When the coronavirus first appeared, in December 2019 in the Hubei Province in China, factories closed and people quarantined and ceased their daily activities. So, shopping, regular work schedules and more quickly phased out of everyday life. As the outbreak grew in Italy, the same measures were taken.
TROPOMI, the Tropospheric Monitoring Instrument onboard the Copernicus satellite — which is a collaboration among the European Space Agency, the European Commission, the Netherlands Space Office, industry, data users and scientists — has been observing these atmospheric changes from space.
The Copernicus Atmosphere Monitoring Service (CAMS) has been, with this instrument, identifying a significant drop in fine particulate matter (a major air pollutant). With both satellite observations and computer models of the atmosphere, researchers have found a 20%-30% decrease in surface particulate matter over huge swaths of China.
The animation shows, with data from Copernicus, how nitrogen dioxide emissions have dropped from Dec. 20, 2019, to March 16, 2020 (with a 10-day moving average). Toward the end of March, you can see the emissions increase again, but there is a distinct and significant drop in late January.
"Satellites offer a unique vantage point to monitor the health of our planet. Sentinel-5P is one of seven Copernicus satellites in orbit today. It currently provides the most accurate measurements of nitrogen dioxide and other trace gases from space," Josef Aschbacher, ESA's director of Earth observation programs, said in a statement.
"As nitrogen dioxide is primarily produced by traffic and factories, it is a first-level indicator of industrial activity worldwide. What is clearly visible is a significant reduction of nitrogen dioxide levels over China, caused by reduced activity due to COVID-19 restrictions, but also the Chinese New Year in January.”
Still, these are just rough estimates, Claus Zehner, ESA's Copernicus Sentinel-5P mission manager, added in the statement. "We are conducting a detailed scientific analysis which will soon provide more insights and quantified results in the following weeks and months," Zehner said.