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Author: James Keith DeBoer
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The validity of linear smoothing of topography for numerical weather prediction and the variation of mountain drag with mountain height and static stability are examined in the study. In the model a constant geostrophic current is perpendicular to the mountain range and the height of the mountain is independent of y. The hydrostatic Boussinesq equations are used with motion bounded at the top by a rigid plane at z = D.A modified coordinate system similar to Phillips' sigma system was used. Solutions were obtained using a smoothed mountain profile. These solutions were compared with smoothed solutions obtained from the unsmoothed mountain. The comparison of these solutions shows that an error is introduced when non-linear terms become sufficiently large. Values of the mountain drag for differing values of mountain height at a given static stability and for differing values of static stability at a given mountain height were computed. Mountain drag was found to vary quadratically with mountain height and linearly with static stability. (Author).
Author: James Keith DeBoer
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The validity of linear smoothing of topography for numerical weather prediction and the variation of mountain drag with mountain height and static stability are examined in the study. In the model a constant geostrophic current is perpendicular to the mountain range and the height of the mountain is independent of y. The hydrostatic Boussinesq equations are used with motion bounded at the top by a rigid plane at z = D.A modified coordinate system similar to Phillips' sigma system was used. Solutions were obtained using a smoothed mountain profile. These solutions were compared with smoothed solutions obtained from the unsmoothed mountain. The comparison of these solutions shows that an error is introduced when non-linear terms become sufficiently large. Values of the mountain drag for differing values of mountain height at a given static stability and for differing values of static stability at a given mountain height were computed. Mountain drag was found to vary quadratically with mountain height and linearly with static stability. (Author).
Author: John Lawrence Hayes
Publisher:
ISBN:
Category : Numerical weather forecasting
Languages : en
Pages : 0
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Book Description
The nature of the interaction of atmospheric flow with a mountain range of finite length is investigated. An inviscid, adiabatic primitive equation model is used to simulate steady, vertically-unsheared flow past a mountain range; various cases of mountain height and width are analyzed. A similar model for two-dimensional Boussinesq flow past a mountain on an f-plane is solved analytically following Merkine (1975) for comparison to the numerical solution. Results indicate that the atmospheric response is quite similar to that observed in the Boussinesq model. Ridging over the mountains and responses which damp in the vertical are observed in both models. Differences are noted in the magnitude of the response in the vicinity of the mountains and in the position of the downstream trough. In addition, the effect of finite difference model grid resolution is investigated by comparing simulations based on differing horizontal and vertical resolution. Results indicate that for larger scale mountains, the effect of poorer horizontal resolution is significant; vertical resolution, however, is relatively unimportant. As the horizontal scale of the mountains is reduced, vertical resolution becomes increasingly more important so that the effects of both horizontal and vertical resolution are significant. (Author).
Author: Miguel A. C. Teixeira
Publisher: Frontiers Media SA
ISBN: 2889450163
Category :
Languages : en
Pages : 162
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Book Description
Mountainous regions occupy a significant fraction of the Earth's continents and are characterized by specific meteorological phenomena operating on a wide range of scales. Being a home to large human populations, the impact of mountains on weather and hydrology has significant practical consequences. Mountains modulate the climate and create micro-climates, induce different types of thermally and dynamically driven circulations, generate atmospheric waves of various scales (known as mountain waves), and affect the boundary layer characteristics and the dispersion of pollutants. At the local scale, strong downslope winds linked with mountain waves (such as the Foehn and Bora) can cause severe damage. Mountain wave breaking in the high atmosphere is a source of Clear Air Turbulence, and lee wave rotors are a major near-surface aviation hazard. Mountains also act to block strongly stratified air layers, leading to the formation of valley cold air-pools (with implications for road safety, pollution, crop damage, etc.) and gap flows. Presently, neither the fine-scale structure of orographic precipitation nor the initiation of deep convection by mountainous terrain can be resolved adequately by regional-to global-scale models, requiring appropriate downscaling or parameterization. Additionally, the shortest mountain waves need to be parameterized in global weather and climate prediction models, because they exert a drag on the atmosphere. This drag not only decelerates the global atmospheric circulation, but also affects temperatures in the polar stratosphere, which control ozone depletion. It is likely that both mountain wave drag and orographic precipitation lead to non-trivial feedbacks in climate change scenarios. Measurement campaigns such as MAP, T-REX, Materhorn, COLPEX and i-Box provided a wealth of mountain meteorology field data, which is only starting to be explored. Recent advances in computing power allow numerical simulations of unprecedented resolution, e.g. LES modelling of rotors, mountain wave turbulence, and boundary layers in mountainous regions. This will lead to important advances in understanding these phenomena, as well as mixing and pollutant dispersion over complex terrain, or the onset and breakdown of cold air pools. On the other hand, recent analyses of global circulation biases point towards missing drag, especially in the southern hemisphere, which may be due to processes currently neglected in parameterizations. A better understanding of flow over orography is also crucial for a better management of wind power and a more effective use of data assimilation over complex terrain. This Research Topic includes contributions that aim to shed light on a number of these issues, using theory, numerical modelling, field measurements, and laboratory experiments.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 580
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Book Description
Author: Jon Ander Arrillaga Mitxelena
Publisher: Springer Nature
ISBN: 303048579X
Category : Mathematics
Languages : en
Pages : 169
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Book Description
This book presents developments of novel techniques and applies them in order to understand the interactions between thermally driven mesoscale flows (sea and mountain breezes) and the turbulent exchange within the atmospheric boundary layer. These interactions are not accurately reproduced in the meteorological models currently employed for weather forecasting. Consequently, important variables such as air temperature and wind speed are misrepresented. Also, the concentrations of relevant greenhouse gases such as CO2 are considerably affected by these interactions. By applying a systematic algorithm based on objective criteria (presented here), the thesis explores complete observational databases spanning up to 10 years. Further, it presents statistically significant and robust results on the topic, which has only been studied in a handful of cases in the extant literature. Lastly, by applying the algorithm directly to the outputs of the meteorological model, the thesis helps readers understand the processes discussed and reveals the biases in such models.
Author: Naval Postgraduate School (U.S.)
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 658
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Book Description
Author: Yayun Qiao
Publisher:
ISBN:
Category : Atmospheric circulation
Languages : en
Pages :
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Book Description
Airflow over complex terrain throughout the atmospheric boundary layer (ABL) governs the transport and mixing of mass, momentum, and heat. Topography causes obstruction of the airflow and generates airflow distortion and turbulence. Perturbations in land-atmosphere interactions cause various weather phenomena like cold-air pools (CAPs) leading to changes in many aspects of weather and climate that impact the optimal position of wind-turbine, forest-fire behavior, and forecasting, as well as trace-gas and pollutant dispersion. This thesis investigates the flow over complex terrain, specifically double-hill terrain, with new numerical model approaches. The first study utilizes the Weather Research and Forecasting (WRF) model with large eddy simulations (LES) and the immersed-boundary method (IBM) to improve the simulations of the flow and recirculation regions over steep double-hill terrain. The gap distance controls the flow distribution behind both hills. The upwind hill has a significant influence on the second hill. When the gap distance is too small, the flow after the upwind hill cannot regain its momentum. The second study examines the flow distribution over a forested double-hill and the impact of the gap distance between two hills on scalar transport (CO2 and H2O). This study uses the WRF-LES model coupled with a new multiple-layer canopy module (MCANOPY module). We find that flow recirculation is the primary factor dominating scalar transport. Scalars are transported and trapped in both recirculation regions and accumulated on the lee sides of both hills. Our simulation shows the occurrence of two vortices on the lee side of the upstream hill enhances the accumulation of scalars in the valleys. In the end, we extend our work from the first study to understand flow patterns over a realistic double-hill topography. Results show that the valley gap distance is so small that the recirculation region in the valley between two hills cannot fully develop. Additionally, the WRF-IBM captures the structure of microscale flows that other models have not captured in the previous studies.
Author: Radyadour Kh. Zeytounian
Publisher: Springer Science & Business Media
ISBN: 3642738001
Category : Science
Languages : en
Pages : 405
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Book Description
The present work is not exactly a "course", but rather is presented as a monograph in which the author has set forth what are, for the most part, his own results; this is particularly true of Chaps. 7-13. Many of the problems dealt with herein have, since the school year 1975-76, been the subject of a series of graduate lectures at the "Universire des Sciences et Techniques de Lille I" for students preparing for the "Diplome d'Etudes Ap profondies de Mecanique (option fluides)". The writing of this book was thus strongly influenced by the author's own conception of meteorology as a fluid mechanics discipline which is in a privi leged area for the application of singular perturbation techniques. It goes without saying that the modeling of atmospheric flows is a vast and complex problem which is presently the focal point of many research projects. The enonnity of the topic explains why many important questions have not been taken up in this work, even among those which are closely related to the subject treated herein. Nonetheless, the author thought it worthwhile for the development of future research on the modeling of atmospheric flows (from the viewpoint of theoretical fluid mechanics) to bring forth a book specifying the problems which have already been resolved in this field and those which are, as yet, unsolved.
Author: M. Abouali
Publisher:
ISBN:
Category :
Languages : en
Pages : 88
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Author: Demetri P Lalas
Publisher: World Scientific
ISBN: 9814602833
Category :
Languages : en
Pages : 768
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Book Description
This volume is a collection of lectures given at the two colloquia on atmospheric flows over complex terrain with applications to wind energy and air pollution, organized and sponsored by ICTP in Trieste, Italy. The colloquia were the result of the recognition of the importance of renewable energy sources, an important aspect which grows yearly as the environmental problems become more pronounced and their effects more direct and intense, while at the same time, the wise management of the Earth's evidently limited resources becomes imperative.It is divided into two main parts. The first, which comprises Chaps. 1 to 4, presents the structure of the atmospheric boundary layer with emphasis in the region adjacent to the ground. The second, Chaps. 5 to 10, discusses methods for the numerical computation of the wind field on an arbitrary terrain. The unique feature of this book is that it does not stop at the theoretical exposition of the analytical and numerical techniques but includes a number of codes, in a diskette, where the mechanisms and techniques presented in the main part are implemented and can be run by the reader. Some of the codes are of instructional value while others can be utilized for simple operational work.Some of the lecturers are: D N Asimakopoulos, C I Aspliden, V R Barros, A K Blackadar, G A Dalu, A de Baas, D Etling, G Furlan, D P Lalas, P J Mason, C F Ratto and F B Smith.
