New Planetary-Relevant Broadening Data in HITRAN2020: Test Case for Generating Opacities under Venusian and Jovian Conditions

The HITRAN2020 edition includes newly added or updated planetary broadening parameters applicable to modeling and interpreting spectra of planetary and exoplanetary atmospheres [1]. These new parameters include broadening due to ambient pressure of H₂O [2], He, H₂, and CO₂ [3]. Planetary broadeners were first added to the database during the HITRAN2016 edition for the line lists of; SO₂, NH₃, HF, HCl, OCS, and C₂H₂ [4]. Since then, He, H₂, and CO₂ broadening parameters, as well as their temperature dependencies, and in some cases, pressure-induced shifts have been added and/or updated for the line lists of; CO₂, N₂O, CO, SO₂, OH, OCS, H₂CO, HCN, PH₃, H₂S, and GeH₄ [3]. By using these planetary broadeners, in conjunction with the HITRAN Application Programming Interface (HAPI) [5], a reliable planetary reference opacity can be calculated. As a test case, this work investigates how the HITRAN broadening data can be used to model spectra under Jovian and Venusian conditions, with resultant opacities compared to available laboratory data [6–9]. Specifically, opacities of NH₃ broadened by H₂, He, and H₂O are tested against laboratory data that are utilized by the Juno mission to retrieve atmospheric molecular constituents of Jupiter [10, 11]. In addition, due to the recent tentative detection of PH₃ on Venus [12] and subsequent studies regarding correlation of the signal with lines of SO₂ [13, 14], the opacities of PH₃ and SO₂ under Venusian conditions are also modeled. Overall, this work demonstrates how HITRAN and HAPI along with the newly included planetary broadeners can be utilized to generate opacities under diverse planetary conditions.

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