Jhoon Kim, Yonsei University
Diurnal variations of aerosol properties have been observed extensively from meteorological imagers in Geostationary Earth Orbit (GEO). To date, no observations of trace gases at high temporal resolution from GEO have been made to complement the high temporal resolution aerosol measurements. Geostationary Environment Monitoring Spectrometer (GEMS) is scheduled for launch on February 18th, 2020 to monitor Air Quality (AQ) in Asia at an unprecedented spatial and temporal resolution from a GEO for the first time. With the development of UV-visible spectrometers at sub-nm spectral resolution and sophisticated retrieval algorithms, estimates of the column amounts of atmospheric pollutants (O3, NO2, SO2, HCHO, CHOCHO and aerosols) can be obtained. With UV-visible instruments on GEO platforms, the diurnal variations of these pollutants can now be determined. Details of the GEMS mission are presented, including instrumentation, scientific algorithms, predicted performance, and applications for air quality forecasts through data assimilation. GEMS will be onboard the GEO-KOMPSAT-2B satellite, which also hosts Geostationary Ocean Color Imager (GOCI)-2. Advanced Meteorological Imager (AMI) was launched in December, 2018 and is in operational phase. These three instruments will provide synergistic science products to better understand air quality, meteorology, the long-range transport of air pollutants, emission source distributions, and chemical processes. Faster sampling rates at higher spatial resolution will increase the probability of finding cloud-free pixels, leading to more observations of aerosols and trace gases than is possible from LEO. GEMS will be joined by NASA's TEMPO and ESA's Sentinel-4 to form a GEO AQ satellite constellation in early 2020s, coordinated by the Committee on Earth Observation Satellites (CEOS).