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| Titel |
Eddy covariance methane measurements at a Ponderosa pine plantation in California |
| VerfasserIn |
C. J. P. P. Smeets, R. Holzinger, I. Vigano, A. H. Goldstein, T. Röckmann |
| 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 ; 9, no. 21 ; Nr. 9, no. 21 (2009-11-03), S.8365-8375 |
| Datensatznummer |
250007731
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| Publikation (Nr.) |
 copernicus.org/acp-9-8365-2009.pdf |
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| Zusammenfassung |
| Long term methane flux measurements have been mostly performed with plant or
soil enclosure techniques on specific components of an ecosystem. New fast
response methane analyzers make it possible to use the eddy covariance (EC)
technique instead. The EC technique is advantageous because it allows
continuous flux measurements integrating over a larger and more
representative area including the complete ecosystem, and allows fluxes to be
observed as environmental conditions change naturally without disturbance. We
deployed the closed-path Fast Methane analyzer (FMA) from Los Gatos Research
Ltd and demonstrate its performance for EC measurements at a Ponderosa pine
plantation at the Blodgett Forest site in central California. The
fluctuations of the CH4 concentration measured at 10 Hz appear to be small
and their standard deviation is comparable to the magnitude of the signal
noise (±5 ppbv). Consequently, the power spectra typically have a white
noise signature at the high frequency end (a slope of +1). Nevertheless, in
the frequency range important for turbulent exchange, the cospectra of CH4
compare very well with all other scalar cospectra confirming the quality of
the FMA measurements are good for the EC technique. We furthermore evaluate
the complications of combined open and closed-path measurements when applying
the Webb-Pearman-Leuning (WPL) corrections (Webb et al., 1980) and the
consequences of a phase lag between the water vapor and methane signal inside
the closed path system. The results of diurnal variations of CH4
concentrations and fluxes are summarized and compared to the monthly results
of process-based model calculations. |
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