LAUSR

In the present study, we have investigated the impacts of anthropogenic aerosols on some relevant atmospheric parameters such as temperature, precipitation, wind and shortwave radiation. For this aim, we use the International Centre for Theoretical Physics (ICTP) regional climate model version 4 named RegCM4. Two sets of simulations with 1 year of spin-up, from 2001 to 2006, identical in their structure have been conducted: one includes the interactions of anthropogenic aerosols (ExpA) and another simulation which does not (Exp). In this regard, it should be noted that discrepancies between ExpA and Exp estimate the impact of the aerosol direct effect. The shortwave radiative forcing associated with the anthropogenic aerosols is negative throughout the entire domain with more negative values up to −6 W m-2 over the latitudinal band 0°–10°N during DJF accordingly to the main sources region. This induces cooling at surface higher than 0.4 °C. Elsewhere over the raining area, the effect on precipitation is largely negative and the reduction can reach up to 1 mm day−1. Moreover, the atmospheric circulation is not systematically affected even though we note a variation of wind speed in the vicinity of the latitudinal band 6°–10°N resembling a dipole pattern. The results also highlight that irrespective of the season, aerosols lead to enhance the moisture divergence mostly over the Guinea Gulf around Nigerian and Cameroonian coasts. This study provides evidence that anthropogenic aerosols influence climate variability and hydrological cycle mostly during dry season.