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Tropospheric NO_2 and O_3 response to COVID-19 lockdown restrictions at the national and urban scales in Germany
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  • Vigneshkumar Balamurugan,
  • Jia Chen,
  • Xiao Bi,
  • Zhen Qu,
  • Johannes Gensheimer,
  • Ankit Shekhar,
  • Shrutilipi Bhattacharjee,
  • Frank Keutsch
Vigneshkumar Balamurugan
Technical University of Munich

Corresponding Author:[email protected]

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Jia Chen
Technical University of Munich
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Xiao Bi
Technical University of Munich
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Zhen Qu
Harvard University
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Johannes Gensheimer
Technical University of Munich
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Ankit Shekhar
ETH Zurich
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Shrutilipi Bhattacharjee
National Institute of Technology Karnataka
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Frank Keutsch
Harvard University
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Abstract

This study estimates the influence of anthropogenic emission reductions on nitrogen dioxide (NO_2) and ozone (O_3) concentration changes during the COVID-19 pandemic period using in-situ surface and Sentinel-5p (TROPOMI) satellite column measurements and GEOS-Chem model simulations. We show that, as a result of reductions in anthropogenic emission in eight German metropolitan cities, meteorology corrected mean in-situ (\& column) NO_2(2020,corr) concentrations decreased by 23 ± 4.7 % (& 16.4 ± 7.2 %) between March 21 and June 30, 2020, whereas meteorology corrected mean in-situ O_3(2020,corr) concentration increased by 4 ± 8.8 % between March 21 and May 31, 2020, and decreased by 3 ± 8.7 % in June 2020, compared to 2019 (uncertainty represents the 1 σ of mean changes of eight metropolitan cities). The impacts of meteorology on in-situ and TROPOMI NO_2 concentration changes during the lockdown compared to 2019 are relatively small (+0.4 % and -0.6 %, respectively), while those on in-situ O_3 concentration changes are more significant (+3.6 % and -13.5 % for March 21 to May 31, 2020 and June 2020, respectively). A NO_X saturated ozone production regime in German metropolitan cities in March to May explains the increased O_3(2020,corr) concentration in response to the decreased NO_2(2020,corr) concentration. This implies that future reductions in NO_X emissions are likely to increase ozone pollution in these cities if appropriate mitigation measures are not implemented. TROPOMI NO_2(2020,corr) concentrations decreased nationwide during the stricter lockdown period, except for North-West Germany, which can be attributed to enhanced NO_X emissions from agricultural soils.
16 Oct 2021Published in Journal of Geophysical Research: Atmospheres volume 126 issue 19. 10.1029/2021JD035440