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US COVID-19 Shutdown Demonstrates Importance of Background NO₂ in Inferring NO_x Emissions From Satellite NO₂ Observations.

ABSTRACT: Satellite nitrogen dioxide (NO₂) measurements are used extensively to infer nitrogen oxide emissions and their trends, but interpretation can be complicated by background contributions to the NO₂ column sensed from space. We use the step decrease of US anthropogenic emissions from the COVID-19 shutdown to compare the responses of NO₂ concentrations observed at surface network sites and from satellites (Ozone Monitoring Instrument [OMI], Tropospheric Ozone Monitoring Instrument [TROPOMI]). After correcting for differences in meteorology, surface NO₂ measurements for 2020 show decreases of 20% in March-April and 10% in May-August compared to 2019. The satellites show much weaker responses in March-June and no decrease in July-August, consistent with a large background contribution to the NO₂ column. Inspection of the long-term OMI trend over remote US regions shows a rising summertime NO₂ background from 2010 to 2019 potentially attributable to wildfires.

SUBMITTER: Qu Z

PROVIDER: S-EPMC8206743 | biostudies-literature |

REPOSITORIES: biostudies-literature

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