A case study of eddy covariance flux of N2O measured within forest ecosystems: Quality control and flux error analysis
Anno: 2010
Autori: Mammarella I., Werle P., Pihlatie M., Eugster W., Haapanala S., Kiese R., Markkanen T., Rannik Ü., Vesala T.
Affiliazione autori: Department of Physics, University of Helsinki, Finland; Karlsruhe Institute of Technology KIT, Garmisch-Partenkirchen, Germany; ETH Zurich, Switzerland; Finnish Meteorological Institute, Helsinki, Finland
Abstract: 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 > 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.
Giornale/Rivista: BIOGEOSCIENCES
Volume: 7 (2) Da Pagina: 427 A: 440
Parole chiavi: anemometer; carbon dioxide; concentration (composition); data acquisition; eddy covariance; energy flow; error analysis; forest ecosystem; heat flux; nitrous oxide; quality control; spectroscopy; trace gas; variance analysis; wind velocity, FinlandDOI: 10.5194/bg-7-427-2010Citazioni: 39dati da “WEB OF SCIENCE” (of Thomson Reuters) aggiornati al: 2024-05-12Riferimenti tratti da Isi Web of Knowledge: (solo abbonati) Link per visualizzare la scheda su IsiWeb: Clicca quiLink per visualizzare la citazioni su IsiWeb: Clicca qui