GEMS Hourly Ozone Data: Enhancing MDA8 Estimates and Reducing Overestimated Health Risks

Accurate estimation of ground-level ozone (O₃) concentration is crucial for assessing its health impacts and devising effective control strategies. Traditional methods relying on polar-orbit satellites offer limited, single-time measurements, failing to capture the significant diurnal variability of O₃. This study utilizes the Geostationary Environment Monitoring Spectrometer (GEMS), a next-generation geostationary satellite, to retrieve hourly O₃ concentrations. The GEMS data not only accurately captures hourly O₃ levels (R² = 0.94) but also significantly enhances the precision of daily maximum 8-hour average (MDA8) O₃ estimates, particularly in semi-urban regions, with an increase in R² by over 0.10 and a reduction in absolute error exceeding 7 μg/m³. Furthermore, our analysis reveals a 30% decrease in O₃-related health risks, with both short-term and long-term mortality rates lower than previous estimates based on polar-orbit satellites. This reduction particularly notable in semi-urban and rural areas, where satellite data is more critical due to the scarcity of ground measurements compared to urban areas. These findings suggest that previous assessments may have overestimated total mortalities and urban-rural spillover effects. Our study highlights the importance of employing high temporal resolution geostationary satellites like GEMS to accurately capture O₃ diurnal variability, providing a robust foundation for health risk assessments and guiding regulatory interventions to address O₃ pollution in China.