Keder Hussen Farah, Chala Hailu Sime , Abdifatah Mohamed Hassen, Usame Mohamed Muhumed

Examining the spatiotemporal dynamics of meteorological variables in the context of changing climate, particularly in countries where rainfed agriculture, and hydropower project are predominant, is vital to assess climate-induced change. CORDEX Africa has been developed to forecast Africa's climate variation and variabilities. the RCA4 regional climate model performance of CORDEX Africa domains have not been evaluated yet. Therefore, this finding is aimed to evaluate RCA4 CORDEX Africa RCMs performance in the Gilgal Gibe Watershed, Omo basin, Ethiopia. The observed rainfall and temperature data for five stations obtained from National Metrological Agent were used for bias correction of the RCMs. First the accuracy of simulation results was evaluated using as suite of statistical measures such as Bias, Root Mean Squared Error (RMSE) and correlation coefficient, and the result was found that the performance of model is satisfactory. After evaluating performance model, the data have been analyzed using coefficient of variation, anomaly index and precipitation concentration index. Furthermore, Mann-Kendell test was used to detect the time series trend. the result revealed that there is non-significantly declining of trend for annual in all stations: -0.0101cm/year, :0.0044cm/year: -0.00441cm/year, 0.0057cm/year, and -0.0939cm/year for Dedo, Assendabo, Sekoru, Omonad and Jimma, respectively. and for maximum and minimum temperature the result has shown that there is significant increasing trend in annually. lastly future climate change (2025-2050) have been investigated, and 60% of stations have shown decrease in annual rainfall under RCP4.5, and RCP8.5 scenario. where temperature of study area has shown that there is increasing monthly maximum and minimum temperature in all stations under RCP4.5, and RCP8.5 scenario.