Radiative effects of dust aerosol on West African climate using simulations from RegCM4

Abstract

A regional climate model (RegCM4.4) has been used to investigate the dynamical effect of dust aerosol radiative forcing and its impact on West African climate. The simulations was performed with the non-dust aerosol version of the model (control) and a dust aerosol module for the year 2010. The spatial and temporal distribution of the aerosol optical depth (AOD) derived from the dust run was compared with observed aerosol data from Aerosol Robotic Network (AERONET) and other satellite products. The results from the simulations show that dust aerosol has a significant impact on West Africa Monsoon (WAM) system. The dust particles induced shortwave (SW) radiative forcing exerted a heating effect at the top of the atmosphere (TOA) over the study area during the DJF season and cooling in MAM. In contrast, the dust induced longwave (LW) radiative forcing exerted an atmospheric cooling during dry season of DJF. The LW radiative forcing at the TOA is maximum during JJA season with the core of 4.3 Wm− 2 over the source region (Bodele). The highest degrees of correlation (r > 0.7) between modeled AOD and (AERONET, MODIS, OMI, and MISR) were observed over Cape Verde. Moderate (0.5 < r < 0.7) to poor correlations (r < 0.5) were also observed over Ilorin, Zinder, Dakar, Ouagadougou, Agoufou, and Banizoumbou. Further results over all the stations revealed that, RegCM4.4 underestimates AOD over Ilorin, Zinder, Cape Verde, Ouagadugou, Agoufou, and Banizoumbou when compared with AERONET and satellite observations except in Dakar where it overestimated AOD from MODIS. All the experiments exhibited a remarkable performance over Guinea and whole West Africa with low RMSE and high postive correlation.