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| Titel |
Intercomparison of six fast-response sensors for the eddy-covariance flux measurement of nitrous oxide over agricultural grassland |
| VerfasserIn |
Eiko Nemitz, Daniela Famulari, Andreas Ibrom, Alex Vermeulen, Arjan Hensen, Pim van den Bulk, Benjamin Loubet, Patricia Laville, Ivan Mammarella, Sami Haapanala, Annalea Lohila, Tuomas Laurila, Eva Rabot, Marie Laborde, Nicholas Cowan, Margaret Anderson, Carole Helfter |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250107523
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| Publikation (Nr.) |
 EGU/EGU2015-7226.pdf |
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| Zusammenfassung |
| Nitrous oxide (N2O) is the third most important greenhouse gas and its terrestrial budget
remains poorly constraint, with bottom up and top down estimates of country emissions often
disagreeing by more than a factor of two.
Whilst the measurements of the biosphere / atmosphere exchange of CO2 with
micrometeorological methods is commonplace, emissions of CH4 and N2O are more
commonly measured with enclosure techniques due to limitations in fast-response sensors
with good signal-to-noise characteristics.
Recent years have seen the development of a range of instruments based on optical
spectroscopy. This started in the early 1990s with instruments based on lead salt lasers, which
had temperamental long-term characteristics. More recent developments in quantum cascade
lasers has lead to increasingly stable instruments, initially based on pulsed, later on
continuous wave lasers.
Within the context of the European FP7 Infrastructure Project InGOS (“Integrated
non-CO2 Greenhouse gas Observing System”), we conducted an intercomparison of six fast
response sensors for N2O: three more or less identical instruments based on off-axis
Integrated Cavity Optical Spectrocopy (ICOS) (Los Gatos Research Inc.) and three
instruments based on quantum cascade laser absorption spectrometry (Aerodyne
Research Inc.): one older generation pulsed instrument (p-QCL) and two of the latest
generation of compact continuous wave instruments (cw-QCL), operating at two
different wavelengths. One of the ICOS instruments was operated with an inlet
drier.
In addition, the campaign was joined by a relaxed eddy-accumulation system linked to a
FTIR spectrometer (Ecotech), a gradient system based on a home-built slower QCL (INRA
Orleans) and a fast chamber system.
Here we present the results of the study and a detailed examination of the various
corrections and errors of the different instruments. Overall, with the exception of the older
generation QCL, the average fluxes based on the different fast-response instruments agreed
within +/- 7.4%, although fluxes were moderate. The cw-QCL systems showed somewhat
better signal-to-noise characteristics and a lower flux detection limit than the ICOS
analysers. Intriguingly, there seemed to be some minor differences between the
ICOS instruments which showed cross sensitivities to CO to varying degree. Overall
the study demonstrates, that, while not cheap, both the ICOS-based instruments
and the cw-QCLs are suitable for the measurement of even moderate N2O fluxes. |
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