Menu

Javascript is not activated in your browser. This website needs javascript activated to work properly.
You are here

Evaluating the performance of commonly used gas analysers for methane eddy covariance flux measurements: the InGOS inter-comparison field experiment

Author:
  • O. Peltola
  • A. Hensen
  • C. Helfter
  • L. Belelli Marchesini
  • F. C. Bosveld
  • W. C. M. van den Bulk
  • J. A. Elbers
  • S. Haapanala
  • Jutta Holst
  • T. Laurila
  • Anders Lindroth
  • E. Nemitz
  • T. Rockmann
  • A. T. Vermeulen
  • I. Mammarella
Publishing year: 2014
Language: English
Pages: 3163-3186
Publication/Series: Biogeosciences
Volume: 11
Issue: 12
Document type: Journal article
Publisher: Copernicus Publications

Abstract english

The performance of eight fast-response methane (CH4) gas analysers suitable for eddy covariance flux measurements were tested at a grassland site near the Cabauw tall tower (Netherlands) during June 2012. The instruments were positioned close to each other in order to minimise the effect of varying turbulent conditions. The moderate CH4 fluxes observed at the location, of the order of 25 nmol m(-2) s(-1), provided a suitable signal for testing the instruments' performance. Generally, all analysers tested were able to quantify the concentration fluctuations at the frequency range relevant for turbulent exchange and were able to deliver high-quality data. The tested cavity ringdown spectrometer (CRDS) instruments from Picarro, models G2311-f and G1301-f, were superior to other CH4 analysers with respect to instrumental noise. As an open-path instrument susceptible to the effects of rain, the LI-COR LI-7700 achieved lower data coverage and also required larger density corrections; however, the system is especially useful for remote sites that are restricted in power availability. In this study the open-path LI-7700 results were compromised due to a data acquisition problem in our data-logging setup. Some of the older closed-path analysers tested do not measure H2O concentrations alongside CH4 (i.e. FMA1 and DLT-100 by Los Gatos Research) and this complicates data processing since the required corrections for dilution and spectroscopic interactions have to be based on external information. To overcome this issue, we used H2O mole fractions measured by other gas analysers, adjusted them with different methods and then applied them to correct the CH4 fluxes. Following this procedure we estimated a bias of the order of 0.1 g (CH4) m(-2) (8% of the measured mean flux) in the processed and corrected CH4 fluxes on a monthly scale due to missing H2O concentration measurements. Finally, cumulative CH4 fluxes over 14 days from three closed-path gas analysers, G2311-f (Picarro Inc.), FGGA (Los Gatos Research) and FMA2 (Los Gatos Research), which were measuring H2O concentrations in addition to CH4, agreed within 3% (355-367 mg (CH4) m(-2)) and were not clearly different from each other, whereas the other instruments derived total fluxes which showed small but distinct differences (+/- 10 %, 330-399 mg (CH4) m(-2)).

Keywords

  • Physical Geography

Other

Published
  • ISSN: 1726-4189
E-mail: jutta [dot] holst [at] nateko [dot] lu [dot] se

Researcher

Dept of Physical Geography and Ecosystem Science

+46 46 222 40 39

+46 72 254 72 00

445

16

Research secretary

ICOS Sweden

16

Researcher

ICOS Sweden

+46 46 222 40 39

+46 72 254 72 00

444a

Sölvegatan 12, Lund

16

Department of Physical Geography and Ecosystem Science
Lund University
Sölvegatan 12
S-223 62 Lund
Sweden

Processing of personal data