Aerosol Indirect Effects on Clouds and Global Climate PDF Download
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Author: Yang Chen
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 472
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Book Description
Author: Yang Chen
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 472
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Book Description
Author: Daniel Alexander Rothenberg
Publisher:
ISBN:
Category :
Languages : en
Pages : 189
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Book Description
The influence of anthropogenic aerosol emissions on the optical properties of clouds and the radiative forcing arising from these interactions, known as the aerosol indirect effect on climate, constitutes a fundamental uncertainty in our understanding of 2 0 th century climate change. In this dissertation, we investigate the role of a keystone physical process, droplet activation, in contributing to this uncertainty. The first half of the ensuing work focuses on the parameterization of this process in global model, assessing both existing schemes and developing a novel one. The second half then quantifies the influence of activation by using a suite of aerosol-climate models which include a complete description of the physics which give rise to the indirect effect. Parameterizations of droplet activation perform well for idealized single-mode aerosol populations, but show systematic biases in high-pollution, weak-updraft regimes. These are exacerbated when the aerosol in question is a complex mixture. We show that estimates of droplet nucleation are highly sensitive to changes in the accumulation mode size and number concentration; this mode is itself sensitive to anthropogenic aerosol emissions, which potentially further biases modeled cloud droplet number. Using a model emulation technique, we develop a framework for building efficient metamodels of activation, which greatly reduce the mean error in droplet number predicted across regimes. The biases in these parameterizations raise questions the influence of activation on the indirect effect. Using different schemes, we calculate a spread of 1 W m- 2 in the indirect effect, which we show is equal to the spread computed from an independent suite of global models with different aerosol and physics modules. The estimated indirect effect scales more strongly with the baseline cloud droplet number concentration simulated by each model than by its change from pre-industrial to present day, indicating a strong saturation effect. While present-day estimates of aerosol-cloud interactions derived from satellite-based instruments are inadequate at constraining the pre-industrial cloud droplet burden, we show that process-based measurements could overcome this problem.
Author: Colin O'Dowd
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Constantin Andronache
Publisher: Elsevier
ISBN: 012810550X
Category : Science
Languages : en
Pages : 302
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Book Description
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: National Research Council
Publisher: National Academies Press
ISBN: 0309133505
Category : Science
Languages : en
Pages : 222
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Book Description
Changes in climate are driven by natural and human-induced perturbations of the Earth's energy balance. These climate drivers or "forcings" include variations in greenhouse gases, aerosols, land use, and the amount of energy Earth receives from the Sun. Although climate throughout Earth's history has varied from "snowball" conditions with global ice cover to "hothouse" conditions when glaciers all but disappeared, the climate over the past 10,000 years has been remarkably stable and favorable to human civilization. Increasing evidence points to a large human impact on global climate over the past century. The report reviews current knowledge of climate forcings and recommends critical research needed to improve understanding. Whereas emphasis to date has been on how these climate forcings affect global mean temperature, the report finds that regional variation and climate impacts other than temperature deserve increased attention.
Author: Kyle Tietze
Publisher:
ISBN:
Category : Air
Languages : en
Pages : 72
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Author: Yunha Lee
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: Abhilash S. Panicker
Publisher: LAP Lambert Academic Publishing
ISBN: 9783838396903
Category :
Languages : en
Pages : 128
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Book Description
Aerosols, which are tiny particles suspended in the atmosphere, influences the climate directly and indirectly through radiative forcing. Aerosols reduce the ground-reaching solar radiation directly by scattering and absorption processes, known as direct radiative forcing. They influence the climate indirectly by modifying the cloud microphysics, known as aerosol indirect radiative forcing. It is found that the aerosol direct and indirect raditive effects can perturb the earth s radiation budget and tropospheric temperature profile, which can make changes even in precipitation patterns. Aerosol direct and indirect radiative forcing estimates have been revealed as one of the major uncertainties in global climate modeling. Uncertainty in determining aerosol radiative forcing is found to be larger than that of greenhouse gases. Hence it is necessary to estimate the aerosol direct and indirect forcing in climate change perspective. In this scenario, this book is intended to quantitatively estimate aerosol direct and indirect effects using ground and satellite remote sensing data sets.
Author: Huilin Huang
Publisher:
ISBN:
Category :
Languages : en
Pages : 61
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Book Description
Aerosols come from both natural and anthropogenic sources and contribute large uncertainties to estimates of the Earth's changing energy budget. It is thus of great importance to understand the mechanism through which aerosols play a role on global climate. In this thesis, we investigate the direct and indirect effect of aerosols on global and regional climate variability (e.g. West Africa, South Asia and East Asia) using an atmospheric general circulation model, GFS (Global Forecast System) coupled with SSiB2 (the second version of Si mplified Simple Biosphere Model). The three-dimensional aerosol data from the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model has been adopted in this study. We first analyze the direct effect of aerosols, especially absorption aerosols, on global and regional energy budget, precipitation, and surface temperature and the mechanism involved. For instance, we find the dust aerosol in North Africa produces a heating in the atmosphere, which generates a cyclonic circulation in middle layer over Sahel region, which further brings about upward motion in the lower level and results in precipitation increase by 0.96 mm/day in June-July-August. We also examine the impact of aerosols on ice clouds effective radius by applying an advanced ice cloud parameterization in the GCM. We find that increased aerosol loading reduces ice crystal size due to aerosol first indirect effect, with the maxima occurs in South Asia and North Indian Ocean. Ice clouds with smaller crystal sizes can absorb both shortwave and longwave radiation, thus resulting in less downward solar flux and less outgoing longwave on top of atmosphere (TOA). Global mean net radiation change on TOA is about 0.5W/m2 and its sign is largely dependent on the relative magnitude of shortwave and longwave change and precipitation changes primarily respond to cooling/warming of the atmosphere. Lastly, we use sulfate data in both pre-industrial and present-day case to test the impact of aerosols on liquid cloud effective radius. We find aerosols can act as cloud condensation nuclei, and hence change the shortwave optical properties of liquid clouds. Radiative cooling occurs globally because smaller droplets size leads to increased cloud albedo. The mean value is about 2.5W/m2. Moreover, most radiative cooling occurs in North Hemisphere, where anthropogenic sulfate aerosols locate, such as East Asia and North America. We also compare the radiative forcing of aerosol direct and indirect effect on both ice clouds and liquid clouds on global as well as the three monsoon regions. All aerosol effects result in radiative cooling on global scale. However, surface net radiation changes are different in West Africa, East and South Asia, which relates to local atmospheric conditions such as cloud cover and convection. Aerosol direct effect and aerosol indirect effect for liquid clouds have comparable impact on surface net radiation change (more than -3 W/m2), while aerosol indirect effects for ice cloud are smaller (~1 W/m2) because of the negative feedback from cloud cover. Decreased land surface temperature can be found over North Hemisphere continent in all three effects, especially over higher latitude, with varied magnitude. The precipitation changes are less predictable. Aerosol indirect effects on averaged global precipitations are close to zero because the precipitation changes are different or even opposite in different regions. The effect of aerosol on precipitations can be influenced by convection strength, topography, and even the relative location of aerosols and monsoon system.
Author: Panel on Aerosol Radiative Forcing and Climate Change
Publisher: National Academies Press
ISBN: 0309588871
Category : Science
Languages : en
Pages : 180
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Book Description
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.
