XVIth Symposium on High Resolution Molecular Spectroscopy (HighRus-2009)
In a previous series of papers, a model for the calculation of CO2-air absorption coefficients taking line-mixing into account and the corresponding database/software package were described and widely tested. In this study, we present an update of this package, based on the 2008 version of HITRAN, the latest currently available. The spectroscopic data for the seven most-abundant isotopologues are taken from HITRAN. When the HITRAN data are not complete up to J″=70, the data files are augmented with spectroscopic parameters from the CDSD-296 database and the high-temperature CDSD-1000 if necessary. Previously missing spectroscopic parameters, the air-induced pressure shifts and CO2 line broadening coefficients with H2O, have been added. The quality of this new database is demonstrated by comparisons of calculated absorptions and measurements using CO2 high-pressure laboratory spectra in the 1.5–2.3 μm region. The influence of the imperfections and inaccuracies of the spectroscopic parameters from the 2000 version of HITRAN is clearly shown as a big improvement of the residuals is observed by using the new database. The very good agreements between calculated and measured absorption coefficients confirm the necessity of the update presented here and further demonstrate the importance of line-mixing effects, especially for the high pressures investigated here. The application of the updated database/software package to atmospheric spectra should result in an increased accuracy in the retrieval of CO2 atmospheric amounts. This opens improved perspectives for the space-borne detection of carbon dioxide sources and sinks.
Measured absorption coefficients (bottom) and associated square density normalized values (top) for pure CO2 at 295.15K and seven total pressures from 15 to 44atm:
(b) Dens normalized Abs (10-6 cm-1/atm2) and
(a) Abs Coeff (10-2 cm-1).
