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Author : Juwon Kim
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (111 download)
Download or read book The Impact of Aerosols on Cloud Microphysics and Dynamics in Deep Convective Clouds Over the UK. written by Juwon Kim and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Parameterizations of Cloud Microphysics and Indirect Aerosol Effects written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 1. OVERVIEW Aerosols and especially their effect on clouds are one of the key components of the climate system and the hydrological cycle [Ramanathan et al., 2001]. Yet, the aerosol effect on clouds remains largely unknown and the processes involved not well understood. A recent report published by the National Academy of Science states "The greatest uncertainty about the aerosol climate forcing - indeed, the largest of all the uncertainties about global climate forcing - is probably the indirect effect of aerosols on clouds [NRC, 2001]." The aerosol effect on clouds is often categorized into the traditional "first indirect (i.e., Twomey)" effect on the cloud droplet sizes for a constant liquid water path [Twomey, 1977] and the "semi-direct" effect on cloud coverage [e.g., Ackerman et al., 2000]. Enhanced aerosol concentrations can also suppress warm rain processes by producing a narrow droplet spectrum that inhibits collision and coalescence processes [e.g., Squires and Twomey, 1961; Warner and Twomey, 1967; Warner, 1968; Rosenfeld, 1999]. The aerosol effect on precipitation processes, also known as the second type of aerosol indirect effect [Albrecht, 1989], is even more complex, especially for mixed-phase convective clouds. Table 1 summarizes the key observational studies identifying the microphysical properties, cloud characteristics, thermodynamics and dynamics associated with cloud systems from high-aerosol continental environments. For example, atmospheric aerosol concentrations can influence cloud droplet size distributions, warm-rain process, cold-rain process, cloud-top height, the depth of the mixed phase region, and occurrence of lightning. In addition, high aerosol concentrations in urban environments could affect precipitation variability by providing an enhanced source of cloud condensation nuclei (CCN). Hypotheses have been developed to explain the effect of urban regions on convection and precipitation [van den Heever and Cotton, 2007 and Shepherd, 2005]. Recently, a detailed spectral-bin microphysical scheme was implemented into the Goddard Cumulus Ensemble (GCE) model. Atmospheric aerosols are also described using number density size-distribution functions. A spectral-bin microphysical model is very expensive from a computational point of view and has only been implemented into the 2D version of the GCE at the present time. The model is tested by studying the evolution of deep tropical clouds in the west Pacific warm pool region and summertime convection over a mid-latitude continent with different concentrations of CCN: a low "clean" concentration and a high "dirty" concentration. The impact of atmospheric aerosol concentration on cloud and precipitation will be investigated. 2. MODEL DESCRIPTION AND CASE STUDIES 2.1 GCE MODEL The model used in this study is the 2D version of the GCE model. Modeled flow is anelastic. Second- or higher-order advection schemes can produce negative values in the solution. Thus, a Multi-dimensional Positive Definite Advection Transport Algorithm (MPDATA) has been implemented into the model. All scalar variables (potential temperature, water vapor, turbulent coefficient and all five hydrometeor classes) use forward time differencing and the MPDATA for advection. Dynamic variables, u, v and w, use a second-order accurate advection scheme and a leapfrog time integration (kinetic energy semi-conserving method). Short-wave (solar) and long-wave radiation as well as a subgrid-scale TKE turbulence scheme are also included in the model. Details of the model can be found in Tao and Simpson (1993) and Tao et al. (2003). 2.2 Microphysics (Bin Model) The formulation of the explicit spectral-bin microphysical processes is based on solving stochastic kinetic equations for the size distribution functions of water droplets (cloud droplets and raindrops), and six types of ice particles: pristine ice crystals (columnar and plate-like), snow (dendrites and aggregates), graupel and frozen drops ...
Author : Yuan Wang
Publisher : Springer
ISBN 13 : 3662471752
Total Pages : 100 pages
Book Rating : 4.6/5 (624 download)
Download or read book Aerosol-Cloud Interactions from Urban, Regional, to Global Scales written by Yuan Wang and published by Springer. This book was released on 2015-05-05 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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. As recognized in the Fifth Assessment Report by the Inter-government Panel on Climate Change, the magnitude of radiative forcing by atmospheric aerosols is highly uncertain, representing the largest uncertainty in projections of future climate by anthropogenic activities. By using a newly implemented cloud microphysical scheme in the cloud-resolving model, the thesis assesses aerosol-cloud interaction for distinct weather systems, ranging from individual cumulus to mesoscale convective systems. This thesis also introduces a novel hierarchical modeling approach that solves a long outstanding mismatch between simulations by regional weather models and global climate models in the climate modeling community. More importantly, the thesis provides key scientific solutions to several challenging questions in climate science, including the global impacts of the Asian pollution. As scientists wrestle with the complexities of climate change in response to varied anthropogenic forcing, perhaps no problem is more challenging than the understanding of the impacts of atmospheric aerosols from air pollution on clouds and the global circulation.
Author : Amy Yu
Publisher :
ISBN 13 : 9781658413855
Total Pages : pages
Book Rating : 4.4/5 (138 download)
Download or read book An Investigation of Mechanisms of Aerosol-induced Invigoration in Deep Convection written by Amy Yu and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Clouds are an important component of Earth's climate and hydrological system. Aerosols play a critical role in cloud formation by acting as cloud condensation nuclei. Altering aerosol properties would arguably have impacts on the microphysics and dynamics of the cloud formation process. In particular, deep convective clouds (DCCs) are comprised of three major regions-warm, mixed-phase, and cold. The complex structure of DCCs reflects on the behavior of DCCs in response to changes in aerosol loading. Studies done by others have proposed various hypotheses, some of which conflict with one another, on the microphysical and dynamic effects aerosols have on DCCs. The lack of consensus illustrates a need to collectively assess these hypotheses. In this study, a deep convective storm is simulated using RAMS to explore the microphysics and dynamics of DCCs under different environmental conditions and with varying aerosol concentrations. Consistent with many studies, analysis of simulations in this study generally show an increase in average updraft speeds in response to aerosol loading. Specifically, this study investigates three hypotheses found in literature: freeze-based aerosol invigoration, condensate loading, and condensation-based aerosol invigoration. Through a series of mechanism denial tests, results show supersaturation to be most strongly tied to the aerosol-induced invigoration process. This study also addresses the possibility of impacts from smaller sized aerosol particles and secondary activation on deep convection. The influences of secondary activation on updraft speeds remain inconclusive as results appear to be dependent on environmental conditions. Meanwhile, the impacts of Aitken mode aerosols are found to be considerably smaller on convective invigoration compared to accumulation mode aerosols. From a broader perspective, this study calls for more consideration to details when parameterizing convective schemes.
Author : Constantin Andronache
Publisher : Elsevier
ISBN 13 : 012810550X
Total Pages : 302 pages
Book Rating : 4.1/5 (281 download)
Download or read book Mixed-Phase Clouds written by Constantin Andronache and published by Elsevier. This book was released on 2017-09-28 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 : Y. Calisesi
Publisher : Springer
ISBN 13 : 9780387483399
Total Pages : 474 pages
Book Rating : 4.4/5 (833 download)
Download or read book Solar Variability and Planetary Climates written by Y. Calisesi and published by Springer. This book was released on 2007-04-06 with total page 474 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides an updated overview of the processes determining the influence of solar forcing on climate. It discusses in particular the most recent developments regarding the role of aerosols in the climate system and the new insights that could be gained from the investigation of terrestrial climate analogues. The book’s structure mirrors that of the ISSI workshop held in Bern in June 2005.
Author : H.R. Pruppacher
Publisher : Springer Science & Business Media
ISBN 13 : 9780792344094
Total Pages : 984 pages
Book Rating : 4.3/5 (44 download)
Download or read book Microphysics of Clouds and Precipitation written by H.R. Pruppacher and published by Springer Science & Business Media. This book was released on 1996-12-31 with total page 984 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cloud physics has achieved such a voluminous literature over the past few decades that a significant quantitative study of the entire field would prove unwieldy. This book concentrates on one major aspect: cloud microphysics, which involves the processes that lead to the formation of individual cloud and precipitation particles. Common practice has shown that one may distinguish among the following addi tional major aspects: cloud dynamics, which is concerned with the physics respon sible for the macroscopic features of clouds; cloud electricity, which deals with the electrical structure of clouds and the electrification processes of cloud and precipi tation particles; and cloud optics and radar meteorology, which describe the effects of electromagnetic waves interacting with clouds and precipitation. Another field intimately related to cloud physics is atmospheric chemistry, which involves the chemical composition ofthe atmosphere and the life cycle and characteristics of its gaseous and particulate constituents. In view of the natural interdependence of the various aspects of cloud physics, the subject of microphysics cannot be discussed very meaningfully out of context. Therefore, we have found it necessary to touch briefly upon a few simple and basic concepts of cloud dynamics and thermodynamics, and to provide an account of the major characteristics of atmospheric aerosol particles. We have also included a separate chapter on some of the effects of electric fields and charges on the precipitation-forming processes.
Author : Jiwen Fan
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (61 download)
Download or read book Effects of Aerosols on Deep Convective Cumulus Clouds written by Jiwen Fan and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This work investigates the effects of anthropogenic aerosols on deep convective clouds and the associated radiative forcing in the Houston area. The Goddard Cumulus Ensemble model (GCE) coupled with a spectral-bin microphysics is employed to investigate the aerosol effects on clouds and precipitation. First, aerosol indirect effects on clouds are separately investigated under different aerosol compositions, concentrations and size distributions. Then, an updated GCE model coupled with the radiative transfer and land surface processes is employed to investigate the aerosol radiative effects on deep convective clouds. The cloud microphysical and macrophysical properties change considerably with the aerosol properties. With varying the aerosol composition from only (NH4)2SO4, (NH4)2SO4 with soluble organics, to (NH4)2SO4 with slightly soluble organics, the number of activated aerosols decreases gradually, leading to a decrease in the cloud droplet number concentration (CDNC) and an increase in the droplet size. Ice processes are more sensitive to the changes of aerosol chemical properties than the warm rain processes. The most noticeable effect of increasing aerosol number concentrations is an increase of CDNC and cloud water content but a decrease in droplet size. It is indicated that the aerosol indirect effect on deep convection is more pronounced in relatively clean air than in heavily polluted air. The aerosol effects on clouds are strongly dependent on RH: the effect is very significant in humid air. Aerosol radiative effects (ARE) on clouds are very pronounced for mid-visible single-scattering albedo (SSA) of 0.85. Relative to the case without the ARE, cloud fraction and optical depth decrease by about 18% and 20%, respectively. The daytime-mean direct forcing is about 2.2 W m-2 at the TOA and -17.4 W m-2 at the surface. The semi-direct forcing is positive, about 10 and 11.2 W m-2 at the TOA and surface, respectively. Aerosol direct and semi-direct effects are very sensitive to SSA. The cloud fraction, optical depth, convective strength, and precipitation decrease with the increase of absorption, resulting from a more stable atmosphere due to enhanced surface cooling and atmospheric heating.
Author : Pao K. Wang
Publisher : Cambridge University Press
ISBN 13 : 1107005566
Total Pages : 469 pages
Book Rating : 4.1/5 (7 download)
Download or read book Physics and Dynamics of Clouds and Precipitation written by Pao K. Wang and published by Cambridge University Press. This book was released on 2013-03-14 with total page 469 pages. Available in PDF, EPUB and Kindle. Book excerpt: New textbook on microphysics, thermodynamics and cloud-scale dynamics of clouds and precipitation, for graduate and advanced undergraduate students, researchers and professionals.
Author : Wei-Kuo Tao
Publisher :
ISBN 13 :
Total Pages : 62 pages
Book Rating : 4.:/5 (798 download)
Download or read book Impact of Aerosols on Convective Clouds and Precipitation written by Wei-Kuo Tao and published by . This book was released on 2012 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aerosols are a critical factor in the atmospheric hydrological cycle and radiation budget. As a major agent for clouds to form and a significant attenuator of solar radiation, aerosols affect climate in several ways. Current research suggests that aerosol effects on clouds could further extend to precipitation, both through the formation of cloud particles and by exerting persistent radiative forcing on the climate system that disturbs dynamics. However, the various mechanisms behind these effects, in particular, the ones connected to precipitation, are not yet well understood. The atmospheric and climate communities have long been working to gain a better grasp of these critical effects and hence to reduce the significant uncertainties in climate prediction resulting from such a lack of adequate knowledge. Here we review past efforts and summarize our current understanding of the effect of aerosols on convective precipitation processes from theoretical analysis of microphysics, observational evidence, and a range of numerical model simulations. In addition, the discrepancies between results simulated by models, as well as those between simulations and observations, are presented. Specifically, this paper addresses the following topics: (1) fundamental theories of aerosol effects on microphysics and precipitation processes, (2) observational evidence of the effect of aerosols on precipitation processes, (3) signatures of the aerosol impact on precipitation from large-scale analyses, (4) results from cloud-resolving model simulations, and (5) results from large-scale numerical model simulations. Finally, several future research directions for gaining a better understanding of aerosol-cloud-precipitation interactions are suggested.
Author : Wendilyn J. Kaufeld
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (774 download)
Download or read book Toward Assessing the Effects of Aerosols on Deep Convection: a Numerical Study Using the WRF-Chemistry Model written by Wendilyn J. Kaufeld and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 : Deepak Waman
Publisher :
ISBN 13 : 9789189187252
Total Pages : 0 pages
Book Rating : 4.1/5 (872 download)
Download or read book Mechanisms for the Influence from Ice Nucleus Aerosols on Clouds and Their Indirect Effects: Clous Modelling written by Deepak Waman and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The role of multiple groups of primary biological aerosol particles (PBAPs) as ice nucleating particles (INPs), and of ice formation processes such as time-dependent freezing of various INPs, and various secondary ice production (SIP) mechanisms in overall ice concentration has been evaluated in a range of cloud systems by simulating them numerically with the state-of-the-art 'Aerosol-Cloud' (AC) model in a 3D mesoscale domain. Also, the mechanisms of aerosol indirect effects (AIEs) arising from anthropogenic INPs, and the responses to these AIEs from time-dependent INP freezing and SIP processes are investigated in the simulated clouds. The cloud systems simulated with AC are: events of summertime deep convection observed over Oklahoma, USA during the Midlatitude Continental Convective Cloud Experiment (MC3E) in 2011 on 1) 11 May, and 2) 20 May, and wintertime 3) orographic clouds observed during the Atmospheric Radiation Measurement Cloud Aerosol Precipitation Experiment (ACAPEX) on 07 February 2015 over North California, and 4) supercooled layer clouds observed over Larkhill, UK, during the Aerosol Properties, Processes And Influences on the Earth's climate (APPRAISE) campaign on 18 February 2009. AC uses the dynamical core of the Weather Research and Forecasting (WRF) model, modified Geophysical Fluid Dynamic Laboratory (GFDL) radiation scheme, and hybrid bin-bulk microphysics scheme. AC is validated adequately with the coincident aircraft, ground-based, and satellite observations for all four cases. AC forms secondary ice through the Hallett-Mossop (HM) process of rime-splintering, and fragmentation during ice-ice collisions, raindrop freezing, and sublimation of dendritic snow and graupel. A measure of SIP is defined using the term 'ice enhancement' (IE) ratio which is the ratio between the number concentration of total ice particles and active INPs at cloud tops. For both cases in MC3E, overall, PBAPs have little effect (+1-6%) on the cloud-liquid (droplet mean sizes, number concentrations, and their water contents) properties, overall ice concentration, and on precipitation. AC predicts the activity of various INPs with an empirical parameterization (EP). The EP is modified to represent the time-dependent approach of INP freezing in light of our published laboratory observations. It is predicted that the time dependence of INP freezing is not the main cause for continuous ice nucleation and precipitation in all simulated cases. Rather, the main mechanism of precipitation formation is the combination of various SIP mechanisms (in convection) and recirculation-reactivation of dust particles (in APPRAISE layer cloud episode). Also, for all cases, the inclusion of time dependence of INP freezing causes little increase (about 10-20%) in the total ice concentration and ice from all SIP. Regarding SIP, in young developing convective clouds of MC3E (11 May), with tops > −15oC, the initial explosive growth is from the fast HM process, creating IE ratios as high as 103. By contrast, in mature convective clouds (tops
Author : Max Heikenfeld
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (114 download)
Download or read book Aerosol Effects on Microphysical Processes and Deep Convective Clouds written by Max Heikenfeld and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Udaya Bhaskar Gunturu
Publisher :
ISBN 13 :
Total Pages : 184 pages
Book Rating : 4.:/5 (651 download)
Download or read book Aerosol-Cloud Interactions written by Udaya Bhaskar Gunturu and published by . This book was released on 2010 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: (cont.) low or high, they are comparatively less efficient. As the most important part of our study, we examine the response of deep convection to changing initial aerosol concentration. Different aerosol concentrations from those representing pristine to polluted atmospheres are considered. We look at the buoyancy of the cloud and the microphysical evolution. It is found that the dynamics and microphysics are tightly coupled and we infer that to understand aerosol-cloud interactions in deep convective clouds, both - dynamics and microphysics - and their interaction have to be taken into consideration. Our results show that the response of a deep convective cloud to changing aerosol concentration is very different from the much well understood reponse of shallow clouds or small cumulus clouds. In general, increase in aerosol concentratin is seen to invigorate convection and lead to greater condensate. Although the cloud droplet size decreases, collision-coalescence is not completely inefficient. The precipitation in high aerosol regime is seen to occure in short spells of intense rain. A very interesting anomalous response of deep convection to initial aerosol concentration is observed at intermediate aerosol concentrations. The cloud lifetime, and precipitation are seen to increase in this regime. A possible mechanism to explain this anomalous behavior is proposed and the available circumstantial support for the mechanism from extant observations is presented. It is proposed that the efficient collection of rain and cloud droplets by ice and graupel particles in the middle troposphere is primarily responsible for this increased cloud lifetime and precipitation.
Author : Deepak Waman
Publisher :
ISBN 13 : 9789189187269
Total Pages : 0 pages
Book Rating : 4.1/5 (872 download)
Download or read book Mechanisms for the Influence from Ice Nucleus Aerosols on Clouds and Their Indirect Effects: Cloud Modelling written by Deepak Waman and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The role of multiple groups of primary biological aerosol particles (PBAPs) as ice nucleating particles (INPs), and of ice formation processes such as time-dependent freezing of various INPs, and various secondary ice production (SIP) mechanisms in overall ice concentration has been evaluated in a range of cloud systems by simulating them numerically with the state-of-the-art 'Aerosol-Cloud' (AC) model in a 3D mesoscale domain. Also, the mechanisms of aerosol indirect effects (AIEs) arising from anthropogenic INPs, and the responses to these AIEs from time-dependent INP freezing and SIP processes are investigated in the simulated clouds. The cloud systems simulated with AC are: events of summertime deep convection observed over Oklahoma, USA during the Midlatitude Continental Convective Cloud Experiment (MC3E) in 2011 on 1) 11 May, and 2) 20 May, and wintertime 3) orographic clouds observed during the Atmospheric Radiation Measurement Cloud Aerosol Precipitation Experiment (ACAPEX) on 07 February 2015 over North California, and 4) supercooled layer clouds observed over Larkhill, UK, during the Aerosol Properties, Processes And Influences on the Earth's climate (APPRAISE) campaign on 18 February 2009. AC uses the dynamical core of the Weather Research and Forecasting (WRF) model, modified Geophysical Fluid Dynamic Laboratory (GFDL) radiation scheme, and hybrid bin-bulk microphysics scheme. AC is validated adequately with the coincident aircraft, ground-based, and satellite observations for all four cases. AC forms secondary ice through the Hallett-Mossop (HM) process of rime-splintering, and fragmentation during ice-ice collisions, raindrop freezing, and sublimation of dendritic snow and graupel. A measure of SIP is defined using the term 'ice enhancement' (IE) ratio which is the ratio between the number concentration of total ice particles and active INPs at cloud tops. For both cases in MC3E, overall, PBAPs have little effect (+1-6%) on the cloud-liquid (droplet mean sizes, number concentrations, and their water contents) properties, overall ice concentration, and on precipitation. AC predicts the activity of various INPs with an empirical parameterization (EP). The EP is modified to represent the time-dependent approach of INP freezing in light of our published laboratory observations. It is predicted that the time dependence of INP freezing is not the main cause for continuous ice nucleation and precipitation in all simulated cases. Rather, the main mechanism of precipitation formation is the combination of various SIP mechanisms (in convection) and recirculation-reactivation of dust particles (in APPRAISE layer cloud episode). Also, for all cases, the inclusion of time dependence of INP freezing causes little increase (about 10-20%) in the total ice concentration and ice from all SIP. Regarding SIP, in young developing convective clouds of MC3E (11 May), with tops > −15oC, the initial explosive growth is from the fast HM process, creating IE ratios as high as 103. By contrast, in mature convective clouds (tops
Author : Peter V. Hobbs
Publisher : Academic Press
ISBN 13 : 0080959962
Total Pages : 259 pages
Book Rating : 4.0/5 (89 download)
Download or read book Aerosol-Cloud-Climate Interactions written by Peter V. Hobbs and published by Academic Press. This book was released on 1993-07-22 with total page 259 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aerosol and clouds play important roles in determining the earth's climate, in ways that we are only beginning to comprehend. In conjunction with molecular scattering from gases, aerosol and clouds determine in part what fraction of solar radiation reaches the earth's surface, and what fraction of the longwave radiation from the earth escapes to space. This book provides an overview of the latest research on atmospheric aerosol and clouds and their effects on global climate. Subjects reviewed include the direct and indirect effects of aerosol on climate, the radiative properties of clouds and their effects on the Earth's radiation balance, the incorporation of cloud effects in numerical weather prediction models, and stratospheric aerosol and clouds.
Author : Daniel A. Brown
Publisher :
ISBN 13 :
Total Pages : 246 pages
Book Rating : 4.:/5 (642 download)
Download or read book Effects of Aerosols on the Properties of Deep Convective Clouds written by Daniel A. Brown and published by . This book was released on 2010 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aerosols are tiny particles that serve as nuclei for cloud droplet and ice crystal formation. Increases in aerosol concentration lead to clouds with smaller but more numerous droplets. Some recent studies have found evidence that ice crystal size in deep convective clouds is also reduced by elevated aerosol concentrations. In this study, aerosol, cloud, and radiation data in the Clouds and Earth's Radiant Energy System (CERES) Single Satellite Footprint (SSF) datastream are used to examine the findings of the earlier studies. Three years of CERES observations were used to survey the Earth for aerosols and deep convective clouds. A CERES field of view (FOV) was taken to contain a deep convective cloud if the 11-micron brightness temperature was below 210 K. To ensure that the cloud was in a region of active convection, the cloud had to be opaque at 11 microns. South America, Equatorial Africa, and the Northern Indian Ocean exhibited relatively high frequencies of deep convective clouds and contained high aerosol burdens. For each day, within each geographic region, 2° x 2° latitude x longitude regions that contained both deep convective clouds and aerosol retrievals were examined. If within a 10° x 10° region on a given day, two or more of the 2° x 2° regions were found, the differences in the properties of the clouds collocated with the large and small aerosol burdens were calculated. Differences in cloud properties were compared to simultaneous differences in aerosol burdens. This strategy ensured that the clouds and aerosols existed simultaneously and that the clouds with large aerosol burdens shared similar large-scale meteorology as those with small aerosol burdens. No link was found between the differences in aerosol burdens and deep convective cloud properties in any of the regions and seasons analyzed. Relationships among ice crystal size, cloud optical depth, and 11-micron brightness temperature were also investigated. Ice crystal diameter was found to decrease with decreasing cloud temperature. Likewise, cloud optical depth increased with decreasing cloud temperature. Such relationships among cloud properties and the inclusion of semitransparent clouds in earlier studies may explain why the findings of this study differ from those of earlier studies.
