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| Titel |
The imprint of surface fluxes and transport on variations in total column carbon dioxide |
| VerfasserIn |
G. Keppel-Aleks, P. O. Wennberg, R. A. Washenfelder, D. Wunch, T. Schneider, G. C. Toon, R. J. Andres, J.-F. Blavier, B. Connor, K. J. Davis, A. R. Desai, J. Messerschmidt, J. Notholt, C. M. Roehl, V. Sherlock, B. B. Stephens, S. A. Vay, S. C. Wofsy |
| 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. 3 ; Nr. 9, no. 3 (2012-03-01), S.875-891 |
| Datensatznummer |
250006831
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| Publikation (Nr.) |
 copernicus.org/bg-9-875-2012.pdf |
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| Zusammenfassung |
| New observations of the vertically integrated CO2 mixing ratio,
⟨CO2⟩, from ground-based remote sensing show that
variations in CO2⟩ are primarily determined by
large-scale flux patterns. They therefore provide fundamentally different
information than observations made within the boundary layer, which reflect
the combined influence of large-scale and local fluxes. Observations of both
⟨CO2⟩ and CO2 concentrations in the free
troposphere show that large-scale spatial gradients induce synoptic-scale
temporal variations in ⟨CO2⟩ in the Northern
Hemisphere midlatitudes through horizontal advection. Rather than obscure the
signature of surface fluxes on atmospheric CO2, these synoptic-scale
variations provide useful information that can be used to reveal the
meridional flux distribution. We estimate the meridional gradient in
⟨CO2⟩ from covariations in
⟨CO2⟩ and potential temperature, θ, a
dynamical tracer, on synoptic timescales to evaluate surface flux estimates
commonly used in carbon cycle models. We find that simulations using Carnegie
Ames Stanford Approach (CASA) biospheric fluxes underestimate both the
⟨CO2⟩ seasonal cycle amplitude throughout the
Northern Hemisphere midlatitudes and the meridional gradient during the
growing season. Simulations using CASA net ecosystem exchange (NEE) with
increased and phase-shifted boreal fluxes better fit the observations. Our
simulations suggest that climatological mean CASA fluxes underestimate boreal
growing season NEE (between 45–65° N) by ~40%. We
describe the implications for this large seasonal exchange on inference of
the net Northern Hemisphere terrestrial carbon sink. |
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