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https://doi.org/10.5194/acp-2020-1023
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/acp-2020-1023
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  13 Oct 2020

13 Oct 2020

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This preprint is currently under review for the journal ACP.

COVID-19 lockdown induced changes in NO2 levels across India observed by multi-satellite and surface observations

Akash Biswal1,2, Vikas Singh1, Shweta Singh1, Amit P. Kesarkar1, Khaiwal Ravindra3, Ranjeet S. Sokhi4, Martyn P. Chipperfield5,6, Sandip S. Dhomse5,6, Richard J. Pope5,6, Tanbir Singh2, and Suman Mor2 Akash Biswal et al.
  • 1National Atmospheric Research Laboratory, Gadanki, AP, India
  • 2Department of Environment Studies, Panjab University, Chandigarh 160014, India
  • 3Department of Community Medicine and School of Public Health, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh 160012, India
  • 4Centre for Atmospheric and Climate Physics Research (CACP), University of Hertfordshire, Hatfield, UK
  • 5School of Earth and Environment, University of Leeds, Leeds, UK
  • 6National Centre for Earth Observation, University of Leeds, Leeds, UK

Abstract. We have estimated the spatial changes in NO2 levels over different regions of India during the COVID-19 lockdown (25th March–3rd May 2020) using the satellite-based tropospheric column NO2 observed by the Ozone Monitoring Instrument (OMI) and the Tropospheric Monitoring Instrument (TROPOMI), as well as surface NO2 concentrations obtained from the Central Pollution Control Board (CPCB) monitoring network. A substantial reduction in NO2 levels was observed across India during the lockdown compared to the same period during previous business-as-usual years, except for some regions that were influenced by anomalous fires in 2020. The reduction (negative change) over the urban agglomerations was substantial (∼ 20–40 %) and directly proportional to the urban size and population density. Rural regions across India also experienced lower NO2 values by ∼ 15–25 %. Localised enhancement of NO2 associated with isolated emission increase scattered across India, were also detected. Observed percentage changes in satellite and surface observations were consistent across most regions and cities, but the surface observations were subject to larger variability depending on their proximity to the local emission sources. Observations also indicate NO2 enhancements of up to ∼ 25 % during the lockdown associated with fire emissions over the north-east, and some parts of central regions. In addition, the cities located near the large fire emission sources show much smaller NO2 reduction than other urban areas as the decrease at the surface was masked by enhancement in NO2 due to the transport of the fire emissions.

Akash Biswal et al.

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Short summary
Satellite and surface observations show reduction in NO2 levels over India during the lockdown compared to business as usual years. A substantial reduction, proportional to the population, was observed over the urban areas. The changes in NO2 levels at the surface during the lockdown appear to be present in the satellite observations. However, TROPOMI showed a better correlation with surface NO2 and was more sensitive to the changes than the OMI because of the finer resolution.
Satellite and surface observations show reduction in NO2 levels over India during the lockdown...
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