The Influence of Regcma4 Lateral Boundary Schemes on East African Rainfall
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Date
2012-06
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Addis Ababa University
Abstract
The 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 rainfall
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Keywords
East African Rainfall