A098-03
Global Impact of COVID-19 Restrictions on the Atmospheric Concentrations of Nitrogen Dioxide and Ozone

Thursday, 10 December 2020: 07:08
Virtual
Mathew J Evans1,2, Christoph Keller3,4, K. Emma Knowland3,4, Christa A Hasenkopf5, Sruti Modekurty6, Robert A Luccesi7,8, Tomohiro Oda3,9, Bruno França10, Felipe Mandarino11, M. Valeria Díaz Suárez12, Robert G Ryan13, Luke Fakes1,14 and Steven Pawson3, (1)University of York, Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, York, YO10, United Kingdom, (2)National Centre for Atmospheric Science, Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry,, York, United Kingdom, (3)NASA Goddard Space Flight Center, Global Modeling and Assimilation Office, Greenbelt, MD, United States, (4)Universities Space Research Association Columbia, Columbia, MD, United States, (5)OpenAQ, Washington, DC, United States, (6)openAQ, Washington, DC, United States, (7)NASA Goddard Space Flight Center, Global Modeling and Assimilation Office, Greenbelt, United States, (8)Science Systems and Applications, Inc., Lanham, United States, (9)Universities Space Research Association Greenbelt, Greenbelt, MD, United States, (10)Secretaria Municipal de Meio Ambiente, Rio de Janeiro, Brazil, (11)City of Rio de Janeiro, Rio deJaneiro, Brazil, (12)Secretaria de Ambiente, Quito, Ecuador, (13)University of Melbourne, School of Earth Sciences, Parkville, Australia, (14)National Centre for Atmospheric Science, Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, York, United Kingdom
Recorded Presentation
Abstract:
Restrictions imposed to reduce the transmission of COVID-19 led to a significant reduction in the emission of air pollutants around the world. Quantifying these changes requires a business as usual counterfactual that accounts for the synoptic and seasonal variability of air pollutants. We develop a counterfactual prediction for the concentration of surface nitrogen dioxide (NO2) and ozone (O3) at 5,756 observation sites in 46 countries from January through June 2020 using a machine learning algorithm and information from the NASA GEOS-CF model. Reductions in NO2 correlate with timing and intensity of COVID-19 restrictions. In severely impacted (e.g., Wuhan, Milan) these reductions can be up to 60%. However, in other cities we do not observe much change (e.g., Rio de Janeiro, Taipei). On average, NO2 concentrations were 18% lower than expected had the restrictions not be implements. China experienced the earliest and steepest decline, but since April concentrations have mostly recovered. In Europe and North America NO2 reductions were smaller with some recovery starting in April. We estimate that the globally NOx (NO+NO2) emission reduced during the first 6 months of 2020 by 2.9 TgN, equivalent to 5.1% of the annual anthropogenic total. Surface O3 shows a more complicated response due to its complex atmospheric chemistry. In some locations O3 increased by up to 50%, but on average we find small changes to daily O3 between February - June 2020. We do find a flattening of the O3 diurnal cycle with an increase in nighttime ozone due to reduced titration and a decrease in daytime ozone, reflecting a reduction in photochemical production.
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