Science.gov

Sample records for neutral atmospheric boundary

  1. Turbulent flux events in a nearly neutral atmospheric boundary layer.

    PubMed

    Narasimha, Roddam; Kumar, S Rudra; Prabhu, A; Kailas, S V

    2007-03-15

    We propose here a novel method of analysing turbulent momentum flux signals. The data for the analysis come from a nearly neutral atmospheric boundary layer and are taken at a height of 4m above ground corresponding to 1.1 x 10(5) wall units, within the log layer for the mean velocity. The method of analysis involves examining the instantaneous flux profiles that exceed a given threshold, for which an optimum value is found to be 1 s.d. of the flux signal. It is found feasible to identify normalized flux variation signatures separately for positive and negative 'flux events'-the sign being determined by that of the flux itself. Using these signatures, the flux signal is transformed to one of events characterized by the time of occurrence, duration and intensity. It is also found that both the average duration and the average time-interval between successive events are of order 1s, about four orders of magnitude higher than a wall unit in time. This episodic description of the turbulence flux in the time domain enables us to identify separately productive, counter-productive and idle periods (accounting, respectively, for 36, 15 and 49% of the time), taking as criterion the generation of the momentum flux. A 'burstiness' index of 0.72 is found for the data. Comparison with laboratory data indicates higher (/lower) ejection (/sweep) quadrant occupancy but lower (/higher) contributions to flux from the ejection (/sweep) quadrant at the high Reynolds numbers of the atmospheric boundary layer. Possible connections with the concept of active and passive motion in a turbulent boundary layer are briefly discussed.

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

    NASA Astrophysics Data System (ADS)

    Jacob, Chinthaka; Anderson, William

    2017-01-01

    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.

  3. Large eddy simulation of a large wind-turbine array in a conventionally neutral atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Allaerts, Dries; Meyers, Johan

    2015-06-01

    Under conventionally neutral conditions, the boundary layer is frequently capped by an inversion layer, which counteracts vertical entrainment of kinetic energy. Very large wind farms are known to depend on vertical entrainment to transport energy from above the farm towards the turbines. In this study, large eddy simulations of an infinite wind-turbine array in a conventionally neutral atmospheric boundary layer are performed. By carefully selecting the initial potential-temperature profile, the influence of the height and the strength of a capping inversion on the power output of a wind farm is investigated. Results indicate that both the height and the strength have a significant effect on the boundary layer flow, and that the height of the neutral boundary layer is effectively controlled by the capping inversion. In addition, it is shown that the vertical entrainment rate decreases for increasing inversion strength or height. In our infinite wind-farm simulations, varying the inversion characteristics leads to differences in power extraction on the order of 13% ± 0.2% (for increasing the strength from 2.5 to 10 K), and 31% ± 0.4% (for increasing the height from 500 to 1500 m). A detailed analysis of the mean kinetic-energy equation is included, showing that the variation in power extraction originates from the work done by the driving pressure gradient related to the boundary layer height and the geostrophic angle, while entrainment of kinetic energy from the free atmosphere does not play a significant role. Also, the effect of inversion strength on power extraction is energetically not related to different amounts of energy entrained, but explained by a difference in boundary layer growth, leading to higher boundary layers for lower inversion strengths. We further present a simple analytical model that allows to obtain wind-farm power output and driving power for the fully developed regime as function of Rossby number and boundary layer height.

  4. A Comprehensive Modelling Approach for the Neutral Atmospheric Boundary Layer: Consistent Inflow Conditions, Wall Function and Turbulence Model

    NASA Astrophysics Data System (ADS)

    Parente, Alessandro; Gorlé, Catherine; van Beeck, Jeroen; Benocci, Carlo

    2011-09-01

    We report on a novel approach for the Reynolds-averaged Navier-Stokes (RANS) modelling of the neutral atmospheric boundary layer (ABL), using the standard k-{\\varepsilon} turbulence model. A new inlet condition for turbulent kinetic energy is analytically derived from the solution of the k-{\\varepsilon} model transport equations, resulting in a consistent set of fully developed inlet conditions for the neutral ABL. A modification of the standard k-{\\varepsilon} model is also employed to ensure consistency between the inlet conditions and the turbulence model. In particular, the turbulence model constant C μ is generalized as a location-dependent parameter, and a source term is introduced in the transport equation for the turbulent dissipation rate. The application of the proposed methodology to cases involving obstacles in the flow is made possible through the implementation of an algorithm, which automatically switches the turbulence model formulation when going from the region where the ABL is undisturbed to the region directly affected by the building. Finally, the model is completed with a slightly modified version of the Richards and Hoxey rough-wall boundary condition. The methodology is implemented and tested in the commercial code Ansys Fluent 12.1. Results are presented for a neutral boundary layer over flat terrain and for the flow around a single building immersed in an ABL.

  5. The neutral upper atmosphere

    NASA Astrophysics Data System (ADS)

    Ghosh, S. N.

    2002-07-01

    After World War II, Professor S.K. Mitra wrote a comprehensive book called The Upper Atmosphere, which dealt with information available from ground-based and balloon-borne experiments. As a result, topics such as day airglow were investigated and further ground-based experiments using incoherent back-scattering were carried out. These activities resulted in important new information on the ozonosphere. The dramatic discovery of ozone holes forms a new and exciting chapter in the discovery of atmospheric processes. While dealing with the limits of the atmosphere, reference may be made to interstellar molecules whose discovery has raised considerable scientific curiosity. Knowledge on the solar-terrestrial relationship advanced a great deal when more information on solar radiation became available by measuring higher energy photons in the UV, EUV, and even X-ray regime. All this information is incorporated in this volume and presented under the title The Neutral Upper Atmosphere. Link: http://www.wkap.nl/prod/b/0-7923-6434-1

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

    NASA Technical Reports Server (NTRS)

    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.

  7. The Atmospheric Boundary Layer

    ERIC Educational Resources Information Center

    Tennekes, Hendrik

    1974-01-01

    Discusses some important parameters of the boundary layer and effects of turbulence on the circulation and energy dissipation of the atmosphere. Indicates that boundary-layer research plays an important role in long-term forecasting and the study of air-pollution meteorology. (CC)

  8. The Atmospheric Boundary Layer

    ERIC Educational Resources Information Center

    Tennekes, Hendrik

    1974-01-01

    Discusses some important parameters of the boundary layer and effects of turbulence on the circulation and energy dissipation of the atmosphere. Indicates that boundary-layer research plays an important role in long-term forecasting and the study of air-pollution meteorology. (CC)

  9. The atmospheric boundary layer

    SciTech Connect

    Garratt, J.R.

    1992-01-01

    This book is aimed at researchers in the atmospheric and associated sciences who require a moderately advanced text on the Atmospheric Boundary Layer (ABL) in which the many links between turbulence, air-surface transfer, boundary-layer structure and dynamics, and numerical modeling are discussed and elaborated upon. Chapter 1 serves as an introduction, with Chapters 2 and 3 dealing with the development of mean and turbulence equations, and the many scaling laws and theories that are the cornerstone of any serious ABL treatment. Modelling of the ABL is crucially dependent for its realism on the surface boundary conditions, and Chapters 4 and 5 deal with aerodynamic and energy considerations, with attention to both dry and wet land surfaces and the sea. The structure of the clear-sky, thermally stratified ABL is treated in Chapter 6, including the convective and stable cases over homogeneous land, the marine ABL and the internal boundary layer at the coastline. Chapter 7 then extends the discussion to the cloudy ABL. This is seen as particularly relevant since the extensive stratocumulus regions over the sub-tropical oceans and stratus regions over the Arctic are now identified as key players in the climate system. Finally, Chapters 8 and 9 bring much of the book's material together in a discussion of appropriate ABL and surface parameterization schemes for the general circulation models of the atmosphere that are being used for climate simulation.

  10. Effect of artificial length scales in large eddy simulation of a neutral atmospheric boundary layer flow: A simple solution to log-layer mismatch

    NASA Astrophysics Data System (ADS)

    Chatterjee, Tanmoy; Peet, Yulia T.

    2017-07-01

    A large eddy simulation (LES) methodology coupled with near-wall modeling has been implemented in the current study for high Re neutral atmospheric boundary layer flows using an exponentially accurate spectral element method in an open-source research code Nek 5000. The effect of artificial length scales due to subgrid scale (SGS) and near wall modeling (NWM) on the scaling laws and structure of the inner and outer layer eddies is studied using varying SGS and NWM parameters in the spectral element framework. The study provides an understanding of the various length scales and dynamics of the eddies affected by the LES model and also the fundamental physics behind the inner and outer layer eddies which are responsible for the correct behavior of the mean statistics in accordance with the definition of equilibrium layers by Townsend. An economical and accurate LES model based on capturing the near wall coherent eddies has been designed, which is successful in eliminating the artificial length scale effects like the log-layer mismatch or the secondary peak generation in the streamwise variance.

  11. A stochastic perturbation method to generate inflow turbulence in large-eddy simulation models: Application to neutrally stratified atmospheric boundary layers

    SciTech Connect

    Muñoz-Esparza, D.; Kosović, B.; Beeck, J. van; Mirocha, J.

    2015-03-15

    Despite the variety of existing methods, efficient generation of turbulent inflow conditions for large-eddy simulation (LES) models remains a challenging and active research area. Herein, we extend our previous research on the cell perturbation method, which uses a novel stochastic approach based upon finite amplitude perturbations of the potential temperature field applied within a region near the inflow boundaries of the LES domain [Muñoz-Esparza et al., “Bridging the transition from mesoscale to microscale turbulence in numerical weather prediction models,” Boundary-Layer Meteorol., 153, 409–440 (2014)]. The objective was twofold: (i) to identify the governing parameters of the method and their optimum values and (ii) to generalize the results over a broad range of atmospheric large-scale forcing conditions, U{sub g} = 5 − 25 m s{sup −1}, where U{sub g} is the geostrophic wind. We identified the perturbation Eckert number, Ec=U{sub g}{sup 2}/ρc{sub p}θ{sup ~}{sub pm}, to be the parameter governing the flow transition to turbulence in neutrally stratified boundary layers. Here, θ{sup ~}{sub pm} is the maximum perturbation amplitude applied, c{sub p} is the specific heat capacity at constant pressure, and ρ is the density. The optimal Eckert number was found for nonlinear perturbations allowed by Ec ≈ 0.16, which instigate formation of hairpin-like vortices that most rapidly transition to a developed turbulent state. Larger Ec numbers (linear small-amplitude perturbations) result in streaky structures requiring larger fetches to reach the quasi-equilibrium solution, while smaller Ec numbers lead to buoyancy dominated perturbations exhibiting difficulties for hairpin-like vortices to emerge. Cell perturbations with wavelengths within the inertial range of three-dimensional turbulence achieved identical quasi-equilibrium values of resolved turbulent kinetic energy, q, and Reynolds-shear stress, . In contrast, large-scale perturbations

  12. Atmospheric and Space Sciences: Neutral Atmospheres

    NASA Astrophysics Data System (ADS)

    Yiǧit, Erdal

    2015-09-01

    The SpringerBriefs on Atmospheric and Space Sciences in two volumes presents a concise and interdisciplinary introduction to the basic theory, observation & modeling of atmospheric and ionospheric coupling processes on Earth. The goal is to contribute toward bridging the gap between meteorology, aeronomy, and planetary science. In addition recent progress in several related research topics, such atmospheric wave coupling and variability, is discussed. Volume 1 will focus on the atmosphere, while Volume 2 will present the ionosphere— the plasma environment. Volume 1 is aimed primarily at (research) students and researchers that would like to gain quick insight in atmospheric sciences and current research. It also is a useful tool for professors who would like to develop a course in atmospheric physics.

  13. The Martian Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Petrosyan, A.; Galperin, B.; Larsen, S. E.; Lewis, S. R.; Määttänen, A.; Read, P. L.; Renno, N.; Rogberg, L. P. H. T.; Savijärvi, H.; Siili, T.; Spiga, A.; Toigo, A.; Vázquez, L.

    2011-09-01

    The planetary boundary layer (PBL) represents the part of the atmosphere that is strongly influenced by the presence of the underlying surface and mediates the key interactions between the atmosphere and the surface. On Mars, this represents the lowest 10 km of the atmosphere during the daytime. 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 atmosphere. To date, this region of the atmosphere has been studied directly, by instrumented lander spacecraft, and from orbital remote sensing, though not to the extent that is necessary to fully constrain its character and behavior. Current data strongly suggest that as for the Earth's PBL, classical Monin-Obukhov similarity theory applies reasonably well to the Martian PBL under most conditions, though with some intriguing differences relating to the lower atmospheric density at the Martian surface and the likely greater role of direct radiative heating of the atmosphere within the PBL itself. Most of the modeling techniques used for the PBL on Earth are also being applied to the Martian PBL, including novel uses of very high resolution large eddy simulation methods. We conclude with those aspects of the PBL that require new measurements in order to constrain models and discuss the extent to which anticipated missions to Mars in the near future will fulfill these requirements.

  14. The Lowest Atmosphere: Atmospheric Boundary Layer Including Atmospheric Surface Layer.

    DTIC Science & Technology

    1996-04-01

    of motion of the atmosphere— "second order closure"—to such applications as the SCIPUFF -PC code for tracer dispersion (see Sykes, 1994). Now, for...Turbulence, Methuen, London, 2nd Ed., 1955. Sykes, R.I., "The SCIPUFF -PC Code," ARAP Draft Report, 1994. Tennekes, H., "The Atmospheric Boundary Layer

  15. Neutral upper atmospheres of the outer planets

    NASA Technical Reports Server (NTRS)

    Atreya, S. K.

    1987-01-01

    The major characteristics of the neutral upper atmospheres of outer planets are discussed, with special attention given to the Uranus upper atmosphere, probed by Voyager 2. The composition, thermal structure, photochemistry, and vertical mixing of the Uranus atmosphere are compared with the respective features of other outer planets. Unlike the atmospheres of Jupiter and Saturn, which reflect the solar ratios of the elements, the Uranus atmosphere was found to have only few constituents, including NH3, CH4, H2, He, C2H2, and C2H6. The eddy diffusion coefficient of Uranus, determined from occultation experiments, was found to be in the range 10,000-100,000 sq cm/sec, the lowest value amongst the major planets; this implies relatively sluggish vertical mixing. Another major difference from Saturn and Jupiter is in the fact that stable hydrocarbon products (C2H2 and C2H6) in the Uranus atmosphere begin to condense at around 5-10 mb level, resulting in the production of haze in the lower stratosphere.

  16. Finite-element numerical modeling of atmospheric turbulent boundary layer

    NASA Technical Reports Server (NTRS)

    Lee, H. N.; Kao, S. K.

    1979-01-01

    A dynamic turbulent boundary-layer model in the neutral atmosphere is constructed, using a dynamic turbulent equation of the eddy viscosity coefficient for momentum derived from the relationship among the turbulent dissipation rate, the turbulent kinetic energy and the eddy viscosity coefficient, with aid of the turbulent second-order closure scheme. A finite-element technique was used for the numerical integration. In preliminary results, the behavior of the neutral planetary boundary layer agrees well with the available data and with the existing elaborate turbulent models, using a finite-difference scheme. The proposed dynamic formulation of the eddy viscosity coefficient for momentum is particularly attractive and can provide a viable alternative approach to study atmospheric turbulence, diffusion and air pollution.

  17. Convection Cells in the Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Fodor, Katherine; Mellado, Juan-Pedro

    2017-04-01

    In dry, shear-free convective boundary layers (CBLs), the turbulent flow of air is known to organise itself on large scales into coherent, cellular patterns, or superstructures, consisting of fast, narrow updraughts and slow, wide downdraughts which together form circulations. Superstructures act as transport mechanisms from the surface to the top of the boundary layer and vice-versa, as opposed to small-scale turbulence, which only modifies conditions locally. This suggests that a thorough investigation into superstructure properties may help us better understand transport across the atmospheric boundary layer as a whole. Whilst their existence has been noted, detailed studies into superstructures in the CBL have been scarce. By applying methods which are known to successfully isolate similar large-scale patterns in turbulent Rayleigh-Bénard convection, we can assess the efficacy of those detection techniques in the CBL. In addition, through non-dimensional analysis, we can systematically compare superstructures in various convective regimes. We use direct numerical simulation of four different cases for intercomparison: Rayleigh-Bénard convection (steady), Rayleigh-Bénard convection with an adiabatic top lid (quasi-steady), a stably-stratified CBL (quasi-steady) and a neutrally-stratified CBL (unsteady). The first two are non-penetrative and the latter two penetrative. We find that although superstructures clearly emerge from the time-mean flow in the non-penetrative cases, they become obscured by temporal averaging in the CBL. This is because a rigid lid acts to direct the flow into counter-rotating circulation cells whose axis of rotation remains stationary, whereas a boundary layer that grows in time and is able to entrain fluid from above causes the circulations to not only grow in vertical extent, but also to move horizontally and merge with neighbouring circulations. Spatial filtering is a useful comparative technique as it can be performed on boundary

  18. The near-neutral atmospheric surface layer: turbulence and non-stationarity.

    PubMed

    Metzger, M; McKeon, B J; Holmes, H

    2007-03-15

    The neutrally stable atmospheric surface layer is used as a physical model of a very high Reynolds number, canonical turbulent boundary layer. Challenges and limitations with this model are addressed in detail, including the inherent thermal stratification, surface roughness and non-stationarity of the atmosphere. Concurrent hot-wire and sonic anemometry data acquired in Utah's western desert provide insight to Reynolds number trends in the axial velocity statistics and spectra.

  19. Neutral Beam Propagation Effects in the Upper Atmosphere.

    DTIC Science & Technology

    1984-10-01

    I 7 -AA74 6 NEUTRAL BEAR PROPAGAT ION EFFECTS IN THE UPPER7~ATMOSPHERE(U) B STON C LL CHESTNUT HILL MA DEPT OF~PHYSICS P CARINI ET AL 01 OCT 84...BUREAU OF STANDARDS 2963 A t %. -_- ’o N, r ,._ .~ , AD-A 174 896 AFGL-TR-85-0038 NEUTRAL BEAM PROPAGATION EFFECTS IN THE UPPER ATMOSPHERE P. Carini...ZIP Code) 10 SOURCE OF FUNDING NOS PROGRAM PROJECT TASK( WORK UNIT ELEMENT NO NO. NO. NO 1j 1 TITLE (Include secuit’iy ClawficaiJon) Neutral Beam

  20. The San Marco 3 neutral atmosphere composition experiment

    NASA Technical Reports Server (NTRS)

    Pelz, D. T.; Newton, G. P.; Kasprzak, W. T.; Clem, T. D.

    1973-01-01

    The experimental instrumentation of the San Marco 3 satellite is described along with the calibration and operation. The instrumentation for the following experiments was included: an air density experiment for measuring the instantaneous drag force, and thus the neutral particle total mass density; a neutral atmosphere composition experiment for measuring the densities of helium, atomic and molecular oxygen, molecular nitrogen and argon; and a neutral atmosphere temperature experiment to determine the gas kinetic temperature by measuring molecular nitrogen density variations in an orificed spherical chamber as a function of angle of attack.

  1. Drag and Atmospheric Neutral Density Explorer (DANDE)

    DTIC Science & Technology

    2009-06-04

    determination will be accomplished using Horizon Crossing Indicators. Active control shall then be performed using magnetic torque rods, and nutation ...situational awareness and presents increased challenges in the specification of the spacecraft environment in low earth orbit. Atmospheric drag has

  2. Soft turbulence in the atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Jánosi, Imre M.; Vattay, Gábor

    1993-08-01

    In this work we compare the spectral properties of the daily medium temperature fluctuations with the experimental results of the Chicago Group, in which the local temperature fluctuations were measured in a helium cell. The results suggest that the dynamics of the daily temperature fluctuations is determined by the soft turbulent state of the atmospheric boundary layer, which state is significantly different from low dimensional chaos.

  3. The Atmospheric Neutral Density Experiment (ANDE)

    DTIC Science & Technology

    2009-01-01

    scaling the B term down to fit the observations. The ANDERR data provide a global climate monitoring metric, which showed a consistent overestimation2... ve d C D MAA FCal ANDERR CD vs. Time (a) (d) (b) (e) (c) 142 2009 NRL REVIEW ATMOSPHERIC SCIENCE AND TECHNOLOGY FIGURE 8 The ANDE wind and temperature spectrometer.

  4. Spectral scales in the atmospheric boundary layer

    NASA Technical Reports Server (NTRS)

    Weber, A. H.; Irwin, J. S.; Mathis, J. J., Jr.; Kahler, J. P.; Petersen, W. B.

    1982-01-01

    Wind data taken from 10 levels between 18 and 305 m were examined to determine the properties of atmospheric turbulence within and above the atmospheric surface layer into the PBL. The samples were averaged over 40 min intervals, with all periods of rain, fog, and other disturbances being eliminated from the 16 days of monitoring. Turbulence spectra were calculated using a fast Fourier transformation. The tower was located in rolling terrain covered with pine forests, waist-high scrub, and cultivated fields. Results are presented for the wavelength and Eulerian length scales, considering the neutral, stable, and unstable PBL. Correlation coefficients were found between velocity fluctuations and wavelengths for the stability classes. Good agreements were found for measured and computed spectra in all but unstable conditions.

  5. Spectral scales in the atmospheric boundary layer

    NASA Technical Reports Server (NTRS)

    Weber, A. H.; Irwin, J. S.; Mathis, J. J., Jr.; Kahler, J. P.; Petersen, W. B.

    1982-01-01

    Wind data taken from 10 levels between 18 and 305 m were examined to determine the properties of atmospheric turbulence within and above the atmospheric surface layer into the PBL. The samples were averaged over 40 min intervals, with all periods of rain, fog, and other disturbances being eliminated from the 16 days of monitoring. Turbulence spectra were calculated using a fast Fourier transformation. The tower was located in rolling terrain covered with pine forests, waist-high scrub, and cultivated fields. Results are presented for the wavelength and Eulerian length scales, considering the neutral, stable, and unstable PBL. Correlation coefficients were found between velocity fluctuations and wavelengths for the stability classes. Good agreements were found for measured and computed spectra in all but unstable conditions.

  6. Helicity in the atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

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

  7. A reassessment of prebiotic organic synthesis in neutral planetary atmospheres.

    PubMed

    Cleaves, H James; Chalmers, John H; Lazcano, Antonio; Miller, Stanley L; Bada, Jeffrey L

    2008-04-01

    The action of an electric discharge on reduced gas mixtures such as H(2)O, CH(4) and NH(3) (or N(2)) results in the production of several biologically important organic compounds including amino acids. However, it is now generally held that the early Earth's atmosphere was likely not reducing, but was dominated by N(2) and CO(2). The synthesis of organic compounds by the action of electric discharges on neutral gas mixtures has been shown to be much less efficient. We show here that contrary to previous reports, significant amounts of amino acids are produced from neutral gas mixtures. The low yields previously reported appear to be the outcome of oxidation of the organic compounds during hydrolytic workup by nitrite and nitrate produced in the reactions. The yield of amino acids is greatly increased when oxidation inhibitors, such as ferrous iron, are added prior to hydrolysis. Organic synthesis from neutral atmospheres may have depended on the oceanic availability of oxidation inhibitors as well as on the nature of the primitive atmosphere itself. The results reported here suggest that endogenous synthesis from neutral atmospheres may be more important than previously thought.

  8. Simulations of Atmospheric Neutral Wave Coupling to the Ionosphere

    NASA Astrophysics Data System (ADS)

    Siefring, C. L.; Bernhardt, P. A.

    2005-12-01

    The densities in the E- and F-layer plasmas are much less than the density of background neutral atmosphere. Atmospheric neutral waves are primary sources of plasma density fluctuations and are the sources for triggering plasma instabilities. The neutral atmosphere supports acoustic waves, acoustic gravity waves, and Kelvin Helmholtz waves from wind shears. These waves help determine the structure of the ionosphere by changes in neutral density that affect ion-electron recombination and by neutral velocities that couple to the plasma via ion-neutral collisions. Neutral acoustic disturbances can arise from thunderstorms, chemical factory explosions and intentional high-explosive tests. Based on conservation of energy, acoustic waves grow in amplitude as they propagate upwards to lower atmospheric densities. Shock waves can form in an acoustic pulse that is eventually damped by viscosity. Ionospheric effects from acoustic waves include transient perturbations of E- and F-Regions and triggering of E-Region instabilities. Acoustic-gravity waves affect the ionosphere over large distances. Gravity wave sources include thunderstorms, auroral region disturbances, Space Shuttle launches and possibly solar eclipses. Low frequency acoustic-gravity waves propagate to yield traveling ionospheric disturbances (TID's), triggering of Equatorial bubbles, and possible periodic structuring of the E-Region. Gravity wave triggering of equatorial bubbles is studied numerically by solving the equations for plasma continuity and ion velocity along with Ohms law to provide an equation for the induced electric potential. Slow moving gravity waves provide density depressions on bottom of ionosphere and a gravitational Rayleigh-Taylor instability is initiated. Radar scatter detects field aligned irregularities in the resulting plasma bubble. Neutral Kelvin-Helmholtz waves are produced by strong mesospheric wind shears that are also coincident with the formation of intense E-layers. An

  9. Nonstationary atmospheric boundary layer turbulence simulation

    NASA Technical Reports Server (NTRS)

    Fichtl, G. H.; Perlmutter, M.

    1974-01-01

    Report on a new and general technique for simulating atmospheric turbulence-like random processes which are statistically homogeneous along the horizontal and nonhomogeneous along the vertical. This technique is general in the sense that it can be used for a broad class of similar problems. Like the other presently available schemes, the techniques presented are based on the Dryden hypothesis and Taylor's frozen eddy hypothesis; however, they go a step further by utilizing certain self-similarity properties of the Dryden spectral density function which permits the development of height invariant filters. These filters are in turn used to generate vertically homogeneous (statistically) random processes from which turbulence at any specified level in the boundary layer can be simulated, thus facilitating the simulation of a nonstationary turbulence process along the flight path of an aircraft during take-off or landing.

  10. A Coupled Ion-Neutral Photochemical Model for the Titan Atmosphere

    NASA Astrophysics Data System (ADS)

    Vuitton, Veronique; Yelle, Roger V.; Klippenstein, Stephen J.; Hörst, Sarah M.; Lavvas, Panayotis

    2014-11-01

    Recent observations from the Cassini-Huygens spacecraft and the Herschel space observatory drastically increased our knowledge of Titan's chemical composition. The combination of data retrieved by Cassini INMS, UVIS, and CIRS allows deriving the vertical profiles of half a dozen species from 1000 to 100 km, while the HIFI instrument on Herschel reported on the first identification of HNC. Partial data or upper limits are available for almost 20 other CHON neutral species. The INMS and CAPS instruments onboard Cassini also revealed the existence of numerous positive and negative ions in Titan's upper atmosphere. We present the results of a 1D coupled ion-neutral photochemical model intended for the interpretation of the distribution of gaseous species in the Titan atmosphere. The model extends from the surface to the exobase. The atmospheric background, boundary conditions, vertical transport and aerosol opacity are all constrained by the Cassini-Huygens observations. The chemical network includes reactions between hydrocarbons, nitrogen and oxygen bearing species (including some species containing both nitrogen and oxygen, such as NO). It takes into account neutrals and both positive and negative ions with m/z extending up to about 100 u. Ab initio Transition State Theory calculations are performed in order to evaluate the rate coefficients and products for critical reactions. The calculated vertical profiles of neutral and ion species generally agree with the existing observational data; some differences are highlighted. We discuss the chemical and physical processes responsible for the production and loss of some key species. We find that the production of neutral species in the upper atmosphere from electron-ion recombination reactions and neutral-neutral radiative association reactions is significant. In the stratosphere, the vertical profile of (cyano)polyynes is extremely sensitive to their heterogeneous loss on aerosols, a process that remains to be

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

    SciTech Connect

    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).

  12. Turbulence in the Stable Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Fernando, Harindra; Kit, Eliezer; Conry, Patrick; Hocut, Christopher; Liberzon, Dan

    2016-11-01

    During the field campaigns of the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program, fine-scale measurements of turbulence in the atmospheric boundary layer (ABL) were made using a novel sonic and hot-film anemometer dyad (a combo probe). A swath of scales, from large down to Kolmogorov scales, was covered. The hot-film was located on a gimbal within the sonic probe volume, and was automated to rotate in the horizontal plane to align with the mean flow measured by sonic. This procedure not only helped satisfy the requirement of hot-film alignment with the mean flow, but also allowed in-situ calibration of hot-films. This paper analyzes a period of nocturnal flow that was similar to an idealized stratified parallel shear flow. Some new phenomena were identified, which included the occurrence of strong bursts in the velocity records indicative of turbulence generation at finer scales that are not captured by conventional sonic anemometers. The spectra showed bottleneck effect, but its manifestation did not fit into the framework of previous bottleneck-effect theories and was unequivocally related to bursts of turbulence. The measurements were also used to evaluate the energetics of stratified shear flows typical of the environment. ONR # N00014-11-1-0709; NSF # AGS-1528451; ISF 408/15.

  13. Ionospheric E-region electron density and neutral atmosphere variations

    NASA Technical Reports Server (NTRS)

    Stick, T. L.

    1976-01-01

    Electron density deviations from a basic variation with the solar zenith angle were investigated. A model study was conducted in which the effects of changes in neutral and relative densities of atomic and molecular oxygen on calculated electron densities were compared with incoherent scatter measurements in the height range 100-117 km at Arecibo, Puerto Rico. The feasibility of determining tides in the neutral atmosphere from electron density profiles was studied. It was determined that variations in phase between the density and temperature variation and the comparable magnitudes of their components make it appear improbable that the useful information on tidal modes can be obtained in this way.

  14. Inverted floor wind-tunnel simulation of stably stratified atmospheric boundary layer flow

    NASA Astrophysics Data System (ADS)

    Grainger, Clive; Meroney, Robert N.

    Most of the critical transport processes in the atmosphere are dominated by density stratification; hence, physical modeling facilities which neglect the important contributions of buoyancy are limited to the examination of high winds or those brief moments after sunrise or before sunset when the atmosphere is nominally neutrally stratified. Large new facilities constructed specifically to simulate the atmosphere offer new opportunities to study the physics of mixing processes dominated by stratification. A novel arrangement to simulate stably stratified atmospheric boundary layer flows in large wind tunnels using distributed electrical heaters and an inverted ground plane to simulate nighttime inversions is described, together with initial measurements.

  15. Measuring Mars' Atmospheric Neutral Density from 160 to 320km altitude with the MGS Electron Reflectometer

    NASA Astrophysics Data System (ADS)

    Lillis, R. J.; Mitchell, D. L.; Lin, R. P.; Acuna, M. H.

    2003-12-01

    The Magnetometer/Electron Reflectometer (MAG/ER) experiment aboard Mars Global Surveyor (MGS) samples the local electron population's distribution in energy and pitch angle (angle between electron velocity and local magneticfield direction) at the mapping orbit altitude of ~400km. We develop a single-particle model of the electrons' interaction with the neutral atmosphere and motion along open field-lines connecting the solar wind to remnant crustal magnetization. Electron reflection from magnetic gradients and absorption due to inelastic collisons with atmospheric neutrals results in characteristic pitch angle (PA) distributions for open field lines. By assuming the validity of spherical harmonic expansions (Cain, Arkani-hamed) in the strongest field regions of Mars (such as Terra Sirenum), we trace the electron paths and fit these PA distributions to our model to constrain the scale height and base density of the neutral atmosphere in the interaction region, which is between 160 and 320km altitude. We analyse ~2 martian years of MGS mapping Orbit Data and present the first measurements of Mars' exospheric neutral density. We track density variations over season, latitude and solar cycle and compare with predictions from Mars Thermosphere Global Circulation Model (MTGCM) simulations and with MGS acceleromater data. Our results will help to constrain the upper boundaries of GCMs and assist orbital decay calculations for low-orbiting spacecraft, such as the 2005 Mars Reconnaissance Orbiter.

  16. Neutral molecular cluster formation of sulfuric acid-dimethylamine observed in real time under atmospheric conditions.

    PubMed

    Kürten, Andreas; Jokinen, Tuija; Simon, Mario; Sipilä, Mikko; Sarnela, Nina; Junninen, Heikki; Adamov, Alexey; Almeida, João; Amorim, Antonio; Bianchi, Federico; Breitenlechner, Martin; Dommen, Josef; Donahue, Neil M; Duplissy, Jonathan; Ehrhart, Sebastian; Flagan, Richard C; Franchin, Alessandro; Hakala, Jani; Hansel, Armin; Heinritzi, Martin; Hutterli, Manuel; Kangasluoma, Juha; Kirkby, Jasper; Laaksonen, Ari; Lehtipalo, Katrianne; Leiminger, Markus; Makhmutov, Vladimir; Mathot, Serge; Onnela, Antti; Petäjä, Tuukka; Praplan, Arnaud P; Riccobono, Francesco; Rissanen, Matti P; Rondo, Linda; Schobesberger, Siegfried; Seinfeld, John H; Steiner, Gerhard; Tomé, António; Tröstl, Jasmin; Winkler, Paul M; Williamson, Christina; Wimmer, Daniela; Ye, Penglin; Baltensperger, Urs; Carslaw, Kenneth S; Kulmala, Markku; Worsnop, Douglas R; Curtius, Joachim

    2014-10-21

    For atmospheric sulfuric acid (SA) concentrations the presence of dimethylamine (DMA) at mixing ratios of several parts per trillion by volume can explain observed boundary layer new particle formation rates. However, the concentration and molecular composition of the neutral (uncharged) clusters have not been reported so far due to the lack of suitable instrumentation. Here we report on experiments from the Cosmics Leaving Outdoor Droplets chamber at the European Organization for Nuclear Research revealing the formation of neutral particles containing up to 14 SA and 16 DMA molecules, corresponding to a mobility diameter of about 2 nm, under atmospherically relevant conditions. These measurements bridge the gap between the molecular and particle perspectives of nucleation, revealing the fundamental processes involved in particle formation and growth. The neutral clusters are found to form at or close to the kinetic limit where particle formation is limited only by the collision rate of SA molecules. Even though the neutral particles are stable against evaporation from the SA dimer onward, the formation rates of particles at 1.7-nm size, which contain about 10 SA molecules, are up to 4 orders of magnitude smaller compared with those of the dimer due to coagulation and wall loss of particles before they reach 1.7 nm in diameter. This demonstrates that neither the atmospheric particle formation rate nor its dependence on SA can simply be interpreted in terms of cluster evaporation or the molecular composition of a critical nucleus.

  17. Neutral molecular cluster formation of sulfuric acid–dimethylamine observed in real time under atmospheric conditions

    PubMed Central

    Kürten, Andreas; Jokinen, Tuija; Simon, Mario; Sipilä, Mikko; Sarnela, Nina; Junninen, Heikki; Adamov, Alexey; Almeida, João; Amorim, Antonio; Bianchi, Federico; Breitenlechner, Martin; Dommen, Josef; Donahue, Neil M.; Duplissy, Jonathan; Ehrhart, Sebastian; Flagan, Richard C.; Franchin, Alessandro; Hakala, Jani; Hansel, Armin; Heinritzi, Martin; Hutterli, Manuel; Kangasluoma, Juha; Kirkby, Jasper; Laaksonen, Ari; Lehtipalo, Katrianne; Leiminger, Markus; Makhmutov, Vladimir; Mathot, Serge; Onnela, Antti; Petäjä, Tuukka; Praplan, Arnaud P.; Riccobono, Francesco; Rissanen, Matti P.; Rondo, Linda; Schobesberger, Siegfried; Seinfeld, John H.; Steiner, Gerhard; Tomé, António; Tröstl, Jasmin; Winkler, Paul M.; Williamson, Christina; Wimmer, Daniela; Ye, Penglin; Baltensperger, Urs; Carslaw, Kenneth S.; Kulmala, Markku; Worsnop, Douglas R.; Curtius, Joachim

    2014-01-01

    For atmospheric sulfuric acid (SA) concentrations the presence of dimethylamine (DMA) at mixing ratios of several parts per trillion by volume can explain observed boundary layer new particle formation rates. However, the concentration and molecular composition of the neutral (uncharged) clusters have not been reported so far due to the lack of suitable instrumentation. Here we report on experiments from the Cosmics Leaving Outdoor Droplets chamber at the European Organization for Nuclear Research revealing the formation of neutral particles containing up to 14 SA and 16 DMA molecules, corresponding to a mobility diameter of about 2 nm, under atmospherically relevant conditions. These measurements bridge the gap between the molecular and particle perspectives of nucleation, revealing the fundamental processes involved in particle formation and growth. The neutral clusters are found to form at or close to the kinetic limit where particle formation is limited only by the collision rate of SA molecules. Even though the neutral particles are stable against evaporation from the SA dimer onward, the formation rates of particles at 1.7-nm size, which contain about 10 SA molecules, are up to 4 orders of magnitude smaller compared with those of the dimer due to coagulation and wall loss of particles before they reach 1.7 nm in diameter. This demonstrates that neither the atmospheric particle formation rate nor its dependence on SA can simply be interpreted in terms of cluster evaporation or the molecular composition of a critical nucleus. PMID:25288761

  18. Atmospheric Boundary-Layer Turbulence Intermittency Revisited

    NASA Astrophysics Data System (ADS)

    Mezemate, Y.; Fitton, G. F.; Tchiguirinskaia, I.; Schertzer, D. J. M.

    2015-12-01

    Turbulence has been and still is the focus of countless experimental, numerical, and theoretical studies. A common physics based approach to complex problems involving extremely large (possibly infinite) degrees of freedom is to consider the possible symmetries of the governing equations. In turbulence, the scaling symmetry of the Navier-Stokes equation justifies a multiple scaling (multifractal) analysis of the phenomena. Kolmogorov's famous 1941 hypotheses led to the 2/3rds law (essentially hypothesizing fractal velocity statistics) for the velocity increments and later in 1962 corrected his hypothesis to include an intermittency correction (essentially allowing the velocity to have multiple scaling exponents). Both hypotheses have been tested in numerous wind tunnel experiments but empirical validation of the hypotheses in the atmospheric boundary-layer have been difficult due to complex symmetry breaking effects. Using 50Hz Sonic Anemometer velocity data measured on the site of École des Ponts ParisTech we test Kolmogorov's hypotheses. We find that contrary to numerous wind tunnel testing results, we do not observe a slight increase of the spectral exponent, but a significant decrease this exponent, therefore that intermittency favorise small eddies. We show that it is necessary to reconsider the classical and frequently used assumptions regarding the normalization of the energy flux through scales.

  19. Transport in a field aligned magnetized plasma/neutral gas boundary: the end of the plasma

    NASA Astrophysics Data System (ADS)

    Cooper, Christopher Michael

    The objective of this dissertation is to characterize the physics of a boundary layer between a magnetized plasma and a neutral gas along the direction of a confining magnetic field. A series of experiments are performed at the Enormous Toroidal Plasma Device (ETPD) at UCLA to study this field aligned Neutral Boundary Layer (NBL) at the end of the plasma. A Lanthanum Hexaboride (LaB6) cathode and semi-transparent anode creates a magnetized, current-free helium plasma which terminates on a neutral helium gas without touching any walls. Probes are inserted into the plasma to measure the basic plasma parameters and study the transport in the NBL. The experiment is performed in the weakly ionized limit where the plasma density (ne) is much less than the neutral density (nn) such that ne/nn < 5%. The NBL is characterized by a field-aligned electric field which begins at the point where the plasma pressure equilibrates with the neutral gas pressure. Beyond the pressure equilibration point the electrons and ions lose their momentum by collisions with the neutral gas and come to rest. An electric field is established self consistently to maintain a current-free termination through equilibration of the different species' stopping rates in the neutral gas. The electric field resembles a collisional quasineutral sheath with a length 10 times the electron-ion collision length, 100 times the neutral collision length, and 10,000 times the Debye length. Collisions with the neutral gas dominate the losses in the system. The measured plasma density loss rates are above the classical cross-field current-free ambipolar rate, but below the anomalous Bohm diffusion rate. The electron temperature is below the ionization threshold of the gas, 2.2 eV in helium. The ions are in thermal equilibrium with the neutral gas. A generalized theory of plasma termination in a Neutral Boundary Layer is applied to this case using a two-fluid, current-free, weakly ionized transport model. The electron

  20. A magnetospheric energy principle extended to include neutral atmosphere

    SciTech Connect

    Miura, Akira

    2011-03-15

    The problem of ideal magnetohydrodynamic stability of plasmas in a magnetosphere-atmosphere system, in which the unperturbed magnetic field is assumed to be perpendicular to the plasma-atmosphere interface (ionospheric surface), is investigated by means of an extended magnetospheric energy principle. The derivation of the principle and conditions under which it applies to a real terrestrial magnetosphere is given. In the principle, the atmosphere is considered to be a very heavy and compressible gas with finite pressure. A thin ionospheric layer is taken into account as boundary conditions, but energetics within it are neglected. The solid-earth surface is assumed to be a perfectly conducting wall for perturbations. For a perturbation that satisfies either rigid or horizontally free boundary conditions at the plasma-atmosphere interface, the self-adjointness of the force operator is satisfied and an extended magnetospheric energy principle can be developed on the basis of the extended energy principle for fusion plasmas. These two boundary conditions are shown to be realized in the magnetosphere when the ionospheric conductivity is either very large or very small. Whereas in fusion plasmas the perturbed magnetic energy in the vacuum makes a stabilizing contribution to the potential energy, in the magnetosphere the perturbed magnetic energy in the atmosphere makes no such stabilizing contribution. This is due to the difference of the assumed field configurations of the magnetospheric and fusion plasmas. The ionospheric surface makes a destabilizing negative contribution to the potential energy owing to a horizontal plasma displacement on the spherical ionospheric surface. The method is applied to magnetospheric ballooning and interchange instabilities. The existence of a new type of magnetospheric interchange instability is shown and its structure in the magnetosphere-atmosphere system is clarified. Possible consequences of the instabilities and their relevance to

  1. An Indirect and Dynamically Induced Energy Mechanism in a Plasma-Neutral Atmosphere

    NASA Astrophysics Data System (ADS)

    Hsu, Vicki W.

    Plasma-neutral interactions play an integral role in governing the dynamics and energy of an upper atmosphere. In the Earth's ionosphere-thermosphere (I/T) region, these interactions can produce significant structure in neutral temperature, winds, mass density, and composition. External sources of momentum and energy that directly affect these properties of the upper atmosphere have been extensively investigated, but these investigations are not sufficient to fully describe thermosphere phenomenology. Considering the strong plasma-neutral coupling in the I/T region, an internal and indirect energy mechanism, or a feedback exchange between hydrodynamics and thermodynamics, can contribute to the resultant structure. The complex, indirect consequences of internal momentum changes on neutral gas properties have not been thoroughly assessed due to the multivariate nature of the problem and limited observations. Through the use of the National Center for Atmospheric Research Thermosphere-Ionosphere-Electrodynamics General Circulation Model, this thesis seeks to simulate, understand, and quantify how plasma-neutral interactions affect the energy distribution of the upper thermosphere via an indirect, dynamically induced mechanism, and to establish that this mechanism can explain the existence of thermospheric density features. The main conclusions that stem from this dissertation are as follows: (1) Changes in the field-aligned ion drag force alter neutral temperature and mass density by means of a divergent neutral wind field, commanding the formation, local time, and solar cycle variations of the equatorial thermosphere anomaly trough; (2) Ion and viscous drag forces produce balanced motion with sustained, divergent winds that change thermal and mass density structure through adiabatic heating; (3) A boundary that delineates the lower and upper thermosphere is recognized and deemed the "thermopause", and helium is demonstrated to be an effective dynamic tracer for a

  2. A coupled ion-neutral photochemical model for the Titan atmosphere

    NASA Astrophysics Data System (ADS)

    Vuitton, V.; Yelle, R. V.; Klippenstein, S. J.; Horst, S. M.; Lavvas, P.

    2013-12-01

    Recent observations from the Cassini-Huygens spacecraft and the Herschel space observatory drastically increased our knowledge of Titan's chemical composition. The combination of data retrieved by Cassini INMS, UVIS, and CIRS allows deriving the vertical profiles of half a dozen species from 1000 to 100 km, while the HIFI instrument on Herschel reported on the first identification of HNC. Partial data or upper limits are available for almost 20 other CHON neutral species. The INMS and CAPS instruments onboard Cassini also revealed the existence of numerous positive and negative ions in Titan's upper atmosphere. We present the results of a 1D coupled ion-neutral photochemical model intended for the interpretation of the distribution of gaseous species in the Titan atmosphere. The model extends from the surface to the exobase. The atmospheric background, boundary conditions, vertical transport and aerosol opacity are all constrained by the Cassini-Huygens observations. The chemical network includes reactions between hydrocarbons, nitrogen and oxygen bearing species (including some species containing both nitrogen and oxygen, such as NO). It takes into account neutrals and both positive and negative ions with m/z extending up to about 100 u. Ab initio Transition State Theory calculations are performed in order to evaluate the rate coefficients and products for critical reactions. The production of minor nitrogen-bearing species and hydrocarbons is initiated by the dissociation and ionization of N2 and CH4 by solar VUV/EUV photons and associated photoelectrons in the upper atmosphere. We incorporate new high-resolution isotopic photoabsorption and photodissociation cross sections for N2 as well as new photodissociation branching ratios for CH4 and C2H2. The photodissociation of hydrocarbon radicals is taken into account and its impact on the chemistry is discussed for the first time. The presence of oxygen-bearing species is explained by an influx of oxygen originating

  3. Composition and Chemistry of the Neutral Atmosphere of Venus

    NASA Astrophysics Data System (ADS)

    Marcq, E.; Millis, F.; Sandor, B.; Vandaele, A. C.

    2014-04-01

    With the pending ending of the ESA Venus Express mission after 8 years of scientific success, a new page in the in situ exploration of the inner solar system is on the verge of being turned. Considering how much our vision of Venus has been updated and refined thanks to it, the scientific community has decided to summarize our new picture of Venus in a dedicated book. This talk aims at presenting the structure and some contents of the Composition and Chemistry of the Neutral Atmosphere chapter.

  4. Temperature Variations in the Martian Upper Atmosphere from the MAVEN Neutral Gas and Ion Mass Spectrometer

    NASA Astrophysics Data System (ADS)

    Stone, Shane W.; Yelle, Roger; Mahaffy, Paul; Benna, Mehdi; Elrod, Meredith K.; Bougher, Stephen W.; MAVEN

    2016-10-01

    The MAVEN Neutral Gas and Ion Mass Spectrometer (NGIMS) measures composition and variability of neutral and ionic species in the Martian upper atmosphere, allowing us to calculate neutral temperatures from roughly 130 km to 300 km above the surface. Over the past two years at Mars, NGIMS has collected an extensive and useful data set that covers much of the Martian thermosphere and exosphere. We use new, improved algorithms for the most accurate determination of densities from the NGIMS data. We use the densities of inert species (specifically CO2, Ar, and N2) along with a hydrostatic equilibrium model to infer the temperature profile and its uncertainty. Uncertainties include the errors in the density measurements, unknown upper boundary conditions, and horizontal variations in the atmosphere. Our calculations reveal diurnal temperature variations of up to 90 K and maximum latitudinal temperature variations of 130 K. These fluctuations in temperature in the upper atmosphere are surprising because they are significantly larger than those predicted by the latest 3D general circulation models for Mars.

  5. An interpretation of radiosonde errors in the atmospheric boundary layer

    Treesearch

    Bernadette H. Connell; David R. Miller

    1995-01-01

    The authors review sources of error in radiosonde measurements in the atmospheric boundary layer and analyze errors of two radiosonde models manufactured by Atmospheric Instrumentation Research, Inc. The authors focus on temperature and humidity lag errors and wind errors. Errors in measurement of azimuth and elevation angles and pressure over short time intervals and...

  6. Measuring Mars' Atmospheric Neutral Density from 160 to 220km with the MGS Electron Reflectometer

    NASA Astrophysics Data System (ADS)

    Lillis, R.; Engel, J.; Mitchell, D.; Brain, D.; Lin, R.; Bougher, S.; Acuna, M.

    2005-08-01

    The Magnetometer/Electron Reflectometer (MAG/ER) experiment aboard Mars Global Surveyor (MGS) samples the local electron population's distribution in energy and pitch angle (angle between electron velocity and local magnetic field direction) at the mapping orbit altitude of ˜400km. We develop a single-particle model of the electrons' interaction with the neutral atmosphere and motion along open field-lines connecting the solar wind to remnant crustal magnetization. Electron reflection from magnetic gradients and absorption due to inelastic collisons with atmospheric neutrals results in characteristic pitch angle (PA) distributions for open field lines. By assuming the validity of spherical harmonic expansions (Cain et al, 2003) in the strongest field regions of Mars (such as Terra Sirenum), we trace the electron paths and fit these PA distributions to our model to constrain the scale height and density of the neutral atmosphere in the region of greatest absorption, 160-220km. We analyse almost 3 martian years of MGS mapping Orbit Data and present the first measurements of Mars' neutral density above 180km. Although the uncertainties in single measurements are quite large, averaging over many measurements over a period of weeks allows us to see long-term trends. Major results are: 1) a mean density of 0.03 kg/km3 at 160km with a month-averaged variation of ˜40%, 2) a very strong annual seasonal variation, confirmed by periodogram and least-squares fit and 3) increasing seasonal density variability with distance from the equator. We see broad general agreement with predictions from Mars Thermosphere Global Circulation Model (MTGCM) simulations [Bougher et al, 2004] and with inferred densities from MGS Doppler tracking data [Tracadas et al, 2001]. Our results will help to constrain the upper boundaries of GCMs and assist orbital decay calculations for low-orbiting spacecraft, such as the 2005 Mars Reconnaissance Orbiter. We thank the NASA Jet Propulsion Laboratory

  7. FIFE atmospheric boundary layer budget methods

    NASA Technical Reports Server (NTRS)

    Betts, A. K.

    1992-01-01

    The budget methods and the mixed layer model employed to analyze the aircraft data from the First ISLSCP Field Experiment (FIFE) are described. Vector budgets for the mixed layer are discussed on conserved variable diagrams. Theoretical solutions are presented for the critical surface Bowen ratio that produces no boundary layer moistening or equivalent potential temperature rise as a function of the Bowen ratio at the inversion.

  8. Stable Layers in the Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Mahalov, A.; Berman, N. S.; Fernando, H. J. S.; Yu, F.; Pardyjak, E.

    1998-11-01

    Field experimental studies on the establishment and growth of the nocturnal stable layer near the ground were made in January, 1998 using a tethered balloon at a site in Phoenix, Arizona. Days and nights with clear skies and light surface winds were of particular interest because small particle and carbon monoxide concentrations can be high during such times. Closest to the ground a shallow stable layer 20 meters deep with a buoyancy frequency (N) of 0.05 1/s rapidly developed before sundown. The height of this layer and N remained constant throughout the night. Above the 20-meter level, there was a transition layer which was also stable with N = 0.025 1/s. This transition layer grew throughout the night and reached 120 meters by dawn. Above the transition layer was a neutrally stable (residual) layer left over from the previous day. An unsteady layer 10 to 100 m thick with N = 0.025 1/s was also found at the top of the troposphere with the neutrally stable troposphere below and the stable stratosphere above. The growth and/or decay of turbulence in such stable layers will be discussed in light of recent theoretical developments.

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Velocity Spectra In The Marine Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Smedman, A.

    In some respects the turbulence structure in the marine atmospheric boundary layer (MABL) reacts in the same way as the boundary layer over land, that is to say Monin-Obukhov similarity theory can be applied. There are, however, frequently situations when the similarity between the two breaks down. Analysis of measurements, taken at the flat, small island Oestergarnsholm in the middle of the Baltic Sea, clearly shows the influence of the sea state on MABL. The measurements comprise turbulence and mean variables taken at several heights on a 30 m tower, as well as wave parameters from a Wave Rider Buoy deployed 3 km outside the island. Model results of the wave field around the island together with foot-print analysis indicate that the wave field is almost un disturbed for low to moderate wind speeds but has to be corrected for limited water depth for the highest wind speeds. Our earlier analysis shows a strict similarity with over-land conditions for both mean and turbulence variables (mean wind gradient, fluxes, spectra etc.) for growing waves (young waves) travelling slower than the wind. But as soon as some waves become mature and get a speed faster than the wind speed, similarity breaks down. Thus the turbulence structure in the MABL needs to be described in terms of additional parameters such as wave age and maybe boundary layer height. Spectra of the velocity components in the MABL have been analyzed taking sea state into account. During neutral stability and young sea spectra follow the new similarity theory proposed by Hunt and Carlotti (2000) and Högström, Hunt and Smedman (2001). But with increasing wavelength of the surface waves spectra gradually change both shape and energy level, beginning at the low frequency end and continuing towards higher frequencies. For cp/U ~ 1 (where cp is the peak phase speed) the `breaking point' can be seen in the inertial subrange, which actually gives two frequency intervals with a ­2/3 slope but with different

  11. Regional scale evaporation and the atmospheric boundary layer

    NASA Technical Reports Server (NTRS)

    Parlange, Marc B.; Eichinger, William E.; Albertson, John D.

    1995-01-01

    In this review we briefly summarize some current models of evaporation and the atmospheric boundary layer (ABL) and discuss new experimental and computational oppurtunities that may aid our understanding of evaporation at these larger scales. In particular, consideration is given to remote sensing of the atmosphere, computational fluid dynamics and the role numerical models can play in understanding land-atmosphere interactions. These powerful modeling and measurement tools are allowing us to visualize and study spatial and temporal scales previously untouched, thereby increasing the oppurtunities to improve our understanding of land-atmosphere interaction.

  12. Wind-farms in shallow conventionally neutral boundary layers: effects of transition and gravity waves on energy budget

    NASA Astrophysics Data System (ADS)

    Meyers, Johan; Allaerts, Dries

    2016-11-01

    Conventionally neutral boundary layers (CNBL) often arise in offshore conditions. In these situations the neutral boundary layer is capped by a strong inversion layer and a stably stratified free atmosphere aloft. We use large-eddy simulations to investigate the interaction between a CNBL and a large wind farm. Following the approach of Allaerts & Meyers (2015), a set of equilibrium CNBLs are produced in a precursor simulation, with a height of approx. 300, 500, and 1000m, respectively. These are used at the inlet of a large wind-farm with a fetch of 15 km, and 20 rows of turbines. We find that above the farm, an internal boundary layer (IBL) develops. For the two lower CNBL cases, the IBL growth is stopped by the overlying capping inversion. Moreover, the upward displacement of the CNBL excites gravity waves in the inversion layer and the free atmosphere above. For the lower CNBL cases, these waves induce significant pressure gradients in the farm. A detailed energy budget analysis of the CNBL is further presented. The authors acknowledge support from the European Research Council (FP7-Ideas, Grant No. 306471).

  13. Measurement of argon neutral velocity distribution functions near an absorbing boundary in a plasma

    NASA Astrophysics Data System (ADS)

    Short, Zachary; Thompson, Derek; Good, Timothy; Scime, Earl

    2016-10-01

    Neutral particle distributions are critical to the study of plasma boundary interactions, where ion-neutral collisions, e.g. via charge exchange, may modify energetic particle populations impacting the boundary surface. Neutral particle behavior at absorbing boundaries thus underlies a number of important plasma physics issues, such as wall loading in fusion devices and anomalous erosion in Hall thruster channels. Neutral velocity distribution functions (NVDFs) are measured using laser-induced fluorescence (LIF). Our LIF scheme excites the 1s4 non-metastable state of neutral argon with 667.913 nm photons. The subsequent decay emission at 750.590 nm is recorded synchronously with injection laser frequency. Measurements are performed near a grounded boundary immersed in a cylindrical helicon plasma, with the boundary plate oriented at an oblique angle to the magnetic field. NVDFs are recorded in multiple velocity dimensions and in a three-dimensional volume, enabling point-to-point comparisons with NVDF predictions from particle-in-cell models as well as comparisons with ion velocity distribution function measurements obtained in the same regions through Ar-II LIF. This work is supported by US National Science Foundation Grant Number PHYS-1360278.

  14. Evaluating Models of The Neutral, Barotropic Planetary Boundary Layer using Integral Measures: Part I. Overview

    NASA Astrophysics Data System (ADS)

    Hess, G. D.; Garratt, J. R.

    Data for the cross-isobaric angle 0, the geostrophic drag coefficient Cg, and the functions A and B of Rossby number similarity theory, obtained from meteorological field experiments, are used to evaluate a range of models of the neutral, barotropic planetary boundary layer. The data give well-defined relationships for 0, Cg, and the integrated dissipation rate over the boundary layer, as a function of the surface Rossby number. Lettau's first-order closure mixing-length model gives an excellent fit to the data; other simple models give reasonable agreement. However more sophisticated models, e.g., higher-order closure, large-eddy simulation, direct numerical simulation and laboratory models, give poor fits to the data. The simplemodels have (at least) one free parameter in their turbulence closure that is matched toatmospheric observations; the more sophisticated models either base their closure onmore general flows or have no free closure parameters. It is suggested that all of theatmospheric experiments that we could locate violate the strict simplifying assumptionsof steady, homogeneous, neutral, barotropic flow required by the sophisticated models.The angle 0 is more sensitive to violations of the assumptions than is Cg.

    The behaviour of the data varies in three latitude regimes. In middle and high latitudes the observed values of A and B exhibit little latitudinal dependence; the best estimates are A = 1.3 and B = 4.4. In lower latitudes the neutral, barotropic Rossby number theory breaks down. The value of B increases towards the Equator; the determination of A is ambiguous - the trend can increase or decrease towards the Equator. Between approximately 5° and 30° latitude, the scatter in the data is thought to be primarily due to the inherent presence of baroclinicity. The presence of the trade-wind inversion, thermal instability and the horizontal component of the Earth's rotation ΩH also contribute.Marked changes in the values of A and B

  15. Airborne validation of ground-object detection from polarized neutral-point atmosphere.

    PubMed

    Yang, Shang-qiang; Guan, Gui-xia; Zhao, Hai-meng; Zhao, Hong-ying; Yang, Bin; Zhang, Wen-kai; Tan, Xiang; Wu, Tai-xia; Yan, Lei

    2013-09-01

    Based on the object's polarization effects, polarization is a newly emerging method in the field of remote sensing. Both objects and atmosphere have polarization effects, however, the atmosphere's polarization effects are much stronger than that of objects'. Consequently, atmosphere polarization effects will interfere or even cover objects' when observing with sensors. How to maximally eliminate the polarized effects generated by the atmosphere is a crucial problem in polarization remote sensing. Atmospheric neutral point is an area where the degree of atmosphere polarization is near to zero; therefore, if sensors are set up in this area, atmosphere polarization would be greatly eliminated, which is the main content of separating the effects between objects and atmosphere by its neutral point method. In this paper, after processing and analyzing the experimental data got from the first polarization remote sensing flight experiment with atmosphere neutral point, the degree of polarization images captured in neutral and non-neutral point area were obtained, and it can be seen that the main value of polarized degree of images got in neutral point area was obviously smaller than that in non-neutral point area. The results showed that the theory mentioned above was logical and practical. An innovation in our study is that the requirements needed in polarization remote sensing flight with neutral point were clarified. In the meantime, a qualitative conclusion was drawn that observing with longer wavelength is more applicable to polarization remote sensing.

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

    SciTech Connect

    Klein, P; Bonin, TA; Newman, JF; Turner, DD; Chilson, P; Blumberg, WG; Mishra, S; Wainwright, CE; Carney, M; Jacobsen, EP; Wharton, S

    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.

  17. A multiscale eddy simulation methodology for the atmospheric Ekman boundary layer

    NASA Astrophysics Data System (ADS)

    Alam, Jahrul; Rokibul Islam, Mo

    2015-01-01

    In a large eddy simulation (LES), resolving the wide spectrum of large turbulent eddies from O(m) to O(km) in the atmospheric boundary layer (ABL) requires O(109) computational degrees of freedom; however, these eddies are intermittent in space and time. In this research, we take advantage of the spatial intermittency in a neutrally stratified atmospheric Ekman boundary layer, and study the development of a novel LES methodology. Using the second generation wavelet transform, the proposed model filters the large eddies into distinct groups of significant and insignificant eddies. We show that the significant eddies are sufficient to resolve the physics of the flow. The effects of insignificant eddies are modelled with the proposed multiscale parameterization scheme. The results of the proposed model have been found to be in good agreement with that of an equivalent reference model, experimental data, and asymptotic boundary layer theory. We have found that the number of significant eddies in a neutrally stratified ABL is much lower than the number of resolved eddies in a reference model. The overall algorithm is asymptotically optimal - the CPU time is approximately proportional to the number of resolved eddies. The proposed methodology suggests a potentially novel research direction that may be employed to address a number of computational challenges that must be faced in the field of atmospheric modeling.

  18. Distribution and escape of the major neutral species from Titan's atmosphere

    NASA Astrophysics Data System (ADS)

    Tenishev, Valeriy; Tucker, Orenthal; Borovikov, Dmitry; Combi, Michael R.

    2016-10-01

    Titan possesses the most significant atmosphere among all satellites in the Solar system, and is an important source of material for the Saturn's magnetosphere. Understanding of the neutral species distribution and escape is important for further understanding of the Titan's atmosphere evolution and loss.The first in situ observations of the Titan's atmosphere were performed by Voyager and continued by Cassini, which measured the atmospheric composition, velocity and temperature, as well as the energy spectra of neutral species, ions and electrons. Analysis and interpretation of the acquired data involves coupled modeling of the Saturn magnetosphere and Titan's atmosphere.Having that in mind we have undertaken numerical modeling of the major neutral species (N2 and CH4) in Titan's upper atmosphere to investigate the effect of the solar EUV and magnetospheric ion energy deposition on the neutral species atmospheric distribution and escape. This modeling combines MHD simulation of the Saturn's magnetosphere plasma interacting with Titan's atmosphere, fluid type simulation of the neutral species in Titan's lower atmosphere, and kinetic modeling of the upper atmosphere and exosphere. Here we present estimations of the neutral species escape rate, and discuss the effect of the magnetospheric ion energy deposition on the atmospheric escape concluded from the results of our modeling.This work was supported by NASA Outer Planet Research grant NNX13AL04G.

  19. Radio occultation measurements of Pluto's neutral atmosphere with New Horizons

    NASA Astrophysics Data System (ADS)

    Hinson, D. P.; Linscott, I. R.; Young, L. A.; Tyler, G. L.; Stern, S. A.; Beyer, R. A.; Bird, M. K.; Ennico, K.; Gladstone, G. R.; Olkin, C. B.; Pätzold, M.; Schenk, P. M.; Strobel, D. F.; Summers, M. E.; Weaver, H. A.; Woods, W. W.

    2017-07-01

    On 14 July 2015 New Horizons performed a radio occultation (RO) that sounded Pluto's atmosphere down to the surface. The sensitivity of the measurements was enhanced by a unique configuration of ground equipment and spacecraft instrumentation. Signals were transmitted simultaneously by four antennas of the NASA Deep Space Network, each radiating 20 kW at a wavelength of 4.2 cm. The polarization was right circular for one pair of signals and left circular for the other pair. New Horizons received the four signals and separated them by polarization for processing by two independent receivers, each referenced to a different ultra-stable oscillator. The two data streams were digitized, filtered, and stored on the spacecraft for later transmission to Earth. The results reported here are the first to utilize the complete set of observations. We calibrated each signal to remove effects not associated with Pluto's atmosphere, including the limb diffraction pattern. We then applied a specialized method of analysis to retrieve profiles of number density, pressure, and temperature from the combined phase measurements. Occultation entry sounded the atmosphere at sunset at 193.5°E, 17.0°S - on the southeast margin of an ice-filled basin known informally as Sputnik Planitia (SP); occultation exit occurred at sunrise at 15.7°E, 15.1°N - near the center of the Charon-facing hemisphere. Above 1215 km radius (∼25 km altitude) there is no discernible difference between the measurements at entry and exit, and the RO profiles are consistent with results derived from ground-based stellar occultation measurements. At lower altitudes the RO measurements reveal horizontal variations in atmospheric structure that had not been observed previously, and they are the first to reach the ground. The entry profile has a strong temperature inversion that ends 3.5 km above the surface, and the temperature in the cold boundary layer beneath the inversion is nearly constant, 38.9 ± 2.1 K, and

  20. Atmospheric boundary layer evening transitions over West Texas

    USDA-ARS?s Scientific Manuscript database

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

  1. Atmospheric boundary layer studies in FIFE - Challenges and advances

    NASA Technical Reports Server (NTRS)

    Kelly, Robert D.

    1992-01-01

    A review is presented of a number of other articles concerning the atmospheric boundary layer (ABL) that focus on challenges and progress in experimental design and analysis represented by those studies. The articles address problems posed by the experimental site itself (inhomogeneity of terrain, size, and vegetation) and examine relationships between the ABL and remote sensing measurements.

  2. Electrodynamic properties and height of atmospheric convective boundary layer

    NASA Astrophysics Data System (ADS)

    Anisimov, S. V.; Galichenko, S. V.; Mareev, E. A.

    2017-09-01

    We consider the relations between the mixed layer height and atmospheric electric parameters affected by convective mixing. Vertical turbulent transport of radon, its progeny and electrically charged particles is described under Lagrangian stochastic framework, which is the next step to develop a consistent model for the formation of electrical conditions in the atmospheric boundary layer. Using the data from detailed and complex measurements of vertical profiles of the temperature and turbulence statistics as input, we calculated non-stationary vertical profiles of radon and its daughter products concentrations, atmospheric electric conductivity and intensity of electric field in the convective boundary layer from the morning transition through early afternoon quasi-stationary conditions. These profiles demonstrate substantial variability due to the changing turbulent regime in the evolving boundary layer. We obtained quantitative estimates of the atmospheric electric field variability range essentially related to the sunrise and convection development. It is shown that the local change in the electrical conductivity is the only factor that can change the intensity of electric field at the earth's surface more than twice during the transition from night to day. The established relations between electric and turbulent parameters of the boundary layer indicate that the effect of sunrise is more pronounced in the case when development of convection is accompanied by an increase in aerosol concentration and, hence, a decrease in local conductivity.

  3. Modelling the Neutral Atmosphere and Plasma Environment of Saturn

    NASA Technical Reports Server (NTRS)

    Richardson, John D.; Jurac, S.; Johnson, R.; McGrath, M.

    2005-01-01

    The first year of this contract has resulted in two publications with the P.I. and co-I Jurac as lead authors and two publications where these team members are co-authors. These papers discuss modeling work undertaken in preparation for Cassini; the goal was to summarize our current best knowledge of the ion and neutrals sources and distributions. One of the major goals of this project is to improve models of the plasma and neutral environment near Saturn. The paper "A self-consistent model of plasma and neutrals at Saturn: Neutral cloud morphology" [Jurac and Richardson, 20051 presents results on the neutral clouds near Saturn using a model which for the first times treats the ions and neutrals self-consistently. We also for the first time include a directly sputtered H source. The Voyager and HST observations are used as model constraints. The neutral source is adjusted to give a good match to the HST observations of OH. For this initial run the ion parameters from Richardson et al. are used; charge exchange with ions is a major neutral loss process. The neutral profile derived from the model is then used in a model of plasma transport and chemistry (with the plasma diffusion rate the only free parameter). This model gives new values of the ion composition which are then fed back into the neutral model. This iteration continues until the values converge.

  4. Atmospheric boundary layer processes during a total solar eclipse

    SciTech Connect

    SethuRaman, S.; Prabhu, A.; Narahari Rao, K.; Narasimha, R.

    1980-01-01

    The total solar eclipse that occurred over the southern part of India on February 16, 1980, gave a unique opportunity to study the earth's atmospheric boundary layer. The meteorological experiments during the 1980 solar eclipse were conducted at Raichur, India (16/sup 0/12'N, 77/sup 0/21'E) located in the state of Karnataka, approximately 400-m above sea level. The main objective was to determine the changes in the earth's atmosphere during and immediately after the eclipse. The goal was to study the changes in the momentum and heat fluxes in the boundary layer due to the eclipse. Measurements were made for 2 days prior to and 1 day after the day of the eclipse to determine background characteristics of the boundary layer which might be site-dependent.

  5. Measurements and Modelling of the Wind Speed Profile in the Marine Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Peña, Alfredo; Gryning, Sven-Erik; Hasager, Charlotte B.

    2008-12-01

    We present measurements from 2006 of the marine wind speed profile at a site located 18 km from the west coast of Denmark in the North Sea. Measurements from mast-mounted cup anemometers up to a height of 45 m are extended to 161 m using LiDAR observations. Atmospheric turbulent flux measurements performed in 2004 with a sonic anemometer are compared to a bulk Richardson number formulation of the atmospheric stability. This is used to classify the LiDAR/cup wind speed profiles into atmospheric stability classes. The observations are compared to a simplified model for the wind speed profile that accounts for the effect of the boundary-layer height. For unstable and neutral atmospheric conditions the boundary-layer height could be neglected, whereas for stable conditions it is comparable to the measuring heights and therefore essential to include. It is interesting to note that, although it is derived from a different physical approach, the simplified wind speed profile conforms to the traditional expressions of the surface layer when the effect of the boundary-layer height is neglected.

  6. Effect of Large Finite-Size Wind Farms and Their Wakes on Atmospheric Boundary Layer Dynamics

    NASA Astrophysics Data System (ADS)

    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.

  7. Particle motion in atmospheric boundary layers of Mars and Earth

    NASA Technical Reports Server (NTRS)

    White, B. R.; Iversen, J. D.; Greeley, R.; Pollack, J. B.

    1975-01-01

    To study the eolian mechanics of saltating particles, both an experimental investigation of the flow field around a model crater in an atmospheric boundary layer wind tunnel and numerical solutions of the two- and three-dimensional equations of motion of a single particle under the influence of a turbulent boundary layer were conducted. Two-dimensional particle motion was calculated for flow near the surfaces of both Earth and Mars. For the case of Earth both a turbulent boundary layer with a viscous sublayer and one without were calculated. For the case of Mars it was only necessary to calculate turbulent boundary layer flow with a laminar sublayer because of the low values of friction Reynolds number; however, it was necessary to include the effects of slip flow on a particle caused by the rarefied Martian atmosphere. In the equations of motion the lift force functions were developed to act on a single particle only in the laminar sublayer or a corresponding small region of high shear near the surface for a fully turbulent boundary layer. The lift force functions were developed from the analytical work by Saffman concerning the lift force acting on a particle in simple shear flow.

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

    NASA Technical Reports Server (NTRS)

    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.

  9. Mean horizontal wind profiles measured in the atmospheric boundary layer about a simulated block building

    NASA Technical Reports Server (NTRS)

    Frost, W.; Connell, J. R.; Hutto, M. L.; Fichtl, G.

    1977-01-01

    Instrumented wind towers are used to measure the three components of wind about a simulated block building. The mean horizontal wind profiles over the building are compared with wind profiles measured in the absence of the building and the wind speed deficit in the wake of the building is correlated. The turbulence intensity is of the order of 20% in the undisturbed flow whereas the free stream turbulence intensity of wind-tunnel studies is generally not more than 5%. The velocity profiles measured in the undisturbed flow zones support the representation of a neutrally stable atmospheric boundary layer with a logarithmic wind profile.

  10. Large-scale intermittency in the atmospheric boundary layer.

    PubMed

    Kholmyansky, M; Moriconi, L; Tsinober, A

    2007-08-01

    We find actual evidence, relying upon vorticity time series taken in a high-Reynolds-number atmospheric experiment, that to a very good approximation the surface boundary layer flow may be described, in a statistical sense and under certain regimes, as an advected ensemble of homogeneous turbulent systems, characterized by a log-normal distribution of fluctuating intensities. Our analysis suggests that the usual direct numerical simulations of homogeneous and isotropic turbulence, performed at moderate Reynolds numbers, may play an important role in the study of turbulent boundary layer flows, if supplemented with appropriate statistical information concerned with the structure of large-scale fluctuations.

  11. Crossing the Boundaries in Planetary Atmospheres - From Earth to Exoplanets

    NASA Technical Reports Server (NTRS)

    Simon-Miller, Amy A.; Genio, Anthony Del

    2013-01-01

    The past decade has been an especially exciting time to study atmospheres, with a renaissance in fundamental studies of Earths general circulation and hydrological cycle, stimulated by questions about past climates and the urgency of projecting the future impacts of humankinds activities. Long-term spacecraft and Earth-based observation of solar system planets have now reinvigorated the study of comparative planetary climatology. The explosion in discoveries of planets outside our solar system has made atmospheric science integral to understanding the diversity of our solar system and the potential habitability of planets outside it. Thus, the AGU Chapman Conference Crossing the Boundaries in Planetary Atmospheres From Earth to Exoplanets, held in Annapolis, MD from June 24-27, 2013 gathered Earth, solar system, and exoplanet scientists to share experiences, insights, and challenges from their individual disciplines, and discuss areas in which thinking broadly might enhance our fundamental understanding of how atmospheres work.

  12. Turbulent transport in the atmospheric boundary layer with application to wind farm dynamics

    NASA Astrophysics Data System (ADS)

    Waggy, Scott B.

    With the recent push for renewable energy sources, wind energy has emerged as a candidate to replace some of the power produced by traditional fossil fuels. Recent studies, however, have indicated that wind farms may have a direct effect on local meteorology by transporting water vapor away from the Earth's surface. Such turbulent transport could result in an increased drying of soil, and, in turn, negatively affect the productivity of land in the wind farm's immediate vicinity. This numerical study will analyze four scenarios with the goal of understanding turbulence transport in the wake of a turbine: the neutrally-stratified boundary layer with system rotation, the unstably-stratified atmospheric boundary layer, and wind turbine simulations of these previous two cases. For this work, the Ekman layer is used as an approximation of the atmospheric boundary layer and the governing equations are solved using a fully-parallelized direct numerical simulation (DNS). The in-depth studies of the neutrally and unstably-stratified boundary layers without introducing wind farm effects will act to provide a concrete background for the final study concerning turbulent transport due to turbine wakes. Although neutral stratification rarely occurs in the atmospheric boundary layer, it is useful to study the turbulent Ekman layer under such conditions as it provides a limiting case when unstable or stable stratification are weak. In this work, a thorough analysis was completed including turbulent statistics, velocity and pressure autocorrelations, and a calculation of the full turbulent energy budget. The unstably-stratified atmospheric boundary layer was studied under two levels of heating: moderate and vigorous. Under moderate stratification, both buoyancy and shearing contribute significantly to the turbulent dynamics. As the level of stratification increases, the role of shearing is shown to diminish and is confined to the near-wall region only. A recent, multi

  13. Large eddy simulation for atmospheric boundary layer flow over flat and complex terrains

    NASA Astrophysics Data System (ADS)

    Han, Yi; Stoellinger, Michael; Naughton, Jonathan

    2016-09-01

    In this work, we present Large Eddy Simulation (LES) results of atmospheric boundary layer (ABL) flow over complex terrain with neutral stratification using the OpenFOAM-based simulator for on/offshore wind farm applications (SOWFA). The complete work flow to investigate the LES for the ABL over real complex terrain is described including meteorological-tower data analysis, mesh generation and case set-up. New boundary conditions for the lateral and top boundaries are developed and validated to allow inflow and outflow as required in complex terrain simulations. The turbulent inflow data for the terrain simulation is generated using a precursor simulation of a flat and neutral ABL. Conditionally averaged met-tower data is used to specify the conditions for the flat precursor simulation and is also used for comparison with the simulation results of the terrain LES. A qualitative analysis of the simulation results reveals boundary layer separation and recirculation downstream of a prominent ridge that runs across the simulation domain. Comparisons of mean wind speed, standard deviation and direction between the computed results and the conditionally averaged tower data show a reasonable agreement.

  14. Immersed Boundary Methods for High-Resolution Simulation of Atmospheric Boundary-Layer Flow Over Complex Terrain

    SciTech Connect

    Lundquist, K A

    2010-05-12

    use of flux (non-zero) boundary conditions. This anabatic flow set-up is further coupled to atmospheric physics parameterizations, which calculate surface fluxes, demonstrating that the IBM can be coupled to various land-surface parameterizations in atmospheric models. Additionally, the IB method is extended to three dimensions, using both trilinear and inverse distance weighted interpolations. Results are presented for geostrophic flow over a three-dimensional hill. It is found that while the IB method using trilinear interpolation works well for simple three-dimensional geometries, a more flexible and robust method is needed for extremely complex geometries, as found in three-dimensional urban environments. A second, more flexible, immersed boundary method is devised using inverse distance weighting, and results are compared to the first IBM approach. Additionally, the functionality to nest a domain with resolved complex geometry inside of a parent domain without resolved complex geometry is described. The new IBM approach is used to model urban terrain from Oklahoma City in a one-way nested configuration, where lateral boundary conditions are provided by the parent domain. Finally, the IB method is extended to include wall model parameterizations for rough surfaces. Two possible implementations are presented, one which uses the log law to reconstruct velocities exterior to the solid domain, and one which reconstructs shear stress at the immersed boundary, rather than velocity. These methods are tested on the three-dimensional canonical case of neutral atmospheric boundary layer flow over flat terrain.

  15. A Kinetic Study of the Gas Phase Neutral-Neutral Reactions Between Sulfur- and Chlorine-Containing Molecules Present in the Atmosphere of Venus

    NASA Astrophysics Data System (ADS)

    Maffucci, D. M.; Woon, D. E.; Herbst, E.

    2017-05-01

    Using updated electronic structures, we employ a variety of kinetic theories to calculate the reaction rate constants for neutral-neutral chemical reactions between sulfur- and chlorine-containing molecules observed in the atmosphere of Venus.

  16. Atmospheric tides on Venus. III - The planetary boundary layer

    NASA Technical Reports Server (NTRS)

    Dobrovolskis, A. R.

    1983-01-01

    Diurnal solar heating of Venus' surface produces variable temperatures, winds, and pressure gradients within a shallow layer at the bottom of the atmosphere. The corresponding asymmetric mass distribution experiences a tidal torque tending to maintain Venus' slow retrograde rotation. It is shown that including viscosity in the boundary layer does not materially affect the balance of torques. On the other hand, friction between the air and ground can reduce the predicted wind speeds from about 5 to about 1 m/sec in the lower atmosphere, more consistent with the observations from Venus landers and descent probes. Implications for aeolian activity on Venus' surface and for future missions are discussed.

  17. The Neutral Gas and Ion Mass Spectrometer on the Mars Atmosphere and Volatile Evolution Mission

    NASA Astrophysics Data System (ADS)

    Mahaffy, Paul R.; Benna, Mehdi; King, Todd; Harpold, Daniel N.; Arvey, Robert; Barciniak, Michael; Bendt, Mirl; Carrigan, Daniel; Errigo, Therese; Holmes, Vincent; Johnson, Christopher S.; Kellogg, James; Kimvilakani, Patrick; Lefavor, Matthew; Hengemihle, Jerome; Jaeger, Ferzan; Lyness, Eric; Maurer, John; Melak, Anthony; Noreiga, Felix; Noriega, Marvin; Patel, Kiran; Prats, Benito; Raaen, Eric; Tan, Florence; Weidner, Edwin; Gundersen, Cynthia; Battel, Steven; Block, Bruce P.; Arnett, Ken; Miller, Ryan; Cooper, Curt; Edmonson, Charles; Nolan, J. Thomas

    2015-12-01

    The Neutral Gas and Ion Mass Spectrometer (NGIMS) of the Mars Atmosphere and Volatile Evolution Mission (MAVEN) is designed to measure the composition, structure, and variability of the upper atmosphere of Mars. The NGIMS complements two other instrument packages on the MAVEN spacecraft designed to characterize the neutral upper atmosphere and ionosphere of Mars and the solar wind input to this region of the atmosphere. The combined measurement set is designed to quantify atmosphere escape rates and provide input to models of the evolution of the martian atmosphere. The NGIMS is designed to measure both surface reactive and inert neutral species and ambient ions along the spacecraft track over the 125-500 km altitude region utilizing a dual ion source and a quadrupole analyzer.

  18. The Neutral Gas and Ion Mass Spectrometer on the Mars Atmosphere and Volatile Evolution Mission

    NASA Technical Reports Server (NTRS)

    Mahaffy, Paul R.; Benna, Mehdi; King, Todd; Harpold, Daniel N.; Arvey, Robert; Barciniak, Michael; Bendt, Mirl; Carrigan, Daniel; Errigo, Therese; Holmes, Vincent; Kellogg, James; Jaeger, Ferzan; Raaen, Eric; Tan, Florence

    2014-01-01

    The Neutral Gas and Ion Mass Spectrometer (NGIMS) of the Mars Atmosphere and Volatile Evolution Mission (MAVEN) is designed to measure the composition, structure, and variability of the upper atmosphere of Mars. The NGIMS complements two other instrument packages on the MAVEN spacecraft designed to characterize the neutral upper atmosphere and ionosphere of Mars and the solar wind input to this region of the atmosphere. The combined measurement set is designed to quantify atmosphere escape rates and provide input to models of the evolution of the martian atmosphere. The NGIMS is designed to measure both surface reactive and inert neutral species and ambient ions along the spacecraft track over the 125-500 km altitude region utilizing a dual ion source and a quadrupole analyzer.

  19. Proceedings of the Atmospheric Neutral Density Specialist Conference, Held in Colorado Springs, Colorado on March 22-23, 1988

    DTIC Science & Technology

    1988-03-23

    PROCEEDINGS OF THE ATMOSPHERIC NEUTRAL DENSITY SPECIALIST CONFERENCE Lf) cN HELD AT THE RAINTREE INN, AIRPORT COLORADO SPRINGS, COLORADO 22 - 23...Lt Col George R. Davenport Headquarters Fourth Weather Wing Air Weather Service Neutral Atmospheric Modeling Requirements...5 Captain Chris R. Tschan HO AWS/DNXP Air Force Space Command Requiremnents for Neutral Atmospheric Density Specification and

  20. Turbulence and mixing in the stable atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Yagüe, C.; Morales, G.; Terradellas, E.; Cuxart, J.

    2003-04-01

    Transport and mixing in the Stable Atmospheric Boundary Layer is not well understood yet. However this is an important feature in atmospheric pollution as well as in other environmental studies. A Stable Atmospheric Boundary Layer Experiment in Spain (SABLES98) took place from the 10th to the 28th of September 1998. Two masts (100 m and 10 m) were instrumented with five sonic anemometers, 14 thermocouples, 8 cup anemometers, vanes,radiometers, etc. In addition, a sodar, a tethered balloon and a triangular array of cup anemometers were operating during the campaign. The experiment showed three different regimes, being specially interesting the one between 14th and 21st of September where stable and very stable conditions were present. In this work we present the behaviour of turbulent and stability parameters at several heights. The different evolutions of the Nocturnal Boundary Layer and the main parameters that controle its behaviour are discussed.The influence of internal gravity waves and their interaction with turbulence is also studied using wavelets.

  1. Surface fluxes in atmospheric boundary layer flows over complex terrain

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Markfort, Corey; Porté-Agel, Fernando

    2016-11-01

    Interactions between the atmosphere and the land/water surface can be described by fluxes of momentum, heat and other scalars. While predicting the atmospheric boundary-layer (ABL) flows and modeling regional/global weather and climate, these surface fluxes need to be specified as boundary conditions. It is a common practice to use formulations based on the Monin-Obukhov similarity theory even for flows over a wide range of complex terrain, which maybe deviate significantly from the conditions of steady, fully-developed ABL flow, due to the knowledge gap for turbulent transport of fluxes across the interface. This work aims to provide insights for spatial distribution of the surface fluxes in ABL flows involving typical complex terrain cases, including surface roughness transition, steep topography and canopy patches. Results from wind-tunnel experiments will be presented to characterize the surface momentum and heat fluxes for different flow regimes and their correlation to the turbulent flow properties in thermally-stratified boundary layers. Application of the similarity theory to such cases is evaluated by comparing to the measurements. Ultimately, new knowledge of surface fluxes will help to improve parameterization of the surface-atmosphere interaction in numerical models.

  2. Dynamic Turbulence Modelling in Large-eddy Simulations of the Cloud-topped Atmospheric Boundary Layer

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    The use of large eddy simulation, or LES, to study the atmospheric boundary layer dates back to the early 1970s when Deardor (1972) used a three-dimensional simulation to determine velocity and temperature scales in the convective boundary layer. In 1974 he applied LES to the problem of mixing layer entrainment (Deardor 1974) and in 1980 to the cloud-topped boundary layer (Deardor 1980b). Since that time the LES approach has been applied to atmospheric boundary layer problems by numerous authors. While LES has been shown to be relatively robust for simple cases such as a clear, convective boundary layer (Mason 1989), simulation of the cloud-topped boundary layer has proved more of a challenge. The combination of small length scales and anisotropic turbulence coupled with cloud microphysics and radiation effects places a heavy burden on the turbulence model, especially in the cloud-top region. Consequently, over the past few decades considerable effort has been devoted to developing turbulence models that are better able to parameterize these processes. Much of this work has involved taking parameterizations developed for neutral boundary layers and deriving corrections to account for buoyancy effects associated with the background stratification and local buoyancy sources due to radiative and latent heat transfer within the cloud (see Lilly 1962; Deardor 1980a; Mason 1989; MacVean & Mason 1990, for example). In this paper we hope to contribute to this effort by presenting a number of turbulence models in which the model coefficients are calculated dynamically during the simulation rather than being prescribed a priori.

  3. Strange drift of passive tracers from horizontal blowing out sources in the atmospheric boundary layer

    SciTech Connect

    Koeltzsch, K.

    1995-12-31

    In the past many scientists running a wind tunnel observed the following strange phenomenon. Plumes blowing out from horizontal sources (with the same momentum as the adjacent flow) and located inside the planar boundary layer, drift stronger towards the ground than described physically by the conventional dispersion equation. This effect occurs clearly in regard to greater surface roughness. If the dispersion by Gauss is used in connection with a term of reflection, the descending of a plume only occurs after the reflection of tracers on the surface, contrary to the observations. On the other hand a dispersion model is used to describe this phenomenon, which depends on height diffusivity coefficients and a power law for the mean velocity profile (Berljand, 1982; Smith, 1957). The aim of the investigation is to provide a contribution to the causes for this phenomenon. The influence of the roughness length is explored more closely for the above named model. The paper studies the properties of basic flow inside the atmospheric boundary layer generated by a wind tunnel with an open test section. The neutral atmosphere over a suburb terrain is modeled. The following presents measurements by hot-wire with a four-wire-probe of the higher, statistical moments related to all three velocities and measurements of concentration by a Flame-Ionization-Detector in an atmospheric boundary layer of the model. In this connection it is of special interest to investigate the skewness of vertical velocity. This quantity is important for the Lagrangian dispersion model.

  4. ROSCOE Manual, Volume 14A-1 - Ambient Atmosphere (Major and Minor Neutral Species and Ionosphere).

    DTIC Science & Technology

    1979-06-30

    ROSCOE Minor Neutral Species Ambient Atmospheric Model Charged Species Ambient Ionospheric Model Major Neutral Species 20 ABSTRACT (Continue ion...reverse side if necessary arnd Identify by blockt number) The ROSCOE-Radar ambient atmosphere model has been extensively revised to provide (a) major... MODEL FOR ROSCOE-IR--------- 16 2-2.1 Background ---------------------------------- 16 2-2.2 Kinetic Temperature Data and Interpolation-- 21 2-2.2.1

  5. Study of the morning transition of the atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Sastre, M.; Yagüe, C.; Maqueda, G.; Viana, S.

    2009-04-01

    In this work it will be analyzed the main physical processes related to the transition of the Atmospheric Boundary Layer (ABL) that takes place from the last hours of the night until the first hours of the morning. In order to achieve that, it will be used data from field campaigns which took place in the Research Centre for the Lower Atmosphere (CIBA), especially those gathered in the campaign carried out in June, 2008 where information was obtained from a 10m height mast provided with temperature, wind speed and direction, and moisture sensors at several levels. Also a sonic anemometer (20 Hz sampling rate) at 10m was available. The database is complemented by a triangle of microbarometers installed next to the surface, and another two microbarometers placed in a 100m meteorological tower at 50 and 100m respectively. A GRIMM particle monitor (MODEL 365), which can be used to continuously measure each six seconds simultaneously the PM10, PM2.5 and PM1 values, was also available to evaluate the degree of mixing taking place near the surface. The thermodynamic characteristics of the first hundreds of meters remain registered from information obtained with a tethered balloon and with a RASS-SODAR. The main turbulent and stability parameters, as well as coherent structures present in the Nocturnal Boundary Layer are studied in connection to their influence in the developing of the next Convective Boundary Layer.

  6. A helicopter observation platform for atmospheric boundary layer studies

    NASA Astrophysics Data System (ADS)

    Holder, Heidi Eichinger

    HOP data collected using the current set of sensors is discussed, including the novel use of the Empirical Mode Decomposition (EMD) to detrend and filter the data. The EMD separates the data into a finite number of Intrinsic Mode Functions (IMFs), each of which is unique and orthogonal. The basis is determined by the data itself, so that it need not be known a priori, and it is adaptive. The EMD is shown to be an ideal tool for the filtering and detrending of the HOP data gathered during the Cloud and Land Surface Interaction Campaign (CLASIC). The ability of the HOP to accurately measure atmospheric profiles of atmospheric variables is demonstrated. During experiments conducted in the marine boundary layer (MBL) and the convective boundary layer (CBL), HOP profiles of potential temperature are evaluated using an elastic backscatter lidar. The HOP and the lidar agree on the height of the boundary layer in both cases, and the HOP effectively locates other atmospheric structures. Atmospheric sensible and latent heat fluxes, turbulence kinetic energy (TKE) and horizontal momentum fluxes are also measured, and the resulting information is used to provide context to tower-based data collected concurrently. A brief comparison made over homogeneous ocean conditions yields good results. A more exhaustive evaluation is made using short HOP flights performed above an orchard during the Canopy Horizontal Turbulence Study (CHATS). Randomly selected one-minute sections of tower data are used to calculate fluxes to which the HOP fluxes can be more directly compared, with good results. Profiles of atmospheric fluxes are used to provide context to tower-based measurements. In conclusion, the research conducted here demonstrates unambiguously that the HOP is a unique platform that fills an important gap in observation facilities for the atmospheric boundary layer. It is now available to the scientific community for performing research, which is likely to help bridging existing

  7. Linking atmospheric composition data across data types and national boundaries

    NASA Astrophysics Data System (ADS)

    Schultz, Martin; Lyapina, Olga; Schröder, Sabine; Stein, Olaf; Mallmann, Daniel

    2016-04-01

    The field of atmospheric composition research involves the management of data sources from various disciplines such as meteorology, chemistry, (radiation) physics, emission inventories, etc. The output from global and regional chemistry climate models, chemistry transport models, and air quality models presents considerable challenges due to the manifold variables of interest and the multitude of diagnostics needed in order to interpret the results. Furthermore, many observations of atmospheric composition exist from different platforms involving different geometries, time resolutions, size spectra, etc. Due to the fact that few observation networks are globally coordinated, various representations of data formats and metadata definitions exist. For example, there is no unique agreement on chemical species names and in many networks, national languages are used to document the data. We will present a summary of the issues involving global interoperability of atmospheric composition data including the aspects of data volume, data compexity and metadata standardisation, and we will demonstrate various activities carried out in Jülich and internationally to overcome these challenges. Specifically, we will describe the current implementation and plans for the Copernicus Atmosphere Monitoring Service boundary condition service (http://ows-server.iek.fz-juelich.de), the design of the JOIN web interface (https://join.fz-juelich.de), and the activities for building an ontology of atmospheric composition vocabulary (https://ontology.geodab.eu/).

  8. Lidar analysis techniques for use in the atmospheric boundary layer

    NASA Technical Reports Server (NTRS)

    Eichinger, William E.; Cooper, Daniel I.; Hof, Doug; Holtkamp, David; Quick, Robert, Jr.; Tiee, Joe; Karl, Robert

    1992-01-01

    There is a growing body of observational and theoretical evidence which suggests that local climate characteristics are associated with variations in the earth's surface. The link between surface variability and local-scale processes must be made if we are to improve our understanding of the feedback mechanisms involved in surface-atmosphere dynamics. However, to understand these interactions, the surface-atmosphere interface must be studied as a large-scale spatial system. Lidars are ideal tools to study the spatial properties of the atmosphere. The described techniques were developed for use with the Los Alamos Water Raman-Lidar, but are applicable to many other types of lidar. The methodology of the analysis of lidar data is summarized in order to determine meteorological parameters in the atmospheric boundary layer. The techniques are not exhaustive but are intended to show the depth and breadth of the information which can be obtained from lidars. Two methods for the computation of water-vapor fluxes were developed. The first uses the fact that the water vapor concentration in the vertical direction follows a logarithmic profile when corrected for atmospheric stability. The second method involves using inertial dissipation techniques in which lidar-derived spatial and temporal power spectra are used to determine the flux.

  9. Lidar analysis techniques for use in the atmospheric boundary layer

    NASA Technical Reports Server (NTRS)

    Eichinger, William E.; Cooper, Daniel I.; Hof, Doug; Holtkamp, David; Quick, Robert, Jr.; Tiee, Joe; Karl, Robert

    1992-01-01

    There is a growing body of observational and theoretical evidence which suggests that local climate characteristics are associated with variations in the earth's surface. The link between surface variability and local-scale processes must be made if we are to improve our understanding of the feedback mechanisms involved in surface-atmosphere dynamics. However, to understand these interactions, the surface-atmosphere interface must be studied as a large-scale spatial system. Lidars are ideal tools to study the spatial properties of the atmosphere. The described techniques were developed for use with the Los Alamos Water Raman-Lidar, but are applicable to many other types of lidar. The methodology of the analysis of lidar data is summarized in order to determine meteorological parameters in the atmospheric boundary layer. The techniques are not exhaustive but are intended to show the depth and breadth of the information which can be obtained from lidars. Two methods for the computation of water-vapor fluxes were developed. The first uses the fact that the water vapor concentration in the vertical direction follows a logarithmic profile when corrected for atmospheric stability. The second method involves using inertial dissipation techniques in which lidar-derived spatial and temporal power spectra are used to determine the flux.

  10. Wake Dynamics in the Atmospheric Boundary Layer Over Complex Terrain

    NASA Astrophysics Data System (ADS)

    Markfort, Corey D.

    The goal of this research is to advance our understanding of atmospheric boundary layer processes over heterogeneous landscapes and complex terrain. The atmospheric boundary layer (ABL) is a relatively thin (˜ 1 km) turbulent layer of air near the earth's surface, in which most human activities and engineered systems are concentrated. Its dynamics are crucially important for biosphere-atmosphere couplings and for global atmospheric dynamics, with significant implications on our ability to predict and mitigate adverse impacts of land use and climate change. In models of the ABL, land surface heterogeneity is typically represented, in the context of Monin-Obukhov similarity theory, as changes in aerodynamic roughness length and surface heat and moisture fluxes. However, many real landscapes are more complex, often leading to massive boundary layer separation and wake turbulence, for which standard models fail. Trees, building clusters, and steep topography produce extensive wake regions currently not accounted for in models of the ABL. Wind turbines and wind farms also generate wakes that combine in complex ways to modify the ABL. Wind farms are covering an increasingly significant area of the globe and the effects of large wind farms must be included in regional and global scale models. Research presented in this thesis demonstrates that wakes caused by landscape heterogeneity must be included in flux parameterizations for momentum, heat, and mass (water vapor and trace gases, e.g. CO2 and CH4) in ABL simulation and prediction models in order to accurately represent land-atmosphere interactions. Accurate representation of these processes is crucial for the predictions of weather, air quality, lake processes, and ecosystems response to climate change. Objectives of the research reported in this thesis are: 1) to investigate turbulent boundary layer adjustment, turbulent transport and scalar flux in wind farms of varying configurations and develop an improved

  11. Atmospheric boundary layer modification in the marginal ice zone

    NASA Technical Reports Server (NTRS)

    Bennett, Theodore J., Jr.; Hunkins, Kenneth

    1986-01-01

    A case study of the Andreas et al. (1984) data on atmospheric boundary layer modification in the marginal ice zone is made. The model is a two-dimensional, multilevel, linear model with turbulence, lateral and vertical advection, and radiation. Good agreement between observed and modeled temperature cross sections is obtained. In contrast to the hypothesis of Andreas et al., the air flow is found to be stable to secondary circulations. Adiabatic lifting and, at long fetches, cloud top longwave cooling, not an air-to-surface heat flux, dominate the cooling of the boundary layer. The accumulation with fetch over the ice of changes in the surface wind field is shown to have a large effect on estimates of the surface wind stress. It is speculated that the Andreas et al. estimates of the drag coefficient over the compact sea ice are too high.

  12. Atmospheric surface and boundary layers of the Amazon Basin

    NASA Technical Reports Server (NTRS)

    Garstang, Michael

    1987-01-01

    Three phases of work were performed: design of and preparation for the Amazon Boundary Layer Experiment (ABLE 2-A); execution of the ABLE 2-A field program; and analysis of the ABLE 2-A data. Three areas of experiment design were dealt with: surface based meteorological measurements; aircraft missions; and project meteorological support. The primary goal was to obtain a good description of the structure of the atmosphere immediately above the rain forest canopy (top of canopy to a few thousand meters), to describe this region during the growing daytime phase of the boundary layer; and to examine the nighttime stratified state. A secondary objective was to examine the role that deep convective storms play in the vertical transport of heat, water vapor, and other trace gases. While significant progress was made, much of the analysis remains to be done.

  13. Behaviour of Atmospheric Boundary Layer Height at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Pietroni, I.; Argentini, S.

    2009-09-01

    The Antarctic Atmospheric Boundary Layer presents characteristics which are substantially different from the mid-latitudes ABLs. On the Antarctic plateau two different extreme situations are observed. During the summer a mixing height develops during the warmer hours of the day although the sensible heat flux is reduced compared to that at mid-latitudes. During the winter a long lived stable boundary layer is continuously present, the residual layer is never observed, consequently the inversion layer is connected at the free atmosphere. To understand the stable ABL process the STABLEDC (Study of the STAble Boundary Layer Environmental at Dome C) experimental field was held at Concordia, the French Italian plateau station at Dome C, during 2005. In the same period the RMO (Routine Measurements Observations) started. The data included turbulence data at the surface, temperature profiles by a microwave profiler (MTP-5P), a mini-sodar and radio-soundings. In this work we will show the results of a comparison of the ABL height at Concordia (3233 m a.s.l) during the summer and the winter using direct measurements and parameterization. The winter ABL height was estimated directly using experimental data (radio-soundings and radiometer temperature and wind velocity profiles) and different methods proposed in literature. The stable ABL height was also estimated using the formulation proposed by Zilitinkevich et al. (2007) for the long-lived stable boundary layer. The correlation of ABL height with the temperature and wind speed is also shown. The summer mixing height was instead estimated by mini-sodar data and compared with the height given by the model suggested by Batchvarova and Gryning (1991) which use as input the turbulence data.

  14. Large-eddy simulation of particle-laden atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Ilie, Marcel; Smith, Stefan Llewellyn

    2008-11-01

    Pollen dispersion in the atmospheric boundary layer (ABL) is numerically investigated using a hybrid large-eddy simulation (LES) Lagrangian approach. Interest in prediction of pollen dispersion stems from two reasons, the allergens in the pollen grains and increasing genetic manipulation of plants leading to the problem of cross pollination. An efficient Eulerian-Lagrangian particle dispersion algorithm for the prediction of pollen dispersion in the atmospheric boundary layer is outlined. The volume fraction of the dispersed phase is assumed to be small enough such that particle-particle collisions are negligible and properties of the carrier flow are not modified. Only the effect of turbulence on particle motion has to be taken into account (one-way coupling). Hence the continuous phase can be treated separate from the particulate phase. The continuous phase is determined by LES in the Eulerian frame of reference whereas the dispersed phase is simulated in a Lagrangian frame of reference. Numerical investigations are conducted for the convective, neutral and stable boundary layer as well different topographies. The results of the present study indicate that particles with small diameter size follow the flow streamlines, behaving as tracers, while particles with large diameter size tend to follow trajectories which are independent of the flow streamlines. Particles of ellipsoidal shape travel faster than the ones of spherical shape.

  15. Three velocity component, nonhomogeneous atmospheric boundary layer turbulence modeling

    NASA Technical Reports Server (NTRS)

    Perlmutter, M.; Frost, W.; Fichtl, G. H.

    1976-01-01

    The vertical nonhomogeneous character of turbulence in the atmospheric boundary layer results in a non-stationary turbulence process relative to an aircraft during takeoff and landing despite the fact that the turbulence statistics can be horizontally homogeneous. The simulation of the three components of the turbulent winds which include the nonstationary aspect of atmospheric turbulence is the subject of this paper. A procedure is developed and demonstrated to generate the three components of a turbulence ramdom process field, u sub i(x,z) where x and z denote horizontal and vertical coordinates and u sub i, i = 1,2,3 are the three orthogonal components of the turbulent random field. This field satisfies any desired one point auto spectra as well as two point statistics (interlevel correlations). By use of Taylors frozen eddy hypothesis we can transform the turbulent random field into the time domain and obtain the random turbulence along an aircraft trajectory.

  16. Neutral Atmosphere Properties Determining D-region Electron Densities

    NASA Technical Reports Server (NTRS)

    Taubenheim, J.

    1984-01-01

    The increasing discoveries of various manifestations of meteorological control of the D region ionization and the growth of techniques for its measurement provide a challenge to meteorologists to test their insight into middle atmosphere processes with the physical interpretation of D layer phenomena. Models for ion production due to photoionization of minor atmospheric nitric oxide by quasi-monochromatic solar Lyman-alpha radiation are presented. A ground based measuring technique using low frequency radio reflection heights is briefly described and an approach to the interpretation of data acquired by this method is discussed. It is shown that D region electron density variations can provide an efficient diagnostic tool for the detection of perturbations of the circulation state of the middle atmosphere.

  17. Wind turbine wakes in forest and neutral plane wall boundary layer large-eddy simulations

    NASA Astrophysics Data System (ADS)

    Schröttle, Josef; Piotrowski, Zbigniew; Gerz, Thomas; Englberger, Antonia; Dörnbrack, Andreas

    2016-09-01

    Wind turbine wake flow characteristics are studied in a strongly sheared and turbulent forest boundary layer and a neutral plane wall boundary layer flow. The reference simulations without wind turbine yield similar results as earlier large-eddy simulations by Shaw and Schumann (1992) and Porte-Agel et al. (2000). To use the fields from the homogeneous turbulent boundary layers on the fly as inflow fields for the wind turbine wake simulations, a new and efficient methodology was developed for the multiscale geophysical flow solver EULAG. With this method fully developed turbulent flow fields can be achieved upstream of the wind turbine which are independent of the wake flow. The large-eddy simulations reproduce known boundary-layer statistics as mean wind profile, momentum flux profile, and eddy dissipation rate of the plane wall and the forest boundary layer. The wake velocity deficit is more asymmetric above the forest and recovers faster downstream compared to the velocity deficit in the plane wall boundary layer. This is due to the inflection point in the mean streamwise velocity profile with corresponding turbulent coherent structures of high turbulence intensity in the strong shear flow above the forest.

  18. Cometary atmospheres: Modeling the spatial distribution of observed neutral radicals

    NASA Technical Reports Server (NTRS)

    Combi, M. R.

    1985-01-01

    Progress on modeling the spatial distributions of cometary radicals is described. The Monte Carlo particle-trajectory model was generalized to include the full time dependencies of initial comet expansion velocities, nucleus vaporization rates, photochemical lifetimes and photon emission rates which enter the problem through the comet's changing heliocentric distance and velocity. The effect of multiple collisions in the transition zone from collisional coupling to true free flow were also included. Currently available observations of the spatial distributions of the neutral radicals, as well as the latest available photochemical data were re-evaluated. Preliminary exploratory model results testing the effects of various processes on observable spatial distributions are also discussed.

  19. Major contribution of neutral clusters to new particle formation at the interface between the boundary layer and the free troposphere

    NASA Astrophysics Data System (ADS)

    Rose, C.; Sellegri, K.; Asmi, E.; Hervo, M.; Freney, E.; Colomb, A.; Junninen, H.; Duplissy, J.; Sipilä, M.; Kontkanen, J.; Lehtipalo, K.; Kulmala, M.

    2015-03-01

    The formation of new aerosol particles in the atmosphere is a key process influencing the aerosol number concentration as well as the climate, in particular at high altitude, where the newly formed particles directly influence cloud formation. However, free tropospheric new particle formation (NPF) is poorly documented due to logistic limitations and complex atmospheric dynamics around high-altitude stations that make the observation of this day-time process challenging. Recent improvements in measurement techniques make now possible the detection of neutral clusters down to ~ 1 nm sizes, which opens new horizons in our understanding of the nucleation process. Indeed, only the charged fraction of clusters has been reported in the upper troposphere up to now. Here we report day-time concentrations of charged and neutral clusters (1 to 2.5 nm mobility diameter) recorded at the interface between the boundary layer (BL) and the FT as well as in the FT at the altitude site of Puy de Dôme (1465 m a.s.l.), central France, between 10 and 29 February 2012. Our findings demonstrate that in the FT, and especially at the interface between the BL and the FT, the formation of 1.5 nm neutral clusters significantly exceeds the one of ionic clusters during NPF events, clearly indicating that they dominate in the nucleation process. We also observe that the total cluster concentration significantly increases during NPF events compared to the other days, which was not clearly observed for the charged cluster population in the past. During the studied period, the nucleation process does not seem to be sulfuric acid-limited and could be promoted by the transport of pollutants to the upper troposphere, coupled with low temperatures.

  20. Coherent Vortical Structures in the Atmospheric Boundary Layer Near Ground.

    NASA Astrophysics Data System (ADS)

    Cropley, Ford

    Available from UMI in association with The British Library. Vorticity has been fundamental to the description of turbulence. Despite this there have been few measurements of vorticity in the atmosphere. An array of twelve digital vane anemometers was used as a probe to measure atmospheric vorticity. Data was taken in neutrally stable conditions, in a range of wind speeds. The velocity vector was measured at four points at 5 or 10 Hz. The coded velocity signals were transmitted by cable for storage in a microcomputer. The assumption of linear velocity fields allowed the subsequent calculation of the local vorticity vector and the divergence. Particular care was taken with the interaction of the various length scales associated with the instrument. Characteristic spacing of the anemometers was 2m. Probability distributions and spectra of the vorticity components are calculated. A literature review examines developments in conditional sampling in controlled flows, and reviews the sparse measurements of ordered motions in the atmosphere. A conditional sampling scheme used the smoothed cross-wind vorticity component as a detector. Further partitioning of the traces using the vertical vorticity component revealed a recurring vortical structure. This appeared to be part of a system of horseshoe vortices. The work ends with a summary of findings, and recommendations for further study.

  1. Parameterization of meandering phenomenon in a stable atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Carvalho, Jonas da Costa; Degrazia, Gervásio Annes; de Vilhena, Marco Túlio; Magalhães, Sergio Garcia; Goulart, Antonio G.; Anfossi, Domenico; Acevedo, Otávio Costa; Moraes, Osvaldo L. L.

    2006-08-01

    Accounting for the current knowledge of the stable atmospheric boundary layer (ABL) turbulence structure and characteristics, a new formulation for the meandering parameters to be used in a Lagrangian stochastic particle turbulent diffusion model has been derived. That is, expressions for the parameters controlling the meandering oscillation frequency in low wind speed stable conditions are proposed. The classical expression for the meandering autocorrelation function, the turbulent statistical diffusion theory and ABL similarity theory are employed to estimate these parameters. In addition, this new parameterization was introduced into a particular Lagrangian stochastic particle model, which is called Iterative Langevin solution for low wind, validated with the data of Idaho National Laboratory experiments, and compared with others diffusion models. The results of this new approach are shown to agree with the measurements of Idaho experiments and also with those of the other atmospheric diffusion models. The major advance shown in this study is the formulation of the meandering parameters expressed in terms of the characteristic scales (velocity and length scales) describing the physical structure of a turbulent stable boundary layer. These similarity formulas can be used to simulate meandering enhanced diffusion of passive scalars in a low wind speed stable ABL.

  2. First observation of the fourth neutral polarization point in the atmosphere.

    PubMed

    Horváth, Gábor; Bernáth, Balázs; Suhai, Bence; Barta, András; Wehner, Rüdiger

    2002-10-01

    In the clear sky there are three commonly known loci, the Arago, Babinet, and Brewster neutral points, where the skylight is unpolarized. These peculiar celestial points, bearing the names of their discoverers, have been the subject of many ground-based investigations, because their positions are sensitive indicators of the amount and type of atmospheric turbidity. According to theoretical considerations and computer simulations, there should exist an additional neutral point approximately opposite to the Babinet point, which can be observed only at higher altitudes in the air or space. Until now, this anonymous "fourth" neutral point has not been observed during air- or space-borne polarimetric experiments and has been forgotten, in spite of the fact that the neutral points were a basic tool in atmospheric research for a century. Here, we report on the first observation of this fourth neutral point from a hot air balloon. Using 180 degrees-field-of-view imaging polarimetry, we could observe the fourth neutral point at 450, 550, and 650 nm from different altitudes between 900 and 3500 m during and after sunrise at approximately 22 degrees - 40 degrees below the anti-solar point along the anti-solar meridian, depending on the wavelength and solar elevation. We show that the fourth neutral point exists at the expected location and has characteristics similar to those of the Arago, Babinet, and Brewster points. We discuss why the fourth neutral point has not been observed in previous air- or space-borne polarimetric experiments.

  3. First observation of the fourth neutral polarization point in the atmosphere

    NASA Astrophysics Data System (ADS)

    Horvath, Gabor; Bernath, Balazs; Suhai, Bence; Barta, Andras; Wehner, Rudiger

    2002-10-01

    In the clear sky there are three commonly known loci, the Arago, Babinet, and Brewster neutral points, where the skylight is unpolarized. These peculiar celestial points, bearing the names of their discoverers, have been the subject of many ground-based investigations, because their positions are sensitive indicators of the amount and type of atmospheric turbidity. According to theoretical considerations and computer simulations, there should exist an additional neutral point approximately opposite to the Babinet point, which can be observed only at higher altitudes in the air or space. Until now, this anonymous fourth neutral point has not been observed during air- or space-borne polarimetric experiments and has been forgotten, in spite of the fact that the neutral points were a basic tool in atmospheric research for a century. Here, we report on the first observation of this fourth neutral point from a hot air balloon. Using 180-field-of-view imaging polarimetry, we could observe the fourth neutral point at 450, 550, and 650 nm from different altitudes between 900 and 3500 m during and after sunrise at approximately 2240 below the anti-solar point along the anti-solar meridian, depending on the wavelength and solar elevation. We show that the fourth neutral point exists at the expected location and has characteristics similar to those of the Arago, Babinet, and Brewster points. We discuss why the fourth neutral point has not been observed in previous air- or space-borne polarimetric experiments. 2002 Optical Society of America

  4. Neutral Mass Spectrometry for Venus Atmosphere and Surface

    NASA Technical Reports Server (NTRS)

    Mahaffy, Paul

    2005-01-01

    The assignment is to make precise (better than 1 %) measurements of isotope ratios and accurate (5-10%) measurements of abundances of noble gas and to obtain vertical profiles of trace chemically active gases from above the clouds all the way down to the surface. Science measurement objectives are as follows: 1) Determine the composition of Venus atmosphere, including trace gas species and light stable isotopes; 2) Accurately measure noble-gas isotopic abundance in the atmosphere; 3) Provide descent, surface, and ascent meteorological data; 4) Measure zonal cloud-level winds over several Earth days; 5) Obtain near-IR descent images of the surface from 10-km altitude to the surface; 6) Accurately measure elemental abundances & mineralogy of a core from the surface; and 7) Evaluate the texture of surface materials to constrain weathering environment.

  5. Neutral Mass Spectrometry for Venus Atmosphere and Surface

    NASA Technical Reports Server (NTRS)

    Mahaffy, Paul

    2004-01-01

    The nature of the divergent evolution of the terrestrial planets Venus, Earth, and Mars is a fundamental problem in planetary science that is most relevant to understanding the characteristics of small planets we are likely to discover in extrasolar systems and the number of such systems that may support habitable environments. For this reason, the National Research Council's Decadal Survey gives Venus exploration high priority. That report was the basis of the NASA selection of Venus as one of four prime mission targets for the recently initiated New Frontiers Program. If the Decadal Survey priorities are to be realized, in situ Venus exploration must remain a high priority. Remote sensing orbital and in situ atmospheric measurements from entry probe or balloon platforms might be realized under the low cost Discovery missions while both atmospheric and landed surface measurements are envisioned with the intermediate class missions of the New Frontiers Program.

  6. Western boundary currents in the atmosphere of Mars

    NASA Astrophysics Data System (ADS)

    Joshi, M. M.; Lewis, S. R.; Read, P. L.; Catling, D. C.

    1994-02-01

    WESTERN boundary currents (WBCs) are an intensification of north-south flow adjacent to an eastward-facing meridional boundary. Although most familiar in the oceans (where the Gulf Stream is the best known example), WBCs also occur in the Earth's troposphere, the main example being the East African Jet1, which is thought to play an important role in the Asiatic monsoon. Here we identify boundary currents in a different geophysical context: a numerical simulation of the atmosphere of Mars. In our simulation, WBCs exist in association with significant cross-equatorial flow and the presence of equatorial martian topography, which has vertical scale far exceeding terrestrial relief2. The intensity and width of these currents depend on model parameters, notably the surface drag. From a comparison of our results with other martian models we suggest that WBCs have already been simulated, although they were not previously identified as such3. The available observational evidence appears to be consistent with the presence of martian WBCs, which may be important in the generation of global and great dust storms.

  7. Impact of Neutral Boundary-Layer Turbulence on Wind-Turbine Wakes: A Numerical Modelling Study

    NASA Astrophysics Data System (ADS)

    Englberger, Antonia; Dörnbrack, Andreas

    2017-03-01

    The wake characteristics of a wind turbine in a turbulent boundary layer under neutral stratification are investigated systematically by means of large-eddy simulations. A methodology to maintain the turbulence of the background flow for simulations with open horizontal boundaries, without the necessity of the permanent import of turbulence data from a precursor simulation, was implemented in the geophysical flow solver EULAG. These requirements are fulfilled by applying the spectral energy distribution of a neutral boundary layer in the wind-turbine simulations. A detailed analysis of the wake response towards different turbulence levels of the background flow results in a more rapid recovery of the wake for a higher level of turbulence. A modified version of the Rankine-Froude actuator disc model and the blade element momentum method are tested as wind-turbine parametrizations resulting in a strong dependence of the near-wake wind field on the parametrization, whereas the far-wake flow is fairly insensitive to it. The wake characteristics are influenced by the two considered airfoils in the blade element momentum method up to a streamwise distance of 14 D ( D = rotor diameter). In addition, the swirl induced by the rotation has an impact on the velocity field of the wind turbine even in the far wake. Further, a wake response study reveals a considerable effect of different subgrid-scale closure models on the streamwise turbulent intensity.

  8. Impact of Neutral Boundary-Layer Turbulence on Wind-Turbine Wakes: A Numerical Modelling Study

    NASA Astrophysics Data System (ADS)

    Englberger, Antonia; Dörnbrack, Andreas

    2016-10-01

    The wake characteristics of a wind turbine in a turbulent boundary layer under neutral stratification are investigated systematically by means of large-eddy simulations. A methodology to maintain the turbulence of the background flow for simulations with open horizontal boundaries, without the necessity of the permanent import of turbulence data from a precursor simulation, was implemented in the geophysical flow solver EULAG. These requirements are fulfilled by applying the spectral energy distribution of a neutral boundary layer in the wind-turbine simulations. A detailed analysis of the wake response towards different turbulence levels of the background flow results in a more rapid recovery of the wake for a higher level of turbulence. A modified version of the Rankine-Froude actuator disc model and the blade element momentum method are tested as wind-turbine parametrizations resulting in a strong dependence of the near-wake wind field on the parametrization, whereas the far-wake flow is fairly insensitive to it. The wake characteristics are influenced by the two considered airfoils in the blade element momentum method up to a streamwise distance of 14D (D = rotor diameter). In addition, the swirl induced by the rotation has an impact on the velocity field of the wind turbine even in the far wake. Further, a wake response study reveals a considerable effect of different subgrid-scale closure models on the streamwise turbulent intensity.

  9. Neutral and charged clusters in the atmosphere: their importance and potential role in heterogeneous catalysis

    SciTech Connect

    Castleman, A.W. Jr.

    1982-01-01

    Extensive investigations of the bonding of atmospherically important molecules to various ions have been made, and the results are used to clarify the overall gas-to-particle conversion process involving a single ionic species. Neutral and charged clusters play an important role in atmospheric processes, and an understanding of their states and reactivity is essential in developing a fundamental understanding and basis for assessing the importance of heterogeneous processes. The purpose of this paper is to survey briefly the current knowledge in these various fields and to recommend studies needed for further progress in quantifying aerosol formation and catalytic reactivity. The topics surveyed include clusters between ions and molecules and among neutral molecules, bonding and stability of small neutral-neutral complexes and related charge transfer complexes, and gas-to-particle conversion. 92 references, 5 figures, 2 tables.

  10. High resolution properties of the marine atmospheric boundary layer

    SciTech Connect

    Cooper, D.; Cottingame, W.; Eichinger, W.; Forman, P.; Lebeda, C.; Poling, D.; Thorton, R.

    1994-02-01

    Los Alamos National Laboratory (LANL) participated in the Central Equatorial Pacific Experiment (CEPEX) by fielding a water-vapor Raman lidar on board the Research Vessel Vickers. The lidar measured water vapor concentration from the surface to lower tropospheric altitudes in order to support the CEPEX goal of evaluating a hypothesis regarding feedback mechanisms for global circulation models. This report describes some of the features observed within the marine Atmospheric Boundary Layer (ABL) and the lower troposphere. Data was collected continuously 24 hours per day over the equatorial Pacific from March 8th to March 2 1st of 1993 while in route between Guadalcanal and Christmas Island (the transect was at approximately 2{degree} south latitude). The lidar collected vertical transects of water vapor concentration up to 10 km during night operations and 4 km in the day. The vertical lidar profiles of water vapor were produced by summing the data over a period up to 600 seconds. The water-vapor Raman lidar measured the properties of the marine ABL as well as the lower and mid-troposphere. From the lidar water vapor profiles, ``images`` of water vapor concentration versus altitude and date or sea surface temperature will be produced along with other products such as latent heat fluxes. The Raman water vapor lidar data will be used to better understand the role of transport and exchange at the ocean-atmosphere interface and throughout the marine atmosphere.

  11. Monitoring the Outer Region of the Neutral Atmosphere

    NASA Astrophysics Data System (ADS)

    Nossal, S. M.; Mierkiewicz, E. J.; Roesler, F. L.; Haffner, L. M.; Reynolds, R. J.; Woodward, R. C.

    2009-05-01

    Hydrogen is a primary constituent of the geocorona and is a chemical byproduct of species below such as methane and water vapor, two greenhouse gases. The solar cycle is a dominant source of natural variability in this region and must be accounted for when isolating the effects of coupling processes from below, including that due to potential long-term change in the region. Observations by the Wisconsin H-alpha Mapper Fabry- Perot of geocoronal hydrogen Balmer-alpha emissions over solar cycle 23 have quantified a factor of 1.5 ± 0.15 higher intensities at solar maximum than at solar minimum. These observations are consistent with Fabry-Perot observations from Wisconsin during solar cycle 22. All observations have been consistently calibrated for intensity using the North American Nebula. We used the LYAO_RT radiative transfer code of Bishop to compare the observed Balmer-alpha intensities with intensities calculated using the hydrogen density distribution in the Mass-Spectrometer-Incoherent-Scatter (MSIS) model, a major empirical model used by the middle and upper atmospheric research communities. The MSIS distribution yields a solar maximum to minimum ratio similar to that observed; however, significant differences in magnitude between predicted and observed intensities highlight the need for improved upper atmospheric hydrogen density determinations.

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

    NASA Astrophysics Data System (ADS)

    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.

  13. Coherent Structures in the Turbulent Atmospheric Boundary Layer: modulation by static stability and role in transport

    NASA Astrophysics Data System (ADS)

    Bou-Zeid, E.; Li, D.; Shah, S.

    2012-12-01

    Understanding the turbulent transport of momentum, scalars, and particles in the atmospheric boundary layer is important in many disciplines such as meteorology, hydrology, and desert morphodynamics. At present, similarity theories that rely on a significant degree of empiricism remain the main approach to understand and model these fluxes. One of the hurdles to developing more fundamental and robust theories is our lack of understanding of the topology and dynamics of turbulent coherent structures, which perform these fluxes, and how they are modulated by atmospheric stability. Using field data sets and numerical simulations of atmospheric surface layer flows under a range of stabilities, we revisit these links between coherent structures, atmospheric stability, and turbulent transport. The results confirm that the topology of the coherent structures is very sensitive to stability. The findings point to a gradual transformation of the structures from hairpin vortices under neutral stability, to thermals under unstable conditions, and to more horizontal structures under stable conditions. Under unstable conditions, this change then induces a decorrelation of the momentum and scalar fluxes in the surface layer: the eddies transporting heat and momentum become distinct leading to an increase in the transport efficiency of heat and a decrease in the transport efficiency of momentum. Under stable conditions, the reduction in the transport of momentum to the surface leads to reductions in the friction velocity and the turbulent kinetic energy (TKE) production. The effect of reduced production can be more important than the effect of direct TKE destruction in the stable ABL.

  14. Non-linear processes in the Earth atmosphere boundary layer

    NASA Astrophysics Data System (ADS)

    Grunskaya, Lubov; Valery, Isakevich; Dmitry, Rubay

    2013-04-01

    The work is connected with studying electromagnetic fields in the resonator Earth-Ionosphere. There is studied the interconnection of tide processes of geophysical and astrophysical origin with the Earth electromagnetic fields. On account of non-linear property of the resonator Earth-Ionosphere the tides (moon and astrophysical tides) in the electromagnetic Earth fields are kinds of polyharmonic nature. It is impossible to detect such non-linear processes with the help of the classical spectral analysis. Therefore to extract tide processes in the electromagnetic fields, the method of covariance matrix eigen vectors is used. Experimental investigations of electromagnetic fields in the atmosphere boundary layer are done at the distance spaced stations, situated on Vladimir State University test ground, at Main Geophysical Observatory (St. Petersburg), on Kamchatka pen., on Lake Baikal. In 2012 there was continued to operate the multichannel synchronic monitoring system of electrical and geomagnetic fields at the spaced apart stations: VSU physical experimental proving ground; the station of the Institute of Solar and Terrestrial Physics of Russian Academy of Science (RAS) at Lake Baikal; the station of the Institute of volcanology and seismology of RAS in Paratunka; the station in Obninsk on the base of the scientific and production society "Typhoon". Such investigations turned out to be possible after developing the method of scanning experimental signal of electromagnetic field into non- correlated components. There was used a method of the analysis of the eigen vectors ofthe time series covariance matrix for exposing influence of the moon tides on Ez. The method allows to distribute an experimental signal into non-correlated periodicities. The present method is effective just in the situation when energetical deposit because of possible influence of moon tides upon the electromagnetic fields is little. There have been developed and realized in program components

  15. The Venus Neutral Atmosphere from the Radio Science Experiment VeRa on Venus Express

    NASA Astrophysics Data System (ADS)

    Tellmann, S.; Haeusler, B.; Paetzold, M.; Bird, M. K.; Tyler, G. L.

    2008-12-01

    The Venus Express Radio Science Experiment VeRa is sounding the Venus neutral atmosphere and ionosphere using the spacecraft radio subsystem in the oneway radio link mode at X-band (8.4 GHz) and S- band (2.3 GHz). An Ultrastable Oscillator (USO) provides a high quality onboard frequency reference source for the derivation of electron density profiles in the ionosphere and profiles of pressure, temperature and neutral number density of the neutral atmosphere. Radial profiles of neutral number density derived from the occultations cover the altitude range 40 to 90 km, which are converted to vertical profiles of temperature and pressure. The polar orbit of Venus Express provides the opportunity to study the atmosphere at all planetocentric latitudes under varying illumination conditions. Five occultation seasons could be covered so far during the Venus Express mission resulting in a data set of more than 150 profiles of the neutral atmosphere. The thermal structure is investigated with regard to the latitudinal and temporal variability. A distinct cold collar region could be observed on both hemispheres. The tropopause altitude increases in this latitude region while the tropopause temperature shows a strong decrease. Profiles of static stability are found to be latitude-dependent and nearly adiabatic in the middle cloud region.

  16. Neutral gas jet in a low velocity shock front at the boundary of the Draco Nebula

    SciTech Connect

    Kalberla, P.W.M.; Herbstmeier, U.; Mebold, U.

    1984-11-01

    Twenty-one cm line observations with the Westerbork Synthesis Radio Telescope of a dust and molecular filament at the boundary of the Draco Nebula reveal a jet like neutral hydrogen feature funneling through an outlet in the low velocity shock front at the interface between the Draco Nebula and the surrounding gas. The jet like feature is apparently connected with a high velocity filament at VLSR -180 km/sec. It is suggested that soft X-ray emission observed in the area is thermal bremsstrahlung produced by the deceleration of high velocity gas in galactic gas.

  17. [Turbulent characteristics in forest canopy under atmospheric neutral condition].

    PubMed

    Diao, Yi-Wei; Guan, De-Xin; Jin, Chang-Jie; Wang, An-Zhi; Pei, Tie-Fan

    2010-02-01

    Based on the micrometeorological data of broad-leaved Korean pine forest in Changbai Mountain in 2003, a second-order closure model was employed to calculate and analyze the turbulent characteristics within and above the canopy of the forest. The calculated mean wind profile was coincident with the measured one. The Reynolds stress within the forest was significantly attenuated. The turbulent strength, velocity flux, and skew were the largest at forest-atmosphere interface, as well the wind shear. With the increase of velocity skew, the turbulent intermittence became more significant, and the downward turbulent eddy within the canopy was limited. Most of the turbulent deeply within the forest canopy was produced by the non-local contributions above the canopy.

  18. Modeling Plasmas with Strong Anisotropy, Neutral Fluid Effects, and Open Boundaries

    NASA Astrophysics Data System (ADS)

    Meier, Eric T.

    Three computational plasma science topics are addressed in this research: the challenge of modeling strongly anisotropic thermal conduction, capturing neutral fluid effects in collisional plasmas, and modeling open boundaries in dissipative plasmas. The research efforts on these three topics contribute to a common objective: the improvement and extension of existing magnetohydrodynamic modeling capability. Modeling magnetically confined fusion-related plasmas is the focus of the research, but broader relevance is recognized and discussed. Code development is central to this work, and has been carried out within the flexible physics framework of the highly parallel HiFi implicit spectral element code. In magnetic plasma confinement, heat conduction perpendicular to the magnetic field is extremely slow compared to conduction parallel to the field. The anisotropy in heat conduction can be many orders of magnitude, and the inaccuracy of low-order representations can allow parallel heat transport to "leak" into the perpendicular direction, resulting in numerical perpendicular transport. If the computational grid is aligned to the magnetic field, this numerical error can be eliminated, even for low-order representations. However, grid alignment is possible only in idealized problems. In realistic applications, magnetic topology is chaotic. A general approach for accurately modeling the extreme anisotropy of fusion plasmas is to use high-order representations which do not require grid alignment for sufficient resolution. This research provides a comprehensive assessment of spectral element representation of anisotropy, in terms of dependence of accuracy on grid alignment, polynomial degree, and grid cell size, and gives results for two- and three-dimensional cases. Truncating large physical domains to concentrate computational resources is often necessary or desirable in simulating natural and man-made plasmas. A novel open boundary condition (BC) treatment for such

  19. Interaction between the atmospheric and oceanic boundary layers

    NASA Technical Reports Server (NTRS)

    Yeh, G.-T.

    1974-01-01

    The two-layer system of an atmosphere over water bodies is reduced to a single-layer problem. Values of the interfacial quantities, such as the friction velocity, the surface velocity, the angles, alpha and beta, between the surface shear stress and the geostrophic wind velocity and the surface wind velocity, respectively, and the surface roughness, all of which depend upon external parameters, such as the geostrophic wind and stratifications, are obtained. The geostrophic drag coefficient, the geostrophic wind coefficient, and the angles alpha, and beta, of the turbulent flow at the sea-air interface are functions of a dimensionless number, mfG/kg, with S sub 1 and S sub 2 as two free stratification parameters. The surface roughness is uniquely determined from the geostrophic wind rather than from the wind profile in the boundary layer.

  20. Neutral atmosphere composition from SOIR measurements on board Venus Express

    NASA Astrophysics Data System (ADS)

    Mahieux, A.; Drummond, R.; Wilquet, V.; Vandaele, A. C.; Federova, A.; Belyaev, D.; Korablev, O.; Villard, E.; Montmessin, F.; Bertaux, J.-L.

    2009-04-01

    The SOIR instrument performs solar occultation measurements in the IR region (2.2 - 4.3 m) at a resolution of 0.12 cm-1, the highest on board Venus Express. It combines an echelle spectrometer and an AOTF (Acousto-Optical Tunable Filter) for the order selection [1,2]. The wavelength range probed by SOIR allows a detailed chemical inventory of the Venus atmosphere above the cloud layer with an emphasis on vertical distribution of the gases. Measurements of HDO, H2O, HCl, HF, CO and CO2 vertical profiles have been routinely performed, as well as those of their isotopologues [3,4]. We will discuss the improvements introduced in the analysis algorithm of the SOIR spectra. This discussion will be illustrated by presenting new results of retrievals of minor constituents of the Venus mesosphere, in terms of vertical profiles and geographical distribution. CO2 is the major constituent of the Venus atmosphere and was therefore observed in many solar occultations, leading to a good geographical coverage, although limited by the geometry of the orbit. Depending on the abundance of the absorbing isotopologue and on the intensity of the band measured, we will show that the SOIR instrument is able to furnish CO2 vertical profiles ranging typically from 65 to 150 km, reaching in some conditions 185 km altitude. This information is important in the frame of compiling, in collaboration with other teams, a new Venus Atmosphere Model. 1. A. Mahieux, S. Berkenbosch, R. Clairquin, D. Fussen, N. Mateshvili, E. Neefs, D. Nevejans, B. Ristic, A. C. Vandaele, V. Wilquet, D. Belyaev, A. Fedorova, O. Korablev, E. Villard, F. Montmessin and J.-L. Bertaux, "In-Flight performance and calibration of SPICAV SOIR on board Venus Express", Applied Optics 47 (13), 2252-65 (2008). 2. D. Nevejans, E. Neefs, E. Van Ransbeeck, S. Berkenbosch, R. Clairquin, L. De Vos, W. Moelans, S. Glorieux, A. Baeke, O. Korablev, I. Vinogradov, Y. Kalinnikov, B. Bach, J.-P. Dubois and E. Villard, "Compact high

  1. The neutral atmosphere temperature experiment. [for thermospheric nitrogen measurement on AEROS satellite

    NASA Technical Reports Server (NTRS)

    Spencer, N. W.; Pelz, D. T.; Niemann, H. B.; Carignan, G. R.; Caldwell, J. R.

    1974-01-01

    The AEROS Neutral Atmosphere Temperature Experiment (NATE) is designed to measure the kinetic temperature of molecular nitrogen in the thermosphere. A quadrupole mass spectrometer tuned to N2 measures the N2 density variation in a small spherical antechamber having a knife-edged orifice which is exposed to the atmosphere at the outer surface of the spacecraft. The changing density of N2 due to the spinning motion of the spacecraft permits determination of the velocity distribution of the N2 from which the temperature is calculated. An alternate mode of operation of the instrument allows measurement of the other gases in the atmosphere as well as N2 permitting determination of the neutral particle composition of the atmosphere.

  2. Acid–base chemical reaction model for nucleation rates in the polluted atmospheric boundary layer

    PubMed Central

    Chen, Modi; Titcombe, Mari; Jiang, Jingkun; Jen, Coty; Kuang, Chongai; Fischer, Marc L.; Eisele, Fred L.; Siepmann, J. Ilja; Hanson, David R.; Zhao, Jun; McMurry, Peter H.

    2012-01-01

    Climate models show that particles formed by nucleation can affect cloud cover and, therefore, the earth's radiation budget. Measurements worldwide show that nucleation rates in the atmospheric boundary layer are positively correlated with concentrations of sulfuric acid vapor. However, current nucleation theories do not correctly predict either the observed nucleation rates or their functional dependence on sulfuric acid concentrations. This paper develops an alternative approach for modeling nucleation rates, based on a sequence of acid–base reactions. The model uses empirical estimates of sulfuric acid evaporation rates obtained from new measurements of neutral molecular clusters. The model predicts that nucleation rates equal the sulfuric acid vapor collision rate times a prefactor that is less than unity and that depends on the concentrations of basic gaseous compounds and preexisting particles. Predicted nucleation rates and their dependence on sulfuric acid vapor concentrations are in reasonable agreement with measurements from Mexico City and Atlanta. PMID:23091030

  3. Acid-base chemical reaction model for nucleation rates in the polluted atmospheric boundary layer.

    PubMed

    Chen, Modi; Titcombe, Mari; Jiang, Jingkun; Jen, Coty; Kuang, Chongai; Fischer, Marc L; Eisele, Fred L; Siepmann, J Ilja; Hanson, David R; Zhao, Jun; McMurry, Peter H

    2012-11-13

    Climate models show that particles formed by nucleation can affect cloud cover and, therefore, the earth's radiation budget. Measurements worldwide show that nucleation rates in the atmospheric boundary layer are positively correlated with concentrations of sulfuric acid vapor. However, current nucleation theories do not correctly predict either the observed nucleation rates or their functional dependence on sulfuric acid concentrations. This paper develops an alternative approach for modeling nucleation rates, based on a sequence of acid-base reactions. The model uses empirical estimates of sulfuric acid evaporation rates obtained from new measurements of neutral molecular clusters. The model predicts that nucleation rates equal the sulfuric acid vapor collision rate times a prefactor that is less than unity and that depends on the concentrations of basic gaseous compounds and preexisting particles. Predicted nucleation rates and their dependence on sulfuric acid vapor concentrations are in reasonable agreement with measurements from Mexico City and Atlanta.

  4. Characterization of the atmospheric state: Lower boundary condition

    SciTech Connect

    Doran, J. C.; Barnard, J. C.; Hubbe, J. M.; Liljegren, J. C.; Shaw, W. J.; Zhong, S.; Collatz, G. J.; Cook, D. R.; Hart, R. L.

    2000-04-04

    It is convenient to consider 2 broad categories of climate-related modeling studies for which it is necessary to specify some kind of lower boundary conditions. The first of these categories is the use of general circulation or weather forecasting models, perhaps modified to carry out climate simulations. In these models, one normally has to specify something about the albedo of the surface to get the radiation balance right, the surface roughness to get the momentum exchange right, and the surface moisture availability to get the surface heat and water vapor fluxes right. Correctly specifying the surface moisture availability can be a major problem and may involve a sophisticated land surface parameterization scheme to take into account plant and soil characteristics. It is reasonable to expect that misrepresenting the water vapor flux by 10--20% on average over continental scales could lead to significant errors in simulated precipitation, temperatures, and circulation patterns. The Atmospheric Radiation Measurement (ARM) Program is focused, however, on clouds and radiation; and it has chosen Cloud and Radiation Testbeds (CART) as the principal tool with which to carry out its work. In this context, what the authors are concerned about for the lower boundary conditions is somewhat different. What they want to known is show the incoming radiation is partitioned into various components by surface processes, and--more importantly--what is the resultant sensitivity of the cloud and radiation fields to that partitioning. These features then determine the accuracy to which they need to describe the lower boundary conditions.

  5. The vertical turbulence structure of the coastal marine atmospheric boundary layer

    SciTech Connect

    Tjernstroem, M.; Smedman, A.S. )

    1993-03-15

    The vertical turbulence structure in the marine atmosphere along a shoreline has been investigated using data from tower and aircraft measurements performed along the Baltic coast in the southeast of Sweden. Two properties make the Baltic Sea particularly interesting. It is surrounded by land in all directions within moderate advection distances, and it features a significant annual lag in sea surface temperature as compared with inland surface temperature. The present data were collected mostly during spring or early summer, when the water is cool, i.e., with a stably or neutrally stratified marine boundary layer usually capped by an inversion. Substantial daytime heating over the land area results in a considerable horizontal thermal contrast. Measurements were made on a small island, on a tower with a good sea fetch, and with an airborne instrument package. The profile data from the aircraft is from 25 slant soundings performed in connection to low level boundary layer flights. The results from the profiles are extracted through filtering techniques on individual time (space) series (individual profiles), applying different normalization and finally averaging over all or over groups of profiles. The land-based data are from a low tower situated on the shoreline of a small island with a wide sector of unobstructed sea fetch. Several factors are found that add to the apparent complexity of the coastal marine environment: the state of the sea appears to have a major impact on the turbulence structure of the surface layer, jet-shaped wind speed profiles were very common at the top of the boundary layer (in about 50% of the cases) and distinct layers with increased turbulence were frequently found well above the boundary layer (in about 80% of the cases). The present paper will concentrate on a description of the experiment, the analysis methods, and a general description of the boundary layer turbulence structure over the Baltic Sea. 40 refs., 16 figs., 2 tabs.

  6. Dispersion of Particles Released into a Neutral Planetary Boundary Layer: A comparative study between three stochastic, discontinuous trajectory models.

    NASA Astrophysics Data System (ADS)

    Avila, Ruben; Raza, Syed

    1999-11-01

    The dispersion of particles which are continuosly released into a neutral planetary boundary layer is presented. Three stochastic, discontinuous models (Monte Carlo, Markov chains and Markov chain-Monte Carlo) are used to predict the trajectory and velocity history of particles which behave as fluid elements. The concentration of particles is also determined by using a fully Lagrangian method known as smoothed particle hydrodynamics, which has been unified with a hierarchical tree algorithm (TREESPH method). The mean velocities and the turbulent characteristics of the atmospheric flow are obtained by using an algebraic Reynolds stress turbulence model. The numerical simulation of the atmospheric flow is compared with observations and with computational results previously published. The predicted root mean-square single particle displacements for an elevated continuous source are compared with the Pasquill-Gifford σz and σy empirical parameters for the Pasquill stability class D. The numerical computations of particle concentration are compared with the results obtained by a general Gaussian dispersion equation for continuous releases over flat terrain. The predictions of particle dispersion (σ's values) and particle concentration indicate that the Pasquill-Gifford empirical parameters are valid only within the range where the effect of the Ekman spiral is small. The results also show that the particle dispersion and the concentration profiles depend on the "jump" stochastic model and on the release height.

  7. Bauxite residue neutralization with simultaneous mineral carbonation using atmospheric CO2.

    PubMed

    Han, Young-Soo; Ji, Sangwoo; Lee, Pyeong-Koo; Oh, Chamteut

    2017-03-15

    Simultaneous carbon mineralization during neutralization of bauxite residue, a caustic alkaline by-product of alumina refining, was tested using laboratory batch and a field pilot study in contact with atmospheric CO2. Since CO2 sequestration is limited by the Ca concentration in the bauxite residue, extra Ca sources were added in a semi-soluble mineral and salt form (flue gas desulfurization gypsum or CaCl2) to verify whether this Ca addition accelerated and enlarged the CO2 sequestration obtained as a consequence of neutralization. The results of 55 days of batch and longer-term field tests were in good agreement, and the neutralization rate was accelerated through the addition of both Ca sources. Without the addition of the extra Ca source, atmospheric CO2 contributed to neutralization of pore water alkalinity alone, while Ca addition induced further neutralization through mineral carbonation of atmospheric CO2 to CaCO3. This simple addition of environmentally benign Ca to bauxite residue may provide a feasible bauxite residue management practice that is cost-effective and easy to apply in the field.

  8. Kinetic modeling of Europa's neutral atmosphere and pick-up ions

    NASA Astrophysics Data System (ADS)

    Tenishev, V.; Rubin, M.; Borovikov, D.; Jia, X.; Combi, M. R.; Gombosi, T. I.

    2013-12-01

    Europa was the highest priority outer planet exploration target in the 2007 NASA Science Plan, the 2006 Solar System Exploration Roadmap, and the 2003 planetary sciences Decadal Survey. The in-depth exploration of the plasma environment of Jupiter's moon Europa and investigation of its interaction with moon's surface and atmosphere remains a central objective of any proposed Europa Jupiter System Mission. The neutral species in Europa's atmosphere are mostly provided by ion sputtering of the water ice surface. Energetic ions and electrons from the Jovian magnetosphere produce molecular oxygen O2, the dominant species in Europa's atmosphere. Very close to the moon's surface the probability for collisional interaction between the species is close to the limit for a surface bound exosphere. The main loss mechanisms for neutrals are electron impact ionization, photoionization, as well as escape when neutral particles leave Europa's Hill sphere at roughly 8.7 Europa radii. The neutral and plasma environment of Europa are a tightly coupled system. A detailed study of this system requires coupled models of both the plasma and neutral environment. In this study we use coupled state-of-the-art computer models developed at the University of Michigan. In particular we include the BATSRUS MHD code of the Space Weather Modeling Framework (SWMF) and the Adaptive Mesh Particle Simulator (AMPS) model based on the DSMC method that both have well proven heritage in numerous space applications. In this investigation we calculate the plasma distribution in the vicinity of Europa at different locations along its orbit. The energetic ion flux derived from these calculations is used for simulation of the neutral particle sputtering that form Europa's atmosphere. The subsequent ionization of these neutral particles is the source of the pick-up ions. Populations of the neutrals and ions are calculated by tracing trajectories of the individual particles with accounting for both Europa

  9. Vegetation-atmosphere interactions and boundary layer cumulus clouds

    NASA Astrophysics Data System (ADS)

    Freedman, Jeffrey Michael

    2000-07-01

    A study of vegetation-atmosphere interactions and boundary layer cumulus clouds (``BLcu'') in terms of seasonal trends (i.e., heat and moisture tendencies) and short-term events (specifically the modification of in situ air masses) is presented. In the northeastern U.S., in response to increasing insolation and sensible heat flux, both the mixed layer height (zi) and lifting condensation level (LCL) peak (~1300 and 1700 m) just before the start of the growing season. With the commencement of transpiration, the Bowen ratio (β) falls abruptly (from greater than 3 to less than 1) as additional moisture is transpired into the boundary layer, and zi and the LCL decrease. By late spring, boundary layer cumulus cloud frequency increases sharply, as the mixed layer approaches a new equilibrium. At Harvard Forest during 1995, afternoon net carbon uptake (Fco2 ) was 52% greater on days with boundary layer cumulus clouds than clear days. For 1996-1998, afternoon Fco2 was also enhanced, especially during dry periods. The same enhancement, albeit reduced, was observed at a northern jack pine site during the BOREAS project, despite very different phenological, hydrological, and climatological regimes. Sixteen frontal sequences affecting the northeastern U.S. were analyzed in terms of local and regional contributions to the temperature and moisture tendency equations. A composite of sequences featuring the daily appearance of BLcu indicates a diminished role for entrainment and other external forcings due to the daily occurrence of a rapid growth phase in ML diurnal evolution subsequent to day 1. From the sequence minimum (day 2) in temperature and moisture, surface flux convergence accounts for about 50% of the overall net moistening and heating of the mixed layer. Model sensitivity tests show that changes in subsidence and γ θν affect ML processes most on day 1; dining subsequent days, the rapid growth phase dominates the ML growth equation, and reduces the impact of these

  10. Equivalence-point electromigration acid-base titration via moving neutralization boundary electrophoresis.

    PubMed

    Yang, Qing; Fan, Liu-Yin; Huang, Shan-Sheng; Zhang, Wei; Cao, Cheng-Xi

    2011-04-01

    In this paper, we developed a novel method of acid-base titration, viz. the electromigration acid-base titration (EABT), via a moving neutralization boundary (MNR). With HCl and NaOH as the model strong acid and base, respectively, we conducted the experiments on the EABT via the method of moving neutralization boundary for the first time. The experiments revealed that (i) the concentration of agarose gel, the voltage used and the content of background electrolyte (KCl) had evident influence on the boundary movement; (ii) the movement length was a function of the running time under the constant acid and base concentrations; and (iii) there was a good linearity between the length and natural logarithmic concentration of HCl under the optimized conditions, and the linearity could be used to detect the concentration of acid. The experiments further manifested that (i) the RSD values of intra-day and inter-day runs were less than 1.59 and 3.76%, respectively, indicating similar precision and stability in capillary electrophoresis or HPLC; (ii) the indicators with different pK(a) values had no obvious effect on EABT, distinguishing strong influence on the judgment of equivalence-point titration in the classic one; and (iii) the constant equivalence-point titration always existed in the EABT, rather than the classic volumetric analysis. Additionally, the EABT could be put to good use for the determination of actual acid concentrations. The experimental results achieved herein showed a new general guidance for the development of classic volumetric analysis and element (e.g. nitrogen) content analysis in protein chemistry.

  11. Structure and Composition of the Neutral Upper Atmosphere of Mars from the MAVEN NGIMS Investigation

    NASA Astrophysics Data System (ADS)

    Mahaffy, P. R.; Benna, M.; Yelle, R. V.; Stone, S. W.; Elrod, M. K.; Fox, J. L.

    2015-12-01

    The Neutral Gas and Ion Mass Spectrometer (NGIMS) on the MAVEN mission is designed to characterize the state of the upper atmosphere and its response to perturbations from the sun and from lower atmosphere. These measurements complement other instruments on the MAVEN spacecraft and support the MAVEN science goal [Jakosky et al., 2015] of understanding atmospheric escape and over the course of martian history. We report NGIMS measurements of the neutral composition of multiple atomic and molecular species over hundreds of orbits since the science phase of this mission began late in 2014. Ion measurements from NGIMS are reported separately in other contributions to this session. The wide dynamic range, the high temporal resolution, and the use of two different ion source configurations of the NGIMS instrument [Mahaffy et al., 2014] allows neutral density structure and its variability to be characterized in detail. Large amplitude wave structure is observed on the lowest altitude portion of many orbits that dissipates at higher altitudes. Although this structure puts scatter in the retrieval of scale height temperatures these are nevertheless robustly secured by averaging over several orbits. The variability of the upper atmosphere temperature with latitude and local solar time is reported. The deep dip campaign approach to the homopause allows the mixing ratio of the major gases in the lower atmosphere to be measured. We compare these mixing ratios with those reported by the Sample Analysis at Mars investigation and previous Viking measurements. Jakosky, B. M., et al. (2015), The Mars Atmosphere and Volatile Evolution (MAVEN) Mission, Space Sci Rev, 21. Mahaffy, P. R., et al. (2014), The Neutral Gas and Ion Mass Spectrometer on the Mars Atmosphere and Volatile Evolution Mission, Space Sci Rev, 185, DOI: 10.1007/s11214-11014-10091-11211.

  12. Structure and composition of the neutral upper atmosphere of Mars from the MAVEN NGIMS investigation

    PubMed Central

    Benna, M.; Elrod, M.; Yelle, R. V.; Bougher, S. W.; Stone, S. W.; Jakosky, B. M.

    2015-01-01

    Abstract The Mars Atmosphere and Volatile EvolutioN (MAVEN) Neutral Gas and Ion Mass Spectrometer (NGIMS) provides sensitive detections of neutral gas and ambient ion composition. NGIMS measurements of nine atomic and molecular neutral species, and their variation with altitude, latitude, and solar zenith angle are reported over several months of operation of the MAVEN mission. Sampling NGIMS signals from multiple neutral species every several seconds reveals persistent and unexpectedly large amplitude density structures. The scale height temperatures are mapped over the course of the first few months of the mission from high down to midlatitudes. NGIMS measurements near the homopause of 40Ar/N2 ratios agree with those reported by the Sample Analysis at Mars investigation and allow the altitude of the homopause for the most abundant gases to be established. PMID:27667873

  13. Determination of seasonal variations in the Martian neutral atmosphere from observations of ionospheric peak height

    NASA Astrophysics Data System (ADS)

    Zou, Hong; Lillis, Robert J.; Wang, Jin Song; Nielsen, Erling

    2011-09-01

    Radio occultation experiments allow us to measure electron and neutral densities in planetary atmospheres. Here we investigate such measurements from the Mars Global Surveyor Radio Science experiment in 2 consecutive Martian years (25 and 26). Using Chapman theory, we parameterize the ionospheric peak altitude in terms of the solar zenith angle, neutral scale height at the peak, neutral density at 20 km and the effective neutral scale height ($\\overline{\\xin) between 20 km and the peak, finding the latter to be the primary driver of peak altitude. From the occultation data, we observe that altitudes of peak electron density at high northern latitudes show a clear seasonal trend, increasing from northern summer (Ls = 90°) to northern autumn (Ls = 180°), driven by substantial increases in $\\overline{\\xin, despite neutral densities at 20 km steadily decreasing as surface temperatures drop. We find these trends to be consistent with neutral density predictions from the LMD Mars Global Circulation Model at both 20 km and 130 km. The primary mechanism responsible for this increase in the 20-130 km effective neutral scale height (and hence temperature) is the southward drift in subsolar latitude as northern summer becomes autumn. This drives the seasonal evolution of the Martian interhemispheric Hadley circulation. The downward branch of this circulation leads to an increasing warming in the middle atmosphere at high north latitudes from the northern summer to the northern autumn, causing an increase in neutral scale height at and below the ionospheric peak and thus an increase in the ionospheric peak height.

  14. 1D-coupled photochemical model of neutrals, cations and anions in the atmosphere of Titan

    NASA Astrophysics Data System (ADS)

    Dobrijevic, M.; Loison, J. C.; Hickson, K. M.; Gronoff, G.

    2016-04-01

    Many models with different characteristics have been published so far to study the chemical processes at work in Titan's atmosphere. Some models focus on neutral species in the stratosphere or ionic species in the ionosphere, but few of them couple all the species throughout the whole atmosphere. Very few of these emphasize the importance of uncertainties in the chemical scheme and study their propagation in the model. We have developed a new 1D-photochemical model of Titan's atmosphere coupling neutral species with positive and negative ions from the lower atmosphere up to the ionosphere and have compared our results with observations to have a comprehensive view of the chemical processes driving the composition of the stratosphere and ionosphere of Titan. We have updated the neutral, positive ion and negative ion chemistry and have improved the description of N2 photodissociation by introducing high resolution N2 absorption cross sections. We performed for the first time an uncertainty propagation study in a fully coupled ion-neutral model. We determine how uncertainties on rate constants on both neutral and ionic reactions influence the model results and pinpoint the key reactions responsible for this behavior. We find very good agreement between our model results and observations in both the stratosphere and in the ionosphere for most neutral compounds. Our results are also in good agreement with an average INMS mass spectrum and specific flybys in the dayside suggesting that our chemical model (for both neutral and ions) provides a good approximation of Titan's atmospheric chemistry as a whole. Our uncertainty propagation study highlights the difficulty to interpret the INMS mass spectra for masses 14, 31, 41 and we identified the key reactions responsible for these ambiguities. Despite an overall improvement in the chemical model, disagreement for some specific compounds (HC3N, C2H5CN, C2H4) highlights the role that certain physical processes could play

  15. Thermospheric Density Fluctuations Derived from the Atmospheric Neutral Density Experiment Risk Reduction Mission

    NASA Astrophysics Data System (ADS)

    Nicholas, A. C.; Budzien, S. A.; Healy, L.; Davis, M.

    2008-12-01

    The Atmospheric Neutral Density Experiment (ANDE) Risk Reduction flight was launched on Dec 9, 2006 and deployed into orbit by the Space Shuttle Discovery on December 21, 2006. The primary mission objective is to test the deployment mechanism from the Shuttle for the ANDE flight in mid 2009. Scientific objectives of the ANDE risk reduction flight include: monitor total neutral density along the orbit for improved orbit determination of resident space objects, monitor the spin rate and orientation of the spacecraft, and provide a test object for polarimetry studies. The two ANDERR spacecraft decayed on December 25, 2007 and May 21, 2008, atmospheric densities derived from observations of the ANDERR spacecraft will be presented and compared to atmospheric models and drivers.

  16. Turbulence in a convective marine atmospheric boundary layer

    NASA Technical Reports Server (NTRS)

    Chou, S.-H.; Atlas, D.; Yeh, E.-N.

    1986-01-01

    The structure and kinetic energy budget of turbulence in the convective marine atmospheric boundary layer as observed by aircraft during a cold air outbreak have been studied using mixed layer scaling. The results are significantly different from those of previous studies under conditions closer to free convection. The normalized turbulent kinetic energy and turbulent transport are about twice those found during the Air Mass Transformation Experiment (AMTEX). This implies that for a given surface heating the present case is dynamically more active. The difference is mainly due to the greater importance of wind shear in the present case. This case is closer to the roll vortex regime, whereas AMTEX observed mesoscale cellular convection which is closer to free convection. Shear generation is found to provide a significant energy source, in addition to buoyancy production, to maintain a larger normalized turbulent kinetic energy and to balance a larger normalized dissipation. The interaction between turbulent pressure and divergence (i.e., pressure scrambling) is also found to transfer energy from the vertical to the horizontal components, and is expected to be stronger in roll vortices than in m esoscale cells. The sensible heat flux is found to fit well with a linear vertical profile in a clear or subcloud planetary boundary layer (PBL), in good agreement with the results of Lenschow et al., (1980). The heat flux ratio between the PBL top and the surface, derived from the linear fitted curve, is approximately -0.14, in good agreement with that derived from the lidar data for the same case. Near the PBL top, the heat flux profiles are consistent with those of Deardoff (1979) and Deardorff et al. (1980).

  17. Earth’s Interaction Region: Plasma-Neutral Interactions in the Weakly Ionized gas of Earth’s High Latitude Upper Atmosphere

    NASA Astrophysics Data System (ADS)

    Thayer, Jeffrey; Hsu, Vicki

    2015-04-01

    The high-latitude regions of Earth’s upper atmosphere are strongly influenced by plasma-neutral interactions. These interactions couple electrodynamic processes of the ionosphere with hydrodynamic processes of the more abundant thermosphere neutral gas, consequently connecting the high-latitude upper atmosphere to distant regions of the geoplasma environment. This produces a complex spatial and temporal interplay of competing processes that results in a myriad of physical and chemical responses and a rich array of neutral and plasma morphologies that constitute the high-latitude thermosphere and ionosphere. The altitude extent from the lower thermosphere to the upper ionosphere (90km - 1000km) can be considered Earth’s space-atmosphere interaction region - likened to the solar chromosphere’s interaction region where radiative processes and hydrodynamic waves from the dense lower atmosphere produce a cold lower boundary that quickly transitions over a few 100 kilometers to neutral and plasma temperatures that are five times hotter. A thousand or more kilometers further in altitude, Earth's upper atmosphere becomes a hot, collisionless, geomagnetically controlled protonosphere whose neutral and plasma population originates from the thermosphere and ionosphere. A grand challenge in the study of Earth’s interaction region is how the collision-dominated thermosphere/ionosphere system exchanges energy, mass and momentum with the collisionless magnetosphere. This talk will focus primarily on collision-dominated processes of the high-latitude ionosphere and the electromagnetic energy transfer processes that lead to frictional heating of ions and neutrals, and plasma instability phenomenon that leads to extreme electron heating. Observations of the ionosphere response to these processes will be illustrated using incoherent scatter radar measurements. Relevance to the solar chromosphere will be identified where appropriate and outstanding issues in Earth

  18. Scaling laws of turbulence intermittency in the atmospheric boundary layer: the role of stability

    NASA Astrophysics Data System (ADS)

    Paradisi, Paolo; Cesari, Rita; Allegrini, Paolo

    2015-09-01

    Bursting and intermittent behavior is a fundamental feature of turbulence, especially in the vicinity of solid obstacles. This is associated with the dynamics of turbulent energy production and dissipation, which can be described in terms of coherent motion structures. These structures are generated at random times and remain stable for long times, after which they become suddenly unstable and undergo a rapid decay event. This intermittent behavior is described as a birth-death point process of self-organization, i.e., a sequence of critical events. The Inter-Event Time (IET) distribution, associated with intermittent self-organization, is typically a power-law decay, whose power exponent is known as complexity index and characterizes the complexity of the system, i.e., the ability to develop self-organized, metastable motion structures. We use a method, based on diffusion scaling, for the estimation of system's complexity. The method is applied to turbulence velocity data in the atmospheric boundary layer. A neutral condition is compared with a stable one, finding that the complexity index is lower in the neutral case with respect to the stable one. As a consequence, the crucial birth-death events are more rare in the stable case, and this could be associated with a less efficient transport dynamics.

  19. Spatiotemporal structure of wind farm-atmospheric boundary layer interactions

    NASA Astrophysics Data System (ADS)

    Cervarich, Matthew; Baidya Roy, Somnath; Zhou, Liming

    2013-04-01

    Wind power is currently one of the fastest growing energy sources in the world. Most of the growth is in the utility sector consisting of large wind farms with numerous industrial-scale wind turbines. Wind turbines act as a sink of mean kinetic energy and a source of turbulent kinetic energy in the atmospheric boundary layer (ABL). In doing so, they modify the ABL profiles and land-atmosphere exchanges of energy, momentum, mass and moisture. This project explores theses interactions using remote sensing data and numerical model simulations. The domain is central Texas where 4 of the world's largest wind farms are located. A companion study of seasonally-averaged Land Surface Temperature data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on TERRA and AQUA satellites shows a warming signal at night and a mixed cooling/warming signal during the daytime within the wind farms. In the present study, wind farm-ABL interactions are simulated with the Weather Research and Forecasting (WRF) model. The simulations show that the model is capable of replicating the observed signal in land surface temperature. Moreover, similar warming/cooling effect, up to 1C, was observed in seasonal mean 2m air temperature as well. Further analysis show that enhanced turbulent mixing in the rotor wakes is responsible for the impacts on 2m and surface air temperatures. The mixing is due to 2 reasons: (i) turbulent momentum transport to compensate the momentum deficit in the wakes of the turbines and (ii) turbulence generated due to motion of turbine rotors. Turbulent mixing also alters vertical profiles of moisture. Changes in land-atmosphere temperature and moisture gradient and increase in turbulent mixing leads to more than 10% change in seasonal mean surface sensible and latent heat flux. Given the current installed capacity and the projected installation across the world, wind farms are likely becoming a major driver of anthropogenic land use change on Earth. Hence

  20. Ground-based lidar for atmospheric boundary layer ozone measurements.

    PubMed

    Kuang, Shi; Newchurch, Michael J; Burris, John; Liu, Xiong

    2013-05-20

    Ground-based lidars are suitable for long-term ozone monitoring as a complement to satellite and ozonesonde measurements. However, current ground-based lidars are unable to consistently measure ozone below 500 m above ground level (AGL) due to both engineering issues and high retrieval sensitivity to various measurement errors. In this paper, we present our instrument design, retrieval techniques, and preliminary results that focus on the high-temporal profiling of ozone within the atmospheric boundary layer (ABL) achieved by the addition of an inexpensive and compact mini-receiver to the previous system. For the first time, to the best of our knowledge, the lowest, consistently achievable observation height has been extended down to 125 m AGL for a ground-based ozone lidar system. Both the analysis and preliminary measurements demonstrate that this lidar measures ozone with a precision generally better than ±10% at a temporal resolution of 10 min and a vertical resolution from 150 m at the bottom of the ABL to 550 m at the top. A measurement example from summertime shows that inhomogeneous ozone aloft was affected by both surface emissions and the evolution of ABL structures.

  1. Ground-Based Lidar for Atmospheric Boundary Layer Ozone Measurements

    NASA Technical Reports Server (NTRS)

    Kuang, Shi; Newchurch, Michael J.; Burris, John; Liu, Xiong

    2013-01-01

    Ground-based lidars are suitable for long-term ozone monitoring as a complement to satellite and ozonesonde measurements. However, current ground-based lidars are unable to consistently measure ozone below 500 m above ground level (AGL) due to both engineering issues and high retrieval sensitivity to various measurement errors. In this paper, we present our instrument design, retrieval techniques, and preliminary results that focus on the high-temporal profiling of ozone within the atmospheric boundary layer (ABL) achieved by the addition of an inexpensive and compact mini-receiver to the previous system. For the first time, to the best of our knowledge, the lowest, consistently achievable observation height has been extended down to 125 m AGL for a ground-based ozone lidar system. Both the analysis and preliminary measurements demonstrate that this lidar measures ozone with a precision generally better than 10% at a temporal resolution of 10 min and a vertical resolution from 150 m at the bottom of the ABL to 550 m at the top. A measurement example from summertime shows that inhomogeneous ozone aloft was affected by both surface emissions and the evolution of ABL structures.

  2. Simultaneous profiling of the Arctic Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

    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. So far, such processes are not sufficiently resolved in numerical weather prediction (NWP) and climate models. 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 will be used under Arctic conditions in March/April 2009. This time the special purpose will be to send two SUMOs simultaneously on mission; one over the ice and snow-covered land surface and the other one above the open water of Isfjorden. This will be 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.

  3. BIOGENIC HYDROCARBONS IN THE ATMOSPHERIC BOUNDARY LAYER: A REVIEW

    EPA Science Inventory

    Nonmethane hydrocarbons are ubiquitous trace atmospheric constituents yet they control the oxidation capacity of the atmosphere. Both anthropogenic and biogenic processes contribute to the release of hydrocarbons to the atmosphere. In this manuscript, the state of the science ...

  4. Mesoscale Coupled Ocean-Atmosphere Feedbacks in Boundary Current Systems

    NASA Astrophysics Data System (ADS)

    Putrasahan, Dian Ariyani

    The focus of this dissertation is on studying ocean-atmosphere (OA) interactions in the Humboldt Current System (HCS) and Kuroshio Extension (KE) region using satellite observations and the Scripps Coupled Ocean-Atmosphere Regional (SCOAR) model. Within SCOAR, a new technique is introduced by implementing an interactive 2-D spatial smoother within the SST-flux coupler to remove the mesoscale SST field felt by the atmosphere. This procedure allows large-scale SST coupling to be preserved while extinguishing the mesoscale eddy impacts on the atmospheric boundary layer (ABL). This technique provides insights to spatial-scale dependence of OA coupling, and the impact of mesoscale features on both the ABL and the surface ocean. For the HCS, the use of downscaled forcing from SCOAR, as compared to NCEP Reanalysis 2, proves to be more appropriate in quantifying wind-driven upwelling indices along the coast of Peru and Chile. The difference in their wind stress distribution has significant impact on the wind-driven upwelling processes and total upwelling transport along the coast. Although upwelling induced by coastal Ekman transport dominates the wind-driven upwelling along coastal areas, Ekman pumping can account for 30% of the wind-driven upwelling in several coastal locations. Control SCOAR shows significant SST-wind stress coupling during fall and winter, while Smoothed SCOAR shows insignificant coupling throughout, indicating the important role of ocean mesoscale eddies on air-sea coupling in HCS. The SST-wind stress coupling however, did not produce any rectified response on the ocean eddies. Coupling between SST, wind speed and latent heat flux is insignificant on large-scale coupling and full coupling mode. On the other hand, coupling between these three variables are significant on the mesoscale for most of the model run, which suggests that mesoscale SST affects latent heat through direct flux anomalies as well as indirectly through stability changes on the

  5. Energetic neutral atoms measured by the interstellar boundary explorer (IBEX): evidence for multiple heliosheath populations

    DOE PAGES

    Desai, M. I.; Allegrini, F. A.; Bzowski, M.; ...

    2013-12-13

    Energetic neutral atoms (ENAs) observed by the Interstellar Boundary Explorer (IBEX) provide powerful diagnostics about the origin of the progenitor ion populations and the physical mechanisms responsible for their production. In this paper, we extend the work of Desai et al. and Fuselier et al. and combine and compare ENA spectra from the first 3 yr of observations by the IBEX-Hi and -Lo ENA imagers along the lines-of-sight (LOSs) from the inner heliosphere through to the locations of Voyager 1 and 2 with results from an updated physics-based model of the three-dimensional heliosphere and its constituent ion populations. Our resultsmore » show that (1) IBEX ENA fluxes and spectra above ~0.7 keV measured along the LOSs of the Voyagers are consistent with several models in which the parent pickup ion (PUI) populations originate in the inner heliosheath, and (2) a significant fraction of lower energy ENAs between ~0.1-0.5 keV may originate from interstellar neutral gas charge-exchanging with a non-thermalized (hot) population of PUIs in the outer heliosheath beyond the heliopause. Here we discuss the implications of ENAs observed by IBEX originating from distinct parent populations as well as from two distinct locations in the heliospheric interface. In conclusion, these results indicate that ENA spectral measurements at various energies can be used to remotely probe distinct physical processes operating in vastly different regions of the distant heliosphere.« less

  6. Energetic neutral atoms measured by the interstellar boundary explorer (IBEX): evidence for multiple heliosheath populations

    SciTech Connect

    Desai, M. I.; Allegrini, F. A.; Bzowski, M.; Dayeh, M. A.; Funsten, H.; Fuselier, S. A.; Heerikhuisen, J.; Kubiak, M. A.; McComas, D. J.; Pogorelov, N. V.; Schwadron, N. A.; Sokół, J. M.; Zank, G. P.; Zirnstein, E. J.

    2013-12-13

    Energetic neutral atoms (ENAs) observed by the Interstellar Boundary Explorer (IBEX) provide powerful diagnostics about the origin of the progenitor ion populations and the physical mechanisms responsible for their production. In this paper, we extend the work of Desai et al. and Fuselier et al. and combine and compare ENA spectra from the first 3 yr of observations by the IBEX-Hi and -Lo ENA imagers along the lines-of-sight (LOSs) from the inner heliosphere through to the locations of Voyager 1 and 2 with results from an updated physics-based model of the three-dimensional heliosphere and its constituent ion populations. Our results show that (1) IBEX ENA fluxes and spectra above ~0.7 keV measured along the LOSs of the Voyagers are consistent with several models in which the parent pickup ion (PUI) populations originate in the inner heliosheath, and (2) a significant fraction of lower energy ENAs between ~0.1-0.5 keV may originate from interstellar neutral gas charge-exchanging with a non-thermalized (hot) population of PUIs in the outer heliosheath beyond the heliopause. Here we discuss the implications of ENAs observed by IBEX originating from distinct parent populations as well as from two distinct locations in the heliospheric interface. In conclusion, these results indicate that ENA spectral measurements at various energies can be used to remotely probe distinct physical processes operating in vastly different regions of the distant heliosphere.

  7. Unsteady Flow in Different Atmospheric Boundary Layer Regimes and Its Impact on Wind-Turbine Performance

    NASA Astrophysics Data System (ADS)

    Gohari, Iman; Korobenko, Artem; Yan, Jinhui; Bazilevs, Yuri; Sarkar, Sutanu

    2016-11-01

    Wind is a renewable energy resource that offers several advantages including low pollutant emission and inexpensive construction. Wind turbines operate in conditions dictated by the Atmospheric Boundary Layer (ABL) and that motivates the study of coupling ABL simulations with wind turbine dynamics. The ABL simulations can be used for realistic modeling of the environment which, with the use of fluid-structure interaction, can give realistic predictions of extracted power, rotor loading, and blade structural response. The ABL simulations provide inflow boundary conditions to the wind-turbine simulator which uses arbitrary Lagrangian-Eulerian variational multiscale formulation. In the present work, ABL simulations are performed to examine two different scenarios: (i) A neutral ABL with zero heat-flux and inversion layer at 350m, in which the wind turbine experiences maximum mean shear; (2) A shallow ABL with the surface cooling-rate of -1 K/hr, in which the wind turbine experiences maximum mean velocity at the low-level-jet nose height. We will discuss differences in the unsteady flow between the two different ABL conditions and their impact on the performance of the wind turbine cluster in the coupled ABL-wind turbine simulations.

  8. Atmospheric planetary boundary layer feedback in climate system and triggering of climate change at high latitudes

    NASA Astrophysics Data System (ADS)

    Esau, I.; Zilitinkevich, S.

    2009-04-01

    Recent publications have revealed that modern, state-of-the-art climate-change models (CCMs) are not sensitive enough to reproduce some fine features of the observed changes in the surface air temperature (SAT) especially at high latitudes. We propose that this problem results from inaccurate representation of the very shallow long-lived stable (LS) and conventionally neutral (CN) atmospheric planetary boundary layers (PBLs) typical of high latitudes, especially of Polar regions. LS and CN PBLs, not yet included in the context of climate modelling, are almost an order of magnitude shallower than mid-latitudinal nocturnal stable (NS) and truly neutral (TN) PBLs, which are the only concern of the traditional theory of stable PBLs. In is only natural that factually observed shallow PBLs respond to thermal impacts (e.g. to the changes in the surface heat balance) much stronger than much deeper PBLs reproduced by the current PBL schemes. In this paper we investigate analytically the PBL feedback in climate system for all known kinds of PBL: stable (distinguishing between NS and LS), neutral (distinguishing between TN and CN) and also convective). Besides very high sensitivity of LS PBLs, quite consistent with the observed variability in SAT, our analyses reveal that in some specific conditions global warming could cause "strange cases" of local cooling. We also obtained analytically that the daily minimum temperatures are more sensitive to the global warming than the daily maximum temperatures, which, at least partially, explains such observed phenomena as asymmetry in the diurnal temperature trends and almost global reduction of the diurnal temperature range.

  9. Impact Wind Farms on the Marine Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Volker, P.; Capps, S. B.; Huang, H. J.; Sun, F.; Badger, J.; Hahmann, A.

    2012-12-01

    We introduce a new, validated wind farm parametrization (Explicit Wake Parametrization, EWP) which is based on the assumption that the downstream propagation of a single turbine wake can be described by a turbulent diffusion process. Thus, the downstream velocity deficit distribution can be described explicitly. Additionally, it allows us to take into account turbine interactions, making it possible to determine the unresolved turbine hub height velocities. Both the EWP wind farm parametrization and the wind farm scheme available in the Weather Research & Forecasting Model (WRF) have been validated against in situ measurements from Horns Rev I (A large offshore wind farm consisting of 80 2MW turbines situated near the west coast of Denmark). The main quantities of interest are the thrust applied to the flow, a consequence of the energy extracted by the wind turbines which determines mainly the wind farm wake extension (around 50 km for Horns Rev I) and the vertical velocity deficit distribution. Results show that the thrust in the WRF-WF scheme is overestimated inside the wind farm. We noticed that the velocity deficit propagates from the first turbine-containing-grid-cell up to the boundary layer top, which is in contrast to the theoretical expected expansion (confirmed by turbulence resolving models and wind tunnel results). The vertical expansion of the velocity deficit is a consequence of the additional turbulence source term in the WRF-WF scheme. The EWP scheme estimates the total amount of thrust correctly and is also able to follow the reduced thrust downstream since it considers the turbine interaction. From the good agreement with the far wake measurement, we can conclude that the formulation of the sub grid scale vertical extension of the velocity deficit must be correct. We will present results from WRF simulations in which we analyze the atmospheric response within the wake of wind farms resulting from the energy extraction of wind turbines. We place

  10. Visual offline sample stacking via moving neutralization boundary electrophoresis for analysis of heavy metal ion.

    PubMed

    Fan, Yinping; Li, Shan; Fan, Liuyin; Cao, Chengxi

    2012-06-15

    In this paper, a moving neutralization boundary (MNB) electrophoresis is developed as a novel model of visual offline sample stacking for the trace analysis of heavy metal ions (HMIs). In the stacking system, the cathodic-direction motion MNB is designed with 1.95-2.8mM HCl+98 mM KCl in phase alfa and 4.0mM NaOH+96 mM KCl in phase beta. If a little of HMI is present in phase alfa, the metal ion electrically migrates towards the MNB and react with hydroxyl ion, producing precipitation and moving precipitation boundary (MPB). The alkaline precipitation is neutralized by hydrogen ion, leading to a moving eluting boundary (MEB), release of HMI from its precipitation, circle of HMI from the MEB to the MPB, and highly efficient visual stacking. As a proof of concept, a set of metal ions (Cu(II), Co(II), Mn(II), Pb(II) and Cr(III)) were chosen as the model HMIs and capillary electrophoresis (CE) was selected as an analytical tool for the experiments demonstrating the feasibility of MNB-based stacking. As shown in this paper, (i) the visual stacking model was manifested by the experiments; (ii) there was a controllable stacking of HMI in the MNB system; (iii) the offline stacking could achieve higher than 123 fold preconcentration; and (iv) the five HMIs were simultaneously stacked via the developed stacking technique for the trace analyses with the limits of detection (LOD): 3.67×10(-3) (Cu(II)), 1.67×10(-3) (Co(II), 4.17×10(-3) (Mn(II)), 4.6×10(-4) (Pb(II)) and 8.40×10(-4)mM (Cr(III)). Even the off-line stacking was demonstrated for the use of CE-based HMI analysis, it has potential applications in atomic absorption spectroscopy (AAS), inductively coupled plasma-mass spectrometry (ICP-MS) and ion chromatography (IC) etc. Copyright © 2012 Elsevier B.V. All rights reserved.

  11. Estimating vertical fluxes of ozone within the atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Belan, Boris D.; Antokhin, Pavel N.; Antokhina, Olga Yu.; Arshinov, Mikhail Yu.; Belan, Sergey B.; Davydov, Denis K.; Krasnov, Oleg A.; Penenko, Alexey V.; Savkin, Denis E.; Sklyadneva, Tatayna K.; Tolmahev, Gennadii N.

    2017-04-01

    Investigation of the vertical distribution of ozone within the atmospheric boundary layer (ABL) was carried out by use of AN-2 light aircraft as a research platform. Vertical fluxes of ozone and their direction from the ground to the free-tropospheric level were calculated based on the in situ measurement data. Research flights have been performed over the greenhouse gas monitoring station located in a background area (56.1-56.4 N, 84.2-84.8 E) in the vicinity of abandoned village of Berezorechka (West Siberia). The schedule of diurnal flights was as follows: the first one just after the sunrise; the second one at noon; the third one 2-3 hours after noon, when a well-developed turbulence is observed; and the last one just before the sunset. A total of 10 diurnal cycles of measurements were undertaken. Analysis of the obtained data showed that the rate of ozone influx from upper layers of the atmosphere is 3-10 times less than the ozone production rate in the ABL. Average rate of ozone influx from the free troposphere was about 1 μg m-3 h-1, but ozone production rate in the ABL was about 5 μg m-3 h-1, so the major part of ozone is formed by photochemical reactions that occur within the ABL and only 20 % of its content is determined by the influx from the free troposphere. The vertical profiles of the ozone fluxes have shown that their maximum values are observed at heights from 200 to 600 m AGL. The height of the maximum depends on the season: in winter it is lower than 200-300 m, and in summer the maximum is observed at 500-600 m. The value of the ozone flux maximum also depends on the season and varies from 1 μg m-2 s-1in winter to 4.2 μg m-2 s-1 in spring. This work was supported by the Russian Foundation for Basic Research (grant No 17-05-00374).

  12. Neutral gas laser: a tool for sensing atmospheric species by infrared absorption

    NASA Astrophysics Data System (ADS)

    Wormhoudt, Joda C.; Kebabian, Paul L.

    1994-07-01

    In the spectroscopic analysis of atmospheric composition, there is a continuing need for stable and reproducible mid-infrared light sources. The neutral rare gas lasers offer several important benefits, in the many cases where one of their lines coincides with an absorption line of an atmospheric species to be observed. As atomic spectral lines, they are not subject to the drift and aging effects seen in diode lasers. Furthermore, the Zeeman effect provides up to a few tenths of a wavenumber of tunability, which can be an advantage over molecular lasers (such as CO2) which can only be tuned by line selection. We present observations in applications of neutral rare gas lasers to measurements of CO, N2O and CH4, and discuss possible applications to a variety of other species, including formaldehyde, methanol, hydrazine, water vapor, and the methyl radical.

  13. The Interstellar Boundary Explorer High Energy (IBEX-Hi) Neutral Atom Imager

    NASA Astrophysics Data System (ADS)

    Funsten, H. O.; Allegrini, F.; Bochsler, P.; Dunn, G.; Ellis, S.; Everett, D.; Fagan, M. J.; Fuselier, S. A.; Granoff, M.; Gruntman, M.; Guthrie, A. A.; Hanley, J.; Harper, R. W.; Heirtzler, D.; Janzen, P.; Kihara, K. H.; King, B.; Kucharek, H.; Manzo, M. P.; Maple, M.; Mashburn, K.; McComas, D. J.; Moebius, E.; Nolin, J.; Piazza, D.; Pope, S.; Reisenfeld, D. B.; Rodriguez, B.; Roelof, E. C.; Saul, L.; Turco, S.; Valek, P.; Weidner, S.; Wurz, P.; Zaffke, S.

    2009-08-01

    The IBEX-Hi Neutral Atom Imager of the Interstellar Boundary Explorer (IBEX) mission is designed to measure energetic neutral atoms (ENAs) originating from the interaction region between the heliosphere and the local interstellar medium (LISM). These ENAs are plasma ions that have been heated in the interaction region and neutralized by charge exchange with the cold neutral atoms of the LISM that freely flow through the interaction region. IBEX-Hi is a single pixel ENA imager that covers the ENA spectral range from 0.38 to 6 keV and shares significant energy overlap and overall design philosophy with the IBEX-Lo sensor. Because of the anticipated low flux of these ENAs at 1 AU, the sensor has a large geometric factor and incorporates numerous techniques to minimize noise and backgrounds. The IBEX-Hi sensor has a field-of-view (FOV) of 6.5°×6.5° FWHM, and a 6.5°×360° swath of the sky is imaged over each spacecraft spin. IBEX-Hi utilizes an ultrathin carbon foil to ionize ENAs in order to measure their energy by subsequent electrostatic analysis. A multiple coincidence detection scheme using channel electron multiplier (CEM) detectors enables reliable detection of ENAs in the presence of substantial noise. During normal operation, the sensor steps through six energy steps every 12 spacecraft spins. Over a single IBEX orbit of about 8 days, a single 6.5°×360° swath of the sky is viewed, and re-pointing of the spin axis toward the Sun near perigee of each IBEX orbit moves the ecliptic longitude by about 8° every orbit such that a full sky map is acquired every six months. These global maps, covering the spectral range of IBEX-Hi and coupled to the IBEX-Lo maps at lower and overlapping energies, will answer fundamental questions about the structure and dynamics of the interaction region between the heliosphere and the LISM.

  14. Neutral polyfluoroalkyl substances in the atmosphere over the northern South China Sea.

    PubMed

    Lai, Senchao; Song, Junwei; Song, Tianli; Huang, Zhijiong; Zhang, Yingyi; Zhao, Yan; Liu, Guicheng; Zheng, Junyu; Mi, Wenying; Tang, Jianhui; Zou, Shichun; Ebinghaus, Ralf; Xie, Zhiyong

    2016-07-01

    Neutral Polyfluoroalkyl substances (PFASs) in the atmosphere were measured during a cruise campaign over the northern South China Sea (SCS) from September to October 2013. Four groups of PFASs, i.e., fluorotelomer alcohols (FTOHs), fluorotelomer acrylates (FTAs), fluorooctane sulfonamides (FOSAs) and fluorooctane sulfonamidoethanols (FASEs), were detected in gas samples. FTOHs was the predominant PFAS group, accounting for 95.2-99.3% of total PFASs (ΣPFASs), while the other PFASs accounted for a small fraction of ΣPFASs. The concentrations of ΣPFASs ranged from 18.0 to 109.9 pg m(-3) with an average of 54.5 pg m(-3). The concentrations are comparable to those reported in other marine atmosphere. Higher concentrations of ΣPFASs were observed in the continental-influenced samples than those in other samples, pointing to the substantial contribution of anthropogenic sources. Long-range transport is suggested to be a major pathway for introducing gaseous PFASs into the atmosphere over the northern SCS. In order to further understand the fate of gaseous PFASs during transport, the atmospheric decay of neutral PFASs under the influence of reaction with OH radicals and atmospheric physical processes were estimated. Concentrations of 8:2 FTOH, 6:2 FTOH and MeFBSE from selected source region to the atmosphere over the SCS after long-range transport were predicted and compared with the observed concentrations. It suggests that the reaction with OH radicals may play an important role in the atmospheric decay of PFAS during long-range transport, especially for shorted-lived species. Moreover, the influence of atmospheric physical processes on the decay of PFAS should be further considered.

  15. Shallow marine cloud topped boundary layer in atmospheric models

    NASA Astrophysics Data System (ADS)

    Janjic, Zavisa

    2017-04-01

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

  16. Acoustic and gravity waves in the neutral atmosphere and the ionosphere, generated by severe storms

    NASA Technical Reports Server (NTRS)

    Balachandran, N. K.

    1983-01-01

    Gravity waves in the neutral atmosphere and their propagation in the ionosphere and the study of infrasonic signals from thunder were investigated. Doppler shifts of the order of 0.1 Hz are determined and they provide high-resolution measurements of the movements in the ionosphere. By using an array of transmitters with different frequencies and at different locations, the horizontal and vertical propagation vectors of disturbances propagating through the ionosphere are determined.

  17. Mechanics of chemical species transport in the marine atmospheric boundary layer

    NASA Technical Reports Server (NTRS)

    Hanson, Howard P.

    1989-01-01

    Marine atmospheric boundary layer (MABL) drafts are modeled as steady-state plumes using the approach proposed by Telford (1966), and the model response to varying forcing and boundary conditions is examined. Since most of the chemical species are passive tracers within the MABL, variations in the implied fluxes are determined as a combination of the boundary conditions for the chemical species and the thermodynamic forcing implied by the stability and thermal boundary conditions.

  18. Incorporation of the planetary boundary layer in atmospheric models

    NASA Technical Reports Server (NTRS)

    Moeng, Chin-Hoh; Wyngaard, John; Pielke, Roger; Krueger, Steve

    1993-01-01

    The topics discussed include the following: perspectives on planetary boundary layer (PBL) measurements; current problems of PBL parameterization in mesoscale models; and convective cloud-PBL interactions.

  19. Precipitation of energetic neutral atoms and induced non-thermal escape fluxes from the Martian atmosphere

    SciTech Connect

    Lewkow, N. R.; Kharchenko, V.

    2014-08-01

    The precipitation of energetic neutral atoms, produced through charge exchange collisions between solar wind ions and thermal atmospheric gases, is investigated for the Martian atmosphere. Connections between parameters of precipitating fast ions and resulting escape fluxes, altitude-dependent energy distributions of fast atoms and their coefficients of reflection from the Mars atmosphere, are established using accurate cross sections in Monte Carlo (MC) simulations. Distributions of secondary hot (SH) atoms and molecules, induced by precipitating particles, have been obtained and applied for computations of the non-thermal escape fluxes. A new collisional database on accurate energy-angular-dependent cross sections, required for description of the energy-momentum transfer in collisions of precipitating particles and production of non-thermal atmospheric atoms and molecules, is reported with analytic fitting equations. Three-dimensional MC simulations with accurate energy-angular-dependent cross sections have been carried out to track large ensembles of energetic atoms in a time-dependent manner as they propagate into the Martian atmosphere and transfer their energy to the ambient atoms and molecules. Results of the MC simulations on the energy-deposition altitude profiles, reflection coefficients, and time-dependent atmospheric heating, obtained for the isotropic hard sphere and anisotropic quantum cross sections, are compared. Atmospheric heating rates, thermalization depths, altitude profiles of production rates, energy distributions of SH atoms and molecules, and induced escape fluxes have been determined.

  20. Design of the microsatellites used in the atmospheric neutral density experiment

    NASA Astrophysics Data System (ADS)

    Kalmanson, Phillip C.; Nicholas, Andrew C.; Thonnard, Stefan E.; Galysh, Ivan; Bruninga, Robert

    2005-01-01

    The Atmospheric Neutral Density Experiment (ANDE) is a series of four microsatellites that will study the atmosphere of the Earth from low earth orbit. Each microsatellite is based on a common design; however, each differs in the instrument payloads and the associated science and mission requirements. The primary mission objective is to provide total neutral density along the orbit for improved orbit determination of resident space objects. Each ANDE microsatellite has several secondary goals. It is the unique design of the microsatellites that allows this task to be accomplished. Each microsatellite is a compact, near perfect sphere; this reduces shape and drag errors so that the local density of the atmosphere can be determined by instantaneous tracking variations detected by very high accuracy laser and radar ranging whereby the spacecrafts themselves are the primary sensing instrument. The accuracy of the atmospheric density measurements inferred from the orbital tracking of ANDE microsatellites will be much greater than that achieved by similar experiments in the past or from any currently proposed. Many unique design challenges had to be overcome to achieve the necessary science, mission, and operational requirements as well as severe cost constraints. New methods for parts and assembly fabrication were sought out and implemented. These new methods allowed similar parts to function in each of the microsatellites despite the differences between them. In addition, the command and telemetry links used inexpensive COTS Ham radio transceivers while meeting all the International requirements for operations in the Amateur Satellite Service.

  1. Experimental Investigation of Soil and Atmospheric Conditions on the Momentum, Mass, and Thermal Boundary Layers Above the Land Atmosphere Interface

    NASA Astrophysics Data System (ADS)

    Trautz, A.; Smits, K. M.; Illangasekare, T. H.; Schulte, P.

    2014-12-01

    The purpose of this study is to investigate the impacts of soil conditions (i.e. soil type, saturation) and atmospheric forcings (i.e. velocity, temperature, relative humidity) on the momentum, mass, and temperature boundary layers. The atmospheric conditions tested represent those typically found in semi-arid and arid climates and the soil conditions simulate the three stages of evaporation. The data generated will help identify the importance of different soil conditions and atmospheric forcings with respect to land-atmospheric interactions which will have direct implications on future numerical studies investigating the effects of turbulent air flow on evaporation. The experimental datasets generated for this study were performed using a unique climate controlled closed-circuit wind tunnel/porous media facility located at the Center for Experimental Study of Subsurface Environmental Processes (CESEP) at the Colorado School of Mines. The test apparatus consisting of a 7.3 m long porous media tank and wind tunnel, were outfitted with a sensor network to carefully measure wind velocity, air and soil temperature, relative humidity, soil moisture, and soil air pressure. Boundary layer measurements were made between the heights of 2 and 500 mm above the soil tank under constant conditions (i.e. wind velocity, temperature, relative humidity). The soil conditions (e.g. soil type, soil moisture) were varied between datasets to analyze their impact on the boundary layers. Experimental results show that the momentum boundary layer is very sensitive to the applied atmospheric conditions and soil conditions to a much less extent. Increases in velocity above porous media leads to momentum boundary layer thinning and closely reflect classical flat plate theory. The mass and thermal boundary layers are directly dependent on both atmospheric and soil conditions. Air pressure within the soil is independent of atmospheric temperature and relative humidity - wind velocity and soil

  2. Improvements in simulation of atmospheric boundary layer parameters through data assimilation in ARPS mesoscale atmospheric model

    NASA Astrophysics Data System (ADS)

    Subrahamanyam, D. Bala; Ramachandran, Radhika; Kunhikrishnan, P. K.

    2006-12-01

    In a broad sense, 'Data Assimilation' refers to a technique, whereby the realistic observational datasets are injected to a model simulation for bringing accurate forecasts. There are several schemes available for insertion of observational datasets in the model. In this piece of research, we present one of the simplest, yet powerful data assimilation techniques - known as nudging through optimal interpolation in the ARPS (Advanced Regional Prediction System) model. Through this technique, we firstly identify the assimilation window in space and time over which the observational datasets need to be inserted and the model products require to be adjusted. Appropriate model variables are then adjusted for the realistic observational datasets with a proper weightage being given to the observations. Incorporation of such a subroutine in the model that takes care of the assimilation in the model provides a powerful tool for improving the forecast parameters. Such a technique can be very useful in cases, where observational datasets are available at regular intervals. In this article, we demonstrate the effectiveness of this technique for simulation of profiles of Atmospheric Boundary Layer parameters for a tiny island of Kaashidhoo in the Republic of Maldives, where regular GPS Loran Atmospheric Soundings were carried out during the Intensive Field Phase of Indian Ocean Experiment (INDOEX, IFP-99).

  3. Simultaneous profiling of the Arctic Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    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

  4. Rocketborne Rayleigh lidar for in situ measurements of neutral atmospheric density.

    PubMed

    Eriksen, T; Hoppe, U P; Thrane, E V; Blix, T A

    1999-04-20

    We describe the design of a small Rayleigh scattering lidar for launch on a sounding rocket as well as the first, to our knowledge, in situ measurements of neutral number density performed with a rocketborne lidar in the mesosphere. The aim of the experiment is to study the dynamics of the neutral atmosphere with emphasis on turbulent structures and gravity waves. The altitude resolution of the density profile is better than 10 m. The uncertainty is 0.3% below 55 km and better than 1% to an altitude of 65 km. The lidar technique meets the requirement of measurement of total molecular density outside the shock front surrounding the supersonic payload, which is necessary for precision measurements of neutral atmospheric density. We have compared different component technologies and design approaches and show performance calculations for two electro-optical systems. The first system has laser and detector components that were available in 1993, the second has new solutions that became available in 1995. The second system has a signal-to-noise ratio that is five times higher than the first and employs a pulsed high-power laser diode array as the transmitter and a large-area avalanche photodiode as the receiver.

  5. Vertical structure of the ionosphere and upper neutral atmosphere of saturn from the pioneer radio occultation.

    PubMed

    Kliore, A J; Lindal, G F; Patel, I R; Sweetnam, D N; Hotz, H B; McDonough, T R

    1980-01-25

    Radio occultation measurements at S band (2.293 gigahertz) of the ionosphere and upper neutral atmosphere of Saturn were obtained during the flyby of the Pioneer 11 Saturn spacecraft on 5 September 1979. Preliminary analysis of the occultation exit data taken at a latitude of 9.5 degrees S and a solar zenith angle of 90.6 degrees revealed the presence of a rather thin ionosphere, having a main peak electron density of about 9.4 x 10/(3) per cubic centimeter at an altitude of about 2800 above the level of a neutral number density of 10(19) per cubic centimeter and a lower peak of about 7 x 10(3) per cubic centimeter at 2200 kilometers. Data in the neutral atmosphere were obtained to a pressure level of about 120 millibars. The temperature structure derived from these data is consistent with the results of the Pioneer 11 Saturn infrared radiometer experiment (for a helium fraction of 15 percent) and with models derived from Earth-based observations for a helium fraction by number of about 4 to 10 percent. The helium fraction will be further defined by mutual iteration with the infrared radiometer team.

  6. The climatic features of the atmospheric boundary layer above the south of western Siberia

    NASA Astrophysics Data System (ADS)

    Komarov, V. S.; Lomakina, N. Ya.

    2006-11-01

    Troposphere and, in particular, the atmospheric boundary layer play a considerable role in propagation and transformation of optical radiation. Therefore, data on vertical statistical structure of meteorological fields in the boundary layer are necessary for solution of various applied problems of atmospheric optics. In the work, climatic features of the atmospheric boundary layer above the south of Western Siberia are considered. The research was conducted for winter and summer using the date of four-years (2002.2005 years) observations of 4 aerologic stations (Ekaterinburg, Omsk, Novosibirsk and Krasnoyarsk). The vertical structures of average values and mean square deviations of temperature, humidity and wind for 10 high-altitude levels (up to 1600 M), as well as the corresponding correlation matrixes and results of their expansion on empirical orthogonal functions were used for detailed studying of climatic features of atmospheric boundary layer. The obtained results are presented.`

  7. Atmospheric Boundary Layer Modeling for Combined Meteorology and Air Quality Systems

    EPA Science Inventory

    Atmospheric Eulerian grid models for mesoscale and larger applications require sub-grid models for turbulent vertical exchange processes, particularly within the Planetary Boundary Layer (PSL). In combined meteorology and air quality modeling systems consistent PSL modeling of wi...

  8. Atmospheric Boundary Layer Modeling for Combined Meteorology and Air Quality Systems

    EPA Science Inventory

    Atmospheric Eulerian grid models for mesoscale and larger applications require sub-grid models for turbulent vertical exchange processes, particularly within the Planetary Boundary Layer (PSL). In combined meteorology and air quality modeling systems consistent PSL modeling of wi...

  9. Neutral and charged clusters in the atmosphere - Their importance and potential role in heterogeneous catalysis

    NASA Technical Reports Server (NTRS)

    Castleman, A. W., Jr.

    1982-01-01

    An assessment is presented of current knowledge concerning the role and importance of neutral and charged clusters in atmospheric heterogeneous catalysis, with a view to the recommendation of future studies needed for progress in the quantification of aerosol formation and catalytic reactivity. It is established that nucleation from the gaseous to the aerosol state commences via the formation of clusters among molecules participating in the phase-transformation process. Nucleation may proceed in some cases by way of the formation of prenucleation embryos, which then evolve through the energy barrier and undergo phase transformation. In other cases, cluster-cluster interaction among neutral particles or stagewise building of alternate-sign ion clusters may be important in the gas-to-particle conversion process.

  10. Neutral and charged clusters in the atmosphere - Their importance and potential role in heterogeneous catalysis

    NASA Technical Reports Server (NTRS)

    Castleman, A. W., Jr.

    1982-01-01

    An assessment is presented of current knowledge concerning the role and importance of neutral and charged clusters in atmospheric heterogeneous catalysis, with a view to the recommendation of future studies needed for progress in the quantification of aerosol formation and catalytic reactivity. It is established that nucleation from the gaseous to the aerosol state commences via the formation of clusters among molecules participating in the phase-transformation process. Nucleation may proceed in some cases by way of the formation of prenucleation embryos, which then evolve through the energy barrier and undergo phase transformation. In other cases, cluster-cluster interaction among neutral particles or stagewise building of alternate-sign ion clusters may be important in the gas-to-particle conversion process.

  11. Small-scale plasma, magnetic, and neutral density fluctuations in the nightside Venus atmosphere

    NASA Technical Reports Server (NTRS)

    Hoegy, W. R.; Brace, L. H.; Kasprzak, W. T.; Russell, C. T.

    1990-01-01

    The evolution of the Venus small-scale waves as they propagate into the nightsite is examined, and the small-scale structures are compared with the waves in the three components of the magnetic field, magnetic dip angle, and neutral density. It is demonstrated that the small-scale fluctuations evolve between the transterminator and antisolar regions. It is shown that atmospheric gravity waves may also be producing some of the fluctuations observed at longer wavelengths. The electron temperature and density are shown to be approximately 180 deg out of phase and exhibiting the highest correlation of any pair of variables. Waves in the electron and neutral densities are found to be correlated moderately on most orbits, while the average electron temperature is higher when the average magnetic field is more horizontal.

  12. Dynamics of the atmospheric boundary layer during the 1980 total solar eclipse

    SciTech Connect

    SethuRaman, S

    1981-01-01

    An atmospheric boundary layer experiment was conducted at Raichur, India to study the variations in the surface shear stress, heat flux and the meteorological processes that take place during a total solar eclipse. Interesting results were observed regarding the evolution of the planetary boundary layer. Changes in atmospheric stability from unstable to stable to unstable were observed during different phases of the eclipse. Downward propagation of negative heat flux associated with decreasing scales of convective eddies was also observed during the eclipse.

  13. Wind sensing in an atmospheric boundary layer by means of micropulse coherent Doppler lidars

    NASA Astrophysics Data System (ADS)

    Banakh, V. A.; Smalikho, I. N.

    2016-07-01

    An algorithm is developed and computer simulation of wind sensing by means of micropulse coherent Doppler lidars (CDLs) in the atmospheric boundary layer is conducted for low values of the signalto- noise (SNR) ratio. The accuracy of lidar wind measurements is studied numerically for parameters of micropulse Stream Line CDLs. Optimal parameters of the measurements and processing data obtained at low SNR, which allow reconstructing vertical profiles of the wind velocity vector with required accuracy within an entire atmospheric boundary layer, are determined.

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

    SciTech Connect

    Vijayakumar, Ganesh; Brasseur, James; Lavely, Adam; Jayaraman, Balaji; Craven, Brent

    2016-01-04

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

  15. One-dimensional simulation of temperature and moisture in atmospheric and soil boundary layers

    NASA Technical Reports Server (NTRS)

    Bornstein, R. D.; Santhanam, K.

    1981-01-01

    Meteorologists are interested in modeling the vertical flow of heat and moisture through the soil in order to better simulate the vertical and temporal variations of the atmospheric boundary layer. The one dimensional planetary boundary layer model of is modified by the addition of transport equations to be solved by a finite difference technique to predict soil moisture.

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

    NASA Astrophysics Data System (ADS)

    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.

  17. Models of neutral cometary atmospheres for the interpretation of spectroscopic observations

    NASA Astrophysics Data System (ADS)

    Tkachuk, A. Iu.

    1985-07-01

    Various models of neutral cometary atmospheres are compared. It is shown that Haser's formula can be applied to primary molecules. The collision sphere is taken into account in models of secondary molecules, and a model for the neighborhood of the nucleus is examined. Models analogous to those for secondary molecules with allowance for the collision sphere are used for tertiary molecules. Consideration is also given to the Monte Carlo model, and it is noted that this is the only model that can be used in the nonspherically symmetric case.

  18. The open-source neutral-mass spectrometer on Atmosphere Explorer-C, -D, and -E.

    NASA Technical Reports Server (NTRS)

    Nier, A. O.; Potter, W. E.; Hickman, D. R.; Mauersberger, K.

    1973-01-01

    The open-source mass spectrometer will be used to obtain the number densities of the neutral atmospheric gases in the mass range 1 to 48 amu at the satellite location. The ion source has been designed to allow gas particles to enter the ionizing region with the minimum practicable number of prior collisions with surfaces. This design minimizes the loss of atomic oxygen and other reactive species due to reactions with the walls of the ion source. The principal features of the open-source spectrometer and the laboratory calibration system are discussed.

  19. The Neutral Mass Spectrometer on the Lunar Atmosphere and Dust Environment Explorer Mission

    NASA Technical Reports Server (NTRS)

    Mahaffy, Paul R.; Hodges, R. Richard; Benna, Mehdi; King, Todd; Arvey, Robert; Barciniak, Michael; Bendt, Mirl; Carigan, Daniel; Errigo, Therese; Harpold, Daniel N.; Holmes, Vincent; Johnson, Christopher S.; Kellogg, James; Kimvilakani, Patrick; Lefavor, Matthew; Hengemihle, Jerome; Jaeger, Ferzan; Lyness, Eric; Maurer, John; Nguyen, Daniel; Nolan, Thomas; Noreiga, Felix; Noreiga, Marvin; Patel, Kiran; Prats, Benito; Quinones, Omar; Raaen, Eric; Tan, Florence; Weidner, Edwin; Woronowicz, Michael; Gundersen, Cynthia (Inventor); Battel, Steven; Block, Bruce P.; Arnett, Ken; Miller, Ryan

    2014-01-01

    The Neutral Mass Spectrometer (NMS) of the Lunar Atmosphere and Dust Environment Explorer (LADEE) Mission is designed to measure the composition and variability of the tenuous lunar atmosphere. The NMS complements two other instruments on the LADEE spacecraft designed to secure spectroscopic measurements of lunar composition and in situ measurement of lunar dust over the course of a 100-day mission in order to sample multiple lunation periods. The NMS utilizes a dual ion source designed to measure both surface reactive and inert species and a quadrupole analyzer. The NMS is expected to secure time resolved measurements of helium and argon and determine abundance or upper limits for many other species either sputtered or thermally evolved from the lunar surface.

  20. SEPARATION OF THE INTERSTELLAR BOUNDARY EXPLORER RIBBON FROM GLOBALLY DISTRIBUTED ENERGETIC NEUTRAL ATOM FLUX

    SciTech Connect

    Schwadron, N. A.; Kucharek, H.; Moebius, E. E-mail: harald.kucharek@unh.edu

    2011-04-10

    The Interstellar Boundary Explorer (IBEX) observes a remarkable feature, the IBEX ribbon, which has energetic neutral atom (ENA) flux over a narrow region {approx}20{sup 0} wide, a factor of 2-3 higher than the more globally distributed ENA flux. Here, we separate ENA emissions in the ribbon from the distributed flux by applying a transparency mask over the ribbon and regions of high emissions, and then solve for the distributed flux using an interpolation scheme. Our analysis shows that the energy spectrum and spatial distribution of the ribbon are distinct from the surrounding globally distributed flux. The ribbon energy spectrum shows a knee between {approx}1 and 4 keV, and the angular distribution is approximately independent of energy. In contrast, the distributed flux does not show a clear knee and more closely conforms to a power law over much of the sky. Consistent with previous analyses, the slope of the power law steepens from the nose to tail, suggesting a weaker termination shock toward the tail as compared to the nose. The knee in the energy spectrum of the ribbon suggests that its source plasma population is generated via a distinct physical process. Both the slope in the energy distribution of the distributed flux and the knee in the energy distribution of the ribbon are ordered by latitude. The heliotail may be identified in maps of globally distributed flux as a broad region of low flux centered {approx}44{sup 0}W of the interstellar downwind direction, suggesting heliotail deflection by the interstellar magnetic field.

  1. Latitudinal and Energy Dependence of Energetic Neutral Atom Spectral Indices Measured by the Interstellar Boundary Explorer

    NASA Astrophysics Data System (ADS)

    Desai, M. I.; Allegrini, F.; Dayeh, M. A.; Funsten, H.; Heerikhuisen, J.; McComas, D. J.; Fuselier, S. A.; Pogorelov, N.; Schwadron, N. A.; Zank, G. P.; Zirnstein, E. J.

    2015-04-01

    We investigate the latitudinal and energy dependence of the globally distributed 0.5-6 keV energetic neutral atom (ENA) spectra measured by the Interstellar Boundary Explorer (IBEX) during the first 3 yrs of the mission. Our results are: (1) the ENA spectral indices at the two lowest energies (0.89 and 1.47 keV) exhibit no clear trend with ecliptic latitude θ, while those at ˜2.29 and ˜3.41 keV exhibit a clear latitudinal pattern; flatter spectra occur above 60° latitude and steeper spectra occur ±30° of the equator. (2) The latitudinal dependence of the spectral indices at different energies can be represented by the cosine function γ ={{a}0}+{{a}1}cos ({{a}2}θ ) with unique offsets, amplitudes, and phase angles; the higher energy ENA indices transition to successively larger amplitudes within ±45° of the equator. Our results confirm the previously reported latitudinal organization of the ENA spectra and their remarkable similarity to that of the solar wind (SW) speed observed by Ulysses in the inner heliosphere. While earlier studies showed that the ˜0.5-6 keV globally distributed ENA spectral indices could be represented as single power laws over much of the sky, our new results indicate that this is an over-simplification because the spectral indices have an energy and latitude dependence. This dependence is an important factor that must be taken into consideration by models and simulations that seek to map the IBEX ENA observations back to the latitudinal profile of the SW speed structure observed in the inner heliosphere.

  2. Latittudinal and energy dependence of energetic neutral atom spectral indices measured by the Interstellar Boundary Explorer

    DOE PAGES

    Desai, M. I.; Allegrini, F.; Dayeh, M. A.; ...

    2015-03-30

    Here, we investigate the latitudinal and energy dependence of the globally distributed 0.5-6 keV energetic neutral atom (ENA) spectra measured by the Interstellar Boundary Explorer (IBEX) during the first 3 yrs of the mission. Our results are: (1) the ENA spectral indices at the two lowest energies (0.89 and 1.47 keV) exhibit no clear trend with ecliptic latitude θ, while those at ~2.29 and ~3.41 keV exhibit a clear latitudinal pattern; flatter spectra occur above 60° latitude and steeper spectra occur ±30° of the equator. (2) The latitudinal dependence of the spectral indices at different energies can be represented bymore » the cosine function γ =a0 + a1 cos (a2θ) with unique offsets, amplitudes, and phase angles; the higher energy ENA indices transition to successively larger amplitudes within ±45° of the equator. The results confirm the previously reported latitudinal organization of the ENA spectra and their remarkable similarity to that of the solar wind (SW) speed observed by Ulysses in the inner heliosphere. And while earlier studies showed that the ~0.5-6 keV globally distributed ENA spectral indices could be represented as single power laws over much of the sky, our new results indicate that this is an over-simplification because the spectral indices have an energy and latitude dependence. Furthermore, this dependence is an important factor that must be taken into consideration by models and simulations that seek to map the IBEX ENA observations back to the latitudinal profile of the SW speed structure observed in the inner heliosphere.« less

  3. Latittudinal and energy dependence of energetic neutral atom spectral indices measured by the Interstellar Boundary Explorer

    SciTech Connect

    Desai, M. I.; Allegrini, F.; Dayeh, M. A.; Funsten, H.; Heerikhuisen, J.; McComas, D. J.; Fuselier, S. A.; Pogorelov, N.; Schwadron, N. A.; Zank, G. P.; Zirnstein, E. J.

    2015-03-30

    Here, we investigate the latitudinal and energy dependence of the globally distributed 0.5-6 keV energetic neutral atom (ENA) spectra measured by the Interstellar Boundary Explorer (IBEX) during the first 3 yrs of the mission. Our results are: (1) the ENA spectral indices at the two lowest energies (0.89 and 1.47 keV) exhibit no clear trend with ecliptic latitude θ, while those at ~2.29 and ~3.41 keV exhibit a clear latitudinal pattern; flatter spectra occur above 60° latitude and steeper spectra occur ±30° of the equator. (2) The latitudinal dependence of the spectral indices at different energies can be represented by the cosine function γ =a0 + a1 cos (a2θ) with unique offsets, amplitudes, and phase angles; the higher energy ENA indices transition to successively larger amplitudes within ±45° of the equator. The results confirm the previously reported latitudinal organization of the ENA spectra and their remarkable similarity to that of the solar wind (SW) speed observed by Ulysses in the inner heliosphere. And while earlier studies showed that the ~0.5-6 keV globally distributed ENA spectral indices could be represented as single power laws over much of the sky, our new results indicate that this is an over-simplification because the spectral indices have an energy and latitude dependence. Furthermore, this dependence is an important factor that must be taken into consideration by models and simulations that seek to map the IBEX ENA observations back to the latitudinal profile of the SW speed structure observed in the inner heliosphere.

  4. Titan's atmospheric sputtering and neutral torus produced by magnetospheric and pick-up ions

    NASA Astrophysics Data System (ADS)

    Michael, M.; Smith, H. T.; Johnson, R. E.; Shematovich, V.; Leblanc, F.; Ledvina, S.; Luhmann, J. H.

    As Titan does not possess an intrinsic magnetic field, Kronian magnetospheric ions can penetrate Titan's exobase as can locally produced pick-up ions (e.g. Shematovich et al. 2003). This can cause atmospheric loss and heating of the exobase region. Penetration by slowed and deflected magnetospheric ions and by the pick-up ions is described here using a 3-D Monte Carlo model (Michael et al. 2004). The incident ions can lead to the production of fast neutrals that collide with other atmospheric neutrals producing the ejection of both atomic and molecular nitrogen and heating. The recently calculated dissociation cross sections of N2 are used in the present model (Tully and Johnson 2002). The incident flux of slowed magnetospheric N+ ions and pick-up C2H5+ ions is estimated from the work of Brecht et al. (2000). These ions, which have energies less than 1.2 keV, were shown to be more efficient in ejecting material from Titan's atmosphere than the non-deflected co-rotating ions used earlier (Lammer et al. 1993). The loss rates are comparable or larger than those produced by photo-dissociation. Exobse heating rates are given and the loss rates of N and N2 are then used as a source of nitrogen for the Titan neutral torus. If atmospheric sputtering is important this torus will contain both atomic and molecular nitrogen and, therefore, will provide a distributed source of both atomic and molecular nitrogen ions that will be readily detected by Cassini (Smith et al. 2004) Acknowledgment: This work is supported by NASA's Planetary Atmospheres Program and by the CAPS-Cassini Instrument. Brecht, S.H., J.G. Luhmann, and D.J. Larson, J. Geophys. Res., 105, 13119, 2000. Lammer, H., and S.J. Bauer,. Planet. Space Sci., 41, 657, 1993. Shematovich, V.I.,et al, J. Geophys. Res., 108, 5086, 10.1029/2003JE002096, 2003. Michael, M. et al., submitted, Icarus, 2004. Smith, H.T., et al., Titan Aeronomy Workshop, Paris, January 7-9, 2004. Tully, C., R.E. Johnson, J. Chem. Phys. 117, 6556

  5. FLUID MODELING OF ATMOSPHERIC DISPERSION IN THE CONVECTIVE BOUNDARY LAYER

    EPA Science Inventory

    Study of convective boundary layer (CBL) processes has depended largely upon laboratory analogs for many years. The pioneering work of Willis and Deardorff (1974) and some 35 subsequent papers by the same authors showed that much useful research could be accomplished with a re...

  6. FLUID MODELING OF ATMOSPHERIC DISPERSION IN THE CONVECTIVE BOUNDARY LAYER

    EPA Science Inventory

    Study of convective boundary layer (CBL) processes has depended largely upon laboratory analogs for many years. The pioneering work of Willis and Deardorff (1974) and some 35 subsequent papers by the same authors showed that much useful research could be accomplished with a re...

  7. Early Observations of the Upper Atmosphere and Ionosphere of Mars by MAVEN’s Neutral Gas and Ion Mass Spectrometer

    NASA Astrophysics Data System (ADS)

    Benna, Mehdi; Mahaffy, Paul R.; Elrod, Meredith

    2015-04-01

    The Neutral Gas and Ion Mass Spectrometer (NGIMS) of the Mars Atmosphere and Volatile Evolution (MAVEN) Mission is designed to characterize the source region of escaping atoms in the upper atmosphere and ionosphere of Mars. The NGIMS instrument is a quadrupole analyzer with a mass rang of 2-150 Da. It utilizes a dual ion source in order to measure both surface reactive neutrals (using the Open Source Neutral mode - OSN), inert neutrals (using the Closed Source Neutral mode - CSN), and thermal ions (using the Open Source Ion mode - OSI) at altitudes below 500 km.In the first few months of the MAVEN mission, NGIMS alternated on sequential orbits between measurement sequences that focus on fully characterizing neutral species (using the CSN/OSN modes) and ions (using the CSN/OSI modes). The collected data revealed the substantial structure present in both neutral and ion densities with spatial scales of hundreds of kilometers along the spacecraft track. The data also brought to light the sharp contrast between the day side and night side atmospheric profiles of neutrals and ions in both total density and relative abundance.

  8. Miniaturized Ion and Neutral Mass Spectrometer for CubeSat Atmospheric Measurements

    NASA Technical Reports Server (NTRS)

    Rodriguez, M.; Paschalidis, N.; Jones, S.; Sittler, E.; Chornay, D.; Uribe, P.; Cameron, T.

    2016-01-01

    To increase the number of single point in-situ measurements of thermosphere and exosphere ion and neutral composition and density, miniaturized instrumentation is in high demand to take advantage of the increasing platform opportunities available in the smallsat/cubesat industry. The INMS (Ion-Neutral Mass Spectrometer) addresses this need by providing simultaneous measurements of both the neutral and ion environment, essentially providing two instruments in one compact model. The 1.3U volume, 570 gram, 1.8W nominal power INMS instrument makes implementation into cubesat designs (3U and above) practical and feasible. With high dynamic range (0.1-500eV), mass dynamic range of 1-40amu, sharp time resolution (0.1s), and mass resolution of MdM16, the INMS instrument addresses the atmospheric science needs that otherwise would have required larger more expensive instrumentation. INMS-v1 (version 1) launched on Exocube (CalPoly 3U cubesat) in 2015 and INMS-v2 (version 2) is scheduled to launch on Dellingr (GSFC 6U cubesat) in 2017. New versions of INMS are currently being developed to increase and add measurement capabilities, while maintaining its smallsat/cubesat form.

  9. Neutral Mass Spectrometer (NMS) for the Lunar Atmosphere and Dust Environment Explorer (LADEE) Mission

    NASA Technical Reports Server (NTRS)

    Collier, Michael R.; Mahaffy, Paul R.; Benna, Mehdi; King, Todd T.; Hodges, Richard

    2011-01-01

    The Lunar Atmosphere and Dust Environment Explorer (LADEE) mission currently scheduled for launch in early 2013 aboard a Minotaur V will orbit the moon at a nominal periselene of 50 km to characterized the lunar atmosphere and dust environment. The science instrument payload includes a neutral mass spectrometer as well as an ultraviolet spectrometer and a dust detector. Although to date only He, Ar-40, K, Na and Rn-222 have been firmly identified in the lunar exosphere and arise from the solar wind (He), the lunar regolith (K and Na) and the lunar interior (Ar-40, Rn-222), upper limits have been set for a large number of other species, LADEE Neutral Mass Spectrometer (NMS) observations will determine the abundance of several species and substantially lower the present upper limits for many others. Additionally, LADEE NMS will observe the spatial distribution and temporal variability of species which condense at nighttime and show peak concentrations at the dawn terminator (e,g, Ar-40), possible episodic release from the lunar interior, and the results of sputtering or desorption processes from the regolith. In this presentation, we describe the LADEE NMS hardware and the anticipated science results.

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

    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-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 observed

  11. Turbulence structure of the marine atmospheric boundary layer observed during the SEMAPHORE experiment

    SciTech Connect

    Durand, P.; Benech, B.; Druilhet, A.; Ferret, B.

    1994-12-31

    The SEMAPHORE experiment was conducted in the Azores region in 1993 and was devoted to mesoscale studies of oceanic and atmospheric circulations, as well as interactions between oceanic and atmospheric boundary layers. From October 4 to November 17, two instrumented aircraft gathered data. One of the major objectives of SEMAPHORE was to study the coupling between the atmospheric and oceanic boundary layers in the vicinity of an oceanic temperature front. This front, associated with the Azores current, was located south of the Santa Maria Island where the aircraft were based. The aim of this paper is to document the turbulent structure of the atmospheric boundary layer, analyzed from aircraft measurements, for two different meteorological situations.

  12. Study of EM Signals Propagation Through Marine Atmospheric Boundary Layer

    DTIC Science & Technology

    2002-09-30

    transmision properties. REFERENCES Barrick, D.E., and Weber, B.L., ’On the nonlinear theory for gravity waves on the ocean’s surface. Part II...and Friehe C., 2000. Boundary-Layer Meteorology, 97, 293-307. Ishimaru, A. 1978, Wave propagation and scattering in random media . Academic Press...Irvine. Rytov, S. M., Y. A. Kravtsov, and V. I. Tatarskii: 1987, Principles of statistical radiophysics 4: Wave propagation through random media

  13. Direct Numerical Simulations of Very Stable Atmospheric Boundary Layers

    DTIC Science & Technology

    2012-01-10

    Ekman boundary layers. Very high resolution, three-dimensional, time-dependent simulations are carried out on computational grids of the order of...turbulent Ekman layers", Annual Meeting of the Division of Fluid Dynamics of the American Physical Society, Long Beach. O Flores and JJ Riley. August...September, 2011. "DNS of a strati ed Ekman layer with a capping inversion", 13th European Turbulence Conference, Warsaw, Poland. Number of

  14. Analysis of wave-like oscillations in parameters of sporadic E layer and neutral atmosphere

    NASA Astrophysics Data System (ADS)

    Mošna, Z.; Koucká Knížová, P.

    2012-12-01

    The present study mainly concerns the wave-like activity in the ionospheric sporadic E layer (Es) and in the lower lying stratosphere. The proposed analysis involves parameters describing the state of plasma in the sporadic E layer. Critical frequencies foEs and layer heights hEs were measured at the Pruhonice station (50°N, 14.5°E) during summer campaigns 2004, 2006 and 2008. Further, we use neutral atmosphere (temperature data at 10 hPa) data from the same time interval. The analysis concentrates on vertically propagating wave-like structures within distant atmospheric regions. By means of continuous wavelet transform (CWT) we have detected significant wave-like oscillation at periods covering tidal and planetary oscillation domains both in the Es layer parameters (some of them were reported earlier, for instance in works of Abdu et al., 2003; Pancheva and Mitchel, 2004; Pancheva et al., 2003; Šauli and Bourdillon, 2008) and in stratospheric temperature variations. Further analyses using cross wavelet transform (XWT) and wavelet coherence analysis (WTC) show that despite high wave-like activity in a wide period range, there are only limited coherent wave-like bursts present in both spectra. Such common coherent wave bursts occur on periods close to eigen-periods of the terrestrial atmosphere. We suppose that vertical coupling between atmospheric regions realized by vertically propagating planetary waves occurs predominantly on periods close to those of Rossby modes. Analysis of the phase shift between data from distant atmospheric regions reveals high variability and very likely supports the non-linear scenario of the vertical coupling provided by planetary waves.

  15. Measurement Science of the Intermittent Atmospheric Boundary Layer

    DTIC Science & Technology

    2014-01-01

    meridionally by 40 m), eight ultrasonic anemometers, two low-response thermometers, two low-response hygrometers, three quartz-crystal barometers , and...has been operating with eight sonics and three quartz-crystal barometers almost without interruption since June 2013 1 • The quartz-crystal... barometers have been arranged in the form of a triangle of 40 m spacing, and the barometer array has effectively detected atmospheric infrasound (including

  16. Turbulent kinetics of a large wind farm and their impact in the neutral boundary layer

    DOE PAGES

    Na, Ji Sung; Koo, Eunmo; Munoz-Esparza, Domingo; ...

    2015-12-28

    High-resolution large-eddy simulation of the flow over a large wind farm (64 wind turbines) is performed using the HIGRAD/FIRETEC-WindBlade model, which is a high-performance computing wind turbine–atmosphere interaction model that uses the Lagrangian actuator line method to represent rotating turbine blades. These high-resolution large-eddy simulation results are used to parameterize the thrust and power coefficients that contain information about turbine interference effects within the wind farm. Those coefficients are then incorporated into the WRF (Weather Research and Forecasting) model in order to evaluate interference effects in larger-scale models. In the high-resolution WindBlade wind farm simulation, insufficient distance between turbines createsmore » the interference between turbines, including significant vertical variations in momentum and turbulent intensity. The characteristics of the wake are further investigated by analyzing the distribution of the vorticity and turbulent intensity. Quadrant analysis in the turbine and post-turbine areas reveals that the ejection motion induced by the presence of the wind turbines is dominant compared to that in the other quadrants, indicating that the sweep motion is increased at the location where strong wake recovery occurs. Regional-scale WRF simulations reveal that although the turbulent mixing induced by the wind farm is partly diffused to the upper region, there is no significant change in the boundary layer depth. The velocity deficit does not appear to be very sensitive to the local distribution of turbine coefficients. However, differences of about 5% on parameterized turbulent kinetic energy were found depending on the turbine coefficient distribution. Furthermore, turbine coefficients that consider interference in the wind farm should be used in wind farm parameterization for larger-scale models to better describe sub-grid scale turbulent processes.« less

  17. Turbulent kinetics of a large wind farm and their impact in the neutral boundary layer

    SciTech Connect

    Na, Ji Sung; Koo, Eunmo; Munoz-Esparza, Domingo; Jin, Emilia Kyung; Linn, Rodman; Lee, Joon Sang

    2015-12-28

    High-resolution large-eddy simulation of the flow over a large wind farm (64 wind turbines) is performed using the HIGRAD/FIRETEC-WindBlade model, which is a high-performance computing wind turbine–atmosphere interaction model that uses the Lagrangian actuator line method to represent rotating turbine blades. These high-resolution large-eddy simulation results are used to parameterize the thrust and power coefficients that contain information about turbine interference effects within the wind farm. Those coefficients are then incorporated into the WRF (Weather Research and Forecasting) model in order to evaluate interference effects in larger-scale models. In the high-resolution WindBlade wind farm simulation, insufficient distance between turbines creates the interference between turbines, including significant vertical variations in momentum and turbulent intensity. The characteristics of the wake are further investigated by analyzing the distribution of the vorticity and turbulent intensity. Quadrant analysis in the turbine and post-turbine areas reveals that the ejection motion induced by the presence of the wind turbines is dominant compared to that in the other quadrants, indicating that the sweep motion is increased at the location where strong wake recovery occurs. Regional-scale WRF simulations reveal that although the turbulent mixing induced by the wind farm is partly diffused to the upper region, there is no significant change in the boundary layer depth. The velocity deficit does not appear to be very sensitive to the local distribution of turbine coefficients. However, differences of about 5% on parameterized turbulent kinetic energy were found depending on the turbine coefficient distribution. Furthermore, turbine coefficients that consider interference in the wind farm should be used in wind farm parameterization for larger-scale models to better describe sub-grid scale turbulent processes.

  18. High resolution properties of the equatorial Pacific marine atmospheric boundary layer from lidar and radiosonde observations

    SciTech Connect

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

    1994-10-01

    Water vapor and relative aerosol concentration were measured with two shipboard lidars from the ocean surface to tropospheric and lower stratospheric altitudes in support of the Central Equatorial Pacific Experiment (CEPEX) program. The goal of CEPEX is to evaluate the ``thermostat`` hypothesis regarding feedback mechanisms between the tropical ocean and the atmosphere. This paper describes some of the features observed with the first two kilometers of the equatorial troposphere, known as the marine Atmospheric Boundary Layer (ABL), as well as the coupling between the ocean and the atmosphere. This paper will present the initial analysis of the structure of the atmospheric boundary layer. Finally, we will look at the implications of this structure for ocean-atmosphere coupling by comparing the height of the mixing layer with sea surface temperatures and other factors.

  19. Watershed Scale Shear Stress From Tethersonde Wind Profile Measurements Under Near Neutral and Unstable Atmospheric Stability

    NASA Astrophysics Data System (ADS)

    Parlange, M. B.; Katul, G. G.

    1995-04-01

    Mean wind speed profiles were measured in the atmospheric surface layer, using a tethersonde system, above the Ojai Valley Watershed in southern California. The valley is mainly planted with mature avocado and orange trees. The surface shear stress and latent and sensible heat fluxes were measured above the trees which are up to 9 m in height. Near-neutral wind speed profile measurements allowed the determination of the watershed surface roughness (z0 = 1.4 m) and the momentum displacement height (d0 = 7.0 m). The wind speed measurements obtained under unstable atmospheric stability were analyzed using Monin-Obukhov similarity theory. New stability correction functions proposed based on theory and experiments of Kader-Yaglom as well as the now classic Businger-Dyer type functions were tested. The watershed shear stress values calculated using the surface layer wind speed profiles with the new Monin-Obukhov stability functions were found to be improved in comparison with the values obtained with the Businger-Dyer functions under strongly unstable stability conditions. The Monin-Obukhov model with the Businger-Dyer stability correction function underpredicted the momentum flux by 25% under strongly unstable stability conditions, while the new Kader-Yaglom formulation compared well on average (R2 = 0.77) with the surface eddy correlation measurements for all atmospheric stability conditions. The unstable 100-m drag coefficient was found to be u*2/V1002 = 0.0182.

  20. Modeling pollutant transport in the atmosphere boundary layer

    SciTech Connect

    O`Steen, B.L.

    1990-12-31

    The two basic methods for modeling the atmospheric transport of pollutants (diagnostic and prognostic) are examined along with the current models utilized at SRS for emergency response (WINDS). The ability of a limited-area (mesoscale) model, nested within a synoptic scale model, to represent a wide range of flow behavior, makes it the method of choice for predicting pollutant transport. Such a mesoscale model can provide an invaluable research tool and, with a periodic processing strategy for wind field calculation and/or sufficient computer capability, can be utilized in an emergency response capacity. Various models are compared.

  1. Modeling pollutant transport in the atmosphere boundary layer

    SciTech Connect

    O'Steen, B.L.

    1990-01-01

    The two basic methods for modeling the atmospheric transport of pollutants (diagnostic and prognostic) are examined along with the current models utilized at SRS for emergency response (WINDS). The ability of a limited-area (mesoscale) model, nested within a synoptic scale model, to represent a wide range of flow behavior, makes it the method of choice for predicting pollutant transport. Such a mesoscale model can provide an invaluable research tool and, with a periodic processing strategy for wind field calculation and/or sufficient computer capability, can be utilized in an emergency response capacity. Various models are compared.

  2. Backscattered UV radiation - Effects of multiple scattering and the lower boundary of the atmosphere

    NASA Technical Reports Server (NTRS)

    Aruga, T.; Heath, D. F.

    1982-01-01

    A method is proposed for the calculation of a multiple-scattering correction to the single-scattering calculation of the radiance of the terrestrial atmosphere resulting from backscattered ultraviolet solar radiation in the spectral region used in the ozone profile inversion. This method uses jointly the usual analytical and Monte Carlo methods. Effects of the lower boundary of the atmosphere, cloud tops, and ground surface are investigated both qualitatively and quantitatively. The ratio of multiple to single scattering is determined, and its importance in ozone profile inversion of backscattered UV solar radiation from the terrestrial atmosphere is evaluated. The polarization of the atmospheric radiance is treated briefly.

  3. Preliminary Validation of Atmospheric Neutral Density Derived From Ultraviolet Airglow Observations

    NASA Astrophysics Data System (ADS)

    Nicholas, A. C.; Thonnard, S. E.; Picone, J. M.; Dymond, K.; Budzien, S. A.; Knowles, S.; Bennert, E.; McCoy, R.

    2003-12-01

    In the past, orbit determination and prediction for resident space objects relied on climatological models to estimate atmospheric drag. Characteristic of climatology, atmospheric density models have errors that range from 10% to 15%. For Low Earth Orbiting (LEO) satellites, the error due to an imprecise density specification is the most significant contribution to the error ellipse associated with the position of the object. Several techniques to obtain corrections for the atmospheric density models and improve orbit determination are in various stages of research and development. This paper presents ultraviolet airglow derived atmospheric density corrections for the NRLMSISE-00 model during January and February 2001. Observations of the naturally occurring airglow on the Earth's limb were obtained from the Low-Resolution Airglow and Auroral Spectrograph (LORAAS) on the Advanced Research and Global Observation Satellite (ARGOS). Inversion algorithms developed at the Naval Research Laboratory were used to retrieve neutral density profiles from the observations. The result of the inversion process produces four correction coefficients for the NRLMSISE-00 atmospheric model; one for the F10.7 cm solar flux model input parameter, and three scalars for the O, O2 and N2 model output. The proper application of these correction coefficients with NRLMSISE-00 allows for the calculation of a global total density specification. Ultraviolet airglow derived density for January and February of 2001 were first compared to climatology using the Jacchia J70 and NRLMSISE-00 models. Additionally the ultraviolet derived density was compared to global density specification from the High Accuracy Satellite Drag Model (HASDM) developed for the Air Force Battlelab. HASDM determines global atmospheric density by simultaneously evaluating the drag on a reference set of resident space objects. From the Space Surveillance Network (SSN) observations of the HASDM reference objects, in

  4. Estimation of Atmospheric Boundary Layer Parameters for Diffusion Applications.

    NASA Astrophysics Data System (ADS)

    van Ulden, A. P.; Holtslag, A. A. M.

    1985-11-01

    This paper gives the outline of a `meteorological preprocessor' for air pollution modeling. It is shown how significantly more information can be extracted from routinely available measurements than the traditional Pasquil stability classes and power law wind speed profiles. Also it is shown how additional special measurements-if available-can be accommodated. The methods are primarily intended for application in generally level, but not necessarily homogeneous terrain. The improved characterization of the state of the planetary boundary layer allows a more modern and probably more accurate description of diffusion. The paper is an extended version of an introductory paper presented during the `Workshop on Updating Applied Diffusion Models' Clearwater, Florida, January 1984.

  5. Simulation of the Atmospheric Boundary Layer for Wind Energy Applications

    NASA Astrophysics Data System (ADS)

    Marjanovic, Nikola

    Energy production from wind is an increasingly important component of overall global power generation, and will likely continue to gain an even greater share of electricity production as world governments attempt to mitigate climate change and wind energy production costs decrease. Wind energy generation depends on wind speed, which is greatly influenced by local and synoptic environmental forcings. Synoptic forcing, such as a cold frontal passage, exists on a large spatial scale while local forcing manifests itself on a much smaller scale and could result from topographic effects or land-surface heat fluxes. Synoptic forcing, if strong enough, may suppress the effects of generally weaker local forcing. At the even smaller scale of a wind farm, upstream turbines generate wakes that decrease the wind speed and increase the atmospheric turbulence at the downwind turbines, thereby reducing power production and increasing fatigue loading that may damage turbine components, respectively. Simulation of atmospheric processes that span a considerable range of spatial and temporal scales is essential to improve wind energy forecasting, wind turbine siting, turbine maintenance scheduling, and wind turbine design. Mesoscale atmospheric models predict atmospheric conditions using observed data, for a wide range of meteorological applications across scales from thousands of kilometers to hundreds of meters. Mesoscale models include parameterizations for the major atmospheric physical processes that modulate wind speed and turbulence dynamics, such as cloud evolution and surface-atmosphere interactions. The Weather Research and Forecasting (WRF) model is used in this dissertation to investigate the effects of model parameters on wind energy forecasting. WRF is used for case study simulations at two West Coast North American wind farms, one with simple and one with complex terrain, during both synoptically and locally-driven weather events. The model's performance with different

  6. The Influence of Solar Proton Events in Solar Cycle 23 on the Neutral Middle Atmosphere

    NASA Technical Reports Server (NTRS)

    Jackman, Charles H.; vonKonig, Miriam; Anderson, John; Roble, Raymond G.; McPeters, Richard D.; Fleming, Eric L.; Russell, James M.

    2004-01-01

    Solar proton events (SPEs) can cause changes in constituents in the Earth's middle atmosphere. The highly energetic protons cause ionizations, excitations, dissociations, and dissociative ionizations of the background constituents, which lead to the production of HO(x) (H, OH, HO2) and NO(y) (N, NO, NO2, NO3, N2O5, HNO3, HO2NO2, ClONO2, BrONO2). The HO(x) increases lead to short-lived ozone decreases in the mesosphere and upper stratosphere due to the short lifetimes of the HO, constituents. The NO(x) increases lead to long-lived stratospheric ozone changes because of the long lifetime of NO(y) constituents in this region. Solar cycle 23 was quite active with SPEs and very large fluxes of high energy protons occurred in July and November 2000, November 200 1, and April 2002. Smaller, but still substantial, proton fluxes impacted the Earth during other months in the 1997-2003 time period. The impact of the very large SPEs on the neutral middle atmosphere during solar cycle 23 will be discussed, including the HO(x), NO(y), ozone variations and induced atmospheric transport changes. Two multi-dimensional models, the Goddard Space Flight Center (GSFC) Two-dimensional (2D) Model and the Thermosphere Ionosphere Mesosphere Electrodynamic General Circulation Model (TIME-GCM), were used in computing the influence of the SPEs. The results of the GSFC 2D Model and the TIME-GCM will be shown along with comparisons to the Upper Atmosphere Research Satellite (UARS) Halogen Occultation Experiment (HALOE) and Solar Backscatter Ultraviolet 2 (SBUV/2) instruments.

  7. On the predominance of unstable atmospheric conditions in the marine boundary layer offshore of the U.S. northeastern coast

    NASA Astrophysics Data System (ADS)

    Archer, Cristina L.; Colle, Brian A.; Veron, Dana L.; Veron, Fabrice; Sienkiewicz, Matthew J.

    2016-08-01

    The marine boundary layer of the northeastern U.S. is studied with focus on wind speed, atmospheric stability, and turbulent kinetic energy (TKE), the three most relevant properties in the context of offshore wind power development. Two long-term observational data sets are analyzed. The first one consists of multilevel meteorological variables measured up to 60 m during 2003-2011 at the offshore Cape Wind tower, located near the center of the Nantucket Sound. The second data set comes from the 2013-2014 IMPOWR campaign (Improving the Modeling and Prediction of Offshore Wind Resources), in which wind and wave data were collected with new instruments on the Cape Wind platform, in addition to meteorological data measured during 19 flight missions offshore of New York, Connecticut, Rhode Island, and Massachusetts. It is found that, in this region: (1) the offshore wind resource is remarkable, with monthly average wind speeds at 60 m exceeding 7 m s-1 all year round, highest winds in winter (10.1 m s-1) and lowest in summer (7.1 m s-1), and a distinct diurnal modulation, especially in summer; (2) the marine boundary layer is predominantly unstable (61% unstable vs. 21% neutral vs. 18% stable), meaning that mixing is strong, heat fluxes are positive, and the wind speed profile is often nonlogarithmic (~40% of the time); and (3) the shape of the wind speed profile (log versus nonlog) is an effective qualitative proxy for atmospheric stability, whereas TKE alone is not.

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

    SciTech Connect

    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.

  9. Dynamics of Atmospheric Boundary Layers: Large-Eddy Simulations and Reduced Analytical Models

    NASA Astrophysics Data System (ADS)

    Momen, Mostafa

    Real-world atmospheric and oceanic boundary layers (ABL) involve many inherent complexities, the understanding and modeling of which manifestly exceeds our current capabilities. Previous studies largely focused on the "textbook ABL", which is (quasi) steady and barotropic. However, it is evident that the "real-world ABL", even over flat terrain, rarely meets such simplifying assumptions. The present thesis aims to illustrate and model four complicating features of ABLs that have been overlooked thus far despite their ubiquity: 1) unsteady pressure gradients in neutral ABLs (Chapters 2 and 3), 2) interacting effects of unsteady pressure gradients and static stability in diabatic ABLs (Chapter 4), 3) time-variable buoyancy fluxes (Chapter 5) , and 4) impacts of baroclinicity in neutral and diabatic ABLs (Chapter 6). State-of-the-art large-eddy simulations will be used as a tool to explain the underlying physics and to validate analytical models we develop for these features. Chapter 2 focuses on the turbulence equilibrium: when the forcing time scale is comparable to the turbulence time scale, the turbulence is shown to be out of equilibrium, and the velocity profiles depart from the log-law; However, for longer, and surprisingly for shorter forcing times, quasi-equilibrium is maintained. In Chapter 3, a reduced analytical model, based on the Navier-Stokes equations, will be introduced and shown to be analogous to a damped oscillator where inertial, Coriolis, and friction forces mirror the mass, spring, and damper, respectively. When a steady buoyancy (stable or unstable) is superposed on the unsteady pressure gradient, the same model structure can be maintained, but the damping term, corresponding to friction forces and vertical coupling, needs to account for stability. However, for the reverse case with variable buoyancy flux and stability, the model needs to be extended to allow time-variable damper coefficient. These extensions of the analytical model are

  10. Horton, pipe hydraulics, and the atmospheric boundary layer (The Robert E. Horton Memorial Lecture)

    NASA Technical Reports Server (NTRS)

    Brutsaert, Wilfried

    1993-01-01

    The early stages of Horton's scientific career which provided the opportunity and stimulus to delve into the origins of some contemporary concepts on the atmospheric boundary layer are reviewed. The study of Saph and Schoder provided basis for the experimental verification and validation of similarity by Blasius, Staton and Pannel, and for the subsequent developments that led to the present understanding of the turbulent boundary layer. Particular attention is given to incorporation of similarity and scaling in the analysis of turbulent flow.

  11. Observations of Wind Profile of Marine Atmosphere Boundary Layer by Shipborne Coherent Doppler Lidar

    NASA Astrophysics Data System (ADS)

    Wu, Songhua; Yin, Jiaping; Liu, Bingyi; Liu, Jintao; Zhang, Hongwei; Song, Xiaoquan; Zhang, Kailin

    2016-06-01

    Pulsed Coherent Doppler Lidar (CDL) system is so good as to prove the feasibility of the marine atmosphere boundary layer detection. A ship-mounted Coherent Doppler lidar was used to measure the wind profile and vertical velocity in the boundary layer over the Yellow sea in 2014. Furthermore, for the purpose of reducing the impact of vibration during movement and correcting the LOS velocity, the paper introduces the attitude correction algorithm and comparison results.

  12. Topography Modeling in Atmospheric Flows Using the Immersed Boundary Method

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    Numerical simulation of flow over complex geometry needs accurate and efficient computational methods. Different techniques are available to handle complex geometry. The unstructured grid and multi-block body-fitted grid techniques have been widely adopted for complex geometry in engineering applications. In atmospheric applications, terrain fitted single grid techniques have found common use. Although these are very effective techniques, their implementation, coupling with the flow algorithm, and efficient parallelization of the complete method are more involved than a Cartesian grid method. The grid generation can be tedious and one needs to pay special attention in numerics to handle skewed cells for conservation purposes. Researchers have long sought for alternative methods to ease the effort involved in simulating flow over complex geometry.

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  14. Determination of the Atmospheric Boundary Layer Height from Radiosonde and Lidar Backscatter

    NASA Astrophysics Data System (ADS)

    Hennemuth, Barbara; Lammert, Andrea

    2006-07-01

    The height of the atmospheric boundary layer is derived with the help of two different measuring systems and methods. From radiosoundings the boundary layer height is determined by the parcel method and by temperature and humidity gradients. From lidar backscatter measurements a combination of the averaging variance method and the high-resolution gradient method is used to determine boundary layer heights. In this paper lidar-derived boundary layer heights on a 10 min basis are presented. Datasets from four experiments two over land and two over the sea are used to compare boundary layer heights from both methods. Only the daytime boundary layer is investigated because the height of the nighttime stable boundary layer is below the range of the lidar. In many situations the boundary layer heights from both systems coincide within ±200 m. This corresponds to the standard deviation of lidar-derived 10-min values within a 1-h interval and is due to the time and space variability of the boundary layer height. Deviations appear for certain situations and depend on which radiosonde method is applied. The parcel method fails over land surfaces in the afternoon when the boundary layer stabilizes and over the ocean when the boundary layer is slightly stable. An automatic radiosonde gradient method sometimes fails when multiple layers are present, e.g. a residual layer above the growing convective boundary layer. The lidar method has the advantage of continuous tracing and thus avoids confusion with elevated layers. On the other hand, it mostly fails in situations with boundary layer clouds

  15. Comprehensive study of disturbances of the neutral atmosphere and ionosphere parameters over Eastern Siberia during major sudden stratospheric warming

    NASA Astrophysics Data System (ADS)

    Medvedeva, Irina; Medvedev, Andrey; Ratovsky, Konstantin; Tolstikov, Maxim; Shcherbakov, Alexander

    We investigated the disturbances of the neutral atmosphere and ionosphere parameters in a large range of heights in the region of Eastern Siberia during the period of the 2013 January sudden stratospheric warming (SSW). The analysis based on the data from spectrometric measurements of the OH and O2 upper atmospheric emissions obtained at the ISTP Geophysical Observatory (52E, 103N), data from Irkutsk DPS-4 Digisonde, data from Irkutsk Incoherent Scatter Radar, and satellite data on vertical temperature distribution in the atmosphere from Aura MLS v3.3. Also, the data of NCEP / NCAR and MERRA reanalysis were involved. The 2013 January major sudden stratospheric warming (SSW) was accompanied by significant disturbances of zonal characteristics of the lower and middle atmosphere, zonal circulation reversal at the 10-hPa level at 60N, and splitting of the polar vortex. Comprehensive analysis of the neutral atmosphere and ionosphere parameters revealed the SSW manifestations in a large height range. Disturbances of the neutral atmosphere temperature from the stratosphere to the mesosphere and lower thermosphere (MLT) were detected. At the MLT heights, revealed was an increase in the intensities of the OH (~87 km) and O2 (~94 km) emissions by a factor of 2-2.5 relative to the undisturbed conditions. At the F2-layer peak height, found were disturbances of the plasma parameters: electron density, electron and ion temperatures, and decrease in the daily rate of meridional component of the neutral wind. We assume that the observed effects can be caused by atmospheric circulation disturbances and amplification of vertical transfer. The disturbances in the upper atmosphere and ionosphere parameters during SSW can be evidence of the coupling between the lower and upper atmosphere. The work was supported by Russian Foundation for Basic Research Grant 13-05-00153 and RF President Grant of Public Support for RF Leading Scientific Schools (NSh-2942.2014.5).

  16. Climatic equilibrium of the atmospheric convective boundary layer over a tropical ocean

    NASA Technical Reports Server (NTRS)

    Ridgway, W.; Betts, Alan K.

    1989-01-01

    A radiative-convective boundary layer model was developed by coupling a thermodynamic model of a partially mixed convective boundary layer (CBL) with a radiation model, and energy balance constraints were used to study coupled boundary layer (CBL) equilibrium over three timescales (about 1 day, about 10 days, and more than 100 days). It is shown that the variation in cloud top decreases with greater coupling to the atmosphere and the ocean. The slope of the latent heat flux with increasing SST decreases with more tropospheric coupling, and reverses sign with a coupled ocean.

  17. Symmetric Neutral-Atmosphere Mapping Functions: A Review of the State-Of-The-Art

    NASA Astrophysics Data System (ADS)

    Sharifi, M. A.; Souri, A. H.

    2013-12-01

    The aim of this paper is to review of six recent symmetric mapping functions. The mapping function can be largely used for GPS meteorological measurements, InSAR atmospheric corrections and precise measurements of very long baseline interferometry (VLBI). These spacebased techniques use radio signal that propagate through the Earth's atmosphere. The electrically-neutral region, predominantly the troposphere, affects the speed and direction of travel of radio waves leading to existence of excess path. The mapping function models the elevation angle dependence of the delay. Within the past decade, significant improvements have been achieved in order to use of Numerical Weather Models (NWM) for geodetic positioning. Ray-tracing algorithms have been performed through refractivity shells retrieved from NWMs in order to relate zenith delays to slant delays. Therefore, there seems to be a real need for deep review of recent developments in the mapping function domain. This paper proposes a comprehensive review of the symmetric mapping functions state of the art, their spatio-temporal variations and used NWM and generic models. Niell Mapping Function (NMF), Vienna Mapping Function (VMF1), University of New Brunswick-VMF1 (UNB-VMF1) mapping functions, Global Mapping Function (GMF) and Global Pressure and Temperature (GPT2)/GMF are reviewed in this paper.

  18. Mass identification of the neutral products generated in the plasma treatment of polluted atmospheres

    NASA Astrophysics Data System (ADS)

    Seymour, David

    2013-09-01

    Plasmas produced using Dielectric Barrier Discharge (DBD) devices are very effective in the abatement of air pollution resulting from, for example, the emission of volatile organic compounds (VCOs) by a range of industrial and agricultural processes. The development and monitoring of effective DBD systems can be investigated by advanced mass spectrometric methods specifically configured for analysis at high and atmospheric pressures The present work involves the operation of a small DBD reactor which uses either a helium or nitrogen carrier gas to sustain the plasma to which may be added reactive gases, such as oxygen, as well as samples of pollutants such as chlorinated hydrocarbons, including trichloroethylene. The mass spectrometric analysis was performed using a specially configured system manufactured by Hiden Analytical Ltd. The DBD source may also be combined with a catalyst for plasma-enhanced catalysis. The neutral products of the reactions proceeding in the plasma at atmospheric pressure are sampled through the capillary sampling system which also reduces the pressure of the gas mixture delivered to the ionisation source of the quadrupole mass spectrometer. The ions produced are subsequently mass identified. We describe typical data and comment on the advantages of this technique.

  19. Radon dispersion modeling and dose assessment for uranium mine ventilation shaft exhausts under neutral atmospheric stability.

    PubMed

    Xie, Dong; Wang, Hanqing; Kearfott, Kimberlee J; Liu, Zehua; Mo, Shunquan

    2014-03-01

    In the present study, the roles of atmospheric wind profiles in the neutral atmosphere and surface roughness parameters in a complex terrain were examined to determine their impacts on radon ((222)Rn) dispersion from an actual uranium mine ventilation shaft. Simulations were completed on (222)Rn dispersion extending from the shaft to a vulnerable distance, near the location of an occupied farmhouse. The eight dispersion scenarios for the ventilation shaft source included four downwind velocities (0.5, 1.0, 2.0 and 4.0 m s(-1)) and two underlying surface roughness characteristics (0.1 m and 1.0 m). (222)Rn distributions and elevated pollution regions were identified. Effective dose estimation methods involving a historical weighting of wind speeds in the direction of interest coupled to the complex dispersion model were proposed. Using this approach, the radiation effects on the residents assumed to be outside at the location of the farm house 250 m downwind from the ventilation shaft outlet were computed. The maximum effective dose rate calculated for the residents at the outside of the farm house was 2.2 mSv y(-1), which is less than the low limit action level of 3-10 mSv y(-1) recommended by the International Commission on Radiological Protection (ICRP) occupational exposure action level for radon.

  20. Atmospheric boundary layer investigations in the Laptev Sea area

    NASA Astrophysics Data System (ADS)

    Schwarz, Pascal; Heinemann, Günther; Drüe, Clemens; Makshtas, Alexander

    2016-04-01

    In the winter season 2014/2015 a field campaign at the Tiksi observatory (71°38'N, 128°52'E) was carried out by the University of Trier with support of the Arctic and Antarctic Research Institute (AARI) and the GEOMAR Kiel in framework of the interdisciplinary Transdrift project. One goal of the campaign is to help to improve the understanding of processes within the Arctic stable boundary layer (SBL). Within the SBL, there are several important phenomena and processes like low-level jets, surface and lifted inversions, the development of the mixing height or the determination of the energy balance, which can be best investigated with a mix of high-resolution ground-based remote sensing systems and flux tower measurements. We mainly used a SODAR/RASS, a scintillometer, a ceilometer as well as the local flux tower to investigate the SBL for the Arctic winter. Baroclinity is found to be the main driven mechanism for low-level jets with jet core heights above 200 m due to the strong temperature gradient between the Laptev Sea and the Siberian continent. Strong temperature changes at short time scale (few hours) were often closely related to a change of wind direction and therefore advection. LLJs with heights below 200 m are likely influenced by local topography. In addition, regional climate model simulations using the COSMO-CLM (COnsortium for Small-scale MOdelling - Climate Limited area Mode) driven by ERA-Interim reanalysis data have been performed. The COSMO-CLM simulations show a good agreement with ERA-Interim reanalysis data and in-situ measurements (tower, soundings).

  1. A Neutral Gas Jet in a Low Velocity Shock Front at the Boundary of the Draco Nebula

    NASA Technical Reports Server (NTRS)

    Kalberla, P. W. M.; Herbstmeier, U.; Mebold, U.

    1984-01-01

    Twenty-one cm line observations with the Westerbork Synthesis Radio Telescope of a dust and molecular filament at the boundary of the Draco Nebula reveal a jet like neutral hydrogen feature funneling through an outlet in the low velocity shock front at the interface between the Draco Nebula and the surrounding gas. The jet like feature is apparently connected with a high velocity filament at VLSR = -180 km/sec. It is suggested that soft X-ray emission observed in the area is thermal bremsstrahlung produced by the deceleration of high velocity gas in galactic gas.

  2. Stability of atmospheric CO2 levels across the Triassic/Jurassic boundary.

    PubMed

    Tanner, L H; Hubert, J F; Coffey, B P; McInerney, D P

    2001-06-07

    The Triassic/Jurassic boundary, 208 million years ago, is associated with widespread extinctions in both the marine and terrestrial biota. The cause of these extinctions has been widely attributed to the eruption of flood basalts of the Central Atlantic Magmatic Province. This volcanic event is thought to have released significant amounts of CO2 into the atmosphere, which could have led to catastrophic greenhouse warming, but the evidence for CO2-induced extinction remains equivocal. Here we present the carbon isotope compositions of pedogenic calcite from palaeosol formations, spanning a 20-Myr period across the Triassic/Jurassic boundary. Using a standard diffusion model, we interpret these isotopic data to represent a rise in atmospheric CO2 concentrations of about 250 p.p.m. across the boundary, as compared with previous estimates of a 2,000-4,000 p.p.m. increase. The relative stability of atmospheric CO2 across this boundary suggests that environmental degradation and extinctions during the Early Jurassic were not caused by volcanic outgassing of CO2. Other volcanic effects-such as the release of atmospheric aerosols or tectonically driven sea-level change-may have been responsible for this event.

  3. The Effect of Lateral Boundary Values on Atmospheric Mercury Simulations with the CMAQ Model

    EPA Science Inventory

    Simulation results from three global-scale models of atmospheric mercury have been used to define three sets of initial condition and boundary condition (IC/BC) data for regional-scale model simulations over North America using the Community Multi-scale Air Quality (CMAQ) model. ...

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

    USDA-ARS?s Scientific Manuscript database

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

  5. The Effect of Lateral Boundary Values on Atmospheric Mercury Simulations with the CMAQ Model

    EPA Science Inventory

    Simulation results from three global-scale models of atmospheric mercury have been used to define three sets of initial condition and boundary condition (IC/BC) data for regional-scale model simulations over North America using the Community Multi-scale Air Quality (CMAQ) model. ...

  6. Study of the Mechanism of Nucleation in the Polluted Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Chen, Modi

    Atmospheric aerosols can affect human health and earth's radiation balance. The formation of these aerosols has been shown to cast high uncertainty in current global climate modeling. Most observed nucleation events in the boundary layers are correlated with high sulfuric acid concentration. Nucleation rates are usually proportional to sulfuric acid concentration up to the third power. After atmospheric aerosol particles are formed, they often grow at a speed faster than can be explained by sulfuric acid condensation, suggesting that other chemical species also participate in this process. The detailed mechanisms of how these particles are formed and their subsequent growth are still unclear. This work is focused on furthering our understanding of atmospheric nucleation. My contribution is mainly on the following three topics: (1) characterizing condensation particle counters (CPCs) for accurate particle measurements down to 1 nm, the size close to the smallest stable sulfuric acid clusters; (2) developing a method of estimating time and size resolved particle growth rates and atmospheric nucleation rates based on data from both atmospheric and laboratory studies; (3) deriving of a simple semi-empirical acid-base reaction model for atmospheric nucleation in the polluted atmospheric boundary layer.

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

  9. The Structure of the Venus Neutral Atmosphere from the Radio Science Experiment VeRa on Venus Express

    NASA Astrophysics Data System (ADS)

    Tellmann, S. A.; Häusler, B.; Pätzold, M.; Bird, M. K.; Tyler, G. L.

    2007-12-01

    The Venus Express Radio Science Experiment VeRa is sounding the Venus neutral atmosphere and ionosphere using the spacecraft radio subsystem in the oneway radio link mode. An Ultrastable Oscillator (USO) provides a high quality onboard frequency reference source for the derivation of electron density profiles in the ionosphere and profiles of pressure, temperature and neutral number density of the neutral atmosphere. The measurement configuration allows an altitude resolution of only a few hundred metres from the cloud deck at about 40 km to approximately 100 km. Three occultation seasons could be covered in the first two years of the Venus Express mission resulting in a data set of about 140 profiles of the neutral atmosphere. The polar orbit of Venus Express provides the opportunity to study the atmosphere at all planetocentric latitudes under varying illumination conditions. Special attention will be given to day-night variations of the thermal structure and the temperature distribution at high polar latitudes on both hemispheres ("cold collar region") and signal absorption effects caused by the H2SO4 vapour.

  10. Empirical Observations of Scaling and Symmetry in the Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Fitton, G. F.; Mezemate, Y.; Tchiguirinskaia, I.; Schertzer, D. J. M.

    2015-12-01

    Using multiple measurement techniques from five locations, including Ecole des Ponts, we study the scaling and symmetries of measured atmospheric quantities in space and time in the atmospheric boundary-layer. Combining LIDAR, SODAR, RADAR, and sonic anemometer data, provides a means to analyse time-scales from 0.02 seconds to 15 years! and heights from 10m to 8km! Understanding and modelling the properties of the atmosphere over these immense ranges of space and time scales with a unique model is only possible through the scales. Moreover, the complex relationships between space and time-scales in the boundary- layer means symmetries differ greatly from classical turbulence theory. Small-temporal scale analysis (<15 minutes) of the velocity fluctuations shows (now) classical models for turbulence are respected over all measurement locations; classical in the sense that a Kolmogorov turbulence model with a significant intermittency correction is respected. Above these time-scales the stability of the atmosphere plays a key role. As such the time-scaling of the velocity is much more complex and classical space-time symmetries aren't respected. Using empirically estimated spectral energies and simple scaling and symmetry arguments we propose a model for the atmospheric boundary-layer that predicts only two possible profiles for the vertical transfer of energy. We discuss the space-time scaling properties of this model and the consequences thereof for the velocity fluctuations.

  11. Investigating TIME-GCM Atmospheric Tides for Different Lower Boundary Conditions

    NASA Astrophysics Data System (ADS)

    Haeusler, K.; Hagan, M. E.; Lu, G.; Forbes, J. M.; Zhang, X.; Doornbos, E.

    2013-12-01

    It has been recently established that atmospheric tides generated in the lower atmosphere significantly influence the geospace environment. In order to extend our knowledge of the various coupling mechanisms between the different atmospheric layers, we rely on model simulations. Currently there exist two versions of the Global Scale Wave Model (GSWM), i.e. GSWM02 and GSWM09, which are used as a lower boundary (ca. 30 km) condition for the Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIME-GCM) and account for the upward propagating atmospheric tides that are generated in the troposphere and lower stratosphere. In this paper we explore the various TIME-GCM upper atmospheric tidal responses for different lower boundary conditions and compare the model diagnostics with tidal results from satellite missions such as TIMED, CHAMP, and GOCE. We also quantify the differences between results associated with GSWM02 and GSWM09 forcing and results of TIMEGCM simulations using Modern-Era Retrospective Analysis for Research and Application (MERRA) data as a lower boundary condition.

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

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

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

  13. A numerical model of the atmospheric boundary layer over a marginal ice zone

    NASA Astrophysics Data System (ADS)

    Kantha, Lakshmi H.; Mellor, George L.

    1989-04-01

    A two-dimensional, multilevel model for simulating changes in the atmospheric boundary layer across a marginal ice zone is described and applied to off-ice, on-ice, and along-ice edge wind conditions. The model incorporates a second-moment closure for parameterizing the intensification and suppression of turbulent mixing in the boundary layer due to stratification effects. For off-ice winds, as the atmospheric boundary layer passes from cold smooth ice onto warm open water, the onset of intense convection raises the inversion. Over the transition zone of rough rafted ice with open leads, the shear stress on the ice cover increases significantly before dropping down to the downstream values over water. Such nonmonotonic surface stress could be the cause of divergence of sea ice near the ice edge in a marginal ice zone. These results are in agreement with the one-layer model simulations of off-ice winds by Overland et al. (1983). For on-ice wind conditions, as the warm flow in the boundary layer encounters the cold ice conditions, the resulting stable stratification could rapidly suppress the turbulence in the boundary layer, leading to the development of a shallow inversion and an associated jet. When the wind is predominantly along the ice edge, the temperature contrast between the open water and the ice could produce a thermal front at the ice edge in the boundary layer with strong associated turbulence. More observations are needed to verify these model predictions. Nevertheless, these model results suggest that it is important to account for the changes in the characteristics of the atmospheric boundary layer across the marginal ice zone in our attempts to understand the behavior of the ice cover in these regions.

  14. LABLE: A Multi-Institutional, Student-Led, Atmospheric Boundary Layer Experiment

    SciTech Connect

    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, S.; Newsom, R. K.

    2015-10-01

    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.

  15. Two Wide-Angle Imaging Neutral-Atom Spectrometers and Interstellar Boundary Explorer energetic neutral atom imaging of the 5 April 2010 substorm

    NASA Astrophysics Data System (ADS)

    McComas, D. J.; Buzulukova, N.; Connors, M. G.; Dayeh, M. A.; Goldstein, J.; Funsten, H. O.; Fuselier, S.; Schwadron, N. A.; Valek, P.

    2012-03-01

    This study is the first to combine energetic neutral atom (ENA) observations from Two Wide-Angle Imaging Neutral-Atom Spectrometers (TWINS) and Interstellar Boundary Explorer (IBEX). Here we examine the arrival of an interplanetary shock and the subsequent geomagnetically effective substorm on 5 April 2010, which was associated with the Galaxy 15 communications satellite anomaly. IBEX shows sharply enhanced ENA emissions immediately upon compression of the dayside magnetosphere at 08:26:17+/-9 s UT. The compression drove a markedly different spectral shape for the dayside emissions, with a strong enhancement at energies >1 keV, which persisted for hours after the shock arrival, consistent with the higher solar wind speed, density, and dynamic pressure (˜10 nPa) after the shock. TWINS ENA observations indicate a slower response of the ring current and precipitation of ring current ions as low-altitude emissions ˜15 min later, with the >50 keV ion precipitation leading the <10 keV precipitation by ˜20 min. These observations suggest internal magnetospheric processes are occurring after compression of the magnetosphere and before the ring current ions end up in the loss cone and precipitate into the ionosphere. We also compare MHD simulation results with both the TWINS and IBEX ENA observations; while the overall fluxes and distributions of emissions were generally similar, there were significant quantitative differences. Such differences emphasize the complexity of the magnetospheric system and importance of the global perspective for macroscopic magnetospheric studies. Finally, Appendix A documents important details of the TWINS data processing, including improved binning procedures, smoothing of images to a given level of statistical accuracy, and differential background subtraction.

  16. Interstellar Neutral Gas Flow Measurements with the Interstellar Boundary Explorer (IBEX) - Implications on Interstellar Medium and Heliosphere Diagnostics

    NASA Astrophysics Data System (ADS)

    Moebius, E.; Bochsler, P. A.; Bzowski, M.; Fuselier, S. A.; Heirtzler, D.; Hlond, M.; Kubiak, M.; Kucharek, H.; Lee, M. A.; Leonard, T.; McComas, D. J.; Saul, L. A.; Schwadron, N. A.; Sokol, J.; Wurz, P.

    2013-05-01

    The Interstellar Boundary Explorer (IBEX) observes the interstellar neutral gas flow tra-jectories at their perihelion in Earth's orbit every year from December through late March, when the Earth moves into the oncoming flow. Surprisingly, the initial quantita-tive analysis resulted in a somewhat different interstellar flow vector with noticeably lower speed than obtained previously. In comparison with astronomical observations of the flow vectors of neighboring interstellar clouds, this result locates the solar system within the Local Interstellar Cloud (LIC), contrary to the previous determination, which indicated values between the LIC and the G-Cloud. This year, the fifth season is being accumulated, providing a database over increasing solar activity and with varying view-ing strategies. These recurring observations of the interstellar flow pattern and its spatial distribution allow us to consolidate the derived physical conditions of the surrounding interstellar medium. We can also track variations in the flow at 1 AU that may arise from solar cycle related changes in ionization and radiation pressure for H and explore any other variations of the neutral gas flow. Based on the angular distributions in latitude and longitude, the neutral flow observations also indicate the presence of a secondary compo-nent for most of the species, which most probably stems from charge exchange with ions in the outer heliosheath. We will review our observations and discuss implications for the LIC and its interaction with the heliosphere in the light of a growing data set and improv-ing analysis techniques.

  17. Neutral Atmospheric Influences of the Solar Proton Events in October-November 2003

    NASA Technical Reports Server (NTRS)

    Jackman, Charles H.; DeLand, Matthew T.; Labow, Gordon J.; Fleming, Eric L.; Weisenstein, Debra K.; Ko, Malcolm K. W.; Sinnhuber, Miriam; Russell, James M.

    2005-01-01

    The large solar storms in October-November 2003 caused solar proton events (SPEs) at the Earth and impacted the middle atmospheric polar cap regions. Although occurring near the end of the maximum of solar cycle 23, the fourth largest period of SPES measured in the past 40 years happened 28-31 October 2003. The highly energetic protons associated with the SPEs produced ionizations, excitations, dissociations, and dissociative ionizations of the background constituents, which led to the production of odd hydrogen (HO(sub x)) and odd nitrogen (NO(sub y)). NO(sub x) (NO + NO2) was observed by the UARS HALOE instrument to increase over 20 ppbv throughout the Southern Hemisphere polar lower mesosphere. The NOAA 16 SBUV/2 instrument measured a short-term ozone depletion of 40% in the Southern Hemisphere polar lower mesosphere, probably a result of the HO(sub x) increases. SBUV/2 observations showed ozone depletions of 5-8% in the southern polar upper stratosphere lasting days beyond the events, most likely a result of the NO(sub y) enhancements. Longer-term Northern Hemisphere polar total ozone decreases of >0.5% were predicted to last for over 8 months past the events with the Goddard Space Flight Center two-dimensional model. Although the production of NO(sub y) constituents is the same in both hemispheres, the NO(sub y) constituents have a much larger impact in the northern than the southern polar latitudes because of the seasonal differences between the two hemispheres. These observations and model computations illustrate the substantial impact of solar protons on the polar neutral middle atmosphere.

  18. Momentum, heat, and neutral mass transport in convective atmospheric pressure plasma-liquid systems and implications for aqueous targets

    NASA Astrophysics Data System (ADS)

    Lindsay, Alexander; Anderson, Carly; Slikboer, Elmar; Shannon, Steven; Graves, David

    2015-10-01

    There is a growing interest in the study of plasma-liquid interactions with application to biomedicine, chemical disinfection, agriculture, and other fields. This work models the momentum, heat, and neutral species mass transfer between gas and aqueous phases in the context of a streamer discharge; the qualitative conclusions are generally applicable to plasma-liquid systems. The problem domain is discretized using the finite element method. The most interesting and relevant model result for application purposes is the steep gradients in reactive species at the interface. At the center of where the reactive gas stream impinges on the water surface, the aqueous concentrations of OH and ONOOH decrease by roughly 9 and 4 orders of magnitude respectively within 50 μ m of the interface. Recognizing the limited penetration of reactive plasma species into the aqueous phase is critical to discussions about the therapeutic mechanisms for direct plasma treatment of biological solutions. Other interesting results from this study include the presence of a 10 K temperature drop in the gas boundary layer adjacent to the interface that arises from convective cooling. Though the temperature magnitudes may vary among atmospheric discharge types (different amounts of plasma-gas heating), this relative difference between gas and liquid bulk temperatures is expected to be present for any system in which convection is significant. Accounting for the resulting difference between gas and liquid bulk temperatures has a significant impact on reaction kinetics; factor of two changes in terminal aqueous species concentrations like H2O2, NO2- , and NO3- are observed in this study if the effect of evaporative cooling is not included.

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

    NASA Astrophysics Data System (ADS)

    Kettle, Anthony

    2014-05-01

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

  20. Observations of the atmospheric boundary layer height over Abu Dhabi, United Arab Emirates: Investigating boundary layer climatology in arid regions

    NASA Astrophysics Data System (ADS)

    Marzooqi, Mohamed Al; Basha, Ghouse; Ouarda, Taha B. M. J.; Armstrong, Peter; Molini, Annalisa

    2014-05-01

    Strong sensible heat fluxes and deep turbulent mixing - together with marked dustiness and a low substrate water content - represent a characteristic signature in the boundary layer over hot deserts, resulting in "thicker" mixing layers and peculiar optical properties. Beside these main features however, desert ABLs present extremely complex local structures that have been scarcely addressed in the literature, and whose understanding is essential in modeling processes such as the transport of dust and pollutants, and turbulent fluxes of momentum, heat and water vapor in hyper-arid regions. In this study, we analyze a continuous record of observations of the atmospheric boundary layer (ABL) height from a single lens LiDAR ceilometer operated at Masdar Institute Field Station (24.4oN, 54.6o E, Abu Dhabi, United Arab Emirates), starting March 2013. We compare different methods for the estimation of the ABL height from Ceilometer data such as, classic variance-, gradient-, log gradient- and second derivation-methods as well as recently developed techniques such as the Bayesian Method and Wavelet covariance transform. Our goal is to select the most suited technique for describing the climatology of the ABL in desert environments. Comparison of our results with radiosonde observations collected at the nearby airport of Abu Dhabi indicate that the WCT and the Bayesian method are the most suitable tools to accurately identify the ABL height in all weather conditions. These two methods are used for the definition of diurnal and seasonal climatologies of the boundary layer conditional to different atmospheric stability classes.

  1. Sea ice edge position impact on the atmospheric boundary layer temperature structure

    NASA Astrophysics Data System (ADS)

    Khavina, Elena; Repina, Irina

    2016-04-01

    Processes happening in the Arctic region nowadays strongly influence global climate system; the polar amplification effect can be considered one of the main indicators of ongoing changes. Dramatic increase in amount of ice-free areas in the Arctic Ocean, which took place in 2000s, is one of the most significant examples of climate system dynamic in polar region. High amplitude of changes in Arctic climate, both observed and predicted, and existing inaccuracies of climate and weather forecasting models, enforce the development of a more accurate one. It is essential to understand the physics of the interaction between atmosphere and ocean in the Northern Polar area (particularly in boundary layer of the atmosphere) to improve the models. Ice conditions have a great influence on the atmospheric boundary layer in the Arctic. Sea ice inhibits the heat exchange between atmosphere and ocean water during the polar winter, while the heat exchange above the ice-free areas increases rapidly. Due to those significant temperature fluctuations, turbulence of heat fluxes grows greatly. The most intensive interaction takes place at marginal ice zones, especially in case of the cold outbreak - intrusion of cooled air mass from the ice to free water area. Still, thermal structure and dynamic of the atmosphere boundary layer are not researched and described thoroughly enough. Single radio sounding observations from the planes being done, bur they do not provide high-resolution data which is necessary for study. This research is based on continuous atmosphere boundary layer temperature and sea ice observation collected in the Arctic Ocean during the two NABOS expeditions in August and September in 2013 and 2015, as well as on ice conditions satellite data (NASA TEAM 2 and VASIA 2 data processing). Atmosphere temperature data has been obtained with Meteorological Temperature Profiler MTP-5 (ATTEX, Russia). It is a passive radiometer, which provides continuous data of atmospheric

  2. A Field-Reversed Configuration Plasma Translated into a Neutral Gas Atmosphere

    NASA Astrophysics Data System (ADS)

    Sekiguchi, Jun'ichi; Asai, Tomohiko; Takahashi, Tsutomu; Ando, Hirotoshi; Arai, Mamiko; Katayama, Seri; Takahashi, Toshiki

    2014-10-01

    A field-reversed configuration (FRC) is a compact toroid dominantly with poloidal magnetic field. Because of its simply-connected configuration, an FRC can be translated axially along a gradient of guide magnetic field, and trapped in a confinement region with quasi-static external magnetic field. FRC translation experiments have been performed several facilities. Translation speed of those translated FRCs is comparable with super-Alfvenic speed of approximately 200 km/s. In this experiments, FRC translation has been performed on the FAT (FRC Amplification via Translation) facility. Achieved translation speed in the case of translation into a confinement chamber maintained as the vacuum state is in the range from 130 to 210 km/s. On the other hand, FRC translation into a statically filled deuterium gas atmosphere has also been performed. In the case of translation into filled neutral gas, FRC translation speed is approximately 80 km/s and the separatrix volume has extremely expanded compared with the case of a vacuum state. The phenomenon suggests the presence of regeneration process of translation kinetic energy back into the internal plasma energy during the translation process. This work was partially supported by ``Nihon University Symbolic Project.'' The authors gratefully acknowledge contributions from Nac Image Technology Inc. on the fast camera measurements.

  3. Calibration of the Neutral Mass Spectrometer for the Lunar Atmosphere and Dust Environment Explorer

    NASA Technical Reports Server (NTRS)

    Mahaffy, P. R.; Hodges, R. R.; Harpold, D. N.; King, T. T.; Jaeger, F.; Raaen, E.; Lyness, E.; Collier, M.; Benna, M.

    2012-01-01

    Science objectives of the LADEE Mission are to (1) determine the composition, and time variability of the tenuous lunar atmosphere and (2) to characterize the dust environment and its variability. These studies will extend the in-situ characterization of the environment that were carried out decades ago with the Apollo missions and a variety of ground based studies. The focused LADEE measurements will enable a more complete understanding of dust and gas sources and sinks. Sources of gas include UV photo-stimulated desorption, sputtering by plasma and micrometeorites, as well as thermal release of species such as argon from the cold service or venting from the lunar interior. Sinks include recondensation on the surface and escape through a variety of mechanisms. The LADEE science payload consists of an Ultraviolet Spectrometer, a Neutral Mass Spectrometer, and a Dust Detector. The LADEE orbit will include multiple passes at or below 50 km altitude and will target repeated sampling at the sunrise terminator where exospheric density will be highest for some thermally released species. The science mission will be implemented in approximately three months to allow measurements to be made over a period of one or more lunations In addition to the science mission NASA will use this mission to demonstrate optical communication technology away from low Earth orbit.

  4. The DROPPS/MIDAS Campaign Neutral Atmosphere Measurements and the Occurrence of PMSE and NLC

    NASA Technical Reports Server (NTRS)

    Schmidlin, F. J.; Schauer, A. G.; Zukor, Dorothy J. (Technical Monitor)

    2001-01-01

    Measurements of the neutral atmosphere and their relationship to electrodynamic conditions in the mesosphere have been of interest for many years. Inflatable falling sphere measurements along with electrodynamic measurements were obtained in conjunction with the occurrence of PMSE and NLC during the DROPPS/MIDAS Campaign conducted in July 1999 from Andenes Rocket Range, Norway. The inflatable failing sphere measurements in conjunction with a PMSE event on 5-6 July and with a NLC event on 14 July are used to infer thermal advection and its influence on the clouds' maintenance. Hodograph analysis, an early tropospheric tool used by analyst and forecasters, will be used to determine the magnitude and direction of thermal advection from measured wind data. Analysis of the wind structure through the use of hodographs and some assumptions can determine thermal advection, wind shear, and possible vertical motion. Changes in the temperature structure between allied observations were subtle which may be explained by advection. Because of meteorological instabilities in the mesosphere it is possible that hodograph analysis may not fully work. It is our intention to show that such analysis has value and has a place in the mesosphere.

  5. The DROPPS/MIDAS Campaign Neutral Atmosphere Measurements and the Occurrence of PMSE and NLC

    NASA Technical Reports Server (NTRS)

    Schmidlin, F. J.; Schauer, A. G.; Zukor, Dorothy J. (Technical Monitor)

    2001-01-01

    Measurements of the neutral atmosphere and their relationship to electrodynamic conditions in the mesosphere have been of interest for many years. Inflatable falling sphere measurements along with electrodynamic measurements were obtained in conjunction with the occurrence of PMSE and NLC during the DROPPS/MIDAS Campaign conducted in July 1999 from Andenes Rocket Range, Norway. The inflatable failing sphere measurements in conjunction with a PMSE event on 5-6 July and with a NLC event on 14 July are used to infer thermal advection and its influence on the clouds' maintenance. Hodograph analysis, an early tropospheric tool used by analyst and forecasters, will be used to determine the magnitude and direction of thermal advection from measured wind data. Analysis of the wind structure through the use of hodographs and some assumptions can determine thermal advection, wind shear, and possible vertical motion. Changes in the temperature structure between allied observations were subtle which may be explained by advection. Because of meteorological instabilities in the mesosphere it is possible that hodograph analysis may not fully work. It is our intention to show that such analysis has value and has a place in the mesosphere.

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

  7. Modeling the Neutral-Atmosphere Propagation Delay in Radiometric Space Techniques

    NASA Astrophysics Data System (ADS)

    Mendes, Virgilio De Brito

    The propagation delay induced by the electrically-neutral atmosphere has been recognized as the most problematic modeling error for radiometric space geodetic techniques. A mismodeling of this propagation delay affects significantly the height component of position and constitutes therefore a matter of concern in space-geodesy applications, such as sea-level monitoring, postglacial rebound measurement, earthquake-hazard mitigation, and tectonic-plate-margin deformation studies. The neutral-atmosphere propagation delay is commonly considered as composed of two components: a ``hydrostatic'' component, due essentially to the dry gases of the atmosphere, and a ``non-hydrostatic'' component, due to water vapor. Each one can be described as the product of the delay at the zenith and a mapping function, which models the elevation angle dependence of the propagation delay. This dissertation discusses primarily the accuracy of zenith delay prediction models and mapping functions found in the scientific literature. This performance evaluation is based on a comparison against 32,467 benchmark values, obtained by ray tracing one-year's worth of radiosonde profiles from 50 stations distributed worldwide, and comprised different phases: ray-tracing accuracy assessment, model development, and model accuracy assessment. We have studied the sensitivity of the ray-tracing technique to the choice of physical models, processing strategies, and radiosonde instrumentation accuracy. We have concluded that errors in ray tracing can amount to a few centimetres, under special circumstances, but they largely average out for each station's time series of profiles. In order to optimize the performance of the models, we have established databases of the temperature-profile parameters using 50 additional sites, for a total of 100 radiosonde stations. Based on these large databases, we have developed models for lapse rate and tropopause height determination, which have improved significantly the

  8. Preliminary comparison of model and prototype wakes. [building wake effects on atmospheric boundary layer

    NASA Technical Reports Server (NTRS)

    Logan, E., Jr.; Camp, D. W.

    1978-01-01

    Velocity and turbulence profiles previously measured in the wake of a long building 3.2 m high, located in the field, transverse to the wind and in an atmospheric boundary layer several hundred meters thick are compared with wake profiles at corresponding longitudinal stations for a scale model of the building located in a large meteorological wind tunnel having a boundary layer thickness of 0.61 m to assess the accuracy of full scale wake profile predictions based on model tests. Results are presented which show that disparities in nondimensional profiles result from differences in relative depth of logarithmic layers and in surface conditions.

  9. Marine atmospheric boundary layer over some Southern Ocean fronts during the IPY BGH 2008 cruise

    NASA Astrophysics Data System (ADS)

    Messager, C.; Speich, S.; Key, E.

    2012-11-01

    A set of meteorological instruments was added to an oceanographic cruise crossing the Southern Ocean from Cape Town to 57°33' S during the summer of 2008. The Cape Cauldron, the Subtropical, Subantarctic, Polar and southern Antarctic Circumpolar current fronts were successively crossed. The recorded data permitted to derive the exchange of momentum, heat and water vapour at the ocean-atmosphere interface. A set of 38 radiosonde releases complemented the dataset. The marine atmospheric boundary layer characteristics and air-sea interaction when the ship crossed the fronts and eddies are discussed. The specific role of the atmospheric synoptic systems advection on the air-sea interaction over these regions is highlighted. Additionally, the Subantarctic front mesoscale variability induced an anticyclonic eddy considered as part of the Subantarctic front. The specific influence of this Agulhas ring on the aloft atmosphere is also presented.

  10. Atmospheric boundary layer characteristics based on the observations at the Climate Change Tower in Ny Alesund( Svalbard).

    NASA Astrophysics Data System (ADS)

    Schiavon, Mario; Mazzola, Mauro; Lupi, Angelo; Drofa, Oxana; Tampieri, Francesco; Pelliccioni, Armando; Choi, Taejin; Vitale, Vito; Viola, Angelo P.

    2017-04-01

    At high latitudes, the Atmospheric Boundary Layer ( ABL) is often characterized by extremely stable vertical stratification since the surface radiative cooling determines inversions in temperature profiles especially during the polar night over land, ice and snow surfaces. Improvements are required in the theoretical understanding of the turbulent behavior of the high-latitude ABL. The parameterizations of surface-atmosphere exchanges employed in numerical weather prediction and climate models have also to be tested in the Arctic area. Moreover, the boundary layer structure and dynamics influence the vertical distribution of aerosol. The main issue is related to the height of PBL: the question is whether some decoupling occurs between the surface layer and the atmosphere aloft when the PBL is shallow or the mechanical mixing due to the synoptic circulation provides an overall vertical homogeneity of the concentration of the aerosol irrespective of the stability conditions. In this aim, the work investigates the features of the high-latitude ABL with particular attention to its vertical structure, the relationships among the main turbulent statistics (in a similarity approach) and their variation with the ABL state. The used data refer to measurements collected since 2012 to 2016 by slow and fast response sensors deployed at the 34 m high Amundsen-Nobile Climate Change Tower (CCT) installed at Ny-Ålesund, Svalbard. Data from four conventional Young anemometers and Väisäla thermo-hygrometers at 2, 4.8, 10.3 and 33.4 m a.g.l., alternated by three lined up sonic anemometers at 3.7, 7.5 and 21 m a.g.l., are used in the analysis. The presented results highlight that the performance of the commonly adopted ABL similarity schemes (e.g. flux-gradient relationships and parameterizations for the stable ABL height) depends upon the ABL state, determined mainly by the wind speed and the shape of the profiles of second order moments (the two being related) . For neutral or

  11. Numerical Simulation of Atmospheric Boundary Layer Flow Over Battlefield-scale Complex Terrain: Surface Fluxes From Resolved and Subgrid Scales

    DTIC Science & Technology

    2015-07-06

    SECURITY CLASSIFICATION OF: The large-eddy simulation (LES) tool has been used to study the transient characteristics of turbulent mixing in atmospheric ...Approved for Public Release; Distribution Unlimited Final Report: Numerical Simulation of Atmospheric Boundary Layer Flow Over Battlefield-scale Complex...ABSTRACT Number of Papers published in peer-reviewed journals: Final Report: Numerical Simulation of Atmospheric Boundary Layer Flow Over Battlefield

  12. Investigating the diurnal and spatial variability of flows in the atmospheric boundary layer: A large eddy simulation study

    NASA Astrophysics Data System (ADS)

    Kumar, Vijayant

    Large-eddy simulation (LES) studies of the atmospheric boundary layer (ABL) have historically modeled the daytime (convective), nighttime (stable) and dawn/dusk windy (neutral) regimes separately under the assumption of a quasi-steady ABL. The real-world ABL however, continuously transitions between the different stability regimes and development of an LES capable of simulating the entire diurnal evolution of the ABL is needed. We have developed an LES tool (The JHU-LES code) with the new-generation Lagrangian dynamic models capable of dynamic adjustment of the subgrid-scale stresses thereby, making it apt for LES over entire diurnal cycles of the ABL. Preliminary LES studies demonstrate that the JHU-LES code reproduces well-known features of the quasi-steady convective and stable boundary layers, such as the well-known spectral scalings for production and inertial subranges. LES of the entire 24-hour diurnal evolution of the atmospheric boundary layer is then performed and compared successfully to field observations (HATS dataset). Important features of the diurnal ABL such as entrainment-based growth of the CBL, development of the stable boundary layer and evolution of the nocturnal low-level jet are well reproduced. The advantages of using a local Obukhov length-scale to normalize the results are highlighted. To investigate the role of surface boundary conditions and geostrophic wind forcing, LES investigations of multi-day evolution of the ABL flow are then performed with several combinations of surface boundary conditions (imposed temperature and heat flux) and geostrophic forcing (constant, time-varying, time and height varying). The variable geostrophic forcing significantly improves the agreement of LES results with surface flux observations but shows poor agreement with daytime surface fluxes and, daytime and nighttime mean profiles. The LES setup using an imposed surface temperature almost always yields better results than cases where the heat flux is

  13. Perturbations to the neutral atmosphere caused by acoustic gravity waves at thermospheric altitudes as obtained from Dynasonde data

    NASA Astrophysics Data System (ADS)

    Negrea, Catalin; Zabotin, Nikolay; Bullett, Terry

    2015-04-01

    Gravity waves are known to have a major impact on the dynamics of the thermosphere-ionosphere. A number of recent studies addressed the issue of determining the characteristics of thermospheric gravity waves and associated Travelling Ionospheric Disturbances and also their impact on the background system. However, there are currently no methods that would allow for the continuous and uninterrupted study of both the spatial and temporal characteristics of gravity wave activity over a broad range of thermospheric altitudes. We present results obtained using Dynasonde measurements of electron density and ionospheric tilts. The data covers the bottom E- and F-Layers and implicitly contains information on induced perturbations in the horizontal plane at all accessible altitudes. The methodology that we developed is largely automated, allowing for the analysis of large amounts of data. A model of the thermosphere-ionosphere coupling is implemented to infer neutral atmosphere parameters from ionospheric measurements. This is done by accounting for ion-neutral interactions, changes to chemical composition due to wave propagation and the effect of the geomagnetic field. Background neutral temperature, neutral density and neutral composition are used from a numerical model. A sample dataset from October 24th at Wallops Island, Virginia is used to illustrate our approach. The frequency, wavevector components, group velocity, phase speed and amplitude of induced thermospheric and ionospheric perturbations are obtained. These include the TID amplitude as well as the underlying gravity wave amplitude in neutral density, temperature and zonal and meridional winds.

  14. Methane fluxes on the water-atmosphere boundary in the Sea of Okhotsk

    NASA Astrophysics Data System (ADS)

    Mishukova, G. I.; Shakirov, R. B.; Obzhirov, A. I.

    2017-08-01

    High variability in methane fluxes at the water-atmosphere boundary was found for the first time for the period 1990-2016 using expeditionary data. Variability from absorption to emission with values of more than 5 kg km-2 day-1 was found in the whole sea area and over time. Increased emission in the Sea of Okhotsk is associated with distribution areas of through and composite anomalous gas-geochemical gas fields migrating from lithospheric sources. The interannual methane discharge into the atmosphere has an oscillatory seismic dependent nature.

  15. Observed Changes in Atmospheric Boundary Layer Properties at Memphis International Airport During August 1995

    NASA Technical Reports Server (NTRS)

    Zak, J. Allen; Rodgers, William G., Jr.

    1997-01-01

    As part of the NASA Terminal Area Productivity Program, Langley Research Center embarked on a series of field measurements of wake vortex characteristics and associated atmospheric boundary layer properties. One measurement period was at the Memphis International Airport in August 1995. Atmospheric temperature, humidity, winds, turbulence, radiation, and soil properties were measured from a variety of sensor systems and platforms including sodars, profilers, aircraft and towers. This research focused on: (1) changes that occurred in tower data during sunrise and sunset transitions, (2) vertical variation of temperature and cross-head winds at selected times utilizing combinations of sensors, and (3) changes measured by an OV-10 aircraft during approaches and level flights. Significant but not unusual changes are documented and discussed in terms of expected boundary layer behavior. Questions on measurement and prediction of these changes from existing and near-term capabilities are discussed in the context of a future Aircraft Vortex Spacing System.

  16. Neutrally Stratified Turbulent Ekman Boundary Layer: Universal Similarity for a Transitional Rough Surface

    NASA Astrophysics Data System (ADS)

    Afzal, Noor

    2009-08-01

    The geostrophic Ekman boundary layer for large Rossby number ( Ro) has been investigated by exploring the role played by the mesolayer (intermediate layer) lying between the traditional inner and outer layers. It is shown that the velocity and Reynolds shear stress components in the inner layer (including the overlap region) are universal relations, explicitly independent of surface roughness. This universality of predictions has been supported by observations from experiment, field and direct numerical simulation (DNS) data for fully smooth, transitionally rough and fully rough surfaces. The maxima of Reynolds shear stresses have been shown to be located in the mesolayer of the Ekman boundary layer, whose scale corresponds to the inverse square root of the friction Rossby number. The composite wall-wake universal relations for geostrophic velocity profiles have been proposed, and the two wake functions of the outer layer have been estimated by an eddy viscosity closure model. The geostrophic drag and cross-isobaric angle predictions yield universal relations, which are also supported by extensive field, laboratory and DNS data. The proposed predictions for the geostrophic drag and the cross-isobaric angle compare well with data for Rossby number Ro ≥ 105. The data show low Rossby number effects for Ro < 105 and higher-order effects due to the mesolayer compare well with the data for Ro ≥ 103.

  17. Large-eddy simulation studies of sea spray in the hurricane atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Kelly, Mark

    The growth and maintenance of hurricanes is highly dependent upon the exchange of heat and momentum between the ocean and atmosphere. Because sea spray can significantly affect this ocean-air exchange, accurate hurricane models need to account for spray effects. We incorporate sea spray into large-eddy simulations (LES) to explore its role in the atmospheric boundary layer (ABL) of hurricanes, allowing us to assess the validity of and offer improvements to the simple spray parameterizations currently used in hurricane models. We investigate thermodynamic feedback between spray and surface heat fluxes, and examine the effects of spray upon the dynamics of the hurricane boundary layer. Results of preliminary LES, which use a bulk representation of the dominant range of spray sizes and a simplified diagnostic phase change scheme, indicate an appreciable amount of spray-air heat transfer---consistent with theory---and demonstrate a form of spray-induced thermodynamic feedback. The LES model of the hurricane atmospheric boundary layer (HABL) is adapted to account for variations in spray generation due to wave-breaking, momentum transfer between air and spray in both the vertical (liquid loading and stratification) and horizontal (drag), and dissipative heating in an emulsion-like two-phase environment. These modifications are accompanied by extension of the phase change and spray generation schemes to account for different droplet sizes, and implementation of a moving three-dimensional boundary. Collective inclusion of all these pieces of modeled physics in the LES provides results which offer a better view of the limitations of current spray-flux models, and motivates a simpler and improved alternative model. The refined results of the 'full' LES-HABL model are consistent with early simulations, and underscore the significance of boundary-layer scale thermodynamic balance, spray-induced fluxes, and wind-dependent thermodynamic feedback.

  18. Temporal variation of heat and moisture flux divergence in the FIFE atmospheric boundary layer during spring

    NASA Technical Reports Server (NTRS)

    Grossman, Robert L.

    1990-01-01

    A one-day investigation of the atmospheric boundary layer (ABL) is reported in which an aircraft monitors the temporal and spatial variations of heat and moisture turbulent-flux divergences. Incoming solar radiation is similar over natural prairie land and agriculturally developed land although the heat and moisture values show significant differences over the surfaces. Other temporal variations are noted which demonstrate that ABL transport of sensible and latent heat is affected by complex variables even under simple synoptic conditions.

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

    DTIC Science & Technology

    1982-12-01

    layers. The approach will be to compare observed evolutions in the oceanic and atmospheric boundary layers with predictions from bulk modelo wherein...evaporatiJon. The slight predicted increase in salinity from 33.5 to 33.5038 pp -:, shown inFig- ure 16, is due to evaporation. An unstable ccnditi-on...P.&.,..1977: "Santa A gsociated Offshore Foe: Forecast.ng wth a Sequentiai’o itN . Thesis, Na Pcstgraduate School, Monterey, CA., 112 pp . Brower

  20. Modelling the atmospheric boundary layer for remotely sensed estimates of daily evaporation

    NASA Technical Reports Server (NTRS)

    Gurney, R. J.; Blyth, K.; Camillo, P. J.

    1984-01-01

    An energy and moisture balance model of the soil surface was used to estimate daily evaporation from wheat and barley fields in West Germany. The model was calibrated using remotely sensed surface temperature estimates. Complete atmospheric boundary layer models are difficult to use because of the number of parameters involved and a simplified model was used here. The resultant evaporation estimates were compared to eddy correlation evaporation estimates and good agreement was found.

  1. ALADINA - an unmanned research aircraft for observing vertical and horizontal distributions of ultrafine particles within the atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Altstädter, B.; Platis, A.; Wehner, B.; Scholtz, A.; Wildmann, N.; Hermann, M.; Käthner, R.; Baars, H.; Bange, J.; Lampert, A.

    2015-04-01

    boundary layer, derived from backscatter signals of a portable Raman lidar POLLYXT, allows a quick overview of the current vertical structure of atmospheric particles. Ground-based aerosol number concentrations are consistent with the results from flights in heights of a few metres. In addition, a direct comparison of ALADINA aerosol data and ground-based aerosol data, sampling the air at the same location for more than 1 h, shows comparable values within the range of ± 20 %. MASC was operated simultaneously with complementary flight patterns. It is equipped with the same meteorological instruments that offer the possibility to determine turbulent fluxes. Therefore, additional information about meteorological conditions was collected in the lowest part of the atmosphere. Vertical profiles up to 1000 m in altitude indicate a high variability with distinct layers of aerosol, especially for the small particles of a few nanometres in diameter on 1 particular day. The stratification was almost neutral and two significant aerosol layers were detected with total aerosol number concentrations up to 17 000 ± 3400 cm-3 between 180 and 220 m altitude and 14 000 ± 2800 cm-3 between 550 and 650 m. Apart from those layers, the aerosol distribution was well mixed and reached the total number concentration of less than 8000 ± 1600 cm-3. During another day, the distribution of the small particles in the lowermost ABL was related to the stratification, with continuously decreasing number concentrations from 16 000 ± 3200 cm-3 to a minimum of 4000 ± 800 cm-3 at the top of the inversion at 320 m. Above this, the total number concentration was rather constant. In the region of 500 to 600 m altitude, a significant difference of both CPCs was observed. This event occurred during the boundary layer development in the morning and represents a particle burst within the ABL.

  2. The structure of the convective atmospheric boundary layer as revealed by lidar and Doppler radars

    NASA Technical Reports Server (NTRS)

    Eilts, M. D.; Sundara-Rajan, A.; Doviak, R. J.

    1985-01-01

    Results on the structure of the convective atmospheric boundary layer based on the analyses of data from the instrumented NSSL-KTVY tower, airborne Doppler lidar, and ground-based Doppler radars are presented. The vertically averaged wind over the boundary layer was found to be insensitive to baroclinicity, supporting the hypothesis of Arya and Wyngaard (1975). The computed momentum flux profiles were affected by baroclinicity. Horizontal wind spectra from lidar, radar, and tower data compared well with each other both in shape and magnitude. A consistent peak found near 4 km in all the computed spectra might have been caused by horizontally symmetric cells with horizontal wavelength 4 times the boundary-layer height as shown in Kuettner (1971) for the case of weak wind shear.

  3. Grain boundary degradation of YBCO superconductors sintered in CO{sub 2}-containing atmospheres

    SciTech Connect

    Balachandran, U.; Merkle, K.L.; Mundy, J.N.; Gao, Y.; Zhang, C.; Xu, D.; Selvaduray, G.

    1993-11-01

    The transport critical current density (J{sub c}) of YBCO superconductors decreased with increasing CO{sub 2} partial pressure in the sintering atmosphere and ultimately reached zero, even though magnetization measurements showed that the bulk of the samples with zero J{sub c} remained superconducting. The microstructure and composition of the samples was investigated by high resolution transmission electron microscopy and secondary-ion mass spectroscopy (SIMS). Microbeam SIMS indicated carbon segregation at grain boundaries (GBs). Approximately 10% of the GBs were coated with a thin layer of a second phase, deduced to be BaCuO{sub 2} and BaCu{sub 2}O{sub 2}. Near some grain boundaries, the structure was tetragonal within several tens of nm of the boundaries. The degradation of J{sub c} is discussed in terms of the partial pressure of CO{sub 2} and the processing temperatures. Detailed examination of GB microstructures is given in this paper.

  4. Decadal change in the troposphere and atmospheric boundary layer over the South Pole

    SciTech Connect

    Neff, W.D.

    1994-12-31

    During the austral winter of 1993, the Environmental Technology Laboratory carried out a detailed field study of the atmospheric boundary layer at Amundsen-Scott South Pole Station to determine the effect of transitory synoptic disturbances on the surface-energy budget. This study used newly developed 915-megahertz radar wind-profiling technology for the first time in the Antarctic in combination with conventional boundary layer instrumentation that included a short tower, sonic anemometer, microbarograph array, and doppler sodar. Recent discussions, however, of interdecadal variability in the circumpolar circulation around Antarctica and of decadal changes in summer cloudiness at the South Pole, motivated our study of the long-term variability in boundary layer characteristics, cloudiness, and tropospheric flow behavior to provide a climatological context for our single year`s observations. 7 refs., 3 figs.

  5. Ammonia Surface-Atmosphere Exchange in the Arctic Marine Boundary Layer

    NASA Astrophysics Data System (ADS)

    Murphy, J. G.; Wentworth, G.; Tremblay, J. E.; Gagnon, J.; Côté, J. S.; Courchesne, I.

    2014-12-01

    The net flux of ammonia between the ocean and the atmosphere is poorly known on global and regional scales. Data from high-latitude research cruises suggest that deposition from the atmosphere to the surface dominates, but the magnitude and drivers of this flux are not well understood. In the polar marine boundary layer, the surface may be composed of not only open ocean, but also first-year or multi-year sea ice which may be covered with meltponds. To characterize the air-sea exchange of ammonia in the polar marine boundary layer, data were collected aboard the Canadian Coast Guard Ship Amundsen between July 10 and Aug 14, 2014 in the Eastern Canadian Arctic. The Ambient Ion Monitor Ion Chromatograph was used to make hourly measurements of the mixing ratio of gas phase ammonia, and the water-soluble constituents of fine particle matter (PM2.5). Fluorometry was used to measure dissolved ammonium concentrations in the ocean between 0 and 20 m, and in low-salinity melt ponds encountered in regions of extensive sea ice. Observations indicate that the atmosphere contains higher levels of ammonia than are calculated to be in equilibrium with surface reservoirs, implying net deposition of ammonia from the atmosphere. While ammonium levels tended to be higher in melt ponds, the lower water temperatures still mean that these are unlikely to be sources of NH3 to the atmosphere. The disequilibrium between atmospheric and surface reservoirs of ammonia imply relatively large sources to the atmosphere (possibly nearby bird colonies) or high consumption rates in surface waters.

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

    NASA Astrophysics Data System (ADS)

    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.

  7. Exploring the Effects of Atmospheric Forcings on Evaporation: Experimental Integration of the Atmospheric Boundary Layer and Shallow Subsurface.

    PubMed

    Smits, Kathleen; Eagen, Victoria; Trautz, Andrew

    2015-06-08

    Evaporation is directly influenced by the interactions between the atmosphere, land surface and soil subsurface. This work aims to experimentally study evaporation under various surface boundary conditions to improve our current understanding and characterization of this multiphase phenomenon as well as to validate numerical heat and mass transfer theories that couple Navier-Stokes flow in the atmosphere and Darcian flow in the porous media. Experimental data were collected using a unique soil tank apparatus interfaced with a small climate controlled wind tunnel. The experimental apparatus was instrumented with a suite of state of the art sensor technologies for the continuous and autonomous collection of soil moisture, soil thermal properties, soil and air temperature, relative humidity, and wind speed. This experimental apparatus can be used to generate data under well controlled boundary conditions, allowing for better control and gathering of accurate data at scales of interest not feasible in the field. Induced airflow at several distinct wind speeds over the soil surface resulted in unique behavior of heat and mass transfer during the different evaporative stages.

  8. Exploring the Effects of Atmospheric Forcings on Evaporation: Experimental Integration of the Atmospheric Boundary Layer and Shallow Subsurface

    PubMed Central

    Smits, Kathleen; Eagen, Victoria; Trautz, Andrew

    2015-01-01

    Evaporation is directly influenced by the interactions between the atmosphere, land surface and soil subsurface. This work aims to experimentally study evaporation under various surface boundary conditions to improve our current understanding and characterization of this multiphase phenomenon as well as to validate numerical heat and mass transfer theories that couple Navier-Stokes flow in the atmosphere and Darcian flow in the porous media. Experimental data were collected using a unique soil tank apparatus interfaced with a small climate controlled wind tunnel. The experimental apparatus was instrumented with a suite of state of the art sensor technologies for the continuous and autonomous collection of soil moisture, soil thermal properties, soil and air temperature, relative humidity, and wind speed. This experimental apparatus can be used to generate data under well controlled boundary conditions, allowing for better control and gathering of accurate data at scales of interest not feasible in the field. Induced airflow at several distinct wind speeds over the soil surface resulted in unique behavior of heat and mass transfer during the different evaporative stages. PMID:26131928

  9. Evolution of energetic neutral atom spectra as measured by the Interstellar Boundary Explorer during its first seven years

    NASA Astrophysics Data System (ADS)

    Dayeh, Maher A.; Heerikhuisen, Jacob; McComas, David; Schwadron, Nathan; Desai, Mihir; Zirnstein, Eric J.

    2016-07-01

    The Interstellar Boundary Explorer (IBEX) mission continues to provide remote Energetic Neutral Atom (ENA) measurements produced by charge exchange between energetic protons and interstellar neutrals at the edge of our heliosphere. Using the first seven years of IBEX-Hi ENA measurements (January 2009 through December 2015), we examine the evolution of the spectral slopes in four different energy bands, namely, ˜0.7-1.1 keV, ˜1.1-1.7 keV, ˜1.7-2.7 keV, and ˜2.7-4.3 keV, across different regions of the sky. Results show that spectral slopes at each energy band are characterized with unique distribution properties (e.g., width, shape, and mode), which vary in time at different rates and in both directions (distribution modes increase or decrease). We attempt to explain these results in context of ENA source regions, solar wind temporal variations, and changes in the heliosheath thickness and its plasma properties. These results provide insights into ENA production mechanisms, properties of their plasma progenitors, and how they relate to changes in the solar wind.

  10. Observation of Ion-neutral Collision Effect on Two-Ion-Stream Instability near Sheath-Presheath Boundary

    NASA Astrophysics Data System (ADS)

    Kim, Nam-Kyun; Song, J.; Roh, H.-J.; Jang, Y.; Ryu, S.; Kim, G.-H.

    2016-09-01

    The ion velocity normal to the sheath-presheath boundary in weakly-collisional Ar/Xe mixture plasmas was measured by using LIF measurement. This investigation would give an answer to the old debate topic in the sheath community, whether each ion enters the sheath with their own Bohm velocity, CB = (Te /Mi) 1 / 2 . In collisionless two-ion-species plasmas, Barrud and Hershkowitz concluded that the two-stream instability limits their velocities to become the common system sound speed, Cs = (n1Te /neM1 +n2Te /neM2) 1 / 2 . This instability is activated when the relative velocity becomes a critical velocity. In practices, the collisionless condition is not achievable. In this study, the ion-neutral collision effect on the instability was investigated with increasing the pressure of the Ar/Xe mixture gas in the range of 0.5 - 2 mTorr. Plasma is generated in a DC multi-dipole source in which n(Ar+) / n(Xe+) is controlled to be 1. Results show that the instability is grown at p <2 mTorr and the ion drift velocities at the sheath edge are close to Cs. At 2 mTorr, the ions reach their individual CB at the sheath edge because the instability is not grown, observing that the characteristic length of the instability is a function of the ion-neutral collisions. The details will be discussed in the conference.

  11. The effect of new interstellar medium parameters on the heliosphere and energetic neutral atoms from the interstellar boundary

    SciTech Connect

    Heerikhuisen, J.; Zirnstein, E. J.; Pogorelov, N. V.; Zank, G. P.; Funsten, H. O.

    2014-03-20

    We present new results from three-dimensional simulations of the solar wind interaction with the local interstellar medium (LISM) using recent observations by NASA's Interstellar Boundary EXplorer (IBEX) mission estimates of the velocity and temperature of the LISM. We investigate four strengths of the LISM magnetic field, from 1 to 4 μG, and adjust the LISM proton and hydrogen densities so that the distance to the termination shock (TS) in the directions of the Voyager spacecraft is just below 90 AU, and the density of hydrogen at the TS is close to 0.09 cm{sup –3} in the nose direction. The orientation of the magnetic field is chosen to point toward the center of the ribbon of enhanced energetic neutral atom (ENA) flux seen in the IBEX data. Our simulations show that the plasma and neutral properties in the outer heliosheath vary considerably as a function of the LISM magnetic field strength. We also show that the heliotail points downwind in all cases, though its structure is strongly affected by the external magnetic field. Comparison and consistency between the simulated ENA flux and the circularity of the ribbon as measured by IBEX are most consistent with a LISM magnetic field strength aligned with the center of the ribbon and a magnitude in the range 2.5-3 μG.

  12. The effect of new interstellar medium parameters on the heliosphere and energetic neutral atoms from the interstellar boundary

    SciTech Connect

    Heerikhuisen, J.; Zirnstein, E. J.; Funsten, H. O.; Pogorelov, N. V.; Zank, G. P.

    2014-03-05

    Here we present new results from three-dimensional simulations of the solar wind interaction with the local interstellar medium (LISM) using recent observations by NASA's Interstellar Boundary EXplorer (IBEX) mission estimates of the velocity and temperature of the LISM. We investigate four strengths of the LISM magnetic field, from 1 to 4 μG, and adjust the LISM proton and hydrogen densities so that the distance to the termination shock (TS) in the directions of the Voyager spacecraft is just below 90 AU, and the density of hydrogen at the TS is close to 0.09 cm-3 in the nose direction. The orientation of the magnetic field is chosen to point toward the center of the ribbon of enhanced energetic neutral atom (ENA) flux seen in the IBEX data. Our simulations show that the plasma and neutral properties in the outer heliosheath vary considerably as a function of the LISM magnetic field strength. We also show that the heliotail points downwind in all cases, though its structure is strongly affected by the external magnetic field. Lastly, comparison and consistency between the simulated ENA flux and the circularity of the ribbon as measured by IBEX are most consistent with a LISM magnetic field strength aligned with the center of the ribbon and a magnitude in the range 2.5-3 μG.

  13. The effect of new interstellar medium parameters on the heliosphere and energetic neutral atoms from the interstellar boundary

    DOE PAGES

    Heerikhuisen, J.; Zirnstein, E. J.; Funsten, H. O.; ...

    2014-03-05

    Here we present new results from three-dimensional simulations of the solar wind interaction with the local interstellar medium (LISM) using recent observations by NASA's Interstellar Boundary EXplorer (IBEX) mission estimates of the velocity and temperature of the LISM. We investigate four strengths of the LISM magnetic field, from 1 to 4 μG, and adjust the LISM proton and hydrogen densities so that the distance to the termination shock (TS) in the directions of the Voyager spacecraft is just below 90 AU, and the density of hydrogen at the TS is close to 0.09 cm-3 in the nose direction. The orientationmore » of the magnetic field is chosen to point toward the center of the ribbon of enhanced energetic neutral atom (ENA) flux seen in the IBEX data. Our simulations show that the plasma and neutral properties in the outer heliosheath vary considerably as a function of the LISM magnetic field strength. We also show that the heliotail points downwind in all cases, though its structure is strongly affected by the external magnetic field. Lastly, comparison and consistency between the simulated ENA flux and the circularity of the ribbon as measured by IBEX are most consistent with a LISM magnetic field strength aligned with the center of the ribbon and a magnitude in the range 2.5-3 μG.« less

  14. Atmospheric response in aurora experiment: Observations of E and F region neutral winds in a region of postmidnight diffuse aurora

    NASA Technical Reports Server (NTRS)

    Larsen, M. F.; Marshall, T. R.; Mikkelsen, I. S.; Emery, B. A.; Christensen, A.; Kayser, D.; Hecht, J.; Lyons, L.; Walterscheid, R.

    1995-01-01

    The goal of the Atmospheric Response in Aurora (ARIA) experiment carried out at Poker Flat, Alaska, on March 3, 1992, was to determine the response of the neutral atmosphere to the long-lived, large-scale forcing that is characteristic of the diffuse aurora in the post midnight sector. A combination of chemical release rocket wind measurements, instrumented rocket composition measurements, and ground-based optical measurements were used to characterize the response of the neutral atmosphere. The rocket measurements were made at the end of a 90-min period of strong Joule heating. We focus on the neutral wind measurements made with the rocket. The forcing was determined by running the assimilated mapping of ionospheric electrodynamics (AMIE) analysis procedure developed at the National Center for Atmospheric Research. The winds expected at the latitude and longitude of the experiment were calculated using the spectral thermospheric general circulation model developed at the Danish Meteorological Institute. Comparisons of the observations and the model suggest that the neutral winds responded strongly in two height ranges. An eastward wind perturbation of approximately 100 m/s developed between 140 and 200 km altitude with a peak near 160 km. A southwestward wind with peak magnitude of approximately 150 m/s developed near 115 km altitude. The large amplitude winds at the lower altitude are particularly surprising. They appear to be associated with the upward propagating semidiurnal tide. However, the amplitude is much larger than predicted by any of the tidal models, and the shear found just below the peak in the winds was nominally unstable with a Richardson number of approximately 0.08.

  15. Atmospheric response in aurora experiment: Observations of E and F region neutral winds in a region of postmidnight diffuse aurora

    SciTech Connect

    Larsen, M.F.; Marshall, T.R.; Mikkelsen, I.S.; Emery, B.A.; Christensen, A.; Kayser, D.; Hecht, J.; Lyons, L.; Walterscheid, R.

    1995-11-01

    The goal of the Atmospheric Response in Aurora (ARIA) experiment carried out at Poker Flat, Alaska, on March 3, 1992, was to determine the response of the neutral atmosphere to the long-lived, large-scale forcing that is characteristic of the diffuse aurora in the post midnight sector. A combination of chemical release rocket wind measurements, instrumented rocket composition measurements, and ground-based optical measurements were used to characterize the response of the neutral atmosphere. The rocket measurements were made at the end of a 90-min period of strong Joule heating. The authors focus on the neutral wind measurements made with the rocket. The forcing was determined by running the assimilated mapping of ionospheric electrodynamics (AMIE) analysis procedure developed at the National Center for Atmospheric Research. The winds expected at the latitude and longitude of the experiment were calculated using the spectral thermospheric general circulation model developed at the Danish Meteorological Institute. Comparisons of the observations and the model suggest that the neutral winds responded strongly in two height ranges. An eastward wind perturbation of approximately 100 m/s developed between 140 and 200 km altitude with a peak near 160 km. A southwestward wind with peak magnitude of approximately 150 m/s developed near 115 km altitude. The large amplitude winds at the lower altitude are particularly surprising. They appear to be associated with the upward propagating semidiurnal tide. However, the amplitude is much larger than predicted by any of the tidal models, and the shear found just below the peak in the winds was nominally unstable with a Richardson number of approximately 0.08.

  16. The Atmospheric Neutral Density Experiment (ANDE) and Modulating Retroreflector in Space (MODRAS): Combined Flight Experiments for the Space Test Program

    DTIC Science & Technology

    2003-01-01

    be tracked by the SSN who will provide accurate orbital state vectors for each sphere. The SLR site can then use these state vectors to acquire the...atmospheric composition, cross- track winds and neutral temperature; a Global Positioning Sensor (GPS); and a Thermal Monitoring System (TMS) to...of the three models discussed above is plotted. Note that the three models track each other for most of the large trends although small deviations

  17. Atmospheric response in aurora experiment: Observations of E and F region neutral winds in a region of postmidnight diffuse aurora

    SciTech Connect

    Larsen, M.F.; Marshall, T.R.; Mikkelsen, I.S.

    1995-09-01

    The goal of the Atmospheric Response in Aurora (ARIA) experiment carried out at Poker Flat, Alaska, on March 3, 1992, was to determine the response of the neutral atmosphere to the long-lived, large-scale forcing that is characteristic of the diffuse aurora in the postmidnight sector. A combination of chemical release rocket wind measurements, intrumented rocket composition measurements, and ground-based optical measurements were used to characterize the response of the neutral atmosphere. The rocket measurements were made at the end of a 90-min period of strong Joule heating. We focus on the neutral wind measurements made with the rocket. The forcing was determined by running the assimilated mapping of ionospheric electrodynamics (AMIE) analysis procedure developed at the National Center for Atmospheric Research. The winds expected at the latitude and longitude of the experiment were calculated using the spectral thermospheric general circulation model developed at the Danish Meteorological Institute. Comparisons of the observations and the model suggest that the neutral winds responded strongly in two height ranges. An eastward wind perturbation of {approximately}100 m s{sup -1} developed between 140 and 200 km altitude with a peak near 160 km. A southwestward wind with peak magnitude of {approximately}150 m s{sup -1} developed near 115 km altitude. The large amplitude winds at the lower altitude are particularly surprising. They appear to be associated with the upward propagating semidiurnal tide. However, the amplitude is much larger than predicted by any of the tidal models, and the shear found just below the peak in the winds was nomially unstable with a Richardson number of {approximately}0.08. 17 refs., 12 figs.

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

    NASA Astrophysics Data System (ADS)

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

    2017-08-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

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

  20. ISEE observations of the plasma sheet boundary, plasma sheet, and neutral sheet. I - Electric field, magnetic field, plasma, and ion composition

    NASA Technical Reports Server (NTRS)

    Cattell, C. A.; Mozer, F. S.; Hones, E. W., Jr.; Anderson, R. R.; Sharp, R. D.

    1986-01-01

    The first simultaneous study of dc and ac electric and magnetic fields, E x B velocity, plasma flows, ratio of plasma to magnetic field pressure, total energy density, energetic particles, and ion composition from the ISEE satellites and ground and interplanetary magnetic fields has been made to determine (1) the relationship of the previously observed electric fields at the plasma sheet boundary and at the neutral sheet to plasma parameters, and (2) whether the phenomena occurring during quiet and active times were consistent with the formation of a near-earth neutral line during substorms or with the boundary layer model. Five observations made during the study of two substorms were seen to be in agreement with the neutral-line model. The observations are consistent with the satellite being located at varying distances from the neutral line and diffusion region where reconnection and plasma acceleration were occurring. Although the z component (into or out of the ecliptic plane) of E x B convection was generally toward the neutral sheet, there were examples when it was consistent with the inferred motion of the plasma sheet past the satellite. A synthesis of previous reports on large electric fields at the plasma sheet boundary and variable fields at the neutral sheet including the associated plasma flows is also described.

  1. Boundary-layer flow and power output in large wind farms during transition from neutral to stable conditions

    NASA Astrophysics Data System (ADS)

    Allaerts, Dries; Meyers, Johan

    2016-11-01

    In wind farms, power deficits are directly related to ambient turbulence levels. Power deficits will therefore increase during the transition from a daytime, conventionally neutral boundary layer (CNBL) to the stable boundary layer (SBL) at night. Besides turbulent decay, a multitude of effects occurs during this transition. For instance, low-level jets may cause strong winds at high elevations, while the velocity near the surface generally decreases. Consequently, Coriolis forces induce a change in wind direction, which alters the apparent wind-farm layout in streamwise direction. In this study, we perform LES of a large onshore wind farm in the late-afternoon transition from an equilibrium CNBL to a surface-cooled SBL. The results of two different cooling rates are compared with the wind-farm performance in the CNBL. The power output decrease during the transition, with faster decrease for stronger surface cooling. However, the initial decrease is dominated by the reduction in wind speed, and the relative power deficits do not increase. Further, considerable wake deflection occurs, and a spatially heterogeneous distribution of temperature and heat flux is observed. The authors acknowledge support from the European Research Council (FP7-Ideas, Grant No. 306471).

  2. The Structure of the Venus Neutral Atmosphere from the Radio Science Experiment VeRa on Venus Express

    NASA Astrophysics Data System (ADS)

    Tellmann, S.; Häusler, B.; Pätzold, M.; Bird, M.; Tyler, G. L.

    2008-09-01

    The Venus Express Radio Science Experiment VeRa uses one-way radio signals at X-band (8.4 GHz) and S-band (2.3 GHz) for the sounding of the Venus neutral atmosphere and ionosphere. Three occultation seasons could be covered during the nominal mission of Venus Express resulting in a data set of about 118 profiles of the neutral atmosphere. Another three occultation seasons are planned during the extended mission. The polar orbit of Venus Express provides the opportunity to study the atmosphere at a large range of planetocentric latitudes under varying illumination conditions. Radial profiles of neutral number density derived from the occultations cover the altitude range 40-90 km, which are converted to vertical profiles of temperature and pressure. Profiles of static stability are found to be latitude-dependent and nearly adiabatic in the middle cloud region. Below the clouds the stability decreases at high latitudes. A large equator-to-pole temperature contrast of approximately 30 K is found at the 1-bar level. A distinct cold collar region could be observed on both hemispheres. At the latitudes of the cold collars, the tropopause altitude increases relative to higher and lower latitudes, while the temperature drops roughly 60 K. The observations indicate the existence of a wave number 2 structure polewards of ±75° latitude at altitudes of about 60 km.

  3. Identification of atmospheric boundary layer thickness using doppler radar datas and WRF - ARW model in Merauke

    NASA Astrophysics Data System (ADS)

    Putri, R. J. A.; Setyawan, T.

    2017-01-01

    In the synoptic scale, one of the important meteorological parameter is the atmospheric boundary layer. Aside from being a supporter of the parameters in weather and climate models, knowing the thickness of the layer of the atmosphere can help identify aerosols and the strength of the vertical mixing of pollutants in it. The vertical wind profile data from C-band Doppler radar Mopah-Merauke which is operated by BMKG through Mopah-Merauke Meteorological Station can be used to identify the peak of Atmospheric Boundaryu Layer (ABL). ABL peak marked by increasing wind shear over the layer blending. Samples in January 2015 as a representative in the wet and in July 2015 as the representation of a dry month, shows that ABL heights using WRF models show that in July (sunny weather) ABL height values higher than in January (cloudy)

  4. Model simulations of the Arctic atmospheric boundary-layer from the SHEBA year.

    PubMed

    Tjernström, Michael; Zagar, Mark; Svensson, Gunilla

    2004-06-01

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

  5. The Impact of Vegetation on the Atmospheric Boundary Layer and Convective Storms

    NASA Astrophysics Data System (ADS)

    Lee, Tsengdar John

    The impact of vegetation on atmospheric boundary layer and convective storms is examined through the construction and testing of a soil-vegetation-atmosphere transfer (SVAT) model. The Land Ecosystem-Atmosphere (LEAF) model is developed using an elevated canopy structure, an above -canopy aerodynamic resistance, two in-canopy aerodynamic resistances, and one stomatal conductance functions. The air temperature and humidity are assumed to be constant in the canopy whereas the wind and radiation follow a specified vertical profile. A simple dump-bucket method is used to parameterize the interception of precipitation and a multi-layer soil model is utilized to handle the vertical transfer of soil water. Evaporation from soil and wet leaves and transpiration from dry leaves are evaluated separately. The solid water uptake is based on soil water potential rather than on the length of roots. Separate energy budgets for vegetation and for the soil are used in order to remove unnecessary assumptions on energy partition between the vegetation and the substrate. Primary parameters are LAI, maximum stomatal conductance, and albedo. Secondary parameters include displacement height and environmental controls on stomatal resistance function. Due to the complexity of the LEAF model, statistical methods are used to improve LEAF model performance. The Multi-response Randomized Bock Permutation (MRBP) procedure is used to guide the choice of model parameter values. The Fourier Amplitude Sensitivity Test (FAST) is applied to better understand the model behavior in response to the changes in model parameters. Finally, LEAF is used to study the growth of boundary layer and the local thermal circulations generated by surface inhomogeneities. Results show the atmospheric boundary layer is substantially cooler and more moist over unstressed vegetation than over bare dry soil. Thermally forced circulation can result from the juxtaposition of two vegetation types due to different biophysical

  6. Study of the evening transition to the nocturnal atmospheric boundary layer: statistical analysis and case studies

    NASA Astrophysics Data System (ADS)

    Sastre, Mariano; Viana, Samuel; Maqueda, Gregorio; Yagüe, Carlos

    2010-05-01

    Turbulence is probably the most important feature dealing with the diffusion of contaminants in the planetary boundary layer. The main characteristics of turbulence are governed, apart from synoptic conditions, by the daily cycle of the Earth surface heating and cooling, so that, simplifying, two configurations are often found: convective and stable. The transition from a diurnal convective boundary layer to a typically stable nocturnal one is not still well understood (Edwards, 2009). Different micrometeorological conditions at sunset or a few hours previously may be critical for the establishment of a strong surface-based stability or a weak one, even for similar synoptic conditions. This work focuses on the characterization of the evening transition which takes place at the atmospheric boundary layer, considering the temporal interval 17.00-23.00 GMT. The methodology includes looking for some relations between meteorological variables, turbulent parameters and particulate matter (PM10, PM2.5 and PM1) concentrations measured by a GRIMM particle monitor (MODEL 365). Observational data (Summer 2009) is provided from permanent instrumentation at the Research Centre for the Lower Atmosphere (CIBA) in Valladolid (Spain), which is on a quite flat terrain (Cuxart et al., 2000). A 10m height mast equipped with temperature, wind speed and direction, and moisture sensors at several levels are available. Also two sonic anemometers (20 Hz sampling rate) at 1.5 and 10m were deployed in the mast. The database is complemented by a triangle of microbarometers installed next to the surface, and another three microbarometers placed in a 100m meteorological tower at 20, 50 and 100m respectively, which are ideal to study coherent structures present in the boundary layer. Statistical parameters of meteorological variables have been calculated and studied in order to find out connections with the most relevant physical processes. Moreover different cases studies will be analyzed

  7. Atmospheric boundary layer characteristics and land-atmosphere energy transfer in the Third Pole area

    NASA Astrophysics Data System (ADS)

    Ma, Y.; Zhu, Z.; Amatya, P. M.; Chen, X.; Hu, Z.; Zhang, L.; Li, M.; Ma, W.

    2015-05-01

    The Tibetan Plateau and nearby surrounding area (the Third Pole area) dramatically impacts the world's environment and especially controls climatic and environmental changes in China, Asia and even in the Northern Hemisphere. Supported by the Chinese Academy of Sciences (CAS) and some international organizations, the Third Pole Environment (TPE) Programme is now under way. First, the background of the establishment of the TPE, the establishment and monitoring plans on long-term for the TPE and six comprehensive observation and study stations are introduced. Then the preliminary observational analysis results on atmosphere-land interaction are presented. The study on the regional distribution of land surface heat fluxes is of paramount importance over the heterogeneous landscape of the Third Pole area. A parameterization methodology based on satellite and in situ data is described and tested for deriving the regional surface heat fluxes (net radiation flux, soil heat flux, sensible heat flux and latent heat flux) over the heterogeneous landscape. As a case study, the methodology was applied to the whole Tibetan Plateau area. Eight images of MODIS data and four images of AVHRR data were used for the comparison among winter, spring, summer and autumn, and the annual variation analyses. The derived results were also validated by using the ``ground truth'' measured in the stations of the TPE. The results show that the derived surface heat fluxes in the four different seasons over the Tibetan Plateau area are in good agreement with the ground measurements. The results from AVHRR were also in agreement with MODIS. It is therefore concluded that the proposed methodology is successful for the retrieval of surface heat fluxes using the MODIS data, AVHRR data and in situ data over the Tibetan Plateau area.

  8. Application of large eddy simulations for the parameterization of stable atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Jin, Emilia; Na, Ji Sung; Lee, Joon Sang; Kim, Young-Joon

    2013-04-01

    Authors investigated the parameter space of the stable atmospheric boundary layer by varying geostrophic winds, surface cooling rates and special/temporal resolutions using the large eddy simulations. The NCAR LES model based on a mixed pseudo-spectral finite difference method with third-order Runge-Kutta time stepping utilizing a staggered vertical grid and Smagorinsky subgrid-scale eddy viscosity model and PArallelized Les Model (PALM) based on a central finite differences method with a Cartesian staggered grid and turbulent kinetic energy (TKE) model were used and compared. The basic structure of the potential temperature, winds, stochastic turbulent profile and TKE budget were analyzed and the vortical structure with horizontal layering in the stable atmospheric boundary layer was investigated. Based on these results, authors validated the state-of-the-art k-profile planetary boundary layer parameterization schemes of the global numerical weather prediction models. Han and Pan (2011), Lock et al. (2000) and YSU (Hong 2010) schemes are evaluated.

  9. LOTOS: A Proposed Lower Tropospheric Observing System from the Land Surface through the Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Cohn, S. A.; Lee, W. C.; Carbone, R. E.; Oncley, S.; Brown, W. O. J.; Spuler, S.; Horst, T. W.

    2015-12-01

    Advances in sensor capabilities, but also in electronics, optics, RF communication, and off-the-grid power are enabling new measurement paradigms. NCAR's Earth Observing Laboratory (EOL) is considering new sensors, new deployment modes, and integrated observing strategies to address challenges in understanding within the atmospheric boundary layer and the underlying coupling to the land surface. Our vision is of a network of deployable observing sites, each with a suite of complementary instruments that measure surface-atmosphere exchange, and the state and evolution of the boundary layer. EOL has made good progress on distributed surface energy balance and flux stations, and on boundary layer remote sensing of wind and water vapor, all suitable for deployments of combined instruments and as network of such sites. We will present the status of the CentNet surface network development, the 449-MHz modular wind profiler, and a water vapor and temperature profiling differential absorption lidar (DIAL) under development. We will further present a concept for a test bed to better understand the value of these and other possible instruments in forming an instrument suite flexible for multiple research purposes.

  10. Modification of the Atmospheric Boundary Layer by a Small Island: Observations from Nauru

    SciTech Connect

    Matthews, Stuart; Hacker, Jorg M.; Cole, Jason N.; Hare, Jeffrey; Long, Charles N.; Reynolds, R. M.

    2007-03-01

    Nauru, a small island in the tropical pacific, generates plumes of clouds that may grow to several hundred km length. This study uses observations to examine the mesoscale disturbance of the marine atmospheric boundary layer by the island that produces these cloud streets. Observations of the surface layer were made from two ships in the vicinity of Nauru and from instruments on the island. The structure of the atmospheric boundary layer over the island was investigated using aircraft flights. Cloud production over Nauru was examined using remote sensing instruments. During the day the island surface layer was warmer than the marine surface layer and wind speed was lower than over the ocean. Surface heating forced the growth of a thermal internal boundary layer, above which a street of cumulus clouds formed. The production of clouds resulted in reduced downwelling shortwave irradiance at the island surface. A plume of warm-dry air was observed over the island which extended 15 – 20 km downwind.

  11. The influence of a very large wind farm on turbulent transport in the atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Abkar, M.; Porté-Agel, F.

    2012-04-01

    Predicting wind and turbulent transport of heat, water vapor and pollutants through wind farms is of great importance for wind engineering, wind energy and environmental applications. It requires detailed knowledge of atmospheric boundary-layer (ABL) over a wide range of spatial and temporal scales. The complexity of such flows makes it difficult to obtain all the needed information through field experiments alone, and often necessitates high-resolution eddy-resolving numerical tools such as large-eddy simulation (LES). In this study, Large-eddy simulation is used to simulate atmospheric boundary-layer flow through a very large wind farm. To do this, tuning-free Lagrangian scale-dependent dynamic models (Stoll and Porte-Agel 2006) are used to model the subgrid-scale fluxes and the turbine-induced forces are parameterized using the actuator disk model (Wu and Porte-Agel 2011). The effect of large arrays of wind turbines on local/regional fluxes of momentum and scalar quantities under different stability conditions is assessed. Also, it will be shown how wind farms can change the vertical distribution of momentum and scalar fluxes inside the ABL. Particular attention is placed on the growth of the boundary layer height due to the presence of the wind turbines.

  12. Instability of wind turbine wakes immersed in the atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Viola, Francesco; Valerio Iungo, Giacomo; Camarri, Simone; Porté-Agel, Fernando; Gallaire, François

    2015-06-01

    In this work a technique capable to investigate the near-wake stability properties of a wind turbine immersed in the atmospheric boundary layer is presented. Specifically, a 2D local spatial stability analysis is developed in order to take into account typical flow features of real operating wind turbines, such as the presence of the atmospheric boundary layer and the turbulence heterogeneity of the oncoming wind. This stability analysis can be generally applied on either experimental measurements or numerical data. In this paper it was carried out on wind tunnel experiments, for which a downscaled wind turbine is immersed in a turbulent boundary layer. Through spatial stability analysis, the dominant mode in the near wake, i.e. the most amplified one, is characterized and its frequency matches the hub-vortex instability frequency measured in the wind tunnel. As in the case of [10], where an axisymmetric wake condition was investigated, the hub-vortex instability results in a single-helical mode.

  13. Study of Transitions in the Atmospheric Boundary Layer Using Explicit Algebraic Turbulence Models

    NASA Astrophysics Data System (ADS)

    Lazeroms, W. M. J.; Svensson, G.; Bazile, E.; Brethouwer, G.; Wallin, S.; Johansson, A. V.

    2016-10-01

    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.

  14. High Altitude Neutral Particle Transport Using the Monte Carlo Simulation Code MCNP with Variable Density Atmosphere

    DTIC Science & Technology

    1991-03-01

    Monti Captain# USAF AFIT.’GNE/F•P/91M-6 (LO IA Approved for public release; distribution unlimited AFIT/IGNE/ENP/91M-6 HIGH ALTITUDE NEUTRAL... distribution unlimited Preface The purpose of this study was to perform Monte Carlo simulations of neutral particle transport with primary and secondary...21 4. Spatial Cell Geometry for Co-Altitude Detectors .................... .................. 44 5. MCNP vs. SMAUG Neutron Fluence at Source Co

  15. Radiation and atmospheric circulation controls on carbonyl sulfide concentrations in the marine boundary layer

    NASA Astrophysics Data System (ADS)

    Berkelhammer, M.; Steen-Larsen, H. C.; Cosgrove, A.; Peters, A. J.; Johnson, R.; Hayden, M.; Montzka, S. A.

    2016-11-01

    A potential closure of the global carbonyl sulfide (COS or OCS) budget has recently been attained through a combination of remote sensing, modeling, and extended surface measurements. However, significant uncertainties in the spatial and temporal dynamics of the marine flux still persist. In order to isolate the terrestrial photosynthetic component of the global atmospheric OCS budget, tighter constraints on the marine flux are needed. We present 6 months of nearly continuous in situ OCS concentrations from the North Atlantic during the fall and winter of 2014-2015 using a combination of research vessel and fixed tower measurements. The data are characterized by synoptic-scale ˜100 pmol mol-1 variations in marine boundary layer air during transitions from subtropical to midlatitude source regions. The synoptic OCS variability is shown here to be a linear function of the radiation history along an air parcel's trajectory with no apparent sensitivity to the chlorophyll concentration of the surface waters that the air mass interacted with. This latter observation contradicts expectations and suggests a simple radiation limitation for the combined direct and indirect marine OCS emissions. Because the concentration of OCS in the marine boundary layer is so strongly influenced by an air parcel's history, marine and atmospheric concentrations would rarely be near equilibrium and thus even if marine production rates are held constant at a given location, the ocean-atmosphere flux would be sensitive to changes in atmospheric circulation alone. We hypothesize that changes in atmospheric circulation including latitudinal shifts in the storm tracks could affect the marine flux through this effect.

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

    NASA Astrophysics Data System (ADS)

    Roberts, Tjarda; Hole, Lars; Voss, Paul

    2017-04-01

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

  17. Study of the diurnal variability of atmospheric chemistry with respect to boundary layer dynamics during DOMINO

    NASA Astrophysics Data System (ADS)

    van Stratum, B. J. H.; Vilà-Guerau de Arellano, J.; Ouwersloot, H. G.; van den Dries, K.; van Laar, T. W.; Martinez, M.; Lelieveld, J.; Diesch, J.-M.; Drewnick, F.; Fischer, H.; Hosaynali Beygi, Z.; Harder, H.; Regelin, E.; Sinha, V.; Adame, J. A.; Sörgel, M.; Sander, R.; Bozem, H.; Song, W.; Williams, J.; Yassaa, N.

    2012-03-01

    We study the interactions between atmospheric boundary layer (ABL) dynamics and atmospheric chemistry using a mixed-layer model (MXLCH) coupled to chemical reaction schemes. Guided by both atmospheric and chemical measurements obtained during the DOMINO campaign (2008), numerical experiments are performed to study the role of ABL dynamics and the accuracy of chemical schemes with different complexity: MOZART-4 and a reduced mechanism of this chemical system. Both schemes produce satisfactory results, indicating that the reduced scheme is capable of reproducing the O3-NOx-VOC-HOx diurnal cycle during conditions characterised by a low NOx regime and small O3 tendencies (less than 1 ppb per hour). By focussing on the budget equations of chemical species in the mixed-layer model, we show that for species like O3, NO and NO2, the influence of entrainment and boundary layer growth is of the same order as chemical production/loss. This indicates that an accurate representation of ABL processes is crucial in understanding the daily cycle of chemical species. By comparing the time scales of chemical reactive species with the mixing time scale of turbulence, we propose a classification based on the Damköhler number to further determine the importance of dynamics on chemistry during field campaigns. Our findings advocate an integrated approach, simultaneously solving the ABL dynamics and chemical reactions, in order to obtain a better understanding of chemical pathways and processes and the interpretation of the results obtained during measurement campaigns.

  18. [Measurement of atmospheric boundary layer pollutants by mobile lidar in Beijing].

    PubMed

    Wang, Shao-Lin; Xie, Pin-Hua; Hu, Shun-Xing; Wei, He-Li; Hu, Huan-Ling; Xie, Jun; Cao, Kai-Fa; Fang, Xin

    2008-03-01

    The parameters of AML-2 mobile lidar were introduced, which was based on differential absorption principle and designed by our institute. In Yufa of Beijing, the pollutants including O3, NO2, SO2 in atmospheric boundary layer were monitored in August and September of 2006 under different weather conditions. Vertical profile and diurnal variation of concentrations of these pollutants were analyzed. If without the influence of pollution air transport from south region, the concentrations of these pollutants are low under the overcast weather condition. The concentrations of O3 and NO2 decrease with altitude, and this characteristic is not obvious for SO2, but there is a high concentration layer of SO2 near ground (about 0.6km). The quality of atmosphere Beijing is influenced significantly by air transportation from south region, and the altitude of the severe pollution air transport is about 1km to 1.5km in August 23rd to 25th. As a result, the characteristics of vertical profile and daily variation of the pollutants are changed, and the concentrations of O3, NO2, SO2 in atmospheric boundary layer of Yufa area increased obviously.

  19. Preliminary analysis of the Nocturnal Atmospheric Boundary Layer during the experimental campaign CIBA 2008

    NASA Astrophysics Data System (ADS)

    Yagüe, C.; Maqueda, G.; Ramos, D.; Sastre, M.; Viana, S.; Serrano, E.; Morales, G.; Ayarzagüena, B.; Viñas, C.; Sánchez, E.

    2009-04-01

    An Atmospheric Boundary Layer campaign was developed in Spain along June 2008 at the CIBA (Research Centre for the Lower Atmosphere) site which is placed on a fairly homogeneous terrain in the centre of an extensive plateau (41°49' N, 4°56' W). Different instrumentation at several levels was available on a new 10m meteorological mast, including temperature and humidity sensors, wind vanes and cup anemometers, as well as one sonic anemometer. Besides, two quartz-based microbarometers were installed at 50 and 100m on the main permanent 100m tower placed at CIBA. Three additional microbarometers were deployed on the surface on a triangular array of approximately 200 m side, and a tethered balloon was used in order to record vertical profiles of temperature, wind and humidity up to 1000m. Finally, a GRIMM particle monitor (MODEL 365), which can be used to continuously measure each six seconds simultaneously the PM10, PM2.5 and PM1 values, was deployed at 1.5m. This work will show some preliminary results from the campaign CIBA 2008, analysing the main physical processes present in the atmospheric Nocturnal Boundary Layer (NBL), the different stability periods observed and the corresponding turbulent parameters, as well as the coherent structures detected. The pressure perturbations measured from the surface and tower levels make possible to study the main wave parameters from wavelet transform, and compared the structures detected by the microbarometers with those detected in the wind and particles records.

  20. Charting the Interstellar Magnetic Field causing the Interstellar Boundary Explorer (IBEX) Ribbon of Energetic Neutral Atoms

    NASA Astrophysics Data System (ADS)

    Frisch, P. C.; Berdyugin, A.; Piirola, V.; Magalhaes, A. M.; Seriacopi, D. B.; Wiktorowicz, S. J.; Andersson, B.-G.; Funsten, H. O.; McComas, D. J.; Schwadron, N. A.; Slavin, J. D.; Hanson, A. J.; Fu, C.-W.

    2015-12-01

    .8}-27.6+23.5 between {B}{POL} and the bulk LSR velocity the local interstellar material indicates a geometry that is consistent with an expanding superbubble. The efficiency of grain alignment in the local interstellar medium has been assessed using stars where both polarization data and hydrogen column density data are available. Nearby stars appear to have larger polarizations than expected based on reddened sightlines, which is consistent with previous results, but uncertainties are large. Optical polarization and color excess E(B - V) data indicate the presence of nearby interstellar dust in the BICEP2 field. Color excess E(B - V) indicates an optical extinction of AV > 0.6 in the BICEP2 field, while the polarization data indicate that AV > 0.09 mag. The IBEX Ribbon ISMF extends to the boundaries of the BICEP2 region.

  1. Atmospheric boundary layer response to sea surface temperatures during the SEMAPHORE experiment

    NASA Astrophysics Data System (ADS)

    Giordani, Hervé; Planton, Serge; Benech, Bruno; Kwon, Byung-Hyuk

    1998-10-01

    The sensitivity of the marine atmospheric boundary layer (MABL) subjected to sea surface temperatures (SST) during the Structure des Echanges Mer-Atmosphere, Proprietes des Heterogeneites Oceaniques: Recherche Experimentale (SEMAPHORE) experiment in 1993 has been studied. Atmospheric analyses produced by the Action de Recherche, Petite Echelle, Grande Echelle (ARPEGE) operational model at the French meteorological weather service assimilated data sets collected between October 7 and November 17, 1993, merged with the Global Telecommunication System (GTS) data. Analyses were validated against independent data from aircraft instruments collected along a section crossing the Azores oceanic front, not assimilated into the model. The responses of the mean MABL in the aircraft cross section to changes in SST gradients of about 1°C/100 km were the presence of an atmospheric front with horizontal gradients of 1°C/100 km and an increase of the wind intensity from the cold to the warm side during an anticyclonic synoptic situation. The study of the spatiotemporal characteristics of the MABL shows that during 3 days of an anticyclonic synoptic situation the SST is remarkably stationary because it is principally controlled by the Azores ocean current, which has a timescale of about 10 days. However, the temperature and the wind in the MABL are influenced by the prevailing atmospheric conditions. The ocean does not appear to react to the surface atmospheric forcing on the timescale of 3 days, whereas the atmospheric structures are modified by local and synoptic-scale advection. The MABL response appears to be much quicker than that of the SSTs. The correlation between the wind and the thermal structure in the MABL is dominated by the ageostrophic and not by the geostrophic component. In particular, the enhancement of the wind on either side of the SST front is mainly due to the ageostrophic component. Although the surface heat fluxes are not the only cause of ageostrophy, the

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

    NASA Astrophysics Data System (ADS)

    Kiliyanpilakkil, Velayudhan Praju

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

  3. A boundary layer approach to the analysis of atmospheric motion over a surface obstruction

    NASA Technical Reports Server (NTRS)

    Frost, W.; Maus, J. R.; Simpson, W. R.

    1973-01-01

    A boundary layer approach for the solution of the flow field induced over a two-dimensional surface obstruction, such as a building or other man-made structure, is proposed. Adopting a specific geometry in the form of a semi-elliptical cylinder, the characteristics of atmospheric shear flow over a rough terrain are coupled with the well-known boundary layer equations. Two approaches are presented to incorporate the pressure field and boundary conditions which exist within the large viscous region over the obstruction. The first considers a region in the immediate vicinity of the body in which the pressure distribution and outer boundary condition on the velocity are computed from potential theory for flow over the elliptical cylinder. The second approach considers a much larger region of influence, extending from the surface to the undisturbed flow at large heights above the obstruction. Methods which appear to provide an improved theoretical model of the flow over the ellipse, such as a technique for simulating the effect of the seperation regions upstream and downstream of the body, are also presented.

  4. Stable Atmospheric Boundary-Layer Experiment in Spain (SABLES 98): A Report

    NASA Astrophysics Data System (ADS)

    Cuxart, J.; Yague, C.; Morales, G.; Terradellas, E.; Orbe, J.; Calvo, J.; Fernandez, A.; Soler, M.R.; Infante, C.; Buenestado, P.; Espinalt, A.; Joergensen, H.E.; Rees, J.M.; Vila, J.; Redondo, J.M.; Cantalapiedra, I.R.; Conangla, L.

    This paper describes the Stable AtmosphericBoundary Layer Experiment in Spain (SABLES 98),which took place over the northern Spanish plateaucomprising relatively flat grassland,in September 1998. The main objectives of the campaign were to study the properties of themid-latitude stable boundary layer (SBL).Instrumentation deployed on two meteorologicalmasts (of heights 10 m and 100 m)included five sonic anemometers, 15 thermocouples,five cup anemometers and three propeller anemometers,humidity sensors and radiometers.A Sensitron mini-sodar and a tetheredballoon were also operated continuously. Atriangular array of cup anemometers wasinstalled to allow the detection ofwave events. Two nocturnal periods analysedon 14-15 and 20-21 September are used toillustrate the wide-ranging characteristics of the SBL.

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

    PubMed Central

    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

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

    PubMed

    Davy, Richard; Esau, Igor

    2016-05-25

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

  7. Statistical-mechanical approach to study the hydrodynamic stability of the stably stratified atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Nevo, G.; Vercauteren, N.; Kaiser, A.; Dubrulle, B.; Faranda, D.

    2017-08-01

    We study the hydrodynamic equilibrium properties of the stably stratified atmospheric boundary layer from measurements obtained in the Snow-Horizontal Array Turbulence Study campaign at the Plaine Morte Glacier in the Swiss Alps. Our approach is based on a combination of dynamical systems techniques and statistical analysis. The main idea is to measure the deviations from the behavior expected by a turbulent observable when it is close to a transition between different metastable states. We first assess the performance of our method on the Lorenz attractor, then on a turbulent flow. The results show that the method recognizes subtle differences among different stable boundary layer turbulence regimes and may be used to help characterize their transitions.

  8. Representation of the Saharan atmospheric boundary layer in the Weather and Research Forecast (WRF) model: A sensitivity analysis.

    NASA Astrophysics Data System (ADS)

    Todd, Martin; Cavazos, Carolina; Wang, Yi

    2013-04-01

    The Saharan atmospheric boundary layer (SABL) during summer is one of the deepest on Earth, and is crucial in controlling the vertical redistribution and long-range transport of dust in the Sahara. The SABL is typically made up of an actively growing convective layer driven by high sensible heating at the surface, with a deep, near-neutrally stratified Saharan residual layer (SRL) above it, which is mostly well mixed in humidity and temperature and reaches a height of ˜5-6km. These two layers are usually separated by a weak (≤1K) temperature inversion. Model representation of the SPBL structure and evolution is important for accurate weather/climate and aerosol prediction. In this work, we evaluate model performance of the Weather Research and Forecasting (WRF) to represent key multi-scale processes in the SABL during summer 2011, including depiction of the diurnal cycle. For this purpose, a sensitivity analysis is performed to examine the performance of seven PBL schemes (YSU, MYJ, QNSE, MYNN, ACM, Boulac and MRF) and two land-surface model (Noah and RUC) schemes. In addition, the sensitivity to the choice of lateral boundary conditions (ERA-Interim and NCEP) and land use classification maps (USGS and MODIS-based) is tested. Model outputs were confronted upper-air and surface observations from the Fennec super-site at Bordj Moktar and automatic weather station (AWS) in Southern Algeria Vertical profiles of wind speed, potential temperature and water vapour mixing ratio were examined to diagnose differences in PBL heights and model efficacy to reproduce the diurnal cycle of the SABL. We find that the structure of the model SABL is most sensitive the choice of land surface model and lateral boundary conditions and relatively insensitive to the PBL scheme. Overall the model represents well the diurnal cycle in the structure of the SABL. Consistent model biases include (i) a moist (1-2 gkg-1) and slightly cool (~1K) bias in the daytime convective boundary layer (ii

  9. The atmospheric boundary layer evening transitions: an observational and numerical study from two different datasets

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    Wu, D. L.; Ganeshan, M.

    2016-12-01

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

  11. Lidar observations of atmospheric internal waves in the boundary layer of the atmosphere on the coast of Lake Baikal

    NASA Astrophysics Data System (ADS)

    Banakh, Viktor A.; Smalikho, Igor N.

    2016-10-01

    Atmospheric internal waves (AIWs) in the boundary layer of atmosphere have been studied experimentally with the use of Halo Photonics pulsed coherent Doppler wind lidar Stream Line. The measurements were carried out over 14-28 August 2015 on the western coast of Lake Baikal (51°50'47.17'' N, 104°53'31.21'' E), Russia. The lidar was placed at a distance of 340 m from Lake Baikal at a height of 180 m above the lake level.

    A total of six AIW occurrences have been revealed. This always happened in the presence of one or two (in five out of six cases) narrow jet streams at heights of approximately 200 and 700 m above ground level at the lidar location. The period of oscillations of the wave addend of the wind velocity components in four AIW events was 9 min, and in the other two it was approximately 18 and 6.5 min. The amplitude of oscillations of the horizontal wind velocity component was about 1 m s-1, while the amplitude of oscillations of the vertical velocity was 3 times smaller. In most cases, internal waves were observed for 45 min (5 wave oscillations with a period of 9 min). Only once the AIW lifetime was about 4 h.

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

    NASA Astrophysics Data System (ADS)

    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

  13. A parametrization of the convective atmospheric boundary layer and its application into a global climate model

    NASA Astrophysics Data System (ADS)

    Holtslag, A. A. M.; Boville, B. A.; Moeng, C.-H.

    Vertical diffusion of heat and passive scalars (like moisture) in the convective atmospheric boundary layer are focused upon. Flux equations are analyzed with data obtained from large eddy simulations. The findings can be used in a modified flux gradient approach, which takes into account the nonlocal convective vertical exchange using the so called counter gradient transport and a nonlocal diffusivity coefficient. Previous findings are simplified and applied to a community climate model. The impact of the nonlocal approach is illustrated in comparison with the usual local diffusion approach.

  14. Atmospheric Boundary Layer Height Evolution with Lidar in Buenos Aires from 2008 to 2011

    NASA Astrophysics Data System (ADS)

    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.

  15. Modelling simulations of NOx and HOx in the middle and upper atmosphere using a 3D Whole Atmosphere Community Climate Model with D region ion-neutral chemistry

    NASA Astrophysics Data System (ADS)

    Feng, W.; Plane, J. M. C.; Kovacs, T.; Chipperfield, M.; Marsh, D. R.; Smith, A. K.; Verronen, P. T.; Newnham, D.; Clilverd, M. A.

    2016-12-01

    In the middle and upper atmosphere, the distributions of odd nitrogen NOx (NO, NO2) and odd hydrogen HOx (OH, HO2) are controlled by transport processes and chemistry. Energetic particle precipitation (of protons and electrons) produces NOx and HOx through ion-molecule chemistry, and this can play an important role in the chemistry of the mesosphere. There is also increasing evidence that the descent of NOx can destroy stratospheric O3 at high latitudes. Therefore, it is crucial to understand the importance of their production/loss rates, horizontal/vertical transport to advance our knowledge in the evolution of NOx and HOx as well as other related chemical species (e.g. HNO3, ClNO3, O and O3). Recently, we have developed a new coupled ion-neutral chemical model for the ionospheric D region (altitudes 50 - 90 km) based on the Sodankylä Ion and neutral Chemistry (SIC) model and 3D Whole Atmosphere Community Climate Model (WACCM), termed WACCM-SIC (Kovacs et al., 2016). An extra 306 ion-neutral and ion-recombination reactions of neutral species, positive and negative ions, and electrons have been added to the standard chemistry in WACCM. WACCM-SIC simulations have been performed to explore the relative contributions to mesospheric NO from auroral and medium energetic electrons, during the period 2013-2015. The modelled simulations are also compared with the available satellite measurements (e.g., temperature, O, H, and O3 from SABER, and NO from AIM) and ground-based microwave radiometer observations of mesospheric NO at Halley station (75oS). The interannual and inter-hemisphere differences will also be discussed.

  16. Determination of the Vertical Extinction Coefficient Profile in the Atmospheric Boundary Layer and the Free Troposphere

    NASA Astrophysics Data System (ADS)

    Adam, M.; Pahlow, M.; Kovalev, V.; Ondov, J.; Balin, I.; Simeonov, V.; van den Bergh, H.; Parlange, M.

    2003-04-01

    Elastic lidars were deployed in Baltimore (USA) and Jungfraujoch (Switzerland) with the goal of determining aerosol vertical extinction coefficient profiles in the atmospheric boundary layer (ABL) and free troposphere, respectively. This talk focuses on a comparision of methods to obtain the vertical extinction coefficient, specifically, 1) One Angle Method (OAM), 2) Optical Depth Method (ODM) and 3) Klett Method. The reference extinction coefficient values for the near point in the first method were obtained using Mie theory with particle size distribution and estimates of the refractive index from supporting ground measurements. For the ODM we use the optical depth measurements using a sun photometer. The reference far field value for the Klett method was obtained using standard atmospheric profiles.

  17. An equilibrium model for the coupled ocean-atmosphere boundary layer in the tropics

    NASA Technical Reports Server (NTRS)

    Sui, C.-H.; Lau, K.-M.; Betts, Alan K.

    1991-01-01

    An atmospheric convective boundary layer (CBL) model is coupled to an ocean mixed-layer (OML) model in order to study the equilibrium state of the coupled system in the tropics, particularly in the Pacific region. The equilibrium state of the coupled system is solved as a function of sea-surface temperature (SST) for a given surface wind and as a function of surface wind for a given SST. It is noted that in both cases, the depth of the CBL and OML increases and the upwelling below the OML decreases, corresponding to either increasing SST or increasing surface wind. The coupled ocean-atmosphere model is solved iteratively as a function of surface wind for a fixed upwelling and a fixed OML depth, and it is observed that SST falls with increasing wind in both cases. Realistic gradients of mixed-layer depth and upwelling are observed in experiments with surface wind and SST prescribed as a function of longitude.

  18. Boundary Layer Flow Control with a One Atmosphere Uniform Glow Discharge Surface Plasma

    NASA Technical Reports Server (NTRS)

    Roth, J. Reece; Sherman, Daniel M.; Wilkinson, Stephen P.

    1998-01-01

    Low speed wind tunnel data have been acquired for planar panels covered by a uniform, glow-discharge surface plasma in atmospheric pressure air known as the One Atmosphere Uniform Glow Discharge Plasma (OAUGDP). Streamwise and spanwise arrays of flush, plasma-generating surface electrodes have been studied in laminar, transitional, and fully turbulent boundary layer flow. Plasma between symmetric streamwise electrode strips caused large increases in panel drag, whereas asymmetric spanwise electrode configurations produced a significant thrust. Smoke wire flow visualization and mean velocity diagnostics show the primary cause of the phenomena to be a combination of mass transport and vortical structures induced by strong paraelectric ElectroHydroDynamic (EHD) body forces on the flow.

  19. Atmospheric stability of surface boundary layer in coastal region of the Wol-Ryong site

    NASA Astrophysics Data System (ADS)

    Lim, Hee-Chang

    2012-08-01

    In order to provide statistically reliable information of a wind energy site, accurate analysis on the atmospheric stability and climate characteristics in a certain area is a prerequisite. Two 2-D ultrasonic anemometers and one cup anemometer, located perpendicular to the prevailing wind direction, were used to measure the atmospheric wind environment at a height of 4.5 m in coastal region of the Wol-Ryong, Jeju, South Korea. The study is aiming to understand the atmospheric stability about a coastal region, and the effect of roughness length. We calculate the Monin-Obukhov length for division of atmospheric stability about unstable regime, neutral regime and stable regime. The distribution of diurnal Monin-Obukhov length is highly sporadic in the coastal region due to the effect of radiant heat from the surface or other environmental effects. In order to calculate the roughness length in coastal region, three different methods are applied in terms of the surface roughness, flow fluctuation and gust wind, which are called logarithmic profile, standard deviation and gust factor methods. In the study, the atmospheric stability was insignificant when applying these three methods. In the results, three different roughness length scales sufficiently showed the effect of obstacle and surface conditions around the measurement position. On the basis of an overall analysis of the short-term data measured in the Wol-Ryong area, Jeju Island, it is concluded that for the development of future wind energy resources, the Wol-Ryong site could be a good candidate for a future wind energy site.

  20. [Analysis on concentration variety characteristics of atmospheric ozone under the boundary layer in Beijing].

    PubMed

    Zong, Xue-Mei; Wang, Geng-Chen; Chen, Hong-Bin; Wang, Pu-Cai; Xuan, Yue-Jian

    2007-11-01

    Based on the atmospheric ozone sounding data, the average monthly and seasonal variety principles of atmospheric ozone concentration during six years are analyzed under the boundary layer in Beijing. The results show that the monthly variation of atmospheric ozone are obvious that the minimum values appear in January from less than 10 x 10(-9) on ground to less than 50 x 10(-9) on upper layer (2 km), but the maximum values appear in June from 85 x 10(-9) on ground to more than 90 x 10(-9) on upper layer. The seasonal variation is also clear that the least atmospheric ozone concentration is in winter and the most is in summer, but variety from ground to upper layer is largest in winter and least in summer. According to the type of outline, the outline of ozone concentration is composite of three types which are winter type, summer type and spring-autumn type. The monthly ozone concentration in different heights is quite different. After analyzing the relationship between ozone concentration and meteorological factors, such as temperature and humidity, we find ozone concentration on ground is linear with temperature and the correlation coefficient is more than 85 percent.

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

    PubMed

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

    2013-10-29

    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 chemical NOx sinks. Here, we present year-round observations of the multiisotopic composition of atmospheric nitrate in the tropical MBL at the Cape Verde Atmospheric Observatory. We show that the observed oxygen isotope ratios of nitrate are compatible with nitrate formation chemistry, which includes the BrNO3 sink at a level of ca. 20 ± 10% of nitrate formation pathways. The results also suggest that the N2O5 pathway is a negligible NOx sink in this environment. Observations further indicate a possible link between the NO2/NOx ratio and the nitrogen isotopic content of nitrate in this low NOx environment, possibly reflecting the seasonal change in the photochemical equilibrium among NOx species. This study demonstrates the relevance of using the stable isotopes of oxygen and nitrogen of atmospheric nitrate in association with concentration measurements to identify and constrain chemical processes occurring in the MBL.

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

    PubMed Central

    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 chemical NOx sinks. Here, we present year-round observations of the multiisotopic composition of atmospheric nitrate in the tropical MBL at the Cape Verde Atmospheric Observatory. We show that the observed oxygen isotope ratios of nitrate are compatible with nitrate formation chemistry, which includes the BrNO3 sink at a level of ca. 20 ± 10% of nitrate formation pathways. The results also suggest that the N2O5 pathway is a negligible NOx sink in this environment. Observations further indicate a possible link between the NO2/NOx ratio and the nitrogen isotopic content of nitrate in this low NOx environment, possibly reflecting the seasonal change in the photochemical equilibrium among NOx species. This study demonstrates the relevance of using the stable isotopes of oxygen and nitrogen of atmospheric nitrate in association with concentration measurements to identify and constrain chemical processes occurring in the MBL. PMID:23431201

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    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 chemical NOx sinks. Here, we present year-round observations of the multiisotopic composition of atmospheric nitrate in the tropical MBL at the Cape Verde Atmospheric Observatory. We show that the observed oxygen isotope ratios of nitrate are compatible with nitrate formation chemistry, which includes the BrNO3 sink at a level of ca. 20 ± 10% of nitrate formation pathways. The results also suggest that the N2O5 pathway is a negligible NOx sink in this environment. Observations further indicate a possible link between the NO2/NOx ratio and the nitrogen isotopic content of nitrate in this low NOx environment, possibly reflecting the seasonal change in the photochemical equilibrium among NOx species. This study demonstrates the relevance of using the stable isotopes of oxygen and nitrogen of atmospheric nitrate in association with concentration measurements to identify and constrain chemical processes occurring in the MBL.

  4. Influence of a high aerosol concentration on the thermal structure of the atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Khaikin, M. N.; Kuznetsova, I. N.; Kadygrov, E. N.

    2006-12-01

    The influence of increased concentrations of submicron aerosol produced by forest fires on thermal characteristics of the atmospheric boundary layer (ABL) in Moscow and its remote vicinity (the town of Zvenigorod) are analyzed on the basis of regular remote measurements of the ABL temperature profile with the use of MTP-5 profilers. In the air basin of a large city, additional aerosol and accompanying pollutants in early morning hours (at small heights of the Sun) most frequently did not cause substantial changes in the ABL thermal structure. In the locality remote from the megalopolis (Zvenigorod), the atmospheric pollution by aerosol led to noticeable changes in the ABL thermal characteristics. Especially strong changes were observed in the daytime, during the maximum supply of solar radiation. In morning hours, the heating rate of the lower 100-m layer of the polluted air exceeded the heating rate of a relatively pure air by more than one degree. In higher layers, the differences between the rates of temperature changes in a relatively clean atmosphere and in an atmosphere polluted by aerosol (in the suburb) were insignificant.

  5. The detection of clouds, aerosols and marine atmospheric boundary layer characteristics from simulated GLAS data

    NASA Technical Reports Server (NTRS)

    Palm, Stephen P.; Spinhirne, James D.

    1998-01-01

    Scheduled for launch in 2001 as part of NASA's Earth Observing System (EOS), the Geoscience Laser Altimeter System (GLAS) will provide continuous laser sounding of the earth's atmosphere from space for the first time. From its polar orbit about 600 km above the surface, GLAS will employ a 40 Hz solid state laser operating at 1064 nm to measure topography to an accuracy of 10 cm. Simultaneously, the atmospheric channels (1064 and 532 nm) of GLAS will provide profiles of atmospheric backscatter from 40 km to the ground with 75 meter vertical resolution (Spinhirne and Palm, 1996). These measurements will give scientists an unprecedented global data set on the vertical structure of clouds and aerosols which will greatly aid research efforts aimed at understanding their effects on climate and their role in climate change (Hartman, 1994). To better understand and predict the performance of the GLAS atmospheric channels, a computer model was developed to simulate the type of signal that the instrument would likely produce. The model uses aircraft lidar data and provides realistic simulated GLAS data sets over large areas spanning a wide range of atmospheric conditions. These simulated GLAS datasets are invaluable for designing and testing algorithms for the retrieval of parameters such as cloud and aerosol layer height, optical depth and extinction cross section. This work is currently proceeding and in this paper we will present results of the cloud and aerosol detection algorithm with emphasis on the detection of Marine Atmospheric Boundary Layer (MABL) aerosol. In addition, we use a recently developed technique to ascertain the feasability of estimating MABL moisture and temperature structure from spaceborne systems such as GLAS.

  6. The atmospheric neutral density experiment (ANDE) and modulating retroreflector in space (MODRAS): combined flight experiments for the space test program

    NASA Astrophysics Data System (ADS)

    Nicholas, Andrew C.; Gilbreath, G. Charmaine; Thonnard, Stefan E.; Kessel, R. A.; Lucke, Robert; Sillman, C. P.

    2003-03-01

    The Atmospheric Neutral Density Experiment (ANDE) is a low cost mission proposed by the Naval Research Laboratory to demonstrate a method to monitor the thermospheric neutral density at an altitude of 400 km. The primary mission objective is to provide total neutral density along the orbit for improved orbit determination of resident space objects. The ANDE mission also serves as a test platform for a new space-to-ground optical communications technique, the Modulating Retro-reflector Array in Space (MODRAS) experiment. Both are sponsored in part by the Department of Defense Space Test Program. The mission consists of two spherical spacecraft fitted with retro-reflectors for satellite laser ranging (SLR). One spacecraft is completely passive; the other carries three active instruments; a miniature Wind And Temperature Spectrometer (WATS) to measure atmospheric composition, cross-track winds and neutral temperature; a Global Positioning Sensor (GPS); and a Thermal Monitoring System (TMS) to monitor the temperature of the sphere. A design requirement of the active satellite is to telemeter the data to the ground without external protrusions from the spherical spacecraft (i.e. an antenna). The active satellite will be fitted with the MODRAS system, which is an enabling technology for the ANDE mission. The MODRAS system consists of a set of multiple quantum well (MQW) modulating retro-reflectors coupled with an electronics package, which will telemeter data to the ground by modulating the reflected light from laser interrogation beam. This paper presents a mission overview and emphasis will be placed on the design, optical layout, performance, ground station, and science capabilities of the combined missions.

  7. Complexation and synergistic boundary lubrication of porcine gastric mucin and branched poly(ethyleneimine) in neutral aqueous solution.

    PubMed

    Patil, Navinkumar J; Rishikesan, Sankaranarayanan; Nikogeorgos, Nikolaos; Guzzi, Rita; Lee, Seunghwan; Zappone, Bruno

    2017-01-18

    Lubrication of soft polydimethylsiloxane (PDMS) elastomer interfaces was studied in aqueous mixtures of porcine gastric mucin (PGM) and branched polyethyleneimine (b-PEI) at neutral pH and various ionic strengths (0.1-1.0 M). While neither PGM nor b-PEI improved lubrication compared to polymer-free buffer solution, their mixtures produced a synergistic lubricating effect by reducing friction coefficients by nearly two orders of magnitude, especially at slow sliding speed in the boundary lubrication regime. An array of spectroscopic studies revealed that small cationic b-PEI molecules were able to strongly bind and penetrate into large anionic PGM molecules, producing an overall contraction of the randomly coiled PGM conformation. The interaction also affected the structure of the folded PGM protein terminals, decreased the surface potential and increased light absorbance in PGM:b-PEI mixtures. Adding an electrolyte (NaCl) weakened the aggregation between PGM and b-PEI, and degraded the lubrication synergy, indicating that electrostatic interactions drive PGM:b-PEI complexation.

  8. Analytical Solutions to the Near-Neutral Atmospheric Surface Energy Balance with and without Heat Storage for Urban Climatological Studies.

    NASA Astrophysics Data System (ADS)

    Tso, C. P.; Chan, B. K.; Hashim, M. A.

    1991-04-01

    Analytical solutions are presented to the near-neutral atmospheric surface energy balance with the new approach of including the participation of heat storage in the building substrate. Analytical solutions are also presented for the first time for the case without heat storage effect. By a linearization process, the governing equations are simplified to a set of time-dependent, linear, first-order equations from which explicit solutions are readily obtainable. The results compare well with those obtained by numerical solutions upon the set without linearization when applied to the tropical city of Kuala Lumpur, Malaysia.

  9. An investigation of geometry and noise corrections to San Marco-C neutral atmospheric composition experiment data

    NASA Technical Reports Server (NTRS)

    Curtis, S. A.

    1972-01-01

    The problem of the calculation of ambient densities from San Marco-C neutral atmospheric composition experiment data is considered. A brief description is given of the data measurement method, followed by a description of both the theoretical and experimental data curves. Geometry, electrometer distortions, and noise effects are then studied in terms of their effects on the ideal data form. From these considerations two data reduction methods are evolved. The first is an iterative integration technique that exploits the symmetry of the experimental data about the minimum angle of attack. For the analysis of geometry effects, a second method using interval averaging was developed and studied.

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

    SciTech Connect

    Pu, Zhaoxia

    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.

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

    SciTech Connect

    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.

  12. Scale effects in wind tunnel modeling of an urban atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Kozmar, Hrvoje

    2010-03-01

    Precise urban atmospheric boundary layer (ABL) wind tunnel simulations are essential for a wide variety of atmospheric studies in built-up environments including wind loading of structures and air pollutant dispersion. One of key issues in addressing these problems is a proper choice of simulation length scale. In this study, an urban ABL was reproduced in a boundary layer wind tunnel at different scales to study possible scale effects. Two full-depth simulations and one part-depth simulation were carried out using castellated barrier wall, vortex generators, and a fetch of roughness elements. Redesigned “Counihan” vortex generators were employed in the part-depth ABL simulation. A hot-wire anemometry system was used to measure mean velocity and velocity fluctuations. Experimental results are presented as mean velocity, turbulence intensity, Reynolds stress, integral length scale of turbulence, and power spectral density of velocity fluctuations. Results suggest that variations in length-scale factor do not influence the generated ABL models when using similarity criteria applied in this study. Part-depth ABL simulation compares well with two full-depth ABL simulations indicating the truncated vortex generators developed for this study can be successfully employed in urban ABL part-depth simulations.

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

    NASA Astrophysics Data System (ADS)

    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.

  14. Giant aeolian dune size determined by the average depth of the atmospheric boundary layer.

    PubMed

    Andreotti, Bruno; Fourrière, Antoine; Ould-Kaddour, Fouzia; Murray, Brad; Claudin, Philippe

    2009-02-26

    Depending on the wind regime, sand dunes exhibit linear, crescent-shaped or star-like forms resulting from the interaction between dune morphology and sand transport. Small-scale dunes form by destabilization of the sand bed with a wavelength (a few tens of metres) determined by the sand transport saturation length. The mechanisms controlling the formation of giant dunes, and in particular accounting for their typical time and length scales, have remained unknown. Using a combination of field measurements and aerodynamic calculations, we show here that the growth of aeolian giant dunes, ascribed to the nonlinear interaction between small-scale superimposed dunes, is limited by the confinement of the flow within the atmospheric boundary layer. Aeolian giant dunes and river dunes form by similar processes, with the thermal inversion layer that caps the convective boundary layer in the atmosphere acting analogously to the water surface in rivers. In both cases, the bed topography excites surface waves on the interface that in turn modify the near-bed flow velocity. This mechanism is a stabilizing process that prevents the scale of the pattern from coarsening beyond the resonant condition. Our results can explain the mean spacing of aeolian giant dunes ranging from 300 m in coastal terrestrial deserts to 3.5 km. We propose that our findings could serve as a starting point for the modelling of long-term evolution of desert landscapes under specific wind regimes.

  15. Giant aeolian dune size determined by the average depth of the atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Claudin, P.; Fourrière, A.; Andreotti, B.; Murray, A. B.

    2009-12-01

    Depending on the wind regime, sand dunes exhibit linear, crescent-shaped or star-like forms resulting from the interaction between dune morphology and sand transport. Small-scale dunes form by destabilization of the sand bed with a wavelength (a few tens of metres) determined by the sand transport saturation length. The mechanisms controlling the formation of giant dunes, and in particular accounting for their typical time and length scales, have remained unknown. Using a combination of field measurements and aerodynamic calculations, we show here that the growth of aeolian giant dunes, ascribed to the nonlinear interaction between small-scale superimposed dunes, is limited by the confinement of the flow within the atmospheric boundary layer. Aeolian giant dunes and river dunes form by similar processes, with the thermal inversion layer that caps the convective boundary layer in the atmosphere acting analogously to the water surface in rivers. In both cases, the bed topography excites surface waves on the interface that in turn modify the near-bed flow velocity. This mechanism is a stabilizing process that prevents the scale of the pattern from coarsening beyond the resonant condition. Our results can explain the mean spacing of aeolian giant dunes ranging from 300 m in coastal terrestrial deserts to 3.5 km. We propose that our findings could serve as a starting point for the modelling of long-term evolution of desert landscapes under specific wind regimes.

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

    NASA Astrophysics Data System (ADS)

    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.

  17. Comparison between the atmospheric boundary layer in Paris and its rural suburbs during the ECLAP experiment

    NASA Astrophysics Data System (ADS)

    Dupont, E.; Menut, L.; Carissimo, B.; Pelon, J.; Flamant, P.

    The ECLAP experiment has been performed during the winter of 1995 in order to study the influence of the urban area of Paris on the vertical structure and diurnal evolution of the atmospheric boundary layer, in situations favourable to intense urban heat island and pollution increase. One urban site and one rural site have been instrumented with sodars, lidars and surface measurements. Additional radiosondes, 100 m masts and Eiffel Tower data were also collected. This paper gives a general overview of this experiment, and presents results of the analysis of four selected days, characterized by various wind directions and temperature inversion strengths. This analysis, which consists in a comparison between data obtained in the two sites, has been focused on three parameters of importance to the ABL dynamics: the standard deviation of vertical velocity, the surface sensible heat flux, and the boundary layer height. The vertical component of turbulence is shown to be enhanced by the urban area, the amplitude of this effect strongly depending on the meteorological situation. The sensible heat flux in Paris is generally found larger than in the rural suburbs. The most frequent differences range from 25-65 W m -2, corresponding to relative differences of 20-60%. The difference of unstable boundary layer height between both sites are most of the time less than 100 m. However, sodar and temperature data show that the urban influence is enhanced during night-time and transitions between stable and unstable regimes.

  18. Complex turbulent flow in the atmospheric boundary layer: Lab and field measurements of embedded canopy wakes

    NASA Astrophysics Data System (ADS)

    Markfort, C. D.; Carbajo Fuertes, F.; Porte-Agel, F.

    2015-12-01

    Natural and anthropogenic fragmented landscapes are pervasive and this complexity significantly affects the structure of the atmospheric boundary layer, causing classic similarity theories to break down. This is especially true in areas affected by wake turbulence. Steep topography and canopy patches can lead to separation of the boundary layer and delay in the adjustment of turbulence to an adjacent underlying surface. Canopy wakes have been shown, in controlled wind tunnel experiments, to significantly affect the mean and turbulence profiles compared to classic rough to smooth transitions (Markfort et al. 2014, Env. Fluid Mech.). The added turbulence due to wakes delay the development of a new boundary layer and turbulent flux measurements and models that rely on similarity theory to determine surface fluxes exhibit significant errors. Here we compare lab-scale experimental measurements using PIV to field-scale measurements using scanning Doppler wind LiDARs. The measurements provide information on how the wake evolves in space and varies over time. Results from the lab and field show a time-varying recirculation zone downwind of the canopy, enhanced turbulence extending far downwind of the transition and reduced surface fluxes in the wake region. The field measurements show that the open trunk space near the base of the canopy results in a surface jet that can be detected just downwind of the canopy and farther downwind dissipates as it mixes with the wake flow above. The implications of canopy wakes for measurements and modeling of surface fluxes will be discussed.

  19. Evolution of the atmospheric boundary-layer structure of an arid Andes Valley

    NASA Astrophysics Data System (ADS)

    Khodayar, S.; Kalthoff, N.; Fiebig-Wittmaack, M.; Kohler, M.

    2008-04-01

    The boundary-layer structure of the Elqui Valley is investigated, which is situated in the arid north of Chile and extends from the Pacific Ocean in the west to the Andes in the east. The climate is dominated by the south-eastern Pacific subtropical anticyclone and the cold Humboldt Current. This combination leads to considerable temperature and moisture gradients between the coast and the valley and results in the evolution of sea and valley wind systems. The contribution of these mesoscale wind systems to the heat and moisture budget of the valley atmosphere is estimated, based on radiosoundings performed near the coast and in the valley. Near the coast, a well-mixed cloud-topped boundary layer exists. Both, the temperature and the specific humidity do not change considerably during the day. In the stratus layer the potential temperature increases, while the specific humidity decreases slightly with height. The top of the thin stratus layer, about 300 m in depth, is marked by an inversion. Moderate sea breeze winds of 3-4 m s-1 prevail in the sub-cloud and cloud layer during daytime, but no land breeze develops during the night. The nocturnal valley atmosphere is characterized by a strong and 900 m deep stably stratified boundary layer. During the day, no pronounced well-mixed layer with a capping inversion develops in the valley. Above a super-adiabatic surface layer of about 150 m depth, a stably stratified layer prevails throughout the day. However, heating can be observed within a layer above the surface 800 m deep. Heat and moisture budget estimations show that sensible heat flux convergence exceeds cold air advection in the morning, while both processes compensate each other around noon, such that the temperature evolution stagnates. In the afternoon, cold air advection predominates and leads to net cooling of the boundary layer. Furthermore, the advection of moist air results in the accumulation of moisture during the noon and afternoon period, while

  20. Evaporation from soils subjected to natural boundary conditions at the land-atmospheric interface

    NASA Astrophysics Data System (ADS)

    Smits, K.; Illngasekare, T.; Ngo, V.; Cihan, A.

    2012-04-01

    Bare soil evaporation is a key process for water exchange between the land and the atmosphere and an important component of the water balance in semiarid and arid regions. However, there is no agreement on the best methodology to determine evaporation under different boundary conditions at the land surface. This becomes critical in developing models that couples land to the atmosphere. Because it is difficult to measure evaporation from soil, with the exception of using lysimeters, numerous formulations have been proposed to establish a relationship between the rate of evaporation and soil moisture and/or soil temperature and thermal properties. Different formulations vary in how they partition available energy. A need exists to systematically compare existing methods to experimental data under highly controlled conditions not achievable in the field. The goal of this work is to perform controlled experiments under transient conditions of soil moisture, temperature and wind at the land/atmospheric interface to test different conceptual and mathematical formulations for the soil surface boundary conditions to develop appropriate numerical models to be used in simulations. In this study, to better understand the coupled water-vapor-heat flow processes in the shallow subsurface near the land surface, we modified a previously developed theory by Smits et al. [2011] that allows non-equilibrium liquid/gas phase change with gas phase vapor diffusion to better account for dry soil conditions. The model did not implement fitting parameters such as a vapor enhancement factor that is commonly introduced into the vapor diffusion coefficient as an arbitrary multiplication factor. In order to experimentally test the numerical formulations/code, we performed a two-dimensional physical model experiment under varying boundary conditions using test sand for which the hydraulic and thermal properties were well characterized. Precision data under well-controlled transient heat and

  1. Traveling neutral disturbances. [acoustic-gravity wave coupling to minor species in atmosphere

    NASA Technical Reports Server (NTRS)

    Gross, S. H.; Eun, H.

    1976-01-01

    The coupling of acoustic-gravity waves in the main atmosphere to acoustic waves characteristic of individual minor species in the atmosphere is postulated. Such coupling would exist as a result of resonances in the response of the minor species, and its likelihood depends on the mass of the atmospheric particle relative to the major species mass, the diffusion of the minor species, and the direction of propagation of the main disturbance. These minor-species disturbances may explain some AE-C measurements in the thermosphere and could possibly play a role in the distribution of minor species and their chemistry in the mesosphere.

  2. Structure and Optical Properties of the Atmospheric Boundary Layer over Dusty Hot Deserts

    NASA Astrophysics Data System (ADS)

    Chalermthai, B.; Al Marzooqi, M.; Basha, G.; Ouarda, T.; Armstrong, P.; Molini, A.

    2014-12-01

    Strong sensible heat fluxes and deep turbulent mixing - together with marked dustiness and a low substrate water content - represent a characteristic signature of the atmospheric boundary layer (ABL) over hot deserts, resulting in "thicker" mixing layers and peculiar optical properties. Beside these main common features however, desert boundary layers present extremely complex local structures that have been scarcely addressed in the literature, and whose understanding is essential in modeling processes such as transport and deposition of dust and pollutants, local wind fields, turbulent fluxes and their impacts on the sustainable development, human health and solar energy harvesting in these regions. In this study, we explore the potential of the joint usage of Lidar Ceilometer backscattering profiles and sun-photometer optical depth retrievals to quantitatively determine the vertical aerosol profile over dusty hot desert regions. Toward this goal, we analyze a continuous record of observations of the atmospheric boundary layer height from a single lens LiDAR ceilometer operated at Masdar Institute Field Station (24.4425N 54.6163E, Abu Dhabi, United Arab Emirates), starting March 2013, and the concurrent measurements of aerosol optical depth derived independently from the Masdar Institute AERONET sun-photometer. The main features of the desert ABL are obtained from the ceilometer range corrected backscattering profiles through bi-dimensional clustering technique we developed as a modification of the recently proposed single-profile clustering method, and therefore "directly" and "indirectly" calibrated to obtain a full diurnal cycle climatology of the aerosol optical depth and aerosol profiles. The challenges and the advantages of applying a similar methodology to the monitoring of aerosols and dust over hyper-arid regions are also discussed, together with the issues related to the sensitivity of commercial ceilometers to changes in the solar background.

  3. Formulation of non-reflecting boundary conditions in numerical models of the atmosphere

    NASA Astrophysics Data System (ADS)

    Kar, Sajal Kumar

    To eliminate/minimize spurious reflections of small-scale gravity-inertia waves at the material-surface upper boundary of a numerical model of the atmosphere, an energy-absorbing sponge layer is formulated. The sponge layer is designed for forced internal gravity-inertia waves in a resting isothermal atmosphere on an f-plane. The sponge layer is introduced immediately below the material-surface upper boundary. The sponge terms appear as linear damping of the vorticity, divergence, and temperature perturbations inside the sponge layer. The damping coefficient (L) is same for all sponge terms. For small-scale gravity-inertia waves that are most effective in propagating vertical wave energy upwards, two approximate forms of L, namely L(sub 1) and L(sub 2) are derived, neither of which explicitly depend on the sign of frequency and equivalent depth, and as such either can be readily implemented into a time-dependent model. The sponge layer with the coefficient L(sub 1) is designed for a spectral model. The sponge layer with the coefficient L(sub 2), on the other hand, is designed for a finite-difference. The sponge layers in linear time-dependent models were implemented and tested. A lateral sponge layer is designed for linear one-dimensional shallow-water gravity waves. The damping terms inside the sponge layer can selectively damp the characteristic variable advected back (or reflected) into the model domain from the lateral boundary. The lateral sponge layer was implemented in a linear time-dependent model.

  4. A Massively Parallel Particle Code for Rarefied Ionized and Neutral Gas Flows in Earth and Planetary Atmospheres, Ionospheres and Magnetospheres

    NASA Technical Reports Server (NTRS)

    Combi, Michael R.

    2004-01-01

    In order to understand the global structure, dynamics, and physical and chemical processes occurring in the upper atmospheres, exospheres, and ionospheres of the Earth, the other planets, comets and planetary satellites and their interactions with their outer particles and fields environs, it is often necessary to address the fundamentally non-equilibrium aspects of the physical environment. These are regions where complex chemistry, energetics, and electromagnetic field influences are important. Traditional approaches are based largely on hydrodynamic or magnetohydrodynamic MHD) formulations and are very important and highly useful. However, these methods often have limitations in rarefied physical regimes where the molecular collision rates and ion gyrofrequencies are small and where interactions with ionospheres and upper neutral atmospheres are important.

  5. Sensitivity of Radar Wave Propagation Power to the Marine Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Lentini, N.; Hackett, E. E.

    2014-12-01

    Radar is a remote sensor used for scientific, meteorological, and military applications. Radar waves are affected by the medium through which they propagate, impacting the accuracy of radar measurements. Thus, environmental effects should be understood and quantified. The marine atmospheric boundary layer (MABL) is highly dynamic and turbulent, and affects radar wave propagation. The ocean surface roughness impacts scattering behavior. These effects cause variability in constructive and destructive interference patterns due to reflection from the ocean surface, known as multipath. The atmospheric effects cause radar waves to attenuate and refract; this study focuses on the refractive effects. A high-fidelity, physics-based, parabolic wave equation simulation is used to model the radar propagation and accounts for effects of the rough ocean surface (wind seas and swell) as well as variable refractivity with height and range. We use a robust, variance based, sensitivity analysis method called the Extended Fourier Amplitude Sensitivity Test to quantify which environmental parameters have the most significant effect on the modeled radar wave propagation. In this sensitivity study, the environment is parameterized by 16 variables, 8 ocean surface and 8 atmospheric. Sensitivity analysis is performed for 3 radar frequencies (3, 9, and 15 GHz) and 2 polarizations (horizontal and vertical). Results indicate that radar wave propagation is more sensitive to atmospheric parameters than ocean surface parameters. The mixed layer has the most far-reaching effect over the entire model domain (a range of 60 km and altitudes up to 1 km), characterized by its height and refractivity gradient. The remaining important factors have a predominantly local effect in the region where they occur in the MABL atmospheric structure. At low altitudes, radar wave propagation power is most sensitive to the gradient and curvature of the vertical refractivity profile. This research provides insight

  6. On the Use of Blanketed Atmospheres as Boundary Conditions for Stellar Evolutionary Models

    NASA Astrophysics Data System (ADS)

    VandenBerg, Don A.; Edvardsson, Bengt; Eriksson, Kjell; Gustafsson, Bengt

    2008-03-01

    Stellar models have been computed for stars having [ Fe/H ] = 0.0 (assuming both the Grevesse & Sauval and Asplund et al. heavy-element mixtures) and -2.0 to determine the effects on the predicted Teff scale of using boundary conditions derived from the latest MARCS model atmospheres. The latter were fitted in a fully consistent way to the interior models at the photosphere and at τ = 100: the resultant evolutionary sequences on the H-R diagram were found to be nearly independent of the chosen fitting point. Tracks were also computed in which the pressure at T = Teff was obtained by integrating the hydrostatic equation together with either the classical gray T(τ , Teff) relation or that derived by Krishna Swamy from an empirical solar atmosphere. Due to the effects of differences in the solar-calibrated values of the mixing-length parameter, αMLT, very similar tracks were obtained for the different treatments of the atmosphere, except at solar abundances, where the models based on the Krishna Swamy T(τ , Teff) relationship predicted ~150 K hotter giant branches than the others, in good agreement with the inferred temperatures of giants in the open cluster M67 from recent (V - K) -Teff relations. Tracks that used new ``scaled solar, differentially corrected'' MARCS atmospheres were found to agree well with those that employed the Krishna Swamy T(τ , Teff) relationship, independently of the assumed metal abundance. (Gray atmospheres are quite different from MARCS models.) Fits of isochrones for [ Fe/H ] = - 2.0 to the CMD of the globular cluster M68, as well as the possibility that αMLT varies with stellar parameters, are also discussed.

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

    NASA Astrophysics Data System (ADS)

    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

  8. Numerical Modeling of the Propagation Environment in the Atmospheric Boundary Layer over the Persian Gulf.

    NASA Astrophysics Data System (ADS)

    Atkinson, B. W.; Li, J.-G.; Plant, R. S.

    2001-03-01

    Strong vertical gradients at the top of the atmospheric boundary layer affect the propagation of electromagnetic waves and can produce radar ducts. A three-dimensional, time-dependent, nonhydrostatic numerical model was used to simulate the propagation environment in the atmosphere over the Persian Gulf when aircraft observations of ducting had been made. A division of the observations into high- and low-wind cases was used as a framework for the simulations. Three sets of simulations were conducted with initial conditions of varying degrees of idealization and were compared with the observations taken in the Ship Antisubmarine Warfare Readiness/Effectiveness Measuring (SHAREM-115) program. The best results occurred with the initialization based on a sounding taken over the coast modified by the inclusion of data on low-level atmospheric conditions over the Gulf waters. The development of moist, cool, stable marine internal boundary layers (MIBL) in air flowing from land over the waters of the Gulf was simulated. The MIBLs were capped by temperature inversions and associated lapses of humidity and refractivity. The low-wind MIBL was shallower and the gradients at its top were sharper than in the high-wind case, in agreement with the observations. Because it is also forced by land-sea contrasts, a sea-breeze circulation frequently occurs in association with the MIBL. The size, location, and internal structure of the sea-breeze circulation were realistically simulated. The gradients of temperature and humidity that bound the MIBL cause perturbations in the refractivity distribution that, in turn, lead to trapping layers and ducts. The existence, location, and surface character of the ducts were well captured. Horizontal variations in duct characteristics due to the sea-breeze circulation were also evident. The simulations successfully distinguished between high- and low-wind occasions, a notable feature of the SHAREM-115 observations. The modeled magnitudes of duct

  9. A simple formula for estimating Stark widths of neutral lines. [of stellar atmospheres

    NASA Technical Reports Server (NTRS)

    Freudenstein, S. A.; Cooper, J.

    1978-01-01

    A simple formula for the prediction of Stark widths of neutral lines similar to the semiempirical method of Griem (1968) for ion lines is presented. This formula is a simplification of the quantum-mechanical classical path impact theory and can be used for complicated atoms for which detailed calculations are not readily available, provided that the effective position of the closest interacting level is known. The expression does not require the use of a computer. The formula has been applied to a limited number of neutral lines of interest, and the width obtained is compared with the much more complete calculations of Bennett and Griem (1971). The agreement generally is well within 50% of the published value for the lines investigated. Comparisons with other formulas are also made. In addition, a simple estimate for the ion-broadening parameter is given.

  10. A simple formula for estimating Stark widths of neutral lines. [of stellar atmospheres

    NASA Technical Reports Server (NTRS)

    Freudenstein, S. A.; Cooper, J.

    1978-01-01

    A simple formula for the prediction of Stark widths of neutral lines similar to the semiempirical method of Griem (1968) for ion lines is presented. This formula is a simplification of the quantum-mechanical classical path impact theory and can be used for complicated atoms for which detailed calculations are not readily available, provided that the effective position of the closest interacting level is known. The expression does not require the use of a computer. The formula has been applied to a limited number of neutral lines of interest, and the width obtained is compared with the much more complete calculations of Bennett and Griem (1971). The agreement generally is well within 50% of the published value for the lines investigated. Comparisons with other formulas are also made. In addition, a simple estimate for the ion-broadening parameter is given.

  11. The Wind and Temperature Spectrometer (WTS) in the Atmospheric Neutral Density Experiment (ANDE) Satellite

    NASA Technical Reports Server (NTRS)

    Herrero, F. A.; Vancil, B.; Nicholas, A.; Zaruba, C.; Beasley, L.

    2004-01-01

    Miniaturization efforts in new spectrometers for ionosphere/thermosphere investigations of the ion-drifts and neutral winds and corresponding temperatures make possible very light (about 250 g) packages consuming less than 0.4 W. Previously described, our approach measures the angular and energy distributions of neutral atoms and molecules (or ions) in two perpendicular planes; using those distributions to determine the full wind vector, the temperature and the relative densities of O and N2, as required for the ANDE mission. The measurements require two separate electron impact ion sources each with its own electron beam cathode. We have developed a low-temperature thermionic emission cathode that delivers 1 mA electron current at 80 mW power, making it possible to operate neutral wind-temperature experiments for the first time with powers less than 0.5 W. Advances in the ion optics of the energy-angle spectrometer enhance the energy resolution-aperture product more than a factor of 3 to enable energy resolutions of a few percent with large apertures. With these technology improvements it is now possible to obtain the full neutral wind vector, temperature and O/N2, density ratio once per second in a 250g/0.4W package with sensitivity up to about 500 km altitude in the thermosphere. We will describe the WTS as deployed in ANDE and show simulated data with the non-linear least squares analysis to illustrate expected performance of the WTS in the estimated errors in the three components of the wind, the temperature, and the relative densities.

  12. Mass spectrometry of positive ions and neutral species in the effluent of an atmospheric pressure plasma with hexamethyldisiloxane and oxygen

    NASA Astrophysics Data System (ADS)

    Benedikt, J.; Ellerweg, D.; Schneider, S.; Rügner, K.; R, Reuter; Kersten, H.; Benter, T.

    2013-11-01

    The effluent of a non-equilibrium atmospheric pressure plasma jet in He with admixture of hexamethyldisiloxane (HMDSO) and O2 has been investigated by means of molecular beam mass spectrometry. Positive ions and neutral plasma chemistry products have been detected and their possible role in the deposition of good-quality SiO2 films is discussed. Positive ion spectra reveal the presence of protonated water clusters and H+ : HMDSO and H3O+ : HMDSO ions. These ions are most probably produced by photoionization. This is corroborated by optical emission spectroscopy data obtained in the wavelength range of 50-300 nm, where helium excimer continuum emission centred around 84 nm has been observed. No ion driven polymerization products of HMDSO have been detected. Measurements of neutral species have allowed the quantification of the HMDSO depletion and absolute densities of trimethylsilanol and pentamethyldisiloxane. Two neutral polymerization products have been observed as well. The results indicate that the Si-O bond of HMDSO is preferentially broken. Additionally, the mass balance of plasma chemistry products is discussed.

  13. An equilibrium model for the coupled ocean-atmosphere boundary layer in the tropics

    NASA Astrophysics Data System (ADS)

    Sui, C.-H.; Lau, K.-M.; Betts, Alan K.

    A coupled model is used to study the equilibrium state of the ocean-atmosphere boundary layer in the tropics. The atmospheric model is a one-dimensional thermodynamic model for a partially mixed, partly cloudy convective boundary layer (CBL), including the effects of cloud-top subsidence, surface momentum and heat (latent and sensible) fluxes, and realistic radiative transfer for both shortwaves and longwaves (Betts and Ridgway, 1988; 1989). The oceanic model is a thermodynamic model for a well-mixed layer, with a closure constraint based on a one-dimensional turbulent kinetic energy (TKE) equation following Kraus and Turner (1967). Results of several sets of experiments are reported in this paper. In the first two sets of experiments, with sea surface temperature (SST) specified, we solve the equilibrium state of the coupled system as a function of SST for a given surface wind (case 1) and as a function of surface wind for a given SST (case 2). In both cases the depth of the CBL and the ocean mixed layer (OML) increases and the upwelling below the OML decreases, corresponding to either increasing SST or increasing surface wind. The deepening of the equilibrium CBL is primarily linked to the increase of CBL moisture with increasing SST and surface wind. The increase of OML depth and decrease of upwelling are due to a decrease of net downward heat flux with increasing SST and the generation of TKE by increasing wind. In another two sets of experiments, we solve for the coupled ocean-atmosphere model iteratively as a function of surface wind for a fixed upwelling (case 3) and a fixed OML depth (case 4). SST falls with increasing wind in both cases, but the fall is steeper in case 4, because the OML depth is fixed, whereas in case 3 the depth is allowed to deepen and the cooling is spread over a larger mass of water. The decrease of evaporation with increasing wind in case 4 leads to a very dry and shallow CBL. Results of further experiments with surface wind and SST

  14. Spatial Variability of Atmospheric Boundary Layer Structure over the Eastern Equatorial Pacific.

    NASA Astrophysics Data System (ADS)

    Yin, Bingfan; Albrecht, Bruce A.

    2000-05-01

    Variations in the atmospheric boundary layer structure over the eastern equatorial Pacific are analyzed using 916 soundings collected during the First Global Atmospheric Research Program Global Experiment. Unstable boundary layer structures are observed much more frequently in soundings north of the ocean front located near 2.5°N in the eastern equatorial Pacific than in soundings south of the front. An objective criterion is applied to identify the presence of the transition layer, a weak stable layer near cloud base, in the soundings. The transition is observed in about 45% of the soundings in both the unstable and the inversion categories. A comparison of soundings over the cold tongue with those over the ITCZ indicates that differences in static stability between these regions are limited to the layer from the surface to about 850 mb, which is the mean height of the inversions capping the cloud layer over the cold tongue. The cold tongue soundings on average are found to be drier from the surface to 300 mb than the ITCZ soundings with the largest average difference (5 g kg1) between these two groups of soundings observed just above the inversion layer. Compensating subsidence from the ITCZ may account for some of the drying observed just above the cold tongue inversions, although horizontal advection may also be a factor. North-south cross sections (10°S-15°N) of potential temperature, mixing ratio, equivalent potential temperature, and meridional wind across the cold tongue-ITCZ complex (CTIC) were constructed for two longitudinal bands: 95°-105°W and 105°-115°W. There is little latitudinal variation of the average height of the trade inversion and the height of the transition layer across the CTIC. Although the average lifting condensation level (LCL) at 980 mb is located near the average top of the transition layers observed over the cold tongue, the average 980-mb LCL is close to the average height of the base of the transition layers observed over

  15. Spacelab 2 Upper Atmospheric Modification experiment over Arecibo. I - Neutral gas dynamics

    NASA Technical Reports Server (NTRS)

    Bernhardt, P. A.; Kashiwa, B. A.; Tepley, C. A.; Noble, S. T.

    1988-01-01

    The Orbital Maneuvering Subsystem engines of the Space Shuttle were used to inject H2, CO2, H2O and other combustion products into the upper atmosphere over the Arecibo Observatory. Images of the airglow enhancements that resulted from chemical reactions between the exhaust gases and the F-layer plasma showed that the exhaust vapor trail came to rest 80 km downstream from the center of the burn. A computer simulation of the gas dynamics shows that the region of the burn was dominated by a 'snow plow' effect sweeping out a corridor in the atmosphere and collisionally heating the injected vapors.

  16. Radical product yields from the ozonolysis of short chain alkenes under atmospheric boundary layer conditions.

    PubMed

    Alam, Mohammed S; Rickard, Andrew R; Camredon, Marie; Wyche, Kevin P; Carr, Timo; Hornsby, Karen E; Monks, Paul S; Bloss, William J

    2013-11-27

    The gas-phase reaction of ozone with unsaturated volatile organic compounds (VOCs), alkenes, is an important source of the critical atmospheric oxidant OH, especially at night when other photolytic radical initiation routes cannot occur. Alkene ozonolysis is also known to directly form HO2 radicals, which may be readily converted to OH through reaction with NO, but whose formation is poorly understood. We report a study of the radical (OH, HO2, and RO2) production from a series of small alkenes (propene, 1-butene, cis-2-butene, trans-2-butene, 2-methylpropene, 2,3-dimethyl-2-butene (tetramethyl ethene, TME), and isoprene). Experiments were performed in the European Photoreactor (EUPHORE) atmospheric simulation chamber, with OH and HO2 levels directly measured by laser-induced fluorescence (LIF) and HO2 + ΣRO2 levels measured by peroxy-radical chemical amplification (PERCA). OH yields were found to be in good agreement with the majority of previous studies performed under comparable conditions (atmospheric pressure, long time scales) using tracer and scavenger approaches. HO2 yields ranged from 4% (trans-2-butene) to 34% (2-methylpropene), lower than previous experimental determinations. Increasing humidity further reduced the HO2 yields obtained, by typically 50% for an RH increase from 0.5 to 30%, suggesting that HOx production from alkene ozonolysis may be lower than current models suggest under (humid) ambient atmospheric boundary layer conditions. The mechanistic origin of the OH and HO2 production observed is discussed in the context of previous experimental and theoretical studies.

  17. An atmospheric pCO2 reconstruction across the Cretaceous-Tertiary boundary from leaf megafossils

    PubMed Central

    Beerling, D. J.; Lomax, B. H.; Royer, D. L.; Upchurch, G. R.; Kump, L. R.

    2002-01-01

    The end-Cretaceous mass extinctions, 65 million years ago, profoundly influenced the course of biotic evolution. These extinctions coincided with a major extraterrestrial impact event and massive volcanism in India. Determining the relative importance of each event as a driver of environmental and biotic change across the Cretaceous-Tertiary boundary (KTB) crucially depends on constraining the mass of CO2 injected into the atmospheric carbon reservoir. Using the inverse relationship between atmospheric CO2 and the stomatal index of land plant leaves, we reconstruct Late Cretaceous-Early Tertiary atmospheric CO2 concentration (pCO2) levels with special emphasis on providing a pCO2 estimate directly above the KTB. Our record shows stable Late Cretaceous/Early Tertiary background pCO2 levels of 350–500 ppm by volume, but with a marked increase to at least 2,300 ppm by volume within 10,000 years of the KTB. Numerical simulations with a global biogeochemical carbon cycle model indicate that CO2 outgassing during the eruption of the Deccan Trap basalts fails to fully account for the inferred pCO2 increase. Instead, we calculate that the postboundary pCO2 rise is most consistent with the instantaneous transfer of ≈4,600 Gt C from the lithic to the atmospheric reservoir by a large extraterrestrial bolide impact. A resultant climatic forcing of +12 W⋅m−2 would have been sufficient to warm the Earth's surface by ≈7.5°C, in the absence of counter forcing by sulfate aerosols. This finding reinforces previous evidence for major climatic warming after the KTB impact and implies that severe and abrupt global warming during the earliest Paleocene was an important factor in biotic extinction at the KTB. PMID:12060729

  18. An atmospheric pCO2 reconstruction across the Cretaceous-Tertiary boundary from leaf megafossils.

    PubMed

    Beerling, D J; Lomax, B H; Royer, D L; Upchurch, G R; Kump, L R

    2002-06-11

    The end-Cretaceous mass extinctions, 65 million years ago, profoundly influenced the course of biotic evolution. These extinctions coincided with a major extraterrestrial impact event and massive volcanism in India. Determining the relative importance of each event as a driver of environmental and biotic change across the Cretaceous-Tertiary boundary (KTB) crucially depends on constraining the mass of CO(2) injected into the atmospheric carbon reservoir. Using the inverse relationship between atmospheric CO(2) and the stomatal index of land plant leaves, we reconstruct Late Cretaceous-Early Tertiary atmospheric CO(2) concentration (pCO(2)) levels with special emphasis on providing a pCO(2) estimate directly above the KTB. Our record shows stable Late Cretaceous/Early Tertiary background pCO(2) levels of 350-500 ppm by volume, but with a marked increase to at least 2,300 ppm by volume within 10,000 years of the KTB. Numerical simulations with a global biogeochemical carbon cycle model indicate that CO(2) outgassing during the eruption of the Deccan Trap basalts fails to fully account for the inferred pCO(2) increase. Instead, we calculate that the postboundary pCO(2) rise is most consistent with the instantaneous transfer of approximately 4,600 Gt C from the lithic to the atmospheric reservoir by a large extraterrestrial bolide impact. A resultant climatic forcing of +12 W.m(-2) would have been sufficient to warm the Earth's surface by approximately 7.5 degrees C, in the absence of counter forcing by sulfate aerosols. This finding reinforces previous evidence for major climatic warming after the KTB impact and implies that severe and abrupt global warming during the earliest Paleocene was an important factor in biotic extinction at the KTB.

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

    NASA Astrophysics Data System (ADS)

    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. Dissolved inorganic carbon and stable carbon isotopic evolution of neutral mine drainage interacting with atmospheric CO2(g).

    PubMed

    Abongwa, Pride Tamasang; Atekwana, Eliot Anong; Puckette, James

    2016-03-01

    We investigated the spatial variations in the concentrations of dissolved inorganic carbon (DIC), the stable carbon isotopic composition (δ(13)C) of DIC and the δ(13)C of carbonate precipitated from neutral mine drainage interacting with the atmospheric CO2(g). We assessed the chemical, DIC and δ(13)CDIC evolution of the mine drainage and the δ(13)C evolution of carbonate precipitates for a distance of 562 m from the end of an 8 km tunnel that drains a mine. Our results show that as the mine drainage interacts with atmospheric CO2(g) the outgassing of CO2 due to the high initial partial pressure of CO2 (pCO2) causes the DIC to evolve under kinetic conditions followed by equilibration and then under equilibrium conditions. The carbonate evolution was characterized by spatial increases in pH, decreasing concentrations of Ca(2+) and DIC and by the precipitation of carbonate. The δ(13)CDIC showed a larger enrichment from the tunnel exit to 38 m, moderate continuous enrichment to 318 m and almost no enrichment to 562 m. On the other hand, the δ(13)C of the carbonate precipitates also showed large enrichment from the tunnel exit to 38 m, moderate enrichment to 318 m after which the δ(13)C remained nearly constant. The enrichment in the δ(13)C of the DIC and the carbonate precipitates from 0 to 38 m from kinetic fractionation caused by CO2(g) outgassing was followed by a mix of kinetic fractionation and equilibrium fractionation controlled by carbon exchange between DIC and atmospheric CO2(g) to 318 m and then by equilibrium fractionation from 318 to 562 m. From the carbonate evolution in this neutral mine drainage, we estimated that 20% of the carbon was lost via CO2 outgassing, 12% was sequestered in sediments in the drainage ponds from calcite precipitation and the remainder 68% was exported to the local stream.

  1. Termolecular Ion-Molecules Reactions in Titan's Atmosphere. I. Principal Ions with Principal Neutrals

    NASA Technical Reports Server (NTRS)

    Anicich, V.; Milligan, D.; Fairley, D.; McEwan, M.

    1999-01-01

    The FA-SIFT experiment at Canterbury was used to determine some of the principal termolecular ion-molecule reactions that occur in Saturn's satellite Titan's atmosphere. The experiments were performed using both a pure nitrogen bath gas and a pure helium bath gas.

  2. Termolecular Ion-Molecules Reactions in Titan's Atmosphere. I. Principal Ions with Principal Neutrals

    NASA Technical Reports Server (NTRS)

    Anicich, V.; Milligan, D.; Fairley, D.; McEwan, M.

    1999-01-01

    The FA-SIFT experiment at Canterbury was used to determine some of the principal termolecular ion-molecule reactions that occur in Saturn's satellite Titan's atmosphere. The experiments were performed using both a pure nitrogen bath gas and a pure helium bath gas.

  3. The Role of Spectroscopy in Research on the Neutral Atmospheres of the Outer Solar System

    NASA Astrophysics Data System (ADS)

    Orton, Glenn S.

    2013-06-01

    Remote-sensing observations of Jupiter, Saturn, Uranus and Neptune, as well as Titan - Saturn's largest satellite, and the spectroscopic information required to interpret these observations play a pivotal role in the exploration of the atmospheres of the outer solar system. We rely on well-mixed constituents to derive temperatures unambiguously, with only the collision-induced absorption and quadrupole transitions of H_2 and CH_4 in Jupiter and Saturn fulfilling that role. Condensate and chemically disequilibrated molecules (e.g. NH_3 and PH_3) act as indirect tracers that inform us of the strength of vertical winds. Higher-order hydrocarbons are present in all these atmospheres and their abundances and distribution acts as a tracer for stratospheric circulation and chemistry. The platforms on which planetary spectroscopy is done include a variety of ground-based facilities that observe the planets from the visible through radio regions. Airborne facilities, such as NASA's SOFIA, together with Earth-proximal facilities in space, allow both increased sensitivity and wider spectral access. Spectrometers on interplanetary missions have allowed us to examine the spatial and temporal variability of atmospheric properties that are not possible from the Earth. Several needs and challenges remain, and a constant dialog between those in the planetary exploration community and laboratory spectroscopists and theorists has been and will continue to be an important component of progress in atmospheric research. -

  4. Neutral Middle Atmospheric Influences by the Extremely Large October 2003 Solar Proton

    NASA Technical Reports Server (NTRS)

    Jackman, C. H.; Fleming, E. L.

    2004-01-01

    The huge coronal mass ejection (CME) on October 28, 2003 caused an extremely large solar proton event (SPE) 3t the Earth, which impacted the middle atmospheric polar cap regions. The highly energetic protons produce ionizations, excitations, dissociations, and dissociative ionizations of the background constituents, which lead to the production of HO(x) (H, OH, HO2) and NO(y) (N, NO, NO2, NO3, N2O5, HNO3, HO2NO2, ClONO2, BrONO2). The total production of middle atmospheric NO(y) molecules by individual SPEs can be used to compare their sizes. Using this scale, the extremely large October 2003 SPE was the fourth largest in the past 40 years and the second largest of solar cycle 23. Only the October 1989, August 1972, and July 2000 SPEs were larger. The Goddard Space Flight Center (CSFC) Two-dimensional (2D)) Model was used in computing the influence of this gigantic SPE The NO(y) amount was increased by over two orders of Atmosphere Research Satellite (UARS) Halogen Occultation Experiment (HALOE) measurements as a result of this noteworthy SPE. The model also calculated polar middle mesosphere ozone decreases of over 70% during the SPE. Other atmospheric impacts from both model predictions and measurements as a result of this major SPE will be discussed in this paper.

  5. Neutral Middle Atmospheric Influences by the Extremely Large October 2003 Solar Proton Event

    NASA Technical Reports Server (NTRS)

    Jackman, C. H.; Fleming, E. L.

    2004-01-01

    The huge coronal mass ejection (CME) on October 28,2003 caused an extremely large solar proton event (SPE) at the Earth, which impacted the middle atmospheric polar cap regions. The highly energetic protons produce ionizations, excitations, dissociations, and dissociative ionizations of the background constituents, which lead to the production of HOx (H, OH, HO2) and NOy (N, NO, NO2, NO3, N2O5, HNO3, HO2NO2, ClONO2, BrONO2). The total production of middle atmospheric NOy molecules by individual SPEs can be used to compare their sizes. Using this scale, the extremely large October 2003 SPE was the fourth largest in the past 40 years and the second largest of solar cycle 23. Only the October 1989, August 1972, and July 2000 SPEs were larger. The Goddard Space Flight Center (GSFC) Two-dimensional (2D) Model was used in computing the influence of this gigantic SPE. The NOy amount was increased by over two orders of magnitude in the mesosphere in both the GSFC 2D Model computations and Upper Atmosphere Research Satellite (UARS) Halogen Occultation Experiment (HALOE) measurements as a result of this noteworthy SPE. The model also calculated polar middle mesospheric ozone decreases of over 70% during the SPE. Other atmospheric impacts from both model predictions and measurements as a result of this major SPE will be discussed in this paper.

  6. Remote Sensing of Icy Galilean Moon Surface and Atmospheric Composition Using Low Energy (1 eV-4 keV) Neutral Atom Imaging

    NASA Technical Reports Server (NTRS)

    Collier, M. R.; Sittler, E.; Chornay, D.; Cooper, J. F.; Coplan, M.; Johnson, R. E.

    2004-01-01

    We describe a low energy neutral atom imager suitable for composition measurements Europa and other icy Galilean moons in the Jovian magnetosphere. This instrument employs conversion surface technology and is sensitive to either neutrals converted to negative ions, neutrals converted to positive ions and the positive ions themselves depending on the power supply. On a mission such as the Jupiter Icy Moons Orbiter (JIMO), two back-to-back sensors would be flown with separate power supplies fitted to the neutral atom and iodneutral atom sides. This will allow both remote imaging of 1 eV < E < 4 keV neutrals from icy moon surfaces and atmospheres, and in situ measurements of ions at similar energies in the moon ionospheres and Jovian magnetospheric plasma. The instrument provides composition measurements of the neutrals and ions that enter the spectrometer with a mass resolution dependent on the time-of-flight subsystem and capable of resolving molecules. The lower energy neutrals, up to tens of eV, arise from atoms and molecules sputtered off the moon surfaces and out of the moon atmospheres by impacts of more energetic (keV to MeV) ions from the magnetosphere. Direct Simulation Monte Carlo (DSMC) models are used to convert measured neutral abundances to compositional distributions of primary and trace species in the sputtered surfaces and atmospheres. The escaping neutrals can also be detected as ions after photo- or plasma-ionization and pickup. Higher energy, keV neutrals come from charge exchange of magnetospheric ions in the moon atmospheres and provide information on atmospheric structure. At the jovicentric orbits of the icy moons the presence of toroidal gas clouds, as detected at Europa's orbit, provide M e r opportunities to analyze both the composition of neutrals and ions originating from the moon surfaces, and the characteristics of magnetospheric ions interacting with neutral cloud material. Charge exchange of low energy ions near the moons, and

  7. Remote Sensing of Icy Galilean Moon Surface and Atmospheric Composition Using Low Energy (1 eV-4 keV) Neutral Atom Imaging

    NASA Technical Reports Server (NTRS)

    Collier, M. R.; Sittler, E.; Chornay, D.; Cooper, J. F.; Coplan, M.; Johnson, R. E.

    2004-01-01

    We describe a low energy neutral atom imager suitable for composition measurements Europa and other icy Galilean moons in the Jovian magnetosphere. This instrument employs conversion surface technology and is sensitive to either neutrals converted to negative ions, neutrals converted to positive ions and the positive ions themselves depending on the power supply. On a mission such as the Jupiter Icy Moons Orbiter (JIMO), two back-to-back sensors would be flown with separate power supplies fitted to the neutral atom and iodneutral atom sides. This will allow both remote imaging of 1 eV < E < 4 keV neutrals from icy moon surfaces and atmospheres, and in situ measurements of ions at similar energies in the moon ionospheres and Jovian magnetospheric plasma. The instrument provides composition measurements of the neutrals and ions that enter the spectrometer with a mass resolution dependent on the time-of-flight subsystem and capable of resolving molecules. The lower energy neutrals, up to tens of eV, arise from atoms and molecules sputtered off the moon surfaces and out of the moon atmospheres by impacts of more energetic (keV to MeV) ions from the magnetosphere. Direct Simulation Monte Carlo (DSMC) models are used to convert measured neutral abundances to compositional distributions of primary and trace species in the sputtered surfaces and atmospheres. The escaping neutrals can also be detected as ions after photo- or plasma-ionization and pickup. Higher energy, keV neutrals come from charge exchange of magnetospheric ions in the moon atmospheres and provide information on atmospheric structure. At the jovicentric orbits of the icy moons the presence of toroidal gas clouds, as detected at Europa's orbit, provide M e r opportunities to analyze both the composition of neutrals and ions originating from the moon surfaces, and the characteristics of magnetospheric ions interacting with neutral cloud material. Charge exchange of low energy ions near the moons, and

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

    NASA Astrophysics Data System (ADS)

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

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

  9. POD Analysis of a Wind Turbine Wake in a Turbulent Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Bastine, D.; Witha, B.; Wächter, M.; Peinke, J.

    2014-06-01

    The wake of a single wind turbine is modeled using an actuator disk model and large eddy simulations. As inflow condition a numerically generated turbulent atmospheric boundary layer is used. The proper orthogonal decomposition (POD) is applied to a plane perpendicular to the main flow in the far wake of the turbine. Reconstructions of the field are investigated depending on the numbers of POD modes used. Even though a great number of modes is needed to recover a great part of the turbulent kinetic energy, our results indicate that relevant aspects of a wake flow can be recovered using only a few modes. Particularly, the dynamics of the average velocity over a potential disk in the wake can partially be captured using only three modes.

  10. Modified shape of the Eiffel Tower determined for an atmospheric boundary-layer wind profile

    NASA Astrophysics Data System (ADS)

    Weidman, P. D.

    2009-06-01

    The design and construction of the Eiffel Tower was based, in part, on a uniform horizontal wind model giving 300 kg m-2 kinematic pressure acting on the surface of the tower. Eiffel received a patent for his method of construction that eliminates the need for diagonal trellis bars used to resist the moment of an oncoming wind. At the end of the 19th century boundary-layer theory, laminar or turbulent, was nonexistent. Now, however, models for atmospheric flow over rough landscapes are available, the simplest being a power-law distribution of velocity with height. In this paper we deduce the shape of the tower had Eiffel incorporated this information into the design and construction of his world famous tower. Moreover, we prove Eiffel's observation that the tower profile conforms to the moment distribution wrought by the wind.

  11. Spectral link for the mean velocity profile in the atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Zhang, Dongrong; Gioia, Gustavo; Chakraborty, Pinaki

    2016-11-01

    Turbulent flow in the atmospheric boundary layer is sheared and stratified. For this flow, we consider the mean velocity profile (MVP), the vertical profile of the time-averaged horizontal wind velocity. We employ the theoretical framework of the spectral link, originally proposed for MVP in sheared flows (Gioia et al., 2010) and later extended to stratified flows (Katul et al., 2011). Accounting for the whole structure of the turbulent energy spectrum-the energetic range, the inertial range, and the dissipative range-we examine the scaling of the MVP in the "wall coordinates" and in the Monin-Obukhov similarity coordinates, for both stable and unstable stratification. Our results are in excellent accord with field measurements and numerical simulations. Okinawa Institute of Science and Technology.

  12. Importance of the Western Oceanic Boundary Currents for the Northern Hemisphere Atmospheric Circulation

    NASA Astrophysics Data System (ADS)

    Omrani, Nour-Eddine; Ogawa, Fumiaki; Nakamura, Hisashi; Keenlyside, Noel; Lubis, Sandro; Matthes, Katja

    2017-04-01

    The importance of the extra-tropical Western Ocean Boundary Currents for the Northern Hemisphere (NH) Climate is assessed using a set of model experiments. Here we show that Sea Surface Temperature (SST)-fronts associated with Gulf Stream and Kuroshio-Oyashio Systems play significant role in maintaining the wintertime strong mid-latitude NH tropospheric Eddy-driven Jet and the weaker stratospheric polar night Jet. The strong tropospheric Eddy-driven Jet is maintained mainly by the enhanced lower tropospheric baroclinicty induced by oceanic front and associated baroclinic wave activities. The reduced stratospheric polar night jet is maintained mainly by upward planetary wave propagation induced by tropospheric circulation change. The implications of our results for the leading mode of NH variability, atmospheric energy balance and ozone depletion are also discussed.

  13. Single-column Model Intercomparison for a Stably Stratified Atmospheric Boundary Layer

    NASA Technical Reports Server (NTRS)

    Cuxart, J.; Holtslag, A. A. M.; Steeneveld, G-J; Beare, R. J.; Bazile, E.; Beljaars, A.; Cheng, A.; Conangla, L.; Ek, M.; Freedman, F.; hide

    2004-01-01

    The parameterization of the stably stratified atmospheric boundary layer is a difficult issue, which has a large impact on the medium-range weather forecasts and on climate integrations. A non-strongly stratified arctic case is simulated by nineteen single-column turbulence schemes. The statistics from the Large-eddy simulation (LES) intercomparison made for the same case by eight different models are used as a guiding reference. The single-column parameterizations include research schemes and operational schemes from major forecast and climate research centres. First order schemes, a large number of turbulence kinetic energy closures, and other proposals have submitted results. There is a large spread in the results; in general, the operational schemes mix more efficiently than the research ones, and the TKE and other higher order closures give results closer to the LES statistics. The sensitivities of the schemes to the parameters of their turbulence closures are partially explored.

  14. The influence of Nunataks on atmospheric boundary layer convection during summer in Dronning Maud Land, Antarctica

    NASA Astrophysics Data System (ADS)

    Stenmark, Aurora; Hole, Lars Robert; Voss, Paul; Reuder, Joachim; Jonassen, Marius O.

    2014-06-01

    The effects of nunataks on temperature profiles and wind patterns are studied using simulations from the Weather Research and Forecasting model. Simulations are compared to hourly observations from an automatic weather station located at the Troll Research Station in Dronning Maud Land. Areas of bare ground have been implemented in the model, and the simulations correspond well with meteorological measurements acquired during the 4 day simulation period. The nunataks are radiatively heated during daytime, and free convection occurs in the overlying atmospheric boundary layer. The inflow below the updraft forces strong horizontal convergence at the surface, whereas weaker divergence appears aloft. In a control run with a completely ice-covered surface, the convection is absent. In situ observations carried out by a remotely controlled balloon and a small model airplane compare well with model temperature profiles, but these are only available over the ice field upwind to the nunatak.

  15. Approximate Analytical Solution to Diurnal Atmospheric Boundary-Layer Growth Under Well-Watered Conditions

    NASA Astrophysics Data System (ADS)

    Rigby, J. R.; Yin, Jun; Albertson, John D.; Porporato, Amilcare

    2015-07-01

    Simplified numerical models of the atmospheric boundary layer (ABL) are useful both for understanding the underlying dynamics and potentially providing parsimonious modelling approaches for inclusion in larger models. Herein the governing equations of a simplified slab model of the uniformly mixed, purely convective, diurnal ABL are shown to allow immediate solutions for the potential temperature and specific humidity as functions of the ABL height and net radiation when expressed in integral form. By employing a linearized saturation vapour relation, the height of the mixed layer is shown to obey a non-linear ordinary differential equation with quadratic dependence on ABL height. A perturbation solution provides general analytical approximations, of which the leading term is shown to represent the contribution under equilibrium evaporation. These solutions allow the diurnal evolution of the height, potential temperature, and specific humidity (i.e., also vapour pressure deficit) of the mixed layer to be expressed analytically for arbitrary radiative forcing functions.

  16. On Lamb wave propagation from small surface explosions in the atmospheric boundary layer

    SciTech Connect

    ReVelle, D.O.; Kulichkov, S.N.

    1998-12-31

    The problem of Lamb waves propagation from small explosions in the atmospheric boundary layer are discussed. The results of lamb waves registrations from surface explosions with yields varied from 3 tons up to a few hundred tons (TNT equivalent) are presented. The source-receiver distances varied from 20 km up to 310 km. Most of the explosions were conducted during the evening and early morning hours when strong near-surface temperature and wind inversions existed. The corresponding profiles of effective sound velocity are presented. Some of the explosions had been realized with 15 minute intervals between them when morning inversion being destroyed. Corresponding transformation of Lamb waves was observed. The Korteveg-de Vrize equation to explain experimental data on Lamb waves propagation along earth surface is used.

  17. A stable and accurate scheme for nonlinear diffusion equations: Application to atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Nazari, Farshid; Mohammadian, Abdolmajid; Zadra, Ayrton; Charron, Martin

    2013-03-01

    Stability concerns are always a factor in the numerical solution of nonlinear diffusion equations, which are a class of equations widely applicable in different fields of science and engineering. In this study, a modified extended backward differentiation formulae (ME BDF) scheme is adapted for the solution of nonlinear diffusion equations, with a special focus on the atmospheric boundary layer diffusion process. The scheme is first implemented and examined for a widely used nonlinear ordinary differential equation, and then extended to a system of two nonlinear diffusion equations. A new temporal filter which leads to significant improvement of numerical results is proposed, and the impact of the filter on the stability and accuracy of the results is investigated. Noteworthy improvements are obtained as compared to other commonly used numerical schemes. Linear stability analysis of the proposed scheme is performed for both systems, and analytical stability limits are presented.

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

    NASA Astrophysics Data System (ADS)

    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. Single-column Model Intercomparison for a Stably Stratified Atmospheric Boundary Layer

    NASA Technical Reports Server (NTRS)

    Cuxart, J.; Holtslag, A. A. M.; Steeneveld, G-J; Beare, R. J.; Bazile, E.; Beljaars, A.; Cheng, A.; Conangla, L.; Ek, M.; Freedman, F.; Hamdi, R.

    2004-01-01

    The parameterization of the stably stratified atmospheric boundary layer is a difficult issue, which has a large impact on the medium-range weather forecasts and on climate integrations. A non-strongly stratified arctic case is simulated by nineteen single-column turbulence schemes. The statistics from the Large-eddy simulation (LES) intercomparison made for the same case by eight different models are used as a guiding reference. The single-column parameterizations include research schemes and operational schemes from major forecast and climate research centres. First order schemes, a large number of turbulence kinetic energy closures, and other proposals have submitted results. There is a large spread in the results; in general, the operational schemes mix more efficiently than the research ones, and the TKE and other higher order closures give results closer to the LES statistics. The sensitivities of the schemes to the parameters of their turbulence closures are partially explored.

  20. Generation of atmospheric boundary layer in the IIUM low speed wind tunnel

    NASA Astrophysics Data System (ADS)

    Za'aba, Khalid Aldin Bin; Asrar, Waqar; Dheeb, Mohamad Al

    2017-03-01

    The purpose of this paper is to describe an attempt made to simulate the atmospheric boundary layer (ABL) in the Low Speed Wind Tunnel (LSWT) at IIUM. This was performed through modifications of the inlet and surface conditions of the test section. Devices such as spires, fences and surface roughness were used. The ASCE 7-10 standard was used as a reference to validate the results between the wind tunnel data and the full-scale ABL flow characteristics. The velocity profile and turbulence intensity were measured using a one-dimensional hotwire (CTA) probe. The data obtained show good agreement with ASCE 7-10 velocity profiles for exposures B and C while using a scale of 1:488 to match the wind tunnel data. The turbulence intensity profiles do not show a good agreement.

  1. Linking NO2 surface concentration and integrated content in the urban developed atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Dieudonné, E.; Ravetta, F.; Pelon, J.; Goutail, F.; Pommereau, J.-P.

    2013-03-01

    A statistical linear relationship between NO2 surface concentration and its integrated content in the atmospheric boundary layer (ABL) is established in urban conditions, using ABL depth as an ancillary parameter. This relationship relies on a unique data set including 20 months of observations from a ground-based UV-visible light spectrometer and from an aerosol lidar, both located in Paris inner city center. Measurements show that in all seasons, large vertical gradients of NO2 concentration exist in Paris developed ABL, explaining why the average concentration retrieved is only about 25% of NO2 surface concentration. This result shows that the commonly used hypothesis of constant mixing ratio in the ABL is not valid over urban areas, where large NOx emissions occur. Moreover, the relationship obtained is robust, and the studied area lacks of any particular orographic features, so that our results should be more widely applicable to pollution survey from space-borne observations.

  2. WRF simulations of the atmospheric boundary layer evening transitions during the BLLAST field campaign

    NASA Astrophysics Data System (ADS)

    Sastre Marugán, Mariano; Steeneveld, Gert-Jan; Yagüe, Carlos; Román-Cascón, Carlos; Maqueda, Gregorio; van de Boer, Anneke

    2013-04-01

    The Planetary Boundary Layer (PBL) is mainly ruled by both mechanical and thermal turbulence, and shows an evident diurnal cycle. In the evening transitional period, decay in turbulent kinetic energy occurs, but all the mechanisms behind this decay are still not well understood. In this framework, the BLLAST (Boundary Layer Late Afternoon and Sunset Turbulence) project aims to improve the knowledge on the physical processes taking place during the late afternoon and evening transition in the lower troposphere. The BLLAST field campaign was organized in Lannemezan (France) from 14th June to 8th July 2011 [1]. Both in situ measurements (i.e., with meteorological towers, surface based instruments, tethered balloons…) and remote sensors (i.e., SODAR, scintillometer…) were used for this purpose, and two different approaches were developed: vertical structure of the boundary layer and spatial heterogeneity. Besides, Numerical Weather Prediction (NWP) models have exhibited substantial difficulties to properly simulate the diurnal cycle in the atmosphere and also the PBL afternoon and evening transition. Typically, some errors are found in air temperature and wind speed close to the surface. Regarding this fact, the main goal of this work is to study how the mesoscale model WRF (Weather Research and Forecast) performs simulations of the evening transition during the BLLAST field campaign. In particular, it is tested for permutations of different PBL and Land Surface Model (LSM) schemes. We try to understand why some differences in model results appear. A comparison between observations and combinations of PBL and LSM parameterizations is shown, testing the sensitivity to these options. We specifically evaluate the surface radiation budget (out- and incoming long- and shortwave radiation), and the surface energy budget variables (latent and sensible heat fluxes, as well as soil heat flux). Furthermore, the vertical profiles of some key variables (such as potential

  3. Large eddy simulations and reduced models of the Unsteady Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Momen, M.; Bou-Zeid, E.

    2013-12-01

    Most studies of the dynamics of Atmospheric Boundary Layers (ABLs) have focused on steady geostrophic conditions, such as the classic Ekman boundary layer problem. However, real-world ABLs are driven by a time-dependent geostrophic forcing that changes at sub-diurnal scales. Hence, to advance our understanding of the dynamics of atmospheric flows, and to improve their modeling, the unsteady cases have to be analyzed and understood. This is particularly relevant to new applications related to wind energy (e.g. short-term forecast of wind power changes) and pollutant dispersion (forecasting of rapid changes in wind velocity and direction after an accidental spill), as well as to classic weather prediction and hydrometeorological applications. The present study aims to investigate the ABL behavior under variable forcing and to derive a simple model to predict the ABL response under these forcing fluctuations. Simplifications of the governing Navier-Stokes equations, with the Coriolis force, are tested using LES and then applied to derive a physical model of the unsteady ABL. LES is then exploited again to validate the analogy and the output of the simpler model. Results from the analytical model, as well as LES outputs, open the way for inertial oscillations to play an important role in the dynamics. Several simulations with different variable forcing patterns are then conducted to investigate some of the characteristics of the unsteady ABL such as resonant frequency, ABL response time, equilibrium states, etc. The variability of wind velocity profiles and hodographs, turbulent kinetic energy, and vertical profiles of the total stress and potential temperature are also examined. Wind Hodograph of the Unsteady ABL at Different Heights - This figure shows fluctuations in the mean u and v components of the velocity as time passes due to variable geostrophic forcing

  4. Neutral Wind Determination from SuperDARN Backscatter: Technique and Application to the Study of Atmospheric Waves and Tides

    NASA Astrophysics Data System (ADS)

    McCubbin, Elizabeth Ann

    The Super Dual Auroral Radar Network (SuperDARN) is a network of high-frequency (HF) radars designed to detect the horizontal motion of plasma drifting in the ionosphere over the Earth's mid- to high-latitude regions. These radars are also sensitive to ionization trails caused by meteors ablating in the upper atmosphere at mesosphere altitudes (85-100 km). Since the ionized meteor trails drift with the neutral atmosphere at these altitudes, they serve as a tracer for studying the dynamics of atmospheric waves. To analyze the background mean wind flow and atmospheric waves, a more reliable technique was developed for identifying meteor echoes from the variety of signals detected by these radars. Applying this technique to data obtained from several mid-latitude radars in 2011 reveals a diurnal and seasonal dependence of the occurrence of meteor echoes. In addition there is a dependence on the orientation between the radar viewing direction and the background wind direction. Further analysis identifies bursts of wave activity throughout the year, showing interesting results from a particular source known as the quasi-two-day wave (QTDW). It is shown that the variability in the amplitude of the QTDW maximizes near particular longitudes across North America. Furthermore, a detailed study of non-linear interactions between the QTDW and multiple wave periods is performed. A technique known as bispectral analysis, a third-order statistical method that identifies phase coupling between harmonic frequencies and secondary waves, is used to confirm that nonlinear wave interactions exist with the QTDW, as suggested by the power spectrum. This research provides a more reliable method for identifying meteor echoes from SuperDARN measurements and furthers our understanding of atmospheric dynamics in the mesosphere.

  5. Direct and large-eddy simulations of the stable atmospheric boundary layer: the effect of unsteadiness and surface variability

    NASA Astrophysics Data System (ADS)

    Shah, S.; Bou-Zeid, E.

    2013-12-01

    Understanding and parameterizing turbulent fluxes in statically-stable atmospheric boundary layers (SABLs), where buoyant forces destroy turbulent kinetic energy, remains a challenging yet very important problem in geophysical fluid dynamics. The complexities of these flows are further exacerbated by the increased sensitivity to unsteadiness and surface variability. To address the role of these exacerbating factors, direct numerical simulations and large eddy simulations are performed. Under the highest stabilities, global intermittency (the almost compete decay of turbulence and then its regeneration) is observed. The intermittent bursts are important to study under these conditions since they become the main agent of vertical transport in the SABL. Under more moderate stabilities, continuous turbulence is maintained, but it is significantly damped compared to neutral flows. This reduction of the TKE under stable conditions is very well known; however, in this study, we show that it is mainly triggered by reduced mechanical production associated with reduced transport of Reynolds stresses from aloft toward the surface, rather than by direct destruction of TKE by buoyancy. Variability of surface temperature is shown to result in excepted flow patterns: TKE is potentially higher under the more stable patches due to advection, and the subsidence and lofting of air over the different patches can counteract the effect of spatial TKE variability on the vertical fluxes. Re_f = 600. (a) Surface Richardson number (R_{i0;t}) versus non-dimensional time (tf) for different stabilities. (b) Non-dimensional volume integrated turbulent kinetic energy per unit area (E). (c) Friction velocity (u_*) and its variation with time and stability. (d) Variation of the angle (Beta) between the geostrophic wind direction and the surface shear stress direction with time and stability. Colormap of the TKE from a heterogeneous surface temperature LES, showing the effect of advection.

  6. Deviations from Equilibrium in Daytime Atmospheric Boundary Layer Turbulence arising from Nonstationary Mesoscale Forcing

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

    LES of the "canonical" daytime atmospheric boundary layer (ABL) over flat topography is developed as an equilibrium ABL with steady surface heat flux, Q0 and steady unidirectional "geostrophic" wind vector Vg above a capping inversion. A strong inversion layer in daytime ABL acts as a "lid" that sharply separates 3D "microscale" ABL turbulence at the O(10) m scale from the quasi-2D "mesoscale" turbulent weather eddies (O(100) km scale). While "canonical" ABL is equilibrium, quasi-stationary and characterized statistically by the ratio of boundary layer depth (zi) to Obukhov length scale (- L) , the real mesoscale influences (Ug and Q0) that force a true daytime ABL are nonstationary at both diurnal and sub-diurnal time scales. We study the consequences of this non-stationarity on ABL dynamics by forcing ABL LES with realistic WRF simulations over flat Kansas terrain. Considering horizontal homogeneity, we relate the mesoscale and geostrophic winds, Ug and Vg, and systematically study the ABL turbulence response to non-steady variations in Q0 and Ug. We observe significant deviations from equilibrium, that manifest in many ways, such as the formation of "roll" eddies purely from changes in mesoscale wind direction that are normally associated with increased surface heat flux. Support from DOE. Compute resources from Penn State ICS.

  7. Analytical Reduced Models for the Non-stationary Diabatic Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Momen, Mostafa; Bou-Zeid, Elie

    2017-09-01

    Geophysical boundary-layer flows feature complex dynamics that often evolve with time; however, most current knowledge centres on the steady-state problem. In these atmospheric and oceanic boundary layers, the pressure gradient, buoyancy, Coriolis, and frictional forces interact to determine the statistical moments of the flow. The resulting equations for the non-stationary mean variables, even when succinctly closed, remain challenging to handle mathematically. Here, we derive a simpler physical model that reduces these governing unsteady Reynolds-averaged Navier-Stokes partial differential equations into a single first-order ordinary differential equation with non-constant coefficients. The reduced model is straightforward to solve under arbitrary forcing, even when the statistical moments are non-stationary and the viscosity varies in time and space. The model is successfully validated against large-eddy simulation for, (1) time-variable pressure gradients, and (2) linearly time-variable buoyancy. The new model is shown to have a superior performance compared to the classic Blackadar solutions (and later improvements on these solutions), and it covers a much wider range of conditions.

  8. Influence of Evaporating Droplets in the Turbulent Marine Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Peng, Tianze; Richter, David

    2017-08-01

    Sea-spray droplets ejected into the marine atmospheric boundary layer take part in a series of complex transport processes. By capturing the air-droplet coupling and feedback, we focus on how droplets modify the total heat transfer across a turbulent boundary layer. We implement a high-resolution Eulerian-Lagrangian algorithm with varied droplet size and mass loading in a turbulent open-channel flow, revealing that the influence from evaporating droplets varies for different dynamic and thermodynamic characteristics of droplets. Droplets that both respond rapidly to the ambient environment and have long suspension times are able to modify the latent and sensible heat fluxes individually, however the competing signs of this modification lead to an overall weak effect on the total heat flux. On the other hand, droplets with a slower thermodynamic response to the environment are less subjected to this compensating effect. This indicates a potential to enhance the total heat flux, but the enhancement is highly dependent on the concentration and suspension time.

  9. Improved Atmospheric Boundary Layer Observations of Tropical Cyclones with the Imaging Wind and Rain Airborne Profiler

    NASA Technical Reports Server (NTRS)

    Fernandez, D. Esteban; Chang, P.; Carswel, J.; Contreras, R.; Chu, T.; Asuzu, P.; Black, P.; Marks, F.

    2006-01-01

    The Imaging Wind and Rain Arborne Profilers (IWRAP) is a dual-frequency, conically-scanning Doppler radar that measures high-resolution, dual-polarized, multi-beam C- and Ku-band reflectivity and Doppler velocity profiles of the atmospheric boundary layer (ABL) within the inner core of hurricanes.From the datasets acquired during the 2002 through 20O5 hurricane seasons as part of the ONR Coupled Boundary Layer Air-Sea Transfer (CBLAST) program and the NOAA/NESDIS Ocean Winds and Rain experiments, very high resolution radar observations of hurricanes have been acquired and made available to the CBLAST community. Of particular interest am the ABL wind fields and 3-D structures found within the inner core of hurricanes. As a result of these analysis, a limitation in the ability to retrieve the ABL wind field at very low altitudes was identified. This paper shows how this limitation has been removed and presents initial results demonstrating its new capabilities to derive the ABL wind field within the inner are of hurricanes to much lower altitudes than the ones the original system was capable of.

  10. The relative importance of ejections and sweeps to momentum transfer in the atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Katul, Gabriel; Poggi, Davide; Cava, Daniela; Finnigan, John

    2006-09-01

    Using an incomplete third-order cumulant expansion method (ICEM) and standard second-order closure principles, we show that the imbalance in the stress contribution of sweeps and ejections to momentum transfer (Δ S o ) can be predicted from measured profiles of the Reynolds stress and the longitudinal velocity standard deviation for different boundary-layer regions. The ICEM approximation is independently verified using flume data, atmospheric surface layer measurements above grass and ice-sheet surfaces, and within the canopy sublayer of maturing Loblolly pine and alpine hardwood forests. The model skill for discriminating whether sweeps or ejections dominate momentum transfer (e.g. the sign of Δ S o ) agrees well with wind-tunnel measurements in the outer and surface layers, and flume measurements within the canopy sublayer for both sparse and dense vegetation. The broader impact of this work is that the “genesis” of the imbalance in Δ S o is primarily governed by how boundary conditions impact first and second moments.

  11. Atmospheric Boundary Layer Sensors for Application in a Wake Vortex Advisory System

    NASA Technical Reports Server (NTRS)

    Zak, J. Allen; Rutishauser, David (Technical Monitor)

    2003-01-01

    Remote sensing of the atmospheric boundary layer has advanced in recent years with the development of commercial off-the-shelf (COTS) radar, sodar, and lidar wind profiling technology. Radio acoustic sounding systems for vertical temperature profiles of high temporal scales (when compared to routine balloon soundings- (radiosondes) have also become increasingly available as COTS capabilities. Aircraft observations during landing and departures are another source of available boundary layer data. This report provides an updated assessment of available sensors, their performance specifications and rough order of magnitude costs for a potential future aircraft Wake Vortex Avoidance System (WakeVAS). Future capabilities are also discussed. Vertical profiles of wind, temperature, and turbulence are anticipated to be needed at airports in any dynamic wake avoidance system. Temporal and spatial resolution are dependent on the selection of approach and departure corridors to be protected. Recommendations are made for potential configurations of near-term sensor technologies and for testing some of the sensor systems in order to validate performance in field environments with adequate groundtruth.

  12. Analytical Reduced Models for the Non-stationary Diabatic Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Momen, Mostafa; Bou-Zeid, Elie

    2017-04-01

    Geophysical boundary-layer flows feature complex dynamics that often evolve with time; however, most current knowledge centres on the steady-state problem. In these atmospheric and oceanic boundary layers, the pressure gradient, buoyancy, Coriolis, and frictional forces interact to determine the statistical moments of the flow. The resulting equations for the non-stationary mean variables, even when succinctly closed, remain challenging to handle mathematically. Here, we derive a simpler physical model that reduces these governing unsteady Reynolds-averaged Navier-Stokes partial differential equations into a single first-order ordinary differential equation with non-constant coefficients. The reduced model is straightforward to solve under arbitrary forcing, even when the statistical moments are non-stationary and the viscosity varies in time and space. The model is successfully validated against large-eddy simulation for, (1) time-variable pressure gradients, and (2) linearly time-variable buoyancy. The new model is shown to have a superior performance compared to the classic Blackadar solutions (and later improvements on these solutions), and it covers a much wider range of conditions.

  13. Observations and Modelling of the Atmospheric Boundary Layer Over Sea-Ice in a Svalbard Fjord

    NASA Astrophysics Data System (ADS)

    Mäkiranta, Eeva; Vihma, Timo; Sjöblom, Anna; Tastula, Esa-Matti

    2011-07-01

    Sonic anemometer and profile mast measurements made in Wahlenbergfjorden, Svalbard Arctic archipelago, in May 2006 and April 2007 were employed to study the atmospheric boundary layer over sea-ice. The turbulent surface fluxes of momentum and sensible heat were calculated using eddy correlation and gradient methods. The results showed that the literature-based universal functions underestimated turbulent mixing in strongly stable conditions. The validity of the Monin-Obukhov similarity theory was questionable for cross-fjord flow directions and in the presence of mesoscale variability or topographic effects. The aerodynamic roughness length showed a dependence on the wind direction. The mean roughness length for along-fjord wind directions was (2.4 ± 2.6) × 10-4 m, whereas that for cross-fjord directions was (5.4 ± 2.8) × 10-3 m. The thermal stratification and turbulent fluxes were affected by the synoptic situation with large differences between the 2 years. Channelling effects and drainage flows occurred especially during a weak large-scale flow. The study periods were simulated applying the Weather Research and Forecasting (WRF) model with 1-km horizontal resolution in the finest domain. The results for the 2-m air temperature and friction velocity were good, but the model failed to reproduce the spatial variability in wind direction between measurement sites 3 km apart. The model suggested that wind shear above the stable boundary layer provided a non-local source for the turbulence observed.

  14. Western boundary currents regulated by interaction between ocean eddies and the atmosphere.

    PubMed

    Ma, Xiaohui; Jing, Zhao; Chang, Ping; Liu, Xue; Montuoro, Raffaele; Small, R Justin; Bryan, Frank O; Greatbatch, Richard J; Brandt, Peter; Wu, Dexing; Lin, Xiaopei; Wu, Lixin

    2016-07-28

    Current climate models systematically underestimate the strength of oceanic fronts associated with strong western boundary currents, such as the Kuroshio and Gulf Stream Extensions, and have difficulty simulating their positions at the mid-latitude ocean's western boundaries. Even with an enhanced grid resolution to resolve ocean mesoscale eddies-energetic circulations with horizontal scales of about a hundred kilometres that strongly interact with the fronts and currents-the bias problem can still persist; to improve climate models we need a better understanding of the dynamics governing these oceanic frontal regimes. Yet prevailing theories about the western boundary fronts are based on ocean internal dynamics without taking into consideration the intense air-sea feedbacks in these oceanic frontal regions. Here, by focusing on the Kuroshio Extension Jet east of Japan as the direct continuation of the Kuroshio, we show that feedback between ocean mesoscale eddies and the atmosphere (OME-A) is fundamental to the dynamics and control of these energetic currents. Suppressing OME-A feedback in eddy-resolving coupled climate model simulations results in a 20-40 per cent weakening in the Kuroshio Extension Jet. This is because OME-A feedback dominates eddy potential energy destruction, which dissipates more than 70 per cent of the eddy potential energy extracted from the Kuroshio Extension Jet. The absence of OME-A feedback inevitably leads to a reduction in eddy potential energy production in order to balance the energy budget, which results in a weakened mean current. The finding has important implications for improving climate models' representation of major oceanic fronts, which are essential components in the simulation and prediction of extratropical storms and other extreme events, as well as in the projection of the effect on these events of climate change.

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

    NASA Astrophysics Data System (ADS)

    Wildmann, Norman; Bange, Jens

    2014-05-01

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

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

    NASA Astrophysics Data System (ADS)

    Wildmann, Norman; Platis, Andreas; Tupman, David-James; Bange, Jens

    2015-04-01

    The remotely piloted aircraft (RPA) MASC (Multipurpose Airborne Sensor Carrier) was developed at the University of Tübingen in cooperation with the University of Stuttgart, University of Applied Sciences Ostwestfalen-Lippe and 'ROKE-Modelle'. Its purpose is the investigation of thermodynamic processes in the atmospheric boundary layer (ABL), including observations of temperature, humidity and wind profiles, as well as the measurement of turbulent heat, moisture and momentum fluxes. The aircraft is electrically powered, has a maximum wingspan of 3.40~m and a total weight of 5-8~kg, depending on the battery- and payload. The standard meteorological payload consists of two temperature sensors, a humidity sensor, a flow probe, an inertial measurement unit and a GNSS. The sensors were optimized for the resolution of small-scale turbulence down to length scales in the sub-meter range. In normal operation, the aircraft is automatically controlled by the ROCS (Research Onboard Computer System) autopilot to be able to fly predefined paths at constant altitude and airspeed. Only take-off and landing are carried out by a human RC pilot. Since 2012, the system is operational and has since then been deployed in more than ten measurement campaigns, with more than 100 measurement flights. The fields of research that were tackled in these campaigns include sensor validation, fundamental boundary-layer research and wind-energy research. In 2014, for the first time, two MASC have been operated at the same time within a distance of a few kilometres, in order to investigate the wind field over an escarpment in the Swabian Alb. Furthermore, MASC was first deployed off-shore in October 2014, starting from the German island Heligoland in the North Sea, for the purpose of characterization of the marine boundary layer for offshore wind parks. Detailed descriptions of the experimental setup and first preliminary results will be presented.

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

    NASA Astrophysics Data System (ADS)

    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. Perturbations to the Spatial and Temporal Characteristics of the Diurnally-Varying Atmospheric Boundary Layer Due to an Extensive Wind Farm

    NASA Astrophysics Data System (ADS)

    Sharma, V.; Parlange, M. B.; Calaf, M.

    2017-02-01

    The effect of extensive terrestrial wind farms on the spatio-temporal structure of the diurnally-evolving atmospheric boundary layer is explored. High-resolution large-eddy simulations of a realistic diurnal cycle with an embedded wind farm are performed. Simulations are forced by a constant geostrophic velocity with time-varying surface boundary conditions derived from a selected period of the CASES-99 field campaign. Through analysis of the bulk statistics of the flow as a function of height and time, it is shown that extensive wind farms shift the inertial oscillations and the associated nocturnal low-level jet vertically upwards by approximately 200 m; cause a three times stronger stratification between the surface and the rotor-disk region, and as a consequence, delay the formation and growth of the convective boundary layer (CBL) by approximately 2 h. These perturbations are shown to have a direct impact on the potential power output of an extensive wind farm with the displacement of the low-level jet causing lower power output during the night as compared to the day. The low-power regime at night is shown to persist for almost 2 h beyond the morning transition due to the reduced growth of the CBL. It is shown that the wind farm induces a deeper entrainment region with greater entrainment fluxes. Finally, it is found that the diurnally-averaged effective roughness length for wind farms is much lower than the reference value computed theoretically for neutral conditions.

  19. Perturbations to the Spatial and Temporal Characteristics of the Diurnally-Varying Atmospheric Boundary Layer Due to an Extensive Wind Farm

    NASA Astrophysics Data System (ADS)

    Sharma, V.; Parlange, M. B.; Calaf, M.

    2016-08-01

    The effect of extensive terrestrial wind farms on the spatio-temporal structure of the diurnally-evolving atmospheric boundary layer is explored. High-resolution large-eddy simulations of a realistic diurnal cycle with an embedded wind farm are performed. Simulations are forced by a constant geostrophic velocity with time-varying surface boundary conditions derived from a selected period of the CASES-99 field campaign. Through analysis of the bulk statistics of the flow as a function of height and time, it is shown that extensive wind farms shift the inertial oscillations and the associated nocturnal low-level jet vertically upwards by approximately 200 m; cause a three times stronger stratification between the surface and the rotor-disk region, and as a consequence, delay the formation and growth of the convective boundary layer (CBL) by approximately 2 h. These perturbations are shown to have a direct impact on the potential power output of an extensive wind farm with the displacement of the low-level jet causing lower power output during the night as compared to the day. The low-power regime at night is shown to persist for almost 2 h beyond the morning transition due to the reduced growth of the CBL. It is shown that the wind farm induces a deeper entrainment region with greater entrainment fluxes. Finally, it is found that the diurnally-averaged effective roughness length for wind farms is much lower than the reference value computed theoretically for neutral conditions.

  20. Atmospheric concentrations and gas/particle partitioning of neutral poly- and perfluoroalkyl substances in northern German coast

    NASA Astrophysics Data System (ADS)

    Wang, Zhen; Xie, Zhiyong; Möller, Axel; Mi, Wenying; Wolschke, Hendrik; Ebinghaus, Ralf

    2014-10-01

    Total 58 high volume air samples were collected in Büsum, Germany, from August 2011 to October 2012 to investigate air concentrations of 12 per- and polyfluoroalkyl substances (PFASs) and their gas/particle partitioning. The total concentration (vapor plus particle phases) of the 12 PFASs (ΣPFASs) ranged from 8.6 to 155 pg/m3 (mean: 41 pg/m3) while fluorotelomer alcohols 8:2 (8:2 FTOH) dominated all samples accounting for 61.9% of ΣPFASs and the next most species were 10:2 FTOH (12.7%). Air mass back trajectory analysis showed that atmospheric PFASs in most samples were from long range atmospheric transport processes and had higher ratios of 8:2 to 6:2 FTOH compared to the data obtained from urban/industrial sources. Small portion of particle PFASs in the atmosphere was observed and the average percent to ΣPFASs was 2.0%. The particle-associated fractions of different PFASs decreased from perfluorooctane sulfonamidoethanols (FOSEs) (15.5%) to fluorotelomer acrylates (FTAs) (7.6%) to perfluorooctane sulfonamides (FOSAs) (3.1%) and FTOHs (1.8%), indicating the functional group obviously influenced their gas/particle partitioning. For neutral compounds with acid dissociation constant (pKa) > 7.0 (i.e., FTOHs, FOSEs and FOSAs), a significant log-linear relationship was observed between their gas/particle partition coefficients (KSP) and vapor pressures (pºL), suggesting the gas/particle partitioning of neutral PFASs agreed with the classical logKSP-logpºL relation. Due to the pKa values of 6:2 and 8:2 FTA below the typical environmental pH conditions, they mainly exist as ionic form in aerosols, and the corrected logKSP (neutral form) were considerably lower than those of FTOHs, FOSEs and FOSAs with similar vapor pressures. Considering the strong partitioning potential to aqueous phases for ionic PFASs at higher pH values, a need exists to develop a model taking account of the ad/absorption mechanism to the condensed phase of aerosols for ionizable PFASs (e

  1. Research study on neutral thermodynamic atmospheric model. [for space shuttle mission and abort trajectory

    NASA Technical Reports Server (NTRS)

    Hargraves, W. R.; Delulio, E. B.; Justus, C. G.

    1977-01-01

    The Global Reference Atmospheric Model is used along with the revised perturbation statistics to evaluate and computer graph various atmospheric statistics along a space shuttle reference mission and abort trajectory. The trajectory plots are height vs. ground range, with height from ground level to 155 km and ground range along the reentry trajectory. Cross sectional plots, height vs. latitude or longitude, are also generated for 80 deg longitude, with heights from 30 km to 90 km and latitude from -90 deg to +90 deg, and for 45 deg latitude, with heights from 30 km to 90 km and longitudes from 180 deg E to 180 deg W. The variables plotted are monthly average pressure, density, temperature, wind components, and wind speed and standard deviations and 99th inter-percentile range for each of these variables.

  2. The Role of Neutral Atmospheric Dynamics in Cusp Density - 2nd Campaign

    DTIC Science & Technology

    2013-12-30

    first case study from January 2012. Two Fabry-Perot interferometers measured the non-ionized component of the upper atmosphere, and independent...mechanism proposed by Carlson et al in 2012 which proposed that depositing energy at high altitudes would require less energy to lift a shorter column of air...results from the first campaign appear to confirm the Carlson et al mechanism, while findings from the second campaign (this grant) confirm that it is

  3. Stability and Turbulence in the Atmospheric Boundary Layer: A Comparison of Remote Sensing and Tower Observations

    SciTech Connect

    Friedrich, K.; Lundquist, J. K.; Aitken, M.; Kalina, E. A.; Marshall, R. F.

    2012-01-01

    When monitoring winds and atmospheric stability for wind energy applications, remote sensing instruments present some advantages to in-situ instrumentation such as larger vertical extent, in some cases easy installation and maintenance, measurements of vertical humidity profiles throughout the boundary layer, and no restrictions on prevailing wind directions. In this study, we compare remote sensing devices, Windcube lidar and microwave radiometer, to meteorological in-situ tower measurements to demonstrate the accuracy of these measurements and to assess the utility of the remote sensing instruments in overcoming tower limitations. We compare temperature and wind observations, as well as calculations of Brunt-Vaisala frequency and Richardson numbers for the instrument deployment period in May-June 2011 at the U.S. Department of Energy National Renewable Energy Laboratory's National Wind Technology Center near Boulder, Colorado. The study reveals that a lidar and radiometer measure wind and temperature with the same accuracy as tower instruments, while also providing advantages for monitoring stability and turbulence. We demonstrate that the atmospheric stability is determined more accurately when the liquid-water mixing ratio derived from the vertical humidity profile is considered under moist-adiabatic conditions.

  4. Acoustic pulse propagation through a fluctuating stably stratified atmospheric boundary layer.

    PubMed

    Chunchuzov, Igor; Kulichkov, Sergey; Otrezov, Alexander; Perepelkin, Vitaly

    2005-04-01

    Mesoscale wind speed and temperature fluctuations with periods from 1 min to a few hours significantly affect temporal variability and turbulent regime of the stable atmospheric boundary layer (ABL). Their statistical characteristics are still poorly understood, although the knowledge of such statistics is required when modeling sound propagation through the stable ABL. Several field experiments have been conducted to study the influence of mesoscale wind speed fluctuations on acoustic pulse propagation through the stable ABL. Some results of these experiments are described in this paper. A special acoustic source was used to generate acoustic pulses by the detonation of an air-propane mixture with a repetition period 30 s. The mean wind speed and temperature profiles were continuously measured by Doppler sodar and temperature profiler, whereas mesoscale wind fluctuations were measured by anemometers placed on a 56-m mast. From the measurements of the pulse travel time fluctuations at different distances from the source, the statistical characteristics of the mesoscale wind fluctuations, such as frequency spectra, coherences, horizontal phase speeds and scales, have been obtained. Some of the obtained results are interpreted with the use of a recently developed model for the internal wave spectrum in a stably stratified atmosphere.

  5. Correlation between Atmospheric Boundary Layer Height and Polybrominated Diphenyl Ether Concentrations in Air.

    PubMed

    Dien, Nguyen Thanh; Hirai, Yasuhiro; Sakai, Shin-Ichi

    2017-01-03

    In this study, we aim to determine the correlation between the height of the atmospheric boundary layer (ABL) and the concentrations of polybrominated diphenyl ether (PBDE) congeners, in an effort to improve comprehension of the atmospheric behavior of PBDEs. We used the PBDE data in air (n = 298), which were measured by the Japan Ministry of Environment (JMOE) at 50 sites across Japan during the period 2009-2012. The height of the ABL, which directly affects the PBDE concentrations in the near-surface air, was estimated by employing data retrieved from the Japanese global reanalysis (JRA-55) database, using the parcel and Richardson number method. The ABL has shown a strong inverse relationship with BDE-47 and BDE-99 (p < 0.01). In contrast, there was less correlation between BDE-209 and the ABL (p = 0.258). These differing behaviors could be explained by differences in particle size distribution of PBDEs, where BDE-47 and BDE-99 are associated with gas phases and fine particles and BDE-209 is associated with coarse particles. To our knowledge, this paper represents the first large-scale analysis of correlations between the ABL and the concentrations of PBDEs in the air.

  6. Internal gravity-shear waves in the atmospheric boundary layer from acoustic remote sensing data

    NASA Astrophysics Data System (ADS)

    Lyulyukin, V. S.; Kallistratova, M. A.; Kouznetsov, R. D.; Kuznetsov, D. D.; Chunchuzov, I. P.; Chirokova, G. Yu.

    2015-03-01

    The year-round continuous remote sounding of the atmospheric boundary layer (ABL) by means of the Doppler acoustic radar (sodar) LATAN-3 has been performed at the Zvenigorod Scientific Station of the Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, since 2008. A visual analysis of sodar echograms for four years revealed a large number of wavelike patterns in the intensity field of a scattered sound signal. Similar patterns were occasionally identified before in sodar, radar, and lidar sounding data. These patterns in the form of quasi-periodic inclined stripes, or cat's eyes, arise under stable stratification and significant vertical wind shears and result from the loss of the dynamic stability of the flow. In the foreign literature, these patterns, which we call internal gravity-shear waves, are often associated with Kelvin-Helmholtz waves. In the present paper, sodar echograms are classified according to the presence or absence of wavelike patterns, and a statistical analysis of the frequency of their occurrence by the year and season was performed. A relationship between the occurrence of the patterns and wind shear and between the wave length and amplitude was investigated. The criteria for the identification of gravity-shear waves, meteorological conditions of their excitation, and issues related to their observations were discussed.

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

    NASA Astrophysics Data System (ADS)

    Sun, Jielun; Nappo, Carmen J.; Mahrt, Larry; Belušić, Danijel; Grisogono, Branko; Stauffer, David R.; Pulido, Manuel; Staquet, Chantal; Jiang, Qingfang; Pouquet, Annick; Yagüe, Carlos; Galperin, Boris; Smith, Ronald B.; Finnigan, John J.; Mayor, Shane D.; Svensson, Gunilla; Grachev, Andrey A.; Neff, William D.

    2015-09-01

    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 surfaces, or even daytime over snow and ice surfaces, and when warm air is advected over cold surfaces. Intermittent turbulence intensification in the SABL impacts human activities and weather variability, yet it cannot be generated in state-of-the-art numerical forecast models. This failure is mainly due to a lack of understanding of the physical mechanisms for seemingly random turbulence generation in a stably stratified flow, in which wave-turbulence interaction is a potential mechanism for turbulence intermittency. A workshop on wave-turbulence interactions in the SABL addressed the current understanding and challenges of wave-turbulence interactions and the role of wavelike motions in contributing to anisotropic and intermittent turbulence from the perspectives of theory, observations, and numerical parameterization. There have been a number of reviews on waves, and a few on turbulence in stably stratified flows, but not much on wave-turbulence interactions. This review focuses on the nocturnal SABL; however, the discussions here on intermittent turbulence and wave-turbulence interactions in stably stratified flows underscore important issues in stably stratified geophysical dynamics in general.

  8. Application of transilient turbulent theory to study interactions between the atmospheric boundary layer and forest canopies

    NASA Astrophysics Data System (ADS)

    Inclán, M. G.; Forkel, R.; Dlugi, R.; Stull, R. B.

    1996-06-01

    The new Forest-Land-Atmosphere ModEl called FLAME is presented. The first-order, nonlocal turbulence closure called transilient turbulence theory (Stull, 1993) is applied to study the interactions between a forested land-surface and the atmospheric boundary layer (ABL). The transilient scheme is used for unequal vertical grid spacing and includes the effects of drag, wake turbulence, and interference to vertical mixing by plant elements. Radiation transfer within the vegetation and the equations for the energy balance at the leaf surface have been taken from Norman (1979). Among others, the model predicts profiles of air temperature, humidity and wind velocity within the ABL, sensible and latent heat fluxes from the soil and the vegetation, the stomata and aerodynamic resistances, as well as profiles of temperature and water content in the soil. Preliminary studies carried out for a cloud free day and idealized initial conditions are presented. The canopy height is 30 m within a vertical domain of 3 km. The model is able to capture some of the effects usually observed within and above forested areas, including the relative wind speed maximum in the trunk space and the counter gradient-fluxes in the lower part of the plant stand. Of special interest is the determination of the location and magnitude of the turbulent mixing between model layers, which permits one to identify the effects of large eddies transporting momentum and scalar quantities into the canopy. A comparison between model simulations and field measurements will be presented in a future paper.

  9. Neutral atmospheric models compatible with satellite orbital decay and incoherent scatter measurements

    NASA Technical Reports Server (NTRS)

    Rohrbaugh, J. L.

    1972-01-01

    A correlation study was made of the variations of the exospheric temperature extrema with various combinations of the monthly mean and daily values of the 2800 MHz and Ca:2 solar indices. The phase and amplitude of the semi-annual component and the term dependent on Kp were found to remain almost the same for the maximum and minimum temperature. The term dependent on the 27 day component of the solar activity was found to be about four times as large for the diurnal maximum as for the minimum. Measurements at Arecibo have shown that temperature gradient changes at 125 km are consistent with the phase difference between the neutral temperature and density maxima. This is used to develop an empirical model which is compatible with both the satellite measurements and the available incoherent scatter measurements. A main feature of this model is that day length is included as a major model parameter.

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

    NASA Astrophysics Data System (ADS)

    Pandolfi, M.; Martucci, G.; Querol, X.; Alastuey, A.; Wilsenack, F.; Frey, S.; O'Dowd, C. D.; 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 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 observed during NAF (β500=0.77±0.57 M m-1 sr-1) when compared with ATL (β500= 0.51±0.44 M m-1 sr-1

  11. Investigation of chemical properties and transport phenomena associated with pollutants in the atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Holmes, Heather A.

    Under the Clean Air Act, the U.S. Environmental Protection Agency is required to determine which air pollutants are harmful to human health, then regulate, monitor and establish criteria levels for these pollutants. To accomplish this and for scientific advancement, integration of knowledge from several disciplines is required including: engineering, atmospheric science, chemistry and public health. Recently, a shift has been made to establish interdisciplinary research groups to better understand the atmospheric processes that govern the transport of pollutants and chemical reactions of species in the atmospheric boundary layer (ABL). The primary reason for interdisciplinary collaboration is the need for atmospheric processes to be treated as a coupled system, and to design experiments that measure meteorological, chemical and physical variables simultaneously so forecasting models can be improved (i.e., meteorological and chemical process models). This dissertation focuses on integrating research disciplines to provide a more complete framework to study pollutants in the ABL. For example, chemical characterization of particulate matter (PM) and the physical processes governing PM distribution and mixing are combined to provide more comprehensive data for source apportionment. Data from three field experiments were utilized to study turbulence, meteorological and chemical parameters in the ABL. Two air quality field studies were conducted on the U.S./Mexico border. The first was located in Yuma, AZ to investigate the spatial and temporal variability of PM in an urban environment and relate chemical properties of ambient aerosols to physical findings. The second border air quality study was conducted in Nogales, Sonora, Mexico to investigate the relationship between indoor and outdoor air quality in order to better correlate cooking fuel types and home activities to elevated indoor PM concentrations. The final study was executed in southern Idaho and focused on

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

    NASA Astrophysics Data System (ADS)

    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

  13. Multiyear measurements of the oceanic and atmospheric boundary layers at the Brazil-Malvinas confluence region

    NASA Astrophysics Data System (ADS)

    Pezzi, Luciano Ponzi; de Souza, Ronald Buss; Acevedo, OtáVio; Wainer, Ilana; Mata, Mauricio M.; Garcia, Carlos A. E.; de Camargo, Ricardo

    2009-10-01

    This study analyzes and discusses data taken from oceanic and atmospheric measurements performed simultaneously at the Brazil-Malvinas Confluence (BMC) region in the southwestern Atlantic Ocean. This area is one of the most dynamical frontal regions of the world ocean. Data were collected during four research cruises in the region once a year in consecutive years between 2004 and 2007. Very few studies have addressed the importance of studying the air-sea coupling at the BMC region. Lateral temperature gradients at the study region were as high as 0.3°C km-1 at the surface and subsurface. In the oceanic boundary layer, the vertical temperature gradient reached 0.08°C m-1 at 500 m depth. Our results show that the marine atmospheric boundary layer (MABL) at the BMC region is modulated by the strong sea surface temperature (SST) gradients present at the sea surface. The mean MABL structure is thicker over the warmside of the BMC where Brazil Current (BC) waters predominate. The opposite occurs over the coldside of the confluence where waters from the Malvinas (Falkland) Current (MC) are found. The warmside of the confluence presented systematically higher MABL top height compared to the coldside. This type of modulation at the synoptic scale is consistent to what happens in other frontal regions of the world ocean, where the MABL adjusts itself to modifications along the SST gradients. Over warm waters at the BMC region, the MABL static instability and turbulence were increased while winds at the lower portion of the MABL were strong. Over the coldside of the BC/MC front an opposite behavior is found: the MABL is thinner and more stable. Our results suggest that the sea-level pressure (SLP) was also modulated locally, together with static stability vertical mixing mechanism, by the surface condition during all cruises. SST gradients at the BMC region modulate the synoptic atmospheric pressure gradient. Postfrontal and prefrontal conditions produce opposite thermal

  14. Vertical distribution of CO2 in the atmospheric boundary layer: Characteristics and impact of meteorological variables

    NASA Astrophysics Data System (ADS)

    Li, Yanli; Deng, Junjun; Mu, Chao; Xing, Zhenyu; Du, Ke

    2014-07-01

    Knowledge of vertical CO2 distribution is important for development of CO2 transport models and calibration/validation of satellite-borne measurements. In this study, vertical profiles of CO2 concentration within 0-1000 m were measured using a tethered balloon at a suburban site in Xiamen, which is undergoing fast urbanization. The characteristics of CO2 vertical distribution were investigated under both stable and convective boundary-layer conditions. The correlation of ground level CO2 concentrations and those at high altitudes decreased with altitude and show significant correlation in the first 300 m with R = 0.78 at 100 m, R = 0.52 at 200 m, R = 0.40 at 300 m (P < 0.01). The correlation keeps almost constant for 300-800 m, and there is no obvious correlation at 800 m, indicating that the impact of ground level CO2 was restricted within the 300 m above the ground. When comparing the vertical profiles obtained at different times during a 24 h period, it was found that CO2 concentration exhibited more obvious diurnal pattern at surface level than at high altitude because of the variation of sources and sinks of CO2 at ground level. Most profiles demonstrated declining trends of CO2 concentration with increasing altitude. The vertical profiles of CO2 were fitted to obtain an empirical equation for estimating CO2 vertical concentration in the lower atmosphere (0-1000 m): y = -75.04 + 1.17 × 109e-x/28.01, R2 = 0.59 (P < 0.05). However, for some cases opposite patterns were observed that the CO2 concentration profiles showed a turning point at a certain altitude or little variation with altitude under certain meteorological conditions. The atmospheric boundary layer depth and atmospheric stability are two major factors controlling the vertical structure of CO2 profile. The results would improve our understanding of the spatial and temporal variation of CO2 in urban environment, which would facilitate using 3-D transport model to study the impacts of CO2 on urban

  15. Atmospheric boundary layer and ozone-aerosol interactions under Saharan intrusions observed during AMISOC summer campaign

    NASA Astrophysics Data System (ADS)

    Adame, J. A.; Córdoba-Jabonero, C.; Sorribas, M.; Toledo, D.; Gil-Ojeda, M.

    2015-03-01

    A research campaign was performed for the AMISOC (Atmospheric Minor Species relevant to the Ozone Chemistry) project at El Arenosillo observatory (southwest Spain) in May-June 2012. The campaign focused on the impact of Saharan dust intrusions at the atmospheric boundary layer (ABL) and ozone-aerosol interactions. In-situ and remote-sensing techniques for gases and aerosols were used in addition to modelling analyses. Meteorology features, ABL structures and evolution, aerosol profiling distributions and aerosol-ozone interactions on the surface were analysed. Two four-day periods were selected according to non-dusty (clean conditions) and dusty (Saharan dust) situations. In both scenarios, sea-land breezes developed in the lower atmosphere, but differences were found in the upper levels. Results show that surface temperatures were greater than 3 °C and humidity were lower during dusty than non-dusty conditions. Thermal structures on the surface layer (estimated using an instrument on a 100 m tower) show differences, mainly during nocturnal periods with less intense inversions under dusty conditions. The mixing layer during dusty days was 400-800 m thick, less than observed on non-dusty. Dust also disturbed the typical daily ABL evolution. Stable conditions were observed in the early evening during intrusions. Aerosol extinction on dusty days was 2-3 times higher, and the dust was confined between 1500 and 5500 m. Back trajectory analyses confirmed that the dust had an African origin. On surface, the particle concentration was approximately 3.5 times higher during dusty events, but the local ozone did not exhibit any change. The arrival of Saharan dust in the upper levels impacted the meteorological surface, inhibited the daily evolution of the ABL and caused an increase in aerosol loading on the surface and at higher altitudes; however, no dust influence was observed on the surface ozone.

  16. Surface ozone-aerosol behaviour and atmospheric boundary layer structure in Saharan dusty scenario

    NASA Astrophysics Data System (ADS)

    Adame, Jose; Córdoba-Jabonero, Carmen; Sorrribas, Mar; Gil-Ojeda, Manuel; Toledo, Daniel; Yela, Margarita

    2016-04-01

    A research campaign was performed for the AMISOC (Atmospheric Minor Species relevant to the Ozone Chemistry) project at El Arenosillo observatory (southwest Spain) in May-June 2012. The campaign focused on the impact of Saharan dust intrusions at the Atmospheric Boundary Layer (ABL) and ozone-aerosol interactions. In-situ and remote-sensing techniques for gases and aerosols were used moreover to modelling analyses. Meteorology features, ABL structures and evolution, aerosol profiling distributions and aerosol-ozone interactions on the surface were analysed. Two four-day periods were selected according to non-dusty (clean conditions) and dusty (Saharan dust) situations. In both scenarios, sea-land breezes developed in the lower atmosphere, but differences were found in the upper levels. Results show that surface temperatures were greater than 3°C and humidity values were lower during dusty conditions than non-dusty conditions. Thermal structures on the surface layer (estimated using an instrument on a 100 m tower) show differences, mainly during nocturnal periods with less intense inversions under dusty conditions. The mixing layer during dusty days was 400-800 m thick, less than observed on non-dusty days. Dust also disturbed the typical daily ABL evolution. Stable conditions were observed during the early evening during intrusions. Aerosol extinction on dusty days was 2-3 times higher, and the dust was confined between 1500 and 5500 m. Back trajectory analyses confirmed that the dust had an African origin. On the surface, the particle concentration was approximately 3.5 times higher during dusty events, but the local ozone did not exhibit any change. The arrival of Saharan dust in the upper levels impacted the meteorological surface, inhibited the daily evolution of the ABL and caused an increase in aerosol loading on the surface and at higher altitudes; however, no dust influence was observed on surface ozone.

  17. On transient climate change at the Cretaceous-Paleogene boundary due to atmospheric soot injections.

    PubMed

    Bardeen, Charles G; Garcia, Rolando R; Toon, Owen B; Conley, Andrew J

    2017-09-05

    Climate simulations that consider injection into the atmosphere of 15,000 Tg of soot, the amount estimated to be present at the Cretaceous-Paleogene boundary, produce what might have been one of the largest episodes of transient climate change in Earth history. The observed soot is believed to originate from global wildfires ignited after the impact of a 10-km-diameter asteroid on the Yucatán Peninsula 66 million y ago. Following injection into the atmosphere, the soot is heated by sunlight and lofted to great heights, resulting in a worldwide soot aerosol layer that lasts several years. As a result, little or no sunlight reaches the surface for over a year, such that photosynthesis is impossible and continents and oceans cool by as much as 28 °C and 11 °C, respectively. The absorption of light by the soot heats the upper atmosphere by hundreds of degrees. These high temperatures, together with a massive injection of water, which is a source of odd-hydrogen radicals, destroy the stratospheric ozone layer, such that Earth's surface receives high doses of UV radiation for about a year once the soot clears, five years after the impact. Temperatures remain above freezing in the oceans, coastal areas, and parts of the Tropics, but photosynthesis is severely inhibited for the first 1 y to 2 y, and freezing temperatures persist at middle latitudes for 3 y to 4 y. Refugia from these effects would have been very limited. The transient climate perturbation ends abruptly as the stratosphere cools and becomes supersaturated, causing rapid dehydration that removes all remaining soot via wet deposition.

  18. On transient climate change at the Cretaceous‑Paleogene boundary due to atmospheric soot injections

    NASA Astrophysics Data System (ADS)

    Bardeen, Charles G.; Garcia, Rolando R.; Toon, Owen B.; Conley, Andrew J.

    2017-09-01

    Climate simulations that consider injection into the atmosphere of 15,000 Tg of soot, the amount estimated to be present at the Cretaceous‑Paleogene boundary, produce what might have been one of the largest episodes of transient climate change in Earth history. The observed soot is believed to originate from global wildfires ignited after the impact of a 10-km-diameter asteroid on the Yucatán Peninsula 66 million y ago. Following injection into the atmosphere, the soot is heated by sunlight and lofted to great heights, resulting in a worldwide soot aerosol layer that lasts several years. As a result, little or no sunlight reaches the surface for over a year, such that photosynthesis is impossible and continents and oceans cool by as much as 28 °C and 11 °C, respectively. The absorption of light by the soot heats the upper atmosphere by hundreds of degrees. These high temperatures, together with a massive injection of water, which is a source of odd-hydrogen radicals, destroy the stratospheric ozone layer, such that Earth’s surface receives high doses of UV radiation for about a year once the soot clears, five years after the impact. Temperatures remain above freezing in the oceans, coastal areas, and parts of the Tropics, but photosynthesis is severely inhibited for the first 1 y to 2 y, and freezing temperatures persist at middle latitudes for 3 y to 4 y. Refugia from these effects would have been very limited. The transient climate perturbation ends abruptly as the stratosphere cools and becomes supersaturated, causing rapid dehydration that removes all remaining soot via wet deposition.

  19. Speciated atmospheric mercury in the marine boundary layer of the Bohai Sea and Yellow Sea

    NASA Astrophysics Data System (ADS)

    Wang, Chunjie; Ci, Zhijia; Wang, Zhangwei; Zhang, Xiaoshan; Guo, Jia

    2016-04-01

    The objectives of this study are to identify the spatial and temporal distributions of gaseous elemental mercury (GEM), reactive gaseous mercury (RGM), and fine particulate mercury (HgP2.5) in the marine boundary layer (MBL) of the Bohai Sea (BS) and Yellow Sea (YS), and to investigate the relationships between mercury species and meteorological parameters. The mean concentrations of GEM, RGM, and HgP2.5 were 2.03 ng m-3, 2.5 pg m-3, and 8.2 pg m-3 in spring, and 2.09 ng m-3, 4.3 pg m-3, and 8.3 pg m-3 in fall. Reactive mercury (RGM + HgP2.5) represented < 1% of total atmospheric mercury (GEM + RGM + HgP2.5), which indicated that most mercury export in the MBL was GEM and the direct outflow of reactive mercury was very small. Moreover, GEM concentrations over the BS were generally higher than those over the YS both in spring and fall. Although RGM showed a homogeneous distribution over the BS and YS both in spring and fall, the mean RGM concentration in fall was significantly higher than that in spring. In contrast, the spatial distribution of HgP2.5 generally reflected a gradient with high levels near the coast of China and low levels in the open sea, suggesting the significant atmospheric mercury outflow from China. Interestingly, the mean RGM concentrations during daytime were significantly higher than those during nighttime both in spring and fall, while the opposite results were observed for HgP2.5. Additionally, RGM positively correlates with air temperature while negatively correlates with relative humidity. In conclusion, the elevated atmospheric mercury levels in the BS and YS compared to other open seas suggested that the human activities had a significant influence on the oceanic mercury cycle downwind of China.

  20. The Influence of High Aerosol Concentration on Atmospheric Boundary Layer Temperature Stratification

    SciTech Connect

    Khaykin, M.N.; Kadygrove, E.N.; Golitsyn, G.S.

    2005-03-18

    Investigations of the changing in the atmospheric boundary layer (ABL) radiation balance as cased by natural and anthropogenic reasons is an important topic of the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) program. The influence of aerosol on temperature stratification of ABL while its concentration was extremely high within a long period of time was studied experimentally. The case was observed in Moscow region (Russia) with the transport of combustion products from peat-bog and forest fires in July-September, 2002. At this time the visibility was some times at about 100-300 m. Aerosol concentration measured by Moscow University Observatory and A.M. Obukhov Institute of Atmospheric Physics field station in Zvenigorod (55.7 N; 36.6 E) for several days was in 50-100 times more than background one (Gorchakov at al 2003). The high aerosol concentration can change the radiation balance at ABL, and so to change thermal stratification in ABL above the mega lopolis. For the analysis the data were used of synchronous measurements by MTP-5 (Microwave Temperature Profiler operating at wavelength 5 mm) in two locations, namely: downtown Moscow and country-side which is 50 km apart to the West (Zvenigorod station). (Kadygrov and Pick 1998; Westwater at al 1999; Kadygrov at al 2002). Zvenigorod station is located in strongly continental climate zone which is in between of the climates of ARM sites (NSANorth Slope of Alaska and SGP-Southern Great Plains). The town of Zvenigorod has little industry, small traffic volume and topography conductive to a good air ventilation of the town. For these reasons Zvenigorod can be considered as an undisturbed rural site. For the analysis some days were chosen with close meteorological parameters (average temperature, humidity, wind, pressure and cloud form) but strongly differing in aerosol concentration level.

  1. Neutralization of atmospheric acidity by chemical weathering in an alpine drainage basin in the North Cascade mountains

    SciTech Connect

    Drever, J.I.; Hurcomb, D.R.

    1986-03-01

    The most important weathering reaction that neutralizes incoming atmospheric acidity in the South Cascade Lake basin is weathering of calcite, which occurs in trace amounts in veins, on joint surfaces, and as a subglacial surficial deposit. Although the basin is underlain by igneous and high-grade metamorphic rocks, weathering of plagioclase is quantitatively negligible; the principal silicate weathering reaction is alteration of biotite to vermiculite. These conclusions are based on mass-balance calculations involving runoff compositions and on mineralogical observations. For predictive modeling of the effects of increased acid deposition, it is essential to identify the relevant weathering reactions. Feldspar weathering is commonly not an important source of solutes in alpine basins underlain by granitic rocks. 30 references, 2 figures, 1 table.

  2. Particle and Joule heating of the neutral polar thermosphere in cusp region using atmosphere Explorer-C satellite measurements

    NASA Technical Reports Server (NTRS)

    Griffis, M.; Nisbet, J. S.; Bleuler, E.

    1981-01-01

    It is pointed out that thermospheric heating in the auroral zone and polar cap is of great importance to the variations in the high-latitude neutral wind and the resulting global temperature and densities. The considered investigation is concerned with relating in a quantitative manner the energy inputs from the Joule heating and particle inputs with the thermospheric responses, taking into account the cusp region, and the region of the eastward auroral electrojet. The data used in the investigation were obtained by the Atmosphere Explorer C satellite in late December 1974. Attention is given to electric fields derived from ion drift measurements, electric field strength and particle energy flux measured by the low energy electron experiment for AE-C orbit 4708, electron density contours, Joule heating contours, and height integrated Joule heating and particle energy flux.

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

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

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

  4. MGS Radio Science Electron Density Profiles: Interannual Variability and Implications for the Martian Neutral Atmosphere

    NASA Technical Reports Server (NTRS)

    Bougher, Stephen W.; Engel, S.; Hinson, D. P.; Murphy, J. R.

    2003-01-01

    Martian electron density profiles provided by the Mars Global Surveyor (MGS) Radio Science (RS) experiment over the 95-200 km altitude range indicate that the height of the electron peak and the longitudinal structure of the peak height are sensitive indicators of the physical state of the Mars lower atmosphere. The present analysis is carried out on five sets of occultation profiles, all at high solar zenith angles (SZA). Variations spanning 2-Martian years are investigated near aphelion conditions at high Northern latitudes (64.7-77.6N). A mean ionospheric peak height of 133.5-135 km was obtained for all aphelion profiles near SZA = 78-82; a corresponding mean peak density of 7.3-8.5 x 10(exp 4)/cu cm was also measured, reflecting solar moderate conditions. Strong wave 2-3 oscillations in peak heights were observed as a function of longitude over both Martian seasons. The Mars Thermospheric General Circulation Model (MTGCM) is exercised for Mars aphelion conditions. The measured interannual variations in the mean and longitude structure of the peak heights are small (consistent with MTGCM simulations), signifying the repeatability of the Mars atmosphere during aphelion conditions. A non-migrating (semi-diurnal period, wave#l eastward propagating) tidal mode is likely responsible for the wave#3 longitude features identified. The height of this photochemically driven peak can be observed to provide an ongoing monitor of the changing state of the Mars lower atmosphere. The magnitudes of these same peaks may reflect more than changing solar EUV fluxes when they are located in the vicinity of Mars crustal magnetic field centers.

  5. MGS Radio Science Electron Density Profiles: Interannual Variability and Implications for the Martian Neutral Atmosphere

    NASA Technical Reports Server (NTRS)

    Bougher, Stephen W.; Engel, S.; Hinson, D. P.; Murphy, J. R.

    2003-01-01

    Martian electron density profiles provided by the Mars Global Surveyor (MGS) Radio Science (RS) experiment over the 95-200 km altitude range indicate that the height of the electron peak and the longitudinal structure of the peak height are sensitive indicators of the physical state of the Mars lower atmosphere. The present analysis is carried out on five sets of occultation profiles, all at high solar zenith angles (SZA). Variations spanning 2-Martian years are investigated near aphelion conditions at high Northern latitudes (64.7-77.6N). A mean ionospheric peak height of 133.5-135 km was obtained for all aphelion profiles near SZA = 78-82; a corresponding mean peak density of 7.3-8.5 x 10(exp 4)/cu cm was also measured, reflecting solar moderate conditions. Strong wave 2-3 oscillations in peak heights were observed as a function of longitude over both Martian seasons. The Mars Thermospheric General Circulation Model (MTGCM) is exercised for Mars aphelion conditions. The measured interannual variations in the mean and longitude structure of the peak heights are small (consistent with MTGCM simulations), signifying the repeatability of the Mars atmosphere during aphelion conditions. A non-migrating (semi-diurnal period, wave#l eastward propagating) tidal mode is likely responsible for the wave#3 longitude features identified. The height of this photochemically driven peak can be observed to provide an ongoing monitor of the changing state of the Mars lower atmosphere. The magnitudes of these same peaks may reflect more than changing solar EUV fluxes when they are located in the vicinity of Mars crustal magnetic field centers.

  6. Dust and neutral gas modeling of the inner atmospheres of comets

    NASA Technical Reports Server (NTRS)

    Gombosi, T. I.; Nagy, A. F.; Cravens, T. E.

    1986-01-01

    This paper summarizes the present, preencounter understanding of the physical and chemical processes controlling the inner (r less than 1000 km) region of cometary atmospheres. Special emphasis was attached to compiling a self-consistent set of governing equations. This review is aimed at readers who want to understand the present status of the mantle and coma regions and/or who want to develop new, next generation models which will be needed as the large volume of new observational data will become available in the near future.

  7. Modelling fluctuations in the concentration of neutrally buoyant substances in the atmosphere

    NASA Astrophysics Data System (ADS)

    Ride, David John

    1987-12-01

    The probability density function (PDF) of the perceived concentration of a contaminant in the atmosphere is modeled using simple, physical representations of the dispersing contaminant. Sensors are characterized by the time taken to achieve a reading and by a threshold level of concentration below which the sensor does not respond and thus records a concentration of zero. A literature search of theoretical and experimental work concerning concentration fluctuations is conducted, and the merits - or otherwise - of of some common PDF's in common use are discussed.

  8. Are there physical links between Saturn's magnetospheric planetary period oscillations, neutral atmosphere circulation, and thunderstorm activity? (Invited)

    NASA Astrophysics Data System (ADS)

    Provan, G.; Cowley, S. W.

    2013-12-01

    Suggestions that the planetary period oscillations (PPOs) observed in Saturn's magnetosphere may be driven or influenced by neutral atmospheric perturbations, motivates an exploratory comparison of PPO rotation periods with available tropospheric and stratospheric determinations. Non-polar atmospheric rotation periods occupy the range ~10.2-10.7 h associated with the latitudinal jet structure, are similar north and south, and independent of season, while PPO periods lie in a narrower partly overlapping range ~10.6-10.8 h, are persistently shorter north than south, and undergo a seasonal cycle. In this cycle, widely-separated north-south PPO periods during southern summer converge across equinox to values lying within the atmospheric west jet band, remaining well-separated from east jet periods. Closest convergence occurred one year post-equinox, contemporaneously with the switch in seasonal thunderstorm activity from southern to northern hemispheres. Since most large-scale atmospheric phenomena are related to the west jets, rotating with closely similar periods, they also rotate with periods close to the PPOs under post-equinoctial conditions, but not otherwise. Specifically, post-equinox northern PPOs rotate with a period close to the southern thunderstorms, as well as the north polar spot and hexagon features, while the post equinox southern PPOs rotate with a period close to the pre-equinox northern ';string of pearls' and the first co-located post-equinox northern thunderstorm, the Great White Spot event. However, even under these conditions no consistent correspondences in period are found at a detailed level, which taken together with the lack of correspondence at other times, does not suggest a direct physical link exists between these phenomena.

  9. Saturn's magnetospheric planetary period oscillations, neutral atmosphere circulation, and thunderstorm activity: Implications, or otherwise, for physical links

    NASA Astrophysics Data System (ADS)

    Cowley, S. W. H.; Provan, G.

    2013-11-01

    that the planetary period oscillations (PPOs) observed in Saturn's magnetosphere may be driven or influenced by neutral atmospheric perturbations motivate an exploratory comparison of PPO rotation periods with available tropospheric and stratospheric determinations. Nonpolar atmospheric rotation periods occupy the range ~10.2-10.7 h associated with the latitudinal jet structure, are similar north and south, and are independent of season, while PPO periods lie in a narrower partly overlapping range ~10.6-10.8 h, are persistently shorter north than south, and undergo a seasonal cycle. In this cycle, widely separated north-south PPO periods during southern summer converge across equinox to values lying within the atmospheric west jet band, remaining well-separated from east jet periods. Closest convergence occurred 1 year post equinox, contemporaneously with the switch in seasonal thunderstorm activity from Southern to Northern Hemispheres. Since most large-scale atmospheric phenomena are related to the west jets, rotating with closely similar periods, they also rotate with periods close to the PPOs under post equinoctial conditions but not otherwise. Specifically, post equinox northern PPOs rotate with a period close to the southern thunderstorms, as well as the north polar spot and hexagon features, while the post equinox southern PPOs rotate with a period close to the pre-equinox northern "string of pearls" and the first colocated post equinox northern thunderstorm, the Great White Spot event. However, even under these conditions, no consistent correspondences in period are found at a detailed level, which taken together with the lack of correspondence at other times does not suggest a direct physical link exists between these phenomena.

  10. A parametrization, based on sea ice morphology, of the neutral atmospheric drag coefficients for weather prediction and climate models

    NASA Astrophysics Data System (ADS)

    Lüpkes, Christof; Gryanik, Vladimir M.; Hartmann, JöRg; Andreas, Edgar L.

    2012-07-01

    A hierarchy of parametrizations of the neutral 10 m drag coefficients over polar sea ice with different morphology regimes is derived on the basis of a partitioning concept that splits the total surface drag into contributions of skin drag and form drag. The new derivation, which provides drag coefficients as a function of sea ice concentration and characteristic length scales of roughness elements, needs fewer assumptions than previous similar approaches. It is shown that form drag variability can explain the variability of surface drag in the marginal sea ice zone (MIZ) and in the summertime inner Arctic regions. In the MIZ, form drag is generated by floe edges; in the inner Arctic, it is generated by edges at melt ponds and leads due to the elevation of the ice surface relative to the open water surface. It is shown that an earlier fit of observed neutral drag coefficients is obtained as a special case within the new concept when specific simplifications are made which concern the floe and melt pond geometry. Due to the different surface morphologies in the MIZ and summertime Arctic, different functional dependencies of the drag coefficients on the sea ice concentration result. These differences cause only minor differences between the MIZ and summertime drag coefficients in average conditions, but they might be locally important for atmospheric momentum transport to sea ice. The new parametrization formulae can be used for present conditions but also for future climate scenarios with changing sea ice conditions.

  11. Interacting kinetics of neutral and ionic species in an atmospheric-pressure helium-oxygen plasma with humid air impurities

    NASA Astrophysics Data System (ADS)

    Murakami, Tomoyuki; Niemi, Kari; Gans, Timo; O'Connell, Deborah; Graham, William G.

    2013-08-01

    We unravel the complex chemistry in both the neutral and ionic systems of a radio-frequency-driven atmospheric-pressure plasma in a helium-oxygen mixture (He-0.5% O2) with air impurity levels from 0 to 500 ppm of relative humidity from 0% to 100% using a zero-dimensional, time-dependent global model. Effects of humid air impurity on absolute densities and the dominant production and destruction pathways of biologically relevant reactive neutral species are clarified. A few hundred ppm of air impurity crucially changes the plasma from a simple oxygen-dependent plasma to a complex oxygen-nitrogen-hydrogen plasma. The density of reactive oxygen species decreases from 1016 to 1015 cm-3, which in turn results in a decrease in the overall chemical reactivity. Reactive nitrogen species (1013 cm-3), atomic hydrogen and hydroxyl radicals (1011-1014 cm-3) are generated in the plasma. With 500 ppm of humid air impurity, the densities of positively charged ions and negatively charged ions slightly increase and the electron density slightly decreases (to the order of 1011 cm-3). The electronegativity increases up to 2.3 compared with 1.5 without air admixture. Atomic hydrogen, hydroxyl radicals and oxygen ions significantly contribute to the production and destruction of reactive oxygen and reactive nitrogen species.

  12. Neutral atmosphere temperature trends and variability at 90 km, 70 °N, 19 °E, 2003-2014

    NASA Astrophysics Data System (ADS)

    Eriksen Holmen, Silje; Hall, Chris M.; Tsutsumi, Masaki

    2016-06-01

    Neutral temperatures at 90 km height above Tromsø, Norway, have been determined using ambipolar diffusion coefficients calculated from meteor echo fading times using the Nippon/Norway Tromsø Meteor Radar (NTMR). Daily temperature averages have been calculated from November 2003 to October 2014 and calibrated against temperature measurements from the Microwave Limb Sounder (MLS) on board Aura. Large-scale periodic oscillations ranging from ˜ 9 days to a year were found in the data using Lomb-Scargle periodogram analysis, and these components were used to seasonally detrend the daily temperature values before assessing trends. Harmonic oscillations found are associated with the large-scale circulation in the middle atmosphere together with planetary and gravity wave activity. The overall temperature change from 2003 to 2014 is -2.2 K ± 1.0 K decade-1, while in summer (May-June-July) and winter (November-December-January) the change is -0.3 K ± 3.1 K decade-1 and -11.6 K ± 4.1 K decade-1, respectively. The temperature record is at this point too short for incorporating a response to solar variability in the trend. How well suited a meteor radar is for estimating neutral temperatures at 90 km using meteor trail echoes is discussed, and physical explanations behind a cooling trend are proposed.

  13. The Relation Between Wind Speed and Air-Sea Temperature Difference in the Marine Atmospheric Boundary Layer off Northwest Europe

    NASA Astrophysics Data System (ADS)

    Kettle, A. J.

    2014-12-01

    Wind speed and atmospheric stability have an important role in determining the turbulence in the marine atmospheric boundary layer (MABL) as well as the surface wave field. The understanding of MABL dynamics in northwest Europe is complicated by fetch effects, the proximity of coastlines, shallow topography, and larger scale circulation patterns (e.g., cold air outbreaks). Numerical models have difficulty simulating the marine atmospheric boundary layer in coastal areas and partially enclosed seas, and this is partly due to spatial resolution problems at coastlines. In these offshore environments, the boundary layer processes are often best understood directly from time series measurements from fixed platforms or buoys, in spite of potential difficulties from platform flow distortion as well as the spatial sparseness of the data sets. This contribution presents the results of time series measurements from offshore platforms in the North Sea and Norwegian Sea in terms of a summary diagnostic - wind speed versus air-sea temperature difference (U-ΔT) - with important implications for understanding atmospheric boundary layer processes. The U-ΔT diagram was introduced in earlier surveys of data from coastal (Sletringen; O.J. Andersen and J. Løvseth, J. Wind Eng. Ind. Aerodyn., 57, 97-109, 1995) and offshore (Statfjord A; K.J. Eidsvik, Boundary-Layer Meteorol., 32, 103-132, 1985) sites in northwest Europe to summarize boundary layer conditions at a given location. Additional information from a series of measurement purpose-built offshore measurement and oil/gas production platforms from the southern North Sea to the Norwegian Sea illustrates how the wind characteristics vary spatially over large distances, highlighting the influence of cold air outbreaks, in particular. The results are important for the offshore wind industry because of the way that wind turbines accrue fatigue damage in different conditions of atmospheric stability and wind speed.

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

    NASA Astrophysics Data System (ADS)

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

    2006-03-01

    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 Surface Exchange Study (CASES-99) field experiment. Very high model resolution in the atmosphere and the soil is utilized to represent three different stable boundary layer archetypes, namely, a fully turbulent night, an intermittently turbulent night, and a radiative night with hardly any turbulence (all at clear skies). Each archetype represents a different class of atmospheric stability. In the current model, the atmosphere is fully coupled to a vegetation layer and the underlying soil. In addition, stability functions (local scaling) are utilized based on in situ observations.Overall it is found that the vertical structure, the surface fluxes (apart from the intermittent character) and the surface temperature in the stable boundary layer can be satisfactorily modeled for a broad stability range (at a local scale) with the current understanding of the physics of the stable boundary layer. This can also be achieved by the use of a rather detailed coupling between the atmosphere and the underlying soil and vegetation, together with high resolution in both the atmosphere and the soil. This is especially true for the very stable nights, when longwave radiative cooling is dominant. Both model outcome and observations show that in the latter case the soil heat flux is a dominant term of the surface energy budget.


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

    NASA Astrophysics Data System (ADS)

    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.

  16. Array of Neutral Density Relative Observations MEasuring Divergence in the Atmosphere (ANDROMEDA), A Constellation Concept for Studying Thermospheric Dynamics

    NASA Astrophysics Data System (ADS)

    Palo, S. E.; Pilinski, M.; Forbes, J. M.

    2015-12-01

    In addition to being critical to the prediction of satellite orbits, total mass density is a fundamental property of the thermosphere. Density measurements from accelerometers on the CHAMP satellite have revealed quasi-steady state distributions of density structures around the globe, density responses to changing solar and geomagnetic activity, and spatial structures of wave-like phenomena along the orbit. However, a basic limitation on the time scale of any observable phenomenon is the ~90-minute orbital period. Thus, single-satellite missions like CHAMP are unable to measure the time derivative of density or the mass flux divergence (MFD) at a single point in the atmosphere. While the two accelerometer-carrying GRACE satellites could theoretically measure the density time derivative, in practice this measurement is hampered by the very low-signal levels in the tenuous atmosphere at the ~500-km GRACE orbits, as well as inter-satellite biases and drifts. The Array of Neutral Density Relative Observations Measuring Divergence in the Atmosphere (ANDROMEDA) is a constellation of CubeSats aimed at improving our understanding of atmospheric dynamics by measuring and interpreting the characteristics of traveling atmospheric disturbances as well as the distribution of MFD in the thermosphere. The ANDROMEDA constellation consists of two to three identical CubeSats spaced approximately 300 km apart and making multi-point measurements of total mass density with an accuracy of <2%. The mass density measurements will be made using a novel torque balance technique enabled by an extremely accurate attitude determination and control system (ADCS) that actively compensates for atmospheric disturbance torques. The benefit of the torque-balance technique is the high level of inter-satellite accuracy. The constellation will be deployed from the ISS and will make observations between 400 km and 250 km altitude as the satellite orbits decay. Distance between the spacecraft will be

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Technical Reports Server (NTRS)

    Allison, D. E.

    1984-01-01

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

  19. MGS Radio Science Electron Density Profiles: Interannual Variability and Implications for the Martian Neutral Atmosphere

    NASA Technical Reports Server (NTRS)

    Bougher, S. W.; Engel, S.; Hinson, D. P.; Murphy, J. R.

    2004-01-01

    Martian electron density profiles provided by the Mars Global Surveyor (MGS) Radio Science (RS) experiment over the 95-200 km altitude range indicate what the height of the electron peak and the longitudinal structure of the peak height are sensitive indicators of the physical state of the Mars lower and upper atmospheres. The present analysis is carried out on five sets of occultation profiles, all at high solar zenith angles (SZA). Variations spanning 2 Martian years are investigated near aphelion conditions at high northern latitudes (64.7 - 77.6 N) making use of four of these data sets. A mean ionospheric peak height of 133.5 - 135 km is obtained near SZA = 78 - 82 deg.; a corresponding mean peak density of 7.3 - 8.5 x l0(exp 4)/ qu cm is also measured during solar moderate conditions at Mars. Strong wave number 2 - 3 oscillations in peak heights are consistently observed as a function of longitude over the 2 Martian years. These observed ionospheric features are remarkably similar during aphelion conditions 1 Martian year apart. This year-to-year repeatability in the thermosphere-ionosphere structure is consistent with that observed in multiyear aphelion temperature data of the Mars lower atmosphere. Coupled Mars general circulation model (MGCM) and Mars thermospheric general circulation model (MTGCM) codes are run for Mars aphelion conditions, yielding mean and longitude variable ionospheric peak heights that reasonably match RS observations. A tidal decomposition of MTGCM thermospheric densities shows that observed ionospheric wave number 3 features are linked to a non-migrating tidal mode with semidiurnal period (sigma = 2) and zonal wave number 1 (s = -1) characteristics. The height of this photochemically determined ionospheric peak should be monitored regularly.

  20. MGS Radio Science Electron Density Profiles: Interannual Variability and Implications for the Martian Neutral Atmosphere

    NASA Technical Reports Server (NTRS)

    Bougher, S. W.; Engel, S.; Hinson, D. P.; Murphy, J. R.

    2004-01-01

    Martian electron density profiles provided by the Mars Global Surveyor (MGS) Radio Science (RS) experiment over the 95-200 km altitude range indicate what the height of the electron peak and the longitudinal structure of the peak height are sensitive indicators of the physical state of the Mars lower and upper atmospheres. The present analysis is carried out on five sets of occultation profiles, all at high solar zenith angles (SZA). Variations spanning 2 Martian years are investigated near aphelion conditions at high northern latitudes (64.7 - 77.6 N) making use of four of these data sets. A mean ionospheric peak height of 133.5 - 135 km is obtained near SZA = 78 - 82 deg.; a corresponding mean peak density of 7.3 - 8.5 x l0(exp 4)/ qu cm is also measured during solar moderate conditions at Mars. Strong wave number 2 - 3 oscillations in peak heights are consistently observed as a function of longitude over the 2 Martian years. These observed ionospheric features are remarkably similar during aphelion conditions 1 Martian year apart. This year-to-year repeatability in the thermosphere-ionosphere structure is consistent with that observed in multiyear aphelion temperature data of the Mars lower atmosphere. Coupled Mars general circulation model (MGCM) and Mars thermospheric general circulation model (MTGCM) codes are run for Mars aphelion conditions, yielding mean and longitude variable ionospheric peak heights that reasonably match RS observations. A tidal decomposition of MTGCM thermospheric densities shows that observed ionospheric wave number 3 features are linked to a non-migrating tidal mode with semidiurnal period (sigma = 2) and zonal wave number 1 (s = -1) characteristics. The height of this photochemically determined ionospheric peak should be monitored regularly.

  1. The Influence of the Several Very Large Solar Proton Events in Years 2000-2003 on the Neutral Middle Atmosphere

    NASA Technical Reports Server (NTRS)

    Jackman, Charles H.; Sinnhuber, Miriam; Anderson, John; McPeters, Richard D.; FLeming, Eric L.; Russell, James M.

    2004-01-01

    Solar proton events (SPEs) are known to have caused changes in constituents in the Earth's neutral middle atmosphere. The highly energetic protons produce ionizations, excitations, dissociations, and dissociative ionizations of the background constituents, which lead to the production of HOx (H, OH, HO2) and NOy (N, NO, NO2, NO3, N2O5, HNO3, HO2NO2, ClONO2, BrONO2). The HOx increases lead to short-lived ozone decreases in the mesosphere and upper stratosphere due to the short lifetimes of the HOx constituents. The NOy increases lead to long-lived stratospheric ozone changes because of the long lifetime of the NOy family in this region. The past four years, 2000-2003, have been replete with SPEs and huge fluxes of high energy protons occurred in July and November 2000, September and November 2001, April 2002, and October 2003. Smaller, but still substantial, proton fluxes impacted the Earth during other months from year 2000 to 2003. The Goddard Space Flight Center (GSFC) Two-dimensional (2D) Model was used in computing the influence of the SPEs. The impact of these extremely large SPEs was calculated to be especially large in the upper stratosphere and mesosphere. The results of the GSFC 2D Model will be shown along with comparisons to the Upper Atmosphere Research Satellite (UARS) Halogen Occultation Experiment (HALOE) and Solar Backscatter Ultraviolet 2 (SBUV/2) instruments.

  2. Structure of the Venus neutral atmosphere as observed by the Radio Science experiment VeRa on Venus Express

    NASA Astrophysics Data System (ADS)

    Tellmann, Silvia; Pätzold, Martin; Häusler, Bernd; Bird, Michael K.; Tyler, G. Leonard

    2009-04-01

    The European Space Agency Venus Express Radio Science experiment (VeRa) obtained 118 radio occultation measurements of the Venusian atmosphere between July 2006 and June 2007. Southern latitudes are uniformly sampled; measurements in the northern hemisphere are concentrated near the pole. Radial profiles of neutral number density derived from the occultations cover the altitude range 40-90 km, which are converted to profiles of temperature (T) and pressure (p) versus height (h). Profiles of static stability are found to be latitude-dependent and nearly adiabatic in the middle cloud region. Below the clouds the stability decreases at high latitudes. At an altitude of 65 km, the VeRa T[p(h)] profiles generally lie between the Venus International Reference Atmosphere (VIRA) and VIRA-2 models; the retrieved temperatures at any given pressure level typically are within 5 K of those derived from the Pioneer Venus Orbiter Radio Occultation experiments. A large equator-to-pole temperature contrast of ˜30 K is found at the 1-bar (1000 hPa) level. The VeRa observations reveal a distinct cold collar region in the southern hemisphere, complementing that in the north. At the latitudes of the cold collars, the tropopause altitude increases relative to higher and lower latitudes by ≈7 km while the temperature drops roughly 60 K. The observations indicate the existence of a wave number 2 structure poleward of ±75° latitude at altitudes of 62 km.

  3. Chemistry of neutral species in the effluent of the micro atmospheric pressure plasma jet in water-helium admixture

    NASA Astrophysics Data System (ADS)

    Willems, Gert; Benedikt, Jan; von Keudell, Achim

    2016-09-01

    A thorough understanding and good control of produced neutral and charged species by cold atmospheric plasmas is essential for potential environmental and/or bio-medical applications. In this study we use the COST reference micro plasma jet (µ-APPJ), which is a radio-frequency capacitive coupled plasma source with 1 mm electrode distance, which has been operated in helium-water vapour mixture and has been studied as a potential source of hydroxyl radicals and hydrogen peroxide molecules. The water vapour concentration was up to 1.2%. Molecular Beam mass spectrometry is used as diagnostic tool. An absolute calibration of hydrogen peroxide was conducted using a double bubbler concept, because the ionization cross section for hydrogen peroxide is not available. Additionally the effluent chemistry was investigated by use of a 0D and 2D model. Absolute densities of hydrogen peroxide and hydroxyl radicals from atmospheric plasma will be presented. Their dependency on water vapour concentration in the carrier gas as well as distance to target have been investigated. The measured density is between 5E-13 cm-3 (2.4ppm) and 1.5E-14 cm-3 (7.2ppm) for both hydrogen peroxide molecules and hydroxyl radicals. The achieved results are in good agreement with other experiments.

  4. Observations of the neutral atmosphere between 100 and 200 km using ARIA rocket-borne and ground-based instruments

    SciTech Connect

    Hecht, J.H.; Christensen, A.B.; Gutierrez, D.J.; Kayser, D.C.; Sharp, W.E.; Sharber, J.R.; Winningham, J.D.; Frahm, R.A.; Strickland, D.J.; Mcewen, D.J.

    1995-11-01

    The atmospheric response in the aurora (ARIA) rocket was launched at 1406 UT on March 3, 1992, from Poker Flat, Alaska, into a pulsating diffuse aurora; rocket-borne instruments included an eight-channel photometer, a far ultraviolet spectrometer, a 130.4-nm atomic oxygen resonance lamp, and two particle spectrometers covering the energy range of 1-400 eV and 10 eV to 20 keV. The photometer channels were isolated using narrow-band interference filters and included measurements of the strong permitted auroral emissions N2 (337.1-nm), N2(+) (391.4-nm), and O I (844.6-nm). A ground-based photometer measured the permitted N2(+) (427.8-nm), the forbidden O I (630.0-nm), and the permitted O I (844.6-nm) emissions. The ground-based instrument was pointed in the magnetic zenith. Also, the rocket payload was pointed in the magnetic zenith from 100 to 200 km on the upleg. The data were analyzed using the Strickland electron transport code, and the rocket and ground-based results were found to be in good agreement regarding the inferred characteristic energy (E(sub 0) is approximately equal to 3 keV) of the precipitating auroral flux and the composition of the neutral atmosphere during the rocket flight. In particular, it was found that the O/N2 density ratio in the neutral atmosphere diminished during the auroral substorm, which started about 2 hours before the ARIA rocket flight. The data showed that there was about a 10-minute delay between the onset of the substorm and the decrease of the O/N2 density ratio. At the time of the ARIA flight this ratio had nearly returned to its presubstorm value. However, the data also showed that the O/N2 density ration did not recover to its presubstorm value until nearly 30 minutes after the particle and joule heating had subsided. Both the photometer and oxygen resonance lamp data showed the presence of structure in the atomic oxygen densities in the region above 130 km.

  5. Observations of the neutral atmosphere between 100 and 200 km using ARIA rocket-borne and ground-based instruments

    SciTech Connect

    Hecht, J.H.; Christensen, A.B.; Gutierrez, D.J.

    1995-09-01

    The atmospheric response in the aurora (ARIA) rocket was launched at 1406 UT on March 3, 1992, from Poker Flat, Alaska, into a pulsating diffuse aurora; rocket-borne instruments included an eight-channel photometer, a far ultraviolet spectrometer, a 130.4-nm atomic oxygen resonance lamp, and two particle spectrometers covering the energy range of 1-400 eV and 10 eV to 20 keV. The photometer channels were isolated using narrow-band interference filters and included measurements of the strong permitted auroral emissions N{sub 2} (337.1 nm), N{sub 2}{sup +} (391.4 nm), and O I (844.6 nm). A ground-based photometer measured the premitted N{sub 2}{sup +} (427.8 nm), the forbidden O I (630.0 nm), and the premitted O I (844.6 nm) emissions. The ground-based instrument was pointed in the magnetic zenith. Also, the rocket payload was pointed in the magnetic zenith from 100 to 200 km on the upleg. The data were analyzed using the Strickland electron transport code, and the rocket and ground-based results were found to be in good agreement regarding the inferred characteristic energy of the precipitating auroral flux and the composition of the neutral atmosphere during the rocket flight. In particular, it was found that the O/N{sub 2} density ratio in the neutral atmosphere diminished during the auroral substorm, which started about 2 hours before the ARIA rocket flight. The data showed that there was about a 10-min delay between the onset of the substorm and the decrease of the O/N{sub 2} density ratio. At the time of the ARIA flight this ratio had nearly returned to its presubstorm value. However, the data also showed that the O/N{sub 2} density ratio did not recover to its presubstorm value until nearly 30 min after the particle and joule heating had subsided. Both the photometer and oxygen densities in the region above 130 km. The observed auroral brightness ratio B{sub 337.1}/B{sub 391.4} equaled 0.29 and was in agreement with other recent measurements.

  6. A Climatology of Atmospheric Rivers Potentially Impacting the Boundary Layer over Greenland: 1871-2012

    NASA Astrophysics Data System (ADS)

    Neff, William; Compo, Gilbert P.

    2016-04-01

    Recently, (Neff et al. 2014) examined the 2012 Greenland melt episode and compared it to the last episode in 1889 using the Twentieth Century Reanalysis (Compo et al. 2011), finding similar factors at work. A key factor in 2012 was the presence of an Atmospheric River (AR) that transported warm air from a mid-continent heat wave over the Atlantic Ocean and thence to the west coast of Greenland and then over the Greenland ice sheet (GIS) with a confirming water vapor isotopic signature (Bonne et al. 2015). ARs are thin filaments of high-moisture air occurring at frontal boundaries and represent an efficient poleward transport mechanism for warm moist air (Newell et al. 1992) to the Arctic (Bonne et al. 2015; Neff et al. 2014) and the Antarctic (Gorodetskaya et al. 2014). Some common characteristics of the events in 1889 and 2012, in addition to the expression of poleward transport as an AR, included continental heat anomalies in the trajectory source regions as well as a trough-ridge pattern that focused transport along the west coast of Greenland. The latter consisted of a trough of low-pressure situated to the west, generally over Baffin Island, and a high-pressure ridge to the southeast of Greenland. This type trough-ridge pattern was also implicated in a major rain event in 2011 along the western margin of the Greenland ice sheet in late summer that accelerated the flow of ice into the ocean (Doyle et al. 2015). Although the events of 2012 and 1889 were extreme, the question remains of how frequent are the near-misses of ARs that are likely to have affected lower elevations and/or included increases in moisture over the GIS that would have modified the boundary layer over the high elevations of the GIS. In this presentation we will show an example of the boundary layer modification lifecycle during the 2012 event and then the climatology of events that reveal an increase in such AR events along the west coast of Greenland over the last three decades.

  7. Imposing land-surface fluxes at an immersed boundary for improved simulations of atmospheric flow over complex terrain

    SciTech Connect

    Lundquist, K A; Chow, F K; Lundquist, J K; Mirocha, J D

    2008-06-05

    Boundary layer flows are greatly complicated by the presence of complex terrain which redirects mean flow and alters the structure of turbulence. Surface fluxes of heat and moisture provide additional forcing which induce secondary flows, or can dominate flow dynamics in cases with weak mean flows. Mesoscale models are increasingly being used for numerical simulations of boundary layer flows over complex terrain. These models typically use a terrain-following coordinate transformation, but these introduce numerical errors over steep terrain. An alternative is to use an immersed boundary method which alleviates errors associated with the coordinate transformation by allowing the terrain to be represented as a surface which arbitrarily passes through a Cartesian grid. This paper describes coupling atmospheric physics models to an immersed boundary method implemented in the Weather Research and Forecasting (WRF) model in previous work [Lundquist et al., 2007]. When the immersed boundary method is used, boundary conditions must be imposed on the immersed surface for velocity and scalar surface fluxes. Previous algorithms, such as those used by Tseng and Ferziger [2003] and Balaras [2004], impose no-slip boundary conditions on the velocity field at the immersed surface by adding a body force to the Navier-Stokes equations. Flux boundary conditions for the advection-diffusion equation have not been adequately addressed. A new algorithm is developed here which allows scalar surface fluxes to be imposed on the flow solution at an immersed boundary. With this extension of the immersed boundary method, land-surface models can be coupled to the immersed boundary to provide realistic surface forcing. Validation is provided in the context of idealized valley simulations with both specified and parameterized surface fluxes using the WRF code. Applicability to real terrain is illustrated with a fully coupled two-dimensional simulation of the Owens Valley in California.

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

    NASA Astrophysics Data System (ADS)

    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.; General, S.; Zielcke, J.; Simpson, W. R.; Platt, U.; Fried, A.; Weibring, P.; Sive, B. C.; Ullmann, K.; Cantrell, C.; Knapp, D. J.; Montzka, D. D.

    2015-03-01

    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 radical chemistry, through the production of a variety of reservoir species, including HNO3, HO2NO2, peroxyacetyl nitrate (PAN), BrNO2, ClNO2 and reductions in BrO and HOBr, with a concomitant, decreased net O3 loss rate. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  10. The Martian atmospheric planetary boundary layer stability, fluxes, spectra, and similarity

    NASA Technical Reports Server (NTRS)

    Tillman, James E.

    1994-01-01

    This is the first analysis of the high frequency data from the Viking lander and spectra of wind, in the Martian atmospheric surface layer, along with the diurnal variation of the height of the mixed surface layer, are calculated for the first time for Mars. Heat and momentum fluxes, stability, and z(sub O) are estimated for early spring, from a surface temperature model and from Viking Lander 2 temperatures and winds at 44 deg N, using Monin-Obukhov similarity theory. The afternoon maximum height of the mixed layer for these seasons and conditions is estimated to lie between 3.6 and 9.2 km. Estimations of this height is of primary importance to all models of the boundary layer and Martian General Circulation Models (GCM's). Model spectra for two measuring heights and three surface roughnesses are calculated using the depth of the mixed layer, and the surface layer parameters and flow distortion by the lander is also taken into account. These experiments indicate that z(sub O), probably lies between 1.0 and 3.0 cm, and most likely is closer to 1.0 cm. The spectra are adjusted to simulate aliasing and high frequency rolloff, the latter caused both by the sensor response and the large Kolmogorov length on Mars. Since the spectral models depend on the surface parameters, including the estimated surface temperature, their agreement with the calculated spectra indicates that the surface layer estimates are self consistent. This agreement is especially noteworthy in that the inertial subrange is virtually absent in the Martian atmosphere at this height, due to the large Kolmogorov length scale. These analyses extend the range of applicability of terrestrial results and demonstrate that it is possible to estimate the effects of severe aliasing of wind measurements, to produce a models which agree well with the measured spectra. The results show that similarity theory developed for Earth applies to Mars, and that the spectral models are universal.

  11. Large-Eddy Simulation of Thermally Stratified Atmospheric Boundary-Layer Flow Using a Minimum Dissipation Model

    NASA Astrophysics Data System (ADS)

    Abkar, Mahdi; Moin, Parviz

    2017-08-01

    A generalized form of a recently developed minimum dissipation model for subfilter turbulent fluxes is proposed and implemented in the simulation of thermally stratified atmospheric boundary-layer flows. Compared with the original model, the generalized model includes the contribution of buoyant forces, in addition to shear, to the production or suppression of turbulence, with a number of desirable practical and theoretical properties. Specifically, the model has a low computational complexity, appropriately switches off in laminar and transitional flows, does not require any ad hoc shear and stability corrections, and is consistent with theoretical subfilter turbulent fluxes. The simulation results show remarkable agreement with well-established empirical correlations, theoretical predictions, and field observations in the atmosphere. In addition, the results show very little sensitivity to the grid resolution, demonstrating the robustness of the model in the simulation of the atmospheric boundary layer, even with relatively coarse resolutions.

  12. Persistent unstable atmospheric boundary layer enhances sensible and latent heat loss in a tropical great lake: Lake Tanganyika

    NASA Astrophysics Data System (ADS)

    Verburg, Piet; Antenucci, Jason P.

    2010-06-01

    Energy fluxes across the surface of lakes regulate heat storage and affect the water balance. Sensible and latent heat fluxes are affected by atmospheric stability, especially for large lakes. We examined the effect of atmospheric stability on the heat fluxes on seasonal time scales at Lake Tanganyika, East Africa, by estimating hourly sensible and latent heat fluxes and net radiation using thermistor chains and meteorological stations. The atmosphere was almost always unstable, in contrast to the atmosphere above North American Great Lakes which is unstable in winter and stable in summer. Persistent atmospheric instability resulted in a 13% and 18% increase in the annual mean heat loss by latent and sensible heat fluxes, respectively, relative to conditions of neutral stability. The persistent unstable atmosphere is caused by a higher water surface temperature compared with air temperature, which we argue is the case in general in (sub)tropical lakes. Low humidity further enhanced the frequency of unstable conditions and enhanced the exchange of heat and vapor from the lake to the atmosphere. The estimated heat fluxes were sensitive to the temporal scale of data inputs and to the local values of parameters such as air density. To our knowledge this is the first paper that demonstrates and quantifies the effect of atmospheric stability on latent and sensible heat fluxes from a lake on an annual basis, using data collected from the lake surface.

  13. Neutrally stable atmospheric flow over a two-dimensional rectangular block

    NASA Technical Reports Server (NTRS)

    Shieh, C. F.; Frost, W.; Bitte, J.

    1977-01-01

    The phenomena of atmospheric flow over a two dimensional surface obstruction such as a building modeled as a rectangular block are analyzed by an approach using the Navier-Stokes equations with a two equation model of turbulence. The partial differential equations for the vorticity, stream function, turbulence kinetic energy, and turbulence length scale are solved by a finite difference technique. The predicted results are in agreement with the limited experimental data available. Current computed results show that the separation bubble originates from the upper front corner of the block and extends approximately 11.5 block heights behind the block. The decay of the mean velocity along the wake center line coincides almost perfectly with the experimental data. The vertical profiles of the mean velocity defect are also in reasonable agreement with wind tunnel results. Velocity profiles in the mixing region are shown to agree with the error function profile typically found in the shear layer. Details of the behavior of the turbulence kinetic energy and the turbulence length scale are also discussed.

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

    NASA Astrophysics Data System (ADS)

    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

  15. Description of coherent structures in the atmospheric boundary layer by model reduction of the surface pressure

    NASA Astrophysics Data System (ADS)

    Lyons, Gregory William

    The flow of coherent turbulent structures into a wind turbine is associated with vibrational blade excitation. Successful forecasting of such turbulent events for control system input would increase the lifetime of turbine components. The coherence of these features suggests description by model reduction. To this end, an array of pressure transducers was deployed on the ground at Reese Technology Center in Lubbock, Texas, and the pressure fluctuations were recorded over nearly two diurnal cycles. A program for computation of the dynamic mode decomposition was developed with special consideration for the case of a non-stationary, nonlinear system. A simulated surface-pressure perturbation was first decomposed, to inform the interpretation of experimental data. Several sets of surface-pressure data were decomposed for various meteorological conditions. The resulting dynamic modes and eigenvalues describe the spatial and temporal coherence of local features in the atmospheric boundary layer. In each case, modes were identified that can be associated with wave-like pressure fluctuations that propagate either at convective or acoustic speeds.

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

    NASA Astrophysics Data System (ADS)

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

    2017-08-01

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

  17. Simulations of Vertical Axis Wind Turbine Farms in the Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Hezaveh, Seyed Hossein; Bou-Zeid, Elie; Lohry, Mark; Martinelli, Luigi

    2014-11-01

    Wind power is an abundant and clean source of energy that is increasingly being tapped to reduce the environmental footprint of anthropogenic activities. The vertical axis wind turbine (VAWT) technology is now being revisited due to some important advantages over horizontal axis wind turbines (HAWTS) that are particularly important for farms deployed offshore or in complex terrain. In this talk, we will present the implementation and testing of an actuator line model (ALM) for VAWTs in a large eddy simulation (LES) code for the atmospheric boundary layer, with the aim of optimizing large VAWT wind farm configurations. The force coefficients needed for the ALM are here obtained from blade resolving RANS simulations of individual turbines for each configuration. Comparison to various experimental results show that the model can very successfully reproduce observed wake characteristic. The influence of VAWT design parameters such as solidity, height to radius ratio, and tip speed ratio (TSR) on these wake characteristics, particularly the velocity deficit profile, is then investigated.

  18. The formation of snow streamers in the turbulent atmosphere boundary layer

    NASA Astrophysics Data System (ADS)

    Huang, Ning; Wang, Zheng-Shi

    2016-12-01

    The drifting snow in the turbulent atmosphere boundary layer is an important type of aeolian multi-phase flow. Current theoretical and numerical studies of drifting snow mostly consider the flow field as steady wind velocity. Whereas, little is known about the effects of turbulent wind structures on saltating snow particles. In this paper, a 3-D drifting snow model based on Large Eddy Simulation is established, in which the trajectory of every snow grain is calculated and the coupling effect between wind field and snow particles is considered. The results indicate that the saltating snow particles are re-organized by the suction effect of high-speed rotating vortexes, which results in the local convergence of particle concentration, known as snow streamers. The turbulent wind leads to the spatial non-uniform of snow particles lifted by aerodynamic entrainment, but this does not affect the formation of snow streamers. Whereas the stochastic grain-bed interactions make a great contribution to the final shapes of snow streamers. Generally, snow streamers display a characteristic length about 0.5 m and a characteristic width of approximately 0.16 m, and their characteristic sizes are not sensitive to the wind speed. Compared to the typical sand streamer, snow streamer is slightly narrower and the occurrence of other complex streamer patterns is later than that of sand streamers due to the better follow performance of snow grains with air flow.

  19. Atmospheric Aerosol and Thermal Structure in the Boundary Layer Over the Los Angeles Basin

    NASA Technical Reports Server (NTRS)

    Johnson, Warren B.

    1973-01-01

    A field study using a mobile lidar was recently conducted in the L. A. Basin, California, to (1) examine the relationship between the vertical aerosol and the thermal structure, and (2) map the vertical aerosol structure in the atmospheric boundary layer over the basin. These data are needed for use in the development of a mixing-depth submodel required for photochemical air Quality simulation models. Toward these ends, a series of lidar aerosol measurements in conjunction with balloon and aircraft temperature soundings were taken at a site in El Monte, and in a mobile mode along a 90-mile freeway loop between El Monte, Santa Monica, and Long Beach. The lidar data are presented in the form of time-height and distance-height cross sections. The results indicate that, although aerosol concentrations are frequently present above the base of the marine inversion, these are generally in stratified layers in contrast to the more uniform nature of the lower convective layer, permitting the mixing depth to be distinguished on this basis. The lidar-derived mixing depths are well correlated (within 100 m) with daytime temperature inversions. Other significant features shown by the lidar data include large Basin-wide mixing-depth variations, waves with amplitudes of 200-300 m and wavelengths of 1000-1500 m on the lower aerosol layer, and apparent aerosol "chimneys" with overrunning in the vicinity of convergence zones.

  20. Flux measurements in the surface Marine Atmospheric Boundary Layer over the Aegean Sea, Greece.

    PubMed

    Kostopoulos, V E; Helmis, C G

    2014-10-01

    Micro-meteorological measurements within the surface Marine Atmospheric Boundary Layer took place at the shoreline of two islands at northern and south-eastern Aegean Sea of Greece. The primary goal of these experimental campaigns was to study the momentum, heat and humidity fluxes over this part of the north-eastern Mediterranean Sea, characterized by limited spatial and temporal scales which could affect these exchanges at the air-sea interface. The great majority of the obtained records from both sites gave higher values up to factor of two, compared with the estimations from the most widely used parametric formulas that came mostly from measurements over open seas and oceans. Friction velocity values from both campaigns varied within the same range and presented strong correlation with the wind speed at 10 m height while the calculated drag coefficient values at the same height for both sites were found to be constant in relation with the wind speed. Using eddy correlation analysis, the heat flux values were calculated (virtual heat fluxes varied from -60 to 40 W/m(2)) and it was found that they are affected by the limited spatial and temporal scales of the responding air-sea interaction mechanism. Similarly, the humidity fluxes appeared to be strongly influenced by the observed intense spatial heterogeneity of the sea surface temperature. Copyright © 2014 Elsevier B.V. All rights reserved.

  1. Atmospheric mercury over the marine boundary layer observed during the third China Arctic Research Expedition.

    PubMed

    Kang, Hui; Xie, Zhouqing

    2011-01-01

    TGM measurements on board ships have proved to provide valuable complementary information to measurements by a ground based monitoring network. During the third China Arctic Research Expedition (from July 11 to September 24, 2008), TGM concentrations over the marine boundary layer along the cruise path were in-situ measured using an automatic mercury vapor analyzer. Here we firstly reported the results in Japan Sea, North Western Pacific Ocean and Bering Sea, where there are rare reports. The value ranged between 0.30 and 6.02 ng/m3 with an average of (1.52 +/- 0.68) ng/m3, being slightly lower than the background value of Northern Hemisphere (1.7 ng/m3). Notably TGM showed considerably spatial and temporal variation. Geographically, the average value of TGM in Bering Sea was higher than those observed in Japan Sea and North Western Pacific Ocean. In the north of Japan Sea TGM levels were found to be l