Column-averaged dry-air mole fractions of CO2 and CO based on EM27/SUN over urban Beijing during COVID-19 outbreak

Abstract:

Fast-spreading coronavirus COVID-19 reduced population mobility and economic activities, which caused a notable impact on the greenhouse gas and air pollution emission. This also occurred in Beijing region which was recognized as one of the most polluted regions in China. Here, we present the correlation of excess column-averaged dry-air mole fractions of CO₂ and CO (ΔXCO₂, ΔXCO) in afternoon compared to counterpart in the morning observed from EM27/SUN over urban Beijing during COVID-19 epidemic.

The average mean XCO₂ and XCO from January to March 2020 show 3ppm, 8ppb higher than the same period in 2019 respectively. However, the regression line fit slope of ΔXCO to ΔXCO₂ (ΔXCO /ΔXCO₂) in 2020 (4.75 ppb/ppm) is significantly smaller than the value in 2019 (5.84 ppb/ppm), implying less anthropogenic proportion of CO₂ emissions during COVID-19 outbreak.

Furthermore, ΔXCO /ΔXCO₂ from different upwind sources in January to March 2019 and 2020 are discussed. ΔXCO /ΔXCO₂ from northwest upwind with high wind speed days in 2020 (N_day = 17 d, slope = 4.91 ppb/ppm) shows smaller than the ΔXCO /ΔXCO₂ in 2019 (N_day = 11d, slope = 5.89 ppb/ppm). Meanwhile, ΔXCO /ΔXCO₂ from windy days with upwind directions except northwest in 2020 (N_day = 14 d, slope = 4.75 ppb/ppm) shows smaller than the value in 2019 (N_day = 14 d, slope = 7.87 ppb/ppm). The northwest upwind region of Beijing (Inner Mongolia and Mongolia) is relatively cleaner than other direction upwind sources (Hebei and Tianjin). The difference of ΔXCO /ΔXCO₂ between northwest upwind with others in 2019 shows larger than the difference in 2020, suggesting the reduction of anthropogenic CO₂ emission in the polluted area surrounding Beijing.