Influences of ENSO and SST variations on the interannual variability of rainfall amounts in southern Africa

Relationships between southern Africa rainfall, the El Nino-Southern Oscillation (ENSO) and sea surface temperatures (SSTs) were investigated. Principal Components Analysis (PCA) on rainfall amounts established coherent regions. Results of correlation analysis between rainfall and the Southern Oscillation Index (SOI) and regional SST anomalies indicated strong influences of ENSO and the Tropical Indian Ocean and moderate influences of the Southwest Indian Ocean. The ENSO influence was consistently, moderately negative in equatorial Southern Africa during October-January, strongly positive in the Tropical/Subtropical areas during February-April and highest for light and moderate events in the south and for intense events in the north. SSTs in the Tropical Indian Ocean influence light and moderate events, while SSTs close to the region influence heavy events. Sliding correlations indicated changing rainfall-SOI/SST relationships in the mid-1950s which improved the associations, and since the early-1970s which deteriorated or reversed the relationships.