Spaceborne NO2 column observations from two high‐resolution instruments, TROPOMI onboard Sentinel‐5 Precursor and OMI on Aura, reveal unprecedented NO2 decreases over China, South Korea, Western Europe and the U.S. as a result of public health measures enforced to contain the coronavirus disease outbreak (Covid‐19) in January‐April 2020. The average NO2 column drop over all Chinese cities amounts to ‐40% relative to the same period in 2019, and reaches up to a factor of ~2 at heavily hit cities, e.g. Wuhan, Jinan, while the decreases in Western Europe and the U.S. are also significant (‐20 to ‐38%). In contrast with this, although Iran is also strongly affected by the disease, the observations do not show evidence of lower emissions, reflecting more limited health measures.
Key Points Satellite NO2 data show substantial decreases by 40% on average over Chinese cities due to lockdown measures against the Covid‐19 outbreakWestern Europe and U.S. display robust NO2 decreases in 2020, 20‐38% relative to the same period in 2019Satellite NO2 observations above Iran, a region strongly affected by coronavirus, do not show clear evidence of lower emissions