A multi-perspective assessment of satellite surface Ozone products in China: Spatiotemporal variability, land cover impacts and pollution monitoring capability

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Accurate Ozone concentration datasets are essential for comprehensively understanding air quality, climate change, and the health and societal impacts related to Ozone exposure. Currently, there is limited research comparing near-surface Ozone concentration products. In this study, we employed continuous evaluation metrics (R2, RMSE, RB) and classified statistical indicators (POD, FAR, CSI) to comprehensively compare and assess three near-surface Ozone concentration products (CHAP O3, LGAP O3, TAP O3) in China from 2015 to 2020. Our findings indicate that CHAP outperforms other products in estimating near-surface Ozone concentration and monitoring Ozone pollution in China. In terms of temporal scale, the three Ozone products exhibited a strong correlation in specific regions across multiple time scales (R2> 0.6). The RMSE values of the products were lower in CHAP, followed by TAP, and higher in LGAP. Notably, LGAP significantly underestimated Ozone concentrations over time. Regarding spatial scale, CHAP and TAP align closely with ground observations, whereas LGAP shows significant underestimation in latitude and longitude, with the discrepancy increasing gradually along the longitude. All three products exhibited strong correlations with measured data at various sites (R2> 0.6). The RMSE and | RB| distributions of CHAP and TAP were similar and superior to LGAP. CHAP and TAP perform better than LGAP under specific land cover types, especially in urban and vegetation-covered areas, while their performance is relatively poorer in farmland-covered areas. Concerning pollution events, CHAP and TAP exhibit strong detection capabilities for Ozone pollution events in the Beijing–Tianjin–Hebei (BTH) region and other majority areas, with POD values exceeding 0.6, and FAR values below 0.1, showcasing excellent CSI performance. In contrast, LGAP has weaker detection capabilities, with POD values primarily in the 0–0.2 range and lower CSI values. This comprehensive evaluation sheds light on the strengths and weaknesses of different near-surface Ozone concentration products and their implications for assessing Ozone pollution in China.