DROUGHTS OVER SOUTHERN AFRICA IN A DOUBLED-CO2 CLIMATE

Abstract

The southern African region is susceptible to climatic extremes and particularly to extended dry periods. Possible changes in the probability of dry years under doubled-CO2 conditions are examined using output from the CSIRO nine-level general circulation model. Changes in annual mean rainfall are not expected to be significant. However, the model simulates an increase in the probability of dry years in the tropics, to the south-west of the subcontinent, as well as over the western and eastern parts of South Africa and southern Mozambique, where large percentage increases in the most intense dry spells are indicated. A decrease in the frequency of dry years is simulated over much of the interior of the subcontinent south of 10°S. In regions where the frequency of dry years decreases, the most severe events occur less often. The CSIRO nine-level model indicates a shift in the frequency distribution of daily rainfall events under doubled-CO2 conditions. A small change in the frequency distribution of daily rainfall events may have further implications for the frequency of mid-summer droughts during the peak summer rainfall period of December–February. Increases in the frequency of mid-summer droughts are simulated over the eastern part of the subcontinent south of 20°S.