This study aims to evaluate the performance of the latest Regional Climate Model version
4 (RegCM4) to simulate the precipitation over the Horn of Africa. Although there are
several aspects in which the model can be improved, the focus of this study is to tackle the
problem of its moisture scheme. RegCM4 moisture scheme has fourteen moisture scheme
parameters, which can be tuned within the allowed physical limits. Each of the fourteen
moisture parameters have been varied around the current default setting and over 80
model runs have been performed for a domain defined by 60km resolution, 18 vertical
levels covering spatially the whole Africa and the major circulation patterns that derive
climate over the region. We have found physical sound set of moisture scheme parameters
to be used in the fourteen moisture scheme parameters that have significantly reduced
bias in RegCM4 precipitation; improved correlation of RegCM4 precipitation with respect
GPCP and CMAP; and captured seasonal and interannual variations over most of the 12
delineated homogeneous regions of Horn of Africa.