Chinese NOx emission reductions and rebound as a result of the COVID-19
crisis quantified through inversion of TROPOMI NO2 observations
During the COVID-19 lockdown in China low air pollution levels were
reported as a consequence of the reduced economic and social activities.
Quantification of the pollution reduction is not straightforward due to
effects of transport, meteorology, and chemistry. Here we have analysed
the NO emission reductions calculated with an inverse algorithm applied
to daily NO observations from the TROPOMI instrument onboard the
Copernicus Sentinel-5P satellite. This method allows quantification of
emission reductions per city, and the analysis of emissions of maritime
transport and of the energy sector separately. The reductions we found
are 20 to 50% for cities, about 40% for power plants and 15 to 40%
for maritime transport depending on the region. The reduction in both
emissions and concentrations shows a similar timeline consisting of a
sharp reduction around the Spring festival and a slow recovery from
mid-February to mid-March.