Open-path and closed-path designs of the high speed CO2/H2O gas analyzers are well-established and widely used to measure concentrations and fluxes of carbon dioxide and water vapor. Both designs have their advantages and deficiencies.
Open-path analyzers have excellent frequency response, long-term stability, and low sensitivity to window contamination. They are pump-free and require infrequent calibrations. Yet they are susceptible to data loss during precipitation and icing-over, and may need instrument surface heat flux correction when used in cold conditions.
Closed-path analyzers can collect data during precipitation, can be climate-controlled, and are not susceptible to surface heating issues. Yet they experience significant frequency loss in long intake tubes, which is especially problematic when computing water vapor fluxes. They may require frequent calibrations and need a powerful pump.
Here we present preliminary data from a third kind of design: a compact enclosed analyzer enabled for operation with short intake tube, intended to maximize strengths and to minimize weaknesses of both traditional open-path and closed-path designs.
Results/Conclusions
The new gas analyzer has a number of advantages over open-path analyzers. Similar to the closed-path analyzers, it has minimal data loss during precipitation events and icing, it does not have surface heating issues, and it has improved water measurement specifications.
The new gas analyzer also has a number of advantages over traditional closed-path analyzers. It has good frequency response (close to that of open-path analyzers) due to small and easily correctable flux attenuation loss in the short intake tube. Similar to open-path analyzers, the new analyzer does not need frequent calibration, has minimal maintenance requirements, and can be used in low power configuration with the short intake tube and flow controller. It is also small, light-weight and weather-proof, making it convenient for use on remote flux towers.
