Rainfall and Atmospheric Circulation during Drought Periods and Wetter Years in West Africa

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  • 1 National Center for Atmospheric Research, Boulder, CO 80307
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Abstract

The semiarid regions of Africa experienced a number of extreme rainfall fluctuations in the present century, most notable of which are the “wet” 1950's and the drought 1968–75. Thirty-seven century-long regional rainfall departure series evidence the continental scale and marked coherence of these anomalies and illustrate important climatic teleconnections. A comparison of sub-Saharan droughts and wetter years suggests that a northward displacement of the Intertropical Convergence Zone (ITCZ) may account for wetter years, but that a weakened “intensity” of the rainy season, independent of ITCZ position, is the most likely cause of drought in the sub-Saharan region. This and the tendency for synchronous fluctuations north and south of the Sahara (i.e., tropical and extratropical regimes) suggest that changes in intensity of the Hadley circulation may be an important factor in West Africa rainfall fluctuations.

Abstract

The semiarid regions of Africa experienced a number of extreme rainfall fluctuations in the present century, most notable of which are the “wet” 1950's and the drought 1968–75. Thirty-seven century-long regional rainfall departure series evidence the continental scale and marked coherence of these anomalies and illustrate important climatic teleconnections. A comparison of sub-Saharan droughts and wetter years suggests that a northward displacement of the Intertropical Convergence Zone (ITCZ) may account for wetter years, but that a weakened “intensity” of the rainy season, independent of ITCZ position, is the most likely cause of drought in the sub-Saharan region. This and the tendency for synchronous fluctuations north and south of the Sahara (i.e., tropical and extratropical regimes) suggest that changes in intensity of the Hadley circulation may be an important factor in West Africa rainfall fluctuations.

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