Precise methane absorption measurements in the 1.64 μm spectral region for the MERLIN mission

• DOI: 10.1002/2016jd025024
• Publication Date: 2016-06-02T07:42:47Z
• Authors: T. Delahaye; S. E. Maxwell; Z. D. Reed; H. Lin; J. T. Hodges; K. Sung; V. M. Devi; T. Warneke; P. Spietz; H. Tran
• Keywords: Spectral resolution; Atmospheric methane

In this article we describe a high-precision laboratory measurement targeting the R(6) manifold of 2ν3 band 12CH4. Accurate physical models absorption spectrum will be required by Franco-German, Methane Remote Sensing LIDAR (MERLIN) space mission for retrievals atmospheric methane. The analysis uses Hartmann-Tran profile modeling line shape and also includes line-mixing effects. To end, six high-resolution high signal-to-noise spectra air-broadened methane were recorded using frequency-stabilized cavity ring-down spectroscopy apparatus. Sample conditions corresponded to room temperature spanned total sample pressures 40 hPa - 1013 with molar fractions between 1 μmol mol-1 12 mol-1. All spectroscopic model parameters simultaneously adjusted in multispectrum nonlinear least-squares fit measured spectra. Comparison fitted reveals ability calculate room-temperature, coefficient better than 0.1% at on-line position MERLIN mission. This is first time that such fidelity has been reached investigated spectral region, fulfilling accuracy requirements We found excellent agreement when comparing present results measurements obtained over different pressure other techniques. Finally, evaluated impact these new on transmissions calculations.