Seasonal to Decadal Prediction of Southern African Climate and Its Links with Variability of the Atlantic Ocean

Abstract

A review of the interannual to interdecadal variability of the southern African region and its links with the Atlantic is given. Emphasis is placed on modes such as the Benguela Nĩno that develop within the Atlantic and may have some predictability. Seasonal forecasting and climate prediction efforts within the region are discussed. Most southern African countries rely on a combination of products obtained overseas and simple statistical methods. GCM based forecasts and statistical downscaling of their outputs are used operationally in South Africa and also applied to some neighboring countries. A review of these downscaling efforts and their various applications is given. Research is also taking place into the predictability of quantities such as the onset of the rainy season (which appears to be associated with anomalous South Atlantic anticyclonic ridging) and dry spell frequencies within it. These parameters are often more useful to farmers in the region than forecasting above- or belowaverage seasonal rainfall totals. A strong link between dry spells and Nĩno-3.4 SST is evident for certain regions of southern Africa, suggesting that some predictability exists. This link is weaker for countries like Namibia and Angola that border the Atlantic than for southeastern Africa. It is concluded that some aspects of southern African climate variability may have predictability but considerably more research is needed to better understand the influence of variability over the Atlantic. An added concern is the ongoing reduction in data collection in many parts of southern Africa. This reduction has serious implications for model development and validation, and for the accuracy of reanalysis products.