Preprints
https://doi.org/10.5194/acp-2021-413
https://doi.org/10.5194/acp-2021-413

  27 Jul 2021

27 Jul 2021

Review status: a revised version of this preprint is currently under review for the journal ACP.

Interpretation of geostationary satellite aerosol optical depth (AOD) over East Asia in relation to fine particulate matter (PM2.5): insights from the KORUS-AQ aircraft campaign and seasonality

Shixian Zhai1, Daniel J. Jacob1, Jared F. Brewer1, Ke Li1, Jonathan M. Moch1, Jhoon Kim2,3, Seoyoung Lee2, Hyunkwang Lim2, Hyun Chul Lee3, Su Keun Kuk3, Rokjin J. Park4, Jaein I. Jeong4, Xuan Wang5, Pengfei Liu6, Gan Luo7, Fangqun Yu7, Jun Meng8,a, Randall V. Martin8, Katherine R. Travis9, Johnathan W. Hair9, Bruce E. Anderson9, Jack E. Dibb10, Jose L. Jimenez11, Pedro Campuzano-Jost11, Benjamin A. Nault11,b, Jung-Hun Woo12, Younha Kim13, Qiang Zhang14, and Hong Liao15 Shixian Zhai et al.
  • 1Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
  • 2Department of Atmospheric Sciences, Yonsei University, Seoul, Republic of Korea
  • 3Samsung Particulate Matter Research Institute, Samsung Advanced Institute of Technology, 130 Samsung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do, Republic of Korea
  • 4School of Earth and Environmental Sciences, Seoul National University, Seoul, Republic of Korea
  • 5School of Energy and Environment, City University of Hong Kong, Hong Kong SAR, China
  • 6School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
  • 7Atmospheric Sciences Research Center, University at Albany, Albany, New York, USA
  • 8Department of Energy, Environmental & Chemical Engineering, Washington University in St Louis, MO, USA
  • 9NASA Langley Research Center, Hampton, VA, USA
  • 10Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH, USA
  • 11Department of Chemistry, and Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA
  • 12Department of Civil and Environmental Engineering, Konkuk University, Seoul, Republic of Korea
  • 13International Institute for Applied Systems Analysis (IIASA), 2361 Laxenburg, Austria
  • 14Department of Earth System Science, Tsinghua University, Beijing, China
  • 15Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, School of Environmental Science and Engineering, Nanjing University of Information Science and Technology, Nanjing, China
  • anow at: Department of Atmospheric & Oceanic Sciences, University of California, Los Angeles, California, USA
  • bnow at: Center for Aerosol and Cloud Chemistry, Aerodyne Research, Inc., Billerica, MA, USA

Abstract. Geostationary satellite sensors over East Asia (GOCI and AHI) are now providing continuous mapping of aerosol optical depth (AOD) at 550 nm to improve monitoring of fine particulate matter (PM2.5) air quality. Here we evaluate our understanding of the physical relationships between AOD and PM2.5 over East Asia by using the GEOS-Chem atmospheric chemistry model to simulate observations from multiple sources: 1) the joint NASA-NIER Korea – United States Air Quality aircraft campaign over South Korea (KORUS-AQ; May–June 2016); 2) AODs from the AERONET ground-based network; 3) AOD from a new GOCI/AHI fused product; and 4) surface PM2.5 networks in South Korea and China. The KORUS-AQ data show that 550 nm AOD is mainly contributed by sulfate-nitrate-ammonium (SNA) and organic aerosols in the planetary boundary layer (PBL), despite large dust concentrations in the free troposphere, reflecting the optically effective size and the high hygroscopicity of the PBL aerosols. Although GEOS-Chem is successful in reproducing the KORUS-AQ vertical profiles of aerosol mass, its ability to link AOD to PM2.5 is limited by under-accounting of coarse PM and by a large overestimate of nighttime PM2.5 nitrate. A broader analysis of the GOCI/AHI AOD data over East Asia in different seasons shows agreement with AERONET AODs and a spatial distribution consistent with surface PM2.5 network data. The AOD observations over North China show a summer maximum and winter minimum, opposite in phase to surface PM2.5. This is due to low PBL depths compounded by high residential coal emissions in winter, and high relative humidity (RH) in summer. Seasonality of AOD and PM2.5 over South Korea is much weaker, reflecting weaker variation of PBL depth and lack of residential coal emissions. Physical interpretation of the satellite AOD data in terms of surface PM2.5 is sensitive to accurate information on aerosol size distributions, PBL depths, RH, the role of coarse particles, and diurnal variation of PM2.5.

Shixian Zhai et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-413', Anonymous Referee #3, 19 Aug 2021
  • RC2: 'Comment on acp-2021-413', Anonymous Referee #2, 22 Aug 2021
  • RC3: 'Comment on acp-2021-413', Anonymous Referee #1, 02 Sep 2021
  • AC1: 'Comment on acp-2021-413', Shixian Zhai, 19 Sep 2021

Shixian Zhai et al.

Shixian Zhai et al.

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Short summary
Geostationary satellite aerosol optical depth (AOD) has tremendous potential for monitoring surface fine particulate matter (PM2.5). We integrated data from surface networks, aircraft, and satellites with the GEOS-Chem atmospheric chemistry model to enhance our ability to relate AOD to PM2.5. We attributed 550 nm AOD mainly to secondary aerosols in the planetary boundary layer (PBL) and explained the opposite seasonality between AOD and PM2.5 by seasonality in PBL heights and relative humidity.
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