Revising the line-shape parameters for air- and self-broadened CO2 lines toward a sub-percent accuracy level

• Published in: Journal of quantitative spectroscopy & radiative transfer 2020-11, Vol.256, p.107283, Article 107283
• Main Authors: Hashemi, Robab, Gordon, Iouli E., Tran, Ha, Kochanov, Roman V., Karlovets, Ekaterina V., Tan, Yan, Lamouroux, Julien, Ngo, Ngoc Hoa, Rothman, Laurence S.
• Format: Article
• Language: English
• Subjects: Air- and self-broadening; CO2; First-order line-mixing; Full line-mixing; HITRAN database; Line-shape parameters; Padé approximants; Physics; Sciences of the Universe; Speed dependence of width
• ISSN: 0022-4073; 1879-1352
• DOI: 10.1016/j.jqsrt.2020.107283

•Best determined line-shape parameters are collected for self- and air-broadened CO2 lines, and by creating sets of semi-empirical models, all the CO2 transitions in the HITRAN are updated using the Voigt and non-Voigt parametrizations.•A semi-empirical approach was examined for calculating the line shifts of air- and CO2 broadened CO2 lines, yielding reliable pressure shift values.•The CO2 line mixing package is updated and the first-order line-mixing parameters will be added for every transition in the HITRAN to be used for the bands with the P and R branches.•Significant improvement in the residuals was achieved when validating the updated parameters with laboratory spectra. Characterizing and modeling atmospheric CO2 with a sub-percent accuracy necessitates high-quality spectroscopic line-shape parameters. For this goal, we collected the best experimentally and theoretically determined parameters for self- and air-broadened CO2 lines to create sets of semi-empirical models for updating all of the carbon dioxide transitions in the HITRAN database using the Voigt and non-Voigt parametrizations. Based on the available data, we estimated the air- and CO2-broadening half widths, their associated temperature exponents, and the speed dependence of the broadening together with its temperature dependence for every transition in HITRAN. Furthermore, a semi-empirical approach educated by the most reliable experimental data was used to calculate the line shifts of air- and self-broadened CO2 absorption lines. The updated line-shape parameters were used for calculating the first-order line-mixing parameters for every transition using the program developed by Lamouroux et al. [JQSRT 151, 88 (2015)]. The same program was used to calculate absorption coefficients with full line-mixing by using the updated parameters. In order to verify these new data, two different sets of laboratory spectra were used to compare with the absorption coefficient calculated by the line-mixing package program and the HITRAN Application Programming Interface (HAPI) for which necessary functionality was implemented. The updated data is proposed for the next edition of HITRAN (2020). Thanks to the relational structure of the HITRAN database, we are able to provide separate consistent and complete sets of parameters in Voigt and speed-dependent Voigt parametrizations for every line of carbon dioxide.