Infrared collision-induced absorption by N_2 near 43 μm for atmospheric applications: measurements and empirical modeling

Abstract

Accurate measurements of collision-induced absorption by pure nitrogen in the fundamental band near 4.3 μm have been made in the 0-10 atm and 230-300 K pressure and temperature ranges, respectively. A Fourier-transform spectrometer was used with a resolution of 0.5 cm(-1). The current measurements, which agree well with previous ones but are more precise, reveal that weak features are superimposed on the broad N(2) continuum. These features have negligible temperature dependence, and their origin is not clear at the present time. Available experimental data in the 190-300 K temperature range have been used to build a simple empirical model that is suitable for use to compute atmospheric N(2) absorption. Tests indicate that this model is accurate unlike the estimates produced by widely used atmospheric transmission codes.

The natural greenhouse effect of atmospheric oxygen (O2) and nitrogen (N2)

“…The collision induced continuum by O 2 is based on the empirical model by Thibault et al [1997]. The continuum by N 2 near 2300 cm À1 is calculated according to Lafferty et al [1996]. The collision induced rototranslational absorption by N 2 at around 100 cm À1 is taken from the MT_CKD version 2.5.2 implementation which is based on Borysow and Frommhold [1986] and Boissoles et al [2003].…”

Technical Note: An assessment of the accuracy of the RTTOV fast radiative transfer model using IASI data

“…Regarding the UMBC-LBL model it should be stressed that it relies on a full treatment of the CO 2 Qand P/R-branch line mixing and does not use the perturbation theory. Finally, the collision-induced bands of oxygen at 1600 cm −1 and nitrogen at 2350 cm −1 are incorporated using the model by Thibault et al (1997) and Lafferty et al (1996) respectively.…”

“…To describe the effects of pressure and Doppler line broadening the Voigt line shape is used at all atmospheric levels with an algorithm based on a linear combination of approximating functions. LBLRTM incorporates version 2.0 of the water vapor continuum model MT CKD (hence after referred to as MT CKD v2.0) and the collision-induced bands of oxygen at 1600 cm −1 and nitrogen at 2350 cm −1 are included as broad-band continuum contributions to the absorption using the models by Thibault et al (1997) and Lafferty et al (1996) respectively. In LBLRTM the CO 2 line shape includes the effects of line mixing for the P-R-branch and Q-branch in the υ2-region and υ3-region using first order line coupling parameters generated using the code by Niro et al, 2005. Since the model by Niro et al (2005) combines the effects of line mixing and duration of collision effects, the χ factor is set equal to 1.…”

Characterization of potentially habitable planets: Retrieval of atmospheric and planetary properties from emission spectra

“…To obtain diskintegrated emission spectra, the radiance spectra were multiplied by π. For the purpose of this work, collision-induced selfcontinua of CO 2 (Wordsworth et al 2010) and N 2 (Borysow & Frommhold 1986;Lafferty et al 1996) have been included.…”