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Sensitivity of Boreal-summer Circulation and Precipitation to Atmospheric Aerosols in Selected Regions – Part 1: Africa and India : Volume 27, Issue 10 (23/10/2009)

By Sud, Y. C.

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Book Id: WPLBN0003980831
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File Size: Pages 19
Reproduction Date: 2015

Title: Sensitivity of Boreal-summer Circulation and Precipitation to Atmospheric Aerosols in Selected Regions – Part 1: Africa and India : Volume 27, Issue 10 (23/10/2009)  
Author: Sud, Y. C.
Volume: Vol. 27, Issue 10
Language: English
Subject: Science, Annales, Geophysicae
Collections: Periodicals: Journal and Magazine Collection (Contemporary), Copernicus GmbH
Historic
Publication Date:
2009
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications

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Nenes, A., Walker, G. K., Lau, W. K., Wilcox, E., Zhou, Y., Sud, Y. C.,...Kim, K. (2009). Sensitivity of Boreal-summer Circulation and Precipitation to Atmospheric Aerosols in Selected Regions – Part 1: Africa and India : Volume 27, Issue 10 (23/10/2009). Retrieved from http://www.ebooklibrary.org/


Description
Description: Laboratory for Atmospheres, NASA/Goddard Space Flight Center, Greenbelt, MD, USA. Version-4 of the Goddard Earth Observing System (GEOS-4) General Circulation Model (GCM) was employed to assess the influence of potential changes in aerosols on the regional circulation, ambient temperatures, and precipitation in four selected regions: India and Africa (current paper), as well as North and South America (companion paper). Ensemble-simulations were carried out with the GCM to assess the aerosol direct and indirect effects, hereafter ADE and AIE. Each simulation was started from the NCEP-analyzed initial conditions for 1 May and was integrated through May-June-July-August of each year: 1982–1987 to provide an ensemble set of six simulations. In the first set, called experiment (#1), climatological aerosols were prescribed. The next two experiments (#2 and #3) had two sets of simulations each: one with 2X and other with 1/2X the climatological aerosols over each of the four selected regions. In experiment #2, the anomaly regions were advectively restricted (AR), i.e., the large-scale prognostic fields outside the aerosol anomaly regions were prescribed while in experiment #3, the anomaly regions were advectively Interactive (AI) as is the case in a normal GCM integrations, but with the same aerosols anomalies as in experiment #2. Intercomparisons of circulation, diabatic heating, and precipitation difference fields showed large disparities among the AR and AI simulations, which raised serious questions about the proverbial AR assumption, commonly invoked in regional climate simulation studies. Consequently AI simulation mode was chosen for the subsequent studies. Two more experiments (#4 and #5) were performed in the AI mode in which ADE and AIE were activated one at a time. The results showed that ADE and AIE work in concert to make the joint influences larger than sum of each acting alone. Moreover, the ADE and AIE influences were vastly different for the Indian and Africa regions, which suggest an imperative need to include them rationally in climate models. We also found that the aerosol induced increase of tropical cirrus clouds would potentially offset any cirrus thinning that may occur due to warming in response to CO2 increase.

Summary
Sensitivity of boreal-summer circulation and precipitation to atmospheric aerosols in selected regions – Part 1: Africa and India

Excerpt
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