Long‐term variations of circulation in the tropical Atlantic sector and Sahel rainfall

Following diagnostic work two decades ago, this study examines the long-term variations of rainfall in the West African Sahel and the underlying circulation mechanisms over the past century. Raingauge measurements bear out DRY regimes during 1910–1919 and 1979–1988 and WET regimes during 1950–1959 and 1999–2008. In the WET as compared to the DRY regimes the cross-equatorial winds from the Southern Hemisphere are enhanced, consistent with lower surface pressure over the tropical North Atlantic, which in terms of hydrostatic forcing plausibly accompanies warmer surface waters, with cooling/warming leading pressure rise/drop in the tropical North Atlantic and DRY/WET in the Sahel. The controls of the observed long-term variations of sea surface temperature in the tropical North Atlantic must remain target of further diagnostic evaluation. Copyright © 2010 Royal Meteorological Society