Qianqian Yang, Bin Wang, Yuan Wang, Qiangqiang Yuan, Caiyi Jin, Jiwen Wang, Shuwen Li, Muyu Li, Tongwen Li, Song Liu, Huanfeng Shen, Liangpei Zhang

In recent months, coronavirus disease 2019 (COVID-19) has been spreading around the globe, and this has led to a rare reduction in human activities. In such a background, data from ground-based environmental stations, satellites, and reanalysis materials are utilized to conduct a comprehensive analysis of the air quality changes during the COVID-19 outbreak at the global scale. The results showed that under the impact of the COVID-19 outbreak, a significant decrease in particulate matter (PMx) and nitrogen dioxide (NO2) occurred in more than 40% of the world’s land area, with NO2 decreasing by approximately 30% and PMx decreasing approximately 20%. In addition, the mobility, meteorological factors, and the response speed to COVID-19 outbreaks in cities were examined, and it was further found that in quick-response cities, lockdowns produced a sharp decline in mobility in a short time. This had a large impact on air quality. In contrast, in slow-response cities, declines in mobility occurred beginning with the confirmation of the first COVID-19 case (FCC) and dropped gradually for a relatively long period. The impact of the FCC, lockdowns, and meteorological factors on air quality can be comparable.