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| Titel |
Assessing filtering of mountaintop CO2 mole fractions for application to inverse models of biosphere-atmosphere carbon exchange |
| VerfasserIn |
B.-G. J. Brooks, A. R. Desai, B. B. Stephens, D. R. Bowling, S. P. Burns, A. S. Watt, S. L. Heck, C. Sweeney |
| 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 ; 12, no. 4 ; Nr. 12, no. 4 (2012-02-22), S.2099-2115 |
| Datensatznummer |
250010742
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| Publikation (Nr.) |
 copernicus.org/acp-12-2099-2012.pdf |
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| Zusammenfassung |
| There is a widely recognized need to improve our understanding of
biosphere-atmosphere carbon exchanges in areas of complex terrain
including the United States Mountain West. CO2 fluxes over mountainous
terrain are often difficult to measure due to unusual and complicated
influences associated with atmospheric transport.
Consequently, deriving regional fluxes in mountain regions with carbon cycle
inversion of atmospheric CO2 mole fraction is sensitive to filtering
of observations to those that can be represented at the transport model
resolution. Using five years of CO2 mole fraction observations from
the Regional
Atmospheric Continuous CO2 Network in the Rocky Mountains (Rocky
RACCOON), five statistical filters are used to investigate
a range of approaches for identifying regionally representative CO2
mole fractions. Test results from three filters indicate that subsets
based on short-term variance and local CO2 gradients across tower
inlet heights retain nine-tenths of the total observations and are able
to define representative diel variability and seasonal cycles even
for difficult-to-model sites where the influence of local fluxes is much
larger than regional mole fraction variations. Test results from two
other filters that consider measurements from previous and following
days using spline fitting or sliding windows are overly selective. Case
study examples showed that these windowing-filters rejected
measurements representing synoptic changes in CO2, which
suggests that they are not well suited to filtering continental
CO2 measurements. We present a novel CO2 lapse
rate filter that uses CO2 differences between levels in
the model atmosphere to select subsets of site measurements
that are representative on model scales. Our new filtering techniques provide
guidance for novel approaches to assimilating mountain-top CO2 mole
fractions in carbon cycle inverse models. |
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