资源环境科技发展态势分析平台

Satellite NO₂ measurements are used extensively to infer nitrogen oxide (NO_x) 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 (OMI, 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.