Evident PMsub2.5/sub drops in the east of China due to the COVID-19 quarantine measures in February

摘要

The top-level emergency response to the COVID-19 pandemic involved exhaustive quarantine measures in China. The impacts of the COVID-19 quarantine on thedecline in fine particulate matter (PM2.5) were quantitatively assessedbased on numerical simulations and observations in February. Relative toboth February 2017 and the climate mean, anomalous southerlies and moisterair occurred in the east of China in February 2020, which causedconsiderable PM2.5 anomalies. Thus, it is a must to disentangle thecontributions of stable meteorology from the effects of the COVID-19lockdown. The contributions of routine emission reductions were alsoquantitatively extrapolated. The top-level emergency response substantiallyalleviated the level of haze pollution in the east of China. Althoughclimate variability elevated the PM2.5 by 29 % (relative to 2020observations), a 59 % decline related to the COVID-19 pandemic and a 20 %decline from the expected pollution regulation dramatically exceeded theformer in North China. The COVID-19 quarantine measures decreased thePM2.5 in the Yangtze River Delta by 72 %. In Hubei Province where mostpneumonia cases were confirmed, the impact of total emission reduction(72 %) evidently exceeded the rising percentage of PM2.5 driven bymeteorology (13 %).