Ozone (O3) 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 O3-temperature relationship under extremely heat conditions (referred to as O3 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 O3 suppression in Eastern China, with particular emphasis on regional disparities between suppression and non-suppression areas. Our analysis revealed distinct spatial patterns of O3 suppression across major Chinese regions. The Yangtze River Delta (YRD) and Pearl River Delta (PRD) regions exhibit significant O3 suppression, with the O3-temperature relationship decreasing by 3–5 μg 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 O3 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 O3 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 O3 suppression and offers valuable scientific support for region-specific O3 pollution control strategies in the context of climate warming and increasingly frequent heatwaves.

Read original article

Read original article