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Keywords:

  • rainfall variability;
  • Southern Oscillation Index;
  • South Africa

Abstract

This study assesses long-term rainfall records in the KwaZulu-Natal Drakensberg, South Africa's most valuable source of surface runoff. Records from 11 stations covering the Drakensberg region in South Africa indicate that no statistically significant trend in interannual variability existed during the last half of the twentieth century. Annual rainfall in the Drakensberg is highly seasonal, and analysis of monthly rainfall indicates an increase in the variability of the distribution of monthly rainfall and the strengthening of rainfall seasonality in the Drakensberg through a significant decrease in autumn rainfall. The El Niño/Southern Oscillation (ENSO) influences summer rainfall variability of the KwaZulu-Natal Drakensberg, and a strong correlation also exists between summer rainfall and the Southern Oscillation Index (SOI) for preceding periods. This correlation between summer rainfall and ENSO events suggests that changes in the frequency and intensity of the ENSO should affect the rainfall in the Drakensberg. The lagged correlation between summer rainfall in the Drakensberg and the SOI could be used as an indicator for seasonal forecasting. Copyright © 2008 Royal Meteorological Society