[A-CG35] グローバル炭素循環の観測と解析

[ACG35-06] Estimate of country-scale methane emissions in Asia by GOSAT and surface atmospheric observations

*Fenjuan Wang¹、Shamil S Maksyutov¹、Rajesh Janardanan¹、Aki Tsuruta²、Akihiko Ito¹、Isamu Morino¹、Yukio Yoshida¹、Yasunori Tohjima¹、Johannes W. Kaiser³、Xin Lan^4,5、Ivan Mammarella⁶、Jost V. Lavric^7,8、Tsuneo Matsunaga¹ (1.NIES National Institute of Environmental Studies、2.Finnish Meteorological Institute, Finland、3.Deutscher Wetterdienst, Germany 、4.Cooperative Institute for Research in Environmental Sciences, University of Colorado, USA 、5.National Oceanic and Atmospheric Administration, USA 、6.University of Helsinki, Finland 、7.Max Planck Institute for Biogeochemistry, Germany、8.now at Acoem, Australia)

キーワード：methane emission, GOSAT satellite , high-resolution inverse model

We present the top-down estimates of methane (CH₄) emissions in Asia countries from 2009 to 2018 and their trend in two five-yearly periods (Wang et al., 2021, ERL). It is the first comprehensive top-down estimate of CH₄ emissions in Asia at a country scale, which serves as an independent evaluation for the global stocktake under the Paris Agreement in 2023. We used the high-resolution global inverse model NIES-TM-FLEXPART-VAR and atmospheric observations from surface observation network and GOSAT satellite to deduce country-scale emissions. There are 13 countries that emit more than 1 Tg y^-1, together emitting more than 97% of the total CH₄ emissions in Asia. Anthropogenic emissions are dominant in most of these countries except Bangladesh and Cambodia. We also analyzed two five-year CH₄ emission budgets for the three subregions East Asia (EA), Southeast Asia (SEA), South Asia (SA), and the 13 top emitting countries. In the first and second five-yearly periods, the mean posterior emissions in EA are both lower than the mean prior emissions. The mean posterior emissions in SEA and SA are higher than the mean prior emissions during 2009-2013, but lower during 2014-2018. The mean posterior emission in SA decreases from the first five-yearly period to the second five-yearly period. The optimized total emissions in China, Japan, and South Korea show more significant increases than the prior estimates. The optimized total emissions in other countries show less increase compared to the prior estimates, in which India, Pakistan, Thailand, Bangladesh, and Myanmar obtain higher optimized emissions during the first five-yearly period compared to the prior emissions. We also found that climate variability may have a distinct influence on the interannual variability in the CH₄ flux in different regions of Asia and suggest that more detailed drivers should be accounted for more precise country emission evaluation in the global stocktake.