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| Titel |
Using boundary layer equilibrium to reduce uncertainties in transport models and CO2 flux inversions |
| VerfasserIn |
I. N. Williams, W. J. Riley, M. S. Torn, J. A. Berry, S. C. Biraud |
| 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 ; 11, no. 18 ; Nr. 11, no. 18 (2011-09-16), S.9631-9641 |
| Datensatznummer |
250010083
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| Publikation (Nr.) |
 copernicus.org/acp-11-9631-2011.pdf |
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| Zusammenfassung |
| This paper reexamines evidence for systematic errors in atmospheric transport
models, in terms of the diagnostics used to infer vertical mixing rates from
models and observations. Different diagnostics support different conclusions
about transport model errors that could imply either stronger or weaker
northern terrestrial carbon sinks. Conventional mixing diagnostics are
compared to analyzed vertical mixing rates using data from the US Southern
Great Plains Atmospheric Radiation Measurement Climate Research Facility, the
CarbonTracker data assimilation system based on Transport Model version 5
(TM5), and atmospheric reanalyses. The results demonstrate that diagnostics
based on boundary layer depth and vertical concentration gradients do not
always indicate the vertical mixing strength. Vertical mixing rates are
anti-correlated with boundary layer depth at some sites, diminishing in
summer when the boundary layer is deepest. Boundary layer equilibrium
concepts predict an inverse proportionality between CO2 vertical
gradients and vertical mixing strength, such that previously reported
discrepancies between observations and models most likely reflect
overestimated as opposed to underestimated vertical mixing. However, errors
in seasonal concentration gradients can also result from errors in modeled
surface fluxes. This study proposes using the timescale for approach to
boundary layer equilibrium to diagnose vertical mixing independently of
seasonal surface fluxes, with applications to observations and model
simulations of CO2 or other conserved boundary layer tracers with
surface sources and sinks. Results indicate that frequently cited
discrepancies between observations and inverse estimates do not provide
sufficient proof of systematic errors in atmospheric transport models. Some
previously hypothesized transport model biases, if found and corrected, could
cause inverse estimates to further diverge from carbon inventory estimates of
terrestrial sinks. |
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