Disentangling the impact of the COVID-19 lockdowns on urban NO2 from
Satellite data show substantial drops in nitrogen dioxide (NO2) during
COVID-19 physical distancing. To attribute NO2 changes to NOx emissions
changes over short timescales, one must account for meteorological
effects. We find that meteorological patterns were especially favorable
for low NO2 in much of the U.S. in spring 2020, complicating comparisons
with spring 2019. Meteorological variations between years can cause
column NO2 differences of ~15% over monthly timescales.
After accounting for sun angle and meteorological considerations, we
calculate that NO2 drops ranged between 9.2 – 43.4% among twenty
cities in North America, with a median of 21.6%. Of the studied cities,
largest NO2 drops (>30%) were in San Jose, Los Angeles,
and Toronto, and smallest drops (<12%) were in Miami,
Minneapolis, and Dallas. These normalized NO2 changes can be used to
highlight locations with greater activity changes and better understand
the sources contributing to adverse air quality in each city.