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<p>Tropospheric ozone (O<sub>3</sub>) remains a critical air quality challenge in China despite effective reductions in PM<sub>2.5</sub> levels. This study investigates the phenomenon of Ozone Suppression (OS) under high-temperature conditions across six major urban agglomerations in China—Beijing-Tianjin-Hebei (BTH), Yangtze River Delta (YRD), Pearl River Delta (PRD), Cheng-Yu (CY), Middle Yangtze River Delta (MYR), and Middle Plain (MP)—from 2015 to 2024. Using a <i>Z</i>-test, we identified the cutoff temperature (<i>T</i><sub>c</sub>) for OS events and analyzed its spatiotemporal variability. Results revealed significant regional differences, with <i>T</i><sub>c</sub> ranging from 28.0&#xa0;°C to 35.3&#xa0;°C, higher in plains and lower in coastal and plateau regions. An XGBoost model was developed to predict daily maximum 8-hour O<sub>3</sub> (O<sub>3</sub>-8&#xa0;h) under OS, demonstrating strong performance (CV-R<sup>2</sup>: 0.69–0.85, CV-RMSE: 18.12–23.37&#xa0;µg·m<sup>− 3</sup>). SHAP analysis quantified the relative contributions of meteorological, anthropogenic, and natural factors. Key drivers included PM<sub>2.5</sub>, 2-m temperature (t2m), and meridional wind (v10), with pronounced regional heterogeneity: PM<sub>2.5</sub> dominated in MYR, PRD, and YRD, while t2m, surface solar downwards (ssrd), and 2-m dew point (d2m) were primary in BTH, CY, and MP, respectively. Meteorological factors contributed 39.0%–66.2% to O<sub>3</sub>-8&#xa0;h variations. These findings underscore the need for region-specific ozone control strategies tailored to localized drivers under warming climate conditions.</p>

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Changes and drivers of ozone suppression in warm seasons in China’s six major urban agglomerations over the past decade

  • 期刊论文

  • 发表日期：

    2026年1月16日

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  • Xiaoyong Liu,
  • Jun Yan,
  • Fangcheng Su,
  • Xiaofang Pan,
  • Wei Wei,
  • Hui Gao

摘要

Tropospheric ozone (O3) remains a critical air quality challenge in China despite effective reductions in PM2.5 levels. This study investigates the phenomenon of Ozone Suppression (OS) under high-temperature conditions across six major urban agglomerations in China—Beijing-Tianjin-Hebei (BTH), Yangtze River Delta (YRD), Pearl River Delta (PRD), Cheng-Yu (CY), Middle Yangtze River Delta (MYR), and Middle Plain (MP)—from 2015 to 2024. Using a Z-test, we identified the cutoff temperature (Tc) for OS events and analyzed its spatiotemporal variability. Results revealed significant regional differences, with Tc ranging from 28.0 °C to 35.3 °C, higher in plains and lower in coastal and plateau regions. An XGBoost model was developed to predict daily maximum 8-hour O3 (O3-8 h) under OS, demonstrating strong performance (CV-R2: 0.69–0.85, CV-RMSE: 18.12–23.37 µg·m− 3). SHAP analysis quantified the relative contributions of meteorological, anthropogenic, and natural factors. Key drivers included PM2.5, 2-m temperature (t2m), and meridional wind (v10), with pronounced regional heterogeneity: PM2.5 dominated in MYR, PRD, and YRD, while t2m, surface solar downwards (ssrd), and 2-m dew point (d2m) were primary in BTH, CY, and MP, respectively. Meteorological factors contributed 39.0%–66.2% to O3-8 h variations. These findings underscore the need for region-specific ozone control strategies tailored to localized drivers under warming climate conditions.