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International Journal of Geophysics
Volume 2011 (2011), Article ID 259529, 14 pages
http://dx.doi.org/10.1155/2011/259529
Observed Change in Sahel Rainfall, Circulations, African Easterly Waves, and Atlantic Hurricanes Since 1979
1Utah Climate Center, Utah State University, Logan, UT 84322, USA
2Department of Plants, Soils, and Climate, Utah State University, Logan, UT 84322, USA
Received 1 April 2011; Revised 1 August 2011; Accepted 26 August 2011
Academic Editor: Amadou Gaye
Copyright © 2011 Shih-Yu Wang and Robert R. Gillies. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Here, we examine the dynamic properties associated with the recent increase in the Sahel rainfall using an ensemble of five global reanalysis datasets (1979–2010). The rainfall that has been observed to be increasing over the Sahel is accounted for by enhancements in both the tropical easterly jet and the African easterly jet, both of which are known to induce wet anomalies. Moreover, positional shifts in the African easterly jet and African easterly waves (AEWs) accompanied the northward migration of the Sahel rainband. Change in the African easterly jet and AEWs are coupled to a northward shift and amplification of convective activity; this signals an increased potential for the occurrence of flash floods along the northern Sahel. In addition, the result from a wave tracking analysis suggests that the change in AEWs is closely linked to increased activity of intense hurricanes in the North Atlantic. The synoptic concurrence of AEWs in driving the dynamics of the Sahel greening and the increase in tropical cyclogeneses over the North Atlantic is an important aspect in the evaluation of climate model projections.