A comprehensive analysis of aerosol-induced radiative forcing and regional warming patterns in West Africa

Abstract Atmospheric aerosols can cause significant perturbations to the Earth's radiative budget and induce substantial regional climate change. West Africa has experienced substantial warming in recent decades, but the drivers behind this regional warming trend remain uncertain. This study conducts a comprehensive analysis to quantify the aerosol radiative forcings and explore the associated regional warming patterns across West Africa. It further unveils a novel method for assessing aerosol radiative forcing, which takes into account Aerosol Instantaneous Radiative Forcing (Aerosol IRF) and its effects on regional energy balance at the top of the atmosphere and at the earth’s surface. Ten-year Copernicus Atmosphere Monitoring Service (CAMS) reanalysis datasets spanning 2009–2018 were integrated to characterize the spatiotemporal distributions of Aerosol IRF and the impacts on regional climate change. Aerosol-Cloud Interaction at the Top of the Atmosphere shows varying radiative forcings across seasons and regions, ranging from 1.5W/m2 in the Sahel and Sahara Desert to 2.5W/m2 in the Guinea coast during DJF and MAM, suggesting a significant regional warming effect, particularly in the Sahel and Sahara. A reduction value of 1.0 W/m2 during the JJA seasonal period was also observed and this is predominant over Aerosol IRFari of Aerosol-Radiation Interaction. The Longwave spectrum of aerosol IRFari of Aerosol-Radiation Interaction at the surface reveals positive values mostly evident in the Sahel and Sahara Desert regions of West Africa with a minimum value of 0.2W/m2 and maximum value of 0.4W/m2 in some specific locations like Nigeria, Niger, and Chad Republic during DJF and MAM seasonal period indicating warming effects. During JJA, a reduction of -0.5W/m2 suggests cooling effects, predominantly observed over Aerosol-Cloud Interaction at the Surface. A positive correlation between Aerosol IRF and absorption of solar radiation by clouds and atmosphere influences radiative balance at the top of the atmosphere. The low RMSE (0.02) indicates a good fit between Aerosol-Cloud and Aerosol-Radiation Interaction. Conversely, a negative correlation (-0.04) between surface Aerosol IRF and longwave radiation suggests that absorbed shortwave radiation influences emitted longwave radiation. It was also discovered that IRFari of Aerosol-Radiation Interaction can boost regional forcing, which in turn causes warming and probably sets off extreme events in the area. That aerosol IRFaci seasonal variability can be reinforced by IRFari. In West Africa, regional aerosol effects must be taken into account when developing climate policies and initiatives. Reducing anthropogenic aerosol emissions can both ameliorate air pollution improve air quality and also mitigate regional climate impacts.