Influence of weather patterns on ground-level ozone pollution: a 2023 summer case study in Jilin City with health...

Despite extensive studies in major industrial regions, the spatiotemporal behavior of ground-level ozone (O₃) in smaller cities such as Jilin City, China, remains poorly understood, particularly with respect to meteorological variability and health risks. This study examined summertime O₃ formation and the associated population-level risk in Jilin City during May-July 2020 and 2023 by integrating WRF v4.4.1 and CMAQ v5.4 simulations with observations from air quality monitoring stations. Compared with 2020, the 2023 period was characterized by higher temperatures by 1.1-1.5 °C, altered wind regimes, shallower boundary-layer conditions during peak episodes, and anticyclonic circulation, with station-level pressures above 950 hPa, equivalent to approximately 1010-1018 hPa at sea level. These conditions favored precursor accumulation, restricted vertical mixing, and enhanced photochemical O₃ formation. Difference analysis showed that meteorological shifts accounted for 3.89 µg m^-3, or 59.1%, of the 6.59 µg m^-3 domain-wide MDA8 O₃ increase between 2020 and 2023, although the fixed 2020 emission inventory limits complete separation of meteorological effects from post-pandemic emission changes. CMAQ reproduced the broad seasonal and interannual patterns but underestimated peak O₃ concentrations, highlighting the need for improved year-specific emissions and for online representation of biogenic VOCs. Conventional AQI changed only modestly, increasing from 40.62 to 46.22, whereas city-average excess health risk increased from 2.76 to 3.16%, indicating a 14.5% deterioration in population-level risk. Observed seasonal O₃ levels of 68-118 µg m^-3 exceeded the WHO 2021 peak-season MDA8 guideline of 60 µg m^-3. Persistent high-risk hotspots were identified at Hada Bay and Jiuzhan, emphasizing the need for localized, source-differentiated O₃ mitigation strategies.