Impacts of the COVID-19 economic slowdown on ozone pollution in the U.S

Patrick C Campbell; Daniel Tong; Youhua Tang; Barry Baker; Pius Lee; Rick Saylor; Ariel Stein; Siqi Ma; Lok Lamsal; Zhen Qu

doi:10.1016/j.atmosenv.2021.118713

Impacts of the COVID-19 economic slowdown on ozone pollution in the U.S

Atmos Environ (1994). 2021 Nov 1:264:118713. doi: 10.1016/j.atmosenv.2021.118713. Epub 2021 Sep 4.

Authors

Patrick C Campbell^{1

2}, Daniel Tong^{1

2

3}, Youhua Tang^{1

2

3}, Barry Baker^{1

2}, Pius Lee², Rick Saylor², Ariel Stein², Siqi Ma³, Lok Lamsal⁴, Zhen Qu⁵

Affiliations

¹ Center for Spatial Information Science and Systems, Cooperative Institute for Satellite Earth System Studies, George Mason University, Fairfax, VA, USA.
² Office of Oceanic and Atmospheric Research, Air Resources Laboratory, National Oceanic and Atmospheric Administration, College Park, MD, USA.
³ Department of Atmospheric, Oceanic and Earth Sciences, George Mason University, Fairfax, VA, USA.
⁴ Universities Space Research Association, NASA Goddard Space Flight Center, Greenbelt, MD, USA.
⁵ Harvard University, Department of Engineering and Applied Science, Cambridge, MA, USA.

Abstract

In this work, we use observations and experimental emissions in a version of NOAA's National Air Quality Forecasting Capability to show that the COVID-19 economic slowdown led to disproportionate impacts on near-surface ozone concentrations across the contiguous U.S. (CONUS). The data-fusion methodology used here includes both U.S. EPA Air Quality System ground and the NASA Aura satellite Ozone Monitoring Instrument (OMI) NO₂ observations to infer the representative emissions changes due to the COVID-19 economic slowdown in the U.S. Results show that there were widespread decreases in anthropogenic (e.g., NO_x) emissions in the U.S. during March-June 2020, which led to widespread decreases in ozone concentrations in the rural regions that are NO_x-limited, but also some localized increases near urban centers that are VOC-limited. Later in June-September, there were smaller decreases, and potentially some relative increases in NO_x emissions for many areas of the U.S. (e.g., south-southeast) that led to more extensive increases in ozone concentrations that are partly in agreement with observations. The widespread NO_x emissions changes also alters the O₃ photochemical formation regimes, most notably the NO_x emissions decreases in March-April, which can enhance (mitigate) the NO_x-limited (VOC-limited) regimes in different regions of CONUS. The average of all AirNow hourly O₃ changes for 2020-2019 range from about +1 to -4 ppb during March-September, and are associated with predominantly urban monitoring sites that demonstrate considerable spatiotemporal variability for the 2020 ozone changes compared to the previous five years individually (2015-2019). The simulated maximum values of the average O₃ changes for March-September range from about +8 to -4 ppb (or +40 to -10%). Results of this work have implications for the use of widespread controls of anthropogenic emissions, particularly those from mobile sources, used to curb ozone pollution under the current meteorological and climate conditions in the U.S.

Keywords: CMAQ Model; COVID-19 economic slowdown; National Air Quality Forecast Capability; Ozone pollution in the U.S..