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| Titel |
A case study of eddy covariance flux of N2O measured within forest ecosystems: quality control and flux error analysis |
| VerfasserIn |
I. Mammarella, P. Werle, M. Pihlatie, W. Eugster, S. Haapanala, R. Kiese, T. Markkanen, Ü. Rannik, T. Vesala |
| 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 ; 7, no. 2 ; Nr. 7, no. 2 (2010-02-02), S.427-440 |
| Datensatznummer |
250004480
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| Publikation (Nr.) |
 copernicus.org/bg-7-427-2010.pdf |
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| Zusammenfassung |
| Eddy covariance (EC) flux measurements of nitrous oxide (N2O) obtained
by using a 3-D sonic anemometer and a tunable diode laser gas analyzer for
N2O were investigated. Two datasets (Sorø, Denmark and Kalevansuo,
Finland) from different measurement campaigns including sub-canopy flux
measurements of energy and carbon dioxide are discussed with a focus on
selected quality control aspects and flux error analysis. Although fast
response trace gas analyzers based on spectroscopic techniques are
increasingly used in ecosystem research, their suitability for reliable
estimates of EC fluxes is still limited, and some assumptions have to be
made for filtering and processing data. The N2O concentration signal
was frequently dominated by offset drifts (fringe effect), which can give an
artificial extra contribution to the fluxes when the resulting concentration
fluctuations are correlated with the fluctuations of the vertical wind
velocity. Based on Allan variance analysis of the N2O signal, we found
that a recursive running mean filter with a time constant equal to 50 s was
suitable to damp the influence of the periodic drift.
Although the net N2O fluxes over the whole campaign periods were quite
small at both sites (~5 μg N m−2 h−1 for Kalevansuo and
~10 μg N m−2 h−1 for Sorø), the calculated
sub-canopy EC fluxes were in good agreement with those estimated by
automatic soil chambers. However, EC N2O flux measurements show larger
random uncertainty than the sensible heat fluxes, and classification
according to statistical significance of single flux values indicates that
downward N2O fluxes have larger random error. |
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