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

Heesung Chong, Seoyoung Lee, Jhoon Kim, Ukkyo Jeong, Can Li, Nickolay A. Krotkov, Caroline R. Nowlan, Jassim A. Al-Saadi, Scott J. Janz, Matthew G. Kowalewski, Myoung Hwan Ahn, Mina Kang, Joanna Joiner, David P. Haffner, Lu Hu, Patricia Castellanos, L. Gregory Huey, Myungje Choi, Chul H. Song, Kyung Man HanJa Ho Koo

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10 Scopus citations

Abstract

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.

Original languageEnglish
Article number111725
JournalRemote Sensing of Environment
Volume241
DOIs
StatePublished - May 2020

Bibliographical note

Funding Information:
This subject was supported by Korea Ministry of Environment (MOE) as the Public Technology Program based on Environmental Policy ( 2017000160001 ). We thank all members of the KORUS-AQ science team for their contributions to the field study and the data processing (doi:10.5067/Suborbital/KORUSAQ/DATA01). We thank NIER, all principal investigators, and their staff of AirKorea for establishing and maintaining the AirKorea stations used in this investigation. We would like to acknowledge all staff involved in the Stack TMS reports for operating the whole system and the free use of the data. We also thank the principal investigators of the Anmyon AERONET site, Je Gyu Ryu and Sang-Ok Han, and all staff for establishing and maintaining the monitoring site during the KORUS-AQ period. We acknowledge the free use of the OMSO2, OMSO2e, OMPS_NPP_NMSO2_PCA_L2, OMLER, and ERA5 datasets. A URL address where each of the data is available is stated in references below.

Funding Information:
This subject was supported by Korea Ministry of Environment (MOE) as the Public Technology Program based on Environmental Policy (2017000160001). We thank all members of the KORUS-AQ science team for their contributions to the field study and the data processing (doi:10.5067/Suborbital/KORUSAQ/DATA01). We thank NIER, all principal investigators, and their staff of AirKorea for establishing and maintaining the AirKorea stations used in this investigation. We would like to acknowledge all staff involved in the Stack TMS reports for operating the whole system and the free use of the data. We also thank the principal investigators of the Anmyon AERONET site, Je Gyu Ryu and Sang-Ok Han, and all staff for establishing and maintaining the monitoring site during the KORUS-AQ period. We acknowledge the free use of the OMSO2, OMSO2e, OMPS_NPP_NMSO2_PCA_L2, OMLER, and ERA5 datasets. A URL address where each of the data is available is stated in references below.

Publisher Copyright:
© 2020

Keywords

  • Airborne remote sensing
  • GEMS
  • GeoTASO
  • KORUS-AQ
  • PCA technique
  • SO

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