The CO₂–broadened H₂O continuum in the 100–1500cm-1 region: Measurements, predictions and empirical model

Abstract

Transmission spectra of H₂O+CO₂ mixtures have been recorded, at 296, 325 and 366 K, for various pressures and mixture compositions using two experimental setups. Their analysis enables to retrieve values of the “continuum” absorption by the CO₂-broadened H2₂O line wings between 100 and 1500 cm-1. The results are in good agreement with those, around 1300 cm-1, of the single previous experimental study available. Comparisons are also made with direct predictions based on line-shape correction factors χ calculated, almost thirty years ago, using a quasistatic approach and an input H₂O—CO₂ intermolecular potential. They show that this model quite nicely predicts, with slightly overestimated values, the continuum over a spectral range where it varies by more than three orders of magnitude. An empirical correction is proposed, based on the experimental data, which should be useful for radiative transfer and climate studies in CO2 rich planetary atmospheres