Comparing laser-based open- and closed-path gas analyzers to measure methane fluxes using the eddy covariance method

Publication year: 2011
Source: Agricultural and Forest Meteorology, In Press, Corrected Proof, Available online 14 June 2011

Matteo, Detto , Joseph, Verfaillie , Frank, Anderson , Liukang, Xu , Dennis, Baldocchi

Closed- and open-path methane gas analyzers are used in eddy covariance systems to compare three potential methane emitting ecosystems in the Sacramento-San Joaquin Delta (CA, USA): a rice field, a peatland pasture and a restored wetland. The study points out similarities and differences of the systems in field experiments and data processing. The closed-path system, despite a less intrusive placement with the sonic anemometer, required more care and power. In contrast, the open-path system appears more versatile for a remote and unattended experimental site. Overall, the two systems have comparable minimum detectable limits, but synchronization between wind speed and methane…

 Highlights: ► We compare methane closed- and open-path analyzers for eddy covariance. ► We examine the role of synchronization, air density adjustment and spectral loss. ► The closed path suffers of spectral losses, especially if an undersize pump is used. ► The open-path is versatile for unattended sites, air density corrections are greater. ► Both systems has similar minimum detectable limit, comparison reveals great scatter.