Preprints
https://doi.org/10.5194/acp-2021-536
https://doi.org/10.5194/acp-2021-536

  06 Jul 2021

06 Jul 2021

Review status: this preprint is currently under review for the journal ACP.

Quantifying urban, industrial, and background changes in NO2 during the COVID-19 lockdown period based on TROPOMI satellite observations

Vitali Fioletov1, Chris A. McLinden1, Debora Griffin1, Nickolay Krotkov2, Fei Liu2, and Henk Eskes3 Vitali Fioletov et al.
  • 1Air Quality Research Division, Environment and Climate Change Canada, Toronto, Canada
  • 2Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
  • 3Environmental Sciences Group, Wageningen University, Wageningen, the Netherlands

Abstract. The COVID-19 lockdown had a large impact on anthropogenic emissions of air pollutants and particularly on nitrogen dioxide (NO2). While the overall NO2 decline over some large cities is well-established, its quantification remains a challenge because of a variety of sources of NO2. In this study, a new method of isolation of three components: background NO2, NO2 from urban sources, and from industrial point sources is applied to estimate the COVID-19 lockdown impact on each of them. The approach is based on fitting satellite data by a statistical model with empirical plume dispersion functions driven by the observed winds. Population density and surface elevation data as well as coordinates of industrial sources were used in the analysis. The NO2 vertical column density (VCD) values measured by Tropospheric Monitoring Instrument (TROPOMI) on board Sentinel‐5 Precursor over 263 urban areas for the period from March 16 to June 15, 2020, were compared with the average VCD values for the same period in 2018 and 2019. While background NO2 component remained almost unchanged, the urban NO2 component declined by 18–28 % over most regions. India, South America, and a part of Europe (particularly, Italy, France, and Spain) demonstrated a 40–50 % urban emissions decline. In contrast, decline over urban area in China, where the lockdown was over during the analyzed period, was only 3 % except for Wuhan, where more than 60 % decline was observed. Emissions from large industrial sources in the analyzed urban areas varies largely from region to region from +5 % for China to −40 % for India. Changes in urban emissions are correlated with changes in Google mobility data (the correlation coefficient is 0.66) confirming that changes in traffic was one of the key elements in decline of urban NO2 emissions. No correlation was found between changes in background NO2 and Google mobility data.

Vitali Fioletov et al.

Status: open (until 17 Aug 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Vitali Fioletov et al.

Vitali Fioletov et al.

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Short summary
The COVID-19 lockdown had a large impact on anthropogenic emissions and particularly on nitrogen dioxide (NO2). A new method of isolation of background, urban, and industrial components in NO2 is applied to estimate the lockdown impact on each of them. During March 16–June 15, 2020, the urban NO2 declined by 18–28 % in most regions, while background NO2 remained almost unchanged. Emissions from large industrial sources varies largely from region to region from +5 % for China to −40 % for India.
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