Recent world-wide attention to greenhouse gases is spawning a new wave of instrument development intended for flux measurements, not only for CO₂ and water vapor, but for methane as well. We report on recent field work conducted with a new, second-generation closed-path analyzer, based on cavity ring-down spectroscopy (CRDS), that simultaneously provides eddy covariance measurements of carbon dioxide and methane, both at a 10-Hz data rate. Field testing of an initial prototype analyzer had previously been conduced, and recommendations for design enhancements generated during that round of testing have been subsequently implemented in the new analyzer.

Results/Conclusions

Both field testing campaigns were conducted at Oregon State University where the analyzer was compared to an AmeriFlux Portable Eddy Covariance System for measuring CO₂ fluxes using conventional infrared open- and closed path CO₂ and water vapor analyzers. Data comparing the performance of the new CRDS-based analyzer against the currently-used AmeriFlux instrumentation is presented. The new analyzer has the ability to conduct both high-speed flux measurements as well as long-term background concentration measurements, owing to its long-term stability. The stability of the analyzer also reduces or eliminates the need for frequent calibration and the linearity of the analyzer allows calibrations, when they are needed, to be conducted with only two gas standards. Further, the ability to measure two greenhouse gases in the same instrument will enable more cost-effective expansion of AmeriFlux sites to include both CO₂ and methane measurements.