| 24 Aug 2026
Evolution and drivers of urban–suburban ozone contrasts in China during 2013–2020
Abstract. Urban–suburban surface ozone (O3) differences provide valuable information for understanding the spatial response of O3 to emission reductions, yet their long-term evolution across China remains poorly understood. Here, we combined surface observations with GEOS-Chem simulations to investigate summertime urban–suburban O3 contrasts across China during 2013–2020. Urban and suburban areas were reclassified using a population density threshold, and the contributions of meteorology (Met), anthropogenic emissions (Anth), and biogenic VOCs emissions (Biog) were quantified using sensitivity simulations. Reclassification enlarged the urban–suburban O3 contrast in eastern China but reversed the interpretation in western China from urban O3 enhancement to persistent suburban enhancement. Suburban monitoring sites also underestimated regional suburban O3 trends, indicating limited spatial representativeness. Nationally, suburban O3 increased faster than urban O3 after 2017, weakening the urban–suburban gradient. Attribution revealed distinct controlling mechanisms. In eastern urban areas, Anth enhanced O3 during 2013–2017 under VOCs-limited conditions but became suppressive by 2020 as chemistry shifted toward transitional regimes, while Met dominated recent increases. In eastern suburban areas, Met was the primary driver, whereas Anth consistently suppressed O3 under predominantly NOx-limited conditions. In western China, weak Anth and Biog contributions made Met the dominant driver in both urban and suburban areas. Case studies further demonstrate substantial regional heterogeneity in driver contributions and O3 sensitivity regimes. These findings highlight the importance of robust urban–suburban classification, representative monitoring, and region-specific O3 drivers for developing effective mitigation strategies.
Competing interests: At least one of the (co-)authors is a member of the editorial board of Atmospheric Chemistry and Physics.
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