Effects Of Aerosols On The Properties Of Deep Convective Clouds

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Effects of Aerosols on the Properties of Deep Convective Clouds

Author : Daniel A. Brown
Publisher :
ISBN 13 :
Total Pages : 246 pages
Book Rating : 4.:/5 (642 download)

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Book Synopsis Effects of Aerosols on the Properties of Deep Convective Clouds by : Daniel A. Brown

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.

Effects of Aerosols on Deep Convective Cumulus Clouds

Author : Jiwen Fan
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (61 download)

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Book Synopsis Effects of Aerosols on Deep Convective Cumulus Clouds by : Jiwen Fan

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.

Mixed-Phase Clouds

Author : Constantin Andronache
Publisher : Elsevier
ISBN 13 : 012810550X
Total Pages : 302 pages
Book Rating : 4.1/5 (281 download)

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Book Synopsis Mixed-Phase Clouds by : Constantin Andronache

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

An Investigation of Mechanisms of Aerosol-induced Invigoration in Deep Convection

Author : Amy Yu
Publisher :
ISBN 13 : 9781658413855
Total Pages : pages
Book Rating : 4.4/5 (138 download)

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Book Synopsis An Investigation of Mechanisms of Aerosol-induced Invigoration in Deep Convection by : Amy Yu

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.

Cloud Dynamics

Author : PRUPPACHER
Publisher : Birkhäuser
ISBN 13 :
Total Pages : 386 pages
Book Rating : 4.:/5 (31 download)

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Book Synopsis Cloud Dynamics by : PRUPPACHER

Download or read book Cloud Dynamics written by PRUPPACHER and published by Birkhäuser. This book was released on 1976 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Chapter 3

Author :
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (727 download)

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Book Synopsis Chapter 3 by :

Download or read book Chapter 3 written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Any attempt to reconcile observed surface temperature changes within the last 150 years to changes simulated by climate models that include various atmospheric forcings is sensitive to the changes attributed to aerosols and aerosol-cloud-climate interactions, which are the main contributors that may well balance the positive forcings associated with greenhouse gases, absorbing aerosols, ozone related changes, etc. These aerosol effects on climate, from various modeling studies discussed in Menon (2004), range from +0.8 to -2.4 W m−2, with an implied value of -1.0 W m−2 (range from -0.5 to -4.5 W m−2) for the aerosol indirect effects. Quantifying the contribution of aerosols and aerosol-cloud interactions remain complicated for several reasons some of which are related to aerosol distributions and some to the processes used to represent their effects on clouds. Aerosol effects on low lying marine stratocumulus clouds that cover much of the Earth's surface (about 70%) have been the focus of most of prior aerosol-cloud interaction effect simulations. Since cumulus clouds (shallow and deep convective) are short lived and cover about 15 to 20% of the Earth's surface, they are not usually considered as radiatively important. However, the large amount of latent heat released from convective towers, and corresponding changes in precipitation, especially in biomass regions due to convective heating effects (Graf et al. 2004), suggest that these cloud systems and aerosol effects on them, must be examined more closely. The radiative heating effects for mature deep convective systems can account for 10-30% of maximum latent heating effects and thus cannot be ignored (Jensen and Del Genio 2003). The first study that isolated the sensitivity of cumulus clouds to aerosols was from Nober et al. (2003) who found a reduction in precipitation in biomass burning regions and shifts in circulation patterns. Aerosol effects on convection have been included in other models as well (cf. Jacobson, 2002) but the relative impacts on convective and stratiform processes were not separated. Other changes to atmospheric stability and thermodynamical quantities due to aerosol absorption are also known to be important in modifying cloud macro/micro properties. Linkages between convection and boreal biomass burning can also impact the upper troposphere and lower stratosphere, radiation and cloud microphysical properties via transport of tropospheric aerosols to the lower stratosphere during extreme convection (Fromm and Servranckx 2003). Relevant questions regarding the impact of biomass aerosols on convective cloud properties include the effects of vertical transport of aerosols, spatial and temporal distribution of rainfall, vertical shift in latent heat release, phase shift of precipitation, circulation and their impacts on radiation. Over land surfaces, a decrease in surface shortwave radiation ((almost equal to) 3-6 W m−2 per decade) has been observed between 1960 to 1990, whereas, increases of 0.4 K in land temperature during the same period that occurred have resulted in speculations that evaporation and precipitation should also have decreased (Wild et al. 2004). However, precipitation records for the same period over land do not indicate any significant trend (Beck et al. 2005). The changes in precipitation are thought to be related to increased moisture advection from the oceans (Wild et al. 2004), which may well have some contributions from aerosol-radiation-convection coupling that could modify circulation patterns and hence moisture advection in specific regions. Other important aspects of aerosol effects, besides the direct, semi-direct, microphysical and thermodynamical impacts include alteration of surface albedos, especially snow and ice covered surfaces, due to absorbing aerosols. These effects are uncertain (Jacobson, 2004) but may produce as much as 0.3 W m−2 forcing in the Northern hemisphere that could contribute to melting of ice and permafrost and change in the length of the season (e.g. early arrival of Spring) (Hansen and Nazarenko, 2004). Besides the impacts of aerosols on the surface albedos in the polar regions, and the thermodynamical impacts of Arctic haze (composed of water soluble sulfates, nitrates, organic and black carbon (BC)), the dynamical response to Arctic haze (through the radiation-circulation feedbacks that cause changes in pressure patterns) is thought to have the potential to modify the mode and strength of large-scale teleconnection patterns such as the Barrents Sea Oscillation that could affect other climate regimes (mainly Europe) (Rinke et al. 2004). Additionally, via the Asian monsoon, wind patterns over the eastern Mediterranean and lower stratospheric pollution at higher latitudes (Lelieveld et al. 2002) are thought to be linked to the pollutants found in Asia, indicating the distant climate impacts of aerosols.

Mineral Dust

Author : Peter Knippertz
Publisher : Springer
ISBN 13 : 9401789789
Total Pages : 526 pages
Book Rating : 4.4/5 (17 download)

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Book Synopsis Mineral Dust by : Peter Knippertz

Download or read book Mineral Dust written by Peter Knippertz and published by Springer. This book was released on 2014-09-01 with total page 526 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume presents state-of-the-art research about mineral dust, including results from field campaigns, satellite observations, laboratory studies, computer modelling and theoretical studies. Dust research is a new, dynamic and fast-growing area of science and due to its multiple roles in the Earth system, dust has become a fascinating topic for many scientific disciplines. Aspects of dust research covered in this book reach from timescales of minutes (as with dust devils, cloud processes and radiation) to millennia (as with loess formation and oceanic sediments), making dust both a player and recorder of environmental change. The book is structured in four main parts that explore characteristics of dust, the global dust cycle, impacts of dust on the Earth system, and dust as a climate indicator. The chapters in these parts provide a comprehensive, detailed overview of this highly interdisciplinary subject. The contributions presented here cover dust from source to sink and describe all the processes dust particles undergo while travelling through the atmosphere. Chapters explore how dust is lifted and transported, how it affects radiation, clouds, regional circulations, precipitation and chemical processes in the atmosphere and how it deteriorates air quality. The book explores how dust is removed from the atmosphere by gravitational settling, turbulence or precipitation, how iron contained in dust fertilizes terrestrial and marine ecosystems, and about the role that dust plays in human health. We learn how dust is observed, simulated using computer models and forecast. The book also details the role of dust deposits for climate reconstructions. Scientific observations and results are presented, along with numerous illustrations. This work has an interdisciplinary appeal and will engage scholars in geology, geography, chemistry, meteorology and physics, amongst others with an interest in the Earth system and environmental change. body>

Storm and Cloud Dynamics

Author : William R. Cotton
Publisher : Academic Press
ISBN 13 : 0080916651
Total Pages : 826 pages
Book Rating : 4.0/5 (89 download)

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Book Synopsis Storm and Cloud Dynamics by : William R. Cotton

Download or read book Storm and Cloud Dynamics written by William R. Cotton and published by Academic Press. This book was released on 2010-12-21 with total page 826 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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

Mechanisms for the Influence from Ice Nucleus Aerosols on Clouds and Their Indirect Effects: Clous Modelling

Author : Deepak Waman
Publisher :
ISBN 13 : 9789189187252
Total Pages : 0 pages
Book Rating : 4.1/5 (872 download)

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Book Synopsis Mechanisms for the Influence from Ice Nucleus Aerosols on Clouds and Their Indirect Effects: Clous Modelling by : Deepak Waman

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

Toward Assessing the Effects of Aerosols on Deep Convection: a Numerical Study Using the WRF-Chemistry Model

Author : Wendilyn J. Kaufeld
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (774 download)

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Book Synopsis Toward Assessing the Effects of Aerosols on Deep Convection: a Numerical Study Using the WRF-Chemistry Model by : Wendilyn J. Kaufeld

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.

Aerosol Effects on Microphysical Processes and Deep Convective Clouds

Author : Max Heikenfeld
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (12 download)

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Book Synopsis Aerosol Effects on Microphysical Processes and Deep Convective Clouds by : Max Heikenfeld

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 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

The Effects of Aerosol-cloud Interactions on Warm Cloud Properties

Author : Alyson Douglas
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (124 download)

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Book Synopsis The Effects of Aerosol-cloud Interactions on Warm Cloud Properties by : Alyson Douglas

Download or read book The Effects of Aerosol-cloud Interactions on Warm Cloud Properties written by Alyson Douglas and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: When aerosols enter the atmosphere through anthropogenic and natural activities, they interact with clouds in the atmosphere in what is termed aerosol-cloud interactions (ACI). ACI alter the cloud's radiative properties by acting as cloud condensation nuclei within the cloud, thereby reducing the mean drop size and increasing the cloud's albedo and cooling the earth by reflecting incoming shortwave radiation in what is termed the first indirect effect. By reducing the mean drop size throughout the cloud, aerosol also act to delay precipitation formation, leading to larger, longer lived clouds and further cooling the earth in a process known as the second indirect effect. Using four years of satellite observations, the overall impact of aerosols on warm cloud radiative effect is evaluated. Warm clouds are defined as clouds with cloud top temperatures below freezing level. The estimates are constrained within regimes of stability, relative humidity of the free atmosphere, and by the scene liquid water path to control for how meteorology modulates the strength and sign of ACI. The sum of the first and second indirect effect, estimates of how aerosols alter the warm cloud shortwave effect and cloud fraction, are compared to an estimate of the full indirect effect, which includes all changes to the warm cloud shortwave radiative effect. The decomposed, or summative, indirect effect (-0.26 +/- .15 Wm2) is less than the full indirect effect (-0.32 +/- .16 Wm2), though they lie within each other's uncertainty estimates. When the decomposed indirect effect is further constrained by precipitation, the estimate decreases to .21 +/- .15 Wm2. The difference between the full indirect effect forcing and the decomposed forcings may be secondary indirect effects not included in our decomposition. The second indirect effect includes not only the cloud extent broadening, but the cloud depth increasing. This deepening response may increase warming due to a larger longwave cloud radiative effect. The longwave indirect effect susceptibility is decomposed to determine how large it may potentially be and whether it could offset any cooling due to the shortwave indirect effect. We find the longwave indirect effect does have the potential to offset cooling through cloud deepening in regions where the shortwave indirect effect is extremely small, however the magnitude of the longwave component is sensitive to the diurnal cycle. Cloud deepening signals clouds may be invigorated, or experiencing a state where precipitation formation and turbulence increase due to ACI. The effects of aerosol on precipitation formation and vertical motion are investigated using WALRUS, an algorithm of latent heating within the cloud determined using CloudSat radar returns. The LWP is constrained to thicker clouds 150 gm2

Atmospheric Aerosol Properties and Climate Impacts

Author :
Publisher :
ISBN 13 :
Total Pages : 128 pages
Book Rating : 4.:/5 (327 download)

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Download or read book Atmospheric Aerosol Properties and Climate Impacts written by and published by . This book was released on 2009 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Aerosol Effects on Microphysical Properties of Amazonian Clouds

Author : Oliver Lauer
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (137 download)

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Book Synopsis Aerosol Effects on Microphysical Properties of Amazonian Clouds by : Oliver Lauer

Download or read book Aerosol Effects on Microphysical Properties of Amazonian Clouds written by Oliver Lauer and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atmospheric aerosol particles fundamentally affect cloud formation and properties by acting as cloud condensation nuclei (CCN) at cloud base and beyond. The effects of aerosols on clouds in theory and processes on small scale are well understood. For real clouds and for a range of atmospheric pollution states, however, the understand- ing of microphysical processes across the entire cloud structure still bears major open questions. Aircraft studies have accurately measured the aerosol effects on clouds on local scales and for short time periods. Satellite investigations cover large scales for extended periods, but with limited accuracy on microphysical processes at different cloud levels, often covering the cloud tops only. A combination of both,provides a comprehensive picture of aerosol and cloud microphysics on large geographic scales across multiple years, which is crucial to understand the current state and future development of the climate system. In this thesis, in situ aerosol data and high-resolution satellite observations across multiple years were combined for the atmosphere over the remote Amazon rain for- est. Satellite retrieved profiles of the temperature and the effective radius of cloud droplets were used to resolve seasonal changes in fundamental cloud properties. A clear seasonality was found in aerosol and cloud parameters. The fraction of aerosol particles being activated into cloud droplets was high during the pristine wet season, but also during the polluted dry season. It was higher than expected from previous studies. The results show that the cloud formation in the Amazon is both, aerosol- and updraft-sensitive, not just for the low aerosol concentrations in the wet season, but also under the heavy biomass burning smoke influence in the dry season. Our findings shed light on the aerosol-driven changes in fundamental parameters of trop- ical convective clouds and suggest that the buffering effect of updraft-limited droplet activation at high aerosol concentrations is smaller than expected. The effects of aerosol particles on cloud properties are not limited to cloud base, but cover the entire vertical cloud structure. Seasonal patterns in the vertical cloud structure were investigated by resolving the distinct microphysical zones of conden- sational droplet growth, collision and coalescence, secondary droplet activation, the mixed phase of water and ice particles as well as the ice phase. The vertical profiles of the effective radius of cloud particles as a function of temperature differ strongly between the low aerosol conditions during the wet season and the biomass burning smoke dominated dry season. The vertical depth of the cloud microphysical zones is strongly seasonal as well. The seasonality is most pronounced for the condensational growth zone, which is much deeper in the dry season. In contrast, the secondary activation zone plays a more significant role in the wet season. These findings under- line that the widely variable aerosol population in the Amazon has profound effects on microphysical processes across the entire vertical profile of convective clouds.

Aerosols and Climate

Author : Ken S. Carslaw
Publisher : Elsevier
ISBN 13 : 0128231726
Total Pages : 856 pages
Book Rating : 4.1/5 (282 download)

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Book Synopsis Aerosols and Climate by : Ken S. Carslaw

Download or read book Aerosols and Climate written by Ken S. Carslaw and published by Elsevier. This book was released on 2022-08-19 with total page 856 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ever-diversifying field of aerosol effects on climate is comprehensively presented here, describing the strong connection between fundamental research and model applications in a way that will allow both experienced researchers and those new to the field to gain an understanding of a wide range of topics. The material is consistently presented at three levels for each topic: (i) an accessible "quick read" of the essentials, (ii) a more detailed description, and (iii) a section dedicated to how the processes are handled in models. The modelling section in each chapter summarizes the current level of knowledge and what the gaps in this understanding mean for the effects of aerosols on climate, enabling readers to quickly understand how new research fits into established knowledge. Definitions, case studies, reference data, and examples are included throughout. Aerosols and Climate is a vital resource for graduate students, postdoctoral researchers, senior researchers, and lecturers in departments of atmospheric science, meteorology, engineering, and environment. It will also be of interest to those working in operational centers and policy-facing organizations, providing strong reference material on the current state of knowledge. Includes a section in each chapter that focuses on the treatment of relevant aerosol processes in climate models Provides clear exposition of the challenges in understanding and reducing persistent gaps in knowledge and uncertainties in the field of aerosol-climate interaction, going beyond the fundamentals and existing knowledge Authored by experts in modeling and aerosol processes, analysis or observations to ensure accessibility and balance

Mechanisms for the Influence from Ice Nucleus Aerosols on Clouds and Their Indirect Effects: Cloud Modelling

Author : Deepak Waman
Publisher :
ISBN 13 : 9789189187269
Total Pages : 0 pages
Book Rating : 4.1/5 (872 download)

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Book Synopsis Mechanisms for the Influence from Ice Nucleus Aerosols on Clouds and Their Indirect Effects: Cloud Modelling by : Deepak Waman

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

Investigation of the Aerosol-cloud Interaction Using the WRF Framework

Author : Guohui Li
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (689 download)

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Book Synopsis Investigation of the Aerosol-cloud Interaction Using the WRF Framework by : Guohui Li

Download or read book Investigation of the Aerosol-cloud Interaction Using the WRF Framework written by Guohui Li and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation, a two-moment bulk microphysical scheme with aerosol effects is developed and implemented into the Weather Research and Forecasting (WRF) model to investigate the aerosol-cloud interaction. Sensitivities of cloud properties to the representation of aerosol size distributions are first evaluated using a simple box model and a cloud resolving model with a detailed spectral-bin microphysics, indicating that the three-moment method generally exhibits better performance in modeling cloud properties than the two-moment method against the sectional approach. A convective cloud event occurring on August 24, 2000 in Houston, Texas is investigated using the WRF model, and the simulation results are qualitatively in agreement with the measurements. Simulations with various aerosol profiles demonstrate that the response of precipitation to the increase of aerosol concentrations is non-monotonic. The maximal cloud cover, core updraft, and maximal vertical velocity exhibit similar responses as precipitation. The WRF model with the two-moment microphysical scheme successfully simulates the development of a squall line that occurred in the south plains of the U.S. Model experiments varying aerosol concentrations from the clean background case to the polluted continental case show that the aerosol concentrations insignificantly influence the rainfall pattern/distribution, but can remarkably alter the precipitation intensity. The WRF experiment with polluted aerosols predicts 12.8% more precipitation than that with clean aerosols, as well as more intensive rainfall locally. Using the monthly mean cloudiness from the International Satellite Cloud Climatology Project (ISCCP), a trend of increasing deep convective clouds over the north Pacific in winter from 1984 to 2005 is detected. Additionally, through analyzing the results from the Global Precipitation Climatology Project (GPCP) version 2, we also show a trend of increasing wintertime precipitation over the north Pacific from 1984 to 2005. Simulations with the WRF model reveal that the increased deep convective clouds and precipitation are reproduced when accounting for the aerosol effect from the increasing Asian pollution outflow.