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

<p>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.</p>