Change in Daily Extremes in the Early Future over Southern Africa Using RegCM4 Regional Climate Model

Friday, 19 December 2014
Ismaila Diallo, Cheikh Anta Diop University, Dakar, Senegal, Filippo Giorgi, Abdus Salam International Center for Theoretical Physics, Trieste, Italy and Frode Stordal, University of Oslo, Meteorology, Oslo, Norway
We discuss a present day (1990-2009) and near future (RCP 4.5, 2010-2029) simulation for the southern Africa region with the RegCM4 regional climate model (RCM, dx = 25 km) driven by the CAM4 global climate model (GCM, dx = 1°).The analysis focuses on mean climate as well as a series of temperature and precipitation extreme indices. With a few exceptions we find that the models reproduce reasonably well the mean and extreme climatology of temperature and precipitation over the region, with the RegCM4 improving the simulation of daily precipitation frequency and duration of dry and wet events compared to CAM4 due to its higher resolution. In the near future simulation both models show a warming of up to 2 degrees locally. In addition, both models show an increase in maximum and minimum temperature extremes and a prevailing shift towards a hydroclimatic regime of more intense and less frequent precipitation events. The global and regional models exhibit quite different patterns of bias and change, an indication of the importance of internal variability and process representation for the simulation of surface climate. Given the good performance shown by the nested CAM4-RegCM4 system, we plan to use these models to generate an ensemble of projections for use in impact assessment studies for the region.