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| Titel |
Impact of transport model errors on the global and regional methane emissions estimated by inverse modelling |
| VerfasserIn |
R. Locatelli, P. Bousquet, F. Chevallier, A. Fortems-Cheney, S. Szopa, M. Saunois, A. Agusti-Panareda, D. Bergmann, H. Bian, P. Cameron-Smith, M. P. Chipperfield, E. Gloor, S. Houweling, S. R. Kawa, M. Krol, P. K. Patra, R. G. Prinn, M. Rigby, R. Saito, C. Wilson |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 19 ; Nr. 13, no. 19 (2013-10-08), S.9917-9937 |
| Datensatznummer |
250085739
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| Publikation (Nr.) |
 copernicus.org/acp-13-9917-2013.pdf |
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| Zusammenfassung |
A modelling experiment has been conceived to assess the impact of transport
model errors on methane emissions estimated in an atmospheric inversion
system. Synthetic methane observations, obtained from 10 different model
outputs from the international TransCom-CH4 model inter-comparison
exercise, are combined with a prior scenario of methane emissions and sinks,
and integrated into the three-component PYVAR-LMDZ-SACS (PYthon VARiational-Laboratoire de Météorologie Dynamique model with Zooming capability-Simplified
Atmospheric Chemistry System) inversion system to produce 10
different methane emission estimates at the global scale for the year 2005.
The same methane sinks, emissions and initial conditions have been applied to
produce the 10 synthetic observation datasets. The same inversion set-up
(statistical errors, prior emissions, inverse procedure) is then applied to
derive flux estimates by inverse modelling. Consequently, only differences in
the modelling of atmospheric transport may cause differences in the estimated
fluxes.
In our framework, we show that transport model errors lead to a discrepancy
of 27 Tg yr−1 at the global scale, representing 5% of total methane
emissions. At continental and annual scales, transport model errors are
proportionally larger than at the global scale, with errors ranging from
36 Tg yr−1 in North America to 7 Tg yr−1 in Boreal Eurasia
(from 23 to 48%, respectively). At the model grid-scale, the spread of
inverse estimates can reach 150% of the prior flux. Therefore, transport
model errors contribute significantly to overall uncertainties in emission
estimates by inverse modelling, especially when small spatial scales are
examined. Sensitivity tests have been carried out to estimate the impact of
the measurement network and the advantage of higher horizontal resolution in
transport models. The large differences found between methane flux estimates
inferred in these different configurations highly question the consistency of
transport model errors in current inverse systems.
Future inversions should include more accurately prescribed observation
covariances matrices in order to limit the impact of transport model errors
on estimated methane fluxes. |
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