资源环境科技发展态势分析平台

Anthropogenic emissions were greatly constrained during COVID‐19 lockdown in China. Nevertheless, observations still showed high loadings of fine particles (PM_2.5) over northern China with secondary aerosols increasing by 15 μg/m³ yet a ∼10% drop in light‐absorbing black carbon (BC). Such a chemical transition in aerosol composition tended to make the atmosphere more scattering, indicated by satellite retrieved aerosol absorption optical depth falling by 60%. Comparison between weather forecast and radiosonde observations illustrated that, without upper‐level heating induced by BC, the stabilized stratification diminished, which was conducive for PBL mixing and thus near‐surface pollution dispersion. Furthermore, coulped dynamic‐chemistry simulations estimated that emission reduction during the lockdown weakened aerosol‐planetary boundary layer (PBL) interaction and thus a reduction of 25 μg/m³ (∼50%) in PM_2.5 enhancement. Based on the unique natural experiment, this work observationally‐confirmed and numerically‐quantified the importance of BC‐induced meteorological feedback, further highlighting the priority of BC control in haze mitigation.