5-year Operation of Geostationary Environmental Monitoring Spectrometer (GEMS) for Atmospheric Composition Observation in Asia in High Spatio-temporal Resolution

Satellite remote sensing has played a key role in understanding distribution and changes of atmospheric composition including aerosols, ozone, air pollutants, and greenhouse gases. These contributions have been achieved extensively with Low Earth Orbit (LEO) satellite instruments providing one to two observations per day, including but not limited to MODIS, VIIRS, OMI, TROPOMI, GAOFEN, and so on. Geostationary Environment Monitoring Spectrometer (GEMS) was launched in February, 2020 as the first component of GEO-Ring for atmospheric composition observation from geostationary Earth orbit. GEMS observation is complemented by AMI and GOCI-2 on the same spacecraft for aerosols, and hyperspectral instruments such as Chinese GIIRS. NASA’s TEMPO was launched in 2023 over North America and ESA’s Sentinel 4 UVN was launched in 2025 over Europe, to establish the GEO ring of Air Quality observation. GEMS has provided hourly observation of key air quality components, including aerosol, ozone, and their precursors such as NO2, HCHO, SO2 etc. In this talk, achievements of GEMS observations to monitor atmospheric composition of aerosol and gases from GEMS are presented with algorithm updates and validation results. Achievements and related issues with GEMS observations are discussed for further improvements and harmonization of dataset for the GEO-RING.