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Gary K. Greenhut

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.

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Tom Beer
,
Gary K. Greenhut
, and
S. E. Tandoh

Abstract

We use radiosonde data from Tamale in northern Ghana to evaluate the Z criterion latitude ϕ z . We find it correlates well with other Hadley cell parameters since its variations are apparently controlled by the meridional movement of the subtropical westerly jet. Since the Hadley cell parameters correlate well with Tamale rainfall, we conjecture that it should be possible to predict northern Ghana rainfall on the basis of the southward extension of the subtropical jet once more data have been collected by the Tamale radiosonde. This conjecture is supported by data from other stations in West Africa.

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