Abstract
Accurately estimating ground-level ozone (O₃) concentration is essential for understanding its health impact and designing effective control strategies. Current estimates rely heavily on polar-orbit satellites, which provide limited, one-time measurements and fail to capture the significant diurnal variability of O₃. In this study, we leverage the next-generation geostationary satellite equipped with ultraviolet capabilities, the Geostationary Environment Monitoring Spectrometer (GEMS), to retrieve O₃ concentration on an hourly basis. Besides accurately capturing hourly-level O₃ concentration (with R² = 0.94), this approach significantly improved the accuracy of daily maximum 8-hour average O3 estimates, particularly in semi-urban regions, enhancing the R² by over 0.10 and reducing absolute error exceeding 7 µg/m³. Moreover, our analysis indicates a 30% reduction in O₃-related health risks, with a total reduction in both short-term and long-term mortality compared to previous estimates based on traditional polar-orbit satellites. This reduction is particularly notable in semi-urban and rural areas, where satellite data plays a more important role due to the lack of ground measurements compared to urban areas. This suggests that previous estimates may have significantly overestimated not only the total mortalities but also the urban-rural spillover effects. Our results underscore the importance of utilizing high temporal resolution geostationary satellites with refined hourly information on photochemical precursors and radiation to accurately capture O₃ diurnal variability, providing a scientific foundation for health assessments and informing standards and regulatory interventions to combat O₃ pollution in China.