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

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.