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Volume 18, issue 20 | Copyright

Special issue: Regional transport and transformation of air pollution in...

Atmos. Chem. Phys., 18, 15387-15402, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 26 Oct 2018

Research article | 26 Oct 2018

Tropospheric NO2, SO2, and HCHO over the East China Sea, using ship-based MAX-DOAS observations and comparison with OMI and OMPS satellite data

Wei Tan1, Cheng Liu1,2,3,6, Shanshan Wang4,5, Chengzhi Xing2, Wenjing Su2, Chengxin Zhang2, Congzi Xia2, Haoran Liu2, Zhaonan Cai7, and Jianguo Liu1 Wei Tan et al.
  • 1Key Lab of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, 230031, China
  • 2School of Earth and Space Sciences, University of Science and Technology of China, Hefei, 230026, China
  • 3Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China
  • 4Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP), Department of Environmental Science and Engineering, Fudan University, Shanghai, 200433, China
  • 5Shanghai Institute of Eco-Chongming (SIEC), No. 3663 Northern Zhongshan Road, Shanghai, 200062, China
  • 6Anhui Province Key Laboratory of Polar Environment and Global Change, USTC, Hefei, 230026, China
  • 7Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences, Beijing, 100029, China

Abstract. In this study, ship-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements were performed in the East China Sea (ECS) area in June 2017. The tropospheric slant column densities (SCDs) of nitrogen dioxide (NO2), sulfur dioxide (SO2), and formaldehyde (HCHO) were retrieved from the measured spectra using the differential optical absorption spectroscopy (DOAS) technique. Using the simple geometric approach, the SCDs of different trace gases observed at a 15° elevation angle were adopted to convert into tropospheric vertical column densities (VCDs). During this campaign, the averaged VCDs of NO2, SO2, and HCHO in the marine environment over the ECS area are 6.50×1015, 4.28×1015, and 7.39×1015moleccm−2, respectively. In addition, the ship-based MAX-DOAS trace gas VCDs were compared with satellite observations of the Ozone Monitoring Instrument (OMI) and Ozone Mapping and Profiler Suite (OMPS). The daily OMI NO2 VCDs agreed well with ship-based MAX-DOAS measurements showing the correlation coefficient R of 0.83. In addition, the good agreements of SO2 and HCHO VCDs between the OMPS satellite and ship-based MAX-DOAS observations were also found, with correlation coefficients R of 0.76 and 0.69. The vertical profiles of these trace gases are achieved from the measured differential slant column densities (DSCDs) at different elevation angles using the optimal estimation method. The retrieved profiles displayed the typical vertical distribution characteristics, which exhibit low concentrations of  < 3,  < 3, and  < 2ppbv for NO2, SO2, and HCHO in a clean area of the marine boundary layer far from coast of the Yangtze River Delta (YRD) continental region. Interestingly, elevated SO2 concentrations can be observed intermittently along the ship routes, which is mainly attributed to the vicinal ship emissions in the view of the MAX-DOAS measurements. Combined with the on-board ozone lidar measurements, the ozone (O3) formation was discussed with the vertical profile of the HCHO∕NO2 ratio, which is sensitive to increases in NO2 concentration. This study provided further understanding of the main air pollutants in the marine boundary layer of the ECS area and also benefited the formulation of policies regulating the shipping emissions in such costal areas like the YRD region.

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Short summary
This ship-based observation in June 2017 has, for the first time, reported the vertical column densities of NO2, SO2, and HCHO over oceanic areas of the East China Sea, which show good agreement with satellite observations. High levels of trace gases over oceanic areas were identified to be related to the regional transport of air pollutants from continental areas and nearby ship emissions.
This ship-based observation in June 2017 has, for the first time, reported the vertical column...