Abrupt decline in tropospheric nitrogen dioxide over China after the outbreak of COVID-19

TLDR

China’s COVID‑19 containment measures have both environmental and economic impacts, as tropospheric nitrogen dioxide—primarily from fossil fuel combustion—serves as a proxy for economic activity. The study aims to link the observed decline in tropospheric nitrogen dioxide to specific government actions during the pandemic. The authors analyze satellite data by correlating the nitrogen dioxide drop with the timing of provincial first‑report announcements and lockdown dates. Satellite data reveal a 48 % reduction in tropospheric nitrogen dioxide after the Lunar New Year, a 21 % larger decline than the 2015‑2019 average, with both provincial report announcements and lockdowns driving comparable reductions and highlighting unintended environmental and economic effects.

Abstract

China's policy interventions to reduce the spread of the coronavirus disease 2019 have environmental and economic impacts. Tropospheric nitrogen dioxide indicates economic activities, as nitrogen dioxide is primarily emitted from fossil fuel consumption. Satellite measurements show a 48% drop in tropospheric nitrogen dioxide vertical column densities from the 20 days averaged before the 2020 Lunar New Year to the 20 days averaged after. This decline is 21 ± 5% larger than that from 2015 to 2019. We relate this reduction to two of the government's actions: the announcement of the first report in each province and the date of a province's lockdown. Both actions are associated with nearly the same magnitude of reductions. Our analysis offers insights into the unintended environmental and economic consequences through reduced economic activities.