Mengistu, Gizaw (PhD)Mekonnen, Tamene2018-07-042023-11-092018-07-042023-11-092012-06http://10.90.10.223:4000/handle/123456789/6263The latest version of the International Center for Theoretical Physics (ICTP) Regional climate model version 4 (RegCM4) is used to study the in uences of ve di erent Lateral Boundary Schemes (LBSs) on the simulated rainfall for a period of 20 years. The rainfall from RegCM4 simulations under the ve LBSs are compared with the observed rainfall in Climate Research Unit (CRU) and Global Precipitation Climatology Project (GPCP) dataset. The spatial domain encompasses the whole continental Africa and includes the Indian and south Atlantic ocean basins to capture the major circulation features dominating eastern Africa. The comparison of the model results of rainfall with observations from CRU and GPCP indicates a wet bias over east African highlands while a dry bias is observed over the east African lowlands for all cases. The mean annual cycle of rainfall is well captured over east African subregions for each LBSs. The mean annual cycle also indicates that some part of the east African countries are characterized by bimodal rainfall trend which is well captured by all simulations. The observed precipitation inter- annual variability is well reproduced by the regional model over most regions, although RegCM4 simulations show some de ciencies. It is found that the use of sponge as well as the exponential LBSs reproduces realistic rainfall as exhibited by good agreement with GPCP and CRU rainfallenEast African RainfallThesis