A comparative study to reveal the influence of typhoons on the transport, production and accumulation of O<sub>3</sub> in the Pearl River Delta, China

Abstract. The Pearl River Delta (PRD) region in South China is faced with severe ambient tropospheric ozone (O3) pollution autumn and summer, which mostly coincides the occurrence of typhoons above Northwest Pacific. With increasingly O3 PRD under influence typhoons, it necessary to gain a comprehensive understanding impact on transport, production accumulation for efficient reduction. In this study, we analysed general via systematic comparisons meteorological conditions, processes sources days without typhoon (denoted as typhoon-induced no-typhoon scenarios, respectively) also examined differences these influences summer. results show that approach was accompanied by higher wind speeds strengthened downdraughts autumn, well inflows more polluted air masses suggesting favourable transport conditions scenario both seasons. However, effect were distinct. Typhoons led reduced cloud cover, thus stronger solar radiation accelerated production, but shorter residence time local unfavourable within PRD. contrast, increased weakened radiation, restraining formation, growing favoured accumulation. modelling using Community Multiscale Air Quality (CMAQ) model typical suggest increasing contributions from outside pollution, confirming enhanced process analysis CMAQ chemical contributed less summer Since cannot be at same time, proportion emissions likely decrease difference can attributed seasonal variation East Asian monsoon. From meteorology–process–source perspective, study revealed complex their differences. To alleviate influence, emission control needed larger scale, rather than only