1997 Articles

Simulated changes in extreme rainfall over southern Africa

Mason, Simon J.; Joubert, Alec

A general circulation model simulation is used to investigate possible changes in rainfall over southern Africa resulting from a doubling of atmospheric carbon dioxide. Simulated increases in rainfall intensity are found to be a spatially coherent and an apparently less regionally dependent signal of climatic change than changes in annual means or number of rain‐days. Accordingly, increases in both the frequency and intensity of extreme daily rainfall events are simulated throughout most of the subcontinent. Simulated increases in the intensity of the lowest frequency floods are shown to be particularly severe, suggesting that greenhouse‐related climatic change may be most detectable through an increase in extreme flood events rather than changes in long‐term means. Similar results are evident when changes in the frequency and intensity of prolonged rainfall events, measured over a period of five consecutive days, are analysed. All results are qualitatively similar to those for the Australian region, except that the model's sensitivity to sharp changes in topography over southern Africa is highlighted.