Enhanced PM(2.5) Decreases and O(3) Increases in China During COVID‐19 Lockdown by Aerosol‐Radiation Feedback

We apply an online‐coupled meteorology‐chemistry model (WRF‐Chem) embedded with an improved process analysis to examine aerosol‐radiation feedback (ARF) impacts on effectiveness of emission control due to Coronavirus Disease 2019 (COVID‐19) lockdown over North China Plain. Emission reduction alone induces PM(2.5) decrease by 16.3 μg m(−3) and O(3) increase by 10.2 ppbv during COVID‐19 lockdown. The ARF enhances PM(2.5) decrease by 2.7 μg m(−3) (16.6%) and O(3) increase by 0.8 ppbv (7.8%). The ARF‐induced enhancement of PM(2.5) decline is mostly attributed to aerosol chemistry process, while enhancement of O(3) rise is ascribed to physical advection and vertical mixing processes. A set of sensitivity experiments with emission reductions in different degrees indicate that the ARF‐induced enhancements of PM(2.5) declines (O(3) rises) follow a robust linear relationship with the emission‐reduction‐induced PM(2.5) decreases. The fitted relationship has an important implication for assessing the effectiveness of emission abatement at any extent.