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| Titel |
Regional inversion of CO2 ecosystem fluxes from atmospheric measurements: reliability of the uncertainty estimates |
| VerfasserIn |
G. Broquet, F. Chevallier, F.-M. Bréon, N. Kadygrov, M. Alemanno, F. Apadula, S. Hammer, L. Haszpra, F. Meinhardt, J. A. Morguí, J. Necki, S. Piacentino, M. Ramonet, M. Schmidt, R. L. Thompson, A. T. Vermeulen, C. Yver, P. Ciais |
| 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. 17 ; Nr. 13, no. 17 (2013-09-10), S.9039-9056 |
| Datensatznummer |
250085685
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| Publikation (Nr.) |
 copernicus.org/acp-13-9039-2013.pdf |
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| Zusammenfassung |
| The Bayesian framework of CO2 flux inversions permits estimates of
the retrieved flux uncertainties. Here, the reliability of these
theoretical estimates is studied through a comparison against the
misfits between the inverted fluxes and independent measurements of
the CO2 Net Ecosystem Exchange (NEE) made by the eddy covariance
technique at local (few hectares) scale. Regional inversions at
0.5° resolution are applied for the western European domain
where ~ 50 eddy covariance sites are operated. These inversions
are conducted for the period 2002–2007. They use
a mesoscale atmospheric transport model, a prior estimate of the NEE
from a terrestrial ecosystem model and rely on the variational
assimilation of in situ continuous measurements of CO2 atmospheric
mole fractions. Averaged over monthly periods and over the whole
domain, the misfits are in good agreement with the theoretical
uncertainties for prior and inverted NEE, and pass the chi-square
test for the variance at the 30% and 5%
significance levels respectively, despite the scale mismatch and the
independence between the prior (respectively inverted) NEE and the
flux measurements. The theoretical uncertainty reduction for the
monthly NEE at the measurement sites is 53% while the
inversion decreases the standard deviation of the misfits by
38%. These results build confidence in the NEE
estimates at the European/monthly scales and in their theoretical
uncertainty from the regional inverse modelling system. However, the
uncertainties at the monthly (respectively annual) scale remain larger
than the amplitude of the inter-annual variability of monthly
(respectively annual) fluxes, so that this study does not engender
confidence in the inter-annual variations. The uncertainties at the
monthly scale are significantly smaller than the seasonal
variations. The seasonal cycle of the inverted fluxes is thus
reliable. In particular, the CO2 sink period over the European
continent likely ends later than represented by the prior ecosystem
model. |
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