The Influence of Synoptic Weather Patterns on Spatiotemporal Characteristics of Ozone Pollution Across Pearl River Delta of Southern China

Tropospheric ozone (O-3) pollution is becoming the primary obstacle to the improvement of air quality in China, especially in the Pearl River Delta (PRD) region. Because O-3 pollution episodes are closely related to synoptic weather patterns (SWPs), historical episodes (from 2006 to 2019) were classified according to SWPs using the Lamb-Jenkinson method. Monitoring network and weather reanalysis data, emission inventories, and satellite retrievals were used to investigate the spatiotemporal characteristics and influences of O-3 pollution. It was found that easterly (P_E), anticyclone (P_A), and typhoon-related (P_NE) SWPs accounted for 75% of all O-3 pollution episodes. In the PRD, the O-3 formation mechanism showed clear differences under different SWPs, which were affected by local emissions under P_A, whereas regional transmission dominated under P_E and P_NE. The O-3 peak concentration was strongly associated with temperature, solar radiation, and shifting of the sea-land breeze. A delayed shift of land to sea breeze caused by SWPs often caused the O-3 peak to appear in the late afternoon. Finally, stepwise regression was used to explain individual meteorological parameters contributing to O-3 formation. It was found that the formation of O-3 pollution under P_E and P_NE was associated with increases in temperature and radiation, while P_A was mainly affected by the increase of the overnight accumulation of O-3. This study advances our knowledge of the formation mechanism of O-3 pollution and provides scientific support for effective O-3 pollution control.