Spatiotemporal changes in global nitrogen dioxide emission due to COVID-19 mitigation policies

This paper investigates spatiotemporal changes of nitrogen dioxide (NO2) tropospheric vertical column density due to the COVID-19 pandemic using satellite observations before, during and after the lockdown (hereafter referred as the pre-, peri- and post-periods) in six different countries: China, South Africa, Brazil, India, the UK and the US, and compare these periods with 2019 as well as mean climatology from 2010 to 2019. We observe significant declines in relative differences (RDs) from the pre- to peri-period (as compared with the 10-year climatology) in most study countries including China, South Africa, India, and the UK by 15, 17, 8 and 7% respectively. The US does not demonstrate significant decline with RD difference relatively small at just 2%. Meanwhile, although the 2020 RD of Brazil is 7% lower than 2010–2019, this trend is quite similar to that of 2019 (20% vs 23%). In the post-period of 2020, the NO2 columns rebound in most target countries: China, US, South Africa, Brazil and UK, with similar RDs relative to the corresponding pre-period as compared with 2019 and 2010–2019. In contrast, NO in India continues to be influenced by the ongoing COVID-19 crisis with pre-to-post RD 8% lower than the average of previous 10 years. [Display omitted] •The impacts of COVID-19-related interventional policies on NO2 emissions are analyzed over different countries.•The lockdown policy reduced the overall trend of NO2 emissions in most target countries.•Detrending analysis is conducted to mitigate the influences of inter-annual trends.•After reopening, trends of national-mean NO2 emissions returned to normal track in most target countries.