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Originally published in Science Express on 9 October 2003
Science 7 November 2003:
Vol. 302. no. 5647, pp. 1027 - 1030
DOI: 10.1126/science.1089357
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Reports

Oceanic Forcing of Sahel Rainfall on Interannual to Interdecadal Time Scales

A. Giannini,1*{dagger} R. Saravanan,1 P. Chang2

We present evidence, based on an ensemble of integrations with NSIPP1 (version 1 of the atmospheric general circulation model developed at NASA's Goddard Space Flight Center in the framework of the Seasonal-to-Interannual Prediction Project) forced only by the observed record of sea surface temperature from 1930 to 2000, to suggest that variability of rainfall in the Sahel results from the response of the African summer monsoon to oceanic forcing, amplified by land-atmosphere interaction. The recent drying trend in the semiarid Sahel is attributed to warmer-than-average low-latitude waters around Africa, which, by favoring the establishment of deep convection over the ocean, weaken the continental convergence associated with the monsoon and engender widespread drought from Senegal to Ethiopia.

1 National Center for Atmospheric Research, Boulder, CO 80305, USA.
2 Department of Oceanography, Texas A&M University, College Station, TX 77843, USA.



{dagger} Present address: International Research Institute for Climate Prediction, Palisades, NY 10964, USA.

* To whom correspondence should be addressed. E-mail: alesall{at}iri.columbia.edu

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