This study examines O₃ and PM_2.5 emission-reduction responses in different regions and under different local weather types in the Beijing–Tianjin–Hebei region in July 2020, using a regional atmospheric chemistry model with NOx–VOCs reduction scenarios and paired simulations with and without aerosol feedback. Co-pollution mainly occurred under weak ventilation and warm-humid boundary-layer conditions, with daily mean temperature of about 23–29°C, relative humidity of about 50%–85%, and planetary boundary layer height of about 0.5–0.9 km. Compared with all samples, co-pollution samples showed concurrent increases of about 8–12 μg m⁻³ in PM_2.5 and 8–15 ppb in MDA8 O₃. The FNR (HCHO/NO2) was mostly 0.15–0.30, indicating that O₃ formation was generally VOC-limited. Regional analysis showed that rural areas were the most responsive to emission reduction, with continuous decreases in both O₃ and PM_2.5 as reduction levels increased. Urban areas showed weaker responses and higher rebound risk, and the additional benefit became smaller at higher reduction levels. Suburban responses were between rural and urban. Based on ventilation, thermal structure, and humidity characteristics, the local weather was classified into five types which are Convective (unstable and well-mixed), Stable_Inv (strong temperature inversion), Neutral_WarmHumid, Neutral_DryHot, and Neutral_Cool. The reduction effects differed across weather types: larger O₃ decreases were found under Stable_Inv and Neutral_WarmHumid/Neutral_DryHot conditions and O₃ rebound was more likely under Convective and Neutral_Cool conditions, while PM_2.5 decreased in most scenarios, with stronger reductions under Neutral_DryHot and Stable_Inv conditions. Aerosol feedback generally increased PM_2.5 reduction but induced O₃ rebound during most hours. Overall, the results show clear dependence of co-pollution response on region, weather type, and aerosol feedback.
 

PM2.5–O3 compound pollution, WRF-Chem, emission scenarios, weather types