Historical rainfall variability in selected rainfall stations in Eastern Cape, South Africa

Abstract

There is evidence of climate shifts in Africa shown by changing rainfall patterns, temperatures and increased fire incidences. As such, the annual rainfall variability for 41 years (1970–2010) for nine stations at Amakhala reserve, Grahamstown, Bathurst, Port Alfred, Uitenhage and Port Elizabeth in Eastern Cape, South Africa was studied through trend and time series analysis. In order to identify the trends for extreme rainfall events, the daily rainfall index (DI), highest daily rainfall and frequency of dry and wet spells for the stations were also analysed. Pearson's product moment correlation test was used to compute relationships between measured parameters over the years. Results showed a declining trend in annual rainfall over time at Grahamstown (r = − 0.59), Uitenhage and Bathurst (r = − 0.32), while Amakhala, Port Alfred and Port Elizabeth remained unchanged. Most of the rainfall declines occurred in the 1980s and 1990s sub-periods, with both the DI and daily rainfall subclasses above 10 mm showing similar declines. The frequency of dry days decreased with time at Port Alfred and Uitenhage, while the length of dry spells increased at Bathurst (r = +0.41). Reports from the literature suggest that the 1970s–1990s rainfall variations were due to the El Niño southern oscillation cycle and sea surface temperatures over the Atlantic and Indian Oceans, which gave drier conditions during El Niño and wetter than normal conditions during La Niño events.