From Earth to Exoplanets: HITRAN2024 Molecular Spectroscopic Data

The 2024 edition of the HITRAN database represents a major advancement in the curation and dissemination of molecular spectroscopic data. A major aspect of HITRAN2024 is the expansion of line-by-line spectroscopic parameters. This now encompasses 61 molecules and includes “planetary” gases such as S₂, CH₃ and H₃⁺. These line lists feature improved accuracy and broader spectral coverage compared to HITRAN2020 [1]. Enhancements are especially relevant for interpreting high-resolution observations from state-of-the-art space telescopes such as the James Webb Space Telescope and the Atacama Large Millimeter/submillimeter Array, which require highly accurate spectroscopic data for the remote characterization of planetary atmospheres.

The HITRAN2024 update also marks a dramatic expansion in the absorption cross section dataset. Absorption cross sections for over 260 molecules not previously represented in HITRAN have been added to the database, including many from the Pacific Northwest National Laboratory [2]. These additions have been made possible thanks to a wealth of newly available experimental data and extend the range of temperatures, pressures, broadening gases, and spectral resolutions covered.

Furthermore, new experimental works have also allowed for an update of the collision-induced absorption data in HITRAN, and the inclusion of new collisional pairs. Additionally, a major new component added to the database in HITRAN2024 is the MT_CKD water vapor continuum model. This complements the existing five core areas of the HITRAN database and the data allows for more accurate simulations of water vapor’s contribution to atmospheric opacity. This update is particularly important in climate modeling and remote sensing applications.

The HITRAN2024 edition will be available through the HITRAN website (https://hitran.org) and through the HITRAN Application Programming Interface (HAPI), which supports the expanded dataset. The upcoming publication describing the new edition is in preparation. Overall, HITRAN2024 delivers extensive improvements that reinforce its role as a dependable resource in atmospheric, terrestrial, and astronomical spectroscopic research.

 References
[1] Gordon, I., Rothman, L., Hargreaves, R., Hashemi, R., Karlovets, E., Skinner, F., Conway, E., Hill, C., Kochanov, R., Tan, Y., Wcislo, P., Finenko, A., Nelson, K., Bernath, P., Birk, M., Boudon, V., Campargue, A., Chance, K., Coustenis, A., Drouin, B., Flaud, J., et al. (2022). The HITRAN2020 molecular spectroscopic database. Journal of Quantitative Spectroscopy and Radiative Transfer, 277:107949.
[2] Sharpe, S. W., Johnson, T. J., Sams, R. L., Chu, P. M., Rhoderick, G. C., and Johnson, P. A. (2004). Gas-Phase Databases for Quantitative Infrared Spectroscopy. Applied Spectroscopy, 58(12):1452–1461.