South African droughts and decadal variability

We explore the historical occurrence of extensive droughts over South Africa within the context of decadal climate variability. A Standardized Precipitation Index dataset is developed and used to assess the spatial extent of droughts in South Africa for the period 1920–2014. The most extensive droughts over the period at various time scales are identified and discussed. Results of a wavelet analysis are also presented towards identifying statistically significant regional climate variation with which the occurrence of droughts is associated. The occurrence of drought with respect to the El Niño Southern Oscillation and decadal climate variability is also considered. Significant associations between short-term droughts and decadal variability are pointed out. An overview of global sea surface temperature and Southern Hemisphere sea-level pressure associations with three prominent scales of multi-year climate variability is given. Dry epochs at the most prominent time scales are shown to be significantly negatively related to the Southern Annular Mode and associated sea surface temperature anomalies in the mid-to-high southern latitudes. Relations with the Pacific Decadal Oscillation, Inter-Decadal Pacific Oscillation and ENSO, which are all associated with a Southern Annular Mode of opposite sign, are also highlighted.