Geostationary Satellites Total Ozone Observations: First Results on Ground-Based Networks Validation Efforts for TEMPO and GEMS.

The Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument, launched in April 2023, is North America's first geostationary air pollution monitoring satellite mission. Together with Asia's Geostationary Environment Monitoring Spectrometer (GEMS) launched in 2020 and Europe's upcoming Sentinel-4, TEMPO contributes to nearly global coverage provided by geostationary satellite constellation. TEMPO and GEMS offer hourly, high-resolution data of ozone surpassing the once-daily observations of instruments like the TROPOspheric Monitoring Instrument (TROPOMI) in temporal resolution. This study presents TEMPO's total ozone data, demonstrating TEMPO's ability to observe sudden changes in ozone and UV index. Furthermore, TEMPO and GEMS measurements are validated using ground-based monitoring networks (Brewer, Dobson, and Pandora). Results show good agreement but also highlight latitude-dependent discrepancies between the satellite and ground-based data sets (-2% to 2% for TEMPO, -1% to -3% for GEMS). Findings are further validated using TROPOMI data and reanalysis models.