Lockdowns were performed worldwide to contain 2019 novel coronavirus (COVID-19) spreads, while the control strategies demonstrated dramatic regional discrepancies. Using space-based Ozone Monitoring Instrument (OMI) nitrogen dioxide (NO₂) and Chinese situ NO2 measurements, here we monitor COVID-19 to evaluate the different measurements. We find significant reductions of tropospheric NO₂ columns due to COVID-19 controls by more than 40%. The perturbations in tropospheric NO₂ diminished accompanied with the mitigation of COVID-19 pandemic, and finally disappeared within around 50-70 days after the starts of control measures, providing indications for the start, maximum, and relaxation of intensive controls.
 

situ-satellite COVID-19 NO2