A Study of Aerosol Effects on Clouds Development and Precipitation Processes over Far-North Cameroon Using WRF-Chem

The Weather Research and Forecasting Model coupled with Chemistry (WRF-Chem) was utilized to examine the effects of aerosols on cloud microphysical properties and precipitation development. Three sensitivity tests were designed by changing the weight of anthropogenic emissions. The increase in the number concentration of aerosols resulted in the formation of more numerous and smaller cloud droplets, through which the optical properties of the clouds were changed. While shortwave cloud forcing is reduced in more polluted tests, changes in aerosol concentration have an insignificant incidence on longwave cloud forcing. The net radiative cloud forcing highlighted the contribution of aerosols to the greenhouse effect. In more polluted tests, cloud water content increased whereas rainwater content decreased, and as for ice water content; no real change was observed. It is found that; cloud fraction is reduced in more polluted tests. Results obtained showed a significant variation in precipitation as the aerosol concentration changed. The domain-averaged accumulated rainfall and the maximum accumulated rainfall in the clean and polluted tests decreased compared to that in the control test. When the weight of anthropogenic emission was increased by 10 times compared to that of the clean test, moderate and heavy rains increased compared to light rains in the Far North region of Cameroon; implying that in certain areas and under certain conditions, the inclusion of aerosols leads to an increase in rainfall, especially for moderate and heavy rainfalls.