Droughts in Western Cape : Statistical Analysis of the Trend and Variability in Present-day and Future Climates

Abstract

Drought is one of the most powerful natural disaster. Relation of drought with atmospheric and oceanic phenomena makes it hard to analysis. In this study, the impact of El-Nino Southern Oscillation, In- dian Ocean Dipole and the Solar cycle on the occurrence of drought in the Western Cape have been investigated. To detect dry events from 1901 to 2000, their beginning and severity, the 3-months and 12-months Standardized Precipitation Index (SPI) were used. This is a drought index that can provides different informations for the analysis of drought at different time scale. Dominant cycles were detected by spectral analysis methods. The results of this study show that most of dry events occurred during a cold El Nino Southern Oscillation event and/or a positive Indian Ocean Dipole phase. The influence of the Solar cycle on the occurrence of dry events has been found almost insignificant except during the June-August season.