Download or read book Investigating Aerosol cloud Interactions written by Benjamin Stephen Grandey and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Microphysical and dynamical interactions between aerosols and clouds are associated with some of the largest uncertainties in projections of future climate. Many possible aerosol effects on clouds have been suggested, but large uncertainties remain. In order to improve model projections of fu- ture climate, it is essential that we improve our quantitative understanding of anthropogenic aerosol effects. Several studies investigating interactions between satellite-observed aerosol and cloud prop- erties have been published in recent years. However, the observed relationships are not necessarily due to aerosol effects on clouds. They may be due to cloud and precipitation effects on aerosol, me- teorological covariation, observational data errors or methodological errors. An analysis of method- ological errors arising through climatological spatial gradients is performed. For region sizes larger than 40 x 40, commonly used in the literature, spurious spatial variations in retrieved cloud and aerosol properties are found to introduce widespread significant errors to calculations of aerosol- cloud relationships. Small scale analysis prior to error-weighted aggregation to larger region sizes is recommended. Appropriate ways of quantifying relationships between aerosol optical depth (T) and cloud properties are considered, and results are presented for three satellite datasets. There is much disagreement in observed relationships between T and liquid cloud droplet number concentration and between T and liquid cloud droplet effective radius, particularly over land. However, all three satellite datasets are in agreement about strong positive relationships between T and cloud top height and between T and cloud fraction (fc). Using reanalysis T data, which are less affected by retrieval artifacts, it is suggested that a large part of the observed Ie-r signal may fc-T be due to cloud contamination of T. General circulation model simulations further demonstrate that positive fc-T relationships may primarily arise due to covariation with relative humidity, and that negative fc-T relationships may arise due to scavenging of aerosol by precipitation. A new method of investigating the contribu- tion of meteorological covariation to the observed relationships is introduced. Extratropical cyclone storm-centric composites of retrieved aerosol and cloud properties are investigated. A storm-centric description of the synoptics is found to be capable of explaining spurious fc-T relationships, although the spurious relationships explained are considerably smaller than observed relationships.
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.
Download or read book Investigation and Parameterization of Aerosol cloud Interactions Using Cloud Parcel Model and Observations written by Jingyi Chen and published by . This book was released on 2018 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
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.
Download or read book Nucleation and Atmospheric Aerosols written by Colin D. O'Dowd and published by Springer Science & Business Media. This book was released on 2007-10 with total page 1275 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atmospheric particles are ubiquitous in the atmosphere: they form the seeds for cloud droplets and they form haze layers, blocking out incoming radiation and contributing to a partial cooling of our climate. They also contribute to poor air quality and health impacts. A large fraction of aerosols are formed from nucleation processes – that is a phase transition from vapour to liquid or solid particles. Examples are the formation of stable clusters about 1 nm in size from molecular collisions and these in turn can grow into larger (100 nm or more) haze particles via condensation to the formation of ice crystals in mixed phase or cold clouds. This book brings together the leading experts from the nucleation and atmospheric aerosols research communities to present the current state-of-the-art knowledge in these related fields. Topics covered are: Nucleation Experiment & Theory, Binary, Homogeneous and Heterogeneous Nucleation, Ion & Cluster Properties During Nucleation, Aerosol Characterisation & Properties, Aerosol Formation, Dynamics and Growth, Marine Aerosol Production, Aerosol-Cloud Interactions, Chemical Composition & Cloud Drop Activation, Remote Sensing of aerosol & clouds and Air Quality-Climate Interactions
Download or read book Investigating the Interactions of Pure and Multicomponent Organic Aerosols with Water written by Mark W. Zimmerman and published by . This book was released on 2007 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atmospheric aerosols have a significant impact on global climate, both directly by absorbing or reflecting solar radiation and indirectly by forming clouds. Particles can act as cloud condensation nuclei (CCN) by taking on water and growing in size until they reach their activation diameter. Investigates the reasons for conflicting experimental activation data in pure organic aerosols and to gain further understanding of organic aerosol interactions with water. Another goal was to measure the activation of multicomponent organic aerosols to determine CCN activity.
Download or read book Investigations of Cloud Altering Effects of Atmospheric Aerosols Using a New Mixed Eulerian Lagrangian Aerosol Model written by Henry Donnan Steele and published by . This book was released on 2004 with total page 315 pages. Available in PDF, EPUB and Kindle. Book excerpt: Industry, urban development, and other anthropogenic influences have substantially altered the composition and size-distribution of atmospheric aerosol particles over the last century. This, in turn, has altered cloud albedo, lifetime, and patterns which together are thought to exert a negative radiative forcing on the climate; these are the indirect effects of atmospheric aerosols. The specifics of the process by which aerosol particles seed cloud particles are complex and highly uncertain. The goal of this thesis is to refine understanding of the role of various aerosol types in determining cloud properties. We approach this goal by constructing a new highly detailed aerosol-cloud process model that is designed to simulate condensation upon complex aerosol populations. We use this model to investigate the microphysics of aerosol-cloud interactions, specifically considering the role of cloud dynamics and of the ubiquitous mixed soot / sulfate aerosols. We describe the Mixed Eulerian-Lagrangian Aerosol Model (MELAM). This new computer model of aerosol microphysics is specifically tailored to simulate condensation and activation as accurately as possible. It specifically calculates aerosol thermodynamics, condensation, coagulation, gas and aqueous phase chemistry, and dissolution. The model is able to consider inorganic aerosols and aerosols with both inorganics and insoluble cores; the specific chemical system to be considered is specified by the user in text input files. Aerosol particles may be represented using "sectional distributions" or using a "representative sample" distribution which tracks individual particles. We also develop a constant updraft speed, adiabatic parcel model and a variable updraft speed, episodically entraining parcel model to provide boundary conditions to MELAM and allow simulations of aerosol activation in cloud updrafts. Using MELAM and the parcel models, we demonstrate that aerosol activation depends on the composition and size distribution of the sub-cloud aerosol population, on the updraft speed through a parcel's lifting condensation level, on the vertical profile of the updraft speed, and on entrainment. We use a convective parameterization that was developed for use in global or regional models to drive the episodically entraining, variable updraft speed parcel model. Ultimately, reducing the uncertainty of the global impact of the indirect effects of aerosols will depend on successfully linking cloud parameterizations to models of aerosol activation; our work represents a step in that direction. We also consider the activation of mixed soot / sulfate particles in cloud updrafts. We constrain for the first time a model of condensation onto these mixed particles that incorporates the contact angle of the soot / solution interface and the size of the soot core. We find that as soot ages and its contact angle with water decreases, mixed soot / sulfate aerosols activate more readily than the equivalent sulfate aerosols that do not have soot inclusions. We use data from the Aerosol Characterization Experiments (ACE) 1 and 2, and from the Indian Ocean Experiment (INDOEX) to define representative aerosol distributions for clean, polluted, and very polluted marine environments. Using these distributions, we argue that the trace levels of soot observed in clean marine environments do not substantially impact aerosol activation, while the presence of soot significantly increases the number of aerosol that activate in polluted areas.
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
Download or read book Impacts of Aerosol cloud Interactions on Past and Future Changes in Tropospheric Composition written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of effective emissions control policies that are beneficial to both climate and air quality requires a detailed understanding of all the feedbacks in the atmospheric composition and climate system. We perform sensitivity studies with a global atmospheric composition-climate model to assess the impact of aerosols on tropospheric chemistry through their modification on clouds, aerosol-cloud interactions (ACI). The model includes coupling between both tropospheric gas-phase and aerosol chemistry and aerosols and liquid-phase clouds. We investigate past impacts from preindustrial (PI) to present day (PD) and future impacts from PD to 2050 (for the moderate IPCC A1B scenario) that embrace a wide spectrum of precursor emission changes and consequential ACI. The aerosol indirect effect (AIE) is estimated to be -2.0 Wm−2 for PD-PI and -0.6 Wm−2 for 2050-PD, at the high end of current estimates. Inclusion of ACI substantially impacts changes in global mean methane lifetime across both time periods, enhancing the past and future increases by 10% and 30%, respectively. In regions where pollution emissions increase, inclusion of ACI leads to 20% enhancements in in-cloud sulfate production and (almost equal to)10% enhancements in sulfate wet deposition that is displaced away from the immediate source regions. The enhanced in-cloud sulfate formation leads to larger increases in surface sulfate across polluted regions ((almost equal to)10-30%). Nitric acid wet deposition is dampened by 15-20% across the industrialized regions due to ACI allowing additional re-release of reactive nitrogen that contributes to 1-2 ppbv increases in surface ozone in outflow regions. Our model findings indicate that ACI must be considered in studies of methane trends and projections of future changes to particulate matter air quality.
Download or read book Aerosol cloud precipitation Interaction in Ultraclean Layers and Optically Thin Veil Cloud System in the Stratocumulus to Cumulus Transition written by Kuan-Ting O and published by . This book was released on 2019 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent observational studies have shown that ultraclean layers (UCLs) and optically thin veil clouds associated with precipitating deep cumulus are common features of the marine boundary layer in the stratocumulus to cumulus transition. The very low number concentration of cloud droplet and cloud condensation nuclei in UCLs, strong precipitation in the associated cumulus, together with the low optical thickness of optically thin veil clouds, make such a system particularly appealing for the study of aerosol-cloud-precipitation interactions. More importantly, low cloud radiative properties biases (i.e., too few, too bright low cloud bias) in the current generation of global climate models (GCMs) seems strongly associated with the uncertainty in representing optically thin veil clouds, and these clouds may serve as an important constraint on the too few, too bright problem. However, systematic investigation of (1) global contribution and seasonal variability of optically thin veil clouds and (2) aerosol-cloud-precipitation interactions in UCLs and optically thin veil clouds is still lacking. We aim to investigate these problems with aircraft remote sensing, satellite measurements and a cloud resolving model. The dissertation is organized into the following three sections: • Using high resolution aircraft remote sensing measurement to characterize optically thin veil clouds in the stratocumulus to cumulus transition (SCT): Aircraft remote sensing measurements (i.e., lidar and radar) taken abroad NSF/NCAR GV-HIAPER research flights flown during the Cloud System Evolution in the Trades field campaign (CSET) sampled marine air masses between Sacramento, California (38.68N, 121.58W), and Kona (19.68N, 156.08W) are used in our study. Optically thin veil clouds, defined as the subset of low clouds with cloud bases > 1 km that do not fully attenuate high-spectral-resolution lidar signal (HSRL) (i.e., indicating optical depths 3), comprise considerable cover of low clouds (~ 40 %) over the SCT. It is found that optically thin veil clouds are also geometrically thin with cloud thickness ~ 200 m, and commonly reside in the upper boundary layer with average cloud base 1.5 km. • Investigating deeper, precipitating PBLs associated with optically thin veil clouds in the Sc-Cu Transition using spaceborne satellite measurements: Variability and vertical structure of optically thin veil clouds over SCT regions around the globe are investigated using both passive and active satellite observations. These observations reveal pronounced relationships between optically thin veil clouds, strong precipitation, deep planetary boundary layer (PBL) height and low cloud droplet number concentration (CDNC). The results are in agreement with the hypothesis that the low optical thickness of veil clouds over the SCT is contingent on the low CDNC caused by strong precipitation scavenging occurring in active cumuli, a process whose efficiency is strongly dependent on maximum condensate amount in updrafts and thus is highly constrained by PBL height. • Exploring aerosol-cloud-precipitation processes in UCLs and optically thin veil clouds system using a cloud resolving model: Characteristics of UCLs and optically thin veil clouds are investigated in the cloud resolving model (CRM). The domain mean cloud and aerosol properties in UCLs and optically thin veil clouds from CRM simulations agree with recent observational studies in general. The simulation results show that the detrainment from active precipitating cumulus produces the stratiform veil clouds, which are strongly depleted in particle concentration due to very efficient coalescence-scavenging process in ascending parcels passing through cumulus towers. The simulation shows a median CDNC in thin veil clouds of 5.8 cm−3, implying that majority of thin veil clouds are UCLs as well and confirming the strong connection between veil clouds and UCLs. In addition, there is a strong correlation between surface precipitation and the fraction of low clouds that are UCLs, and such correlation implies the importance of precipitation scavenging for the formation of UCLs. A cloud resolving model coupled with a prognostic aerosol scheme is used in our study, enabling characterization of the spatiotemporal variability of aerosol in the boundary layer. The results show that depletion of aerosol concentration starts first in the upper boundary layer that is associated with in-cloud coalescence scavenging process. The evaporation of veil clouds leaves very low CCN number concentration (Na
Download or read book A Plan for a Research Program on Aerosol Radiative Forcing and Climate Change written by Panel on Aerosol Radiative Forcing and Climate Change and published by National Academies Press. This book was released on 1996-05-01 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book recommends the initiation of an "integrated" research program to study the role of aerosols in the predicted global climate change. Current understanding suggest that, even now, aerosols, primarily from anthropogenic sources, may be reducing the rate of warming caused by greenhouse gas emissions. In addition to specific research recommendations, this book forcefully argues for two kinds of research program integration: integration of the individual laboratory, field, and theoretical research activities and an integrated management structure that involves all of the concerned federal agencies.
Download or read book BAECC Biogenic Aerosols Effects on Clouds and Climate written by and published by . This book was released on 2015 with total page 53 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Biogenic Aerosols - Effects on Clouds and Climate (BAECC)", featured the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) Program's 2nd Mobile Facility (AMF2) in Hyytiälä, Finland. It operated for an 8-month intensive measurement campaign from February to September 2014. The main research goal was to understand the role of biogenic aerosols in cloud formation. One of the reasons to perform BAECC study in Hyytiälä was the fact that it hosts SMEAR-II (Station for Measuring Forest Ecosystem-Atmosphere Relations), which is one of the world's most comprehensive surface in-situ observation sites in a boreal forest environment. The station has been measuring atmospheric aerosols, biogenic emissions and an extensive suite of parameters relevant to atmosphere-biosphere interactions continuously since 1996. The BAECC enables combining vertical profiles from AMF2 with surface-based in-situ SMEAR-II observations and allows the processes at the surface to be directly related to processes occurring throughout the entire tropospheric column. With the inclusion of extensive surface precipitation measurements, and intensive observation periods involving aircraft flights and novel radiosonde launches, the complementary observations of AMF2 and SMEAR-II provide a unique opportunity for investigating aerosol-cloud interactions, and cloud-to-precipitation processes. The BAECC dataset will initiate new opportunities for evaluating and improving models of aerosol sources and transport, cloud microphysical processes, and boundary-layer structures.
Download or read book Thermodynamics Kinetics and Microphysics of Clouds written by Vitaly I. Khvorostyanov and published by Cambridge University Press. This book was released on 2014-08-25 with total page 801 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book advances understanding of cloud microphysics and provides a unified theoretical foundation for modeling cloud processes, for researchers and advanced students.
Download or read book Investigation of the Impact of Aerosols on Clouds During May 2003 Intensive Operational Period at the Southern Great Plains written by and published by . This book was released on 2005 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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
Download or read book Climate Intervention written by National Research Council and published by National Academies Press. This book was released on 2015-06-23 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt: The growing problem of changing environmental conditions caused by climate destabilization is well recognized as one of the defining issues of our time. The root problem is greenhouse gas emissions, and the fundamental solution is curbing those emissions. Climate geoengineering has often been considered to be a "last-ditch" response to climate change, to be used only if climate change damage should produce extreme hardship. Although the likelihood of eventually needing to resort to these efforts grows with every year of inaction on emissions control, there is a lack of information on these ways of potentially intervening in the climate system. As one of a two-book report, this volume of Climate Intervention discusses albedo modification - changing the fraction of incoming solar radiation that reaches the surface. This approach would deliberately modify the energy budget of Earth to produce a cooling designed to compensate for some of the effects of warming associated with greenhouse gas increases. The prospect of large-scale albedo modification raises political and governance issues at national and global levels, as well as ethical concerns. Climate Intervention: Reflecting Sunlight to Cool Earth discusses some of the social, political, and legal issues surrounding these proposed techniques. It is far easier to modify Earth's albedo than to determine whether it should be done or what the consequences might be of such an action. One serious concern is that such an action could be unilaterally undertaken by a small nation or smaller entity for its own benefit without international sanction and regardless of international consequences. Transparency in discussing this subject is critical. In the spirit of that transparency, Climate Intervention: Reflecting Sunlight to Cool Earth was based on peer-reviewed literature and the judgments of the authoring committee; no new research was done as part of this study and all data and information used are from entirely open sources. By helping to bring light to this topic area, this book will help leaders to be far more knowledgeable about the consequences of albedo modification approaches before they face a decision whether or not to use them.
