Abstract:
The outputs from the Global Climate Models (GCMs) and Regional Climate Models (RCMs) have been used worldwide to predict the evolution of extreme weather events such as floods and droughts. In this study the spatial and temporal characteristics of historical, current as well as future meteorological drought trends are computed using the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI). Statistical and trend analysis done using SPI time series derived from rainfall observations have shown that most parts of South Africa experienced moderate to severe droughts between 1981 and 2015. Gridded monthly precipitation data from the Tropical Rainfall Measuring Mission (TRMM) satellite was used to compute the SPI at each grid point of the domain. The computed SPI was used to obtain drought monitoring indicators such as drought intensity (DI), drought severity (DS), drought duration (DD) and drought frequency (DF) for the period 1998-2015. Results have shown decreasing (negative) trends in drought intensity and duration over most parts of South Africa mainly in provinces such as Gauteng, Limpopo, Free State and North West province. Furthermore results shows that SPI/SPEI computed using data from in-situ observations as well as the SPI computed using data from TRMM reproduced most of the major drought episodes that occurred in South Africa during 1981-2015. Additionally, the ensemble mean of climate simulations obtained when the Rossby Centre for regional climate model (RCA4) is forced by nine GCM models was used to compute the Standardized Precipitation Evapotranspiration Index (SPEI) during the reference period (1971-2000) and future projections (2011-2040 and 2041-2070) under Representative Concentration Pathways (RCP 8.5). Statistical and trend analysis were done using drought intensity, severity, duration and frequency. Moreover, results show an overall increase in drought intensity, duration, severity and frequency during the two future periods 2011-2040 and 2041-2070 under RCP 8.5. Future studies will focus on the impact based assessment in order to complete the drought preparedness and mitigation plan.
