Simulation of West African monsoon using the RegCM3. Part I: Model validation and interannual variability |
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Authors: | E A Afiesimama J S Pal B J Abiodun W J Gutowski Jr A Adedoyin |
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Institution: | (1) WMO Regional Meteorological Research Institute, Lagos, Nigeria;(2) International Centre for Theoretical Physics, Trieste, Italy;(3) Federal University of Technology, Akure, Nigeria;(4) Iowa State University, Iowa, USA;(5) University of Botswana, Botswana |
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Abstract: | Summary The West African monsoon oscillates each year with remarkable regularity but the interannual variability associated with the
monsoon is not fully understood although much progress has been made in recent years. This study examines and evaluates the
mean state and the interannual variability of the West African climate as simulated by the International Centre for Theoretical
Physics (ICTP) Regional Climate Model version 3 (RegCM3) over the period 1979 through 1990 using the National Center for Environmental
Prediction (NCEP)/National Center for Atmospheric Research (NCAR) reanalysis data as lateral boundary conditions.
Our analysis shows that the averaged rainfall over the region is well represented by the model and demonstrates considerable
skill in reproducing the extreme rainfall regimes.
There is however a tendency to overestimate rainfall amounts along the Guinean coast, particularly around mountainous areas,
and to underestimate it over the Soudano-Sahel. The increased rainfall along the coast is due to an enhanced low-level convergence
of the moist southwesterly winds along the coast leading to a reduction of the moisture content in the atmosphere. The decrease
over the Soudano-Sahel could be associated with the weakening of the land–sea temperature gradient and hence the decrease
in the low level southerly flows. The spatial and temporal variations in temperature are well captured by the model except
for slightly cold bias over the coastal region due to an overestimation of precipitation. |
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