L. R. Brown

Methane and its isotopes: Current status and prospects for improvement

Abstract The compilations of molecular line parameters of methane are continually being updated and improved. In the present article, numerous changes made for the 1991 and 1992 versions of the HITRAN database in the 0–6185 cm-1 region are described. An assessment of the deficiencies in the parameters is also given.

THE GEISA SYSTEM IN 1996 : TOWARDS AN OPERATIONAL TOOL FOR THE SECOND GENERATION VERTICAL SOUNDERS RADIANCE SIMULATION

Abstract Since their creation, in 1974, the GEISA (Gestion et Etude des Informations Spectroscopiques Atmospheriques: Management and Study of Atmospheric Spectroscopic Information) database system (more than 730 000 entries between 0 and 22 656 cm−1, corresponding to 40 molecules and 86 isotopic species, in its 1992 edition) and the associated software have been widely used for forward atmospheric radiative transfer modelling, with the maximum reliability, tractability and efficiency. For the upcoming high spectral resolution sounders like IASI (Infrared Atmospheric Sounding Interferometer) and AIRS (Atmospheric InfraRed Sounder), more complete and accurate laboratory measurements of spectroscopic parameters, presently included in the databases, are required, and more sophisticated theoretical radiative transfer modelling should be developed. Consequently, it is intended to elaborate the GEISA database as an interactive tool, named GEISA/IASI, designed for providing spectroscopic information tailored to the IASI sounding radiative transfer modelling.

Line Mixing in Water Vapor and Methane

A multispectrum fitting algorithm has been used to identify line mixing and determine mixing parameters for infrared transitions of H2O and CH4 in the 5–9 μm region. Line mixing parameters at room temperature were determined for two pairs of transitions in the v2 fundamental band of H216O, for self‐broadening and for broadening by H2, He, CO2, N2, O2 and air. Line mixing parameters have been determined from air‐broadened CH4 spectra, recorded at temperatures between 210 K and 314 K, in selected R‐branch manifolds of the v4 band. For both H2O and CH4, the inclusion of line mixing was seen to have a greater effect on the retrieved values of the line shifts than on the retrieved values of other parameters.

Spectral Line Parameters for the ν9 Band of Ethane

Ethane is a prominent contributor to the spectrum of Titan, particularly in the region of the ν9 band at 12 μm. A multispectrum nonlinear least squares fitting program was applied to laboratory spectra of ethane to measure accurate positions, absolute intensities, N2‐ and self‐broadened half‐width coefficients and their temperature dependences for a large number transitions. These measurements include several pQ and rQ sub‐bands (and other sub‐bands such as pP, rR) in the ν9 fundamental band of 12C2H6 centered near 822 cm−1. Positions and intensities were measured for 3771 transitions. N2‐ and self‐broadened half‐width coefficients were determined for over 1700 transitions while temperature dependence exponents were retrieved for over 1350 of those transitions. Of these, many measurements (mostly line positions and intensities) belong to the 12C2H6ν9+ν4−ν4 and the ν9+2ν4−2ν4 hot bands, 13C12CH6 ν9 band and unidentified transitions. Forty‐three high resolution (0.0016–0.005 cm−1) infrared laboratory absorp...

TEMPERATURE DEPENDENCE OF AIR-BROADENED HALF WIDTH AND PRESSURE SHIFT COEFFICIENTS IN THE 30012 - 00001 BAND OF

Author Institution: Department of Physics, College of William and Mary, Box 8795, Williamsburg, VA 23187-8795, USA; Department of Physics, University of Lethbridge, 4401 University Drive, Lethbridge, AB T1K 3M4 Canada; Steacie Institute for Molecular Sciences, National Research Council of Canada, Ottawa, ON K1A 0R6 Canada; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA