Smoke-weather Interaction Affects Clouds, Precipitation and Extreme Wildfires in Southeast Asia

The biomass burning in Indo-China Peninsula, caused by agricultural activities, has a significant impact on human lives, air quality, ecosystems, and weather systems. However, it is not fully clear how wildfire can affect weather processes, especially clouds and precipitation formation, which are important for wildfire behaviours. Here we show that biomass burning aerosols aloft strongly increase the low cloud coverage over both land and ocean in subtropical southeastern Asia. The degree of this enhancement and its spatial extent is comparable to that in the Southeast Atlantic, even though Southeast Asia's total biomass burning emissions are only one-fifth of those in Southern Africa. We find that a synergetic effect of aerosol-cloud-boundary layer interaction with the monsoon is the main reason for the strong semi-direct effect and enhanced low cloud formation in southeastern Asia. Moreover, the interactions between smoke and weather can reduce rainfall on Indo-China Peninsula, thus worsening air pollution by enhancing fire emissions and weakening dispersion. The intricate interactions among wildfires, smoke, and weather form a positive feedback loop that substantially increases air pollution exposure.