Images taken over the first three weeks of March show less nitrogen dioxide over parts of the United States than the same time last year. Nitrogen dioxide in the air comes primarily from the burning of fuel and forms from the emissions of cars, trucks, buses, power plants and off-road equipment, according to the US Environmental Protection Agency.
The pollutant is noticeably lower in concentration in much of California, where places including the Bay Area and Central Valley have implemented stricter social distancing guidelines. Another area hit hard by the virus, western Washington state around Seattle, also shows much lower concentration of the gas the past several weeks.
The images were created by CNN using Sentinel-5P satellite data processed by Descartes Labs.
“This is the first time I have seen such a dramatic drop-off over such a wide area for a specific event,” says Fei Liu, an air quality researcher at NASA’s Goddard Space Flight Center. “I am not surprised because many cities nationwide have taken measures to minimize the spread of the virus.”