Aerosol-Cloud-Precipitation Interactions in Moist Orographic Flows

Aerosol-Cloud-Precipitation Interactions in Moist Orographic Flows
Author: Andreas Mühlbauer
Publisher: Sudwestdeutscher Verlag Fur Hochschulschriften AG
Total Pages: 0
Release: 2009
Genre: Aerosols
ISBN: 9783838106809

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Aerosols are ubiquitous in the Earth's atmosphere and influence the climate system through their interactions with clouds and radiation. With their ability to serve as cloud condensation nuclei and ice nuclei aerosols influence microphysical processes in clouds thereby potentially affecting precipitation. In this book the possible effects of aerosols on orographic precipitation are investigated with a numerical model.

Modeling Aerosol-Cloud-Precipitation Interactions in Mountainous Regions

Modeling Aerosol-Cloud-Precipitation Interactions in Mountainous Regions
Author: Ana Barros
Publisher:
Total Pages: 0
Release: 2018
Genre: Electronic books
ISBN:

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In mountainous regions, the nonlinear thermodynamics of orographic land-atmosphere interactions (LATMI) in organizing and maintaining moisture convergence patterns on the one hand, and aerosol-cloud-precipitation interactions (ACPI) in modulating the vertical structure of precipitation and space-time variability of surface precipitation on the other, are difficult to separate unambiguously because the physiochemical characteristics of aerosols themselves exhibit large sub-regional scale variability. In this chapter, ACPI in the Central Himalayas are examined in detail using aerosol observations during JAMEX09 (Joint Aerosol Monsoon Campaign 2009) to specify CCN activation properties for simulations of a premonsoon convective storm using the Weather Research and Forecasting (WRF) version 3.8.1. The focus is on contrasting AIE during episodes of remote pollution run-up from the Indo-Gangetic Plains and when only local aerosols are present in Central Nepal. This study suggests strong coupling between the vertical structure of convection in complex terrain that governs the time-scales and spatial organization of cloud development, CCN activation rates, and cold microphysics (e.g. graupel production is favored by slower activation spectra) that result in large shifts in the spatial distribution of precipitation, precipitation intensity and storm arrival time.

Aerosol-Cloud-Precipitation Interactions in the Trade Wind Boundary Layer

Aerosol-Cloud-Precipitation Interactions in the Trade Wind Boundary Layer
Author: Eunsil Jung
Publisher:
Total Pages:
Release: 2012
Genre:
ISBN:

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This dissertation includes an overview of aerosol, cloud, and precipitation properties associated with shallow marine cumulus clouds observed during the Barbados Aerosol Cloud Experiment (BACEX, March-April 2010) and a discussion of their interactions. The principal observing platform for the experiment was the Cooperative Institute for Remotely Piloted Aircraft Studies (CIRPAS) Twin Otter (TO) research aircraft that was equipped with aerosol, cloud, and precipitation probes, standard meteorological instruments, and a up-looking cloud radar. The temporal variations and vertical distributions of aerosols observed on the 15 flights show a wide range of aerosol conditions that include the most intense African dust event observed at the Barbados surface site during all of 2010. An average CCN varied from 50 cm-3 to 800 cm-3 at super-saturation of 0.6 %, for example. The 10-day backward trajectories show that three distinctive air masses (originality of air mass as well as the vertical structure) dominate over the Eastern Caribbean (e.g., typical maritime air mass, Saharan Air Layer (SAL), Middle latitude dry air) with characteristic aerosol vertical structures. Many clouds in various phases of growth during BACEX are sampled. The maximum cloud depth observed is about less than 3 km and in most of the clouds is less than 1 km. Two types of precipitation features were observed for the shallow marine cumulus clouds with different impacts on boundary layer. In one, precipitation shafts are observed to emanate from the cloud base with evaporation in the sub-cloud layer (stabilize the sub-cloud layer). In the other, precipitation shafts emanate mainly near the cloud top on the downshear side of the cloud and evaporate in the cloud layer, leading to destabilizing the cloud layer and providing moisture to the layer. Only 42-44 % of clouds sampled were purely non-precipitating throughout the clouds; the remainder of the clouds showed precipitation somewhere in the cloud, predominantly closer to the cloud top. The relationship between aerosol (Na), cloud droplets (Nd), and precipitation rates (R) is addressed to explore aerosol-cloud-precipitation interactions. A robust increase in Nd with increase in aerosol concentrations is documented. Further, a strong linear relation between sub-cloud CCN and cloud-base Nd is observed in updrafts. The sensitivity of Nd to changes in vertical velocity perturbations w ́ (i.e., dlnNd /dlnw ́), is greater in the regimes of high aerosol concentrations, suggesting a slight increase in updrafts (or w ́) in polluted conditions can lead to greater increases in Nd. Suppression of precipitation with aerosol is a common feature during BACEX. To quantify this decrease of precipitation toward higher aerosol concentration, the sensitivity of precipitation to changes in aerosol (i.e., precipitation susceptibility S0 ) is examined. S0 exhibits three regimes and peaks at intermediate range of cloud thickness. Further, the removal of Nd , due to the rain (wet scavenging), makes susceptibility stronger overall. In addition to the aerosol feeding clouds from the sub-cloud layer, small cumuli can alter the aerosol properties of their immediate environment through cloud and precipitation processes. In the warm cumuli studied, the depletion of aerosols near cloud field (so-called cloud halos/shell regimes) are notable, and the reduction of aerosols is more significant in precipitating clouds compared with non-and/or light-precipitating clouds. The modification of boundary layer aerosol by cloud processes is also explored. The comparisons of the thermodynamic structures observed over Africa with those at Barbados indicate that layers below the SAL are moistened by surface fluxes and convective processes as the air masses are advected across the Atlantic over 7-10 days.

Aerosol-Cloud Interactions from Urban, Regional, to Global Scales

Aerosol-Cloud Interactions from Urban, Regional, to Global Scales
Author: Yuan Wang
Publisher: Springer
Total Pages: 100
Release: 2015-05-05
Genre: Science
ISBN: 3662471752

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The studies in this dissertation aim at advancing our scientific understandings about physical processes involved in the aerosol-cloud-precipitation interaction and quantitatively assessing the impacts of aerosols on the cloud systems with diverse scales over the globe on the basis of the observational data analysis and various modeling studies. 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.

Aerosol-Cloud-Climate Interactions

Aerosol-Cloud-Climate Interactions
Author: Peter V. Hobbs
Publisher: Academic Press
Total Pages: 259
Release: 1993-07-22
Genre: Science
ISBN: 0080959962

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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.

Opportunities to Improve Representation of Clouds and Aerosols in Climate Models with Classified Observing Systems

Opportunities to Improve Representation of Clouds and Aerosols in Climate Models with Classified Observing Systems
Author: National Academies of Sciences, Engineering, and Medicine
Publisher: National Academies Press
Total Pages: 53
Release: 2016-08-31
Genre: Science
ISBN: 0309443458

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One of the most significant and uncertain aspects of climate change projections is the impact of aerosols on the climate system. Aerosols influence the climate indirectly by interacting with nearby clouds leading to small changes in cloud cover, thickness, and altitude, which significantly affect Earth's radiative balance. Advancements have been made in recent years on understanding the complex processes and atmospheric interactions involved when aerosols interact with surrounding clouds, but further progress has been hindered by limited observations. The National Academies of Sciences, Engineering, and Medicine organized a workshop to discuss the usefulness of the classified observing systems in advancing understanding of cloud and aerosol interactions. Because these systems were not developed with weather and climate modeling as a primary mission objective, many participants said it is necessary for scientists to find creative ways to utilize the data. The data from these systems have the potential to be useful in advancing understanding of cloud and aerosol interactions. This publication summarizes the presentations and discussions from the workshop.

Aerosol Pollution Impact on Precipitation

Aerosol Pollution Impact on Precipitation
Author: Zev Levin
Publisher: Springer Science & Business Media
Total Pages: 399
Release: 2008-09-30
Genre: Science
ISBN: 1402086903

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Life on Earth is critically dependent upon the continuous cycling of water between oceans, continents and the atmosphere. Precipitation (including rain, snow, and hail) is the primary mechanism for transporting water from the atmosphere back to the Earth’s surface. It is also the key physical process that links aspects of climate, weather, and the global hydrological cycle. Changes in precipitation regimes and the frequency of extreme weather events, such as floods, droughts, severe ice/snow storms, monsoon fluctuations and hurricanes are of great potential importance to life on the planet. One of the factors that could contribute to precipitation modification is aerosol pollution from various sources such as urban air pollution and biomass burning. Natural and anthropogenic changes in atmospheric aerosols might have important implications for precipitation by influencing the hydrological cycle, which in turn could feed back to climate changes. From an Earth Science perspective, a key question is how changes expected in climate will translate into changes in the hydrological cycle, and what trends may be expected in the future. We require a much better understanding and hence predictive capability of the moisture and energy storages and exchanges among the Earth’s atmosphere, oceans, continents and biological systems. This book is a review of our knowledge of the relationship between aerosols and precipitation reaching the Earth's surface and it includes a list of recommendations that could help to advance our knowledge in this area.