Strong reduction in near-surface turbulence due to aerosols in South and East Asia

Absorbing and scattering aerosols influence the vertical temperature profile and can lead to a shallower boundary layer and potentially enhanced surface air pollution. Using a regional chemistry-climate model validated against >1000 air quality monitoring stations, we show that absorbing black carbon (BC) aerosols reduce near-surface turbulence and boundary layer height through aerosol-radiation interactions (ARI). While ARI due to total aerosols lead to enhanced PM_2.5 surface concentrations and 25,000–27,000 annual excess deaths in each of Northern India and Eastern China, ARI due to BC have a modest impact on near-surface PM_2.5 because of its ability for self-lofting and enhanced precipitation affecting wet scavenging. However, over India, BC ARI strongly increase the number of days with combined high temperature and relative humidity, which is dangerous for human health. These results highlight that the multitude of indirect impacts from individual aerosol species need to be considered to achieve efficient mitigation of air pollution.