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| Titel |
Regional CH4 flux estimates based on GOSAT and ground-based observations |
| VerfasserIn |
Shamil Maksyutov, Heon-Sook Kim, Tazu Saeki, Dmitry A. Belikov, Akihiko Ito, Isamu Morino, Osamu Uchino, Yukio Yoshida, Tatsuya Yokota |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250075120
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| Zusammenfassung |
| Monthly CH4 fluxes for 43 regions in 2009-2010 are estimated by an inverse model using the
GOSAT SWIR Level 2 XCH4 data and ground-based CH4 observations archived at WDCGG.
The flux estimates and global distribution of methane concentrations in the atmosphere are
prepared for a distribution as the GOSAT Level 4 research product. We used interannually
varying CH4 emissions by the GFED and VISIT ecosystem model and the interannually
repeating EDGAR CH4 emissions and chemical sink fields prepared by the TransCom-CH4
project in a forward simulation by the NIES transport model. Scale adjustments were applied
to 4 categories of fluxes independently for each region. The inverse problem of optimizing the
fluxes was solved with a fixed-lag Kalman smoother. We compared the inversion results
using the two different datasets to assess the utility of GOSAT XCH4 data in flux
estimates and found good fit to the data with chi-square values of 0.7 and 1.2 with
fluxes estimated using ground-based data only and both ground-based and GOSAT
data, respectively. Mean residual misfit between simulations and GOSAT data is 5
ppb, which is smaller than difference with TCCON and GOSAT observations. The
inversion using ground-based data only estimated larger uncertainty of fluxes over
tropical regions, South America and Temperate Asia where the data are sparse.
Adding large number of the GOSAT data to the inversion leads to decreasing the
uncertainty in Temperate Asia (by 41%), northern South America (26%), Tropical Asia
(24%), Europe (23%) and other regions. Monthly mean XCH4 simulated with fluxes
estimated using the ground-based data is close to the GOSAT observations in the north
of 40Ë N, but lower than GOSAT in southern hemisphere, and the difference can
be attributed to possible biases in XCH4 observations and the transport model.
Authors acknowledge contribution of the ground-based FTS data by TCCON partners. |
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