11:00 〜 13:00
[ACG37-P03] 八重山諸島における大気観測から推定されたCOVID-19都市封鎖後の中国からのCO2排出量の回復
キーワード：新型コロナウイルスの流行、大気中二酸化炭素、大気中メタン、総観規模変動
Explosive spread of the new coronavirus infection (COVID-19) in China, through a nationwide lockdown, resulted in substantial reduction of fossil fuel-derived CO2 emissions from China. Although about 20% reduction in February 2020 was estimated by compiling variety of economic indices, it is crucially important to validate the CO2 emission changes by using independent and scientific approaches. In previous studies, we revealed that the synoptic-scale variability ratio between atmospheric CO2 and CH4 (ΔCO2/ΔCH4) observed at Hateruma Island (HAT; lat. 24.1°N, long. 123.8°E) and Yonaguni Island (YON, 24.5°N, 123.0°E) during January to March were useful to detect the change in the relative emissions from China. The ΔCO2/ΔCH4 ratios for HAT and YON showed marked decreases in February 2020 in association with the COVID-19 lockdown in China. In this presentation, we estimate the recent change in the CO2 emissions from China after COVID-19 lockdown based on the ΔCO2/ΔCH4 ratios observed at HAT and YON.
In accordance with the previous studies, the monthly ΔCO2/ΔCH4 ratio was computed as an average of slopes of the scatter plots for the data within a certain time window (24-hour for HAT and 84-hour for YON), which was repeatedly shifted by one hour for the entire data set. Note that in addition to rather longer time window only night-time data (20-6 LST) were used to calculate the ΔCO2/ΔCH4 ratios for YON to suppress the local influences on the variability ratios.
The monthly ΔCO2/ΔCH4 ratios for HAT (YON) in January, February, and March during 9-year period (2011-2019) showed relatively stable values, of which average was 131 ± 10 (130 ± 11) mol/mol, whereas the ratio decreased to the value of 100 (97) mol/mol in February 2020. In 2021, the ratios for both sites became almost equal to or a little larger than those for the preceding 9-year period before the COVID-19 lockdown: 146 (149), 126 (126), and 147 (170) for January, February, and March, respectively, for HAT (YON). Assuming that the CH4 emissions from China were stable after 2019, the CO2 emissions from China during January to March in 2021 corresponded to about 119 ± 22% of the emission in 2019. This result is consistent with the recovery of China’s economy after COVID-19 lockdown: China’s GDP returned growth as early as in the second quarter in 2020 and its year-on-year growth rate reached more than 18% in the first quarter in 2021.
In accordance with the previous studies, the monthly ΔCO2/ΔCH4 ratio was computed as an average of slopes of the scatter plots for the data within a certain time window (24-hour for HAT and 84-hour for YON), which was repeatedly shifted by one hour for the entire data set. Note that in addition to rather longer time window only night-time data (20-6 LST) were used to calculate the ΔCO2/ΔCH4 ratios for YON to suppress the local influences on the variability ratios.
The monthly ΔCO2/ΔCH4 ratios for HAT (YON) in January, February, and March during 9-year period (2011-2019) showed relatively stable values, of which average was 131 ± 10 (130 ± 11) mol/mol, whereas the ratio decreased to the value of 100 (97) mol/mol in February 2020. In 2021, the ratios for both sites became almost equal to or a little larger than those for the preceding 9-year period before the COVID-19 lockdown: 146 (149), 126 (126), and 147 (170) for January, February, and March, respectively, for HAT (YON). Assuming that the CH4 emissions from China were stable after 2019, the CO2 emissions from China during January to March in 2021 corresponded to about 119 ± 22% of the emission in 2019. This result is consistent with the recovery of China’s economy after COVID-19 lockdown: China’s GDP returned growth as early as in the second quarter in 2020 and its year-on-year growth rate reached more than 18% in the first quarter in 2021.