Sensitivity of different convection schemes in RegCM4.0 for simulation of precipitation during the Septembers of 1989 and 1998 over West Africa

The regional climate model of the International Centre for Theoretical Physics (RegCM4.0) was used to simulate the climate of West Africa. The convective schemes Kuo, Massachusetts Institute of Technology-Emanuel (Ema) and Grell with closures Arakawa-Schubert (Grell 1) and Fritch Chappel (Grell 2) were tested for sensitivity during Septembers of 1989 and 1998 which succeeded a strong La Nina and El Nino, respectively. The general circulation of the atmosphere, the prevailing winds at different pressure levels, position of inter-tropical convergence zone during its descent were well captured by all the convection schemes. All the convection schemes gave good spatial representation of rainfall but not without biases. Kuo and Grell 1 underestimated the observed precipitation; Ema overestimated the observed values in most regions both in 1989 and 1998 while Grell 2 simulated monthly precipitation nearest to the observed CRU and GPCP gridded precipitation data set. The regional distribution of observed precipitation during the September 1998 (which succeeded a strong El Nino) was exactly opposite to the ones for the 1989 (which succeeded a strong La Nina) but none of the convective schemes could mimic the opposite regional distribution.