Statistical Associations Between African Rainfall and ENSO-Monsoon Circulations

Rainfall patterns and trends over Africa are analysed using principal component analysis and the leading modes are identified and related to environmental variables over the adjacent tropical oceans and their monsoon circulations. Simultaneous and six month lead multi-variate models are formulated and the influential variables are studied. For the zero lag models the tropical Indian Ocean is important. At six month lead the tropical Atlantic comes into play. Between 15 and 35% of the variance can be explained, mainly by atmospheric variables which interact with changes in sea surface temperature (eg. wind, pressure). Interrelationships between the most influential environmental variables are analysed. It is found that anti-phase sea surface temperatures either side of Africa are closely related to upper zonal winds and ENSO phase. A conceptual model is presented which contributes to climate prediction efforts across Africa.