Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 17, 4781-4797, 2017
http://www.atmos-chem-phys.net/17/4781/2017/
doi:10.5194/acp-17-4781-2017
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
12 Apr 2017
Consistent regional fluxes of CH4 and CO2 inferred from GOSAT proxy XCH4 : XCO2 retrievals, 2010–2014
Liang Feng1, Paul I. Palmer1, Hartmut Bösch2, Robert J. Parker2, Alex J. Webb2, Caio S. C. Correia3, Nicholas M. Deutscher4,5, Lucas G. Domingues3, Dietrich G. Feist6, Luciana V. Gatti3, Emanuel Gloor7, Frank Hase8, Rigel Kivi9, Yi Liu10, John B. Miller11,12, Isamu Morino13, Ralf Sussmann14, Kimberly Strong15, Osamu Uchino13, Jing Wang10, and Andreas Zahn16 1National Centre for Earth Observation, School of GeoSciences, University of Edinburgh, Edinburgh, UK
2National Centre for Earth Observation, Department of Physics and Astronomy, University of Leicester, Leicester, UK
3Instituto de Pesquisas Energéticas e Nucleares (IPEN) – Comissao Nacional de Energia Nuclear (CNEN) – Atmospheric Chemistry Laboratory, Cidade Universitaria, São Paulo, Brazil
4Institute of Environmental Physics, University of Bremen, Bremen, Germany
5Centre for Atmospheric Chemistry, University of Wollongong, Wollongong, Australia
6Max Planck Institute for Biogeochemistry, Jena, Germany
7School of Geography, University of Leeds, Leeds, UK
8Karlsruhe Institute of Technology (KIT), IMK-ASF, Karlsruhe, Germany
9FMI-Arctic Research Center, Sodankylä, Finland
10Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
11Global Monitoring Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO, USA
12Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, CO, USA
13National Institute for Environmental Studies (NIES), Tsukuba, Japan
14Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research - Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany
15Department of Physics, University of Toronto, Toronto, Canada
16Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research (IMK), Eggenstein-Leopoldshafen, Germany
Abstract. We use the GEOS-Chem global 3-D model of atmospheric chemistry and transport and an ensemble Kalman filter to simultaneously infer regional fluxes of methane (CH4) and carbon dioxide (CO2) directly from GOSAT retrievals of XCH4 : XCO2, using sparse ground-based CH4 and CO2 mole fraction data to anchor the ratio. This work builds on the previously reported theory that takes into account that (1) these ratios are less prone to systematic error than either the full-physics data products or the proxy CH4 data products; and (2) the resulting CH4 and CO2 fluxes are self-consistent. We show that a posteriori fluxes inferred from the GOSAT data generally outperform the fluxes inferred only from in situ data, as expected. GOSAT CH4 and CO2 fluxes are consistent with global growth rates for CO2 and CH4 reported by NOAA and have a range of independent data including new profile measurements (0–7 km) over the Amazon Basin that were collected specifically to help validate GOSAT over this geographical region. We find that large-scale multi-year annual a posteriori CO2 fluxes inferred from GOSAT data are similar to those inferred from the in situ surface data but with smaller uncertainties, particularly over the tropics. GOSAT data are consistent with smaller peak-to-peak seasonal amplitudes of CO2 than either the a priori or in situ inversion, particularly over the tropics and the southern extratropics. Over the northern extratropics, GOSAT data show larger uptake than the a priori but less than the in situ inversion, resulting in small net emissions over the year. We also find evidence that the carbon balance of tropical South America was perturbed following the droughts of 2010 and 2012 with net annual fluxes not returning to an approximate annual balance until 2013. In contrast, GOSAT data significantly changed the a priori spatial distribution of CH4 emission with a 40 % increase over tropical South America and tropical Asia and a smaller decrease over Eurasia and temperate South America. We find no evidence from GOSAT that tropical South American CH4 fluxes were dramatically affected by the two large-scale Amazon droughts. However, we find that GOSAT data are consistent with double seasonal peaks in Amazonian fluxes that are reproduced over the 5 years we studied: a small peak from January to April and a larger peak from June to October, which are likely due to superimposed emissions from different geographical regions.

Citation: Feng, L., Palmer, P. I., Bösch, H., Parker, R. J., Webb, A. J., Correia, C. S. C., Deutscher, N. M., Domingues, L. G., Feist, D. G., Gatti, L. V., Gloor, E., Hase, F., Kivi, R., Liu, Y., Miller, J. B., Morino, I., Sussmann, R., Strong, K., Uchino, O., Wang, J., and Zahn, A.: Consistent regional fluxes of CH4 and CO2 inferred from GOSAT proxy XCH4 : XCO2 retrievals, 2010–2014, Atmos. Chem. Phys., 17, 4781-4797, doi:10.5194/acp-17-4781-2017, 2017.
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Short summary
We use the GEOS-Chem global 3-D model of atmospheric chemistry and transport and an ensemble Kalman filter to simultaneously infer regional fluxes of methane (CH4) and carbon dioxide (CO2) directly from GOSAT retrievals of XCH4:XCO2, using sparse ground-based CH4 and CO2 mole fraction data to anchor the ratio. Our results show that assimilation of GOSAT data significantly reduced the posterior uncertainty and changed the a priori spatial distribution of CH4 emissions.
We use the GEOS-Chem global 3-D model of atmospheric chemistry and transport and an ensemble...
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