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Air quality has become one of the key environmental issues with its wider impact on our society, economy, industry, diplomacy,

public hearth and natural resources. Especially, Asia with its rapid increase in industrialization and population, has received attention as an important source region of the globe. With its ever increasing emission, air pollution became from local to global problems .

Thus, it is crucial to monitor concentration of relevant gases and aerosols over Asia in high temporal and spatial resolution. A geostationary Earth orbit(GEO) satellite, Geostationary Environmental Monitoring Spectrometer (GEMS) was launched successfully in Feb 19th, 2020. GEMS is the first instrument to observe air pollutants concentrations from GEO. The objectives of the GEMS are: (1) To provide atmospheric chemistry measurements in high temporal and spatial resolution over Asia, (2) To monitor regional transport events: transboundary pollution and Asia dust, (3) To enhance our understanding on interactions between atmospheric chemistry and meteorology, (4) To better understand the globalization of tropospheric pollution, (5) To improve air quality forecast by: constraining emission rates / data assimilation of chemical observations.

This group has been in charge of its data processing algorithm for GEMS, based on radiative transfer and inversion theory including optimal estimation, differential optical absorption spectroscopy(DOAS), machine learning etc. GEMS is to be followed by NASA's TEMPO in 2023 and ESA's Sentinel-4 in 2024 to form a geostationary air quality constellation to cover major continents in Northern Hemisphere.

Aerosols affect climate by scattering and absorbing radiation and by altering cloud microphysics known as direct and indirect effect, respectively. Since these impacts occur from local- to global-scale with high spatio-temporal variation, satellite sensors which can observe extensive area with high temporal resolution, have been valuable to monitor their distribution and investigate relevant problems. In our laboratory, retrieval algorithms for aerosols have been developed, and impacts of aerosols on climate and air quality have been investigated by using various satellite sensors including GOCI, MODIS, MISR, TROPOMI, CALIOP, etc.  Machine learning algorithms are also developed to convert the satellite retrievals to surface PM2.5 concentrations. Data fusion has been conducted among different satellite instruments and algorithms for better accuracy and coverage based on big data science.

One of the major factors underlying recent climate change is radiative forcing. Radiative forcing is an externally imposed change in the radiative energy budget of the Earth’s climate system [e.g. IPCC, 2022]. The energy budget is characterized by an approximate balance between shortwave absorption and longwave emission by the climate system [e.g., Kiehl and Trenberth, 1997]. Radiative forcing can affect the either the shortwave or longwave components of the radiative budget. The most important forcings are related to anthropogenic increases in the well-mixed greenhouse gases (WMGHGs) CO2, CH4, N2O, and the halocarbons. Despite continuing uncertainty regarding the magnitude of aerosol radiative forcing [Anderson et al., 2003], it is very likely that the net anthropogenic radiative forcing of the climate system is positive because of the effects of WMGHGs [Boucher and Haywood, 2001]. The increased concentrations of CO2, CH4, and N2O between 1750 and 1998 have produced forcings of +1.66, +0.48, and +0.16 Wm-2, respectively [IPCC, 2007]. Carbonaceous aerosols (black carbon) are also known as a strong absorber of radiation. Thereby our laboratory is focusing on the accurate quantification of radiative forcing for CO2, CH4, and BC using recent satellite remote sensing by GOCI, GOSAT, OCO, MODIS, and OMI.

Ozone layer plays an important role in protecting the global environment by preventing the harmful ultraviolet (UV) rays coming from the sun to the earth’s surface. It is also important because the ozone absorbs ultraviolet light in the upper layer, which directly affects the thermal structure of the atmosphere, ultimately leading to weather or climate change. Our laboratory started observing ozone with Dobson ozone spectrophotometer in May 1984 for the first time in Korea, which is a instrument of the WMO Ozone Observing System (WMO / GAW). We focus on monitoring ozone layer and its variations and harmful UV radiation, together with UV, visible and infrared bands. Also, we do research on the solar radiation process, which is the ultimate energy source of all natural phenomenon. Radiative transfer theory is the basis of remote sensing which helps calculate physical and chemical properties of the atmosphere, the earth surface, and the ocean.