, W. B.; Yang, Z. G.

    2015-08-01

    An interesting change of scale sequence occurred during oxidation of nanocrystalline surface layer by means of a surface mechanical attrition treatment. The three-layer oxide structure from the surface towards the matrix is Fe3O4, spinel FeCr2O4 and corundum (Fe,Cr)2O3, which is different from the typical two-layer scale consisted of an Fe3O4 outer layer and an FeCr2O4 inner layer in conventional P91 steel. The diffusivity of Cr, Fe and O is enhanced concurrently in the nanocrystalline surface layer, which causes the fast oxidation in the initial oxidation stage. The formation of (Fe,Cr)2O3 inner layer would inhabit fast diffusion of alloy elements in the nanocrystalline surface layer of P91 steel in the later oxidation stage, and it causes a decrease in the parabolic oxidation rate compared with conventional specimens. This study provides a novel approach to improve the oxidation resistance of heat resistant steel without changing its Cr content.

  1. CVD Delta-Doped Boron Surface Layers for Ultra-Shallow Junction Formation

    OpenAIRE

    Sarubbi, F.; Nanver, L.K.; Scholtes, T.L.M.

    2006-01-01

    A new doping technique is presented that uses a pure boron atmospheric/low-pressure chemical vapor deposition (AP/LPCVD) in a commercially available epitaxial reactor to form less than 2-nm-thick δ-doped boron-silicide (BxSi) layers on the silicon surface. For long exposure B segregates at the surface to form a very slow growing amorphous layer of pure B (α-B). The electrical properties of the as-deposited α- B/BxSi stack have been studied by fabricating and measuring diodes where the B depos...

  2. 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 apply...... from the pattern size and filling factor of the active material are analyzed for tuned permittivity of the ITO layer. Direct simulation of the device functionality validates optimization design....

  3. Laser nitriding of the surface layer of Ti6Al4V titanium alloy

    Directory of Open Access Journals (Sweden)

    R. Filip

    2008-03-01

    Full Text Available Purpose: The purpose of this paper is modification of the surface layer of the Ti6Al4V titanium alloymicrostructure and properties by laser remelting in nitrogen atmosphere.Design/methodology/approach: Laser treatment was performed on the samples in stream of nitrogen.Microstructure of laser treated layer was investigated by using Epiphot 300 optical microscope and Novascan30 scanning electron microscope. Phase composition was determined using X-ray diffractometry. The roughnessof surface of treated material was examined using topography scanning system T 8000 made by HommelwerkeGMBH. The Vickers hardness under load of 1.96 N was measured on the cross sections of surface layer. The wearproperties of alloyed zone were tested on the testing machine T 08M using ‘pin on disc’ test.Findings: Laser remelting process has produced a surface layer consists of hard ceramics particles of TiN andTi2N phases spaced in martensitic matrix. The hardness of surface layer increases clearly in comparison withuntreated alloy due to formation of TiN and Ti2N particles and depends on the volume fraction of nitrides. Theirmaximum value of the hardness (1500 HV 0.2 occurs on the surface of laser treated zone. Wear resistance of lasernitrided layer increases considerably in relation to base alloy.Research limitations/implications: Research range was limited to microstructure, phase composition,hardness, fractography and wear resistance investigations. To estimate the influence of the laser nitriding processon corrosion resistance of the layer additional examinations will be performed in future research.Practical implications: Laser remelting of titanium alloy in nitrogen atmosphere makes possible to obtain coatingscomposed of ceramic particles spaced in metallic matrix characterised by high hardness and wear resistance.Originality/value: The range of investigation included microstructure, phase composition, hardness as well asfractographic estimation and wear

  4. Impedance of Surface Footings on Layered Ground

    DEFF Research Database (Denmark)

    Andersen, Lars; Clausen, Johan Christian

    2005-01-01

    discussed. Based on the Green's function for a stratified half-space, the impedance of a surface footing with arbitrary shape is computed. A wind turbine foundation is analysed in the frequency range 0 to 3 Hz. Analyses show that soil stratification may lead to a significant changes in the impedance related...

  5. Impedance of Surface Footings on Layered Ground

    DEFF Research Database (Denmark)

    Andersen, Lars; Clausen, Johan

    2007-01-01

    discussed. Based on the Green's function for a stratified half-space, the impedance of a surface footing with arbitrary shape is computed. A wind turbine foundation is analysed in the frequency range 0-3 Hz. Analyses show that soil stratification may lead to significant changes in the impedance related to...

  6. 2nd international conference on ion beam surface layer analysis

    International Nuclear Information System (INIS)

    The papers of this conference are concerned with the fundamental aspects and with the application of surface layer analysis. It is reported amongst others about backscattering analysis, Auger electron spectroscopy, channelling and microprobe. (HPOE)

  7. The Bacterial Surface Layer Provides Protection against Antimicrobial Peptides

    OpenAIRE

    de la Fuente-Núñez, César; Mertens, Jan; Smit, John; Hancock, Robert E. W.

    2012-01-01

    This report describes a previously unrecognized role for bacterial surface layers as barriers that confer protection against antimicrobial peptides. As antimicrobial peptides exist in natural environments, S-layers may provide a bacterial survival mechanism that has been selected for through evolution.

  8. Near-Surface Effects of Free Atmosphere Stratification in Free Convection

    Science.gov (United States)

    Mellado, Juan Pedro; van Heerwaarden, Chiel C.; Garcia, Jade Rachele

    2016-04-01

    The effect of a linear stratification in the free atmosphere on near-surface properties in a free convective boundary layer (CBL) is investigated by means of direct numerical simulation. We consider two regimes: a neutral stratification regime, which represents a CBL that grows into a residual layer, and a strong stratification regime, which represents the equilibrium (quasi-steady) entrainment regime. We find that the mean buoyancy varies as z^{-1/3}, in agreement with classical similarity theory. However, the root-mean-square (r.m.s.) of the buoyancy fluctuation and the r.m.s. of the vertical velocity vary as z^{-0.45} and ln z, respectively, both in disagreement with theory. These scaling laws are independent of the stratification regime, but the depth over which they are valid depends on the stratification. In the strong stratification regime, this depth is about 20 to 25 % of the CBL depth instead of the commonly used 10 %, which we only observe under neutral conditions. In both regimes, the near-surface flow structure can be interpreted as a hierarchy of circulations attached to the surface. Based on this structure, we define a new near-surface layer in free convection, the plume-merging layer, that is conceptually different from the constant-flux layer. The varying depth of the plume-merging layer depending on the stratification accounts for the varying depth of validity of the scaling laws. These findings imply that the buoyancy transfer law needed in mixed-layer and single-column models is well described by the classical similarity theory, independent of the stratification in the free atmosphere, even though other near-surface properties, such as the r.m.s. of the buoyancy fluctuation and the r.m.s. of the vertical velocity, are inconsistent with that theory.

  9. Influence of the characteristics of atmospheric boundary layer on the vertical distribution of air pollutant in China's Yangtze River Delta

    Science.gov (United States)

    Wang, Chenggang; Cao, Le

    2016-04-01

    Air pollution occurring in the atmospheric boundary layer is a kind of weather phenomenon which decreases the visibility of the atmosphere and results in poor air quality. Recently, the occurrence of the heavy air pollution events has become more frequent all over Asia, especially in Mid-Eastern China. In December 2015, the most severe air pollution in recorded history of China occurred in the regions of Yangtze River Delta and Beijing-Tianjin-Hebei. More than 10 days of severe air pollution (Air Quality Index, AQI>200) appeared in many large cities of China such as Beijing, Tianjin, Shijiazhuang and Baoding. Thus, the research and the management of the air pollution has attracted most attentions in China. In order to investigate the formation, development and dissipation of the air pollutions in China, a field campaign has been conducted between January 1, 2015 and January 28, 2015 in Yangtze River Delta of China, aiming at a intensive observation of the vertical structure of the air pollutants in the atmospheric boundary layer during the time period with heavy pollution. In this study, the observation data obtained in the field campaign mentioned above is analyzed. The characteristics of the atmospheric boundary layer and the vertical distribution of air pollutants in the city Dongshan located in the center of Lake Taihu are shown and discussed in great detail. It is indicated that the stability of the boundary layer is the strongest during the nighttime and the early morning of Dongshan. Meanwhile, the major air pollutants, PM2.5 and PM10 in the boundary layer, reach their maximum values, 177.1μg m-3 and 285μg m-3 respectively. The convective boundary layer height in the observations ranges from approximately 700m to 1100m. It is found that the major air pollutants tend to be confined in a relatively shallow boundary layer, which represents that the boundary layer height is the dominant factor for controlling the vertical distribution of the air pollutants. In

  10. Large Eddy Simulation and Field Experiments of Pollen Transport in the Atmospheric Boundary Layer

    Science.gov (United States)

    Chamecki, M.; Meneveau, C.; Parlange, M. B.; van Hout, R.

    2006-12-01

    Dispersion of airborne pollen by the wind has been a subject of interest for botanists and allergists for a long time. More recently, the development of genetically modified crops and questions about cross-pollination and subsequent contamination of natural plant populations has brought even more interest to this field. A critical question is how far from the source field pollen grains will be advected. Clearly the answer depends on the aerodynamic properties of the pollen, geometrical properties of the field, topography, local vegetation, wind conditions, atmospheric stability, etc. As a consequence, field experiments are well suited to provide some information on pollen transport mechanisms but are limited to specific field and weather conditions. Numerical simulations do not have this drawback and can be a useful tool to study pollen dispersal in a variety of configurations. It is well known that the dispersion of particles in turbulent fields is strongly affected by the large scale coherent structures. Large Eddy Simulation (LES) is a technique that allows us to study the typical distances reached by pollen grains and, at the same time, resolve the larger coherent structures present in the atmospheric boundary layer. The main objective of this work is to simulate the dispersal of pollen grains in the atmospheric surface layer using LES. Pollen concentrations are simulated by an advection-diffusion equation including gravitational settling. Of extreme importance is the specification of the bottom boundary conditions characterizing the pollen source over the canopy and the deposition process everywhere else. In both cases we make use of the theoretical profile for suspended particles derived by Kind (1992). Field experiments were performed to study the applicability of the theoretical profile to pollen grains and the results are encouraging. Airborne concentrations as well as ground deposition from the simulations are compared to experimental data to validate the

  11. Decrease of the electric field penetration into the ionosphere due to low conductivity at the near ground atmospheric layer

    OpenAIRE

    M. Ampferer; V. V. Denisenko; Hausleitner, W.; Krauss, S.; G. Stangl; Boudjada, M. Y.; H. K. Biernat

    2010-01-01

    It is well known that lithospheric electromagnetic emissions are generated before earthquakes occurrence. In our study, we consider the physical penetration mechanism of the electric field from the Earth's surface, through the atmosphere-ionosphere layers, and until its detection in space by satellites. A simplified approach is investigated using the electric conductivity equation, i.e., ∇ˆσ·∇Φ)=0 in the case of a vertical inclina...

  12. Evaluation of the similarty functions Fm and Fh for the stable atmospheric boundary layer: range of validity

    OpenAIRE

    Viana, S.; Yague, Carlos; Maqueda, Gregorio; Redondo Apraiz, José Manuel

    2015-01-01

    Poster EGU Turbulent transfer is one of the most important processes in the Atmospheric Boundary Layer (ABL), showing many difficulties in stable situations (SBL): non stationary conditions, presence of internal gravity waves, intermittency, decoupling from the surface fluxes, etc. • The Monin-Obukhov (M-O) Theory is a suitable framework for presenting micrometeorological data, as well as for extrapolating and predicting certain micrometeorological information where direct measure...

  13. Isotope discrimination and partitioning exercises at the scale of the atmospheric boundary layer

    Science.gov (United States)

    Berry, J.; Helliker, B.; Bakwin, P.; Davis, K.; Torn, M.

    2003-12-01

    During the daytime the atmospheric boundary layer (ABL) is typically well mixed by convection up to about 1.5 km and moves across the land about 500 km per day. Underlying ecosystems modify carbon dioxide in the ABL through photosynthesis and respiration, and ABL air is ultimately replaced by air from the overlying free troposphere. Hence, measurements of carbon dioxide and isotopes in the ABL and the free troposphere offer the potential for regionally integrated estimates of isotope discrimination. We use tall-tower and airplane measurements of carbon dioxide and carbon and oxygen isotopes to develop estimates of ABL-scale isotope discrimination. We then utilize ecosystem-level measurements of the isotope ratio of respiration and land surface model estimates of photosynthetic discrimination to deconvolve net carbon dioxide fluxes into the gross components of photosynthesis and respiration at the regional scale.

  14. Nonequilibrium Response of the Daytime Atmospheric Boundary Layer to Mesoscale Forcing

    Science.gov (United States)

    Brasseur, James; Jayaraman, Bajali; Haupt, Sue; Lee, Jared

    2015-11-01

    The essential turbulence structure of the daytime atmospheric boundary layer (ABL) is driven by interactions between shear and buoyancy. A relatively strong inversion layer ``lid'' typically confines the ABL turbulence, whose height grows during the day with increasing surface heat flux (Q0) to ~ 1-2 km before collapsing with Q0 towards the day's end. The 3D ``microscale'' ABL turbulence is forced largely in the horizontal by winds above the capping inversion at the ``mesoscale'' at the O(100) km scale. Whereas the ``canonical'' ABL is in equilibrium and quasi-stationary, quasi-2D weather dynamics at the mesoscale is typically nonstationary at sub-diurnal time scales. We study the consequences of nonstationarity in the quasi-2D mesoscale forcing in horizontal winds and solar heating on the dynamics of ABL turbulence and especially on the potential for significant deviations from the canonical equilibrium state. We apply high-fidelity LES of the dry cloudless ABL over Kansas in July forced at the mesoscale (WRF) with statistical homogeneity in the horizontal. We find significant deviations from equilibrium that appear in a variety of interesting ways. One of the more interesting results is that the changes in mesoscale wind direction at the diurnal time scale can destabilize the ABL and sometimes cause a transition in ABL eddy structure that are normally associated with increased surface heating. Supported by DOE. Computer resources by the Penn State ICS.

  15. Land surface heterogeneity in 3-dimensional atmospheric simulations. Doctoral thesis

    Energy Technology Data Exchange (ETDEWEB)

    Seth, A.

    1995-07-01

    Stand-alone, vectorized version of the Biosphere-Atmosphere Transfer Scheme (VBATS) and a regional climate model (ReGCM2) are used to study the effects of subgrid scale heterogeneity in land surface processes on large scale mean surface fluxes and on mesoscale dynamics, respectively. The thesis is about the interactions of large and small scales within the climate system. We are concerned with two climate subsystems; the land surface and the atmosphere. We shall define large scales as those which can be resolved by current atmospheric general circulation models (grid resolutions of 100-200 km can resolve wavelengths of 400-800 km and larger). Small scales, or subgrid scale processes, are those which cannot be resolved by the resolution of global scale atmospheric models, but may be resolved using models with limited area domains. Our discussion will focus on the physical interactions between land and atmosphere and, specifically, will explore the effects of surface heterogeneity. Chemical exchanges are not considered here, nor is the evolution of the biosphere.

  16. On the Representation of Heterogeneity in Land-Surface-Atmosphere Coupling

    Science.gov (United States)

    de Vrese, Philipp; Schulz, Jan-Peter; Hagemann, Stefan

    2016-07-01

    A realistic representation of processes that are not resolved by the model grid is one of the key challenges in Earth-system modelling. In particular, the non-linear nature of processes involved makes a representation of the link between the atmosphere and the land surface difficult. This is especially so when the land surface is horizontally strongly heterogeneous. In the majority of present day Earth system models two strategies are pursued to couple the land surface and the atmosphere. In the first approach, surface heterogeneity is not explicitly accounted for, instead effective parameters are used to represent the entirety of the land surface in a model's grid box (parameter-aggregation). In the second approach, subgrid-scale variability at the surface is explicitly represented, but it is assumed that the blending height is located below the lowest atmospheric model level (simple flux-aggregation). Thus, in both approaches the state of the atmosphere is treated as being horizontally homogeneous within a given grid box. Based upon the blending height concept, an approach is proposed that allows for a land-surface-atmosphere coupling in which horizontal heterogeneity is considered not only at the surface, but also within the lowest layers of the atmosphere (the VERTEX scheme). Below the blending height, the scheme refines the turbulent mixing process with respect to atmospheric subgrid fractions, which correspond to different surface features. These subgrid fractions are not treated independently of each other, since an explicit horizontal component is integrated into the turbulent mixing process. The scheme was implemented into the JSBACH model, the land component of the Max Planck Institute for Meteorology's Earth-system model, when coupled to the atmospheric general circulation model ECHAM. The single-column version of the Earth system model is used in two example cases in order to demonstrate how the effects of surface heterogeneity are transferred into the

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

    International Nuclear Information System (INIS)

    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

  18. A numerical model of the transport and diffusion of Peronospora tabacina spores in the evolving atmospheric boundary layer

    Science.gov (United States)

    Yao, Chengwei; Pal Arya, S.; Davis, Jerry; Main, Charles E.

    Numerical solutions of the diffusion equation of Peronospora tabacina spores from a finite-area source over flat terrain in the evolving convective boundary layer are presented. Temporal variations in the release of spores, atmospheric stability, wind speed, and eddy diffusivity are considered. The model also includes the vertical variations of wind and eddy diffusivity. The model results indicate that ground level concentrations decrease with time as wind speed and eddy diffusivity increase in the evolving convective boundary layer. The loss of P. tabacina spores due to deposition at the surface also decrease with increasing instability and wind speed. Deposition is found to be particularly important close to the source area.

  19. 3-D water vapor field in the atmospheric boundary layer observed with scanning differential absorption lidar

    OpenAIRE

    Späth, Florian; Behrendt, Andreas; Muppa, Shravan Kumar; Metzendorf, Simon; Riede, Andrea; Wulfmeyer, Volker

    2016-01-01

    High-resolution three-dimensional (3-D) water vapor data of the atmospheric boundary layer (ABL) are required to improve our understanding of land–atmosphere exchange processes. For this purpose, the scanning differential absorption lidar (DIAL) of the University of Hohenheim (UHOH) was developed as well as new analysis tools and visualization methods. The instrument determines 3-D fields of the atmospheric water vapor number density with a temporal resolution of a few secon...

  20. Height of convective layer in planetary atmospheres with condensable and non-condensable greenhouse substances

    OpenAIRE

    Makarieva, A. M.; V. G. Gorshkov; Pujol, T.

    2003-01-01

    Convection reduces greenhouse effect by transporting a certain amount of non-radiative dynamic energy to the upper atmosphere, where this energy dissipates and radiates into space without interaction with greenhouse substances in the lower atmosphere. In this paper we show that the height of the convective layer zc is finite and independent of atmospheric optical thickness τs at large values of the latter. We derive an analytical formula for z...

  1. Neural-estimator for the surface emission rate of atmospheric gases

    OpenAIRE

    Paes, F. F.; Velho, H. F. Campos

    2009-01-01

    The emission rate of minority atmospheric gases is inferred by a new approach based on neural networks. The neural network applied is the multi-layer perceptron with backpropagation algorithm for learning. The identification of these surface fluxes is an inverse problem. A comparison between the new neural-inversion and regularized inverse solution id performed. The results obtained from the neural networks are significantly better. In addition, the inversion with the neural netwroks is fster...

  2. Growth of Large-Area Single- and Bi-Layer Graphene by Controlled Carbon Precipitation on Polycrystalline Ni Surfaces

    OpenAIRE

    Reina, Alfonso; Thiele, Stefan; Jia, Xiaoting; Bhaviripudi, Sreekar; Dresselhaus, Mildred S.; Schaefer, Juergen A.; Kong, Jing

    2009-01-01

    We report graphene films composed mostly of one or two layers of graphene grown by controlled carbon precipitation on the surface of polycrystalline Ni thin films during atmospheric chemical vapor deposition (CVD). Controlling both the methane concentration during CVD and the substrate cooling rate during graphene growth can significantly improve the thickness uniformity. As a result, one- or two- layer graphene regions occupy up to 87% of the film area. Single layer coverage accounts for 5%–...

  3. Erosion resistance of Fe-C-Cr weld surfacing layers

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Fe-C-Cr weld surfacing layers with different compositions and microstructures can be obtained by submerged arc welding with welding wire of the low carbon steel and high alloy bonded flux. With the increase of Cr and C in the layers the microstructures are changed from hypoeutectoid steel, hypereutectoid steel to hypoeutectic iron and hypereutectic iron. When the weld surfacing layers belong to the alloyed cast irons the erosion resistance can be raised with the eutectic increase and the austenite decrease. Good erosion resistance can be obtained when the proportion of the primary carbides is within 10 %. The experimental results lay a foundation to make double-metal percussive plates by surfacing wear resistant layers on the substrates of the low carbon steels.

  4. Surface potential of functionalised nanodiamond layers

    Czech Academy of Sciences Publication Activity Database

    Kratochvílová, Irena; Taylor, A.; Fendrych, František; Kovalenko, Alexander; Nesládek, Miloš

    Warrendale, PA: Materials Research Society, 2010 - (Bergonzo, P.; Butler, J.; Jackman, R.; Loh, K.; Nesladek, M.), 1203-J17-01 /5 s. ( MRS Symposium Proceedings. Vol. 1203). ISBN 978-1-60511-176-6. [ MRS Fall Meeting 2009. Boston (US), 26.11.2009-02.12.2009] R&D Projects: GA ČR GA203/08/1594; GA AV ČR KAN401770651; GA MŠk OC 137; GA AV ČR KAN200100801 Institutional research plan: CEZ:AV0Z10100520 Keywords : nanodiamond * Kelvin probe * surface potential Subject RIV: BM - Solid Matter Physics ; Magnetism http://www. mrs .org/s_mrs/sec_subscribe.asp?CID=24691&DID=303759&action=detail

  5. 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.

  6. Thin film deposition on powder surfaces using atmospheric pressure discharge

    International Nuclear Information System (INIS)

    The deposition of SiOx containing films on NaCl and KBr particles in dielectric barrier discharge under atmospheric pressure was investigated. As precursor hexamethyldisiloxane (HMDSO) and tetraethoxysilane (TEOS) in argon-oxygen gas mixtures were used. The deposited layers were studied by means of light microscopy, SEM and XPS investigations. The particles could be completely covered by SiOx. With increasing oxygen content in the coating the carbon content decreases

  7. Influence of humidity on atmospheric pressure air plasma treatment of aluminium surfaces

    International Nuclear Information System (INIS)

    Atmospheric pressure air plasma treatment of aluminium surfaces and its aging behaviour in different environments were studied. Two types of aluminium samples with different purity and surface morphology were treated using the diffuse coplanar surface barrier discharge (DCSBD). Surface free energy (SFE) and X-ray photoelectron spectroscopy (XPS) have been utilised to characterise changes induced by the plasma. A significant decrease of hydrocarbon contaminants after the plasma treatment was observed. It is concluded that besides the re-contamination by exposure to ambient air, the aging effect, i.e. decrease of the surface free energy of plasma treated surfaces, can be due by dehydration of aluminium oxide layer. Also, it was observed that the humid air plasma treatment resulted in generation of -NOx surface groups.

  8. 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...

  9. Planetary boundary layer depth in Global climate models induced biases in surface climatology

    CERN Document Server

    Davy, Richard

    2014-01-01

    The Earth has warmed in the last century with the most rapid warming occurring near the surface in the arctic. This enhanced surface warming in the Arctic is partly because the extra heat is trapped in a thin layer of air near the surface due to the persistent stable-stratification found in this region. The warming of the surface air due to the extra heat depends upon the amount of turbulent mixing in the atmosphere, which is described by the depth of the atmospheric boundary layer (ABL). In this way the depth of the ABL determines the effective response of the surface air temperature to perturbations in the climate forcing. The ABL depth can vary from tens of meters to a few kilometers which presents a challenge for global climate models which cannot resolve the shallower layers. Here we show that the uncertainties in the depth of the ABL can explain up to 60 percent of the difference between the simulated and observed surface air temperature trends and 50 percent of the difference in temperature variability...

  10. Wind farm performance in conventionally neutral atmospheric boundary layers with varying inversion strengths

    Science.gov (United States)

    Allaerts, Dries; Meyers, Johan

    2014-06-01

    In this study we consider large wind farms in a conventionally neutral atmospheric boundary layer. In large wind farms the energy extracted by the turbines is dominated by downward vertical turbulent transport of kinetic energy from the airflow above the farm. However, atmospheric boundary layers are almost always capped by an inversion layer which slows down the entrainment rate and counteracts boundary layer growth. In a suite of large eddy simulations the effect of the strength of the capping inversion on the boundary layer and on the performance of a large wind farm is investigated. For simulations with and without wind turbines the results indicate that the boundary layer growth is effectively limited by the capping inversion and that the entrainment rate depends strongly on the inversion strength. The power output of wind farms is shown to decrease for increasing inversions.

  11. MAIC-2, a latitudinal model for the Martian surface temperature, atmospheric water transport and surface glaciation

    OpenAIRE

    Greve, Ralf; Grieger, Bjoern; Stenzel, Oliver J.

    2009-01-01

    The Mars Atmosphere-Ice Coupler MAIC-2 is a simple, latitudinal model, which consists of a set of parameterisations for the surface temperature, the atmospheric water transport and the surface mass balance (condensation minus evaporation) of water ice. It is driven directly by the orbital parameters obliquity, eccentricity and solar longitude (Ls) of perihelion. Surface temperature is described by the Local Insolation Temperature (LIT) scheme, which uses a daily and latitude-dependent radiati...

  12. Atmospheric boundary layer top height in South Africa: measurements with lidar and radiosonde compared to three atmospheric models

    Directory of Open Access Journals (Sweden)

    K. Korhonen

    2013-07-01

    Full Text Available Atmospheric lidar measurements were carried out at Elandsfontein measurement station, on the eastern Highveld approximately 150 km east of Johannesburg in South Africa (SA throughout 2010. The height of the planetary boundary layer (PBL top was continuously measured using a~Raman lidar, PollyXT (POrtabLe Lidar sYstem eXTended. High atmospheric variability together with a large surface temperature range and significant seasonal changes in precipitation were observed, which had an impact on the vertical mixing of particulate matter (PM, and hence, on the PBL evolution. The results were compared to radio soundings, CALIOP (Cloud–Aerosol Lidar with Orthogonal Polarization space-borne lidar measurements and three atmospheric models that followed different approaches to determine the PBL top height. These models included two weather forecast models operated by ECMWF (European Centre for Medium-range Weather Forecasts and SAWS (South African Weather Service and one mesoscale prognostic meteorological and air pollution regulatory model TAPM (The Air Pollution Model. The ground-based lidar used in this study was operational for 4935 h during 2010 (49% of the time. The PBL top height was detected 86% of the total measurement time (42% of the total time. Large seasonal and diurnal variations were observed between the different methods utilised. Comparison of lidar measurements to the models indicated that the ECMWF model agreed the best with mean absolute difference of 15.4%, while the second best correlation was with the SAWS model with corresponding difference of 20.1%. TAPM was found to have a tendency to underestimate the PBL top height. The wind speeds in SAWS operated and TAPM models were strongly underestimated which probably led to underestimation of the vertical wind and turbulence and thus underestimation of the PBL top height. High variation was found when lidar measurements were compared to radiosonde measurements. This could be partially due

  13. 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)

  14. Coherent structures in the Es layer and neutral middle atmosphere

    Czech Academy of Sciences Publication Activity Database

    Mošna, Zbyšek; Koucká Knížová, Petra; Potužníková, Kateřina

    136 B, December (2015), s. 155-162. ISSN 1364-6826 R&D Projects: GA ČR(CZ) GA15-24688S; GA ČR(CZ) GAP209/12/2440 Institutional support: RVO:68378289 Keywords : critical frequency foEs * mesospheric temperature * mesospheric winds * planetary waves * Rossby mode * sporadic layer * stratospheric temperature Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.474, year: 2014 http://www.sciencedirect.com/science/article/pii/S1364682615001273

  15. Coherent structures in the Es layer and neutral middle atmosphere

    Czech Academy of Sciences Publication Activity Database

    Mošna, Zbyšek; Koucká Knížová, Petra; Kouba, Daniel; Potužníková, Kateřina

    Prague: International Union of Geodesy and Geophysics, 2015. A12p-155. [Earth and Environmental Sciences for Future Generations. General Assembly of International Union of Geodesy and Geophysics /26./. 22.06.2015-02.07.2015, Prague] Institutional support: RVO:68378289 Keywords : ionospheric Es layer * coherent structures Subject RIV: DG - Athmosphere Sciences, Meteorology http://www.iugg2015prague.com/abstractcd/data/HtmlApp/main.html#0

  16. Surface modification of polymeric materials by cold atmospheric plasma jet

    Energy Technology Data Exchange (ETDEWEB)

    Kostov, K.G., E-mail: kostov@feg.unesp.br [Faculty of Engineering in Guaratinguetá–FEG, Universidade Estadual Paulista–UNESP Guaratiguetá, 12516-410, SP (Brazil); Nishime, T.M.C.; Castro, A.H.R. [Faculty of Engineering in Guaratinguetá–FEG, Universidade Estadual Paulista–UNESP Guaratiguetá, 12516-410, SP (Brazil); Toth, A. [Institute of Material and Environmental Chemistry, Hungarian Academy of Science P.O. Box 17, H-1525, Budapest (Hungary); Hein, L.R.O. [Faculty of Engineering in Guaratinguetá–FEG, Universidade Estadual Paulista–UNESP Guaratiguetá, 12516-410, SP (Brazil)

    2014-09-30

    Highlights: • We investigate polymer surface modification by atmospheric pressure plasma jet APPJ. • Jet operation conditions for uniform surface modification were determined. • The APPJ added O atoms to the polymer surface and also enhanced the roughness. • The degree of polymer surface modification by APPJ and DBD were compared. • The APPJ is more efficient in attaching O atoms and produces less polymer fragments. - Abstract: In this work we report the surface modification of different engineering polymers, such as, polyethylene terephthalate (PET), polyethylene (PE) and polypropylene (PP) by an atmospheric pressure plasma jet (APPJ). It was operated with Ar gas using 10 kV, 37 kHz, sine wave as an excitation source. The aim of this study is to determine the optimal treatment conditions and also to compare the polymer surface modification induced by plasma jet with the one obtained by another atmospheric pressure plasma source – the dielectric barrier discharge (DBD). The samples were exposed to the plasma jet effluent using a scanning procedure, which allowed achieving a uniform surface modification. The wettability assessments of all polymers reveal that the treatment leads to reduction of more than 40° in the water contact angle (WCA). Changes in surface composition and chemical bonding were analyzed by x-ray photoelectron spectroscopy (XPS) and Fourier-Transformed Infrared spectroscopy (FTIR) that both detected incorporation of oxygen-related functional groups. Surface morphology of polymer samples was investigated by Atomic Force Microscopy (AFM) and an increase of polymer roughness after the APPJ treatment was found. The plasma-treated polymers exhibited hydrophobic recovery expressed in reduction of the O-content of the surface upon rinsing with water. This process was caused by the dissolution of low molecular weight oxidized materials (LMWOMs) formed on the surface as a result of the plasma exposure.

  17. Predictability in France : atmospheric forcing or land surface initial conditions?

    Science.gov (United States)

    Singla, S.; Martin, E.; Céron, J.-P.; Regimbeau, F.

    2010-09-01

    A first study of a hydrological forecasting suite has already been done at seasonal time scales over France (Céron and al., 2010) in a context of adaptation for water resources management. The results showed the feasibility of hydrological seasonal forecasts by forcing the hydrometeorological model Safran-Isba-Modcou (SIM) with seasonal atmospheric forecasts from the DEMETER project. Scores were better for hydrological variables than for atmospheric variables for four river catchments for the spring season. The purpose of the present study is to quantify the sources of predictability of the hydrometeorological system. Two experiences were conducted in order to address this issue. The first experience consisted in testing the impact of the land surface initial conditions. We used realistic land surface initial state produced by the operational SIM model for the specific year and 9 random years of Safran atmospheric analyses (temperature and precipitation) from 1971 to 2001, in a consistent way with the previous study (Céron et al, 2010). The other atmospheric parameters (wind, specific humidity, long wave and short wave radiation and cloudiness) come from the SAFRAN climatology over the same period. The second experience was designed to evaluate the impact of the atmospheric forcing with 9 random years, chosen for the land surface initial state. The atmospheric forcing (temperature and precipitation) comes from the Safran analysis system for the corresponding year. Some results of this study will be presented on soil wetness index (SWI) forecasts and river flows forecasts for all stations in France. We will compare deterministic and probabilistic scores of the two experiences with those of the hydrological forecasting suite built with the seasonal forecasts from the DEMETER project. Perspectives for the downscaling of seasonal forecasts will be discussed in a last part. Céron J-P, Tanguy G, Franchistéguy L, Martin E, Regimbeau F and Vidal J-P, 2010. Hydrological

  18. 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.

  19. Vapor layer evolution during drop impact on a heated surface

    Science.gov (United States)

    Lee, Sanghyeon; Lee, Sangjun; Lee, Jisan; Fezzaa, Kamel; Je, Jung Ho

    2015-11-01

    When a liquid drop impacts on a sufficiently hot surface above the boiling point, a vapor layer is formed between the drop and the surface, preventing direct contact between them and as a result levitating the drop, known as the Leidenfrost effect. Understanding the evolution of the vapor layer is largely unexplored despite its importance in estimating heat transfer in cooling systems of thermal or nuclear power plants. The side-profile visualization of the vapor layer, as absolutely required for investigating its evolution, has been however unavailable by conventional optical microscopy. In this study, by employing ultrafast X-ray phase contrast imaging, we directly visualize the profiles of the vapor layers during liquid drop impact on a hot surface and elucidate the evolution of the vapor layers during spreading and retraction of the drop as functions of impact height and surface temperature. We reveal that the evolution is governed by the propagation of capillary waves generated in retraction and the wavelength of capillary waves λ is inversely proportional to the impact height h with a relation ~σ/ρh ~We-1 where We is weber number. Capillary waves that converge at the center of the vapor layers are linked to the bouncing behavior of the drop.

  20. Mechanical and Wear Properties of Nanostructured Surface Layer in Iron Induced by Surface Mechanical Attrition Treatment

    Institute of Scientific and Technical Information of China (English)

    Nairong TAO; Weiping TONG; Zhenbo WANG; Wei WANG; Manling SUI; Jian LU; Ke LU

    2003-01-01

    A porosity-free and contamination-free surface layer with grain sizes ranging from nanometer to micrometer in Fe samples was obtained by surface mechanical attrition treatment (SMAT) technique. Mechanical and wear properties of the surface layer in the SMATed and annealed Fe samples were measured by means of nanoindentation and nanoscratch tests, respectively. Experimental results showed that the hardness of the surface layer in the SMATed Fe sample increased evidently due to the grain refinement. The elastic noduli of the surface layers in the SMATed and annealed Fe samples were unchanged, independent of grain size in the present grain size regime. Compared with the original Fe sample, the wear resistance enhanced and the coefficient of friction decreased in the surface layer of the SMATed Fe sample.

  1. 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

  2. SURFACE HYDROPHOBICITY MODIFICATION OF CELLULOSE FIBERS BY LAYER-BY-LAYER SELF-ASSSEMBLY OF LIGNOSULFONATES

    Directory of Open Access Journals (Sweden)

    Hui Li

    2011-03-01

    Full Text Available Self-assembled multilayers of lignosulfonates (LS were built up on both quartz slides and cellulose fibers using a Cu2+-mediated layer-by-layer (LBL technique. The growth of LS multilayers on quartz slides was monitored by UV-Vis spectroscopy, and the absorbance at 205 nm as well as at 280 nm was found to linearly increase with the number of layers. The formation of LS multilayers on fibers surfaces was characterized by X-ray photoelectron spectroscopy (XPS and atomic force microscopy (AFM. The XPS results showed that the surface contents of the characteristic elements, S and Cu, of LS multilayers were increased with the number of layers, which suggests the deposition of LS-Cu2+ complexes on cellulose fibers. Furthermore, there was a good linear relationship between the calculated surface LS content and the increment of LS layers. The AFM morphology results confirmed that the cellulose microfibrils on fiber surface were gradually covered by LS particles, resulting in the increase of surface roughness as self-assembly proceeded. The hydrophobicity of cellulose fiber probed by dynamic contact angle was significantly increased due to LBL self-assembly of LS on its surface. The initial contact angle was increased from 0° to 115° as the cellulose fibers were modified with a 5-layer LS multilayer. The reduction rate of the contact angle was dependent on the number of layers. When the cellulose fiber was modified by a 5-layer LS multilayer, the contact angle shifted from 115 to 98° after 0.12 s, suggesting some degree of hydrophobic character. Therefore, this technique provides a simple but effective way for promoting hydrophobicity of cellulose fibers in a controllable manner.

  3. The Tturbulent Structure of the Atmospheric Boundary Layer over Small Northern Lakes

    Science.gov (United States)

    Repina, I.; Stepanenko, V.; Artamonov, A.; Barskov, K.; Polukhov, A.

    2015-12-01

    Wetland and freshwater ecosystems of the Northern Europe are an important natural source of atmospheric methane. Adequate calculation of gas emission from the northern territories requires calculation of balances of heat, moisture, and gases at the surface of water bodies on the sub-grid scale in the climate models. We carried out measurements in North Karelia on the lake Verkhneye (White Sea Biological Station of Moscow State University). The purpose of the study is evaluation of turbulent transport in the system "lake water- near-surface air - surrounding forest" in the winter season. We used an array of acoustic anemometers mounted at different distances from the lake shore. Measurements were taken at two heights in the center of the lake. It was revealed that the intensity of the turbulent transfer essentially depends on the height and location of sensors, and the wind direction. Stratification in the near-to-surface air probably does not play significant role. Besides, there is no constant-flux layer. The later makes Monin and Obukhov similarity theory (which is used in most of the parameterizations for calculating turbulent flows) inapplicable in this case. The work was sponsored by RFBR 14-05-91752, 14-05-91764, 15-35-20958.

  4. Simulation of a 5MW wind turbine in an atmospheric boundary layer

    International Nuclear Information System (INIS)

    This article presents detached eddy simulation (DES) results of a 5MW wind turbine in an unsteady atmospheric boundary layer. The evaluation performed in this article focuses on turbine blade loads as well as on the influence of atmospheric turbulence and tower on blade loads. Therefore, the turbulence transport of the atmospheric boundary layer to the turbine position is analyzed. To determine the influence of atmospheric turbulence on wind turbines the blade load spectrum is evaluated and compared to wind turbine simulation results with uniform inflow. Moreover, the influences of different frequency regimes and the tower on the blade loads are discussed. Finally, the normal force coefficient spectrum is analyzed at three different radial positions and the influence of tower and atmospheric turbulence is shown

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

    Science.gov (United States)

    Kang, D.

    2015-12-01

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

  6. Changes of surface layer of nitrogen-implanted AISI316L stainless steel

    International Nuclear Information System (INIS)

    The effects of nitrogen ion implantation into AISI316L stainless steel on friction, wear, and microhardness have been investigated at an energy level of 125 keV at a fluence of 1·1017 - 1·1018 N/cm2. The composition of the surface layer was investigated by RBS, XRD (GXRD), SEM and EDX. The friction coefficient and abrasive wear rate of the stainless steel were measured in the atmospheres of air, oxygen, argon, and in vacuum. As follows from the investigations, there is an increase in resistance to frictional wear in the studied samples after implantation; however, these changes are of different characters in various atmospheres. The largest decrease in wear was observed during tests in the air, and the largest reduction in the value of the friction coefficient for all implanted samples was obtained during tests in the argon atmosphere. Tribological tests revealed larger contents of nitrogen, carbon, and oxygen in the products of surface layer wear than in the surface layer itself of the sample directly after implantation

  7. Atomic and molecular layer deposition for surface modification

    International Nuclear Information System (INIS)

    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 Al2O3 due to e.g. complex formation. • Same effect on cellulosic fabrics observed with low temperature deposited TiO2. • Different film growth and oxidation potential with different precursors. • Hybrid layer on inorganic layer can be used to improve adhesion of polymer melt

  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. Multi-layer surface profiling using gated wavefront sensing

    Science.gov (United States)

    Wang, Xin; Nordin, Nur Dalilla; Tik, Eddy Chow Mun; Tan, ChingSeong; Chew, Kuew Wai; Menoni, Carmen

    2015-01-01

    Recently, multi-layer surface profiling and inspection has been considered an emerging topic that can be used to solve various manufacturing inspection problems, such as graded index lenses, TSV (Thru-Silicon Via), and optical coating. In our study, we proposed a gated wavefront sensing approach to estimate the multi-layer surface profile. In this paper, we set up an experimental platform to validate our theoretical models and methods. Our test bed consists of pulse laser, collimator, prism, well-defined focusing lens, testing specimen, and gated wavefront sensing assembly (e.g., lenslet and gated camera). Typical wavefront measurement steps are carried out for the gated system, except the reflectance is timed against its time of flight as well as its intensity profile. By synchronizing the laser pulses to the camera gate time, it is possible to discriminate a multi-layer wavefront from its neighbouring discrete layer reflections.

  10. 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 Gaussian plume model concept with the spread parameters described in terms of the Pasquill stability classification or Monin-Obukhov similarity relationships are used. Other model types are Lagrangian particle models which also are parameterized in terms of Monin-Obukhov similarity relationships....... The applied models describe adequately the dispersion process in a weakly stable atmosphere, but fail during very stable atmospheric conditions. This suggests that Monin-Obukhov similarity theory is an adequate tool for the parameterization of the input parameters to atmospheric dispersion models...... during weakly stable conditions, but that more detailed parameterisations including other physical processes than those covered by the Monin-Obukhov theory should be developed for the very stable atmosphere....

  11. 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

  12. METHODS TO DETECT ATMOSPHERIC AND SURFACE HEAT ISLANDS IN URBAN AREAS

    Directory of Open Access Journals (Sweden)

    I. HERBEL

    2015-10-01

    Full Text Available Intensification of the urbanization process and its associated climatic effects is nowadays a major problem of large cities worldwide. One of these climatic effects is the urban heat island (UHI, that implies increased air and surface temperature values in the city when compared to the nearby rural areas. This phenomenon threatens the health of the population, especially during heat waves, affects the quality of the environment and the quality of life, and also generates significant costs to ensure the inhabitants' thermal comfort. In this study we present a review of the UHI concept and three of the main methods used to detect the atmospheric and surface urban heat islands. Satellite image data analysis seems an easier and time-saving solution, but due to its limitations, we consider that a combination of both surfaces and lower atmospheric layer temperature data analysis is the best choice in order to get accurate results of the intensity and spatial extension of the UHI.

  13. The NOx dependence of bromine chemistry in the Arctic atmospheric boundary layer

    Science.gov (United States)

    Custard, K. D.; Thompson, C. R.; Pratt, K. A.; Shepson, P. B.; Liao, J.; Huey, L. G.; Orlando, J. J.; Weinheimer, A. J.; Apel, E.; Hall, S. R.; Flocke, F.; Mauldin, L.; Hornbrook, R. S.; Pöhler, D.; S., General; Zielcke, J.; Simpson, W. R.; Platt, U.; Fried, A.; Weibring, P.; Sive, B. C.; Ullmann, K.; Cantrell, C.; Knapp, D. J.; Montzka, D. D.

    2015-09-01

    Arctic boundary layer nitrogen oxides (NOx = NO2 + NO) are naturally produced in and released from the sunlit snowpack and range between 10 to 100 pptv in the remote background surface layer air. These nitrogen oxides have significant effects on the partitioning and cycling of reactive radicals such as halogens and HOx (OH + HO2). However, little is known about the impacts of local anthropogenic NOx emission sources on gas-phase halogen chemistry in the Arctic, and this is important because these emissions can induce large variability in ambient NOx and thus local chemistry. In this study, a zero-dimensional photochemical kinetics model was used to investigate the influence of NOx on the unique springtime halogen and HOx chemistry in the Arctic. Trace gas measurements obtained during the 2009 OASIS (Ocean - Atmosphere - Sea Ice - Snowpack) field campaign at Barrow, AK were used to constrain many model inputs. We find that elevated NOx significantly impedes gas-phase halogen radical-based depletion of ozone, through the production of a variety of reservoir species, including HNO3, HO2NO2, peroxyacetyl nitrate (PAN), BrNO2, ClNO2 and reductions in BrO and HOBr. The effective removal of BrO by anthropogenic NOx was directly observed from measurements conducted near Prudhoe Bay, AK during the 2012 Bromine, Ozone, and Mercury Experiment (BROMEX). Thus, while changes in snow-covered sea ice attributable to climate change may alter the availability of molecular halogens for ozone and Hg depletion, predicting the impact of climate change on polar atmospheric chemistry is complex and must take into account the simultaneous impact of changes in the distribution and intensity of anthropogenic combustion sources. This is especially true for the Arctic, where NOx emissions are expected to increase because of increasing oil and gas extraction and shipping activities.

  14. A Study On Atmospheric Boundary-Layer Characteristics At Anand, India Using Lsp Experimental Data Sets

    Science.gov (United States)

    Satyanarayana, A. N. V.; Lykossov, V. N.; Mohanty, U. C.

    An attempt is made to study the planetary boundary layer (PBL) characteristics during the winter period at Anand (22.4°N, 72.6°E), a semi-arid region, which is located in the western part of India. A one-dimensional turbulent kinetic energy (TKE) closure model is used for the study. The structure of the PBL,which consists of profiles of zonal and meridional components of wind,potential temperature and specific humidity, is simulated. A one-dimensional soil heat and moisture transport parameterization scheme is incorporated for the accurate representation of the energy exchange processes at the soil-atmosphere interface. The diurnal variation of fluxes of sensible heat, latent heat, shortwave radiation, net radiation and soil flux, soil temperature at different depths, Richardson number and TKE at the height of the constant flux layer is studied. The model predictions are compared with the available observations obtained from a special Land Surface Processes (LSP) experiment.

  15. 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.

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

    International Nuclear Information System (INIS)

    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

  17. 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

  18. Surface waves versus negative refractive index in layered superconductors

    OpenAIRE

    Golick, V. A.; Kadygrob, D. V.; Yampol'skii, V. A.; Rakhmanov, A. L.; Ivanov, B. A.; Nori, Franco

    2010-01-01

    We predict a new branch of surface Josephson plasma waves (SJPWs) in layered superconductors for frequencies higher than the Josephson plasma frequency. In this frequency range, the permittivity tensor components along and transverse to the layers have different signs, which is usually associated with negative refraction. However, for these frequencies, the bulk Josephson plasma waves cannot be matched with the incident and reflected waves in the vacuum, and, instead of the negative-refractiv...

  19. 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

  20. Surface stress of graphene layers supported on soft substrate

    Science.gov (United States)

    Du, Feng; Huang, Jianyong; Duan, Huiling; Xiong, Chunyang; Wang, Jianxiang

    2016-05-01

    We obtain the surface stress of a single layer and multilayers of graphene supported on silicone substrates by measuring the deformation of the graphene-covered substrates induced by the surface tension of liquid droplets together with the Neumann’s triangle concept. We find that the surface stress of the graphene-covered substrate is significant larger than that of the bare substrate, and it increases with increasing graphene layers, and finally reaches a constant value of about 120 mN/m on three and more layers of graphene. This work demonstrates that the apparent surface stress of graphene-substrate systems can be tuned by the substrate and the graphene layers. The surface stress and the tuning effect of the substrate on it may have applications in design and characterization of graphene-based ultra-sensitive sensors and other devices. Moreover, the method may also be used to measure the surface stress of other ultrathin films supported on soft substrates.

  1. Surface stress of graphene layers supported on soft substrate

    Science.gov (United States)

    Du, Feng; Huang, Jianyong; Duan, Huiling; Xiong, Chunyang; Wang, Jianxiang

    2016-01-01

    We obtain the surface stress of a single layer and multilayers of graphene supported on silicone substrates by measuring the deformation of the graphene-covered substrates induced by the surface tension of liquid droplets together with the Neumann’s triangle concept. We find that the surface stress of the graphene-covered substrate is significant larger than that of the bare substrate, and it increases with increasing graphene layers, and finally reaches a constant value of about 120 mN/m on three and more layers of graphene. This work demonstrates that the apparent surface stress of graphene-substrate systems can be tuned by the substrate and the graphene layers. The surface stress and the tuning effect of the substrate on it may have applications in design and characterization of graphene-based ultra-sensitive sensors and other devices. Moreover, the method may also be used to measure the surface stress of other ultrathin films supported on soft substrates. PMID:27166087

  2. Surface stress of graphene layers supported on soft substrate.

    Science.gov (United States)

    Du, Feng; Huang, Jianyong; Duan, Huiling; Xiong, Chunyang; Wang, Jianxiang

    2016-01-01

    We obtain the surface stress of a single layer and multilayers of graphene supported on silicone substrates by measuring the deformation of the graphene-covered substrates induced by the surface tension of liquid droplets together with the Neumann's triangle concept. We find that the surface stress of the graphene-covered substrate is significant larger than that of the bare substrate, and it increases with increasing graphene layers, and finally reaches a constant value of about 120 mN/m on three and more layers of graphene. This work demonstrates that the apparent surface stress of graphene-substrate systems can be tuned by the substrate and the graphene layers. The surface stress and the tuning effect of the substrate on it may have applications in design and characterization of graphene-based ultra-sensitive sensors and other devices. Moreover, the method may also be used to measure the surface stress of other ultrathin films supported on soft substrates. PMID:27166087

  3. 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.

  4. Surface Force and Friction : effects of adsorbed layers and surface topography

    OpenAIRE

    Liu, Xiaoyan

    2014-01-01

    Interfacial features of polymers are a complex, fascinating topic, and industrially very important. There is clearly a need to understand interactions between polymer layers as they can be used for controlling surface properties, colloidal stability and lubrication. The aim of my Ph.D study was to investigate fundamental phenomena of polymers at interfaces, covering adsorption, interactions between polymer layers and surfactants, surface forces and friction between adsorbed layers. A branched...

  5. Ice Layers as an Indicator of Summer Warmth and Atmospheric Blocking in Alaska

    Science.gov (United States)

    Kelsey, E. P.; Wake, C. P.; Kreutz, K. J.; Osterberg, E. C.

    2009-12-01

    A new snowpit and shallow firn core was extracted from near Kahiltna Pass (2970 m) in Denali National Park, Alaska in May 2008. The 23.12 m-long record spans autumn 2003 to spring 2008 with an average annual accumulation rate of 2.43 m water equivalent. Density, accumulation rate and δD time series are presented (Fig. 1) and compared with meteorological observations. Clusters of ice layers reveal the occurrence of occasional above freezing temperatures during the summertime. The annual cumulative number of degrees above freezing at the closest grid point in the NCEP Reanalysis dataset (62.5°W 150.0°W 700 hPa) correlates amazingly well with annual ice layer thickness (r=0.99), and astoundingly high correlation coefficients (0.94-1.00) between annual ice layer thickness and regional station temperatures indicate ice layer thickness can be used as a proxy for mean and extreme summertime temperatures across interior Alaska. Three melting events lasted two weeks or longer and were associated with a “Rex block” (aka “high-over-low block”) pattern and downstream trough over Hudson Bay as seen with 500 hPa geopotential heights. Most shorter melting events were associated with a cut-off low traversing the Gulf of Alaska. The extraction of a surface-to-bedrock core from this location should be able to provide a high quality record of summer temperature and atmospheric blocking variability for the last several hundred years. Figure 1. Kahiltna Pass firn core density (top curve), high resolution δD (high-res bottom curve), and smoothed δD (smooth curve), peak summer markers (black diamonds), peak winter markers (black squares), and significant δD events (open black circles) with a time scale as the abscissa. The arrows indicate the thickest ice layer (0.13 m) in the record and its associated spike in δD. The relative thickness of the density layers does not correspond to their relative physical thickness because of linear interpolation between reference horizons

  6. Atmospheric pressure plasma surface modification of carbon fibres

    DEFF Research Database (Denmark)

    Kusano, Yukihiro; Løgstrup Andersen, Tom; Michelsen, Poul

    2008-01-01

    Carbon fibres are continuously treated with dielectric barrier discharge plasma at atmospheric pressure in various gas conditions for adhesion improvement in mind. An x-ray photoelectron spectroscopic analysis indicated that oxygen is effectively introduced onto the carbon fibre surfaces by He, He...... temperature for a month the O/C ratio at the plasma treated surfaces decreased to 0.151, which is close to that of the untreated ones. It can be attributed to the adsorption of hydrocarbon contamination at the plasma treated surfaces....

  7. Evidence of the surface layer in tungstated zirconia

    Science.gov (United States)

    Torres-García, E.; Rosas, G.; Ascencio, J. A.; Haro-Poniatowski, E.; Pérez, R.

    We characterized the structure of tungstated zirconia (WOx-ZrO2) by combining X-ray diffraction, Raman spectroscopy and High Resolution Electron Microscopy (HREM) together with molecular simulations. Our results indicate that the structure of this material consists of metastable tetragonal ZrO2 nanoparticles (WOx). Although the X-ray diffraction pattern matched the spectra of the tetragonal ZrO2 bulk phase the lattice fringes of the ZrO2 nanoparticles observed by HREM were locally distorted, presumably as a result of the interaction with the surface WOx layer. The local interplanar distances of the surface layer were close to those present in different bulk tungsten oxocompounds, and its variability was also an indication of the WOx-ZrO2 interaction. Molecular simulations corroborated our structural assignment. The results presented here are a direct evidence for the presence of a surface WOx layer in the case of WOx-ZrO2.

  8. Large-eddy simulation of the atmospheric boundary layer: Influence of unsteady forcing, baroclinicity, inversion strength and stability on the wind profile

    DEFF Research Database (Denmark)

    Pedersen, Jesper Grønnegaard

    The largest wind turbines today often reach heights where traditional models of the wind speed and how it varies with height no longer can be expected to apply. For accurate assessment of wind energy resources and loads on wind turbines, there is a need for better understanding of the flow of air...... above the atmospheric surface layer. Continuous and detailed measurements of mean winds and turbulence above the surface layer are expensive and difficult to obtain. Computational fluid dynamics modelling of the atmospheric flow can be an attractive alternative or supplement to field experiments. In...

  9. 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.

  10. Adhesive Stretchable Printed Conductive Thin Film Patterns on PDMS Surface with an Atmospheric Plasma Treatment.

    Science.gov (United States)

    Li, Chun-Yi; Liao, Ying-Chih

    2016-05-11

    In this study, a plasma surface modification with printing process was developed to fabricate printed flexible conductor patterns or devices directly on polydimethylsiloxane (PDMS) surface. An atmospheric plasma treatment was first used to oxidize the PDMS surface and create a hydrophilic silica surface layer, which was confirmed with photoelectron spectra. The plasma operating parameters, such as gas types and plasma powers, were optimized to obtain surface silica layers with the longest lifetime. Conductive paste with epoxy resin was screen-printed on the plasma-treated PDMS surface to fabricate flexible conductive tracks. As a result of the strong binding forces between epoxy resin and the silica surface layer, the printed patterns showed great adhesion on PDMS and were undamaged after several stringent adhesion tests. The printed conductive tracks showed strong mechanical stability and exhibited great electric conductivity under bending, twisting, and stretching conditions. Finally, a printed pressure sensor with good sensitivity and a fast response time was fabricated to demonstrate the capability of this method for the realization of printed electronic devices. PMID:27082455

  11. Surface modification of Ti-surfaces by alginate polyelectrolyte layers

    Czech Academy of Sciences Publication Activity Database

    Kubies, Dana; Pop-Georgievski, Ognen; Mázl Chánová, Eliška; Zemek, Josef; Neykova, Neda; Demianchuk, Roman; Houska, Milan; Filová, Elena; Bačáková, Lucie; Rypáček, František

    Liverpool : European Society for Biomaterials, 2014. P314. [Annual Conference European Society for Biomaterials /26./. 31.08.2014-03.09.2014, Liverpool] R&D Projects: GA MZd(CZ) NT13297; GA MŠk(CZ) EE2.3.30.0029; GA MŠk(CZ) ED1.1.00/02.0109 Institutional support: RVO:61389013 ; RVO:68378271 ; RVO:67985823 Keywords : surface modification * titanium * alginate Subject RIV: CD - Macromolecular Chemistry; BM - Solid Matter Physics ; Magnetism (FZU-D); EI - Biotechnology ; Bionics (FGU-C)

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

    Directory of Open Access Journals (Sweden)

    Ziemath Ervino Carlos

    1998-01-01

    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.

  13. Surface tension in plasmas related to double layer formation

    International Nuclear Information System (INIS)

    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)

  14. Surface layer ozone and nitric oxides in the Arctic: The inuence of boundary layer dynamics, snowpack chemistry, surface exchanges, and seasonality

    Science.gov (United States)

    Van Dam, Brie A.

    The snowpack is a region of active chemistry. Aqueous chemistry in a quasi-liquid layer on snow grains and gas-phase chemical reactions in snow interstitial air can lead to the production or destruction of important trace gases. Physical transport parameters such as wind pumping and diffusion affect the vertical distribution of gases within the snowpack. The resulting emission or uptake of trace gases at the atmosphere-snowpack interface can have significant in uence on the chemistry of the lower atmosphere. In this work the dynamic interactions between the snowpack and atmosphere are examined from multiple perspectives. The primary focus is on ozone (O3) and nitrogen oxides (NOx) in the Arctic, a region undergoing widespread environmental change. To investigate an ice-sheet location with year round snow cover, data from a two-year campaign at Summit, Greenland are implemented. At Summit this study examines (1) the processes contributing to vigorous chemistry in snow interstitial air, and (2) the role of the boundary layer over snow in determining surface layer NOx. Physical and chemical processes are shown to contribute to distinct seasonal and diurnal cycles of O3, NO, and NO2 in the snowpack. Boundary layer depths estimated from sonic anemometer turbulence quantities are used alongside sodar-derived values to show that the depth of the stable to weakly stable boundary layer at Summit was not a primary factor in determining NO x in early summer. Motivated by observations of an increase in the length of the snow-free season in the Arctic in recent decades, data from a one-year experiment at the seasonally-snow covered location of Toolik Lake, AK are also incorporated. This study shows the first observations of springtime ozone depletion events at a location over 200 km from the coast in the Arctic. FLEXPART analysis is used to illustrate that these inland events are linked to transport conditions. Lastly at this location, eddy-covariance O3 uxes were calculated to

  15. Evolution of the lower planetary boundary layer over strongly contrasting surfaces

    International Nuclear Information System (INIS)

    In a multilaboratory field study held near Boardman in northeastern Oregon in June 1991, various properties of the surface and lower atmospheric boundary layer over heavily irrigated cropland and adjacent desert steppe were investigated in the initial campaign of the Atmospheric Radiation Measurement (ARM) program. The locale was selected because its disparate characteristics over various spatial scales stress the ability of general circulation models (GCMS) to describe lower boundary conditions, particularly across the discontinuity between desert (in which turbulent flux of heat must be primarily as sensible heat) and large irrigated tracts (in which turbulent flux of latent heat should be the larger term). This campaign of ARM seeks to increase knowledge in three critical areas: (1) determination of the relationships between surface heat fluxes measured over multiple scales and the controlling surface parameters within each scale, (2) integration of local and nearly local heat flux estimates to produce estimates appropriate for GCM grid cells of 100-200 km horizontal dimension, and (3) characterization of the growth and development of the atmospheric boundary layer near transitions between surfaces with strongly contrasting moisture availabilities

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

    Science.gov (United States)

    Arrieta, Jesús M; Duarte, Carlos M; Sala, M Montserrat; Dachs, Jordi

    2015-01-01

    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. PMID:26834717

  17. Out of thin air: Microbial utilization of atmospheric gaseous organics in the surface ocean

    Directory of Open Access Journals (Sweden)

    Jesus M Arrieta

    2016-01-01

    Full Text Available 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 to 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 subsidising 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.

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

    Science.gov (United States)

    Arrieta, Jesús M.; Duarte, Carlos M.; Sala, M. Montserrat; Dachs, Jordi

    2016-01-01

    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. PMID:26834717

  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. Surface morphological evolution of epitaxial CrN(001) layers

    International Nuclear Information System (INIS)

    CrN layers, 57 and 230 nm thick, were grown on MgO(001) at Ts=600-800 deg. C by ultrahigh-vacuum magnetron sputter deposition in pure N2 discharges from an oblique deposition angle α=80 deg. . Layers grown at 600 deg. C nucleate as single crystals with a cube-on-cube epitaxial relationship with the substrate. However, rough surfaces with cauliflower-type morphologies cause the nucleation of misoriented CrN grains that develop into cone-shaped grains that protrude out of the epitaxial matrix to form triangular faceted surface mounds. The surface morphology of epitaxial CrN(001) grown at 700 deg. C is characterized by dendritic ridge patterns extending along the orthogonal directions superposed by square-shaped super mounds with edges. The ridge patterns are attributed to a Bales-Zangwill instability while the supermounds form due to atomic shadowing which leads to the formation of epitaxial inverted pyramids that are separated from the surrounding layer by tilted nanovoids. Growth at 800 deg. C yields complete single crystals with smooth surfaces. The root-mean-square surface roughness for 230-nm-thick layers decreases from 18.8 to 9.3 to 1.1 nm as Ts is raised from 600 to 700 to 800 deg. C. This steep decrease is due to a transition in the roughening mechanism from atomic shadowing to kinetic roughening. Atomic shadowing is dominant at 600 and 700 deg. C, where misoriented grains and supermounds, respectively, capture a larger fraction of the oblique deposition flux in comparison to the surrounding epitaxial matrix, resulting in a high roughening rate that is described by a power law with an exponent β>0.5. In contrast, kinetic roughening controls the surface morphology for Ts=800 deg. C, as well as the epitaxial fraction of the layers grown at 600 and 700 deg. C, yielding relatively smooth surfaces and β≤0.27

  1. Non-thermal atmospheric pressure discharges for surface modification

    International Nuclear Information System (INIS)

    Throughout the last decades, plasma technology has been established in a series of surface treatment applications, e.g. for semiconductor processing or optical coatings. The majority of plasma assisted technologies is based on low pressure processes. In recent years, however, non-thermal atmospheric pressure discharges have attracted considerable interest because of their simplified technical devices for industrial applications as compared to low pressure processes which require vacuum equipment. Hence, batch processing can be avoided, thus facilitating the implementation of plasma process steps into production lines. Investment costs are cut down significantly. The use of atmospheric pressure plasmas for technical applications dates back to the ozone production with dielectric barrier discharges (DBD) by Siemens in 1857. Lately, the application of atmospheric pressure plasmas for surface treatment has been reported, e.g. for the treatment of foils to improve printability, for surface cleaning and protective coatings. The DBD is known as a strongly inhomogeneous, filamentary discharge. A non filamentary, homogeneous DBD was observed in He, N2, other gases, and mixtures. An example of this discharge type and its application for the deposition of thin films by plasma polymerization is discussed in more detail. The standard planar electrode geometry of the DBD is characterized by a narrow inter-electrode gap in the mm-Region. Hence, surface treatment has been restricted to thin, flat substrates. Attempts to overcome these limitations involve micro discharge arrays and jet geometries, which are evoked by an enhanced gas flow, partly in combination with the electric field. Jets are created out of several plasma types, among them corona discharge, DBD, microwave discharge and RF discharge. With these plasma sources, substrate geometries displaying 3-dimensional features can be treated, too. Critical parameters for the comparison of atmospheric pressure surface

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

    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 atmospheric properties, and heat fluxes....

  3. 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

  4. The structure of alteration layers on cast glass surfaces

    International Nuclear Information System (INIS)

    Alteration layers developed on SRL-165 simulated waste glasses in dilute sodium silicate/bicarbonate leaching solutions have been examined by Secondary Ionization Mass Spectroscopy (SIMS) using fine-scale, multiple-element depth profiling. Selected samples were examined with an imaging detector system, which demonstrated the horizontal homogeneity of the layer development at all depths within the layer. After 1 day of reaction at 90 degrees C the reaction layer shows depletion of glass elements to a depth of 0.2 μm. The surface of the layer in contact with the solution shows enrichment of Si, Al, and alkali elements even at this short reaction time, suggesting the early stages of development of secondary aluminosilicate phases. With increased reaction time, the layer thickens to about 1.3 μm at 91 days, while the evidence for aluminosilicate development at the surface of the layer becomes more prominent. Penetration of hydrogen into the ''unreacted'' glass proceeds to a depth of about 0.5 μm deeper than the alkali depletion zone. This suggests the mechanism of initial reaction of the glass is by attack of the silicate structure by molecular water or hydroxide ion rather than by alkali-hydrogen ion exchange. The simple structure of the layers developed in the silicate solution is in contrast to the complexity of layer structure found when glasses are reacted in deionized water. Since the conditions for geologic disposal will be closer to those used in the silicate leaching experiments, these results hold promise for the ability to model the system to predict long-term performance after disposal in a repository

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

    CERN Document Server

    Spiga, Aymeric; Madeleine, Jean-Baptiste; Määttänen, Anni; Forget, François

    2012-01-01

    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 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, 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 on board Mars Global Surveyor and Mars Reconnaissance Orbite...

  6. SURFACE HYDROPHOBICITY MODIFICATION OF CELLULOSE FIBERS BY LAYER-BY-LAYER SELF-ASSSEMBLY OF LIGNOSULFONATES

    OpenAIRE

    Hui Li; Hao Liu; Shiyu Fu; Huaiyu Zhan

    2011-01-01

    Self-assembled multilayers of lignosulfonates (LS) were built up on both quartz slides and cellulose fibers using a Cu2+-mediated layer-by-layer (LBL) technique. The growth of LS multilayers on quartz slides was monitored by UV-Vis spectroscopy, and the absorbance at 205 nm as well as at 280 nm was found to linearly increase with the number of layers. The formation of LS multilayers on fibers surfaces was characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM...

  7. The influence of the atmospheric boundary layer on nocturnal layers of noctuids and other moths migrating over southern Britain

    OpenAIRE

    Wood, Curtis Ron; Chapman, Jason W.; Reynolds, Donald R.; Barlow, Janet Fraser; Alan D. Smith; Woiwod, Ian P.

    2006-01-01

    Insects migrating at high altitude over southern Britain have been continuously monitored by automatically-operating, vertical-looking radars over a period of several years. During some occasions in the summer months, the migrants were observed to form well-defined layer concentrations, typically at heights of 200-400 m, in the stable night-time atmosphere. Under these conditions, insects are likely to have control over their vertical movements and are selecting flight heights which are favou...

  8. Continuous atmospheric boundary layer observations in the coastal urban area of Barcelona during SAPUSS

    Directory of Open Access Journals (Sweden)

    M. Pandolfi

    2013-05-01

    Full Text Available Continuous measurements of surface mixed layer (SML, decoupled residual/convective layer (DRCL and aerosol backscatter coefficient were performed within the Barcelona (Spain boundary layer from September to October 2010 (30 days in the framework of the SAPUSS (Solving Aerosol Problems by Using Synergistic Strategies field campaign. Two near-infrared ceilometers (Jenoptik CHM15K, vertically and horizontally probing (only vertical profiles are herein discussed, were deployed. Ceilometer-based DRCLs (1761 ± 363 m a.g.l. averaged over the campaign duration were twice as high as the mean SML (904 ± 273 m a.g.l.. Both DRCL and SML showed a marked SML diurnal cycle. Ceilometer data were compared with potential temperature profiles measured by daily radiosounding (twice a day, midnight and midday to interpret the boundary layer structure in the coastal urban area of Barcelona. The overall agreement (R2 = 0.80 between the ceilometer-retrieved and radiosounding-based SML heights (h revealed overestimation of the SML by the ceilometer (Δh=145 ± 145 m. After separating the data in accordance with different atmospheric scenarios, the lowest SML (736 ± 183 m and DRCL (1573 ± 428 m were recorded during warm North African (NAF advected air mass. By contrast, higher SML and DRCL were observed during stagnant Regional (REG (911 ± 234 m and 1769 ± 314 m, respectively and cold Atlantic (ATL (965 ± 222 m and 1878 ± 290 m, respectively air masses. In addition to being the lowest, the SML during the NAF scenario frequently showed a flat upper boundary throughout the day possibly because of the strong winds from the Mediterranean Sea limiting the midday SML convective growth. The mean backscatter coefficients were calculated at two selected heights representative of middle and top SML portions, i.e. β500 = 0.59 ± 0.45 Mm−1 sr−1 and β800 = 0.87 ± 0.68 Mm−1 sr−1 at 500 m and 800 m a.g.l., respectively. The highest backscatter coefficients were

  9. Particle concentration and flux dynamics in the atmospheric boundary layer as the indicator of formation mechanism

    Directory of Open Access Journals (Sweden)

    J. Lauros

    2010-08-01

    Full Text Available We carried out column model simulations to study particle fluxes and deposition and to evaluate different particle formation mechanisms at a boreal forest site in Finland. We show that kinetic nucleation of sulphuric acid cannot be responsible for new particle formation alone as the vertical profile of particle number distribution does not correspond to observations. Instead organic induced nucleation leads to good agreement confirming the relevance of the aerosol formation mechanism including organic compounds emitted by biosphere.

    Simulation of aerosol concentration inside the atmospheric boundary layer during nucleation days shows highly dynamical picture, where particle formation is coupled with chemistry and turbulent transport. We have demonstrated suitability of our turbulent mixing scheme in reproducing most important characteristics of particle dynamics inside the atmospheric boundary layer. Deposition and particle flux simulations show that deposition affects noticeably only the smallest particles at the lowest part of the atmospheric boundary layer.

  10. Surfactant-associated bacteria in the near-surface layer of the ocean.

    Science.gov (United States)

    Kurata, Naoko; Vella, Kate; Hamilton, Bryan; Shivji, Mahmood; Soloviev, Alexander; Matt, Silvia; Tartar, Aurélien; Perrie, William

    2016-01-01

    Certain marine bacteria found in the near-surface layer of the ocean are expected to play important roles in the production and decay of surface active materials; however, the details of these processes are still unclear. Here we provide evidence supporting connection between the presence of surfactant-associated bacteria in the near-surface layer of the ocean, slicks on the sea surface, and a distinctive feature in the synthetic aperture radar (SAR) imagery of the sea surface. From DNA analyses of the in situ samples using pyrosequencing technology, we found the highest abundance of surfactant-associated bacterial taxa in the near-surface layer below the slick. Our study suggests that production of surfactants by marine bacteria takes place in the organic-rich areas of the water column. Produced surfactants can then be transported to the sea surface and form slicks when certain physical conditions are met. This finding has potential applications in monitoring organic materials in the water column using remote sensing techniques. Identifying a connection between marine bacteria and production of natural surfactants may provide a better understanding of the global picture of biophysical processes at the boundary between the ocean and atmosphere, air-sea exchange of greenhouse gases, and production of climate-active marine aerosols. PMID:26753514

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

    OpenAIRE

    C. Messager; Swart, S

    2016-01-01

    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 atm...

  12. 3D Water Vapor Field in the Atmospheric Boundary Layer Observed with Scanning Differential Absorption Lidar

    OpenAIRE

    Späth, F.; A. Behrendt; Muppa, S. K.; S. Metzendorf; A. Riede; V. Wulfmeyer

    2016-01-01

    The scanning differential absorption lidar (DIAL) of the University of Hohenheim (UHOH) determines fields of the atmospheric water vapor number density with a temporal resolution of a few seconds and spatial resolution of up to a few tens of meters. We present three case studies which show that this high resolution combined with 2- and 3-dimensional scans allows for new insights in the 3-dimensional structure of the water vapor field in the atmospheric boundary layer (ABL). In spring 2013, th...

  13. Design improvement of three-surface-multi-layered channel by reinforcing inner metal layer

    International Nuclear Information System (INIS)

    The three-surface-multi-layered channel has been proposed to reduce magnetohydrodynamic (MHD) pressure drop in a liquid lithium blanket for a future fusion reactor. The channel has three inner side coated with an insulating layer other than the first wall side. Furthermore, a thin vanadium alloy layer is placed on the insulating layer. Our previous study showed that the thin metal layer having a thickness less than 0.02 mm, which is too small to insure its structural integrity, is needed for the reduction of MHD pressure drop. In this study, therefore, we propose a new design for the channel, in which the thin vanadium alloy layer is partially reinforced by attaching reinforcing structure such as wires or columns on the insulating-layer side. As a first step, we conduct a three-dimensional MHD flow analysis by taking interval and length of the reinforcing structure as parameters. The results show that MHD pressure drop induced by the reinforcing structures does not show simple correlation with averaged electric conductance of thin metal layer with the reinforcing structures. Furthermore, a high velocity region appears in region of the first wall's side by changing the length of reinforcing structures. (author)

  14. The importance of a surface organic layer in simulating permafrost thermal and carbon dynamics

    Science.gov (United States)

    Jafarov, Elchin; Schaefer, Kevin

    2016-03-01

    Permafrost-affected soils contain twice as much carbon as currently exists in the atmosphere. Studies show that warming of the perennially frozen ground could initiate significant release of the frozen soil carbon into the atmosphere. Initializing the frozen permafrost carbon with the observed soil carbon distribution from the Northern Circumpolar Soil Carbon Database reduces the uncertainty associated with the modeling of the permafrost carbon feedback. To improve permafrost thermal and carbon dynamics we implemented a dynamic surface organic layer with vertical carbon redistribution, and introduced dynamic root growth controlled by active layer thickness, which improved soil carbon exchange between frozen and thawed pools. These changes increased the initial amount of simulated frozen carbon from 313 to 560 Gt C, consistent with observed frozen carbon stocks, and increased the spatial correlation of the simulated and observed distribution of frozen carbon from 0.12 to 0.63.

  15. Investigations of surface layers by wide-angle Rutherford scattering

    International Nuclear Information System (INIS)

    The energy spectrum of elastically scattered light ions of some MeV gives important informations on surface layers: 1. The energy of the scattered ions depends on the weight of the scattering centre and the depth where scattering takes place. The composition of surface layers of 1-3 μm in thickness can be examined. 2. In case of a mono-crystal target channel effect can arise which results in a decrease of the scattering yield by one or two orders of magnitude. This can be used for investigating the lattice localisation of the additive. Two examples demonstrate the method: the analysis of a magnetic thin-layer (Gd-Co) and the study of the mechanism of diffusion of additions (Sb) used in semi-conductor technic. (V.N.)

  16. Effects of initiating anaerobic digestion of layer-hen poultry dung at sub-atmospheric pressure

    OpenAIRE

    Chima C. Ngumah; Jude N. Ogbulie; Justina C. Orji; Ekperechi S. Amadi

    2013-01-01

    This study investigated the effects of initiating anaerobic digestion (AD) of dry layer-hen poultry dung at the sub-atmospheric pressure of -30 cmHg on biodegradation, biogasification, and biomethanation. The setup was performed as a batch process at an average ambient temperature of 29±2 0C and a retention time of 15 days. Comparisons were made with two other experiments which were both begun at ambient atmospheric pressure; one was inoculated with digestate from a previous layer-hen dung AD...

  17. Quantized layer growth at liquid-crystal surfaces

    DEFF Research Database (Denmark)

    Ocko, B. M.; Braslau, A.; Pershan, P. S.;

    1986-01-01

    specular reflectivity is consistent with a sinusoidal density modulation, starting at the surface and terminating abruptly, after an integral number of bilayers. As the transition is approached the number of layers increases in quantized steps from zero to five before the bulk undergoes a first...

  18. Analysis of the surface layer of the brake disk

    Czech Academy of Sciences Publication Activity Database

    Švábenská, Eva; Roupcová, Pavla; Podstranská, Ivana; Petr, M.; Filip, J.; Schneeweiss, Oldřich

    Ostrava : TANGER Ltd, 2015. ISBN 978-80-87294-58-1. [METAL 2015. International Conference on Metallurgy and Materials /24./. Brno (CZ), 03.06.2015-05.06.2015] R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068 Institutional support: RVO:68081723 Keywords : grey cast iron * brake disk * microstructure analysis * surface layer Subject RIV: JG - Metallurgy

  19. Surface/atmosphere exchange of ammonia over grazed pasture.

    OpenAIRE

    Plantaz, M.A.H.G.

    1998-01-01

    This thesis deals with the exchange of ammonia between the atmosphere and grazed pasture in an area of intensive livestock breeding. The term exchange is used because gaseous ammonia can be taken up (dry deposition) as well as released (emission) by this type of surface.Ammonia exchange fluxes over the grass pasture of a research farm for dairy cattle breeding at Zegveld (the Netherlands) were measured continuously from July 1992 until July 1994. The main objective was to investigate the long...

  20. High Vertically Resolved Atmospheric and Surface/Cloud Parameters Retrieved with Infrared Atmospheric Sounding Interferometer (IASI)

    Science.gov (United States)

    Zhou, Daniel K.; Liu, Xu; Larar, Allen M.; Smith, WIlliam L.; Taylor, Jonathan P.; Schluessel, Peter; Strow, L. Larrabee; Mango, Stephen A.

    2008-01-01

    The Joint Airborne IASI Validation Experiment (JAIVEx) was conducted during April 2007 mainly for validation of the IASI on the MetOp satellite. IASI possesses an ultra-spectral resolution of 0.25/cm and a spectral coverage from 645 to 2760/cm. Ultra-spectral resolution infrared spectral radiance obtained from near nadir observations provide atmospheric, surface, and cloud property information. An advanced retrieval algorithm with a fast radiative transfer model, including cloud effects, is used for atmospheric profile and cloud parameter retrieval. This physical inversion scheme has been developed, dealing with cloudy as well as cloud-free radiance observed with ultraspectral infrared sounders, to simultaneously retrieve surface, atmospheric thermodynamic, and cloud microphysical parameters. A fast radiative transfer model, which applies to the cloud-free and/or clouded atmosphere, is used for atmospheric profile and cloud parameter retrieval. A one-dimensional (1-d) variational multi-variable inversion solution is used to improve an iterative background state defined by an eigenvector-regression-retrieval. The solution is iterated in order to account for non-linearity in the 1-d variational solution. It is shown that relatively accurate temperature and moisture retrievals are achieved below optically thin clouds. For optically thick clouds, accurate temperature and moisture profiles down to cloud top level are obtained. For both optically thin and thick cloud situations, the cloud top height can be retrieved with relatively high accuracy (i.e., error Interferometer (NAST-I), dedicated dropsondes, radiosondes, and ground based Raman Lidar. The capabilities of satellite ultra-spectral sounder such as the IASI are investigated indicating a high vertical structure of atmosphere is retrieved.

  1. Optimizing a remote sensing instrument to measure atmospheric surface pressure

    Science.gov (United States)

    Peckham, G. E.; Gatley, C.; Flower, D. A.

    1983-01-01

    Atmospheric surface pressure can be remotely sensed from a satellite by an active instrument which measures return echoes from the ocean at frequencies near the 60 GHz oxygen absorption band. The instrument is optimized by selecting its frequencies of operation, transmitter powers and antenna size through a new procedure baesd on numerical simulation which maximizes the retrieval accuracy. The predicted standard deviation error in the retrieved surface pressure is 1 mb. In addition the measurements can be used to retrieve water vapor, cloud liquid water and sea state, which is related to wind speed.

  2. About an ozone layer dynamics in the atmosphere above Kazakhstan territory

    International Nuclear Information System (INIS)

    The summary of achievements in the field of ozone layer protection in atmosphere is presented. The stratosphere ozone changes above Kazakhstan territory on the base of ozone-measuring station data during 1973-1992 are given. It was established that the sum ozone departures have been decreased on minus of 3,2 % every year in comparison with average values. This process can conduct to increase of ultraviolet radiation coming to lower troposphere layers

  3. Hierarchy of adhesion forces in patterns of photoreactive surface layers

    Science.gov (United States)

    Hlawacek, Gregor; Shen, Quan; Teichert, Christian; Lex, Alexandra; Trimmel, Gregor; Kern, Wolfgang

    2009-01-01

    Precise control of surface properties including electrical characteristics, wettability, and friction is a prerequisite for manufacturing modern organic electronic devices. The successful combination of bottom up approaches for aligning and orienting the molecules and top down techniques to structure the substrate on the nano- and micrometer scale allows the cost efficient fabrication and integration of future organic light emitting diodes and organic thin film transistors. One possibility for the top down patterning of a surface is to utilize different surface free energies or wetting properties of a functional group. Here, we used friction force microscopy (FFM) to reveal chemical patterns inscribed by a photolithographic process into a photosensitive surface layer. FFM allowed the simultaneous visualization of at least three different chemical surface terminations. The underlying mechanism is related to changes in the chemical interaction between probe and film surface.

  4. Quantified In Situ Analysis of Initial Atmospheric Corrosion : Surface heterogeneity, galvanic effects and corrosion product distribution on zinc, brass and Galvalume

    OpenAIRE

    Qiu, Ping

    2011-01-01

    The interaction of the surface of a pure metal or an alloy with the surrounding atmosphere occurs in a highly complex interfacial regime. During atmospheric corrosion this interfacial regime involves the metal surface, often covered by a naturally formed oxide layer of a few nanometers thickness; an aqueous adlayer, typically with a thickness of a few to a few tens of nanometers, and the atmosphere from which airborne particles, oxygen, and gaseous pollutants dissolve into the adlayer and inf...

  5. Anode layer in a high-current arc in atmospheric pressure nitrogen

    Energy Technology Data Exchange (ETDEWEB)

    Nemchinsky, Valerian A [ESAB Welding and Cutting Products and Francis Marion University, Florence, SC 29501 (United States)

    2005-11-21

    An anode layer in a high-current atmospheric nitrogen arc was modelled. Calculations were made in a one-dimensional approximation at current densities in the range 500-3000 A cm{sup -2}. Two-temperature approximation was used. We calculated the distributions of both electron and heavy particle temperatures, the concentrations of charged and neutral particles and the electric field inside the anode layer. It was shown that for the conditions that exist in the anode layer of a high-current atmospheric pressure arc in nitrogen (a) the concentration of the molecular ions is negligible and (b) the concentration of atoms exceeds the concentration of molecules everywhere in the anode layer except in a narrow region close to the anode. Calculation showed that the electric field decreases towards the anode, and then close to the anode it rises again. Contrary to the situation in argon, the present calculations showed that in nitrogen the electric field in the anode layer is always accelerating. However, the average electric field in the anode layer is weaker than in the adjacent arc column (the so-called negative anode layer voltage). The voltage drop in the Langmuir sheath is also negative. It is shown that the main difference in anode layer voltages between an arc in nitrogen and an arc in argon is due to the high reactive thermal conductivity in nitrogen.

  6. 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.

  7. Experimental investigations and DICTRA simulations on formation of diffusion-controlled fcc-rich surface layers on cemented carbides

    Science.gov (United States)

    Garcia, José; Prat, Orlando

    2011-08-01

    Wear resistant fcc-rich surface layers were produced on cemented carbides by nitridation of W-Ti-Ta-Nb-Co-C compositions at 1400 °C in nitrogen atmosphere. A 15 ± 3 μm thick (Ti,Ta,Nb,W)(C,N) top-layer formed on the surface of the cemented carbides. The driving force for formation of the fcc-rich layers was the difference in nitrogen activity between the sintering atmosphere and the cemented carbide bulk, which promoted in-diffusion of nitrogen and out-diffusion of Ti, Ta and Nb. The diffusion-controlled process was modeled by DICTRA considering that all diffusion occurred in the liquid binder phase of a dispersed system model with a labyrinth factor of λ( f) = f. Good agreement between experimental and simulations regarding layer thickness, phase fraction distribution and element profiles was obtained for the presented model.

  8. Experimental investigations and DICTRA simulations on formation of diffusion-controlled fcc-rich surface layers on cemented carbides

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Jose, E-mail: jose.garcia@helmholtz-berlin.de [Helmholtz-Zentrum Berlin fuer Materialien und Energie GmbH, Hahn-Meitner-Platz 1, D-14109 Berlin (Germany); Prat, Orlando [Max Planck Institute fuer Eisenforschung GmbH, Max Planck Str. 1, D-40237 Duesseldorf (Germany)

    2011-08-15

    Wear resistant fcc-rich surface layers were produced on cemented carbides by nitridation of W-Ti-Ta-Nb-Co-C compositions at 1400 {sup o}C in nitrogen atmosphere. A 15 {+-} 3 {mu}m thick (Ti,Ta,Nb,W)(C,N) top-layer formed on the surface of the cemented carbides. The driving force for formation of the fcc-rich layers was the difference in nitrogen activity between the sintering atmosphere and the cemented carbide bulk, which promoted in-diffusion of nitrogen and out-diffusion of Ti, Ta and Nb. The diffusion-controlled process was modeled by DICTRA considering that all diffusion occurred in the liquid binder phase of a dispersed system model with a labyrinth factor of {lambda}(f) = f. Good agreement between experimental and simulations regarding layer thickness, phase fraction distribution and element profiles was obtained for the presented model.

  9. Experimental investigations and DICTRA simulations on formation of diffusion-controlled fcc-rich surface layers on cemented carbides

    International Nuclear Information System (INIS)

    Wear resistant fcc-rich surface layers were produced on cemented carbides by nitridation of W-Ti-Ta-Nb-Co-C compositions at 1400 oC in nitrogen atmosphere. A 15 ± 3 μm thick (Ti,Ta,Nb,W)(C,N) top-layer formed on the surface of the cemented carbides. The driving force for formation of the fcc-rich layers was the difference in nitrogen activity between the sintering atmosphere and the cemented carbide bulk, which promoted in-diffusion of nitrogen and out-diffusion of Ti, Ta and Nb. The diffusion-controlled process was modeled by DICTRA considering that all diffusion occurred in the liquid binder phase of a dispersed system model with a labyrinth factor of λ(f) = f. Good agreement between experimental and simulations regarding layer thickness, phase fraction distribution and element profiles was obtained for the presented model.

  10. MAIC-2, a latitudinal model for the Martian surface temperature, atmospheric water transport and surface glaciation

    CERN Document Server

    Greve, Ralf; Stenzel, Oliver J

    2009-01-01

    The Mars Atmosphere-Ice Coupler MAIC-2 is a simple, latitudinal model, which consists of a set of parameterizations for the surface temperature, the atmospheric water transport and the surface mass balance (condensation minus evaporation) of water ice. It is driven directly by the orbital parameters obliquity, eccentricity and solar longitude (Ls) of perihelion. Surface temperature is described by the Local Insolation Temperature (LIT) scheme, which uses a daily and latitude-dependent radiation balance, includes a treatment of the seasonal CO2 cap, and has been validated against the surface temperatures from the Mars Climate Database. The evaporation rate of water is calculated by an expression for free convection, driven by density differences between water vapor and ambient air, and the condensation rate follows from the assumption that any water vapour which exceeds the local saturation pressure condenses instantly. Atmospheric transport of water vapour is assumed to be purely diffusive, with an adjustable...

  11. 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

  12. The Zodiacal Cloud Model applied to the Martian atmosphere. Diurnal variations in Meteoric ion layers

    Science.gov (United States)

    Diego Carrillo-Sánchez, Juan; Plane, John M. C.; Withers, Paul; Fallows, Kathryn; Nesvorný, David; Pokorný, Petr; Feng, Wuhu

    2016-04-01

    Sporadic metal layers have been detected in the Martian atmosphere by radio occultation measurements using the Mars Express Orbiter and Mars Global Surveyor spacecraft. More recently, metallic ion layers produced by the meteor storm event following the close encounter between Comet Siding Spring (C/2013 A1) and Mars were identified by the Imaging UltraViolet Spectrograph (IUVS) aboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. However, the background metal layers produced by the influx of sporadic meteors have not yet been detected at Mars (contrary to the permanent metal layers identified in the Earth's atmosphere). The Zodiacal Dust Cloud (ZDC) model for particle populations released by asteroids (AST), and dust grains from Jupiter Family Comets (JFC) and Halley-Type Comets (HTC) has been combined with a Monte Carlo sampling method and the Chemical ABlation MODel (CABMOD) to predict the ablation rates of Na, K, Fe, Si, Mg, Ca and Al above 40 km altitude in the Martian atmosphere. CABMOD considers the standard treatment of meteor physics, including the balance of frictional heating by radiative losses and the absorption of heat energy through temperature increases, melting phase transitions and vaporization, as well as sputtering by inelastic collisions with the air molecules. These vertical profiles are input into the Leeds 1-D Mars atmospheric model which includes photo-ionization, and gas-phase ion-molecule and neutral chemistry, in order to explore the evolution of the resulting metallic ions and atoms. We conclude that the formation of the sporadic ion layers observed below 100 km with a plasma density exceeding 104 cm-3 requires the combination of the three different influx sources considered by the ZDC model, with a significant asteroidal contribution. Finally, we explore the changes of the neutral and ionized Mg and Fe layers over a diurnal cycle.

  13. Surface fluxes and convective boundary layer instability in summer over harvested wheat fields in Oklahoma

    Science.gov (United States)

    Li, W.; Barros, A. P.

    2008-05-01

    Vertical profiles of wind, pressure, air temperature and humidity up to 500 m obtained from measurements by a tethersonde system were used in combination with upper level temperature and humidity soundings from Rapid Update Cycle (RUC), to calculate Convective Available Potential Energy (CAPE) in an unstable boundary layer. The surface fluxes of sensible and latent heat were also calculated based on turbulent similarity theory for the atmospheric surface layer. The measurements were performed during the Cloud and Land Surface Interaction Campaign (CLASIC) June 2007 that includes pre-storm and post-storm conditions for a record monthly rainfall in excess of 300 mm at the site. The daytime trajectories of the surface layer in the Relative-Humidity and Bowen Ratio phase-space are consistent with the rainfall and aridity attractors in previous studies, with strong decrease in the post-storm periods. The decrease of Bowen ratio was the result of a strong decrease in the magnitude of sensible heat fluxes. The latent heat fluxes in the post-storm environment were not significantly different from the pre-storm environment, which is explained by a significant decrease in the net radiation. High soil moisture and increased moisture in boundary layer in the post-storm environment led to sustained low-level instability and daily evening showers. The diurnal cycle of potential temperature and specific humidity during the duration of the field campaign with an emphasis on conditions before and after one major rainy event are also discussed in this study.

  14. A surface layer variance heat budget for ENSO

    Science.gov (United States)

    Boucharel, Julien; Timmermann, Axel; Santoso, Agus; England, Matthew H.; Jin, Fei-Fei; Balmaseda, Magdalena A.

    2015-05-01

    Characteristics of the El Niño-Southern Oscillation (ENSO), such as frequency, propagation, spatial extent, and amplitude, strongly depend on the climatological background state of the tropical Pacific. Multidecadal changes in the ocean mean state are hence likely to modulate ENSO properties. To better link background state variations with low-frequency amplitude changes of ENSO, we develop a diagnostic framework that determines locally the contributions of different physical feedback terms on the ocean surface temperature variance. Our analysis shows that multidecadal changes of ENSO variance originate from the delicate balance between the background-state-dependent positive thermocline feedback and the atmospheric damping of sea surface temperatures anomalies. The role of higher-order processes and atmospheric and oceanic nonlinearities is also discussed. The diagnostic tool developed here can be easily applied to other tropical ocean areas and climate phenomena.

  15. Monitoring of the atmospheric ozone layer and natural ultraviolet radiation: Annual report 2014

    OpenAIRE

    Svendby, Tove Marit; Edvardsen, Kåre; Hansen, Georg Heinrich; Stebel, Kerstin; Dahlback, Arne

    2015-01-01

    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 2014. The ozone layer was below the long-term mean in spring 2014, but increased in April/May and was close to normal rest of the year. A clear decrease in total ozone above Norway during the period 1979-1997 stopped after 1998 and the ozone layer above Norway now seems to have stabilized.

  16. 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.

  17. 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.

  18. Atmospheric-Pressure Plasma Cleaning of Contaminated Surfaces

    International Nuclear Information System (INIS)

    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

  19. Modification of Surface Layers by Surfacing Intermetallic Coatings with Variable Properties

    Science.gov (United States)

    Makeev, D. N.; Zakharov, O. V.; Vinogradov, A. N.; Kochetkov, A. V.

    2016-02-01

    The paper considers the possibility of forming coating layers for parts within wide limits of microhardness. The technology uses surfacing of intermetallic coatings provided by a unique experimental setup. Theoretical and experimental dependence of the coating layer microhardness on the filler concentration using the changes in the speed of the filler wire feed and current intensity were determined.

  20. Pilot project of measuring and computing system for mesoscale monitoring of atmospheric boundary layer

    Science.gov (United States)

    Korolkov, V. A.; Tikhomirov, A. A.; Telminov, A. E.; Komarov, A. I.; Kobzev, A. A.

    2015-11-01

    Conception of design of measuring and computing system for monitoring atmospheric boundary layer is proposed. The system includes: stationary measuring complex consisting of four multiple-elevation ultrasonic weather stations and mobile measuring complex consisting of transportable weather station, touch probing system of weather data profile based on unmanned aerial vehicle and also Raman scattering gas analyzer, and new modification mercury gas analyzer.

  1. 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).

  2. 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

  3. 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 c

  4. Modelled suppression of boundary-layer clouds by plants in a CO2-rich atmosphere

    NARCIS (Netherlands)

    Vilà-Guerau de Arellano, J.; Heerwaarden, van C.C.; Lelieveld, J.

    2012-01-01

    Cumulus clouds in the atmospheric boundary layer play a key role in the hydrologic cycle, in the onset of severe weather by thunderstorms and in modulating Earth’s reflectivity and climate1. How these clouds respond to climate change, in particular over land, and how they interact with the carbon cy

  5. Equipment for atmospheric, spatial atomic layer deposition in roll-to-roll processes

    NARCIS (Netherlands)

    Knaapen, R.; Poodt, P.; Olieslagers, R.; Lankhorst, A.; Boer, M. van den; Berg, D. van den; Asten, A. van; Roozeboom, F.

    2012-01-01

    A novel type of reactor has been designed for atmospheric atomic layer deposition (ALD) on flexible substrates. In the reactor, a flexible substrate slowly advances around a fast rotating drum. Gas bearing technology is used to prevent physical contact between the flexible substrate and the drum, an

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

    Science.gov (United States)

    Norberg, Seth A.; Johnsen, Eric; Kushner, Mark J.

    2015-07-01

    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/O2 = 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.

  7. A new method for estimating aerosol mass flux in the urban surface layer using LAS technology

    Science.gov (United States)

    Yuan, Renmin; Luo, Tao; Sun, Jianning; Liu, Hao; Fu, Yunfei; Wang, Zhien

    2016-04-01

    Atmospheric aerosol greatly influences human health and the natural environment, as well as the weather and climate system. Therefore, atmospheric aerosol has attracted significant attention from society. Despite consistent research efforts, there are still uncertainties in understanding its effects due to poor knowledge about aerosol vertical transport caused by the limited measurement capabilities of aerosol mass vertical transport flux. In this paper, a new method for measuring atmospheric aerosol vertical transport flux is developed based on the similarity theory of surface layer, the theory of light propagation in a turbulent atmosphere, and the observations and studies of the atmospheric equivalent refractive index (AERI). The results show that aerosol mass flux can be linked to the real and imaginary parts of the atmospheric equivalent refractive index structure parameter (AERISP) and the ratio of aerosol mass concentration to the imaginary part of the AERI. The real and imaginary parts of the AERISP can be measured based on the light-propagation theory. The ratio of the aerosol mass concentration to the imaginary part of the AERI can be measured based on the measurements of aerosol mass concentration and visibility. The observational results show that aerosol vertical transport flux varies diurnally and is related to the aerosol spatial distribution. The maximum aerosol flux during the experimental period in Hefei City was 0.017 mg m-2 s-1, and the mean value was 0.004 mg m-2 s-1. The new method offers an effective way to study aerosol vertical transport in complex environments.

  8. Continuous atmospheric boundary layer observations in the coastal urban area of Barcelona, Spain

    OpenAIRE

    Pandolfi, M.; Martucci, G.; X. Querol; Alastuey, A.; F. Wilsenack; Frey, S.; C. D. O'Dowd; Dall'Osto, M.

    2013-01-01

    Continuous measurements of Surface Mixed Layer (SML), Decoupled Residual/Convective Layer (DRCL) and aerosol backscatter coefficient were performed within the Barcelona (NE Spain) boundary layer from September to October 2010 (30 days) in the framework of the SAPUSS (Solving Aerosol Problems Using Synergistic Strategies) field campaign. Two near-infrared ceilometers (Jenoptik CHM15K) vertically and horizontally-probing (only vertical profiles are discussed) were deployed during SAPUSS and ...

  9. Continuous atmospheric boundary layer observations in the coastal urban area of Barcelona during SAPUSS

    OpenAIRE

    Pandolfi, M.; Martucci, G.; X. Querol; Alastuey, A.; F. Wilsenack; Frey, S.; C. D. O'Dowd; Dall'Osto, M.

    2013-01-01

    Continuous measurements of surface mixed layer (SML), decoupled residual/convective layer (DRCL) and aerosol backscatter coefficient were performed within the Barcelona (Spain) boundary layer from September to October 2010 (30 days) in the framework of the SAPUSS (Solving Aerosol Problems by Using Synergistic Strategies) field campaign. Two near-infrared ceilometers (Jenoptik CHM15K), vertically and horizontally probing (only vertical profiles are herein discussed), were deployed. Ceilometer-...

  10. [Study on the infrared spectra and raman spectra of steel rusty layer with atmospheric corrosion].

    Science.gov (United States)

    Yang, Xiao-mei

    2006-12-01

    In the present study two methods, infrared and Raman spectral analyses, were used to measure the rusty layer of samples with atmospheric corrosion from Qingdao. The main component rust phase of the rusty layer was observed, showing that the relative content of the rust phase varies with the change in corrosion time. The main component rust phases of the rusty layer were found to be alpha-Fe2O3 , gamma-FeOOH, alpha-FeOOH, delta-FeOOH and Fe3O4, with the relative content of each rust phase of A3 (1) rusty layer sample exhibiting the following relation: gamma-FeOOH> alpha-FeOOH>delta-FeOOH, and the relative contents of other rusty layer samples were found to follow the relation: gamma-FeOOH> delta-FeOOH>alpha-FeOOH. PMID:17361722

  11. Scattering from a rough surface in presence of atmospheric turbulence

    Science.gov (United States)

    Basu, Santasri; Hyde, Milo W.; McCrae, Jack E.; Fiorino, Steven T.

    2013-05-01

    A Gaussian Schell Model (GSM) might be a convenient way to model extended beacons created on diffuse targets. Earlier, we used a full wave computational technique called the Method of Moments (MoM) to evaluate the scattered field from a rough impedance surface in vacuum. The MoM model showed several deviations from GSM. The present work uses a simulation approach based on physical optics approximation to study the scattering behavior in presence of atmospheric turbulence. A fully coherent beam is propagated through weak turbulence and is incident on the rough surface. The light scattered from the rough surface is again propagated through turbulence back to the source plane and the properties of the scattered radiation are studied through numerical simulations. The simulation results are compared with a GSM.

  12. Atmospheric controls on soil moisture-boundary layer interactions: Three-dimensional wind effects

    Science.gov (United States)

    Findell, Kirsten L.; Eltahir, Elfatih A. B.

    2003-04-01

    This paper expands the one-dimensionally based CTP-HIlow framework for describing atmospheric controls on soil moisture-boundary layer interactions [, 2003] to three dimensions by including low-level wind effects in the analysis. The framework is based on two measures of atmospheric thermodynamic properties: the convective triggering potential (CTP), a measure of the temperature lapse rate between approximately 1 and 3 km above the ground surface, and a low-level humidity index, HIlow. These two measures are used to distinguish between three types of early morning soundings: those favoring rainfall over dry soils, those favoring rainfall over wet soils, and those whose convective potential is unaffected by the partitioning of fluxes at the surface. The focus of this paper is the additional information gained by incorporating information about low-level winds into the CTP-HIlow framework. Three-dimensional simulations using MM5 and an analysis of observations from the FIFE experiment within this framework highlight the importance of the winds in determining the sensitivity of convection to fluxes from the land surface. A very important impact of the 3D winds is the potential for low-level backing or unidirectional winds with great shear to suppress convective potential. Because of this suppression of convection in certain wind conditions, far fewer simulations produced rain than would be anticipated based solely on the 1D framework of understanding. However, when the winds allowed, convection occurred in a manner consistent with the 1D-based expectations. Generally speaking, in the regime where dry soils were expected to have an advantage, convection was triggered over dry soils more often than over wet; in the regime where wet soils were expected to have an advantage, convection was more frequently triggered over wet soils than over dry. Additionally, when rainfall occurred in both simulations with wet soils and simulations with dry soils for a given day, rainfall

  13. 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;

    This thesis describes the further development and validation of the dynamic meandering wake model for simulating the flow field and power production of wind farms operating in the atmospheric boundary layer (ABL). The overall objective of the conducted research is to improve the modelling...... of the wind industry, four areas were identified as high prioritizations for further research: 1. the turbulence distribution in a single wake 2. multiple wake deficits and build-up of turbulence over a row of turbines 3. the effect of the atmospheric boundary layer on wake turbulence and wake deficit...... 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...

  14. Linking evaporative fluxes from bare soil across surface viscous sublayer with the Monin-Obukhov atmospheric flux-profile estimates

    Science.gov (United States)

    Haghighi, Erfan; Or, Dani

    2015-06-01

    The Monin-Obukhov similarity theory (MOST) provides the theoretical basis for many "atmospheric-based" methods (such as eddy covariance and flux-profile methods) that are widely used for quantifying surface-atmosphere exchange processes. The turbulence driven and highly nonlinear profiles of momentum, air temperature, and vapor densities require complex resistance expressions applied to simple gradients deduced from a single or few height measurements. Notwithstanding the success of these atmospheric-based methods, they often leave a gap at the immediate vicinity of terrestrial surfaces where fluxes emanate. A complementary approach for quantifying surface fluxes relies on diffusive interactions across a viscous sublayer next to the surface, referred to as the "surface boundary layer (BL)" approach. This study (for bare soil) establishes formal links between these two approaches thereby offering a physically based lower boundary condition (BC) for flux-profile methods while improving the top BC for surface BL-based formulations to include atmospheric stability. The modified lower BC for flux-profile relationships links characteristics of drying evaporating surfaces considering nonlinearities between wetness and evaporative fluxes and obviates reliance on both profile measurements and empirical surface resistances. The revised top BC for surface BL methods greatly improves the agreement with published field-scale experimental measurements. The proposed reconciliation procedure improves estimation capabilities of both flux-profile and surface BL formulations, and considerably enhances their accuracy of flux estimation when applied theoretically (in the absence of measured profiles) to drying bare soil surfaces.

  15. 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.

  16. Adjustment of the summertime marine atmospheric boundary layer to the western Iberia coastal morphology

    Science.gov (United States)

    Monteiro, Isabel T.; Santos, Aires J.; Belo-Pereira, Margarida; Oliveira, Paulo B.

    2016-04-01

    During summer (June, July, and August), northerly winds driven by the Azores anticyclone are prevalent over western Iberia. The Quick Scatterometer Satellite 2000 to 2009 summertime estimates reveal a broad high wind speed (≥7 ms-1) area extending about 300 km from shore and along the entire Iberian west coast. Nested in this large high-speed region, preferred maximum regions anchored in the Iberian major capes, Finisterre, Roca, and S. Vicente, are found. Composite analyses of wind maxima were performed to diagnose the typical summertime synoptic-scale pressure distribution associated with these smaller size high-speed regions. The flow low-level structure was further studied with a mesoscale numerical prediction model for three northerly events characterized by typical summertime synoptic conditions. A low-level coastal jet, setting the background conditions to the marine atmospheric boundary layer (MABL) response to topography, was found in the three cases. The causes for wind maximum downwind capes were investigated, focusing on the hypothesis that western Iberia MABL responds to hydraulic forcing. For the three events supercritical and transcritical flow conditions were identified and expansion fan signatures were found downwind each cape. Aircraft measurements, performed during one of the events, gave additional evidence of the expansion fan leeward Cape Roca. The importance of other forcing mechanisms was also assessed by considering the hypothesis of downslope wind acceleration and found to be in direct conflict with soundings and surface observations.

  17. Surface analysis of polymers treated by remote atmospheric pressure plasma.

    Science.gov (United States)

    Gonzalez, Eleazar; Hicks, Robert F

    2010-03-01

    The surfaces of high-density polyethylene (HDPE), poly(methyl methacrylate) (PMMA), and polyethersulfone (PES) were treated with a low-temperature, atmospheric pressure oxygen and helium plasma. The polymers were exposed to the downstream afterglow of the plasma, which contained primarily oxygen atoms and metastable oxygen molecules ((1)Delta(g) O(2)), and no ions or electrons. X-ray photoelectron spectroscopy (XPS) of HDPE revealed that 20% of the carbon atoms were converted into oxidized functional groups, with about half of these being carboxylic acids. Attenuated total reflection infrared spectroscopy of all three polymers was obtained in order to determine the types of functional groups formed by atmospheric plasma exposure. It was found that the polymers were rapidly oxidized with addition of alcohols, ketones, and carboxylic acids to the carbon backbone. Chain scission occurred on HDPE and PMMA, while on PES the aromatic groups underwent ring-opening and insertion of carboxylic acid. PMID:19950952

  18. Boundary layer for non-newtonian fluids on curved surfaces

    International Nuclear Information System (INIS)

    By using the basic equation of fluid motion (conservation of mass and momentum) the boundary layer parameters for a Non-Newtonian, incompressible and laminar fluid flow, has been evaluated. As a test, the flat plate boundary layer is first analized and afterwards, a case with pressure gradient, allowing separation, is studied. In the case of curved surfaces, the problem is first developed in general and afterwards particularized to a circular cylinder. Finally suction and slip in the flow interface are examined. The power law model is used to represent the stress strain relationship in Non-Newtonian flow. By varying the fluid exponent one can then, have an idea of how the Non-Newtonian behavior of the flow influences the parameters of the boundary layer. Two equations, in an appropriate coordinate system have been obtained after an order of magnitude analysis of the terms in the equations of motion is performed. (Author)

  19. LABLE: A multi-institutional, student-led, atmospheric boundary layer experiment

    Energy Technology Data Exchange (ETDEWEB)

    Klein, P.; Bonin, T. A.; Newman, J. F.; Turner, D. D.; Chilson, P. B.; Wainwright, C. E.; Blumberg, W. G.; Mishra, S.; Carney, M.; Jacobsen, E. P.; Wharton, Sonia; Newsom, Rob K.

    2015-10-23

    This paper presents an overview of the Lower Atmospheric Boundary Layer Experiment (LABLE), which included two measurement campaigns conducted at the Atmospheric Radiation Measurement (ARM) Southern Great Plains site in Oklahoma during 2012 and 2013. LABLE was conducted as a collaborative effort between the University of Oklahoma (OU), the National Severe Storms Laboratory, Lawrence Livermore National Laboratory (LLNL), and the ARM program. LABLE can be considered unique in that it was designed as a multi-phase, low-cost, multi-agency collaboration. Graduate students served as principal investigators and took the lead in designing and conducting experiments aimed at examining boundary-layer processes. The main objective of LABLE was to study turbulent phenomena in the lowest 2 km of the atmosphere over heterogeneous terrain using a variety of novel atmospheric profiling techniques. Several instruments from OU and LLNL were deployed to augment the suite of in-situ and remote sensing instruments at the ARM site. The complementary nature of the deployed instruments with respect to resolution and height coverage provides a near-complete picture of the dynamic and thermodynamic structure of the atmospheric boundary layer. This paper provides an overview of the experiment including i) instruments deployed, ii) sampling strategies, iii) parameters observed, and iv) student involvement. To illustrate these components, the presented results focus on one particular aspect of LABLE, namely the study of the nocturnal boundary layer and the formation and structure of nocturnal low-level jets. During LABLE, low-level jets were frequently observed and they often interacted with mesoscale atmospheric disturbances such as frontal passages.

  20. Characterization of Rust Layer Formed on Low Alloy Steel Exposed in Marine Atmosphere

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The iron rust phases formed on Iow alloy steels containing different quantities of Cr element have been characterizedusing EPMA, Raman spectroscopy, TEM, optical microscopy etc. The ion selective properties of synthesized rust filmswith the same phase constituent as the atmospheric corrosion products were investigated using self-made apparatus.The results showed that corrosion loss of steels exposed in marine atmosphere decreased rapidly as the Cr contentof the steel was increased. Cr-containing steels were covered by a uniform compacted rust layer composed of fineparticles with an average diameter of several nanometers. Inner rust layer of Cr-containing steel (2 mass fraction)was composed of α-CrxFel-xOOH, with Cr content of about 5 mass fraction. Such rust layer showed cation selectiveproperty, and could depress the penetration of Cl- to contact substrate steel directly.

  1. Contribution of the Atmospheric Dynamics to the Sporadic Sodium Layer Formation

    Institute of Scientific and Technical Information of China (English)

    杨国韬; 王嘉珉; 刘炳模; 程学武; 万卫星; 龚顺生

    2002-01-01

    We report on a sporadic sodium layer (SSL) event observed by our Na fluorescence lidar at Wuhan, China (31°N, 114°E) on 16 March 1999, and we reveal some special behaviour. From careful analysis of various sodium content variations of the layer during the development of this SSL event, it is found that besides the sodium injection mechanism as expected, another mechanism which we call atmospheric dynamics also made a noticeable contribution to this SSL formation. Computer simulations confirmed that under the combined action ora suitable sodium injection and a bi-direction vertical wind field, an SSL profile can be reproduced with a pronounced SSL peak on a normal sodium layer, as we observed in this event. From these results, it is emphasized that atmospheric dynamics is important for SSL formation.

  2. Parameterization of Land Surface Processes to Study Boundary Layer Characteristics over a Semiarid Region in Northwest India.

    Science.gov (United States)

    Satyanarayana, A. N. V.; Lykossov, V. N.; Mohanty, U. C.; Machul'Skaya, E. E.

    2003-04-01

    The atmospheric boundary layer and land surface processes play a crucial role and affect large-scale phenomena such as monsoons. A comprehensive soil-vegetation parameterization scheme has been developed to understand the complex interaction of the transfer processes, such as heat and moisture within the atmospheric surface layer and the active land layer. In this scheme, attention is given to the accurate representation of soil heat and moisture by considering all three states of water and their phase transitions. This scheme is incorporated in a one-dimensional multilevel boundary layer model for accurate representation of energy exchange processes to study the boundary layer characteristics. Numerical experiments are carried out with this model using special datasets obtained from the Land Surface Processes Experiment (LASPEX-97) at Anand (22.4°N, 72.6°E), a semiarid region of the state of Gujarat in northwest India. For this study, a dry simulation in February 1997 and a wet situation in July 1997 are considered. The model-simulated temporal variation of the fluxes of sensible heat, latent heat, and net radiation and soil temperatures are compared with the available observations. The results suggest that this model is suitable for better representation of land surface processes and the PBL in large-scale atmospheric models.

  3. Formation of intermetallic surface layers with high intensity ion implantation

    International Nuclear Information System (INIS)

    Full text: Ion implantation is an effective method to produce the intermetallic phases and for improving of surface properties of the construction materials. From the variety of the well-known methods, the high intensity ion implantation is the most attractive one, since it allows us to obtain in the target materials the ion ion-alloyed layers with the thickness several orders greater than the ion projected range. The increase of the thickness of ion-alloyed surface layers at high intensity implantation can be achieved by the means of controlled heating of target by the ion beam, as well as by the saturation of the surface layer by high concentrated ion beam, followed by radiation-stimulated diffusion. Now the task of obtaining of high intensity ion beams is successfully solved not only for the gas ions, but also for the metals ions. The new vacuum-arc beam and plasma flow source 'Raduga-5' has the opportunity to carry out the implantation of the conductive material ions in the high intensity mode. The high intensity ion implantation allows us to form in the surface layer the fine dispersed intermetallic phases in order to improve the wear resistance and the heat resistance of the metallic work pieces. In the present work, titanium was used as a target for ion implantation. Ion implantation of aluminum ions into titanium was carried out using the 'Raduga-5' ion source at the accelerating voltage 20 kV. The surface sputtering was compensated by plasma deposition of ions. The variation of the time of the ion implantation allowed us to change the dose of the implanted aluminium ions. The chemical and phase composition, as well as morphologic structure of the ion-alloyed surface layers were analyzed by the Auger spectroscopy and by the transmission electron microscopy. Additionally, the tests of the tribological and mechanical properties of the implanted materials have been carried out. It was found out that increasing of the dose of aluminum ions from 2.2·1017 up to

  4. On the Effects of Surface Roughness on Boundary Layer Transition

    Science.gov (United States)

    Choudhari, Meelan M.; Li, Fei; Chang, Chau-Lyan; Edwards, Jack

    2009-01-01

    Surface roughness can influence laminar-turbulent transition in many different ways. This paper outlines selected analyses performed at the NASA Langley Research Center, ranging in speed from subsonic to hypersonic Mach numbers and highlighting the beneficial as well as adverse roles of the surface roughness in technological applications. The first theme pertains to boundary-layer tripping on the forebody of a hypersonic airbreathing configuration via a spanwise periodic array of trip elements, with the goal of understanding the physical mechanisms underlying roughness-induced transition in a high-speed boundary layer. The effect of an isolated, finite amplitude roughness element on a supersonic boundary layer is considered next. The other set of flow configurations examined herein corresponds to roughness based laminar flow control in subsonic and supersonic swept wing boundary layers. A common theme to all of the above configurations is the need to apply higher fidelity, physics based techniques to develop reliable predictions of roughness effects on laminar-turbulent transition.

  5. Atmospheric pressure plasma treatment of flat aluminum surface

    International Nuclear Information System (INIS)

    Highlights: • DCSBD plasma is applicable for activation and cleaning of flat aluminum surfaces. • Decrease in the value of the contact angle after 1 s plasma treatment was 93%. • EDX measurements confirmed removal of oil contamination by 50% decreasing of carbon. • XPS analyze shown decrease of carbon content and increase of aluminum hydroxide and oxyhydroxide. - Abstract: The atmospheric pressure ambient air and oxygen plasma treatment of flat aluminum sheets using the so-called Diffuse Coplanar Surface Barrier Discharge (DCSBD) were investigated. The main objective of this study is to show the possibility of using DCSBD plasma source to activate and clean aluminum surface. Surface free energy measurements, X-ray photoelectron spectroscopy (XPS), Scanning Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy (SEM/EDX) and Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) were used for the characterization of the aluminum surface chemistry and changes induced by plasma treatment. Short plasma exposure times (several seconds) led to a significant increase in the surface free energy due to changes of its polar components. Various ageing effects, depending on the storage conditions were observed and discussed. Effects of air and oxygen plasmas on the removal of varying degrees of artificial hydrocarbon contamination of aluminum surfaces were investigated by the means of EDX, ATR-FTIR and XPS methods. A significant decrease in the carbon surface content after the plasma treatment indicates a strong plasma cleaning effect, which together with high energy efficiency of the DCSBD plasma source points to potential benefits of DCSBD application in processing of the flat aluminum surfaces

  6. EM Propagation in Marine Atmospheric Boundary Layer: Analysis of RED Experiment Data

    Science.gov (United States)

    Hristov, T.; Friehe, C. A.

    2002-05-01

    The pattern of propagation for EM signals over the ocean is a combined result of the atmospheric refraction and scattering from the rough ocean surface. Here we study experimentally the structure of the atmospheric refractive index and the ocean surface statistics, pertinent to scattering. We are also interested in fluctuations of the refractive index induced by the ocean surface waves, which along with the turbulence contribute to the random refraction. However, these fluctuations exhibit behavior different from turbulence (e.g. their structure function does not follow the 2/3 scaling valid for the turbulent fluctuations) and require to be studied separately. We analyze data of atmospheric turbulence, humidity, temperature, and sea surface temperature and waves from the Rough Evaporation Duct experiment, conducted in part from the instrument platform FLIP in the open ocean north of Oahu, Hawaii.

  7. Fluid-dynamics of the nuclear surface Fermi-layer

    International Nuclear Information System (INIS)

    In the framework of the long-mean-free-path approach the fluid-dynamical model of the nuclear surface as a spherical Fermi-layer is formulated. It is shown that the model reproduces known results of Fermi-drop dynamics and permits the description of more low energy collective states in spherical nuclei. The quantum-capillary branch of low-lying surface excitations is predicted. The model gives an adequate description of both lowest and highest experimental collective energies. (author) 18 refs.; 8 figs

  8. Studies of stability of blade cascade suction surface boundary layer

    Institute of Scientific and Technical Information of China (English)

    DONG Xue-zhi; YAN Pei-gang; HAN Wan-jin

    2007-01-01

    Compressible boundary layers stability on blade cascade suction surface was discussed by wind tunnel experiment and numerical solution. Three dimensional disturbance wave Parabolized Stability Equations(PSE) of orthogonal Curvilinear Coordinates in compressible flow was deducted. The surface pressure of blade in wind tunnel experiment was measured. The Falkner-Skan equation was solved under the boundary conditions of experiment result, and velocity, pressure and temperature of average flow were obtained. Substituted this result for discretization of the PSE Eigenvalue Problem, the stability problem can be solved.

  9. The appearance of liquid surfaces and layers in routine radiographs

    International Nuclear Information System (INIS)

    As has been demonstrated, the interfaces between a gas and a body fluid or a contrast medium may be visualized in the radiographic image as various kinds of boundaries, as also may interfaces between a contrast medium and a body fluid. These can provide little diagnostic information. Data of clinical value are usually derived from boundaries that represent bounding surfaces of anatomic structures touched by the roentgen rays. In the interpretation of the radiographic image it is important to recognize whether a boundary represents an anatomic structure, a liquid surface or a diffusion layer. It is a traditional view that a liquid surface is visualized by a horizontal beam as a straight horizontal boundary and that the imaged surface is then also horizontal. As has been shown in the earlier investigations and the present one, this is not always the case, for these boundaries are usually curved with an upward concavity. It is important to bear in mind that also rays departing considerably from the horizontal may still touch the liquid surface in its meniscoid. Even a vertical beam will form a boundary when touching a meniscoid. It would also appear that the simple layering phenomenon can present difficulty in interpretation. Examples of this phenomenon that illustrate particularly important situations have been presented. Ambiguity associated with the interpretation of images produced by a vertical beam may be resolved with the aid of supplementary films exposed with a horizontal beam. (orig.)

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

    Science.gov (United States)

    Turner, Andrew; Bhat, Gs; Evans, Jonathan; Marsham, John; Martin, Gill; Parker, Douglas; Taylor, Chris; Bhattacharya, Bimal; Madan, Ranju; Mitra, Ashis; Mrudula, Gm; Muddu, Sekhar; Pattnaik, Sandeep; Rajagopal, En; Tripathi, Sachida

    2015-04-01

    The monsoon supplies the majority of water in South Asia, making understanding and predicting its rainfall vital for the growing population and economy. However, modelling and forecasting the monsoon from days to the season ahead is limited by large model errors that develop quickly, with significant inter-model differences pointing to errors in physical parametrizations such as convection, the boundary layer and land surface. These errors persist into climate projections and many of these errors persist even when increasing resolution. At the same time, a lack of detailed observations is preventing a more thorough understanding of monsoon circulation and its interaction with the land surface: a process governed by the boundary layer and convective cloud dynamics. The INCOMPASS project will support and develop modelling capability in Indo-UK monsoon research, including test development of a new Met Office Unified Model 100m-resolution domain over India. The first UK detachment of the FAAM research aircraft to India, in combination with an intensive ground-based observation campaign, will gather new observations of the surface, boundary layer structure and atmospheric profiles to go with detailed information on the timing of monsoon rainfall. Observations will be focused on transects in the northern plains of India (covering a range of surface types from irrigated to rain-fed agriculture, and wet to dry climatic zones) and across the Western Ghats and rain shadow in southern India (including transitions from land to ocean and across orography). A pilot observational campaign is planned for summer 2015, with the main field campaign to take place during spring/summer 2016. This project will advance our ability to forecast the monsoon, through a programme of measurements and modelling that aims to capture the key surface-atmosphere feedback processes in models. The observational analysis will allow a unique and unprecedented characterization of monsoon processes that

  11. Interactions between soil moisture and Atmospheric Boundary Layer at the Brazilian savana-type vegetation Cerrado

    Science.gov (United States)

    Pinheiro, L. R.; Siqueira, M. B.

    2013-05-01

    Before the large people influx and development of the central part of Brazil in the sixties, due to new capital Brasília, Cerrado, a typical Brazilian savanna-type vegetation, used to occupy about 2 million km2, going all the way from the Amazon tropical forest, in the north of the country, to the edges of what used to be of the Atlantic forest in the southeast. Today, somewhat 50% of this area has given place to agriculture, pasture and managed forests. It is forecasted that, at the current rate of this vegetation displacement, Cerrado will be gone by 2030. Understanding how Cerrado interacts with the atmosphere and how this interaction will be modified with this land-use change is a crucial step towards improving predictions of future climate-change scenarios. Cerrado is a vegetation adapted to a climate characterized by two very distinct seasons, a wet season (Nov-Mar) and dry season (May-Ago), with April and October being transitions between seasons. Typically, based on measurements in a weather station located in Brasilia, 75% of precipitation happens in the wet-season months and only 5% during dry-season. Under these circumstances, it is clear that the vegetation will have to cope with long periods of water stress. In this work we studied using numerical simulations, the interactions between soil-moisture, responsible for the water stress, with the Atmospheric Boundary Layer (ABL). The numerical model comprises of a Soil-Vegetation-Atmosphere model where the biophysical processes are represented with a big-leaf approach. Soil water is estimated with a simple logistic model and with water-stress effects on stomatal conductance are parameterized from local measurements of simultaneous latent-heat fluxes and soil moisture. ABL evolution is calculate with a slab model that considers independently surface and entrainment fluxes of sensible- and latent- heat. Temperature tropospheric lapse-rate is taken from soundings at local airport. Simulations of 30-day dry

  12. Effects on the atmospheric boundary layer of a solar eclipse in the Arctic

    Science.gov (United States)

    Sjöblom, Anna

    2010-05-01

    On 1 August 2008, a total solar eclipse took place in the Arctic and in Longyearbyen, the main settlement in the High Arctic archipelago of Svalbard (78° 13' N, 15° 37' E), the maximum solar coverage was 93%. The eclipse had a large impact on the atmospheric boundary layer and the local weather in general around Longyearbyen triggering a fog that lasted for three days. This fog grounded all air traffic to and from Svalbard and so in addition to the change in local weather, the eclipse also had economic and social consequences. Approximately 60% of Svalbard is covered with permanent ice and snow. Permafrost underlies most of the surface. In Longyearbyen, the midnight sun is present between 19 April and 23 August and so on the day of the eclipse the sun was about 30 degrees above the horizon at noon and 6 degrees above at midnight. A rare opportunity therefore occurred to study what happens when the sunlight is suddenly decreased after several months with no dark night. The maximum solar coverage at Longyearbyen took place at 10.41 Local Standard Time. The incoming shortwave radiation had then decreased from approximately 300 W m-2 before the start of the eclipse to 20 W m-2, i.e. less radiation than during a normal cloud free night at the same location at the same time of the year. Observations of turbulence and mean meteorological parameters were taken both over land and over a large fjord in the vicinity of Longyearbyen. In addition, cloud observations were recorded. Data have been analysed in detail from 31 July to 2 August, i.e., from one day before to one day after the eclipse. The simultaneous observations over land and over water showed that the atmospheric response was much faster and stronger over land than over water. Over land, the air temperature sank by 0.3-1.5°C, wind speed decreased, turbulent fluctuations were significantly reduced and the atmospheric stability changed from unstable to stable. Over the fjord, no clear minima in these parameters

  13. Measurements of Physical and Gas Exchanges between the Atmosphere and Surface at the Tiksi Hydrometeorological Observatory

    Science.gov (United States)

    Uttal, T.; Grachev, A. A.; Makshtas, A. P.; Repina, I.; Persson, O. P.; Laurila, T. J.; Crepinsek, S.

    2013-12-01

    In recent years a number of Arctic stations have installed micro-meteorological towers in recognition of the need to explicitly quantify the detailed exchanges between the surface and the atmosphere. One of the newer installations is a 20 meter tower in Tiksi, Russia that is located at 71.58N, 128.92E in the Russian Far East. The Tiksi tower is equipped with temperature, humidity and wind sensors at several levels (allowing the calculation of turbulent heat fluxes and fine scale characterization of the near-surface boundary layer) and H2O/CO2 sensors, It is located in near proximity to measurements of incoming and outgoing solar radiation (allowing energy balance calculations), and CH4 sensors, surface O3 measurements (allowing detection of ozone depletion events), and ancillary measurements of snow depth and permafrost active layer temperature profiles. An integrated analysis will look at the variability of these physical and chemical exchanges and variations over one annual cycle with an emphasis on detecting connections and linkages. This network of measurements supports the International Arctic Systems for Observing the Atmosphere (www.iasoa.org) and Global Cryosphere Watch (http://globalcryospherewatch.org/)

  14. The Impact of the Winter Monsoon on Marine Surface-Layer Turbulence

    Science.gov (United States)

    Nishida, Tomoya; Waseda, Takuji

    2015-10-01

    During winter the East-Asia monsoon is the dominant climatological phenomenon in the north-west Pacific, especially around the Japan Islands. Previous studies based on satellite and radiosonde observations revealed that cold and dry strong flow from Siberia over the warm Kuroshio Extension enhances instability of the marine boundary layer and reduces vertical wind shear. Since active convection manifests as intensification of near-surface turbulence, in situ meteorological buoy data were analyzed, confirming that turbulence intensity or equivalently the gust factor increases during the winter north-westerly monsoon. Concurrently, a hindcast atmospheric simulation was conducted to quantify the thermal and vapour fluxes in the marine boundary layer. When large gust factors or turbulence intensity are observed, the buoyancy production plays an important role in the turbulent kinetic energy budget. To further clarify the respective roles of the sensible and latent heat fluxes at the sea surface, atmospheric model experiments showed that the sensible heat flux predominantly contributes to the increase in turbulence intensity. On the other hand, the latent heat flux mainly affects the generation of clouds at the top of the marine boundary layer.

  15. X-ray photoelectron spectroscopic study on surface reaction on titanium by laser irradiation in nitrogen atmosphere

    International Nuclear Information System (INIS)

    The surface reaction on titanium due to pulsed Nd:YAG laser irradiation in a nitrogen atmosphere was investigated using X-ray photoelectron spectroscopy (XPS). The laser, with a wavelength of 532 nm (SHG mode), was irradiated on a titanium substrate in an atmosphere-controlled chamber, and then the substrate was transported to an XPS analysis chamber without exposure to air. This in situ XPS technique makes it possible to clearly observe the intrinsic surface reaction. The characteristics of the surface layer strongly depend on the nitrogen gas pressure. When the pressure is 133 kPa, an oxynitride and a stoichiometric titanium nitride form the topmost and lower surface layers on the titanium substrate, respectively. However, only a nonstoichiometric titanium oxide layer containing a small amount of nitrogen is formed when the pressure is lower than 13.3 kPa. Repetition of laser shots promotes the formation of the oxide layer, but the formation is completed within a few laser shots. After the initial structure is formed, the chemical state of the surface layer is less influenced by the repetition of laser shots.

  16. Continuous atmospheric boundary layer observations in the coastal urban area of Barcelona, Spain

    Directory of Open Access Journals (Sweden)

    M. Pandolfi

    2013-01-01

    Full Text Available Continuous measurements of Surface Mixed Layer (SML, Decoupled Residual/Convective Layer (DRCL and aerosol backscatter coefficient were performed within the Barcelona (NE Spain boundary layer from September to October 2010 (30 days in the framework of the SAPUSS (Solving Aerosol Problems Using Synergistic Strategies field campaign. Two near-infrared ceilometers (Jenoptik CHM15K vertically and horizontally-probing (only vertical profiles are discussed were deployed during SAPUSS and compared with potential temperature profiles measured by daily radiosounding (midnight and midday to interpret the boundary layer structure in the urban area of Barcelona. Ceilometer-based DRCL (1761±363 m a.g.l. averaged over the campaign duration were twice as high as the mean SML (904±273 m a.g.l. with a marked SML diurnal cycle. The overall agreement between the ceilometer-retrieved and radiosounding-based SML heights (R2=0.8 revealed overestimation of the SML by the ceilometer (Δh=145±145 m. After separating the data in accordance with different atmospheric scenarios, the lowest SML (736±183 m and DRCL (1573±428 m were recorded during warm North African (NAF advected air mass. By contrast, higher SML and DRCL were observed during stagnant regional (REG (911±234 m and 1769±314 m, respectively and cold Atlantic (ATL (965±222 m and 1878±290 m, respectively air masses. The SML during the NAF scenario frequently showed a flat upper boundary throughout the day because of strong winds from the Mediterranean Sea that limit the midday SML convective growth observed during ATL and REG scenarios. The mean backscatter coefficients were calculated at two selected heights as representative of middle and top SML portions, i.e. β500=0.59±0.45 M m−1 sr−1 and β800=0.87±0.68 M m−1 sr−1 at 500 m and 800 m a.g.l., respectively. The highest backscatter coefficients were

  17. Surface chemistry of atmospheric plasma modified polycarbonate substrates

    International Nuclear Information System (INIS)

    Surface of polycarbonate substrates were activated by atmospheric plasma torch using different gas pressure, distance from the substrates, velocity of the torch and number of treatments. The modifications were analyzed by contact angle measurements, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and UV-vis spectrophotometry. Plasma treatment caused the surface characteristics to become more hydrophilic as measured by the water contact angle, which decreased from 88 deg. to 18 deg. The decrease in contact angle was mainly due to oxidation of the surface groups, leading to formation of polar groups with hydrophilic property. XPS results showed an increase in the intensity of -(C-O)- groups and also introduction of new functional groups i.e. -(O-C=O)- after the treatment process. AFM topographic images demonstrated an increase in the rms roughness of the surface from 2.0 nm to 4.0 nm caused by the treatment. Increase in rms roughness of the surface caused relevant decrease in transmission up to ∼2-5%.

  18. Etching of silicon surfaces using atmospheric plasma jets

    Science.gov (United States)

    Paetzelt, H.; Böhm, G.; Arnold, Th

    2015-04-01

    Local plasma-assisted etching of crystalline silicon by fine focused plasma jets provides a method for high accuracy computer controlled surface waviness and figure error correction as well as free form processing and manufacturing. We investigate a radio-frequency powered atmospheric pressure He/N2/CF4 plasma jet for the local chemical etching of silicon using fluorine as reactive plasma gas component. This plasma jet tool has a typical tool function width of about 0.5 to 1.8 mm and a material removal rate up to 0.068 mm3 min-1. The relationship between etching rate and plasma jet parameters is discussed in detail regarding gas composition, working distance, scan velocity and RF power. Surface roughness after etching was characterized using atomic force microscopy and white light interferometry. A strong smoothing effect was observed for etching rough silicon surfaces like wet chemically-etched silicon wafer backsides. Using the dwell-time algorithm for a deterministic surface machining by superposition of the local removal function of the plasma tool we show a fast and efficient way for manufacturing complex silicon structures. In this article we present two examples of surface processing using small local plasma jets.

  19. Etching of silicon surfaces using atmospheric plasma jets

    International Nuclear Information System (INIS)

    Local plasma-assisted etching of crystalline silicon by fine focused plasma jets provides a method for high accuracy computer controlled surface waviness and figure error correction as well as free form processing and manufacturing. We investigate a radio-frequency powered atmospheric pressure He/N2/CF4 plasma jet for the local chemical etching of silicon using fluorine as reactive plasma gas component. This plasma jet tool has a typical tool function width of about 0.5 to 1.8 mm and a material removal rate up to 0.068 mm3 min−1. The relationship between etching rate and plasma jet parameters is discussed in detail regarding gas composition, working distance, scan velocity and RF power. Surface roughness after etching was characterized using atomic force microscopy and white light interferometry. A strong smoothing effect was observed for etching rough silicon surfaces like wet chemically-etched silicon wafer backsides. Using the dwell-time algorithm for a deterministic surface machining by superposition of the local removal function of the plasma tool we show a fast and efficient way for manufacturing complex silicon structures. In this article we present two examples of surface processing using small local plasma jets. (paper)

  20. How are Gases Transferred from the Atmosphere to Snow and Ice Surfaces?

    Science.gov (United States)

    Abbatt, J.

    2005-12-01

    Aside from mass transfer through the gas phase, the rate-determining step for transferring a gas from the atmosphere to ice or snow is frequently determined by the chemistry of the gas-ice surface interaction. What are the kinetics of this uptake process? How are they affected as the surface becomes coated? What is the capacity of the surface to adsorb gaseous species? How does the uptake change if the ice is growing or evaporating? Does uptake to polycrystalline snow differ from that to ice of large crystal size? How does the uptake capacity of ice change at high temperatures, as the quasi-liquid layer thickness grows? To investigate these effects, this talk will focus on some recent studies we have performed in the laboratory using nitric acid and small oxygenated organics as the adsorbing molecules, and using both ice and polycrystalline snow samples.

  1. 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...

  2. Sterilisation properties of the Mars surface and atmospheric environment

    Science.gov (United States)

    Moreau, D.; Muller, C.

    The radiative and chemical conditions at the surface and in the lower Martian atmosphere are computed at various latitudes and seasons combining a 2D photochemical model and radiation simulations. In most situations, the solar UV B and C radiations reach the surface however, suspended dust and, in polar cases, ozone can constitute an effective UV shield. The daytime and night time concentrations of the sterilizing oxidants: /OH, H2O2 and O3 are determined, as well as the concentration of the substances which could influence the metabolism of microorganisms. The possible habitats of a remaining Mar's life as well as the possibilities of contamination by resistant earth life forms will be described.

  3. Impact of soil water property parameterization on atmospheric boundary layer simulation

    Science.gov (United States)

    Cuenca, Richard H.; Ek, Michael; Mahrt, Larry

    1996-03-01

    Both the form of functional relationships applied for soil water properties and the natural field-scale variability of such properties can significantly impact simulation of the soil-plant-atmosphere system on a diurnal timescale. Various input parameters for soil water properties including effective saturation, residual water content, anerobiosis point, field capacity, and permanent wilting point are incorporated into functions describing soil water retention, hydraulic conductivity, diffusivity, sorptivity, and the plant sink function. The perception of the meaning of these values and their variation within a natural environment often differs from the perspective of the soil physicist, plant physiologist, and atmospheric scientist. This article investigates the sensitivity of energy balance and boundary layer simulation to different soil water property functions using the Oregon State University coupled atmosphere-plant-soil (CAPS) simulation model under bare soil conditions. The soil parameterizations tested in the CAPS model include those of Clapp and Hornberger [1978], van Genuchten [1980], and Cosby et al. [1984] using initial atmospheric conditions from June 16, 1986 in Hydrologic Atmospheric Pilot Experiment-Modélisation du Bilan Hydrique (HAPEX-MOBILHY). For the bare soil case these results demonstrate unexpected model sensitivity to soil water property parameterization in partitioning all components of the diurnal energy balance and corresponding boundary layer development.

  4. Modelled suppression of boundary-layer clouds by plants in a CO2-rich atmosphere

    Science.gov (United States)

    Vila-Guerau Arellano, J.; Vanheerwaarden, C.; Lelieveld, J.

    2013-12-01

    We will present and discuss a conceptual modelling framework that can facilitate the understanding of the interactions between land processes and atmospheric boundary layer dynamics/chemistry at diurnal scales. This framework has been successful applied to the interpretation of field experiments, but also to identify the non-linear relations that occur at larger spatial and temporal scales. We will then discuss in depth the link between shallow cumulus and vegetation exchange of water and carbon dioxide. Cumulus clouds in the atmospheric boundary layer play a key role in the hydrologic cycle, in the onset of severe weather by thunderstorms, and in modulating the Earth's reflectivity and climate. How these clouds respond to climate change, in particular over land, and how they interact with the carbon cycle is poorly understood. It is expected that as a consequence of rising atmospheric CO2 the plant stomata will close leading to lower latent heat fluxes and higher sensible heat fluxes. During the presentation, we will show that this causes a decline in boundary layer cloud formation in middle latitudes. This could be partly counteracted by the greater ability of a warmer atmosphere to take up water and by a growth in biomass due to CO2 fertilization. Our results are based on a new soil-water-atmosphere-plant model supported by comprehensive observational evidence, from which we identify the dominant atmospheric responses to plant physiological processes. They emphasize the intricate connection between biological and physical aspects of the climate system and the relevance of short-term and small-scale processes in establishing this connection

  5. Surface heterogeneity impacts on boundary layer dynamics via energy balance partitioning

    Directory of Open Access Journals (Sweden)

    N. A. Brunsell

    2010-07-01

    Full Text Available 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 variability under three different horizontal wind speeds are used in the analysis. The base case uses Landsat ETM imagery over the Cloud Land Surface Interaction Campaign (CLASIC field site for 3 June 2007. Using wavelets, the surface fields are band-pass filtered in order to maintain the spatial mean and variances to length scales of 200 m, 1600 m, and 12.8 km as lower boundary conditions to the model. The simulations exhibit little variation in net radiation. Rather, a change in the partitioning of the surface energy between sensible and latent heat flux is responsible for differences in boundary layer dynamics. The sensible heat flux is dominant for intermediate surface length scales. For smaller and larger scales of surface heterogeneity, which can be viewed as being more homogeneous, the latent heat flux becomes increasingly important. The results reflect a general decrease of the Bowen ratio as the surface conditions transition from heterogeneous to homogeneous. Air temperature is less sensitive to surface heterogeneity than water vapor, which implies that the role of surface heterogeneity in modifying the local temperature gradients in order to maximize convective heat fluxes. More homogeneous surface conditions, on the other hand, tend to maximize latent heat flux. Scalar vertical profiles respond predictably to the partitioning of surface energy. Fourier spectra of the vertical wind speed, air temperature and specific humidity (w, T and q and associated cospectra (w'T', w'q' and T'q', however, are insensitive to the length scale of surface heterogeneity, but the near surface spectra are sensitive to the

  6. Mass Spectrometry of Atmospheric Pressure Surface Wave Discharges

    Science.gov (United States)

    Ridenti, M. A.; Souza-Corrêa, J. A.; Amorim, J.

    2016-05-01

    By applying mass spectrometry techniques, we carried out measurements of ionic mass spectrum and their energy distribution in order to investigate an atmospheric argon discharge by using a surfatron surface-wave device. The mass and energy distribution measurements were performed with fixed flow rate (2.5 SLM) of pure argon gas (99.999%) and different Ar-O2 gas mixture compositions (99-1, 98-2 and 97-3). The mass spectra and energy distributions were recorded for Ar+, O+, O+ 2, N+ and N2 +. The axial distribution profiles of ionic mass and their energy were obtained for different experimental conditions as a function of the plasma length. The results showed that the peak of the positive ion energy distributions shifted to higher energies and also that the distribution width increased as the distance between the sampling orifice and the launcher gap was increased. It was also found that under certain experimental conditions the ion flux of atomic species were higher than the ion flux of their diatomic counterpart. The motivation of this study was to obtain a better understanding of a surface wave discharge in atmospheric pressure that may play a key role on new second generation biofuel technologies.

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

    International Nuclear Information System (INIS)

    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/O2 = 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

  8. Complex measurements of aerosol and ion characteristics in the atmospheric boundary layer

    Science.gov (United States)

    Kikas, Iu. E.; Kolomiets, S. M.; Kornienko, V. I.; Mirme, A. A.; Sal'm, Ia. I.; Sergeev, I. Ia.; Tammet, Kh. F.

    Results of a comprehensive study of the characteristics of atmospheric ions and aerosols in the boundary layer during the summer season are reported. A study is also made of the kinetics of aerosol formation under conditions of high artificial ionization of the air by alpha and UV radiation. A high degree of correlation is shown to exist between atmospheric concentrations of medium ions and fine (less than 0.01 micron) aerosol. The results obtained support the radiation-chemical mechanism of aerosol formation.

  9. In-situ surface hardening of cast iron by surface layer metallurgy

    International Nuclear Information System (INIS)

    Abrasive wear is a serious problem in many cast iron castings used in industry. To minimize failure and repair of these components, different strategies exist to improve their surface microhardness thus enhancing their wear resistance. However, most of these methods lead to very brittle and/or expensive castings. In the current work a new method for surface hardening is presented which utilizes surface layer metallurgy to generate in-situ a boron-enriched white cast iron surface layer with a high microhardness on a gray cast iron casting. To do this, sand molds are coated with a ferroboron suspension and cast with a cast iron melt. After solidification, a 100–900 µm thick layer of boron-enriched ledeburite is formed on the surface of the casting which produces an increase in the average microhardness from 284 HV0.1±52 HV0.1 to 505 HV0.1±87 HV0.1. Analyses of the samples' core reveal a typical cast iron microstructure which leads to the conclusion that the coating mainly affects the castings' surface. By varying the grain size of the ferroboron powder in the coatings, it is shown that a powder size ≤100 µm is most suitable to create a boron-enriched ledeburite surface layer possessing high hardness values

  10. Open Contours Extraction of Rotational Surface Oriented to Layer Measurement

    Institute of Scientific and Technical Information of China (English)

    亓利伟; 赵毅; 李明辉

    2003-01-01

    With layer-measured contours, an algorithm that can extract the contour segments from a rotational surface is presented. The extraction can be divided into two stages, i. e. the rough segmentation and the refinement. In the rough segmenting stage, an optimal contour matching method is put forward to find similar contour segment from another closed contour with respect to the seed contour. In the refining stage, an iterative way that can extract a circular arc precisely is presented based on parameters identification and contour-ends expanding/shrinking operation. The algorithm can extract the open contour segments from a rotational surface precisely, as demonstrated in the examples. Based on the work of this paper, further research, such as parameter identification of 3 - D surface and CAD model creation, can be conducted.

  11. Nanoscale Structuring of Surfaces by Using Atomic Layer Deposition.

    Science.gov (United States)

    Sobel, Nicolas; Hess, Christian

    2015-12-01

    Controlled structuring of surfaces is interesting for a wide variety of areas, including microelectronic device fabrication, optical devices, bio(sensing), (electro-, photo)catalysis, batteries, solar cells, fuel cells, and sorption. A unique feature of atomic layer deposition (ALD) is the possibility to form conformal uniform coatings on arbitrarily shaped materials with controlled atomic-scale thickness. In this Minireview, we discuss the potential of ALD for the nanoscale structuring of surfaces, highlighting its versatile application to structuring both planar substrates and powder materials. Recent progress in the application of ALD to porous substrates has even made the nanoscale structuring of high-surface-area materials now feasible, thereby enabling novel applications, such as those in the fields of catalysis and alternative energy. PMID:26538495

  12. Physical modeling of the atmospheric boundary layer for wind energy and wind engineering studies

    Science.gov (United States)

    Taylor-Power, Gregory; Turner, John; Wosnik, Martin

    2015-11-01

    The Flow Physics Facility (FPF) at UNH has test section dimensions W6.0m, H2.7m, 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): the stable, unstable, and neutral ABL. The neutral ABL is characterized by a zero potential temperature gradient, which is readily achieved in the FPF by operating when air and floor temperatures are close to equal. The stable and unstable ABLs have positive and negative vertical temperature gradients, respectively, which are more difficult to simulate without direct control of air or test section floor temperature. The test section floor is a 10 inch thick concrete cement slab and has significant thermal mass. When combined with the diurnal temperature variation of the ambient air, it is possible to achieve vertical temperature gradients in the test section, and produce weakly stable or weakly unstable boundary layer. Achievable Richardson numbers and Obukhov lengths are estimated. The different boundary layer profiles were measured, and compared to theoretical atmospheric models. Supported by UNH Hamel Center for Undergraduate Research SURF.

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

    International Nuclear Information System (INIS)

    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 (H2O2) as oxidizing agent of lead layer on the chromium surface and acetic acid (CH3COOH) 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 deg. C), only 15-min time is needed for complete removal of 3 g fouling lead from a chromium surface.

  14. 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.

  15. Numerical study of the anode boundary layer in atmospheric pressure arc discharges

    Science.gov (United States)

    Semenov, I. L.; Krivtsun, I. V.; Reisgen, U.

    2016-03-01

    The anode boundary layer in atmospheric pressure arc discharges is studied numerically on the basis of the hydrodynamic (diffusion) equations for plasma components. The governing equations are formulated in a unified manner without the assumptions of thermal equilibrium, ionization equilibrium or quasi-neutrality. For comparison, a quasi-neutral model of the anode layer is also considered. The numerical computations are performed for an argon arc at typical values of the current density in anode layers (500-2000 A cm-2). The results of numerical modelling show that the common collisionless model of the sheath fails to describe the sheath region for the problem under consideration. For this reason, a detailed analysis of the anode sheath is performed using the results of unified modelling. In addition, the distributions of plasma parameters in the anode layer are analysed and the basic characteristics of the layer (anode voltage drop, sheath voltage drop, anode layer thickness, sheath thickness, heat flux to the anode) are calculated. Our results are found to be in good agreement with the existing theoretical predictions and experimental data. The dependence of the anode layer characteristics on the current density is also discussed.

  16. Soil moisture sensor calibration for organic soil surface layers

    Directory of Open Access Journals (Sweden)

    S. Bircher

    2015-12-01

    Full Text Available 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 Finish 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 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 surface areas compared to the studied mineral soils. ThetaProbe measurements from organic horizons showed stronger non-linearity 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 Sodankyl

  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. Effects of relative thickness of the duplex-treated layer on surface properties of AlSl H13 steel

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S.Y.; Chung, J.W. [Hankuk Aviation Univ., Koyang (Korea, Republic of). Dept. of Materials Engineering; Kim, C.W.; Han, J.G.; Kim, S.S. [Department of Metallurgical Engineering, Plasma Applied Materials Laboratory, SungKyunKwan University, KyungKi-Do 440-746 (Korea, Republic of); Lee, J.H. [Korea Institute of Machinery and Metals, ChangWon, KyungNam 641-010 (Korea, Republic of)

    1997-10-01

    A duplex surface treatment technique based on calorizing and plasma nitriding was developed to improve the wear and oxidation resistance of H13 steel at high temperatures. The effects of the relative thickness of the calorized layer to the depth of plasma nitriding on the wear and oxidation properties at temperatures up to 900 C were investigated in this work. High-temperature wear tests were performed at 500 C with dry conditions in open air using a ball-on-disk type tribotest machine. Isothermal oxidation tests were performed at 900 C for up to 100 h under controlled atmosphere. The results indicated that the specimens with a calorized layer as an intermediate phase between the surface duplex layer and the base metal showed higher wear and oxidation resistance than the specimens with a nitrided layer alone. During exposure to elevated temperatures, the aluminum in the calorized layer diffused to the surface and formed an aluminum oxide layer. This oxide layer protected the specimens from further oxidation and prevented the nitrogen from diffusing out of the surface, thus resulting in the retention of surface hardness even after exposure to high temperatures. (orig.) 11 refs.

  19. Processing and properties of electrodeposited layered surface coatings

    DEFF Research Database (Denmark)

    Horsewell, Andy

    1998-01-01

    clacks and spalls off early on. For thick, non-compliant coatings, much thicker coatings can be formed. Fracture resistance must be considered in relation to both specimen and loading geometries. Since the inherent bending moment causes a maximum tensile stress at the coating surface, the loading......Hard chromium, produced by conventional dir ect curl ent (DC) electrodeposition, cannot be deposited to thicknesses gl enter than about 5 mu m because of the buildup of processing stresses which cause channel cracks in the coating. Much thicker chromium coatings map be produced by depositing a...... layered structure using alternate DC plating and periodic current reversal (PR). Such layering produces a through thickness stepped gradient in residual stresses. Most importantly a bending moment develops in the coating whenever the substrate is compliant. For thin, compliant substrates, the coating...

  20. Gas permeation barriers deposited by atmospheric pressure plasma enhanced atomic layer deposition

    International Nuclear Information System (INIS)

    This paper reports on aluminum oxide (Al2O3) thin film gas permeation barriers fabricated by atmospheric pressure atomic layer deposition (APPALD) using trimethylaluminum and an Ar/O2 plasma at moderate temperatures of 80 °C in a flow reactor. The authors demonstrate the ALD growth characteristics of Al2O3 films on silicon and indium tin oxide coated polyethylene terephthalate. The properties of the APPALD-grown layers (refractive index, density, etc.) are compared to that deposited by conventional thermal ALD at low pressures. The films films deposited at atmospheric pressure show water vapor transmission rates as low as 5 × 10−5 gm−2d−1

  1. 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.

  2. Isotopic composition of atmospheric nitrate in a tropical marine boundary layer

    OpenAIRE

    Savarino, Joel; Morin, Samuel; Erbland, Joseph,; Grannec, Francis; Patey, Matthew D.; Vicars, William; Alexander, Becky; Achterberg, Eric P.

    2013-01-01

    Long-term observations of the reactive chemical composition of the tropical marine boundary layer (MBL) are rare, despite its crucial role for the chemical stability of the atmosphere. Recent observations of reactive bromine species in the tropical MBL showed unexpectedly high levels that could potentially have an impact on the ozone budget. Uncertainties in the ozone budget are amplified by our poor understanding of the fate of NOx (= NO + NO2), particularly the importance of nighttime chemi...

  3. WAVELET TRANSFORM METHOD FOR DERIVING ATMOSPHERIC BOUNDARY LAYER HEIGHT FROM LIDAR SIGNALS

    Directory of Open Access Journals (Sweden)

    RAJITHA PALETI

    2013-04-01

    Full Text Available Wavelet method of determining the atmospheric boundary layer (ABL height from lidar signals is presented in this paper. The wavelet covariance transform (WCT method employed determines the significant gradient in the measured lidar signals. Using this method, the accuracy of ABL height detection enhances with increased dilation length. The developed wavelet algorithm is coded in MATLAB software and has a provision to alter the dilation length in real-time for a given translation estimate.

  4. Thin layer chromatography/desorption atmospheric pressure photoionization-mass spectrometry of lipids

    Czech Academy of Sciences Publication Activity Database

    Rejšek, Jan; Vrkoslav, Vladimír; Cvačka, Josef

    Praha: Ústav organické chemie a biochemie AV ČR, 2016 - (Kuda, O.). s. 30 ISBN 978-80-86241-54-8. [Česká lipidomická konference /5./. 21.04.2016-22.04.2016, Praha] Institutional support: RVO:61388963 Keywords : desorption atmospheric pressure photoionization * ambient mass spectrometry * thin layer chromatography * lipids Subject RIV: CB - Analytical Chemistry, Separation

  5. Plasma boundary layer with active surface. Pt. 1

    International Nuclear Information System (INIS)

    The space-charge boundary layer between plasma and wall which is normally (almost) homogeneous may become instable and may decay into largely independent spots of plasma-induced unipolar-like discharges. In Tokamaks the existence of such highly inhomogeneous boundary plasmas often has been found by observation of arc tracks and of ''hot spots'' a.s.o. In this way wall erosion and production rates of plasma impurities will be enhanced, and several special phenomena of intense wall erosion (like ''carbon blooming'') may be traced back to such effects. In this paper the influence of electron emission from the wall (i.e. of an ''active'' surface) on the parameter of the space charge sheath is investigated, applying simple balance equations, as a first step towards an explanation of the transition from a homogeneous into an inhomogeneous boundary layer. Several variations of such models are calculated, using typical plasma parameters. Essential result is the dependence of the sheath potential and of the surface power density on the emission yield and on the net current density. Irrespective of the chosen constants the potential drop between plasma and wall turns out to become the higher the lower is the electron emission and the higher is the net current. Opposite is the dependence of the energy flux to the wall which, however, passes a minimum and increases rapidly again near the maximum net current jmax (with jmax∼jis(γ-1), where jis=ion saturation current, and γ=emission yield per ion). As a consequence, the wall loading is strongly enhanced as well in case of high negative net currents and intense electron emission, as near the maximum net current. This will be infavour of an instability of the boundary layer, resulting - with high probability - in the decay of the layer into plasma-induced arc spots. As a next step in this investigation of such plasma boundary layers a careful analysis of this transition is provided for, taking the specified conditions of the

  6. 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.

  7. Atmospheric Pressure Dielectric Barrier Discharges: A Low-Cost System for Surface Modification

    International Nuclear Information System (INIS)

    Plasma treatment is a common way for modifying the surface of a material. A simple but effective source for a low-temperature nonequilibrium plasma is dielectric barrier discharges (DBDs), also referred to as silent discharges. DBDs are characterized by the presence of at least one insulating (dielectric) layer in the discharge gap between two metal electrodes. When a high voltage is applied to the DBD configuration, tiny breakdown channels are formed in the discharge gap. These microdischarges are characterized as a weakly ionized plasma containing electrons with energies up to 10 eV and ions at room temperature. The energetic electrons provide an effective tool for chemical surface modification. Typical setups for DBD treatments consist of vacuum chambers and vacuum equipment, and so are very cost-intensive. Atmospheric pressure discharges provide a possibility for low-cost surface chemistry, because the setup consists only of the discharge set-up in normal air or in a specified inert gas atmosphere and a high-voltage amplifier coupled with a frequency generator. Silent discharges in air increase the wettability of polymer foils such as PTFE and FEP, sufficient for cell growth and further for surface-chemical binding of proteins onto the polymer. Thereby a simple and low-cost process to achieve protein chips for biomedical applications may be envisaged

  8. Combined surface acoustic wave and surface plasmon resonance measurement of collagen and fibrinogen layers

    CERN Document Server

    Friedt, J M; Francis, L; Zhou, C; Campitelli, A; Friedt, Jean-Michel; Denis, Frederic; Francis, Laurent; Zhou, Cheng; Campitelli, Andrew

    2003-01-01

    We use an instrument combining optical (surface plasmon resonance) and acoustic (Love mode acoustic wave device) real-time measurements on a same surface for the identification of water content in collagen and fibrinogen protein layers. After calibration of the surface acoustic wave device sensitivity by copper electrodeposition, the bound mass and its physical properties -- density and optical index -- are extracted from the complementary measurement techniques and lead to thickness and water ratio values compatible with the observed signal shifts. Such results are especially usefully for protein layers with a high water content as shown here for collagen on an hydrophobic surface. We obtain the following results: collagen layers include 70+/-20 % water and are 16+/-3 to 19+/-3 nm thick for bulk concentrations ranging from 30 to 300 ug/ml. Fibrinogen layers include 50+/-10 % water for layer thicknesses in the 6+/-1.5 to 13+/-2 nm range when the bulk concentration is in the 46 to 460 ug/ml range.

  9. Pluto's atmosphere

    International Nuclear Information System (INIS)

    Airborne CCD photometer observations of Pluto's June 9, 1988 stellar occultation have yielded an occultation lightcurve, probing two regions on the sunrise limb 2000 km apart, which reveals an upper atmosphere overlying an extinction layer with an abrupt upper boundary. The extinction layer may surround the entire planet. Attention is given to a model atmosphere whose occultation lightcurve closely duplicates observations; fits of the model to the immersion and emersion lightcurves exhibit no significant derived atmosphere-structure differences. Assuming a pure methane atmosphere, surface pressures of the order of 3 microbars are consistent with the occultation data. 43 references

  10. Effects of the March 2015 solar eclipse on near-surface atmospheric electricity.

    Science.gov (United States)

    Bennett, A J

    2016-09-28

    Measurements of atmospheric electrical and standard meteorological parameters were made at coastal and inland sites in southern England during the 20 March 2015 partial solar eclipse. Clear evidence of a reduction in air temperature resulting from the eclipse was found at both locations, despite one of them being overcast during the entire eclipse. The reduction in temperature was expected to affect the near-surface electric field (potential gradient (PG)) through a reduction in turbulent transfer of space charge. No such effect could be unambiguously confirmed, however, with variability in PG and air-Earth current during the eclipse being comparable to pre- and post-eclipse conditions. The already low solar radiation for this latitude, season and time of day was likely to have contributed to the reduced effect of the eclipse on atmospheric electricity through boundary layer stability. The absence of a reduction in mean PG shortly after time of maximum solar obscuration, as observed during eclipses at lower geomagnetic latitude, implied that there was no significant change in atmospheric ionization from cosmic rays above background variability. This finding was suggested to be due to the relative importance of cosmic rays of solar and galactic origin at geomagnetic mid-latitudes.This article is part of the themed issue 'Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse'. PMID:27550771

  11. Anomalous magnetotransport of a surface electron layer above liquid helium

    International Nuclear Information System (INIS)

    The magnetoconductivity σxx of a surface electron layer above liquid helium has been measured at temperatures between 0.5-1.6 K, for concentrations up to about 4x108 cm-2, in magnetic fields up to 25 kOe. As was observed, σxx first decreases with lowering temperature, then has a minimum and at T xy, the earlier ascertained anomalous behaviour of the magnetoresistance ρxx taken into consideration. The calculated dependence of ρxx on T is in satisfactory agreement with the anomalous dependence ρxx(T) found earlier by experiment

  12. Structure-phase states of the nickel surface layers after electroexplosive carburizing

    Institute of Scientific and Technical Information of China (English)

    Budovskikh; E.; A.; Bagautdinov; A.; Y.; Ivanov; Yu.; F.; Martusevich; E.; V.; Gromov; V.; E.

    2005-01-01

    The layer by layer study of the structure-phase states of the nickel surface layer carburizing with use the phenomena of the electrical explosion has conducted by the method TEM of the fine foils.……

  13. Surface treatment of a titanium implant using low temperature atmospheric pressure plasmas

    Science.gov (United States)

    Lee, Hyun-Young; Tang, Tianyu; Ok, Jung-Woo; Kim, Dong-Hyun; Lee, Ho-Jun; Lee, Hae June

    2015-09-01

    During the last two decades, atmospheric pressure plasmas(APP) are widely used in diverse fields of biomedical applications, reduction of pollutants, and surface treatment of materials. Applications of APP to titanium surface of dental implants is steadily increasing as it renders surfaces wettability and modifies the oxide layer of titanium that hinders the interaction with cells and proteins. In this study, we have treated the titanium surfaces of screw-shaped implant samples using a plasma jet which is composed of a ceramic coaxial tube of dielectrics, a stainless steel inner electrode, and a coper tube outer electrode. The plasma ignition occurred with Ar gas flow between two coaxial metal electrodes and a sinusoidal bias voltage of 3 kV with a frequency of 20 kHz. Titanium materials used in this study are screw-shaped implants of which diameter and length are 5 mm and 13 mm, respectively. Samples were mounted at a distance of 5 mm below the plasma source, and the plasma treatment time was set to 3 min. The wettability of titanium surface was measured by the moving speed of water on its surface, which is enhanced by plasma treatment. The surface roughness was also measured by atomic force microscopy. The optimal condition for wettability change is discussed.

  14. High-Resolution Properties of the Equatorial Pacific Marine Atmospheric Boundary Layer from Lidar and Radiosonde Observations.

    Science.gov (United States)

    Cooper, D. I.; Eichinger, W. E.; Barr, S.; Cottingame, W.; Hynes, M. V.; Keller, C. F.; Lebeda, C. F.; Poling, D. A.

    1996-07-01

    A `thermostat' mechanism for cooling the Equatorial pacific is being tested with data collected during the Central Equatorial Pacific Experiment. The Los Alamos National Laboratory participated by fielding two shipboard lidars that collected nearly continuous data over the Pacific from 10 to 21 March 1993 as the ship sailed from Guadalcanal to Christmas Island. A Raman lidar measured water vapor mixing ratio in the lower troposphere, especially in the marine atmospheric boundary layer (ABL), and an aerosol backscatter lidar measured height and thickness of clouds to an altitude of 20 km. The data collected from these two lidars were used to determine ocean-atmosphere phenomenology, which in turn, affects the climatology of the Central Pacific.Agreement between coincident radiosonde and the Raman water vapor lidar measurements was typically within ±0.25 g kg1 of water. Divergence between the two instruments occurred at transitions between distinct layers in the lower marine atmosphere. Reasons for this divergence will be discussed. Above the ABL the lidar and radiosonde are in excellent agreement. A wealth of detail is apparent in the lidar-derived profiles. For example, there are large variations in water vapor mixing ratio-the expression of the inherent low-frequency, intermittent, atmospheric turbulence that produces spatially discrete features such as convective plumes. These features define the structure and extent of the ABL. Using the ABL structural characteristics, an analysis of the relationship between entrainment zone (EZ) height and observed sea surface temperature (SST) revealed counterintuitive behavior-that the height of the EZ decreases as SST increases in the range between 27° and 3°C.

  15. Surface treatment of the window layer in CdS/CdTe solar cells

    International Nuclear Information System (INIS)

    CdS films are used as window layers in CdS/CdTe solar cells, and an annealing process is required to promote grain growth and recrystallization in them. However, when annealing is performed in an air atmosphere, oxides such as CdO and CdSO4 form on parts of the layer's surface, which reduces the shunt resistance and the fill factor and results in poor device performance. In this study, we annealed the CdS film in a CdCl2 atmosphere instead of air. Then, CdCl2 annealing and air annealing were compared by investigating the structural and the electrical properties of the CdS window layers. Our results reveal that the CdCl2 annealing protects the CdS film from oxidation and provides good recrystallization conditions. We also found that this CdCl2 annealing enhance the device's performance. In particular, considerably higher shunt resistance and conversion efficiency were obtained for the CdCl2-annealed device compared with the air-annealed device.

  16. Enhanced Lifetime of Polymer Solar Cells by Surface Passivation of Metal Oxide Buffer Layers.

    Science.gov (United States)

    Venkatesan, Swaminathan; Ngo, Evan; Khatiwada, Devendra; Zhang, Cheng; Qiao, Qiquan

    2015-07-29

    The role of electron selective interfaces on the performance and lifetime of polymer solar cells were compared and analyzed. Bilayer interfaces consisting of metal oxide films with cationic polymer modification namely poly ethylenimine ethoxylated (PEIE) were found to enhance device lifetime compared to bare metal oxide films when used as an electron selective cathode interface. Devices utilizing surface-modified metal oxide layers showed enhanced lifetimes, retaining up to 85% of their original efficiency when stored in ambient atmosphere for 180 days without any encapsulation. The work function and surface potential of zinc oxide (ZnO) and ZnO/PEIE interlayers were evaluated using Kelvin probe and Kelvin probe force microscopy (KPFM) respectively. Kelvin probe measurements showed a smaller reduction in work function of ZnO/PEIE films compared to bare ZnO films when aged in atmospheric conditions. KPFM measurements showed that the surface potential of the ZnO surface drastically reduces when stored in ambient air for 7 days because of surface oxidation. Surface oxidation of the interface led to a substantial decrease in the performance in aged devices. The enhancement in the lifetime of devices with a bilayer interface was correlated to the suppressed surface oxidation of the metal oxide layers. The PEIE passivated surface retained a lower Fermi level when aged, which led to lower trap-assisted recombination at the polymer-cathode interface. Further photocharge extraction by linearly increasing voltage (Photo-CELIV) measurements were performed on fresh and aged samples to evaluate the field required to extract maximum charges. Fresh devices with a bare ZnO cathode interlayer required a lower field than devices with ZnO/PEIE cathode interface. However, aged devices with ZnO required a much higher field to extract charges while aged devices with ZnO/PEIE showed a minor increase compared to the fresh devices. Results indicate that surface modification can act as a

  17. 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. PMID:26572322

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

    International Nuclear Information System (INIS)

    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

  19. Surface wave propagation characteristics in atmospheric pressure plasma column

    International Nuclear Information System (INIS)

    In the typical experiments of surface wave sustained plasma columns at atmospheric pressure the ratio of collision to wave frequency (ν/ω) is much greater than unity. Therefore, one might expect that the usual analysis of the wave dispersion relation, performed under the assumption ν/ω = 0, cannot give adequate description of the wave propagation characteristics. In order to study these characteristics we have analyzed the wave dispersion relationship for arbitrary ν/ω. Our analysis includes phase and wave dispersion curves, attenuation coefficient, and wave phase and group velocities. The numerical results show that a turning back point appears in the phase diagram, after which a region of backward wave propagation exists. The experimentally observed plasma column is only in a region where wave propagation coefficient is higher than the attenuation coefficient. At the plasma column end the electron density is much higher than that corresponding to the turning back point and the resonance

  20. Atmospheric-Pressure Plasma Cleaning of Contaminated Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Robert F. Hicks; Gary S. Selwyn

    2001-01-09

    Project was to develop a low-cost, environmentally benign technology for the decontamination and decommissioning of transuranic waste. With the invention of the atmospheric-pressure plasma jet the goal was achieved. This device selectively etches heavy 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. Studies on tantalum, a surrogate material for plutonium, have shown that etch rate of 6.0 microns per minute can be achieved under mild conditions. Over the past three years, we have made numerous improvements in the design of the plasma jet. It may now be operated for hundreds of hours and not undergo any degradation in performance. Furthermore, small compact units have been developed, which are easily deployed in the field.

  1. Surface wave propagation characteristics in atmospheric pressure plasma column

    Science.gov (United States)

    Pencheva, M.; Benova, E.; Zhelyazkov, I.

    2007-04-01

    In the typical experiments of surface wave sustained plasma columns at atmospheric pressure the ratio of collision to wave frequency (ν/ω) is much greater than unity. Therefore, one might expect that the usual analysis of the wave dispersion relation, performed under the assumption ν/ω = 0, cannot give adequate description of the wave propagation characteristics. In order to study these characteristics we have analyzed the wave dispersion relationship for arbitrary ν/ω. Our analysis includes phase and wave dispersion curves, attenuation coefficient, and wave phase and group velocities. The numerical results show that a turning back point appears in the phase diagram, after which a region of backward wave propagation exists. The experimentally observed plasma column is only in a region where wave propagation coefficient is higher than the attenuation coefficient. At the plasma column end the electron density is much higher than that corresponding to the turning back point and the resonance.

  2. Surface wave propagation characteristics in atmospheric pressure plasma column

    Energy Technology Data Exchange (ETDEWEB)

    Pencheva, M [Faculty of Physics, Sofia University, 5 James Bourchier Blvd., BG-1164 Sofia (Bulgaria); Benova, E [Department for Language Teaching and International Students, Sofia University, 27 Kosta Loulchev Street, BG-1111 Sofia (Bulgaria); Zhelyazkov, I [Faculty of Physics, Sofia University, 5 James Bourchier Blvd., BG-1164 Sofia (Bulgaria)

    2007-04-15

    In the typical experiments of surface wave sustained plasma columns at atmospheric pressure the ratio of collision to wave frequency ({nu}/{omega}) is much greater than unity. Therefore, one might expect that the usual analysis of the wave dispersion relation, performed under the assumption {nu}/{omega} = 0, cannot give adequate description of the wave propagation characteristics. In order to study these characteristics we have analyzed the wave dispersion relationship for arbitrary {nu}/{omega}. Our analysis includes phase and wave dispersion curves, attenuation coefficient, and wave phase and group velocities. The numerical results show that a turning back point appears in the phase diagram, after which a region of backward wave propagation exists. The experimentally observed plasma column is only in a region where wave propagation coefficient is higher than the attenuation coefficient. At the plasma column end the electron density is much higher than that corresponding to the turning back point and the resonance.

  3. 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.

  4. Atmospheric-Pressure Plasma Cleaning of Contaminated Surfaces

    International Nuclear Information System (INIS)

    Project was to develop a low-cost, environmentally benign technology for the decontamination and decommissioning of transuranic waste. With the invention of the atmospheric-pressure plasma jet the goal was achieved. This device selectively etches heavy 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. Studies on tantalum, a surrogate material for plutonium, have shown that etch rate of 6.0 microns per minute can be achieved under mild conditions. Over the past three years, we have made numerous improvements in the design of the plasma jet. It may now be operated for hundreds of hours and not undergo any degradation in performance. Furthermore, small compact units have been developed, which are easily deployed in the field

  5. Nonlinear Dependence of the Phase Screen Structure Function on the Atmospheric Layer Thickness

    CERN Document Server

    Mathar, Richard J

    2011-01-01

    The phase structure function accumulated by two parallel rays after transmission through a layer of turbulent air is best known by a proportionality to the 5/3rd power of the lateral distance in the aperture, derived from an isotropic Kolmogorov spectrum of the refractive index. For a von-Karman spectrum of the refractive index, a dependence involving a modified Bessel function of the ratio of the distance over the outer scale is also known. A further standard proposition is a proportionality to the path length through the atmospheric layer. The manuscript modifies this factor through a refined calculation of an integral representation of the structure function. The correction establishes a sub-linearity as the lateral distance grows in proportion to the layer thickness; it is more important for large than for small outer scales.

  6. 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.

  7. Gridded global surface ozone metrics for atmospheric chemistry model evaluation

    Directory of Open Access Journals (Sweden)

    E. D. Sofen

    2015-07-01

    Full Text Available The concentration of ozone at the Earth's surface is measured at many locations across the globe for the purposes of air quality monitoring and atmospheric chemistry research. We have brought together all publicly available surface ozone observations from online databases from the modern era to build a consistent dataset for the evaluation of chemical transport and chemistry-climate (Earth System models for projects such as the Chemistry-Climate Model Initiative and Aer-Chem-MIP. From a total dataset of approximately 6600 sites and 500 million hourly observations from 1971–2015, approximately 2200 sites and 200 million hourly observations pass screening as high-quality sites in regional background locations that are appropriate for use in global model evaluation. There is generally good data volume since the start of air quality monitoring networks in 1990 through 2013. Ozone observations are biased heavily toward North America and Europe with sparse coverage over the rest of the globe. This dataset is made available for the purposes of model evaluation as a set of gridded metrics intended to describe the distribution of ozone concentrations on monthly and annual timescales. Metrics include the moments of the distribution, percentiles, maximum daily eight-hour average (MDA8, SOMO35, AOT40, and metrics related to air quality regulatory thresholds. Gridded datasets are stored as netCDF-4 files and are available to download from the British Atmospheric Data Centre (doi:10.5285/08fbe63d-fa6d-4a7a-b952-5932e3ab0452. We provide recommendations to the ozone measurement community regarding improving metadata reporting to simplify ongoing and future efforts in working with ozone data from disparate networks in a consistent manner.

  8. Gridded global surface ozone metrics for atmospheric chemistry model evaluation

    Science.gov (United States)

    Sofen, E. D.; Bowdalo, D.; Evans, M. J.; Apadula, F.; Bonasoni, P.; Cupeiro, M.; Ellul, R.; Galbally, I. E.; Girgzdiene, R.; Luppo, S.; Mimouni, M.; Nahas, A. C.; Saliba, M.; Tørseth, K.

    2016-02-01

    The concentration of ozone at the Earth's surface is measured at many locations across the globe for the purposes of air quality monitoring and atmospheric chemistry research. We have brought together all publicly available surface ozone observations from online databases from the modern era to build a consistent data set for the evaluation of chemical transport and chemistry-climate (Earth System) models for projects such as the Chemistry-Climate Model Initiative and Aer-Chem-MIP. From a total data set of approximately 6600 sites and 500 million hourly observations from 1971-2015, approximately 2200 sites and 200 million hourly observations pass screening as high-quality sites in regionally representative locations that are appropriate for use in global model evaluation. There is generally good data volume since the start of air quality monitoring networks in 1990 through 2013. Ozone observations are biased heavily toward North America and Europe with sparse coverage over the rest of the globe. This data set is made available for the purposes of model evaluation as a set of gridded metrics intended to describe the distribution of ozone concentrations on monthly and annual timescales. Metrics include the moments of the distribution, percentiles, maximum daily 8-hour average (MDA8), sum of means over 35 ppb (daily maximum 8-h; SOMO35), accumulated ozone exposure above a threshold of 40 ppbv (AOT40), and metrics related to air quality regulatory thresholds. Gridded data sets are stored as netCDF-4 files and are available to download from the British Atmospheric Data Centre (doi: 10.5285/08fbe63d-fa6d-4a7a-b952-5932e3ab0452). We provide recommendations to the ozone measurement community regarding improving metadata reporting to simplify ongoing and future efforts in working with ozone data from disparate networks in a consistent manner.

  9. 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

  10. Plant surface reactions: an ozone defence mechanism impacting atmospheric chemistry

    Directory of Open Access Journals (Sweden)

    W. Jud

    2015-07-01

    Full Text Available Elevated tropospheric ozone concentrations are considered a toxic threat to plants, responsible for global crop losses with associated economic costs of several billion dollars per year. Plant injuries have been linked to the uptake of ozone through stomatal pores and oxidative damage of the internal leaf tissue. But a striking question remains: how much ozone effectively enters the plant through open stomata and how much is lost by chemical reactions at the plant surface? In this laboratory study we could show that semi-volatile organic compounds exuded by the glandular trichomes of different Nicotiana tabacum varieties are an efficient ozone sink at the plant surface. In our experiments, different diterpenoid compounds were responsible for a strongly variety dependent ozone uptake of plants under dark conditions, when stomatal pores are almost closed. Surface reactions of ozone were accompanied by prompt release of oxygenated volatile organic compounds, which could be linked to the corresponding precursor compounds: ozonolysis of cis-abienol (C20H34O – a diterpenoid with two exocyclic double bonds – caused emissions of formaldehyde (HCHO and methyl vinyl ketone (C4H6O. The ring-structured cembratrien-diols (C20H34O2 with three endocyclic double bonds need at least two ozonolysis steps to form volatile carbonyls such as 4-oxopentanal (C5H8O2, which we could observe in the gas phase, too. Fluid dynamic calculations were used to model ozone distribution in the diffusion limited leaf boundary layer under daylight conditions. In the case of an ozone-reactive leaf surface, ozone gradients in the vicinity of stomatal pores are changed in such a way, that ozone flux through the open stomata is strongly reduced. Our results show that unsaturated semi-volatile compounds at the plant surface should be considered as a source of oxygenated volatile organic compounds, impacting gas phase chemistry, as well as efficient ozone sink improving the ozone

  11. Application of a dynamical two-box surface-atmosphere model to the Mount Pinatubo cooling event

    CERN Document Server

    Knox, Robert S

    2008-01-01

    We analyze the global temperature change due to the Mt. Pinatubo eruption using a simple two-layer model of the atmosphere and surface to obtain results consistent with satellite data. Current highly complex models exist to model this and other temperature anomalies, but because of their complexity are not easily analyzed by those not directly involved. Through analytic and numerical analysis we find a principal characteristic response time of 5 to 8 months and a climate sensitivity of 0.17 to 0.20 C/(W/m^2), corresponding to a negative instantaneous feedback. Our solutions were fit to the data, reproducing the results of a one-box model, and providing somewhat more detailed information about the feedbacks related to surface layer temperature. The formalism for coupling of the surface layer to the thermocline is set up but not applied.

  12. Formation of gradient surface layers on high speed steel by laser surface alloying process

    Directory of Open Access Journals (Sweden)

    M. Bonek

    2012-12-01

    Full Text Available Purpose: The purpose of this research paper is focused on the high speed steel HS6-5-3-8 surface layers improvement properties using HPDL laser. The paper present laser surface technologies, investigation of structure and properties of the high speed steel alloying with the WC, VC, TiC, SiC, Si3N4 and Al2O3 particles using high power diode laser HPDL.Design/methodology/approach: Investigation indicate the influence of the alloying elements on the structure and properties of the surface layer of investigated steel depending on the kind of alloying carbides, oxides, nitrides and power implemented laser (HPDL.Findings: Laser alloying of surface layer of investigated steel without introducing alloying additions into liquid molten metal pool, in the whole range of used laser power, causes size reduction of dendritic microstructure with the direction of crystallization consistent with the direction of heat carrying away from the zone of impact of laser beam. In the effect of laser alloying with powder of the WC, VC, TiC, SiC, Si3N4and Al2O3 particles occurs size reduction of microstructure as well as dispersion hardening through fused in but partially dissolved particles and consolidation through enrichment of surface layer in alloying additions coming from dissolving elements. Introduced particles of carbides, oxides, nitrides and in part remain undissolved, creating conglomerates being a result of fusion of undissolved powder grains into molten metal base. In effect of convection movements of material in the liquid state, conglomerates of carbides arrange themselves in the characteristic of swirl. Practical implications: Laser surface modification has the important cognitive significance and gives grounds to the practical employment of these technologies for forming the surfaces of new tools and regeneration of the used ones.Originality/value: The structural mechanism was determined of surface layers development, effect was studied of alloying

  13. Water-soluble sacrificial layers for surface micromachining.

    Science.gov (United States)

    Linder, Vincent; Gates, Byron D; Ryan, Declan; Parviz, Babak A; Whitesides, George M

    2005-07-01

    This manuscript describes the use of water-soluble polymers for use as sacrificial layers in surface micromachining. Water-soluble polymers have two attractive characteristics for this application: 1) They can be deposited conveniently by spin-coating, and the solvent removed at a low temperature (95-150 degrees C), and 2) the resulting layer can be dissolved in water; no corrosive reagents or organic solvents are required. This technique is therefore compatible with a number of fragile materials, such as organic polymers, metal oxides and metals-materials that might be damaged during typical surface micromachining processes. The carboxylic acid groups of one polymer-poly(acrylic acid) (PAA)-can be transformed by reversible ion-exchange from water-soluble (Na+ counterion) to water-insoluble (Ca2+ counterion) forms. The use of PAA and dextran polymers as sacrificial materials is a useful technique for the fabrication of microstructures: Examples include metallic structures formed by the electrodeposition of nickel, and freestanding, polymeric structures formed by photolithography. PMID:17193516

  14. Plasma Nitriding of Austenitic Stainless Steel with Severe Surface Deformation Layer

    Institute of Scientific and Technical Information of China (English)

    JI Shi-jun; GAO Yu-zhou; WANG Liang; SUN Jun-cai; HEI Zu-kun

    2004-01-01

    The dc glow discharge plasma nitriding of austenite stainless steel with severe surface deformation layer is used to produce much thicker surface modified layer. This kind of layers has useful properties such as a high surface hardness of about 1500 Hv 0.1 and high resistance to frictional wear. This paper presents the structures and properties of low temperature plasma nitrided austenitic stainless steel with severe surface deformation layer.

  15. Wake Turbulence of Two NREL 5-MW Wind Turbines Immersed in a Neutral Atmospheric Boundary-Layer Flow

    CERN Document Server

    Bashioum, Jessica L; Schmitz, Sven; Duque, Earl P N

    2013-01-01

    The fluid dynamics video considers an array of two NREL 5-MW turbines separated by seven rotor diameters in a neutral atmospheric boundary layer (ABL). The neutral atmospheric boundary-layer flow data were obtained from a precursor ABL simulation using a Large-Eddy Simulation (LES) framework within OpenFOAM. The mean wind speed at hub height is 8m/s, and the surface roughness is 0.2m. The actuator line method (ALM) is used to model the wind turbine blades by means of body forces added to the momentum equation. The fluid dynamics video shows the root and tip vortices emanating from the blades from various viewpoints. The vortices become unstable and break down into large-scale turbulent structures. As the wakes of the wind turbines advect further downstream, smaller-scale turbulence is generated. It is apparent that vortices generated by the blades of the downstream wind turbine break down faster due to increased turbulence levels generated by the wake of the upstream wind turbine.

  16. 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. PMID:26552090

  17. The effect of unsteady and baroclinic forcing on predicted wind profiles in Large Eddy Simulations: Two case studies of the daytime atmospheric boundary layer

    DEFF Research Database (Denmark)

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

    2013-01-01

    and in relevant atmospheric fields (e.g. temperature) that occur at larger scales must be imposed through boundary conditions or as external forcing. In this work we study the influence of such variations on the wind profile in Large Eddy Simulations of daytime atmospheric boundary layers, by comparing....... The applied domain-scale pressure gradient and its height- and time-dependence are estimated from LIDAR measurements of the wind speed above the atmospheric boundary layer in the Høvsøre case, and from radio soundings and a network of ground-based pressure sensors in the Hamburg case. In the two case studies......-scale subsidence and advection, tend to reduce agreement with measurements, relative to the Høvsøre case. The Hamburg case illustrates that measurements of the surface pressure gradient and relatively infrequent radio soundings alone are not sufficient for accurate estimation of a height- and time...

  18. Effects of initiating anaerobic digestion of layer-hen poultry dung at sub-atmospheric pressure

    Directory of Open Access Journals (Sweden)

    Chima C. Ngumah

    2013-12-01

    Full Text Available This study investigated the effects of initiating anaerobic digestion (AD of dry layer-hen poultry dung at the sub-atmospheric pressure of -30 cmHg on biodegradation, biogasification, and biomethanation. The setup was performed as a batch process at an average ambient temperature of 29±2 0C and a retention time of 15 days. Comparisons were made with two other experiments which were both begun at ambient atmospheric pressure; one was inoculated with digestate from a previous layer-hen dung AD, while the other was not inoculated. The bioreactors initiated at sub-atmospheric pressure, ambient atmospheric pressure without inoculum, and ambient atmospheric pressure with inoculum showed the following for biogas and biomethane yields respectively: 16.8 cm3 g-1 VS and 15.46 cm3 g 1 VS, 25.10 cm3 g-1 VS and 12.85 cm3 g-1 VS, 21.44 cm3 g-1 VS and 14.88 cm3 g 1 VS. In the same order, after AD, the following values were recorded for volatile solids and total viable counts (prokaryotes and fungi in the digestates: 40.33% and 23.22 x 106 cfu mL-1, 43.42% and 22.17 x 106 cfu mL-1, 41.11% and 13.3 x 106 cfu mL-1. The feedstock showed values of 83.93% and 3.98 x 106 cfu mL-1 for volatile solids and total viable count respectively. There was a slight difference in the volatile solids of the digestates of the three bioreactors after AD. The pH recorded for the feedstock slurry before AD was 7.9 at 30oC, while after AD, the digestates from all the three bioreactors showed the same pH of 5.9 at 29 0C. Statistical analysis using ANOVA showed no significant difference in biogas yields of the feedstock for the three bioreactors (A, B, C. ANOVA showed no significant difference for biomethane yields in the bioreactors initiated at sub-atmospheric pressure and for those initiated at ambient atmospheric pressure with inoculums. However, it showed significant difference in the bioreactor initiated at sub-atmospheric pressure and that initiated at ambient atmospheric

  19. Numerical Computations of Hypersonic Boundary-Layer over Surface Irregularities

    Science.gov (United States)

    Chang, Chau-Lyan; Choudhari, Meelan M.; Li, Fei

    2010-01-01

    Surface irregularities such as protuberances inside a hypersonic boundary layer may lead to premature transition on the vehicle surface. Early transition in turn causes large localized surface heating that could damage the thermal protection system. Experimental measurements as well as numerical computations aimed at building a knowledge base for transition Reynolds numbers with respect to different protuberance sizes and locations have been actively pursued in recent years. This paper computationally investigates the unsteady wake development behind large isolated cylindrical roughness elements and the scaled wind-tunnel model of the trip used in a recent flight measurement during the reentry of space shuttle Discovery. An unstructured mesh, compressible flow solver based on the space-time conservation element, solution element (CESE) method is used to perform time-accurate Navier-Stokes calculations for the flow past a roughness element under several wind-tunnel conditions. For a cylindrical roughness element with a height to the boundary-layer thickness ratio from 0.8 to 2.5, the wake flow is characterized by a mushroom-shaped centerline streak and horse-shoe vortices. While time-accurate solutions converged to a steady-state for a ratio of 0.8, strong flow unsteadiness is present for a ratio of 1.3 and 2.5. Instability waves marked by distinct disturbance frequencies were found in the latter two cases. Both the centerline streak and the horse-shoe vortices become unstable downstream. The oscillatory vortices eventually reach an early breakdown stage for the largest roughness element. Spectral analyses in conjunction with the computed root mean square variations suggest that the source of the unsteadiness and instability waves in the wake region may be traced back to possible absolute instability in the front-side separation region.

  20. 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

  1. Evaluating the performance of the land surface model ORCHIDEE-CAN on water and energy flux estimation with a single- and a multi- layer energy budget scheme

    OpenAIRE

    Chen, Yiying; Ryder, James; Bastrikov, Vladislav; McGrath, Matthew J.; NAUDTS Kim; Otto, Juliane; Ottlé, Catherine; Peylin, Philippe; Polcher, Jan; VALADE Aude; Black, Andrew; Elbers, Jan A.; Moors, Eddy; Foken, Thomas; Gorsel, Eva van

    2016-01-01

    Canopy structure is one of the most important vegetation characteristics for land-atmosphere interactions, as it determines the energy and scalar exchanges between the land surface and the overlying air mass. In this study we evaluated the performance of a newly developed multi-layer energy budget in the land surface model ORCHIDEE-CAN (Organising Carbon and Hydrology In Dynamic Ecosystems – CANopy), which simulates canopy structure and can be coupled to an atmospheric model using an im...

  2. 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.

  3. Effect of Large Finite-Size Wind Farms and Their Wakes on Atmospheric Boundary Layer Dynamics

    Science.gov (United States)

    Wu, Ka Ling; Porté-Agel, Fernando

    2016-04-01

    Through the use of large-eddy simulation, the effect of large finite-size wind farms and their wakes on conventionally-neutral atmospheric boundary layer (ABL) dynamics and power extraction is investigated. Specifically, this study focuses on a wind farm that comprises 25 rows of wind turbines, spanning a distance of 10 km. It is shown that large wind farms have a significant effect on internal boundary layer growth both inside and downwind of the wind farms. If the wind farm is large enough, the internal boundary layer interacts with the thermally-stratified free atmosphere above, leading to a modification of the ABL height and power extraction. In addition, it is shown that large wind farms create extensive wakes, which could have an effect on potential downwind wind farms. Specifically, for the case considered here, a power deficit as large as 8% is found at a distance of 10 km downwind from the wind farm. Furthermore, this study compares the wind farm wake dynamics for cases in which the conventionally neutral ABLs are driven by a unidirectional pressure gradient and Coriolis forces.

  4. Study of Transitions in the Atmospheric Boundary Layer Using Explicit Algebraic Turbulence Models

    Science.gov (United States)

    Lazeroms, W. M. J.; Svensson, G.; Bazile, E.; Brethouwer, G.; Wallin, S.; Johansson, A. V.

    2016-08-01

    We test a recently developed engineering turbulence model, a so-called explicit algebraic Reynolds-stress (EARS) model, in the context of the atmospheric boundary layer. First of all, we consider a stable boundary layer used as the well-known first test case from the Global Energy and Water Cycle Experiment Atmospheric Boundary Layer Study (GABLS1). The model is shown to agree well with data from large-eddy simulations (LES), and this agreement is significantly better than for a standard operational scheme with a prognostic equation for turbulent kinetic energy. Furthermore, we apply the model to a case with a (idealized) diurnal cycle and make a qualitative comparison with a simpler first-order model. Some interesting features of the model are highlighted, pertaining to its stronger foundation on physical principles. In particular, the use of more prognostic equations in the model is shown to give a more realistic dynamical behaviour. This qualitative study is the first step towards a more detailed comparison, for which additional LES data are needed.

  5. Exploring the bronzing effect at the surface of ink layers

    Science.gov (United States)

    Hébert, Mathieu; Mallet, Maxime; Deboos, Alexis; Chavel, Pierre; Kuang, Deng-Feng; Hugonin, Jean-Paul; Besbes, Mondher; Cazier, Anthony

    2015-03-01

    We investigate the optical phenomenon responsible for the colored shine that sometimes appears at the surface of ink layers in the specular direction, often called bronzing or gloss differential. It seems to come from the wavelength-dependent refractive index of the ink, which induces a wavelength-dependent reflectance of the ink-air interface. Our experiments on cyan and magenta inkjet inks confirm this theory. Complex refractive indices can be obtained from measurements of the spectral reflectance and transmittance of a transparency film coated with the ink. We propose a correction of the classical Clapper-Yule model in order to include the colored gloss in the prediction of the spectral reflectance of an inked paper. We also explored effects of scattering by the micrometric or nanometric roughness of the ink surface. The micrometric roughness, easy to model with a geometrical optics model, can predict the spreading of the colored gloss over a large cone. Electromagnetic models accounting for the effect of the nanometric roughness of the surface also predict the attenuation of short wavelengths observed under collimated illumination.

  6. Some Characteristics of the Surface Boundary Layer of a Strong Cold Air Process over Southern China

    Institute of Scientific and Technical Information of China (English)

    LIU Ximing; CHENG Xueling; WU Qiong; FU Minning; ZENG Qingcun

    2013-01-01

    In southern China,cold air is a common weather process during the winter soason; it can cause strong wind,sharp temperature decreases,and even the snow or freezing rain events.However,the features of the atmospheric boundary layer during cold air passage are not clearly understood due to the lack of comprehensive observation data,especially regarding turbulence.In this study,four-layer gradient meteorological observation data and one-layer.10-Hz ultrasonic anemometer-thermometer monitoring data from the northeru side of Poyang Lake were employed to study the main features of the surface boundary layer during a strong cold-air passagc over southern China.The results show that,with the passage of a cold air front.the wind speed exhibits low-frequency variations and that the wind systematically descends.During the strong wind period,the wind speed increases with height in the surface layer.Regular gust packets arc superimposed on the basic strong wind flow.Before the passage of cold air,the wind gusts exhibit a coherent structure.The wind and turbulent momentum fluxes are small,although the gusty wind momentum flux is slightly larger than the turbulent momentum flux.However,during the invasion of cold air,both the gusty wind and turbulent momentum fluxes increase rapidly with wind speed,and the turbulent momentum flux is larger than the gusty wind momentum flux during the strong wind period.After the cold air invasion,this structure almost disappears.

  7. Electron tunneling in tantalum surface layers on niobium

    International Nuclear Information System (INIS)

    We have performed electron tunneling measurements on tantalum surface layers on niobium. The tunnel junctions comprise 2000-A-circle Nb base electrodes with 10--100-A-circle in situ--deposited Ta overlayers, an oxide barrier, and Ag, Pb, or Pb-Bi alloy counterelectrodes. The base electrodes were prepared by ion-beam sputter deposition. The characteristics of these junctions have been studied as a function of Ta-layer thickness. These include the critical current, bound-state energy, phonon structure, and oxide barrier shape. We have compared our results for the product I/sub c/R versus tantalum-layer thickness with an extended version of the Gallagher theory which accounts for both the finite mean free path in the Ta overlayers and suppression of the I/sub c/R product due to strong-coupling effects. Excellent fits to the data yield a value of the intrinsic scattering probability for electrons at the Ta/Nb interface of r2 = 0.01. This is consistent with the value expected from simple scattering off the potential step created by the difference between the Fermi energies of Ta and Nb. We have found a universal empirical correlation in average barrier height phi-bar and width s in the form phi-bar = 6 eV/(s-10 A-circle) for measured junctions which holds both for our data and results for available data in the literature for oxide-barrier junctions. The latter are composed of a wide variety of base and counterelectrode materials. These results are discussed in the general context of oxide growth and compared with results for artificial tunnel barriers

  8. 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...

  9. Thermodynamic model of hydrogen-induced silicon surface layer cleavage

    International Nuclear Information System (INIS)

    A thermodynamic model of hydrogen-induced silicon surface layer splitting with the help of a bonded silicon wafer is proposed in this article. Wafer splitting is the result of lateral growth of hydrogen blisters in the entire hydrogen-implanted region during annealing. The blister growth rate depends on the effective activation energies of both hydrogen complex dissociation and hydrogen diffusion. The hydrogen blister radius was studied as a function of annealing time, annealing temperature, and implantation dose. The critical radius was obtained according to the Griffith energy condition. The time required for wafer splitting at the cut temperature was calculated in accordance with the growth of hydrogen blisters. [copyright] 2001 American Institute of Physics

  10. Fraunhofer Lidar Prototype in the Green Spectral Region for Atmospheric Boundary Layer Observations

    Directory of Open Access Journals (Sweden)

    Songhua Wu

    2013-11-01

    Full Text Available A lidar detects atmospheric parameters by transmitting laser pulse to the atmosphere and receiving the backscattering signals from molecules and aerosol particles. Because of the small backscattering cross section, a lidar usually uses the high sensitive photomultiplier and avalanche photodiode as detector and uses photon counting technology for collection of weak backscatter signals. Photon Counting enables the capturing of extremely weak lidar return from long distance, throughout dark background, by a long time accumulation. Because of the strong solar background, the signal-to-noise ratio of lidar during daytime could be greatly restricted, especially for the lidar operating at visible wavelengths where solar background is prominent. Narrow band-pass filters must therefore be installed in order to isolate solar background noise at wavelengths close to that of the lidar receiving channel, whereas the background light in superposition with signal spectrum, limits an effective margin for signal-to-noise ratio (SNR improvement. This work describes a lidar prototype operating at the Fraunhofer lines, the invisible band of solar spectrum, to achieve photon counting under intense solar background. The photon counting lidar prototype in Fraunhofer lines devised was used to observe the atmospheric boundary layer. The SNR was improved 2-3 times by operating the lidar at the wavelength in solar dark lines. The aerosol extinctions illustrate the vertical structures of aerosol in the atmospheric boundary over Qingdao suburban during summer 2011.

  11. Cone model for two surface foundations on layered soil

    Institute of Scientific and Technical Information of China (English)

    Chen Wenhua

    2006-01-01

    In this paper, the cone model is applied to the vibration analysis of two foundations on a layered soil half space. In the analysis, the total stress field in the subsoil is divided into the free-field and the scattering field. Seed's simplified method is adopted for the free-field analysis,while the cone model is proposed for analyzing the dynamic scattering stress wave field.The shear stress field and the compressive stress field in the layered stratum with two scattering sources are calculated by shear cone and compressive cone, respectively. Furthermore, the stress fields in the subsoil with two foundations are divided into six zones, and the P wave and S wave are analyzed in each zone. Numerical results are provided to illustrate features of the added stress field for two surface foundations under vertical and horizontal sinusoidal force excitation. The proposed cone model may be useful in handling some of the complex problems associated with multi-scattering sources.

  12. Influences of the boundary layer evolution on surface ozone variations at a tropical rural site in India

    Indian Academy of Sciences (India)

    K K Reddy; M Naja; N Ojha; P Mahesh; S Lal

    2012-08-01

    Collocated measurements of the boundary layer evolution and surface ozone, made for the first time at a tropical rural site (Gadanki 13.5°N, 79.2°E, 375 m amsl) in India, are presented here. The boundary layer related observations were made utilizing a lower atmospheric wind profiler and surface ozone observations were made using a UV analyzer simultaneously in April month. Daytime average boundary layer height varied from 1.5 km (on a rainy day) to a maximum of 2.5 km (on a sunny day). Correlated day-to-day variability in the daytime boundary layer height and ozone mixing ratios is observed. Days of higher ozone mixing ratios are associated with the higher boundary layer height and vice versa. It is shown that higher height of the boundary layer can lead to the mixing of near surface air with the ozone rich air aloft, resulting in the observed enhancements in surface ozone. A chemical box model simulation indicates about 17% reduction in the daytime ozone levels during the conditions of suppressed PBL in comparison with those of higher PBL conditions. On a few occasions, substantially elevated ozone levels (as high as 90 ppbv) were observed during late evening hours, when photochemistry is not intense. These events are shown to be due to southwesterly wind with uplifting and northeasterly winds with downward motions bringing ozone rich air from nearby urban centers. This was further corroborated by backward trajectory simulations.

  13. Controlling the surface termination of NdGaO3 (110): the role of the gas atmosphere

    Science.gov (United States)

    Cavallaro, Andrea; Harrington, George F.; Skinner, Stephen J.; Kilner, John A.

    2014-06-01

    In this work the effect of gas atmosphere on the surface termination reconstruction of single crystal NdGaO3 (110) (NGO) during thermal annealing was analyzed. Using Low Energy Ion Scattering (LEIS) it has been possible to study the chemical composition of the first atomic layer of treated NGO single crystal samples. NGO has been analyzed both as-received and after a specific thermal treatment at 1000 °C under different gas fluxes (argon, nitrogen, static air, synthetic air, nitrogen plus 5% hydrogen and wet synthetic air respectively). Thermal annealing of perovskite single crystals, as already reported in the literature, is used to obtain a fully A-cation surface termination. Nevertheless the effect of the gas-atmosphere on this process has not been previously reported. By the use of sequential low energy Ar+ sputtering combined with the primary ion LEIS analysis, the reconstruction of the outermost atomic layers has allowed the clarification of the mechanism of NGO neodymium surface enrichment. It is proposed that the gallium at the surface is submitted to a reduction/evaporation mechanism caused by low oxygen partial pressure and/or high water pressure in the vector gas. Below the first surface atomic layers of an as-received NGO single-crystal a gallium-rich phase has also been observed.

  14. Observations of high rates of NO2 – HONO conversion in the nocturnal atmospheric boundary layer in Kathmandu, Nepal

    Directory of Open Access Journals (Sweden)

    R. Prinn

    2009-01-01

    Full Text Available Nitrous acid (HONO plays a significant role in the atmosphere, especially in the polluted troposphere. Its photolysis after sunrise is an important source of hydroxyl free radicals (OH. Measurements of nitrous acid and other pollutants were carried out in the Kathmandu urban atmosphere during January–February 2003, contributing to the sparse knowledge of nitrous acid in South Asia. The results showed average nocturnal levels of HONO (1.7±0.8 ppbv, NO2 (17.9±10.2 ppbv, and PM10 (0.18±0.11 mg m−3 in urban air in Kathmandu. Surprisingly high ratios of chemically formed secondary [HONO] to [NO2] (up to 30% were found, which indicates unexpectedly efficient chemical conversion of NO2 to HONO in Kathmandu. The ratios of [HONO]/[NO2] at nights are much higher than previously reported values from measurements in urban air in Europe, North America and Asia. The influence of aerosol plumes, relative humidity, aerosol surface and ground reactive surface, temperature on NO2-HONO chemical conversion were discussed. The high humidity, strong and low inversion layer at night, and serious aerosol pollution burden may explain the particularly efficient conversion of NO2 to HONO.

  15. Atmospheric pressure spatial atomic layer deposition web coating with in situ monitoring of film thickness

    International Nuclear Information System (INIS)

    Spectral reflectometry was implemented as a method for in situ thickness monitoring in a spatial atomic layer deposition (ALD) system. Al2O3 films were grown on a moving polymer web substrate at 100 °C using an atmospheric pressure ALD web coating system, with film growth of 0.11–0.13 nm/cycle. The modular coating head design and the in situ monitoring allowed for the characterization and optimization of the trimethylaluminum and water precursor exposures, purge flows, and web speed. A thickness uniformity of ±2% was achieved across the web. ALD cycle times as low as 76 ms were demonstrated with a web speed of 1 m/s and a vertical gap height of 0.5 mm. This atmospheric pressure ALD system with in situ process control demonstrates the feasibility of low-cost, high throughput roll-to-roll ALD

  16. Influence of annealing in H atmosphere on the electrical properties of Al2O3 layers grown on p-type Si by the atomic layer deposition technique

    Science.gov (United States)

    Kolkovsky, Vl.; Stübner, R.; Langa, S.; Wende, U.; Kaiser, B.; Conrad, H.; Schenk, H.

    2016-09-01

    In the present study the electrical properties of 100 nm and 400 nm alumina films grown by the atomic layer deposition technique on p-type Si before and after a post-deposition annealing at 440 °C and after a dc H plasma treatment at different temperatures are investigated. We show that the density of interface states is below 2 × 1010 cm-2 in these samples and this value is significantly lower compared to that reported previously in thinner alumina layers (below 50 nm). The effective minority carrier lifetime τg,eff and the effective surface recombination velocity seff in untreated p-type Si samples with 100 nm and 400 nm aluminum oxide is comparable with those obtained after thermal oxidation of 90 nm SiO2. Both, a post-deposition annealing in forming gas (nitrogen/hydrogen) at elevated temperatures and a dc H-plasma treatment at temperatures close to room temperature lead to the introduction of negatively charged defects in alumina films. The results obtained in samples annealed in different atmospheres at different temperatures or subjected to a dc H plasma treatment allow us to correlate these centers with H-related defects. By comparing with theory we tentatively assign them to negatively charged interstitial H atoms.

  17. Surface modification of polyimide (PI) film using water cathode atmospheric pressure glow discharge plasma

    Science.gov (United States)

    Zheng, Peichao; Liu, Keming; Wang, Jinmei; Dai, Yu; Yu, Bin; Zhou, Xianju; Hao, Honggang; Luo, Yuan

    2012-10-01

    The industrial use of polyimide film is limited because of undesirable properties such as poor wettability. In the present paper, a new kind of equipment called water cathode atmospheric pressure glow discharge was used to improve the surface properties of polyimide films and made them useful to technical applications. The changes in hydrophilicity of modified polyimide film surfaces were investigated by contact angle, surface energy and water content measurements as a function of treatment time. The results obtained show good treatment homogeneity and that the variation trends of contact angles are different for polar and non-polar testing liquids, while surface energy and water content are significantly enhanced with the increase of treatment time until they achieve saturated values after 60 s plasma treatment. Also, the thickness of liquid layer plays an important role in plasma processing and directly affects the treatment effect. Changes in morphology of polyimide films were analyzed by atomic force microscope and the results indicate that surface hydrophilicity after plasma treatment are improved partly due to the increase in the roughness. In addition, polyimide films treated by plasma are subjected to an ageing process to determine the durability of plasma treatment. It is found that the hydrophilicity is still better than untreated ones though the hydrophobic character partly recovers after long-term storage in ambient air.

  18. The atmospheric boundary layer evening transitions: an observational and numerical study from two different datasets

    Science.gov (United States)

    Sastre, Mariano; Yagüe, Carlos; Román-Cascón, Carlos; Maqueda, Gregorio; Ander Arrillaga, Jon

    2015-04-01

    In this work we study the temporal evolution of the Atmospheric Boundary Layer (ABL) along the transition period from a diurnal typical convection to a nocturnal more frequently stable situation. This period is known as late afternoon or evening transition, depending on the specific definitions employed by different authors [1]. In order to obtain a proper characterization, we try to learn whether or not the behaviour of these transitional boundary layers is strongly dependent on local conditions. To do so, two sets of evening transitions are studied from data collected at two different experimental sites. These locations correspond to research facilities named CIBA (Spain) and CRA (France), which are the places where atmospheric field campaigns have been conducted during the last years, such as CIBA2008 and BLLAST 2011, respectively. In order to get comparable situations, we focus especially on transitions with weak synoptic forcing, and consider daily astronomical sunset as a reference time. A statistical analysis on main parameters related to the transition is carried out for both locations, and the average behaviour is shown as well as extreme values according to the timing. A similar pattern in the qualitative evolution of many variables is found. Nevertheless, several relevant differences in the progress of key variables are obtained too. Moisture, both from the soil and the air, is thought to have great relevance in explaining many of the differences found between the two sites. Some case studies are explored, focusing on the role played by the atmospheric turbulence. Complementary, numerical experiments are also performed using the Weather Research and Forecast (WRF) mesoscale model, in order to test the role of humidity, by artificially varying it in some of the simulations. [1] Lothon, M. and coauthors (2014): The BLLAST field experiment: Boundary-Layer Late Afternoon and Sunset Turbulence. Atmos. Chem. Phys., 14, 10931-10960.

  19. A modified surface-resistance approach for representing bare-soil evaporation: wind tunnel experiments under various atmospheric conditions

    International Nuclear Information System (INIS)

    A physically based (i.e., nonempirical) representation of surface-moisture availability is proposed, and its applicability is investigated. This method is based on the surface-resistance approaches, and it uses the depth of evaporating surface rather than the water content of the surface soil as the determining factor of surface-moisture availability. A simple energy-balance model including this representation is developed and tested against wind tunnel experiments under various atmospheric conditions. This model can estimate not only the latent heat flux but also the depth of the evaporating surface simultaneously by solving the inverse problem of energy balance at both the soil surface and the evaporating surface. It was found that the depth of the evaporating surface and the latent heat flux estimated by the model agreed well with those observed. The agreements were commonly found out under different atmospheric conditions. The only limitation of this representation is that it is not valid under conditions of drastic change in the radiation input, owing to the influence of transient phase transition of water in the dry surface layer. The main advantage of the approach proposed is that it can determine the surface moisture availability on the basis of the basic properties of soils instead of empirical fitting, although further investigations on its practical use are needed

  20. Variation of 222Rn concentration in outdoor air due to variation of the atmospheric boundary layer

    International Nuclear Information System (INIS)

    Variation of 222Rn concentration in outdoor air, returns of a monostatic acoustic sounder and sensible heat flux are simultaneously observed at Okayama-shi in Japan. The sensible heat flux is measured with an eddy correlation method using a sonic anemometer and a copper-constantan thermocouple thermometer. Using height of a surface-based inversion layer obtained by the acoustic sounder returns and two 222Rn concentrations during the presence of the surface-based inversion layer, the exhalation rate of 222Rn at this site is estimated to be about 0.01 Bq.m-2.s-1, which agrees well within the exhalation rate of 222Rn estimated at Nagoya-shi in Japan. Using the estimated exhalation rates of 222Rn and the variation of the 222Rn concentration in the daytime, heights of mixing layers are estimated. These heights of the mixing layers are larger than the height of the mixing layer estimated using the sensible heat flux and the representative vertical profile of the autumnal night time air temperature in this area. (author)

  1. Using an artificial neural network approach to estimate surface-layer optical turbulence at Mauna Loa, Hawaii.

    Science.gov (United States)

    Wang, Yao; Basu, Sukanta

    2016-05-15

    In this Letter, an artificial neural network (ANN) approach is proposed for the estimation of optical turbulence (Cn2) in the atmospheric surface layer. Five routinely available meteorological variables are used as the inputs. Observed Cn2 data near the Mauna Loa Observatory, Hawaii are utilized for validation. The proposed approach has demonstrated its prowess by capturing the temporal evolution of Cn2 remarkably well. More interestingly, this ANN approach is found to outperform a widely used similarity theory-based conventional formulation for all the prevalent atmospheric conditions (including strongly stratified conditions). PMID:27176996

  2. Simulation of impact assesment of crown forest fires on boudary layer of atmosphere using software PHOENICS

    Science.gov (United States)

    Soprunenko, Elina E.; Perminov, Valeriy; Reyno, Vladimir V.; Loboda, Egor L.

    2015-11-01

    Mathematical model of heat and mass transfer of crown forest fire is used in this paper, which is developed on the base of experimental research data and laws and methods of mechanics of reacting media. The numerical calculation carried out using software PHOENICS for non stationary three dimensional case. K-Ɛ model of turbulence is taken into account. It is studied the influence of temperature and wind velocity in boundary layer of atmosphere on the turbulent kinematic viscosity coefficient value and distribution of temperature above the crown forest fire front.

  3. Atmospheric Boundary Layer Height Evolution with Lidar in Buenos Aires from 2008 to 2011

    Science.gov (United States)

    Pawelko, Ezequiel Eduardo; Salvador, Jacobo Omar; Ristori, Pablo Roberto; Pallotta, Juan Vicente; Otero, Lidia Ana; Quel, Eduardo Jaime

    2016-06-01

    The analysis of the atmospheric boundary layer top height evolution is obtained from 2008 to 2011 in Buenos Aires using the multiwavelength lidar located at CEILAP (CITEDEF-CONICET) (34°33' S; 58°30' W; 17 m asl). Algorithms recognition based on covariance wavelet transform are applied to obtain seasonal statistics. This method is being evaluated for use in the Lidar Network in Argentina and it is being deployed in Patagonia region currently. The technique operates in real time in both low and high aerosol loads and with almost no human supervision.

  4. Numerical Solution of 2D and 3D Atmospheric Boundary Layer Stratified Flows

    Czech Academy of Sciences Publication Activity Database

    Šimonek, J.; Kozel, K.; Jaňour, Zbyněk

    Berlín : Springer, 2011 - (Fořt, J.; Fürst, J.; Halama, J.; Herbin, R.; Hubert, R.), s. 723-730 ISBN 978-3-642-20670-2. [FVCA Internationa Symposium /6./. Praha (CZ), 06.06.2011-10.6.2011] Institutional research plan: CEZ:AV0Z20760514 Keywords : CFD * finite volume method * variable density flows * atmospheric boundary layer flows Subject RIV: BK - Fluid Dynamics http://www.springerlink.com/content/p7r28m682x638510

  5. Validation of the simpleFoam (RANS) solver for the atmospheric boundary layer in complex terrain

    OpenAIRE

    Peralta C.; Nugusse H.; Kokilavani S.P.; Schmidt J.; Stoevesandt B.

    2014-01-01

    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 bl...

  6. The Oblique Incident Effects of Electromagnetic Wave in Atmospheric Pressure Plasma Layers

    Institute of Scientific and Technical Information of China (English)

    HE Yong; JIANG Zhonghe; HU Xiwei; LIU Minghai

    2008-01-01

    The propagating behaviours, i.e. phase shift, transmissivity, reflectivity and absorptivity, of an electromagnetic (EM) wave in a two-dimensional atmospheric pressure plasma layer are described by the numerical solutions of integral-differential Maxwell's equations through a generalized finite-difference-time-domain (FDTD) algorithm. These propagating behaviours are found to be strongly affected by five factors: two EM wave characteristics relevan.t to the oblique incident and three dimensionless factors. The two EM wave factors are the polarization mode (TM mode or TE mode) and its incident angle. The three dimensionless factors are: the ratio of the maximum electron density to the critical density n0/ncr, the ratio of the plasma layer width to the wave length d/λ, and the ratio of the collision frequency between electrons and neutrals to the incident wave frequency ve0/f.

  7. The viscous boundary layer at the free surface of a rotating baroclinic fluid

    OpenAIRE

    Hide, R.

    2011-01-01

    The properties of the viscous boundary layer at the free surface of a rotating baroclinic fluid are analyzed and compared with those of the well-known Ekman boundary layer at a rigid surface. Although the ageostrophic components of the flow in the free surface boundary layer are weaker than in the Ekman layer, there are problems of practical interest in which their effects are not negligible.DOI: 10.1111/j.2153-3490.1964.tb00188.x

  8. 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

  9. Immobilization of gold nanoparticles on a polycarbonate surface layer during molding

    International Nuclear Information System (INIS)

    Highlights: → A new nanoparticle layer system is constructed. → Nanoparticles are transferred to a thermoplastic surface during a molding step. → The nanoparticles are permanently embedded in the outermost surface layer. → Applications are selective heating for chemical reactions or physical processes. - Abstract: A gold nanoparticle layer on a substrate is deposited by electrostatic deposition from a colloidal solution. This layer is transferred to the surface of a polycarbonate sheet by molding. Our investigations reveal that the nanoparticles are almost completely transferred. A random distribution over the surface is found, which is almost equivalent to that on the substrate surface. The particles are embedded into the outermost surface layer of polycarbonate and covered by a polycarbonate layer of about 5 nm in thickness. This ensures an effective immobilization of the particles. Such a layer may be used for applications where, for example, a selective surface activation by irradiation is desired.

  10. On the role of atmosphere-ocean interactions in the expected long-term changes of the Earth's ozone layer caused by greenhouse gases

    Science.gov (United States)

    Zadorozhny, Alexander; Dyominov, Igor

    It is well known that anthropogenic emissions of greenhouse gases into the atmosphere produce a global warming of the troposphere and a global cooling of the stratosphere. The expected stratospheric cooling essentially influences the ozone layer via increased polar stratospheric cloud formation and via temperature dependences of the gas phase reaction rates. One more mechanism of how greenhouse gases influences the ozone layer is enhanced water evaporation from the oceans into the atmosphere because of increasing temperatures of the ocean surface due to greenhouse effect. The subject of this paper is a study of the influence of anthropogenic pollution of the atmosphere by the greenhouse gases CO2, CH4, N2O and ozone-depleting chlorine and bromine compounds on the expected long-term changes of the ozone layer with taking into account an increase of water vapour content in the atmosphere due to greenhouse effect. The study based on 2-D zonally averaged interactive dynamical radiative-photochemical model of the troposphere and stratosphere. The model allows to self-consistently calculating diabatic circulation, temperature, gaseous composition of the troposphere and stratosphere at latitudes from the South to North Poles, as well as distribution of sulphate aerosol particles and polar stratospheric clouds of two types. It was supposed in the model that an increase of the ocean surface temperature caused by greenhouse effect is similar to calculated increase of atmospheric surface temperature. Evaporation rate from the ocean surface was computed in dependence of latitude. The model time-dependent runs were made for the period from 1975 to 2100 using two IPCC scenarios depicting maximum and average expected increases of greenhouse gases in the atmosphere. The model calculations show that anthropogenic increasing of water vapour abundance in the atmosphere due to heating of the ocean surface caused by greenhouse effect gives a sensible contribution to the expected ozone

  11. Turbulent boundary layer over a convergent and divergent superhydrophobic surface

    Science.gov (United States)

    Nadeem, Muhammad; Hwang, Jinyul; Sung, Hyung Jin

    2015-11-01

    Direct numerical simulation (DNS) of spatially developing turbulent boundary layer (TBL) over a convergent and divergent superhydrophobic surface (SHS) was performed. The convergent and divergent SHS was aligned in the streamwise direction. The SHS was modeled as a pattern of slip and no-slip surfaces. For comparison, DNS of TBL over a straight SHS was also carried out. The momentum thickness Reynolds number was varied from 800 to 1400. The gas fraction of the convergent and divergent SHS was the same as that of the straight SHS, keeping the slip area constant. The slip velocity in the convergent SHS was higher than that of the straight SHS. An optimal streamwise length of the convergent and divergent SHS was obtained. The convergent and divergent SHS gave more drag reduction than the straight SHS. The convergent and divergent SHS led to the modification of near wall-turbulent structures, resembling the narrowing and widening streaky structures near the wall. The convergent and divergent SHS had a relatively larger damping effect on near-wall turbulence than the straight SHS. These observations will be further analyzed statistically to demonstrate the effect of the convergent and divergent SHS on the interaction of inner and outer regions of TBL.

  12. Thin hydroxyapatite surface layers on titanium produced by ion implantation

    International Nuclear Information System (INIS)

    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 (α,α) backscattering and the resonant nuclear reaction 1H(15N,αγ)12C. 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 marrow bone cells on the implanted sample surface with that of titanium

  13. UAS and DTS: Using Drones and Fiber Optics to Measure High Resolution Temperature of the Atmospheric Boundary Layer

    Science.gov (United States)

    Predosa, R. A.; Darricau, B.; Higgins, C. W.

    2015-12-01

    The atmospheric boundary layer (ABL) is the lowest part of the atmosphere that directly interacts with the planet's surface. The development of the ABL plays a vital role, as it affects the transport of atmospheric constituents such as air pollutants, water vapor, and greenhouse gases. Measurements of the processes in the ABL have been difficult due to the limitations in the spatial and temporal resolutions of the equipment as well as the height of the traditional flux tower. Recent advances in the unmanned aerial vehicle (UAV) and distributed temperature sensing (DTS) technologies have provided us with new tools to study the complex processes in ABL. We conducted a series of pioneering experiments in Eastern Oregon using a platform that combines UAV and DTS to collect data during morning and evening transitions in the ABL. The major components of this platform consists of a quad-copter, a DTS computer unit, and a set of customized fiber optic cables. A total of 75 flights were completed to investigate: (1) the capability of a duplexed fiber optic cable to reduce noise in the high spatial and temporal temperature measurements taken during the morning transition; (2) the possibility of using fiber optic cable as "wet bulb" thermometer to calculate relative humidity in the ABL at high spatial and temporal resolution. The preliminary results showed that using a fiber optic cable in a duplexed configuration with the UAV-DTS platform can effectively reduce noise level during the morning transition data collection. The customized "wet bulb" fiber optic cable is capable of providing information for the calculation of relative humidity in the ABL at unprecedented spatial and temporal resolutions. From this study, the UAV-DTS platform demonstrated great potential in collecting temperature data in the ABL and with the development of atmospheric sensor technologies, it will have more applications in the future.

  14. Emanation thermal analysis for characterization of surface and near surface layers of advanced materials

    International Nuclear Information System (INIS)

    A non traditional method, called emanation thermal analysis (ETA), was used the for characterization of surface and near surface layers of SiC based materials. This method consists in the measurement of the release of inert gas (radon) from the samples previously labeled to the depth of several tens of nanometers with the inert gas atoms. The ETA results brought about information about microstructure changes and transport properties of SiC/SiCf composites on heating in the range 30-1300degC in argon and air, respectively. The annealing of structure irregularities which served as diffusion paths for radon was evaluated. The temperature range of the formation and crystallization of the silica layer resulting after oxidation of the SiC/SiCf sample on heating in air was determined from the ETA results. (author)

  15. Effect of treatment time on characterization and properties of nanocrystalline surface layer in copper induced by surface mechanical attrition treatment

    Indian Academy of Sciences (India)

    Farzad Kargar; M Laleh; T Shahrabi; A Sabour Rouhaghdam

    2014-08-01

    Nanocrystalline surface layers were synthesized on pure copper by means of surface mechanical attrition treatment (SMAT) at various treatment times. The microstructural features of the surface layers produced by SMAT were systematically characterized by optical microscopy (OM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis. Hardness and surface roughness measurements were also carried out. It is found that the thickness of the deformed layer increased from 50 to 500 m with increasing treatment time from 10 to 300 min, while the average grain size of the top surface layer decreased from 20 to 7 nm. Hardness of the all SMATed samples decreased with depth. Furthermore, the hardness of the top surface layer of the SMATed samples was at least two times higher than that of the un-treated counterpart. Surface roughness results showed different trend with treatment time. Amounts of PV and a values first sharply increased and then decreased.

  16. The Effect of Surface Ice and Topography on the Atmospheric Circulation and Distribution of Nitrogen Ice on Pluto.

    Science.gov (United States)

    Rafkin, Scot; Soto, Alejandro; Michaels, Timothy

    2016-04-01

    A newly developed general circulation model (GCM) for Pluto is used to investigate the unexpected and highly heterogeneous distribution of nitrogen surface ice imaged by the New Horizons spacecraft on the surface of Pluto. The GCM is based on the GFDL Flexible Modeling System (FMS) dynamical core, solved on a discretized latitude/longitude horizontal grid and a pressure-based hybrid vertical coordinate. Model physics include a 3-band radiative scheme, molecular thermal conduction within the atmosphere, subsurface thermal conduction, and a nitrogen volatile cycle. The radiative-conductive model takes into account the 2.3, 3.3 and 7.8 μm bands of CH4, including non-local thermodynamic equilibrium effects. The subsurface conduction model assumes a water ice regolith. In the case of nitrogen surface ice deposition, additional super-surface layers are added above the water ice regolith to properly account for conductive energy flow through the nitrogen ice. The nitrogen volatile cycle is based on a vapor pressure equilibrium assumption between the atmosphere and surface. Prior to the arrival of the New Horizons spacecraft, the expectation was that the volatile surface ice distribution on the surface of Pluto would be strongly controlled by the latitudinal temperature gradient resulting primarily from the slow seasonal variations of radiative-conductive equilibrium. If this were the case, then Pluto would have broad latitudinal bands of both ice covered surface and ice free surface, as dictated by the season. Furthermore, the circulation, and thus the transport of volatiles, was thought to be driven almost exclusively by sublimation and deposition flows (so-called "condensation flows") associated with the volatile cycle. In contrast to expectations, images from New Horizon showed an extremely complex, heterogeneous distribution of surface ices draped over topography of substantial geologic diversity. To maintain such an ice distribution, the atmospheric circulation and

  17. Study on the atmospheric boundary layer and its influence on regional air quality over the Pearl River delta

    Directory of Open Access Journals (Sweden)

    M. Wu

    2013-03-01

    Full Text Available To study the structure of atmospheric boundary layer (ABL and its influence on regional air quality over the Pearl River delta (PRD, two ABL intensive observations were conducted at Panyu (urban station and Xinken (non-urban station, near estuary of PRD during October 2004 and July 2006, respectively. Based on the ABL intensive observation data analysis, the typical weather condition type associated with poor air quality over PRD could be summarized into two kinds: the warmed period before cold front (WPBCF and the subsidence period controlled by tropical cyclone (SPCTC. Two typical polluted cases (affected by WPBCF and SPCTC, respectively and one clean (not-polluted case were chosen for detail analysis. It was found that the continuously low or calm ground wind would lead to pollutant accumulation. The local circulation, such as sea–land breezes and heat–island circulation, played an important role in these polluted cases. The recirculation was significant in polluted cases; steady transport occurred in the clean case. Ventilation index (VI was quite different between polluted cases and the clean case: in WPBCF cases, the peak VI was from 184 to 3555 m2 s−1; on SPCTC days, the peak VI was from 1066 to 4363 m2 s−1; on the clean day, the peak VI was 10 885 m2 s−1 and much larger than all polluted cases. The 24-h average VI on polluted days was from 169 to 2858 m2 s−1 and also much smaller than that of the clean day. VI is a good reference index for pollution judgment. The peak mixing heights were smaller than 700 m in WPBCF cases, and were smaller than 800 m in SPCTC cases. During WPBCF polluted case, only surface inversion layer appeared. In the period of land breeze, surface inversion layer height was about 50 m, but in the period of sea breeze, surface inversion layer height would increase, and reach the maximum height, which was about 600 m. During SPCTC polluted case, there were several inversion layers that appeared at different

  18. Investigation of surface layer on rolled recycled AA5050 in relation to Filiform Corrosion

    OpenAIRE

    Premendra

    2007-01-01

    The presence of a heavily deformed surface layer (a few microns thick) on rolled aluminium alloy is understood to be one of the main reasons contributing to the Filiform Corrosion (FFC) susceptibility of the alloy. The surface layer is formed during the thermo-mechanical processing of the sheet metal, in the rolling mills. The surface layer characteristics are process dependent, i.e. depends on thermo-mechanical processing and the composition of the alloy in addition to post-production surfac...

  19. Laboratory Simulations of Local Winds in the Atmospheric Boundary Layer via Image Analysis

    Directory of Open Access Journals (Sweden)

    Monica Moroni

    2015-01-01

    Full Text Available In the atmospheric boundary layer, under high pressure conditions and negligible geostrophic winds, problems associated with pollution are the most critical. In this situation local winds play a major role in the evaluation of the atmospheric dynamics at small scales and in dispersion processes. These winds originate as a result of nonuniform heating of the soil, either when it is homogeneous or in discontinuous terrain in the presence of sea and/or slopes. Depending on the source of the thermal gradient, local winds are classified into convective boundary layer, sea and land breezes, urban heat islands, and slope currents. Local winds have been analyzed by (i simple analytical models; (ii numerical models; (iii field measurements; (iv laboratory measurements through which it is impossible to completely create the necessary similarities, but the parameters that determine the phenomenon can be controlled and each single wind can be separately analyzed. The present paper presents a summary of laboratory simulations of local winds neglecting synoptic winds and the effects of Coriolis force. Image analysis techniques appear suitable to fully describe both the individual phenomenon and the superposition of more than one local wind. Results do agree with other laboratory studies and numerical experiments.

  20. Characterization of oxide layers of heat-resisting alloys in oxidizing and oxidizing/sulfidizing atmospheres by deuterium permeation measurement

    International Nuclear Information System (INIS)

    Deuterium permeation measurements are suitable to characterize the integrity of layers, which are preoxidized or in-situ oxidized on high temperature alloys. The permeation through metal alloys with a growing oxidized layer is described by a model with a time dependence of the permeation flux related to the growth of the oxide layer. The behaviour of the layers, which are oxidized at different oxidizing atmospheres, are investigated in this work. By permeation test, parabolic rate constants, impeding factors, as well as permeability, diffusivity and the solubility of deuterium for the oxide layers are obtained. The measurement are continued in sulfidizing atmosphere for testing such layers as corrosion barrier. In correlation with microstructural post examinations it is found that permeation measurement can be utilized as a method for investigating high-temperature corrosion. (orig.)