33 search hits
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Whole-air relaxed eddy accumulation for the measurement of isotope and trace-gas fluxes
(2012)
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Johannes Ruppert
Michael Riederer
Willi A. Brand
Thomas Foken
- Measuring the isotopic composition of trace gas fluxes can provide additional information on ecosystem gas exchange, when ecosystem processes, like assimilation, discriminate against heavier isotopes. In the case of CO2 exchange, different mass-balances for bulk CO2 and its 13CO2 or CO18O isotopes can be used to separate respiration from photosynthetic assimilation. Up to now, detectors for direct isotope measurements in the field lack the precision needed for fast eddy covariance (EC) flux measurements. The collection of updraft and downdraft whole-air samples using the relaxed eddy accumulation technique (REA) allows simultaneously determining trace gas concentrations and isotope ratios by high precision laboratory analysis. At the same time whole-air REA relaxes several of the technical problems related to REA sampling on traps. In tests using air from a tank the complete whole-air REA sampling system and its foil balloon bag reservoirs showed no signs of contamination after cleaning. The standard deviations of δ13C and δ18O isotope ratios were only slightly higher than the precision specified for the laboratory analysis procedure. First experiment results showed that isotopic differences (up-drafts−downdrafts) were large enough to yield signal to noise ratios greater than five when applying hyperbolic deadbands during REA sampling (HREA). The performance of the instrument and the HREA sampling method are investigated by simulation of the sampling process for bulk CO2, which serves as proxy scalar. Measurements by whole-air HREA in combination with high precision isotope analysis can quantify the isofluxes of 13CO2 and CO18O. Furthermore, additional information is collected on the scalar correlation of bulk CO2 and its stable isotopes, which represents the relatively short timescale of updrafts and downdrafts in the turbulent exchange above an ecosystem. This information is essential to check the scalar similarity assumptions made in the HREA and EC/flask method for the quan-tification of isofluxes.
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The OP-2 open path infrared gas analyser for CO2 and H2O
(2005)
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Gesa M. Herold
Christoph Thomas
Thomas Foken
- no abstract
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Strukturanalyse der atmosphärischen Turbulenz mittels Wavelet-Verfahren zur Bestimmung von Austauschprozessen über dem antarktischen Schelfeis
(1999)
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Georg Heinz
Dörte Handorf
Thomas Foken
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Qualitätsbegutachtung komplexer mikrometeorologischer Messstationen im Rahmen des VERTIKO projects
(2004)
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Matthias Göckede
Matthias Mauder
Thomas Foken
- keine Zusammenfassung
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Proceedings of the International Conference of "Atmospheric Transport and chemistry in Forest Ecosystems" Castle of Thurnau, Germany Oct 5 to Oct 8, 2009
(2009)
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Johannes Lüers
Thomas Foken
- no abstract
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Nachtfrostgefährdung im Ökologisch-Botanischen Garten
(1999)
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Thomas Foken
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Methode zur Bestimmung der trockenen Deposition von Bor
(1999)
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Thomas Foken
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Mesoscale Circulations and Energy and GaS Exchange Over the Tibetan Plateau Documentation of the Micrometeorological Experiment, Nam Tso, Tibet
(2009)
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Tobias Biermann
Wolfgang Babel
Johannes Olesch
Thomas Foken
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Lufthygienisch-Bioklimatische Kennzeichnung des oberen Egertales - Abschlussbericht des Projektes 111450 des Bayerischen Staatsministeriums für Landesentwicklung und Umweltfragen
(2001)
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Thomas Foken
- keine Zusammenfassung
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Lufthygienisch-Bioklimatische Kennzeichnung des oberen Egertales
(1999)
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Thomas Foken
