Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 12, issue 18
Biogeosciences, 12, 5393–5414, 2015
https://doi.org/10.5194/bg-12-5393-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 12, 5393–5414, 2015
https://doi.org/10.5194/bg-12-5393-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 18 Sep 2015

Research article | 18 Sep 2015

Natural and anthropogenic methane fluxes in Eurasia: a mesoscale quantification by generalized atmospheric inversion

A. Berchet1,a, I. Pison1, F. Chevallier1, J.-D. Paris1, P. Bousquet1, J.-L. Bonne1, M. Y. Arshinov2, B. D. Belan2, C. Cressot1, D. K. Davydov2, E. J. Dlugokencky3, A. V. Fofonov2, A. Galanin4, J. Lavrič5, T. Machida6, R. Parker7, M. Sasakawa6, R. Spahni8, B. D. Stocker8, and J. Winderlich9 A. Berchet et al.
  • 1Laboratoire des Sciences du Climat et de l'Environnement, CEA-CNRS-UVSQ, IPSL, Gif-sur-Yvette, France
  • 2V. E. Zuev Institute of Atmospheric Optics, SB-RAS, Tomsk, Russia
  • 3NOAA Earth System Research Laboratory, Boulder, Colorado, USA
  • 4P. E. Melnikov Permafrost Institute SB-RAS, Yakutsk, Russia
  • 5Max Planck Institute for Biogeochemistry, Jena, Germany
  • 6Center for Global Environmental Research, National Institute for Environmental Studies, Tsukuba, Japan
  • 7University of Leicester, Leicester, UK
  • 8Climate and Environmental Physics, Physics Institute, and Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
  • 9Max Planck Institute for Chemistry, Mainz, Germany
  • anow at: Laboratory for Air Pollution/Environmental Technology, Swiss Federal Laboratories for Materials Science and Technology, Empa, Dübendorf, Switzerland

Abstract. Eight surface observation sites providing quasi-continuous measurements of atmospheric methane mixing ratios have been operated since the mid-2000's in Siberia. For the first time in a single work, we assimilate 1 year of these in situ observations in an atmospheric inversion. Our objective is to quantify methane surface fluxes from anthropogenic and wetland sources at the mesoscale in the Siberian lowlands for the year 2010. To do so, we first inquire about the way the inversion uses the observations and the way the fluxes are constrained by the observation sites. As atmospheric inversions at the mesoscale suffer from mis-quantified sources of uncertainties, we follow recent innovations in inversion techniques and use a new inversion approach which quantifies the uncertainties more objectively than the previous inversion systems. We find that, due to errors in the representation of the atmospheric transport and redundant pieces of information, only one observation every few days is found valuable by the inversion. The remaining high-resolution quasi-continuous signal is representative of very local emission patterns difficult to analyse with a mesoscale system. An analysis of the use of information by the inversion also reveals that the observation sites constrain methane emissions within a radius of 500 km. More observation sites than the ones currently in operation are then necessary to constrain the whole Siberian lowlands. Still, the fluxes within the constrained areas are quantified with objectified uncertainties. Finally, the tolerance intervals for posterior methane fluxes are of roughly 20 % (resp. 50 %) of the fluxes for anthropogenic (resp. wetland) sources. About 50–70 % of Siberian lowlands emissions are constrained by the inversion on average on an annual basis. Extrapolating the figures on the constrained areas to the whole Siberian lowlands, we find a regional methane budget of 5–28 TgCH4 for the year 2010, i.e. 1–5 % of the global methane emissions. As very few in situ observations are available in the region of interest, observations of methane total columns from the Greenhouse Gas Observing SATellite (GOSAT) are tentatively used for the evaluation of the inversion results, but they exhibit only a marginal signal from the fluxes within the region of interest.

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