Preventative measures recently adopted to prevent further spread of COVID-19 in the United States of America have prompted an overall slowdown in economic activity and fewer vehicles on the roadways. Since combustion engine powered vehicles can represent a major source of nitrogen dioxide (NO2) emissions, less traffic on the roadways may lead to a significant reduction in NO2 concentrations and, as a result, fine particulate matter (particulate matter less than 2.5 microns in diameter or PM2.5) as NO2 emissions are a known precursor to PM formation. Overall, these observed reductions in TROPOMI NO2 throughout March are the result of decreased emissions on top of the seasonal changes in meteorological conditions.
