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Suitability of quantum cascade laser spectrometry for CH4 and N2O eddy covariance measurements
1Energy research Centre of the Netherlands (ECN), Department of Air Quality and Climate Change, Netherlands
2TU Delft, Department of Multi-Scale Physics, Research group Clouds, Climate and Air Quality, Netherlands
3Aerodyne Research, Inc., USA
Abstract. A quantum cascade laser spectrometer was evaluated for eddy covariance measurements of CH4 and N2O using laboratory tests and three months of continuous measurements. Moreover, an indication was given of CH4 and N2O exchange. All four required criteria for eddy covariance measurements related to continuity, sampling frequency, precision and stationarity were checked. The system had been running continuously at a dairy farm on peat grassland in the Netherlands from 17 August to 6 November 2006. An automatic liquid nitrogen filling system was employed for unattended operation of the system. A sampling frequency of 10 Hz was obtained using a 1 GHz PC system. A precision of 2.6 and 0.3 ppb Hz−1/2 was obtained for CH4 and N2O, respectively. However, it proved to be important to calibrate the equipment frequently using a low and a high standard. Drift in the system was removed using a 120 s running mean filter. Average fluxes and standard deviations in the averages of 484±375 ngC m−2s−1 (2.32±1.80 mg m−2h−1) and 39±62 ngN m−2s−1 (0.22±0.35 mg m−2h−1) were observed. About 40% of the total N2O emission was due to a fertilizing event.
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Citation: Kroon, P. S., Hensen, A., Jonker, H. J. J., Zahniser, M. S., van 't Veen, W. H., and Vermeulen, A. T.: Suitability of quantum cascade laser spectrometry for CH4 and N2O eddy covariance measurements, Biogeosciences Discuss., 4, 1137-1165, 2007. Bibtex EndNote Reference Manager
