First Year Observations of Air Quality from Geostationary Environment Monitoring Spectrometer (GEMS)

Hourly observations of air quality (AQ) over Asia has been available by the Geostationary Environment Monitoring Spectrometer (GEMS) for the first time from a geostationary Earth orbit (GEO) since its launch in February 2020. After 8-month in orbit tests, the first light images were released in November, 2020. GEMS has observed column amounts of atmospheric pollutants (O3, NO2, SO2, HCHO, CHOCHO, and aerosols) to capture their diurnal variations with the UVvisible spectrometers at 0.6 nm spectral resolution and sophisticated retrieval algorithms. Details of the first year of GEMS mission are presented, including calibrations, results, validations, and case studies including volcanic eruption, dusts, and urban pollution. The Advanced Meteorological Imager (AMI) and Geostationary Ocean Color Imager 2 (GOCI-2) are onboard the Geostationary Korea Multi-Purpose Satellite 2 (GK-2) satellite series with GEMS, which can now provide synergistic science products to better understand air quality, the long-range transport of air pollutants, emission source distributions, and chemical processes. Faster sampling rates at higher spatial resolution increase the probability of finding cloud-free pixels, leading to more observations of aerosols and trace gases than has been possible from LEO. GEMS will be joined by NASAs Tropospheric Emissions: Monitoring of Pollution (TEMPO) and ESAs Sentinel-4 to form a GEO AQ satellite constellation in 2022 and 2023, respectively, as recognized by the Committee on Earth Observation Satellites (CEOS).