A Closed-Path Methane and Water Vapor Gas Analyzer

A closed-path, methane and water vapor gas analyzer is required to support the widespread deployment that is needed to achieve a better understanding of the global methane budget and to quantify exchanges between the atmosphere and terrestrial biosphere. The analyzer must be robust, portable, consistent with solar powered applications, and suitable for long-term and remote field measurements. In addition, it must have low power consumption and use room-temperature lasers. Building on a previously-developed open-path methane analyzer, this project will develop a tunable diode, laser-based, closed-path CH4 and H2O gas analyzer. Based on two recently-developed laser technologies ¿ vertical cavity surface emitting lasers (VCSEL) and wavelength modulation spectroscopy (WMS) ¿ the instrument will provide better spectral performance, lower power consumption, high sensitivity, and less susceptibility to mirror contamination than cavity ring-down spectroscopy (CRDS). Commercial Applications and other Benefits as described by the awardee: The closed-path CH4 and H2O gas analyzer should enable measurements of atmospheric methane concentration that can be made year-round with minimum maintenance and with power from solar panels and batteries. The analyzer also could find use in the measurement of chamber-based soil methane flux and net ecosystem methane exchange.