09:30 〜 09:45
[ACG34-03] COVID-19の発生で中国の化石燃料起源CO2の減少により引き起こされた、東アジアの流出地域における大気中のCO2/CH4変動の変化
キーワード：新型コロナウイルスの流行、都市封鎖、大気二酸化炭素、大気メタン、シノプティックスケール変動
To prevent the spread of the new coronavirus (COVID-19) in China, the government of China imposed a nationwide lockdown and strict restrictions on the inter-city transport and socio-economic activity during the period from the end of January through March in 2020. Such restrictions were expected to significantly reduce the fossil-fuel-derived CO2 (FFCO2) emissions from China during the above period. Previous study revealed that the ratio of the synoptic-scale variability between CO2 and CH4 (ΔCO2/ΔCH4) observed in the downwind region of the East Asian continent reflected the emission ratio of the source region. Accordingly, since the restrictions would not cause any immediate effects on the CH4 emissions in China, the atmospheric observations in the downwind region would detect the significant reduction of ΔCO2/ΔCH4 ratio during the restriction period.
The National Institute of Environmental Studies (NIES) has been monitoring the atmospheric greenhouse gases including CO2 and CH4 mainly in the Asia Pacific region by using variety of platforms including ground sites, commercial cargo ships, and passenger airplane. The continental marginal region of the East Asia corresponds to the outflow region of the continental emissions during the period from late fall through early spring because of the East Asian monsoon. In this presentation, we examined the temporal or spatial variability ratio between the atmospheric CO2 and CH4 mole fractions obtained from continuous measurements at Hateruma Island (HAT; lat. 24.1°N, long. 123.8°E), in-situ measurements aboard cargo ships sailing between Japan and Southeast Asia, and airplane sampling over Shanghai. For example, the monthly mean ratio of the synoptic scale variations between CO2 and CH4 observed at HAT in February 2020 showed significant decrease in comparison with those observed in the previous decadal period (2010-2019). The decrease in the ΔCO2/ΔCH4 ratio was well reproduced by the model simulation based on an atmospheric transport model (NICAM-TM) and a set of corresponding CO2 and CH4 fluxes when the FFCO2 emissions from China reduced by 30%. The relationship between the atmospheric CO2 and CH4 observed over Shanghai and in the South and East China sea in February 2020 agreed well with the simulated relationship with the similarly reduced FFCO2 emissions from China. These results show the utility of high-precision measurements of CO2 and CH4 to detect signals from the emission change from specific regions.
The National Institute of Environmental Studies (NIES) has been monitoring the atmospheric greenhouse gases including CO2 and CH4 mainly in the Asia Pacific region by using variety of platforms including ground sites, commercial cargo ships, and passenger airplane. The continental marginal region of the East Asia corresponds to the outflow region of the continental emissions during the period from late fall through early spring because of the East Asian monsoon. In this presentation, we examined the temporal or spatial variability ratio between the atmospheric CO2 and CH4 mole fractions obtained from continuous measurements at Hateruma Island (HAT; lat. 24.1°N, long. 123.8°E), in-situ measurements aboard cargo ships sailing between Japan and Southeast Asia, and airplane sampling over Shanghai. For example, the monthly mean ratio of the synoptic scale variations between CO2 and CH4 observed at HAT in February 2020 showed significant decrease in comparison with those observed in the previous decadal period (2010-2019). The decrease in the ΔCO2/ΔCH4 ratio was well reproduced by the model simulation based on an atmospheric transport model (NICAM-TM) and a set of corresponding CO2 and CH4 fluxes when the FFCO2 emissions from China reduced by 30%. The relationship between the atmospheric CO2 and CH4 observed over Shanghai and in the South and East China sea in February 2020 agreed well with the simulated relationship with the similarly reduced FFCO2 emissions from China. These results show the utility of high-precision measurements of CO2 and CH4 to detect signals from the emission change from specific regions.