Recent Advances in HITEMP and HITRAN for Planetary Research

The HITRAN database [1] is a compilation of accurate molecular spectroscopic parameters and data that can be used to model atmospheric radiative transfer. The traditional focus of the database has been toward terrestrial applications, but recently an extensive program has been undertaken to expand the available molecular parameters for application to planetary atmospheres. Such endeavors include the addition of broadening half-widths of relevance to the gas giants (H₂, He), Mars and Venus (CO₂), and steamy exoplanetary atmospheres (H₂O) [2]. Besides the high resolution transitions represented in the main section of the database, the number of available absorption cross sections has also been significantly increased and now accounts for more than 320 species over a broader range of temperatures, with the addition of H₂-, He- and N₂-broadened hydrocarbon cross sections also being included in time for the release of HITRAN2020. Furthermore, the collision-induced absorption data has been expanded with many collisional systems being added or extended.

The high temperatures observed for some exoplanets and brown dwarfs significantly increase the number of lines required to model their atmospheres. The HITEMP database [3] has, therefore, been established for studying high-temperature environments. The increase in the amount of theoretical and laboratory studies in recent years has facilitated a large-scale update to the HITEMP2010 data. The most recent addition to HITEMP has been CH₄ [4], which is of particular significance for exoplanetary research, and has extended the HITEMP database to eight molecules.

This talk will highlight these developments of the HITRAN and HITEMP databases, which are of particular relevance to planetary research. It will also outline appropriate new additions to be expected in HITRAN2020.

[1] Gordon et al. (2017), JQSRT 203, 3.

[2] Tan et al. (2019), JGR-Atmos. 124, 11580.

[3] Rothman et al. (2010), JQSRT 111, 2139.

[4] Hargreaves et al. (2020), ApJS 247, 55.