Evident PM_2.5 Drops in the East of China due to the COVID-19 Quarantines in February

Abstract. The top-level emergency response to the COVID-19 pandemic involved an exhaustive quarantine in China. The impacts of COVID-19 quarantine on the decline in fine particulate matter (PM_2.5) were quantitatively assessed based on numerical simulations and observations in February. The stable meteorological conditions in February 2020 caused considerable PM_2.5 anomalies that were eliminated in advance. The contributions of routine emission reductions were also quantitatively extrapolated. The top-level emergency response substantially alleviated the level of haze pollution in the east of China. Although climate variability elevated the PM_2.5 by 29 % (relative to 2020 observations), 59 % decline related to COVID-19 pandemic and 20 % decline from the expected pollution regulation dramatically exceeded the former in North China. The COVID-19 quarantine measures decreased the PM_2.5 in Yangtze River Delta by 72 %. In Hubei Province where most pneumonia cases were confirmed, the impact of total emission reduction (72 %) evidently exceeded the rising percentage of PM_2.5 driven by meteorology (13 %).