A Numerical Investigation of the Aerosol Effects on a Mesoscale Convective System PDF Download
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Author: Priyanka Roy
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 0
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Book Description
Mesoscale Convective Systems (MCSs) are frequent occurrences during summer months in mid-west USA and bring almost 30% rainfall to the region. This work investigates the effects of anthropogenic aerosols, like sulfate and black carbon, and natural aerosols like dust on a MCS. The coupled meteorology and chemistry Weather Research and Forecasting-Chemistry (WRF-Chem) version 3.1.1 model was employed for the numerical study of the aerosol effects on MCS. The selected MCS occurred on June 20, 2007 covering large parts of Kansas, Oklahoma and northern Texas. In the WRF-Chem model, the aerosol effects are analyzed by inputting the aerosol optical properties into the shortwave radiation scheme and physical properties into the microphysics scheme. The interaction of aerosols with the incoming shortwave radiation is higher due to the wavelength being similar to particulate sizes found in the atmosphere. The spatial resolution which resolves the features of the MCS reliably well was found by conducting sensitivity studies at coarse and fine resolution. At the coarse resolution (18 km) the MCS was not very well resolved, with delays in cloud and precipitation formation. However, the direct and indirect effects of anthropogenic aerosols were prominent, by showing large scale scattering of the shortwave radiation and by suppressing the precipitation, respectively. The nested domain simulations have higher inner domain resolutions (6 and 1.5 km) and as a result resolved the MCS better than the single coarse resolution simulation. The combined aerosol effects are investigated by increasing the amount of the sulfate, black carbon and dust aerosols, and considering their dominant characteristics. Sulfates are the major constituents of the anthropogenic emissions, and they are scattering and reflecting in nature. On the other hand, black carbon and dust absorb radiation, evaporating clouds and also warming the atmosphere. The dust particulates form giant cloud condensation nuclei (CCN), which can enhance precipitation in the presence of moisture in the atmosphere. The combination of the radiative effects due to each of these aerosols has shown, that scattering due to aerosols is a dominant factor for all the types of aerosols. The presence of aerosols interacting with the microphysics and radiation schemes produces a more organized MCS structure, as well as more liquid and ice clouds. The black carbon particulates do not solely warm the atmosphere, but also prevent a large amount of the solar radiation from reaching the surface. The giant CCN due to dust particles instead of suppressing the precipitation enhances it. Thus, two absorbing aerosols when increased in amounts show very different effects on cloud cover and precipitation during MCS. This is one of the few studies to use coupled chemistry and meteorology model to study the effects of aerosols on MCS. It brings to light the fact that inspite of their concentration, some dominant characteristics of each aerosol type may be lost while others may be emphasized, on the surface energy balance and in the non-linear process of precipitation even during MCS. This work shows that the aerosol concentration and composition are prominent on the surface energy and while the aerosol size and concentration are vital for the precipitation processes.
Author: Priyanka Roy
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 0
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Book Description
Mesoscale Convective Systems (MCSs) are frequent occurrences during summer months in mid-west USA and bring almost 30% rainfall to the region. This work investigates the effects of anthropogenic aerosols, like sulfate and black carbon, and natural aerosols like dust on a MCS. The coupled meteorology and chemistry Weather Research and Forecasting-Chemistry (WRF-Chem) version 3.1.1 model was employed for the numerical study of the aerosol effects on MCS. The selected MCS occurred on June 20, 2007 covering large parts of Kansas, Oklahoma and northern Texas. In the WRF-Chem model, the aerosol effects are analyzed by inputting the aerosol optical properties into the shortwave radiation scheme and physical properties into the microphysics scheme. The interaction of aerosols with the incoming shortwave radiation is higher due to the wavelength being similar to particulate sizes found in the atmosphere. The spatial resolution which resolves the features of the MCS reliably well was found by conducting sensitivity studies at coarse and fine resolution. At the coarse resolution (18 km) the MCS was not very well resolved, with delays in cloud and precipitation formation. However, the direct and indirect effects of anthropogenic aerosols were prominent, by showing large scale scattering of the shortwave radiation and by suppressing the precipitation, respectively. The nested domain simulations have higher inner domain resolutions (6 and 1.5 km) and as a result resolved the MCS better than the single coarse resolution simulation. The combined aerosol effects are investigated by increasing the amount of the sulfate, black carbon and dust aerosols, and considering their dominant characteristics. Sulfates are the major constituents of the anthropogenic emissions, and they are scattering and reflecting in nature. On the other hand, black carbon and dust absorb radiation, evaporating clouds and also warming the atmosphere. The dust particulates form giant cloud condensation nuclei (CCN), which can enhance precipitation in the presence of moisture in the atmosphere. The combination of the radiative effects due to each of these aerosols has shown, that scattering due to aerosols is a dominant factor for all the types of aerosols. The presence of aerosols interacting with the microphysics and radiation schemes produces a more organized MCS structure, as well as more liquid and ice clouds. The black carbon particulates do not solely warm the atmosphere, but also prevent a large amount of the solar radiation from reaching the surface. The giant CCN due to dust particles instead of suppressing the precipitation enhances it. Thus, two absorbing aerosols when increased in amounts show very different effects on cloud cover and precipitation during MCS. This is one of the few studies to use coupled chemistry and meteorology model to study the effects of aerosols on MCS. It brings to light the fact that inspite of their concentration, some dominant characteristics of each aerosol type may be lost while others may be emphasized, on the surface energy balance and in the non-linear process of precipitation even during MCS. This work shows that the aerosol concentration and composition are prominent on the surface energy and while the aerosol size and concentration are vital for the precipitation processes.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 836
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Author: Yuan Wang
Publisher:
ISBN:
Category :
Languages : en
Pages :
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The studies in this dissertation aim at advancing our scientific understandings about physical processes involved in the aerosol-cloud-precipitation interaction and quantitatively assessing the impacts of aerosols on the cloud systems with diverse scales over the globe on the basis of the observational data analysis and various modeling studies. Long-term impacts of aerosols on precipitation and lightning over the Pearl River Delta megacity area in China are identified through the analysis of seven-year measurements of precipitation, lightning flashes, and visibility from 2000 to 2006. The cloud resolving - Weather Research and Forecasting (CR-WRF) model with a two- moment bulk microphysical scheme is employed to simulate a mesoscale convective system in the Guangzhou megacity area and to elucidate the effects of aerosols on cloud processes, precipitation, and lightning activity. The responses of hydrometeors and latent heat release to different aerosol loadings reveal the physical mechanism for the precipitation and lightning enhancement in the Guangzhou megacity area, showing more efficient mixed phase processes and intensified convection under the polluted aerosol condition. Sensitivity modeling experiments are performed for maritime warm stratocumulus clouds over the southeast Pacific Ocean to evaluate the microphysical parameterizations for simulations of the aerosol effects in regional and global climate models. The Morrison double-moment bulk microphysical scheme presently implemented in the WRF model is modified by replacing the fixed aerosols in the original bulk scheme with a prognostic double-moment aerosol representation to predict both aerosol number concentration and mass mixing ratio. The impacts of the parameterizations of diffusional growth and autoconversion of cloud droplets and the selection of the embryonic raindrop radius on the performance of the bulk microphysical scheme are also evaluated. The impacts of Asian pollution outflows on the Pacific storm track are assessed utilizing reanalysis data, a hierarchical modeling approach and the multi-scale aerosol- climate modeling frame. Statistical analysis of two sets of reanalysis data suggests a strengthened trend of the storm track intensity over the North Pacific since 1979. The two-month seasonal simulations using a CR-WRF model with a two-moment bulk microphysics are performed to examine the aerosol effects on the Pacific storm track intensity. Subsequently, the anomalies of the diabatic heating rate by the Asian pollution outflow derived from the CR-WRF simulations have been prescribed in the NACR Community Atmosphere Model (CAM5) to provide the aerosol forcing terms. The forced GCM well reproduces an enhancement in the intensity of storm track, compared to the unforced model simulations. Similarly, under the multi-scale aerosol-climate modeling frame, the comparisons of the simulated present day versus pre-industrial climate corresponding to two different aerosol scenarios indicate the increased precipitation and poleward heat transport for the present-day climate reveal invigorated mid-latitude cyclones. The current work illustrates the complexity of the aerosol effects on the cloud systems at the diverse scales with different meteorological conditions. This study also stresses the importance of accurate representation of aerosol forcings in the different types of atmospheric numerical models for future climate projections. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/151115
Author: PRUPPACHER
Publisher: Birkhäuser
ISBN:
Category : Juvenile Nonfiction
Languages : en
Pages : 386
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Book Description
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: Wendilyn J. Kaufeld
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
As the formative agents of cloud droplets, aerosols play an undeniably important role in the development of clouds and precipitation. Few meteorological models have been developed or adapted to simulate aerosols and their contribution to cloud and precipitation processes. The Weather Research and Forecasting model (WRF) has recently been coupled with an atmospheric chemistry suite and is jointly referred to as WRF-Chem, allowing atmospheric chemistry and meteorology to influence each other0́9s evolution within a mesoscale modeling framework. Provided that the model physics are robust, this framework allows the feedbacks between aerosol chemistry, cloud physics, and dynamics to be investigated. This study focuses on the effects of aerosols on meteorology, specifically, the interaction of aerosol chemical species with microphysical processes represented within the framework of the WRF-Chem. Aerosols are represented by eight size bins using the Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) sectional parameterization, which is linked to the Purdue Lin bulk microphysics scheme. The aim of this study is to examine the sensitivity of deep convective precipitation modeled by the 2D WRF-Chem to varying aerosol number concentration and aerosol type. A systematic study has been performed regarding the effects of aerosols on parameters such as total precipitation, updraft/downdraft speed, distribution of hydrometeor species, and organizational features, within idealized maritime and continental thermodynamic environments. Initial results were obtained using WRFv3.0.1, and a second series of tests were run using WRFv3.2 after several changes to the activation, autoconversion, and Lin et al. microphysics schemes added by the WRF community, as well as the implementation of prescribed vertical levels by the author. The results of WRFv3.2 runs contrasted starkly with WRFv3.0.1 runs. The WRFv3.0.1 runs produced a propagating system resembling a developing squall line, whereas the WRFv3.2 runs did not. The response of total precipitation, updraft/downdraft speeds, and system organization to increasing aerosol concentrations were opposite between runs with different versions of WRF. Results of the WRFv3.2 runs, however, were in better agreement in timing and magnitude of vertical velocity and hydrometeor content with a WRFv3.0.1 run using single-moment Lin et al. microphysics, than WRFv3.0.1 runs with chemistry. One result consistent throughout all simulations was an inhibition in warm-rain processes due to enhanced aerosol concentrations, which resulted in a delay of precipitation onset that ranged from 2-3 minutes in WRFv3.2 runs, and up to 15 minutes in WRFv.3.0.1 runs. This result was not observed in a previous study by Ntelekos et al. (2009) using the WRF-Chem, perhaps due to their use of coarser horizontal and vertical resolution within their experiment. The changes to microphysical processes such as activation and autoconversion from WRFv3.0.1 to WRFv3.2, along with changes in the packing of vertical levels, had more impact than the varying aerosol concentrations even though the range of aerosol tested was greater than that observed in field studies. In order to take full advantage of the input of aerosols now offered by the chemistry module in WRF, the author recommends that a fully double-moment microphysics scheme be linked, rather than the limited double-moment Lin et al. scheme that currently exists. With this modification, the WRF-Chem will be a powerful tool for studying aerosol-cloud interactions and allow comparison of results with other studies using more modern and complex microphysical parameterizations.
Author: Environmental Research Laboratories (U.S.)
Publisher:
ISBN:
Category : Environmental policy
Languages : en
Pages : 234
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Book Description
Author: S. G. Jennings
Publisher: University of Arizona Press
ISBN: 9780816513628
Category : Science
Languages : en
Pages : 324
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Book Description
There is now a growing awareness that, in addition to the well publicized influence of carbon dioxide and other greenhouse gases on the warming of the earth's atmosphere, aerosol particles may also play an important role in forcing climate change. This volume brings together previously unavailable data and interpretative analyses, derived from studies in both the U.S. and U.S.S.R., which review, update, and assess aerosol-related climatic effects.
Author: United States. National Telecommunications and Information Administration
Publisher:
ISBN:
Category : Telecommunication
Languages : en
Pages : 290
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Book Description
Author: Tanvir Islam
Publisher: Elsevier
ISBN: 0128104384
Category : Science
Languages : en
Pages : 366
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Book Description
Remote Sensing of Aerosols, Clouds, and Precipitation compiles recent advances in aerosol, cloud, and precipitation remote sensing from new satellite observations. The book examines a wide range of measurements from microwave (both active and passive), visible, and infrared portions of the spectrum. Contributors are experts conducting state-of-the-art research in atmospheric remote sensing using space, airborne, and ground-based datasets, focusing on supporting earth observation satellite missions for aerosol, cloud, and precipitation studies. A handy reference for scientists working in remote sensing, earth science, electromagnetics, climate physics, and space engineering. Valuable for operational forecasters, meteorologists, geospatial experts, modelers, and policymakers alike. - Presents new approaches in the field, along with further research opportunities, based on the latest satellite data - Focuses on how remote sensing systems can be designed/developed to solve outstanding problems in earth and atmospheric sciences - Edited by a dynamic team of editors with a mixture of highly skilled and qualified authors offering world-leading expertise in the field
