Japan Geoscience Union Meeting 2021

Presentation information

[E] Oral

A (Atmospheric and Hydrospheric Sciences ) » A-CG Complex & General

[A-CG34] Global Carbon Cycle Observation and Analysis

Sat. Jun 5, 2021 9:00 AM - 10:30 AM Ch.08 (Zoom Room 08)

convener:Kazuhito Ichii(Chiba University), Prabir Patra(Research Institute for Global Change, JAMSTEC), Akihiko Ito(National Institute for Environmental Studies), Chairperson:Prabir Patra(Research Institute for Global Change, JAMSTEC), Kazuhito Ichii(Chiba University)

9:30 AM - 9:45 AM

[ACG34-03] Changes in the atmospheric CO2/CH4 variability in the East Asian outflow region caused by plummet of fossil fuel-derived CO2 in China due to COVID-19 outbreak

*Yasunori Tohjima1, Prabir Patra2, Yosuke Niwa1, Hitoshi Mukai1, Motoki Sasakawa1, Toshinobu Machida1, Shin-ichiro Nakaoka1 (1.National Institute for Environmental Studies, 2.Japan Agency for Marine-Earth Science and Technology)

Keywords:COVID-19 outbreak, lockdown, atmospheric CO2, atmospheric CH4, synoptic-scale variation

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.