Preprints
https://doi.org/10.5194/acp-2021-592
https://doi.org/10.5194/acp-2021-592

  16 Aug 2021

16 Aug 2021

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

Declines and peaks in NO2 pollution during the multiple waves of the COVID-19 pandemic in the New York metropolitan area

Maria Tzortziou1,2, Charlotte Frances Kwong1, Daniel Goldberg3, Luke Schiferl4, Róisín Commane4,5, Nader Abuhassan2,6, James Szykman7,8, and Lukas Valin8 Maria Tzortziou et al.
  • 1Center for Discovery and Innovation, Earth & Atmospheric Sciences, City College of New York, New York, NY 10031, USA
  • 2NASA Goddard Space Flight Center, Greenbelt, MD, 20771, USA
  • 3Department of Environmental and Occupational Health, George Washington University, Washington, DC, 20052, USA
  • 4Lamont Doherty Earth Observatory, Columbia University, Palisades, NY, 10964, USA
  • 5Department of Earth and Environmental Sciences, Columbia University, New York, NY, 10027, USA
  • 6Joint Center for Earth Systems Technology, University of Maryland, Baltimore, MD, 21201, USA
  • 7NASA Langley Research Center, Hampton, VA, 23666, USA
  • 8US EPA/Office of Research and Development/Center for Environmental Measurement and Modeling, Research Triangle Park, NC, USA

Abstract. The COVID-19 pandemic created an extreme natural experiment in which sudden changes in human behavior and economic activity resulted in significant declines in nitrogen oxide (NOx) emissions, immediately after strict lockdowns were imposed. Here we examined the impact of multiple waves and response phases of the pandemic on nitrogen dioxide (NO2) dynamics and the role of meteorology in shaping relative contributions from different emission sectors to NO2 pollution in post-pandemic New York City. Long term (> 3.5 years), high frequency measurements from a network of ground-based Pandora spectrometers were combined with TROPOMI satellite retrievals, meteorological data, mobility trends, and atmospheric transport model simulations to quantify changes in NO2 across the New York metropolitan area. The stringent lockdown measures after the first pandemic wave resulted in a decline in top-down NOx emissions by approx. 30 % on top of long-term trends, in agreement with sector-specific changes in NOx emissions. Ground-based measurements showed a sudden drop in total column NO2 in spring 2020, by up to 36 % in Manhattan and 19–29 % in Queens, New Jersey and Connecticut, and a clear weakening (by 16 %) of the typical weekly NO2 cycle. Extending our analysis to more than a year after the initial lockdown captured a gradual recovery in NO2 across the NY/NJ/CT tri-state area in summer and fall 2020, as social restrictions eased, followed by a second decline in NO2 coincident with the second wave of the pandemic and resurgence of lockdown measures in winter 2021. Meteorology was not found to have a strong NO2 biasing effect in New York City after the first pandemic wave. Winds, however, were favorable for low NO2 conditions in Manhattan during the second wave of the pandemic, resulting in larger column NO2 declines than expected based on changes in transportation emissions alone. Meteorology played a key role in shaping the relative contributions from different emission sectors to NO2 pollution in the city, with low-speed (< 5 ms−1) SW-SE winds enhancing contributions from the high-emitting power-generation sector in NJ and Queens and driving particularly high NO2 pollution episodes in Manhattan, even during – and despite – the stringent early lockdowns. These results have important implications for air quality management in New York City, and highlight the value of high resolution NO2 measurements in assessing the effects of rapid meteorological changes on air quality conditions and the effectiveness of sector-specific NOx emission control strategies.

Maria Tzortziou et al.

Status: open (until 27 Sep 2021)

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

Maria Tzortziou et al.

Maria Tzortziou et al.

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Short summary
The COVID-19 pandemic created an extreme natural experiment in which sudden changes in human behavior significantly impacted urban air quality. Using a combination of model, satellite, and ground-based data, we examine the impact of multiple waves and phases of the pandemic on atmospheric nitrogen pollution in the New York metropolitan area, and address the role of weather as a key driver of high pollution episodes observed even during – and despite – the stringent early lockdowns.
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