Guanyu Huang This email address is being protected from spambots. You need JavaScript enabled to view it.1, Reyla Ponder2,3, Amber Bond1, Hailey Brim1, Akua Temeng4, Aaron R. Naeger5, Lei Zhu6

1 Environmental and Health Sciences Program, Spelman College, Atlanta, GA 30314, USA
2 Department of Mathematics, Spelman College, Atlanta, GA 30314, USA
3 College of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
4 Department of Chemistry and Biochemistry, Spelman College, Atlanta, GA 30314, USA
5 Earth System Science Center, University of Alabama in Huntsville, Huntsville, AL 35805, USA
6 School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China

Received: June 26, 2021
Revised: August 31, 2021
Accepted: September 9, 2021

 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.

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Huang, G., Ponder, R., Bond, A., Brim, H., Temeng, A., Naeger, A.R., Zhu, L. (2021). Unexpected Impact of COVID-19 Lockdown on the Air Quality in the Metro Atlanta, USA Using Ground-based and Satellite Observations. Aerosol Air Qual. Res.


  • Air quality in Atlanta has improved slightly during the COVID-19 lockdown period.
  • This slight improvement is caused by reduced human activities and meteorology.
  • Ground measurements disagree with space-borne measurements on NO2


We studied the impact of COVID-19 (coronavirus disease 2019) lockdown on the air quality over the Atlanta area using satellite and ground-based observations, meteorological reanalysis data and traffic information. Unlike other cities, we found the air quality has improved slightly over the Atlanta area during the 2020 COVID-19 lockdown period (March 14–April 30, 2020), compared to the analogous period of 2019 (March 14-April 30, 2019). Ground NO2 concentrations have decreased slightly 10.8% and 8.2% over the near-road (NR) and urban ambient (UA) stations, respectively. Tropospheric NO2 columns have reduced 13%-49% over the Atlanta area from space-borne observations of TROPOspheric Monitoring Instrument (TROPOMI). Ground ozone and PM2.5 have decreased 15.7% an ~5%, respectively. This slight air quality improvement is primarily caused by the reduced human activities, as COVID-19 lockdowns have reduced ~50% human activities, measured by traffic volume. Higher wind speed and precipitations also make the meteorological conditions favorable to this slight air quality improvement. We have not found a significant improvement in Atlanta amid the lockdown when human activities have reduced ~50%. Further studies are needed to understand the impacts of reduced human activities on atmospheric chemistry.  We also found TROPOMI and ground measurements have disagreements on NO2 reductions, as collocated TROPOMI observations revealed ~23% and ~21% reductions of tropospheric NO2 columns over NR and UA stations, respectively. Several factors may explain this disagreement: First, tropospheric NO2 columns and ground NO2 concentrations are not necessarily the same, although they are highly correlated in the afternoon; Second, meteorological conditions may have different impacts on TROPMI and ground measurements. Third, TROPOMI may underestimate tropospheric NO2 due to uncertainties from air mass factors. Fourth, the uncertainties of chemiluminescence NO2 measurements used by ground stations.  Consequently, studies using space-borne tropospheric NO2 column and ground NO2 measurements should take these factors into account.

Keywords: COVID-19, Air Quality, TROPOMI, NO2

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