Abstract

A high-frequency-modulation spectrometer with a lead-salt diode laser operating in the ν ₄ band of CH₄ at 7.8 µm was used as a fast chemical sensor to measure ambient methane concentrations of 2 ppmv (parts in 10⁶ volume-mixing ratio) with a time resolution of 10 Hz for micrometeorological flux measurements. To assess the quality of the data on methane emissions from rice paddy fields, we compared eddy-correlation measurements with simultaneously recorded emission data from the state-of-the-art closed-chamber technique and showed that the closed-chamber measurements were 60%–90% higher than were the eddy-correlation measurements during the campaign. This outcome demonstrates that diode-laser spectroscopy is a valuable tool for quality assurance.

© 2001 Optical Society of America

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