Eddy flux measurements of methane over the fen Murnauer Moos, 11 degrees 11 ' E, 47 degrees 39 ' N, using a fast tunable diode laser spectrometer

Eddy covariance measurements of methane were carried out over the fen Murnauer Moos in the south of Germany in order to evaluate the performance of a newly developed eddy covariance measurement system, based on a frequency-modulated tunable diode laser spectrometer as a fast chemical sensor. During a six-day period, an average daytime methane emission of (5.4 +/- 1.8) mg CH4 m(-2) h(-1) was measured. We find this value moderate, considering the favorable meteorological and soil conditions for methane emission. Diurnal cycles of the fluxes of methane and carbon dioxide as well as of sensible and latent heat are presented. Results are discussed in terms of relevant micrometeorological quantities, and quality control procedures based on Allan variance and spectral analysis are discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.