Evaluating the surface shortwave radiative impact of african landscape fires

Wildfires are an important Earth system process with far-reaching impacts. The African continent is responsible for over 70% of all landscape burning worldwide, and over 10% of African land burns every year. The work presented here uses satellite data to investigate the effects of landscape fires in Africa on surface albedo, how these changes affect the surface shortwave radiative balance, and what the associated change in surface temperature is. Surface albedo is found to decrease immediately after a landscape burn due to the charring of the surface, with a continental average decline of 0.019±0.001. Albedo recovers exponentially thereafter, and some level of surface brightening is observed in the long term because of vegetation removal; this is especially prominent in the Kalahari region. Land cover types with higher tree cover experience less albedo change, faster recovery and less brightening after a fire. Landscape fires are found to cause a significant instantaneous surface shortwave radiative forcing (RF), with the average warming effect in fire affected pixels peaking at 4.5±1.7 Wm-2. RF decreases after a fire, following a recovery similar to post-fire albedo. In months 5-10 after a fire, the continent-wide RF is small and negative, driven almost exclusively by behaviour in the Kalahari region. Land surface temperature (LST) increases immediately after a fire, with an average peak LST anomaly of 1.9±0.6 K. This change cannot be explained by the albedo-induced radiative forcing only, suggesting the latent heat flux is also affected by fire. This causes additional heating at the surface, especially in areas with higher tree cover and moderate to high soil moisture. The analysis of 20 years of data reveals few trends in all variables investigated, largely due to high interannual variability of fire and other variables across the continent.