Sensitivity experiments of RegCM4 simulations to different convective schemes over Central Africa

Abstract

In this study, version 4 of the International Centre for Theoretical Physics (ICTP) regional climate model named RegCM4 is used to perform 6 years simulation including 1 year for spin-up (from January 2001 to December 2006) over Central Africa using four convective schemes: The Emmanuel scheme (MIT), the Grell scheme with Arakawa-Schulbert closure assumption (GAS), the Grell scheme with Fritsch-Chappell closure assumption (GFC) and the Anthes-Kuo scheme (Kuo). We have investigated the ability of the model to simulate precipitation, surface temperature, wind and aerosols optical depth. Emphasis in the model results were made in December–January–February (DJF) and July–August–September (JAS) periods. Two subregions have been identified for more specific analysis namely: zone 1 which corresponds to the sahel region mainly classified as desert and steppe and zone 2 which is a region spanning the tropical rain forest and is characterized by a bimodal rain regime. We found that MIT scheme shows a better index of agreement in temperature, but it generally has a tendency to an overestimation of other simulated parameters. Overall, GAS scheme is more suitable to downscale the aforementioned parameters except temperature, as well as the diurnal cycle of precipitation everywhere over the study domain irrespective of the seasons. In JAS, model results are similar in the representation of regional wind circulation. Apart from the MIT scheme, all the convective schemes give the same tendencies in aerosols optical depth simulations. Additional experiment reveals that the use of BATS instead of Zeng scheme to calculate ocean flux appears to improve the quality of the model simulations.