The influence of el Nino/la Nina on rainfall in equatorial and southern Africa

This paper examines the influence of El Nino and la Nina episodes on rainfall in equatorial and southern-hemisphere Africa, using the harmonic method developed by Ropelewski and Halpert (1982). Composite patterns of rainfall during the course of the two-year duration of a typical episode are determined, using 20 el Nino episodes and 17 la Nina episodes of the period 1901 to 1990. While el Nino tends to produce drought over southern Africa and heavy rainfall over eastern equatorial Africa, the opposite pattern prevails during la Nina. This pattern is evident in roughly 4 of 5 episodes. The patterns of SSTs in the Atlantic and Indian Oceans are critical determinants of whether or not the anticipated rainfall fluctuations occur in conjunction with a given el Nino or la Nina event.