%0 Journal Article
%T An Advanced Review of the Relationships between Sahel Precipitation and Climate Indices: A Wavelet Approach
%A Churchill Okonkwo
%J International Journal of Atmospheric Sciences
%D 2014
%I Hindawi Publishing Corporation
%R 10.1155/2014/759067
%X The interannual and decadal to multidecadal variability of precipitation in western Sahel region was examined using wavelet transform and coherency analysis. The aim was to identify the major climate index that has a robust relationship with Sahel precipitation (drought). The results show that ENSO, North Atlantic Oscillation (NAO), Atlantic Multidecadal Oscillation (AMO), and Indian Ocean Dipole (IOD) all have some relationship with precipitation at different time scales which is in agreement with recent studies. There is an antiphase relationship between Sahel precipitation and ENSO at the 3-4-year band localized around 1982/83 El Ni£¿o episode. This indicates a cause and effect relationship between the droughts of 1983 and 1982/83 El Ni£¿o. In addition, wavelet transform coherence analysis also revealed a relatively antiphase relationship between AMO and precipitation signifying cause and effect. The wavelet analyses indicate that IOD control on rainfall variability in Sahel is limited to the east (15¡ãE¨C35¡ãE). Advancing this understanding of variability in rainfall and climate forcing could improve the accuracy of rainfall forecast. 1. Introduction Several authors have reported marked interannual variability in rainfall across Africa [1¨C3]. Since economic development in the region is highly dependent on water availability [4], the effect of climate variability on rainfall is critical [5]. Western Sahel region (latitudes 14¡ãN and 18¡ãN¡ªlongitude £¿18¡ãW to 10¡ãW) is the semiarid transition zone between the Sahara desert and humid tropical Africa that is prone to drought [6, 7]. The Disaster Management Center (DMC) [8] reported that more than 900,000 people were severely affected by the devastating drought of the 1970s across the Sahel. The associated social and economic consequence of drought such as failure in crop yield, destruction of pasture, and famine has led to a series of studies exploring the interactions and dynamics that control precipitation within the region. Over the past three decades, studies on the possible causes of drought in Sahel have focused on forcing by either sea surface temperature (SST) or land-atmosphere interaction. Simulations of hydrological impact of land-atmosphere interactions include [9¨C12] which all attributed reduced rainfall to degradation of land surface at least in part. Li et al. [12] confirmed the impact of land surface changes on the regional climate through a feedback mechanism that sustains drought. The contribution of these mechanisms has however been exaggerated [13, 14] especially the characterization of
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