Evaluation the Performance of Regional Climate Models in Simulating Rainfall Characteristics over Upper Awash Sub-Basin, Ethiopia

Abstract

To obtain reliable estimates of the likely impacts of climate change on the hydrological regime in the bas in determination of the most appropriate climate model was needed. This study aims to evaluate the performance dynamically downscaled simulations of General Circulation Models (GCMs) by Regional Climate Models (RCMs) over Upper Awash sub-basin. The evaluation is based on how well the RCMs simulate the characteristics of the rainfall pattern in Upper Awash sub-basin for the period of 1985 to 2005. For performance assessment the observed rainfall data was obtained from National Meteorological Agency of Ethiopia. Future climate data from CORDEX Africa was dynamically downscaled and corrected for bias using delta change approach. The models were evaluated using statistical measures such as coefficient of variation (CV), root mean square error (RMSE), correlation coefficient and bias. Findings of this study indicates that the MPI-ES-LR climate model performed best in terms of correlation coefficient and CNRM-CM5 best in terms of coefficient of variations. All models were found best in capturing the observed rainfall, but no individual model is best in all performance measures. The ensemble of models is better in simulating the characteristics of rainfall rather than individual models and best in all performance measures. Therefore, in order to capture different aspects of the basin rainfall it is recommend to use ensemble of models simulations rather than individual model.