Controls on the interannual variability of rainfall over western equatorial Africa

The rainfall regime of western equatorial Africa is strongly heterogeneous with respect to interannual variability, despite broad similarities of magnitude and seasonal cycle throughout the region. This study has produced an objective regionalization as a first step in evaluating the dynamic causes of rainfall variability. The result is a set of five regions homogeneous with respect to this variability. The spatial boundaries of the regions are modified seasonally. An examination of the links to sea-surface temperatures shows that causal factors are both regionally and seasonally specific, with the Atlantic, Pacific and Indian Oceans all playing a role. This remote boundary forcing plays a role via its effect on the major circulation features influencing the region as a whole.