HR: 1330h
AN: PP52A-0944    [PDF]
TI: Sahel Precipitation Variability and Global Sea Surface Temperature Forcing
AU: * Bach, D E
EM: dbach@princeton.edu
AF: Department of Geosciences, Princeton University, 1 Guyot Hall, Princeton, NJ 08544 United States
AU: Kushnir, Y
EM: kushnir@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, P.O. Box 1000 61 Route 9W, Palisades, NY 10964-1000 United States
AU: Seager, R
EM: seager@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, P.O. Box 1000 61 Route 9W, Palisades, NY 10964-1000 United States
AU: Goddard, L
EM: goddard@iri.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, P.O. Box 1000 61 Route 9W, Palisades, NY 10964-1000 United States
AU: Giannini, A
EM: alesall@iri.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, P.O. Box 1000 61 Route 9W, Palisades, NY 10964-1000 United States
AB: In the last 50 years or so, the Sahel region in sub-Saharan Africa has experienced two multi-decadal wet and dry periods separated by a relatively sharp transition. The onset of the dry episode in the Sahel is associated with the start of a significant warming trend in Southern Hemisphere sea surface temperatures (SST) that persisted well into the late 1990's. It has been stipulated, based on general circulation model (GCM) experiments, that the SST rise in the southern ocean basins is the predominant driver of rainfall patterns over the Sahel. Here we support this notion by comparing the observed rate of change in Southern Hemisphere SST with that of Sahel summertime rainfall. We examine the variations in each ocean basin separately and find that the drought pattern is most prominently associated with SST changes in the Indian Ocean, which display maximum warming rates simultaneously with the wet to dry shift in the Sahel. We provide further support to the role of the Indian Ocean using results from GCM integrations forced with observed Indian Ocean SST values and climatological values elsewhere, which effectively recreate the dry Sahel rainfall pattern. While the variations in equatorial Pacific SST associated with El Ni¤o have been found to have an effect on Sahel rainfall during the summer months, their influence does not appear to be significantly connected with the prolonged drought episode. The dry period was accentuated by two severe droughts in the early 1970's and 1980s, which generated very different repercussions for the Sahelian people. The first drought resulted in widespread famine and death while the second more severe drought in 1983-84 generated very few casualties. The political and socioeconomic assessment of these episodes suggests that the extensive loss of life was due to inefficient transportation of supplies to the starving populations. International aid organizations initiated famine protection programs following the 1970's drought that helped to effectively counteract devastating famine in the 1980's.
DE: 1635 Oceans (4203)
DE: 1699 General or miscellaneous
DE: 4203 Analytical modeling
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting