1. Climate System Analysis Group Simulating the Characteristics of Extreme Rainfall Events in Southern Africa using Regional Climate Models Babatunde J. Abiodun Sabina Abbar Omar and Arlindo Meque Climate System Analysis Group (CSAG) Department Environmental and Geographical Science University of Cape Town (South Africa) Presented by: Kamoru A. Lawal

2. Climate System Analysis Group Study Domain: Southern Africa Cape Town Western Cape Mozambique

3. Climate System Analysis Group City of Cape Town

4. Climate System Analysis Group Impacts of Extreme Rainfall Events in Cape Town

5. Climate System Analysis Group Impacts of Extreme Rainfall Events in the Western Cape Displacement of communities Damages to infrastructure Loss of lives Damaging extreme rainfall event remains a big threat in the Western Cape.

6. Climate System Analysis Group Causes of Extreme Rainfall in the Western Cape Kalahari trough Mid-latitude cyclone Cut-off low Tropical Temperate Trough Agulhas Current

7. Climate System Analysis Group Aim and Objectives Examine the capability of regional climate models (RCMs) in simulating the characteristics of widespread extreme rainfall events (WERE) over the Western Cape Examine how GCM boundary forcing may alter the characteristics of the simulated WERE.

8. Climate System Analysis Group Simulation and observation Datasets SMHI-RCA PRECISREMO CRCM5 RACMO CCLM ARPEGE ERAINT CCMA NCC ICHEC MIROC MPI CNRM REGCM3WRF CORDEX RCMs SMHI- RCA TRMM GPCP ERA-Interim

9. Climate System Analysis Group Extreme rainfall event: defined at each grid point as rainfall above the 95 th percentile of daily rainfall at the grid point Widespread extreme rainfall event (WERE): defined as a simultaneous occurrence of extreme rainfall events over at least 60% of the Western Cape area (i.e. about 60 grid points). Methods

10. Climate System Analysis Group Simulated and observed threshold of extreme rainfall over Southern Africa (mm/day) There are notable differences between GPCP and TRMM results Only four RCMs (CRCM5, RCA3,WRF and REMO) perform better than ERAINT in simulating the observed threshold pattern

11. Climate System Analysis Group Frequency distribution of rainfall over the Western Cape

12. Climate System Analysis Group Seasonal distribution of widespread extreme rainfall over the Western Cape GPCP and ERAINT report different total number of WERE. Among the RCMs, PRECIS reports the highest number the WERE, while CCLM reports the lowest number.

13. Climate System Analysis Group The classification of the observed and simulated WERE, using the Self Organizing Map (SOM), shows four main groups of WERE over the Western Cape 1 2 3 4

14. Climate System Analysis Group The frequency of WERE in each SOM node as observed (GPCP and TRMM) and simulated (ERAINT and RCMs).

15. Climate System Analysis Group The sensitivity of RCA-simulated WERE over the Western Cape to GCM forcing All the WEREs are link to mid-latitude rainfall activities

16. Climate System Analysis Group Conclusion Only four RCMs perform better than ERAINT in simulating the threshold of extreme rainfall over Southern Africa All RCMs underestimate the extreme rainfall threshold over the Western Cape The RCMs perform very well in simulating the seasonal variation of WERE over the Western Cape, but perform poorly in simulating the inter-annual variability. When forced with ERINT, all RCMs reproduce the four main pattern of WERE in the Western Cape, but when forced GCM, RCA model reproduces only one pattern.

17. Climate System Analysis Group Thank you!!! babiodun@csag.uct.ac.za