An assessment of moisture based drought indices in CORDEX Africa simulations

We investigate possible changes in moisture availability from 1961- 2100 on a regional scale for the African continent under the representative concentration pathways (RCP) 4.5 and 8.5 scenarios. Eight CMIP5 coupled atmospheric general circulation models (AOGCMs) namely CanESM2, CNRM-CM5, HadGEM2-ES, NorESM1-M, EC-EARTH, MIROC5, GFDL-ESM2M and MPI-ESM-LR, with spatial resolution varying from about 1° to 3° are downscaled to 0.44° resolution by the Rossby Centre (SMHI) regional climate model RCA4. The downscaled RCA4 ensemble is compared with the coarser driving AOGCM ensemble to investigate potential advantages of increased horizontal resolution in RCA4. We also evaluate the spatial and temporal variability of the moisture based indices for different climate zones of Africa and inter-compare them to assess their level of agreement in a changing climate. Results show that the regional model generally tends to reduce spread in the simulations compared to the driving global models. The level of agreement between the indices is also found to be influenced by regional factors. The experimental layout allows us to explore how uncertainties in future climate change are related to forcing scenarios and to driving AOGCMs at different periods. The study also illustrates the usefulness of CORDEX simulations in identifying possible future impacts of global change at local and regional scales. Keywords: Drought, Climate change, Africa, RCM, CORDEX, RCP