Mechanisms of high-temperature ozone suppression in Eastern China: a meteorological perspective

Abstract Ozone (O 3 ) is a typical secondary photochemical pollutant, whose production typically increases under high temperature and radiation. However, emerging observational evidences reveal a notable alteration in the O 3 -temperature relationship under extremely heat conditions (referred to as O 3 suppression) in 20%–30% cities of China, yet the underlying mechanisms and driving forces remain unclear. This study provides a comprehensive investigation of the meteorological mechanisms driving high-temperature O 3 suppression in Eastern China, with particular emphasis on regional disparities between suppression and non-suppression areas. Our analysis revealed distinct spatial patterns of O 3 suppression across major Chinese regions. The Yangtze River Delta (YRD) and Pearl River Delta (PRD) regions exhibit significant O 3 suppression, with the O 3 -temperature relationship decreasing by 3–5 μ g m −3 °C −1 at high temperatures. In contrast, the Beijing–Tianjin–Hebei (BTH) region rarely illustrates this phenomenon. Through integrated statistical analysis and machine learning approaches, we identified radiation, relative humidity (RH), and planetary boundary layer height (PBLH) as the key meteorological drivers. Mechanistic analysis demonstrated that RH was the dominant factor accounting for regional differences in O 3 suppression, primarily owing to the contrasting effects of dry heat (BTH) and wet heat (YRD and PRD). PBLH emerged as a secondary influential factor that modulates O 3 concentration through the competitive effects of diffusion and transport processes. Cluster analysis further revealed that the occurrence frequency of inhibitory meteorological conditions (high RH and low PBLH) during high-temperature days in the YRD and PRD regions (25%–35%) significantly exceeded that in the BTH region (2%). This study provides crucial insights into the regional disparities in meteorological mechanisms underlying high-temperature O 3 suppression and offers valuable scientific support for region-specific O 3 pollution control strategies in the context of climate warming and increasingly frequent heatwaves.