Recent-year variations in O pollution with high-temperature suppression over central China.

By analyzing environmental and meteorological monitoring data over recent years of 2015-2022, the Twain-Hu Basin (THB) in central China was identified as a regional O pollution center over China with the highest increasing trend at 1.10 %⸱yr in interannual variations of O concentrations with deteriorating O pollution over recent years. We explored the spatiotemporal variations in O pollution in the THB with ozone suppression (OS) under high air temperature over metropolitan, small urban, and mountainous areas. The bipolarized interannual trends in interannual O variations in urban and mountainous areas over central China were characterized with the increasing and decreasing 90th percentiles of the daily maximum 8-h (MDA8-90) O concentrations respectively in polluted urban areas and clean mountainous areas over recent eight years. The changes of the near-surface O concentrations with air temperature exhibited the inflection points of OS from increasing to decreasing O at air temperature of 30.5 °C in mountainous areas, 32.5 °C in small urban areas, and 34.5 °C in metropolitan areas, and the intensity of OS was estimated in the ranking with mountainous areas (-2.30 μg⸱m⸱°C) > small urban areas (-1.96 μg⸱m⸱°C) > metropolitan areas (-1.54 μg⸱m⸱°C), indicating that the OS was more significant over the lower-O mountainous areas. This study has implications for understanding O pollution variations with the meteorological drivers.