Impacts of Meteorological Conditions on Autumn Surface Ozone During 2014–2020 in the Pearl River Delta, China

As one of the largest megacity clusters in China, the Pearl River Delta (PRD) exhibited an obvious increase in the autumn mean maximum daily 8 hr average (MDA8) ozone (O3) concentration from 2014 to 2020, although O3 precursors were effectively controlled. To understand the cause of these elevated surface MDA8 O3 concentrations in the PRD, we explored potential meteorological causes. Based on the relationships between the MDA8 O3 concentrations and the meteorological conditions, the ozone weather index (OWI) was constructed from surface downward shortwave radiation flux (DSWRF), relative humidity (RH), and wind speed (WS) data to represent the variations in the autumn MDA8 O3 concentration in the PRD. Stronger DSWRF, lower RH, and lower WS were linked to larger OWI values and stronger O3 pollution. Discrepancies in DSWRF, RH, and WS were observed on days with OWI > 1 and OWI