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Impact of the ongoing Amazonian deforestation on local precipitation: A GCM simulation studyNumerical simulation experiments were conducted to delineate the influence of in situ deforestation data on episodic rainfall by comparing two ensembles of five 5-day integrations performed with a recent version of the Goddard Laboratory for Atmospheres General Circulation Model (GCM) that has a simple biosphere model (SiB). The first set, called control cases, used the standard SiB vegetation cover (comprising 12 biomes) and assumed a fully forested Amazonia, while the second set, called deforestation cases, distinguished the partially deforested regions of Amazonia as savanna. Except for this difference, all other initial and prescribed boundary conditions were kept identical in both sets of integrations. The differential analyses of these five cases show the following local effects of deforestation. (1) A discernible decrease in evapotranspiration of about 0.80 mm/d (roughly 18%) that is quite robust in the averages for 1-, 2-, and 5-day forecasts. (2) A decrease in precipitation of about 1.18 mm/d (roughly 8%) that begins to emerge even in 1-2 day averages and exhibits complex evolution that extends downstream with the winds. (3) A significant decrease in the surface drag force (as a consequence of reduced surface roughness of deforested regions) that, in turn, affects the dynamical structure of moisture convergence and circulation. The surface winds increase significantly during the first day, and thereafter the increase is well maintained even in the 2- and 5-day averages.
Document ID
19950051101
Document Type
Reprint (Version printed in journal)
Authors
Walker, G. K. (NASAGoddard Space Flight Center Greenbelt, MD, United States)
Sud, Y. C. (NASAGoddard Space Flight Center Greenbelt, MD, United States)
Atlas, R. (NASAGoddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 16, 2013
Publication Date
March 1, 1995
Publication Information
Publication: American Meteorological Society, Bulletin
Volume: 76
Issue: 3
ISSN: 0003-0007
Subject Category
METEOROLOGY AND CLIMATOLOGY
Distribution Limits
Public
Copyright
Other