Synoptic and meteorological drivers of regional ozone pollution events in China

Surface ozone (O-3) pollution events are becoming more frequent and have recently emerged as a severe air pollution problem in China. However, the spatial-temporal distribution of surface O-3, as well as its primary synoptic and meteorological drivers, remains poorly understood. The purpose of this study was to identify the key synoptic and meteorological drivers of O-3 pollution in different regions of China. To achieve this goal, this study established meteorology overlaps of regional O-3 pollution events in space and time and applied a comprehensive statistical model selection method for optimal synoptic and meteorological models, based on a newly released O-3 dataset for 2015-2018. It was observed that extreme regional O-3 pollution events (duration >7 d) occurred more frequently and exhibited a high co-occurrence frequency (>50%) with air stagnation (AS). Moreover, the beginning and end of 69% of the regional O-3 pollution events coincided with regional daily maximum temperature changes. The intensity of AS is the dominant driver of O-3 pollution event intensity across most of the six selected megacity regions. Although other meteorological drivers, such as the intensity of hot days (HD) and meridional wind of 10 m were also important, their impacts varied according to the region. Overall, increase in extreme AS and HD led to the worsening of regional O-3 pollution events. These findings imply that mitigating regional O-3 pollution should consider changing synoptic and meteorological conditions.