Satellite based analysis on covariation of air pollution and human activities in Guangdong during COVID-19 lockdown

The relationship between air pollution emissions and economic development has been a research hot spot in the last few decades. Lockdowns caused by novel coronavirus provide an unprecedented opportunity to deepen our understanding to the possible mechanism of the covariation between human economical activities and air pollutant events. In this paper, satellite derived aerosol optical depth (AOD) and Nighttime light (NTL) data were used as agencies for air pollution and economic activities respectively. The results show that NTL in Feb. 2020 is lower than the same month of previous year in most of the eight cities of Guangdong Province, Northern China. That indicates lower NTL may due to less activities of social activities, tourism and industrial production because of lockdown during COVID-19 pandemic. Meanwhile, AOD also sharply decreases in Feb. 2020. And, both trends of NTL and AOD turned over as soon as March 2020. The correlations between AOD and NTL of these eight cities are quite different from each other, somehow them are more correspondingly close to 1 during COVID-19 from Dec. 2019 to Feb. 2020. That may suggest solid covariation between AOD and NTL, and may indicate human economic activities may be one of the reasons leading to air pollution.