A New Criterion for Locating the Subtropical High in West Africa

Gary K. Greenhut Department of Physics, University of Ghana, Legon, Ghana

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Abstract

After reanalyzing the potential temperature data of Peixoto (1958, 1960), a criterion is derived for locating the mean latitude of the subtropical high over West Africa. Using this criterion, it is found that the subtropical high tends to move to higher latitudes, and therefore the amount of rainfall in the Sahel tends to increase, as the concentration of carbon dioxide and particulate matter in the atmosphere increases. We conclude that increasing amounts of atmospheric pollutants are probably not the cause of the severe drought experienced in the Sahel in the early 1970's. This conclusion contradicts that of Bryson (1973) who used the so called Z criterion to predict an opposite response of the subtropical high to changes in the concentration of atmospheric pollutants.

Abstract

After reanalyzing the potential temperature data of Peixoto (1958, 1960), a criterion is derived for locating the mean latitude of the subtropical high over West Africa. Using this criterion, it is found that the subtropical high tends to move to higher latitudes, and therefore the amount of rainfall in the Sahel tends to increase, as the concentration of carbon dioxide and particulate matter in the atmosphere increases. We conclude that increasing amounts of atmospheric pollutants are probably not the cause of the severe drought experienced in the Sahel in the early 1970's. This conclusion contradicts that of Bryson (1973) who used the so called Z criterion to predict an opposite response of the subtropical high to changes in the concentration of atmospheric pollutants.

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