COVID-19 lockdowns and air quality: Evidence from grey spatiotemporal forecasts.

This paper proposes a novel grey spatiotemporal model and quantitatively analyzes the spillover and momentum effects of the COVID-19 lockdown policy on the concentration of PM2.5 (particulate matter of diameter less than 2.5 μm) in Wuhan during the COVID-19 pandemic lockdown from 23 January to 8 April 2020 inclusive, and the post-pandemic period from 9 April 2020 to 17 October 2020 inclusive. The results suggest that the stringent lockdowns lead to a reduction in PM2.5 emissions arising from a momentum effect (9.57–18.67%) and a spillover effect (7.07–27.60%). • This paper proposes a novel spatiotemporal grey model for PM2.5 trend forecasting. • This paper considers the momentum effect of historical policies on PM2.5 emission. • Comparing the forecast of PM2.5 with actual values, this paper quantifies the spillover effect of lockdown policies. • A lockdown has a positive knock-on effect on urban air quality. [ABSTRACT FROM AUTHOR]