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Four-dimensional variational data assimilation for inverse modeling of atmospheric methane emissions: Analysis of SCIAMACHY observations

Meirink, Jan Fokke and Bergamaschi, Peter and Frankenberg, Christian and d’Amelio, Monica T. S. and Dlugokencky, Edward J. and Gatti, Luciana V. and Houweling, Sander and Miller, John B. and Röckmann, Thomas and Villani, M. Gabriella and Krol, Maarten C. (2008) Four-dimensional variational data assimilation for inverse modeling of atmospheric methane emissions: Analysis of SCIAMACHY observations. Journal of Geophysical Research. Atmospheres, 113 (D17). Art. No D17301. ISSN 2169-897X. doi:10.1029/2007JD009740. https://resolver.caltech.edu/CaltechAUTHORS:20150511-141831482

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Abstract

Recent observations from the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) instrument aboard ENVISAT have brought new insights in the global distribution of atmospheric methane. In particular, the observations showed higher methane concentrations in the tropics than previously assumed. Here, we analyze the SCIAMACHY observations and their implications for emission estimates in detail using a four-dimensional variational (4D-Var) data assimilation system. We focus on the period September to November 2003 and on the South American continent, for which the satellite observations showed the largest deviations from model simulations. In this set-up the advantages of the 4D-Var approach and the zooming capability of the underlying TM5 atmospheric transport model are fully exploited. After application of a latitude-dependent bias correction to the SCIAMACHY observations, the assimilation system is able to accurately fit those observations, while retaining consistency with a network of surface methane measurements. The main emission increments resulting from the inversion are an increase in the tropics, a decrease in South Asia, and a decrease at northern hemispheric high latitudes. The SCIAMACHY observations yield considerable additional emission uncertainty reduction, particularly in the (sub-)tropical regions, which are poorly constrained by the surface network. For tropical South America, the inversion suggests more than a doubling of emissions compared to the a priori during the 3 months considered. Extensive sensitivity experiments, in which key assumptions of the inversion set-up are varied, show that this finding is robust. Independent airborne observations in the Amazon basin support the presence of considerable local methane sources. However, these observations also indicate that emissions from eastern South America may be smaller than estimated from SCIAMACHY observations. In this respect it must be realized that the bias correction applied to the satellite observations does not take into account potential regional systematic errors, which – if identified in the future – will lead to shifts in the overall distribution of emission estimates.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1029/2007JD009740DOIArticle
http://onlinelibrary.wiley.com/doi/10.1029/2007JD009740/abstractPublisherArticle
http://onlinelibrary.wiley.com/doi/10.1029/2007JD009740/suppinfoPublisherSupporting Information
ORCID:
AuthorORCID
Frankenberg, Christian0000-0002-0546-5857
Dlugokencky, Edward J.0000-0003-0612-6985
Houweling, Sander0000-0002-6189-1009
Röckmann, Thomas0000-0002-6688-8968
Additional Information:© 2008 American Geophysical Union. Received 20 December 2007; Revised 16 April 2008; Accepted 19 June 2008; Published 4 September 2008. Jan Fokke Meirink was supported by the NWO project IMEAS (project EO-087). Peter Bergamaschi was supported by the European Commission RTD project GEMS (Global and regional Earth-system (atmosphere) monitoring using satellite and in-situ data), contract SIP4-CT-2004-516099, 6th Framework Programme. Computer facilities were provided by the Dutch NCF (Nationale Computerfaciliteiten). We thank NOAA-ESRL for providing CarbonTracker data. SAN and MAN air samples were collected as part of the Brazilian-led large-scale biosphere-atmosphere experiment in Amazonia (LBA), and funded from NASA interagency agreements S-10137 and S-71307.
Funders:
Funding AgencyGrant Number
Netherlands Organization for Scientific Research (NWO)EO-087
European CommissionSIP4-CT-2004-516099
NASAS-10137
NASAS-71307
Issue or Number:D17
DOI:10.1029/2007JD009740
Record Number:CaltechAUTHORS:20150511-141831482
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20150511-141831482
Official Citation:Meirink, J. F., Bergamaschi, P., Frankenberg, C., d'Amelio, M. T. S., Dlugokencky, E. J., Gatti, L. V., . . . Krol, M. C. (2008). Four-dimensional variational data assimilation for inverse modeling of atmospheric methane emissions: Analysis of SCIAMACHY observations. Journal of Geophysical Research: Atmospheres, 113(D17), D17301. doi: 10.1029/2007jd009740
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:57423
Collection:CaltechAUTHORS
Deposited By: Joanne McCole
Deposited On:12 May 2015 17:43
Last Modified:10 Nov 2021 21:12

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