Variability of circulation and Sahel rainfall in the twentieth century

Abstract

Variations of rainfall in the West African Sahel and circulation in the tropical Atlantic sector in the course of 1901-2010 are documented in recent data sources. From rainfall index series published for 1901-1984 and 1941-2010, an index series of Sahel rainfall, SHL, was reconstructed for 1901-2010. Consistent with circulation diagnostics, SHL has strong positive correlation with latitude position of the intertropical wind confluence, LAT, and southerly wind component off the coast of West Africa, V, which came with steeper northward pressure and southward temperature gradients. Over the century, SHL experienced a drying trend, accompanying southward shift of LAT and weakening V, which came with weaker northward pressure and southward temperature gradients. The greater temperature rise in the South may be related to greater longwave-induced warming in the region with less cloudiness. Over the twentieth century rains were most abundant in the 1950s, scarcest in the 1980s, and they have still not recovered in the first decade of the new century. © 2013 Royal Meteorological Society.