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Author: Mikael K. Witte
Publisher:
ISBN: 9781339956848
Category :
Languages : en
Pages : 153
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Book Description
The third goal of the research presented herein is to implement a high spectral resolution bin microphysics scheme in a large eddy simulation (LES) model. The high resolution scheme is validated by comparison with simulations using the default spectral resolution. Considerable differences in microphysical structure and planetary boundary layer turbulence are found when collision coalescence is active due to artificial acceleration of the process at the default resolution, which causes higher concentrations at large drop sizes than in the high resolution configuration.
Author: Mikael K. Witte
Publisher:
ISBN: 9781339956848
Category :
Languages : en
Pages : 153
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Book Description
The third goal of the research presented herein is to implement a high spectral resolution bin microphysics scheme in a large eddy simulation (LES) model. The high resolution scheme is validated by comparison with simulations using the default spectral resolution. Considerable differences in microphysical structure and planetary boundary layer turbulence are found when collision coalescence is active due to artificial acceleration of the process at the default resolution, which causes higher concentrations at large drop sizes than in the high resolution configuration.
Author: Xue Zheng
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
This dissertation investigates the impacts of meteorological factors and aerosol indirect effects on the costal marine stratocumulus (Sc) variations in the southeast Pacific, a region that has been largely unexplored and is a major challenge of the modeling community, through both observational and numerical studies. This study provides a unique dataset for documenting the characteristics of the marine Sc-topped BL off the coast of Northern Chile. The observational study shows that the boundary layer (BL) over this region was well mixed and topped by a thin and non-drizzling Sc layer on days synoptically-quiescent with little variability between this region and the coast. The surface wind, the surface fluxes and the BL turbulence appeared to be weaker than those over other ocean regions where stratocumulus clouds exist. The weaker turbulence in the BL may contribute to a relatively low entrainment rate calculated from the near cloud top fluxes. This in-situ data set can help us better understand cloud processes within this coastal regime, and also be valuable for the calibration of the satellite retrievals and the evaluation of numerical models operating at a variety of scales. A strong positive correlation between the liquid water path (LWP) and the cloud condensation nuclei (CCN) was observed under similar boundary layer conditions. This correlation cannot be explained by some of the hypotheses based on previous modeling studies. The satellite retrievals obtained upstream one day prior to the flight observations reveal some sign that the clouds under the high CCN concentrations have minimal LWP loss due to precipitation suppression effects. The results from large eddy simulations with a two-momentum bulk microphysics scheme under different idealized environment scenarios based on aircraft observations indicate that 1) the simulated Sc responds more quickly to changes in large-scale subsidence than to those changes in surface fluxes, free-tropospheric humidity, and the BL-top stability; 2) large-scale vertical wind shear clearly induces cloud-top mixing and enhances entrainment rate; 3) the solar radiation could weaken the BL turbulence, reduce the entrainment rate and decouple the BL; and 4) the impact of the reduced cloud sedimentation due to increasing aerosol on the cloud is small.
Author: A. D. Marrs
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: Alexandre Jousse
Publisher:
ISBN:
Category :
Languages : en
Pages : 102
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Book Description
Marine Stratocumulus clouds are prevalent over the eastern boundary of the subtropical oceans (e.g. northeast and southeast Pacific). Due to their shortwave properties, these low clouds significantly impact the regional and global climate. However marine stratocumulus clouds are subject to modeling approximations as well as, numerous uncertainties on the factors contributing to their radiative properties, variability and possible future changes. In this dissertation, we present three regional modeling studies that intend to provide some more understanding to these issues. We first analyze the sensitivity of marine stratocumulus to parameterizations in the Weather Research and Forecasting (WRF) model. We use the southeast Pacific as a testbed region and compare the simulated surface energy fluxes to those measured during VOCALS-REx. Our results show that errors in shortwave fluxes are traceable to errors in liquid water path (LWP). Two mechanisms controlling the LWP in our simulations are diagnosed. The first mechanism involves boundary layer and shallow cumulus schemes, which control moisture available for cloud by regulating boundary layer height. The second mechanism involves microphysics schemes, which control LWP through the production of drizzle. This study demonstrates that when parameterizations are appropriately chosen, the stratocumulus deck and the related surface energy fluxes are reasonably well represented in WRF. In s second study, we take advantage of these advancements to evaluate the importance of aerosol indirect effects on clouds shortwave properties in the northeast Pacific. Satellite retrievals (e.g. MODIS) show that the cloud droplet number concentration is generally high along the U.S. west coast (~300cm-3), while it drops to smaller values further offshore (~50cm-3). Our results highlight the importance of representing accurately this aerosol spatial variability and the associated indirect effects on LWP for realistic shortwave fluxes simulations in the northeast Pacific. Finally, we analyze the marine stratocumulus variability and their possible anthropogenic changes using a suite of dynamically downscaled experiments in the California region. In particular, we develop a methodology that enables a clear identification of the factors contributing to low cloud cover anthropogenic changes. Our results show a systematic reduction in low cloud cover, which is mostly imputable to a reduction of the coupling between boundary layer top and surface. Our analysis suggests that the enhanced decoupling conditions might be at least partially driven by the drying of the free troposphere in comparison to the boundary layer in future climate.
Author: William R. Cotton
Publisher: Academic Press
ISBN: 0080916651
Category : Science
Languages : en
Pages : 826
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Book Description
Storm and Cloud Dynamics focuses on the dynamics of clouds and of precipitating mesoscale meteorological systems. Clouds and precipitating mesoscale systems represent some of the most important and scientifically exciting weather systems in the world. These are the systems that produce torrential rains, severe winds including downburst and tornadoes, hail, thunder and lightning, and major snow storms. Forecasting such storms represents a major challenge since they are too small to be adequately resolved by conventional observing networks and numerical prediction models. - Provides a complete treatment of clouds integrating the analysis of air motions with cloud structure, microphysics, and precipitation mechanics - Describes and explains the basic types of clouds and cloud systems that occur in the atmosphere-fog, stratus, stratocumulus, altocumulus, altostratus, cirrus, thunderstorms, tornadoes, waterspouts, orographically induced clouds, mesoscale convection complexes, hurricanes, fronts, and extratropical cyclones - Summarizes the fundamentals, both observational and theoretical, of atmospheric dynamics, thermodynamics, cloud microphysics, and radar meteorology, allowing each type of cloud to be examined in depth - Integrates the latest field observations, numerical model simulations, and theory - Supplies a theoretical treatment suitable for the advanced undergraduate or graduate level, as well as post-graduate
Author: Constantin Andronache
Publisher: Elsevier
ISBN: 012810550X
Category : Science
Languages : en
Pages : 302
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Book Description
Mixed-Phase Clouds: Observations and Modeling presents advanced research topics on mixed-phase clouds. As the societal impacts of extreme weather and its forecasting grow, there is a continuous need to refine atmospheric observations, techniques and numerical models. Understanding the role of clouds in the atmosphere is increasingly vital for current applications, such as prediction and prevention of aircraft icing, weather modification, and the assessment of the effects of cloud phase partition in climate models. This book provides the essential information needed to address these problems with a focus on current observations, simulations and applications. - Provides in-depth knowledge and simulation of mixed-phase clouds over many regions of Earth, explaining their role in weather and climate - Features current research examples and case studies, including those on advanced research methods from authors with experience in both academia and the industry - Discusses the latest advances in this subject area, providing the reader with access to best practices for remote sensing and numerical modeling
Author: Darko Koračin
Publisher: Springer
ISBN: 3319452290
Category : Science
Languages : en
Pages : 540
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Book Description
This volume presents the history of marine fog research and applications, and discusses the physical processes leading to fog's formation, evolution, and dissipation. A special emphasis is on the challenges and advancements of fog observation and modeling as well as on efforts toward operational fog forecasting and linkages and feedbacks between marine fog and the environment.
Author: Zev Levin
Publisher: Springer Science & Business Media
ISBN: 1402086903
Category : Science
Languages : en
Pages : 399
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Book Description
Life on Earth is critically dependent upon the continuous cycling of water between oceans, continents and the atmosphere. Precipitation (including rain, snow, and hail) is the primary mechanism for transporting water from the atmosphere back to the Earth’s surface. It is also the key physical process that links aspects of climate, weather, and the global hydrological cycle. Changes in precipitation regimes and the frequency of extreme weather events, such as floods, droughts, severe ice/snow storms, monsoon fluctuations and hurricanes are of great potential importance to life on the planet. One of the factors that could contribute to precipitation modification is aerosol pollution from various sources such as urban air pollution and biomass burning. Natural and anthropogenic changes in atmospheric aerosols might have important implications for precipitation by influencing the hydrological cycle, which in turn could feed back to climate changes. From an Earth Science perspective, a key question is how changes expected in climate will translate into changes in the hydrological cycle, and what trends may be expected in the future. We require a much better understanding and hence predictive capability of the moisture and energy storages and exchanges among the Earth’s atmosphere, oceans, continents and biological systems. This book is a review of our knowledge of the relationship between aerosols and precipitation reaching the Earth's surface and it includes a list of recommendations that could help to advance our knowledge in this area.
Author: Jost Heintzenberg
Publisher: Strungmann Forum Reports
ISBN: 9780262012874
Category : Science
Languages : en
Pages : 0
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Book Description
More than half the globe is covered by visible clouds.
Author: Qingfu Liu
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 270
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Book Description
