Clarifying the relationship between PM2.5 and ozone complex pollution and synoptic patterns in a typical petrochemical city in the Bohai Rim region of China: Implications for air pollution forecasting and control

Meteorological conditions are vital to PM2.5 and ozone (O3) complex pollution. Herein, the T-mode principal component analysis method was employed to objectively classify the 925-hPa geopotential height field of Dongying from 2017 to 2022. Synoptic patterns associated with four pollution types—namely, Only PM2.5 pollution, Only O3 pollution, Co-occurring of PM2.5 and O3 pollution, Non-occurring of PM2.5 and O3 pollution—were characterized at different time scales. The results indicated that synoptic classes conducive to Only PM2.5 pollution were "high-pressure top front", "offshore high-pressure rear", and "high-pressure inside", while those conducive to Only O3 pollution were "offshore high-pressure rear", "subtropical high", and "high and low systems". The Co-occurring of PM2.5 and O3 pollution were influenced by high pressure, and the Non-occurring of PM2.5 and O3 pollution were linked to precipitation and strong northerly winds. The variation in dominant synoptic patterns is crucial in the frequency changes of the four pollution types, which was further validated through the analysis of typical cases. Under the favorable meteorological conditions of high-pressure control with strong northerly winds or a subtropical high and inverted trough both with strong precipitation, there is potential to achieve coordinated control of PM2.5 and O3 in Dongying. Additionally, measures like artificially manipulating local humidity could be adopted to alleviate pollution levels. This study reveals the importance of comprehending the meteorological factors contributing to the formation of PM2.5 and O3 complex pollution for the improvement of urban air quality in the Bohai Rim region of China when emissions are high and the concentration of air pollutants exhibits high meteorological sensitivity. 摘要 本文研究了中国环渤海地区典型石化城市东营市近年来PM2.5与臭氧复合污染的天气形势特征. 结果表明, 有利于促发PM2.5单独污染的环流形势与高压顶前部型, 海上高压后部型, 高压内部型有关; 有利于促发臭氧单独污染的天气型与海上高压后部, 副高和高低值系统有关; PM2.5和臭氧双高污染的发生主要受高压系统的控制; 不利于PM2.5和臭氧污染发生的环流类型则与降水和较强的偏北风有关. 优势天气型的变化是导致四种污染类型发生频率变化的重要因素. 研究结果揭示了当一次排放处于高位, 且空气污染物浓度变化具有高气象敏感性的情况下, 弄清PM2.5和臭氧复合污染的气象成因对于中国环渤海地区城市空气质量持续改善的重要意义.