Rainfall Variability in Equatorial and Southern Africa: Relationships with Sea Surface Temperatures along the Southwestern Coast of Africa

Abstract

This article presents the results of an analysis of sea surface temperature (SST) fluctuations in the upwelling region along the Benguela coat and its relationship to rainfall variability both along the coast and throughout equatorial and southern Africa. The analysis incorporates compositing and time series analysis. Coastal rainfall is markedly enhanced during warm-water years and suppressed during cold-water years. The effects are strongest in March and April; at some stations, March totals of 50 mm in cold-water years contrast with 200 to 400 mm in March of warm-water years. Spectral analysis shows the variability of SSTs to be more pronounced on time scales of 5 to 6 years, and strong relationships with rainfall throughout equatorial and southern Africa are evident on this time scale. In coastal regions there may be some degree of direct local forcing of rainfall anomalies via SST anomalies, but the temporal and geographical patterns of the relationships suggest that in general, both SSTs and rainwall probably respond to common atmospheric forcing mechanisms.