The implication of the air quality pattern in South Korea after the COVID-19 outbreak.

By using multiple satellite measurements, the changes of the aerosol optical depth (AOD) and nitrogen dioxide (NO) over South Korea were investigated from January to March 2020 to evaluate the COVID-19 effect on the regional air quality. The NO decrease in South Korea was found but not significant, which indicates the effects of spontaneous social distancing under the maintenance of ordinary life. The AODs in 2020 were normally high in January, but they became lower starting from February.