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Author: William Peter Kustas
Publisher:
ISBN:
Category : Boundary layer (Meteorology)
Languages : en
Pages : 336
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Book Description
Author: William Peter Kustas
Publisher:
ISBN:
Category : Boundary layer (Meteorology)
Languages : en
Pages : 336
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Book Description
Author: Yi Han
Publisher:
ISBN: 9781088395493
Category : Air flow
Languages : en
Pages : 172
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Book Description
The present work establishes a complete process to perform the micro-scale simulations of the neutral atmospheric boundary layer (ABL) flow over realistic terrain with multi-fidelity turbulence modeling approaches, and to validate the numerical predictions with the available on-site wind data. The complex terrain is located within the Chokecherry and Sierra Madre wind farm site which encompasses about 500 square kilometers of rugged and diverse terrain in south-central Wyoming. A robust conditional sampling procedure for the meteorological tower (met-tower) data to identify near-neutral ABL condition based on a criterion of the turbulence intensity is developed. The conditionally averaged wind data on fourteen met-towers is used for the model validation. The ABL flow simulations are conducted based on the OpenFOAM-based simulator for on/offshore wind farm applications (SOWFA) with both RANS and LES turbulence modeling approaches. The turbulent inflow is generated through a two-stage iterative approach using a precursor method. Appropriate boundary conditions are developed to adjust the real flow patterns over the complex terrain. In the RANS approach, a new formulation to calculate the production term in the transport equation for the turbulent kinetic energy (TKE) is developed to greatly reduce the commonly observed nonphysical near-surface TKE peak, and to improve the prediction of law-of-the-wall scaling in the near-surface region. In the LES approach, a low-dissipative, scale-selective discretization scheme is applied to the non-linear convection term of the filtered momentum equation. The aim is to reduce the numerical dissipation arising from the typically adopted upwind-biased schemes while maintaining second-order accuracy. The simulation results from both RANS and LES approaches are qualitatively compared with each other, and quantitatively compared to the conditional met-tower data in terms of the mean, standard deviation and direction of the wind at three about ground levels. The instantaneous flow field and turbulent structures are predicted by the LES approach. Overall, the wind statistic obtained by RANS and LES approaches show reasonable agreement compared to the met-tower data, except for some under-predictions at four met-tower located closer to the main ridge of the hill in a region of strong terrain variations.
Author: J. R. Garratt
Publisher: Cambridge University Press
ISBN: 9780521467452
Category : Mathematics
Languages : en
Pages : 340
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Book Description
The book gives a comprehensive and lucid account of the science of the atmospheric boundary layer (ABL). There is an emphasis on the application of the ABL to numerical modelling of the climate. The book comprises nine chapters, several appendices (data tables, information sources, physical constants) and an extensive reference list. 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 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 subtropical 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 in general circulation models of the atmosphere that are being used for climate simulation.
Author: Mireia Udina Sistach
Publisher:
ISBN:
Category :
Languages : ca
Pages : 176
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Book Description
The atmospheric boundary layer in stably-stratified conditions and over non-homogeneous terrain becomes a complex system with many interactions of physical processes occurring in a wide range of different spatial and temporal scales. During clear sky night-time or in any stably-stratified conditions intermittent turbulent events and gravity waves are usually present in the stable boundary layer (SBL), which can substantially modify the flow structure. In addition, the circulations in stable flows can be strongly driven by the underlying and surrounding topography, generating katabatic winds, density currents and low level jets, which in turn, trigger gravity waves and turbulence. This thesis aims to contribute to a better comprehension of some of the processes and phenomena occurring in the SBL and over complex terrain areas. In order to understand and quantify the unknown atmospheric processes one can distinguish three different procedures that are very well connected: theoretical descriptions, experimental campaigns and numerical modeling. The numerical models allow us to further understand the experimental data, to test the theoretical relationships or to simulate processes which are very difficult to measure. Principally, in this thesis we have used numerical models to deal with the uncertainties that arise in stably-stratified flows and over heterogeneous terrain and to explore the model capabilities and limitations to resolve them. These numerical weather prediction models (NWP) contain the primitive equations of the atmosphere to describe and forecast the flow motions and properties. In this thesis we have employed one of the worldwide known NWP model, the Weather Research and Forecasting (WRF) model, using two different approaches: the mesoscale approximation and the large eddy simulation (LES). While the mesoscale methodology has allowed us to investigate the flow circulation patterns in a wide range of scales, the LES approximation has enabled us to explicitly resolve the turbulence and describe its structure. In this thesis each methodology has been applied to investigate these different purposes. Using the WRF model with the mesoscale approach we have determined the origin of a density current that generated internal gravity waves over the "Centro de Investigaciones de la Baja Atmosfera"(CIBA) site. We have seen that the long distance mesoscale sea-breeze circulation and the night-time katabatic flows originated at the surrounding complex topography were the origin of the density current which generated displacement in the air parcels and periodic oscillations. In this thesis we have also investigated the vertical turbulence structure using the LES approximation of the WRF model. As a previous step, we have first validated the WRF-LES model in the SBL with a reference case by a comparison of the first and second order moments profiles. Using different wind speed initial conditions we reproduce neutrally and stably stratified flows. However, different from the reality, stably stratified flows are strongly coupled with the surface and turbulence is always maintained. We have shown how the turbulence intensity increases sharply with the wind speed at each height above ground but the rate of increase (slope) is not maintained, as we would expect. It seems that the the top domain potential temperature inversion affects the flow turbulence structure over the whole domain. Finally, we have studied topographically generated gravity waves over the Pyrenees and specifically simulated a trapped lee wave event using the mesoscale approximation with WRF. We have seen that the model is able to reproduce the gravity waves at the lee side of the mountain range with periodic oscillations in all magnitudes. We have seen that 1-km horizontal resolution is necessary to capture the wave field. We have also showed that upstream conditions have to be well represented to capture the adequate wave characteristics.
Author: Yu Song
Publisher:
ISBN:
Category : Atmospheric circulation
Languages : en
Pages : 264
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Book Description
Author: Hadassah Kaplan
Publisher: Springer Science & Business Media
ISBN: 9400965141
Category : Science
Languages : en
Pages : 480
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Book Description
In this volume, we present the lectures given during the 1984 OHOLO Conference, held in Zichron Yaacov, Israel. The Conference was organized by the Israel Institute for Biological Research, Department of Mathematics, which is involved in Environmental Risk Evaluation, and in Projects Estimating the Potential of Wind Energy. The lectures cover a broad spectrum of mathematical models, ranging from those that deal with the solution of atmospheric conservation equations, and to those models that yield empirical estimates based on real time measure ments and thus are unique to the locale where measured. The goal of the Conference was to allow scientists from various countries to meet and discuss topics of mutual interest, including the following: 1. Structure of the boundary layer - primarily models dealing in the understanding of the various processes of atmospheric energy transfer, and their influence on the size and composition of the boundary 1 ayer. 2. Advanced mathematical techniques for describing flow and diffusion - lectures on approximations and techniques for solving the diffu sion and transport equations. 3. Flow over complex terrain - research into various aspects of the problem - mathematical models, physical models, experimental results. 4. Models of pollution transport and deposition.
Author: Mathias W. Rotach
Publisher: Elsevier
ISBN: 032395958X
Category : Science
Languages : en
Pages : 0
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Book Description
Ideal and Real Atmospheric Boundary Layers is based on the notion that classical books of Boundary Layer Meteorology largely focus on ideal surface conditions, while the actual real circumstances often address situations that are more complex, like over heterogeneous land and in urban and mountain areas. Ideal and Real Atmospheric Boundary Layers starts by covering the basic physical principles used in atmospheric boundary layer meteorology, including atmospheric turbulence, observing and modeling atmospheric boundary layers, and neutral, convective, and stable boundary layers over different types of land surfaces. The second part of the book describes the applications and extension of these principles for real-world circumstances. The book will be of interest to researchers and students in atmospheric science, climate science, and meteorology. - Covers state of current research into ideal and real boundary layers - Includes methods and applications of the principles covered in the book - Features highly visual content, including infographics to further exemplify principles and applications covered in the text
Author: Massimiliano Burlando
Publisher:
ISBN:
Category :
Languages : en
Pages : 192
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Book Description
Author: Jens-Christopher Mayer
Publisher:
ISBN:
Category :
Languages : en
Pages : 86
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Author: Katherine Ann Lundquist
Publisher:
ISBN:
Category :
Languages : en
Pages : 358
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Book Description
Mesoscale models, such as the Weather Research and Forecasting (WRF) model, are increasingly used for high resolution simulations, particularly in complex terrain, but errors associated with terrain-following coordinates degrade the accuracy of the solution. Use of an alternative Cartesian gridding technique, known as an immersed boundary method (IBM), alleviates coordinate transformation errors and eliminates restrictions on terrain slope which currently limit mesoscale models to slowly varying terrain. In this dissertation, an immersed boundary method is developed for use in numerical weather prediction. Use of the method facilitates explicit resolution of complex terrain, even urban terrain, in the WRF mesoscale model. First, the errors that arise in the WRF model when complex terrain is present are presented. This is accomplished using a scalar advection test case, and comparing the numerical solution to the analytical solution. Results are presented for different orders of advection schemes, grid resolutions and aspect ratios, as well as various degrees of terrain slope. For comparison, results from the same simulation are presented using the IBM. Both two-dimensional and three-dimensional immersed boundary methods are then described, along with details that are specific to the implementation of IBM in the WRF code. Our IBM is capable of imposing both Dirichlet and Neumann boundary conditions. Additionally, a method for coupling atmospheric physics parameterizations at the immersed boundary is presented, making IB methods much more functional in the context of numerical weather prediction models. The two-dimensional IB method is verified through comparisons of solutions for gentle terrain slopes when using IBM and terrain-following grids. The canonical case of flow over a Witch of Agnesi hill provides validation of the basic no-slip and zero gradient boundary conditions. Specified diurnal heating in a valley, producing anabatic winds, is used to validate the 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.
