Yongjoo Choi This email address is being protected from spambots. You need JavaScript enabled to view it.1, Yugo Kanaya1, Hisahiro Takashima1,2, Kihong Park3, Haebum Lee3, Jihyo Chong3,4, Jae Hwan Kim5, Jin-Soo Park6 

1 Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, Yokohama 2360001, Japan
2 Faculty of Science, Fukuoka University, Fukuoka 8140133, Japan
3 School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology, Gwangju 61005, Korea
4 Environmental Management Division, Yeongsan River Basin Environmental Office, Gwangju 61945, Korea
5 Pusan National University, Busan 46241, Korea
6 National Institute of Environmental Research, Incheon 22689, Korea

Received: April 10, 2022
Revised: October 25, 2022
Accepted: March 6, 2023

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.

Download Citation: ||https://doi.org/10.4209/aaqr.220145  

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Cite this article:

Choi, Y., Kanaya, Y., Takashima, H., Park, K., Lee, H., Chong, J., Kim, J.H., Park, J.S. (2023). Changes in Tropospheric Nitrogen Dioxide Vertical Column Densities over Japan and Korea during the COVID-19 Using Pandora and MAX-DOAS. Aerosol Air Qual. Res. https://doi.org/10.4209/aaqr.220145


  • Investigation of the impact of COVID-19 on NO2 TropVCD from ground-based networks.
  • The differences in correlations between NO2 and Google mobility in Korea and Japan.
  • More rapid decreasing trend in NO2 in 2020 by excluding influenced variables.


We investigated the impact of human activity during COVID-19 on the tropospheric nitrogen dioxide vertical column density (NO2 TropVCD) at three urban sites (Gwangju and Busan in Korea and Yokosuka in Japan) and one remote site (Cape Hedo in Japan) from Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) and Pandora. Compared to the monthly mean NO2 TropVCD from 2015 to 2018 and in 2019, the values were lower in 2020 due to social distancing in Korea and Japan. High negative relative changes were observed from May to September (−30% to −18%) at the three urban sites; Cape Hedo, a remote site, did not show a significant difference in relative changes between previous years and 2020, suggesting that only anthropogenic emission sources decreased dramatically. In the case of Yokosuka, the 15-day moving average of the NO2 TropVCD exhibited a good relationship with transportation (R = 0.48) and industry (R = 0.54) mobility data. In contrast, the NO2 TropVCD at the Korean sites showed a moderate to low correlation with the industrial sector and insignificant correlations with transportation. The differences in correlations might be caused by the different social distancing policies in Korea (voluntary) and Japan (mandatory). By applying generalized boosted models to exclude meteorological and seasonal effects associated with NO2 TropVCD variations, we revealed that the decreasing trend from 2019 to 2020 was much steeper than that from 2015 to 2020 (a factor of two), and a significant change was identified in January 2020, when the first cases of COVID-19 were observed in both Korea and Japan. This result confirmed that the reduction in NO2 can be largely explained by the NOx emission reduction resulting from social distancing for COVID-19 rather than annual meteorological differences; however, in December 2020, NO2 recovered suddenly to its previous level due to an increase in human activities.

Keywords: COVID-19, Nitrogen dioxide, MAX-DOAS, Pandora

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