Comparison of Temperature Gradient Model Predictions with Recent Rainfall Trends in the Sahel

Abstract

Using the temperature departure data of Angell and Korshover (1978), models relating the movement of the Intertropical Convergence Zone (ITCZ) to hemispheric temperature gradients are compared with rainfall data from the Sahel. The Northern Hemisphere models (Bryson, 1973, 1974; Greenhut, 1977), in general, do not correlate with rainfall. Rainfall is well correlated with meridional temperature gradients taken with constant vertical lapse rate?a result which parallels that of Korff and Flohn (1969) in a study of the motion of the subtropical high. The Southern Hemisphere model relating temperature gradients to ITCZ motion (Kraus, 1977) also is not correlated with rainfall in the Sahel. However, highly significant correlation between rainfall and summer-winter change in the Southern Hemisphere meridional temperature gradient with the latter lagged by 0.5?1 year is evidence that the cross-equatorial transport of energy may be driven to some extent by the movement of the ITCZ in the Northern Hemisphere.