Assessing the Association Between Unfavorable Meteorological Conditions and Severe PM2.5 and Ozone Pollution

The increasing occurrence of unfavorable meteorological conditions under global warming has significantly impacted urban atmospheric environments, particularly ozone (O3) and fine particulate matter (PM2.5) pollution in densely populated cities. Using nationwide air quality observations and reanalysis data from 2013 to 2022, we assessed the variations in three typical unfavorable meteorological conditions—heatwave (HW), atmospheric stagnation (AS), and temperature inversion (TI)—in Eastern China and their influences on air pollution, as well as the large-scale synoptic drivers behind them. Results indicate that HW and AS events have increased substantially by 9.61 and 1.72 days/decade, leading to remarkable rises in O3 and PM2.5 concentrations. Compound events (e.g., HW + AS and HW + TI) exhibit even stronger synergistic impacts, raising O3 and PM2.5 concentrations by more than 57.34% and 46.76%, respectively, compared to individual events. In addition, by applying the T-mode Principal Component Analysis (T-PCA), this study identified typical synoptic patterns favorable for such conditions and air pollution events. Synoptic patterns such as the northward displacement of Western Pacific Subtropical High (WPSH) were identified as critical large-scale drivers. These findings highlight linkages between unfavorable meteorological conditions and air quality, providing scientific support for air-quality management and pollution control in Eastern China.