High-resolution mapping of SO2 using airborne observations from the GeoTASO instrument during the KORUS-AQ field study: PCA-based vertical column retrievals

• Published in: Remote sensing of environment Vol. 241; p. 111725
• Main Authors: Chong, Heesung, Lee, Seoyoung, Kim, Jhoon, Jeong, Ukkyo, Li, Can, Krotkov, Nickolay A., Nowlan, Caroline R., Al-Saadi, Jassim A., Janz, Scott J., Kowalewski, Matthew G., Ahn, Myoung-Hwan, Kang, Mina, Joiner, Joanna, Haffner, David P., Hu, Lu, Castellanos, Patricia, Huey, L. Gregory, Choi, Myungje, Song, Chul H., Han, Kyung Man, Koo, Ja-Ho
• Format: Journal Article
• Language: English
• Published: Goddard Space Flight Center Elsevier Inc 01.05.2020; Elsevier; Elsevier BV
• Subjects: Aerosols; Air quality; Air quality measurements; Airborne instruments; Airborne remote sensing; Airborne sensing; Algorithms; Backscattering; Emission; Environmental monitoring; Field study; GEMS; Geosciences (General); GeoTASO; High resolution; In situ measurement; Industrial plant emissions; Iron and steel plants; KORUS-AQ; Mapping; Meteorological satellites; Optimization; PCA technique; Petrochemicals industry; Plumes; Point source pollution; Power plants; Principal components analysis; Radiation measurement; Satellite observation; SO2; Solar radiation; Spatial discrimination; Spatial distribution; Spatial resolution; Steel industry; Sulfur; Sulfur dioxide; Temperature; Trace gases; Ultraviolet radiation; Airborne remote sensing; GEMS; GeoTASO; SO2; KORUS-AQ; PCA technique
• ISSN: 0034-4257; 1879-0704
• DOI: 10.1016/j.rse.2020.111725

The Geostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) instrument is an airborne hyperspectral spectrometer measuring backscattered solar radiation in the ultraviolet (290–400 nm) and visible (415–695 nm) wavelength regions. This paper presents high-resolution sulfur dioxide (SO2) maps over the Korean Peninsula, produced by SO2 retrievals from GeoTASO measurements during the Korea–United States Air Quality Field Study (KORUS-AQ) from May to June 2016. The highly sensitive GeoTASO instrument with a spatial resolution of ~250 m × 250 m can detect point emission sources of SO2 within its fields of view, even without merging multiple overlapping observations. To retrieve SO2 vertical columns from the GeoTASO measurements, we apply an algorithm based on principal component analysis (PCA), which is effective in suppressing noise and biases in SO2 retrievals. The retrievals successfully capture SO2 plumes and various point sources such as power plants, a petrochemical complex, and a steel mill, located in South Chungcheong Province, some of which are not detected by a ground-based in situ measurement network. Spatial distributions of SO2 from GeoTASO observations in source areas are consistent with those from the Stack Tele-Monitoring System reports and airborne in situ SO2 measurements. Comparisons of SO2 retrievals from GeoTASO and existing satellite sensors demonstrate the significance of high-resolution SO2 observations, by indicating that GeoTASO detects small SO2 emission sources that are not precisely resolved by single overpasses of satellites. To assess future geostationary SO2 observations having a higher spatial resolution, we upscale the GeoTASO SO2 retrievals to a spatial resolution of the Geostationary Environment Monitoring Spectrometer (GEMS). Since the upscaled GeoTASO retrievals also detect SO2 plumes clearly, we expect from GEMS to identify even small SO2 emission sources over Asia. •SO2 columns are retrieved from airborne remote sensing by an algorithm based on PCA.•Retrieved SO2 columns successfully detect SO2 sources in the Korean Peninsula.•Distributions of SO2 columns are consistent with those of known SO2 point sources.•Comparisons with spaceborne SO2 data highlight the significance of high-resolution.•Upscaled airborne SO2 retrievals allow assessing future geostationary observations.