Figure 3.

Mean bimonthly changes in NO₂ concentrations at AQS sites from 2019 to 2020. Changes in AQS surface air NO₂ concentrations are compared to changes in TROPOMI tropospheric NO₂ columns sampled at the same sites. Results for the AQS sites with the 5% highest 2019 NO₂ concentrations on a 0.5° × 0.625° grid (Figure 1) are shown in the left panel. The effects of meteorological changes have been subtracted with a GEOS‐Chem simulation. The error bars represent the normalized standard errors of the changes averaged over the sites. AQS, Air Quality System; TROPOMI, Tropospheric Ozone Monitoring Instrument.