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Abstract
Abstract. Performances of four methane gas analyzers suitable for eddy covariance measurements are assessed. The assessment and comparison was performed by analyzing eddy covariance data obtained during summer 2010 (1 April to 26 October) at a pristine fen, Siikaneva, Southern Finland. High methane fluxes with pronounced seasonality have been measured at this fen. The four participating methane gas analyzers are commercially available closed-path units TGA-100A (Campbell Scientific Inc., USA), RMT-200 (Los Gatos Research, USA), G1301-f (Picarro Inc., USA) and an early prototype open-path unit Prototype-7700 (LI-COR Biosciences, USA). The RMT-200 functioned most reliably throughout the measurement campaign, during low and high flux periods. Methane fluxes from RMT-200 and G1301-f had the smallest random errors and the fluxes agree remarkably well throughout the measurement campaign. Cospectra and power spectra calculated from RMT-200 and G1301-f data agree well with corresponding temperature spectra during a high flux period. None of the gas analyzers showed statistically significant diurnal variation for methane flux. Prototype-7700 functioned only for a short period of time, over one month, in the beginning of the measurement campaign during low flux period, and thus, its overall accuracy and season-long performance were not assessed. The open-path gas analyzer is a practical choice for measurement sites in remote locations due to its low power demand, whereas for G1301-f methane measurements interference from water vapor is straightforward to correct since the instrument measures both gases simultaneously. In any case, if only the performance in this intercomparison is considered, RMT-200 performed the best and is the recommended choice if a new fast response methane gas analyzer is needed.
Highlights
Hydrology and Prior to 1990s, eddy cEovaarriatnhceS(yEsCt)emmeasurements of malyetzhearsnenefleudxedwienreoridmeprotosscibalpetudSrueectutioerblnualcceknetosflfu“xfatsrta”nsgpaosrat na-t all relevant frequencies, or eddy sizes
Methane fluxes from RMT-200 and G1301-f had the smallest random errors and the fluxes agree remarkably well throughout the measurement campaign
After the development of fast instruments based on the laser absorption spectroscopy (LAS), studies reporting ecosystem scale EC
Summary
Hydrology and Prior to 1990s, eddy cEovaarriatnhceS(yEsCt)emmeasurements of malyetzhearsnenefleudxedwienreoridmeprotosscibalpetudSrueectutioerblnualcceknetosflfu“xfatsrta”nsgpaosrat na-t all relevant frequencies, or eddy sizes. After the development of fast instruments based on the laser absorption spectroscopy (LAS), studies reporting ecosystem scale EC methane flux measuremOenctes satanrteSd tcoioecncucremore frequently (e.g., Verma et al, 1992; Suyker et al, 1996; Rinne et al, 2007). The early studies employed instruments which needed continuous maintenance, and whose sampling resolution was not very high. Estimating long-term methane balance was quite expensive and a laborious task due to substantial need of continuous uSpkoeelpid. TEhealarstehrs needed to be cooled to cryogenic temperature in order to function properly, and such cooling was usually done with liquid nitrogen which further increased the maintenance requirements. Recent advancements in the development of LAS gas anacliyalzleyrsavhaaivlaebmlea,daensdeTancshcitoievrdeiCanngrdlyyr,ootbhsuespnt huinmestbrreuermoefngtsascoamnamlyezr--
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