%0 Journal Article
%T Relationship of Sahel Precipitation and Atmospheric Centers of Action
%A Sultan Hameed
%A Nicole Riemer
%J Advances in Meteorology
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/953853
%X The dynamics associated with drought in the Sahel have attracted considerable attention in the recent literature. This paper evaluates Sahel precipitation using the paradigm of the atmospheric centers of action, that is, the extended semipermanent highs and lows that dominate regional circulations and are evident in sea level pressure patterns. We find that Sahel precipitation is significantly influenced by changes in the Azores High and the South Asia Low. Specifically, about 50 percent of the variance of July to September rainfall over the Sahel is explained by changes in the Azores High Longitude position and South Asia Low pressure. In contrast, the contribution of the Southern Oscillation to Sahel precipitation is smaller in comparison. Results presented in this paper suggest that a key test for a climate model in simulating variability of Sahel rainfall is the accuracy with which the model simulates the dynamics of South Asia Low and the Azores High. 1. Introduction Since the 1950s, the semiarid African Sahel zone has undergone a persistent drought, although there is some amelioration observed since the 1980s. Several theories on the cause of this phenomenon have been discussed, with a final conclusion and a quantification of human versus natural causes still to be reached. The Sahel drought does not only have devastating consequences for the Sahel region itself [1], but it also influences regions far away because of the increased output of soil-derived aerosol particles into the atmosphere [2, 3]. Soon after the drought in Sahel became known as a major climatic phenomenon, Angell and Korshover [4] analyzed the trends in the atmospheric centers of action and suggested that ¡°the southward or southeastward movement of the Azores High after 1945 is related to the recent drought just south of the Sahara (Sahelian Zone).¡± Later other more local processes were put forth as influencing Sahel rainfall such as changes in albedo due to land use change [5], the amount of moisture in the soil [6], and the surface roughness [7]. These can be influenced by overgrazing or deforestation, which led to the hypothesis that human activity contributes to the continuing drought by impacting the land surface processes, and which in turn affect atmospheric circulation. More recently, several global climate models have been used to study Sahel precipitation by using the paradigm that the Sahel rainfall responds to sea surface temperature changes in certain ocean basins [8, 9]. Some models have been used to make projections for Sahel precipitation in the future under
%U http://www.hindawi.com/journals/amete/2012/953853/