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| Titel |
North American CO2 exchange: inter-comparison of modeled estimates with results from a fine-scale atmospheric inversion |
| VerfasserIn |
S. M. Gourdji, K. L. Mueller, V. Yadav, D. N. Huntzinger, A. E. Andrews, M. Trudeau, G. Petron, T. Nehrkorn, J. Eluszkiewicz, J. Henderson, D. Wen, J. Lin, M. Fischer, C. Sweeney, A. M. Michalak |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 1 ; Nr. 9, no. 1 (2012-01-25), S.457-475 |
| Datensatznummer |
250006676
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| Publikation (Nr.) |
 copernicus.org/bg-9-457-2012.pdf |
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| Zusammenfassung |
| Atmospheric inversion models have the potential to quantify CO2 fluxes
at regional, sub-continental scales by taking advantage of near-surface
CO2 mixing ratio observations collected in areas with high flux
variability. This study presents results from a series of regional
geostatistical inverse models (GIM) over North America for 2004, and uses
them as the basis for an inter-comparison to other inversion studies and
estimates from biospheric models collected through the North American Carbon
Program Regional and Continental Interim Synthesis. Because the GIM approach
does not require explicit prior flux estimates and resolves fluxes at fine
spatiotemporal scales (i.e. 1° × 1°, 3-hourly in this study), it avoids
temporal and spatial aggregation errors and allows for the recovery of
realistic spatial patterns from the atmospheric data relative to previous
inversion studies. Results from a GIM inversion using only available
atmospheric observations and a fine-scale fossil fuel inventory were used to
confirm the quality of the inventory and inversion setup. An inversion
additionally including auxiliary variables from the North American Regional
Reanalysis found inferred relationships with flux consistent with
physiological understanding of the biospheric carbon cycle. Comparison of GIM
results with bottom-up biospheric models showed stronger agreement during the
growing relative to the dormant season, in part because most of the
biospheric models do not fully represent agricultural land-management
practices and the fate of both residual biomass and harvested products.
Comparison to earlier inversion studies pointed to aggregation errors as a
likely source of bias in previous sub-continental scale flux estimates,
particularly for inversions that adjust fluxes at the coarsest scales and use
atmospheric observations averaged over long periods. Finally, whereas the
continental CO2 boundary conditions used in the GIM inversions have a
minor impact on spatial patterns, they have a substantial impact on the
continental carbon budget, with a difference of 0.8 PgC yr−1 in the total
continental flux resulting from the use of two plausible sets of boundary
CO2 mixing ratios. Overall, this inter-comparison study helps to
assess the state of the science in estimating regional-scale CO2
fluxes, while pointing towards the path forward for improvements in future
top-down and bottom-up modeling efforts. |
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