Contrasting ozone-response patterns across Chinese cities driven by meteorology and emissions during the warm season.

Understanding how urban ozone responds to meteorological variability is essential for explaining spatial heterogeneity in ozone pollution and developing region-specific mitigation strategies. Previous studies have primarily focused on identifying dominant meteorological drivers, whereas much less attention has been devoted to understanding why comparable meteorological anomalies produce contrasting ozone responses. Here, we integrated interpretable machine learning with meteorological normalization to investigate warm-season ozone variability across six cities representing typical ozone-polluted regions of China during 2018-2023. Multi-timescale analyses revealed distinct ozone-response patterns governed by nonlinear interactions between meteorological conditions and local precursor emissions. Beijing and Shijiazhuang (in the North China Plain) exhibited a temperature-amplification pattern that hotness strongly enhanced photochemical ozone production, whereas Shanghai and Wuhan (in the mid-low reaches of the Yangtze River) exhibited a humidity-regulated pattern in which atmospheric moisture retarded ozone formation despite elevated temperatures. Taiyuan (in the Fen-Wei River Plain) exhibited a precursor-regulated pattern, while Chengdu (in the Sichuan Basin) was characterized by a stagnation-dominated accumulation pattern. These contrasting ozone-response patterns further explained regional differences in heatwave-induced ozone enhancement by revealing distinct pathways of ozone evolution under extreme meteorological conditions. Heatwaves were not consistently accompanied by ozone pollution across cities, with the dynamic evolution of dominant drivers reflecting markedly different ozone responses to comparable thermal anomalies. Interannual ozone variability exhibited substantial city-dependent differences in meteorological modulation, with meteorological contributions ranged from approximately -12% to +10% across cities, highlighting pronounced heterogeneity in ozone sensitivity to meteorological variability. These findings provide a deeper understanding of why urban ozone responds differently to meteorological variability across cities and offer a scientific basis for regionally adaptive ozone management under a warming climate.