The Spring Festival Effect: the change of NO2 column concentration in China caused by the migration of human activities

The Spring Festival is the most important holiday in China, human activity and population mobility may contribute greatly to air quality, especially in the megacities. According to the satellite-based tropospheric nitrogen dioxide (NO₂) column and ground-based observational concentration of NO₂ in the megacities from 2013 to 2018 around the Spring Festival, we found that NO₂ concentration decreases obviously during the Spring Festival and rebounds after the Spring Festival in China, particularly in the megacities. The tropospheric NO₂ columns density around Beijing-Tianjin-Hebei region decreases about 40% than the period before the festival, and it in Beijing decreases by 41.6% and rebounds by 22.3%. While under the Coronavirus disease 2019 (COVID-19) pandemic progresses, the tropospheric NO₂ columns density in Beijing decreases by 56.2% and rebounds only by 6.8% in 2020.