Aerosol effects during heat waves in summer 2022 and responses to emission change over China

This study explores aerosol direct, indirect, and feedback effects on meteorology and fine particulate matter during August 2022 heat waves over eastern China using an online coupled regional climate–chemistry–aerosol model. Mean direct (DRE) and indirect (IRE) radiative effects at the top of atmosphere (TOA) were −3.9 and −2.4 W m⁻², respectively, leading to an average surface air temperature decrease of 0.3 °C over east China, decreases in PBL height and precipitation, and an increase in PM₂.₅ concentration. With anthropogenic emission reductions from 2013 to 2022, DRE decreased markedly while IRE changed little, resulting in a 27% decrease in total radiative effect (TRE) at TOA. The weakened TRE increased surface air temperature and precipitation by 0.14 °C and 2.7 mm, respectively, on average over east China, with maximum warming exceeding 0.5 °C in the Beijing–Tianjin–Hebei (BTH) region. The results highlight a warming trend from weakened TRE that may exacerbate heat waves, and an increasing importance of aerosol IRE relative to DRE due to weak cloud sensitivity to aerosol changes during emission reductions.