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Improvement in air quality and its impact on land surface temperature in major urban areas across India during the first lockdown of the pandemic

Improvement in air quality and its impact on land surface temperature in major urban areas across India during the first lockdown of the pandemic
Improvement in air quality and its impact on land surface temperature in major urban areas across India during the first lockdown of the pandemic
The SARS CoV-2 (COVID-19) pandemic and the enforced lockdown have reduced the use of surface and air transportation. This study investigates the impact of the lockdown restrictions in India on atmospheric composition, using Sentinel–5Ps retrievals of tropospheric NO2 concentration and ground-station measurements of NO2 and PM2.5 between March–May in 2019 and 2020. Detailed analysis of the changes to atmospheric composition are carried out over six major urban areas (i.e. Delhi, Mumbai, Kolkata, Chennai, Bangalore, and Hyderabad) by comparing Moderate Resolution Imaging Spectroradiometer (MODIS) Aerosol Optical Depth (AOD) and land surface temperature (LST) measurements in the lockdown year 2020 and pre-lockdown (2015–2019). Satellite-based data showed that NO2 concentration reduced by 18% (Kolkata), 29% (Hyderabad), 32-34% (Chennai, Mumbai, and Bangalore), and 43% (Delhi). Surface-based concentrations of NO2, PM2.5, and AOD also substantially dropped by 32–74%, 10–42%, and 8–34%, respectively over these major cities during the lockdown period and co-located with the intensity of anthropogenic activity. Only a smaller fraction of the reduction of pollutants was associated with meteorological variability. A substantial negative anomaly was found for LST both in the day (–0.16 °C to –1 °C) and night (–0.63 °C to –2.1 °C) across select all cities, which was also consistent with air temperature measurements. The decreases in LST could be associated with a reduction in pollutants, greenhouse gases and water vapor content. Improvement in air quality with lower urban temperatures due to lockdown may be a temporary effect, but it provides a crucial connection among human activities, air pollution, aerosols, radiative flux, and temperature. The lockdown for a shorter-period showed a significant improvement in environmental quality and provides a strong evidence base for larger scale policy implementation to improve air quality.
AOD, Atmospheric pollutants, LST, Net radiative flux, Water vapor
0013-9351
111280
Parida, Bikash
3be9cfc2-17b7-4157-b2d3-139c177394cc
Bar, Somnath
9a818d88-927e-4bb4-91f6-dc5fe9159826
Roberts, Gareth
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Mandal, Shyama Prasad
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Pandey, Arvind
356b71cf-5bbb-43b6-8098-c1cdfad27d99
Kumar, Manoj
bf00b494-cad6-4ae9-8bc9-8a861ffeadb5
Dash, Jadunandan
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Parida, Bikash
3be9cfc2-17b7-4157-b2d3-139c177394cc
Bar, Somnath
9a818d88-927e-4bb4-91f6-dc5fe9159826
Roberts, Gareth
fa1fc728-44bf-4dc2-8a66-166034093ef2
Mandal, Shyama Prasad
19a0b498-d550-4f79-88fd-0b6d4efd7fa7
Pandey, Arvind
356b71cf-5bbb-43b6-8098-c1cdfad27d99
Kumar, Manoj
bf00b494-cad6-4ae9-8bc9-8a861ffeadb5
Dash, Jadunandan
51468afb-3d56-4d3a-aace-736b63e9fac8

Parida, Bikash, Bar, Somnath, Roberts, Gareth, Mandal, Shyama Prasad, Pandey, Arvind, Kumar, Manoj and Dash, Jadunandan (2021) Improvement in air quality and its impact on land surface temperature in major urban areas across India during the first lockdown of the pandemic. Environmental Research, 199, 111280, [111280]. (doi:10.1016/j.envres.2021.111280).

Record type: Article

Abstract

The SARS CoV-2 (COVID-19) pandemic and the enforced lockdown have reduced the use of surface and air transportation. This study investigates the impact of the lockdown restrictions in India on atmospheric composition, using Sentinel–5Ps retrievals of tropospheric NO2 concentration and ground-station measurements of NO2 and PM2.5 between March–May in 2019 and 2020. Detailed analysis of the changes to atmospheric composition are carried out over six major urban areas (i.e. Delhi, Mumbai, Kolkata, Chennai, Bangalore, and Hyderabad) by comparing Moderate Resolution Imaging Spectroradiometer (MODIS) Aerosol Optical Depth (AOD) and land surface temperature (LST) measurements in the lockdown year 2020 and pre-lockdown (2015–2019). Satellite-based data showed that NO2 concentration reduced by 18% (Kolkata), 29% (Hyderabad), 32-34% (Chennai, Mumbai, and Bangalore), and 43% (Delhi). Surface-based concentrations of NO2, PM2.5, and AOD also substantially dropped by 32–74%, 10–42%, and 8–34%, respectively over these major cities during the lockdown period and co-located with the intensity of anthropogenic activity. Only a smaller fraction of the reduction of pollutants was associated with meteorological variability. A substantial negative anomaly was found for LST both in the day (–0.16 °C to –1 °C) and night (–0.63 °C to –2.1 °C) across select all cities, which was also consistent with air temperature measurements. The decreases in LST could be associated with a reduction in pollutants, greenhouse gases and water vapor content. Improvement in air quality with lower urban temperatures due to lockdown may be a temporary effect, but it provides a crucial connection among human activities, air pollution, aerosols, radiative flux, and temperature. The lockdown for a shorter-period showed a significant improvement in environmental quality and provides a strong evidence base for larger scale policy implementation to improve air quality.

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ER-20-5325-Accepted - Accepted Manuscript
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More information

Accepted/In Press date: 30 April 2021
e-pub ahead of print date: 21 May 2021
Published date: August 2021
Additional Information: Funding Information: Authors thanks to European Union, Copernicus Services for providing access to satellite-based NO2 data (Sentinel?5P TROPOMI), NASA LPDAAC for provision of the MODIS LST and AOD data, and Google Earth Engine (GEE) for providing the analyzing platform. The authors also thank various organizations for providing access to ground observation data on NO2 and PM2.5. B.R Parida received funding from University Grants Commission under the start-up Grant (F.4?5(209-FRP)/2015/BSR). Funding Information: Authors thanks to European Union, Copernicus Services for providing access to satellite-based NO 2 data (Sentinel–5P TROPOMI), NASA LPDAAC for provision of the MODIS LST and AOD data, and Google Earth Engine (GEE) for providing the analyzing platform. The authors also thank various organizations for providing access to ground observation data on NO 2 and PM 2.5 . B.R Parida received funding from University Grants Commission under the start-up Grant ( F.4–5(209-FRP)/2015/BSR ). Publisher Copyright: © 2021 Elsevier Inc.
Keywords: AOD, Atmospheric pollutants, LST, Net radiative flux, Water vapor

Identifiers

Local EPrints ID: 448792
URI: http://eprints.soton.ac.uk/id/eprint/448792
ISSN: 0013-9351
PURE UUID: 7dc8d8fa-6c34-4e21-bc73-f7955673c77f
ORCID for Gareth Roberts: ORCID iD orcid.org/0009-0007-3431-041X
ORCID for Jadunandan Dash: ORCID iD orcid.org/0000-0002-5444-2109

Catalogue record

Date deposited: 05 May 2021 16:56
Last modified: 19 Dec 2023 05:21

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Contributors

Author: Bikash Parida
Author: Somnath Bar
Author: Gareth Roberts ORCID iD
Author: Shyama Prasad Mandal
Author: Arvind Pandey
Author: Manoj Kumar
Author: Jadunandan Dash ORCID iD

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