AtmosphericAbsorption.jl

Clean-slate, GPU-accelerated molecular absorption cross-sections for atmospheric radiative transfer — a standalone successor to vSmartMOM's Absorption module.

Goals

• Pluggable line-list sources behind one interface: HITRAN, ExoMol, … (the "Port" hierarchy).
• Advanced line shapes: Voigt → speed-dependent Voigt → Hartmann-Tran, plus line mixing.
• Water-vapor continuum (MT_CKD) and CIA.
• One KernelAbstractions compute core running on CPU, CUDA, and Metal.
• Type-stable and correct in both Float32 and Float64 to machine precision.
• Validated against hapi2 as a golden-file benchmark.

Status

Implemented:

• Core — Architectures, TOML-defined Constants, columnar LineDatabase, the Port interface, and one KernelAbstractions compute core with CUDA/Metal extensions.
• HITRAN — .par parser and direct download (HitranPort, load_hitran), authenticated non-Voigt parameters (load_hitran_nonvoigt), and tabulated .xsc cross-sections. Voigt validated to <5×10⁻³ of HAPI on real CO2/H2O; ~10× faster than HAPI on CPU and ~1900× on an A100 GPU (see benchmark/).
• ExoMol — ExoMolPort, with line strengths derived from Einstein-A coefficients and the ExoMol partition function.
• Line shapes — Doppler, Lorentz, Voigt, speed-dependent Voigt, Rautian and Hartmann-Tran (HAPI's pcqsdhc, matched to ~1e-6), plus first-order (Rosenkranz) line mixing.
• Partition functions — TIPS-2021 (default), TIPS-2017, and tabulated ExoMol .pf.
• Continuum — MT_CKD water-vapor continuum and HITRAN CIA.
• Lookup tables — interpolated cross-section models, AER ABSCO tables (including GPU-native OCO-2 LUTs), and batched profile queries (compute_cross_section_profile).
• vSmartMOM — vSmartMOM.jl builds its absorption models with this package; its legacy Absorption module has not been retired yet.

See the documentation for details.

HITRAN API key (for non-Voigt parameters)

Standard HITRAN line data and ExoMol downloads need no credentials. Fetching HITRAN non-Voigt parameters (Hartmann-Tran / speed-dependent / line-mixing) uses the authenticated HITRANonline API and requires your own key from your profile at https://hitran.org. Supply it in-memory (never stored on disk or in this repo):

activate_hitran!("your-key")          # or set the HITRAN_API_KEY environment variable

Citing HITRAN and ExoMol

Line data come from the HITRAN database. If you publish results computed with HITRAN data through this package, please cite the HITRAN edition you used. Direct downloads from hitran.org always return the current edition (HITRAN2024 at the time of writing). The edition keyword is only a cache/provenance label. For local .par files, cite the edition the file came from.

• HITRAN2024: Gordon IE, Rothman LS, Hargreaves RJ, et al. The HITRAN2024 molecular spectroscopic database. J Quant Spectrosc Radiat Transf 2026;353:109807. https://doi.org/10.1016/j.jqsrt.2026.109807
• HITRAN2020: Gordon IE, Rothman LS, Hargreaves RJ, et al. The HITRAN2020 molecular spectroscopic database. J Quant Spectrosc Radiat Transf 2022;277:107949. https://doi.org/10.1016/j.jqsrt.2021.107949
• HITRAN2016: Gordon IE, Rothman LS, Hill C, et al. The HITRAN2016 molecular spectroscopic database. J Quant Spectrosc Radiat Transf 2017;203:3–69. https://doi.org/10.1016/j.jqsrt.2017.06.038

If you use the speed-dependent / Hartmann–Tran profiles (based on HAPI's pcqsdhc) or non-Voigt parameters from the HITRANonline API, please also cite HAPI:

• Kochanov RV, Gordon IE, Rothman LS, Wcisło P, Hill C, Wilzewski JS. HITRAN Application Programming Interface (HAPI): A comprehensive approach to working with spectroscopic data. J Quant Spectrosc Radiat Transf 2016;177:15–30. https://doi.org/10.1016/j.jqsrt.2016.03.005

If you use ExoMol line lists (ExoMolPort), please cite the ExoMol database and the paper for each line list you used. That paper is listed on the line list's page at https://www.exomol.com. ExoMol data are released under CC BY-SA 4.0.

• ExoMol 2024 release: Tennyson J, Yurchenko SN, Zhang J, et al. The 2024 release of the ExoMol database: Molecular line lists for exoplanet and other hot atmospheres. J Quant Spectrosc Radiat Transf 2024;326:109083. https://doi.org/10.1016/j.jqsrt.2024.109083
• ExoMol database and data format: Tennyson J, Yurchenko SN, Al-Refaie AF, et al. The ExoMol database: Molecular line lists for exoplanet and other hot atmospheres. J Mol Spectrosc 2016;327:73–94. https://doi.org/10.1016/j.jms.2016.05.002
• Line list, e.g. CO Li2015: Li G, Gordon IE, Rothman LS, et al. Rovibrational line lists for nine isotopologues of the CO molecule in the X ¹Σ⁺ ground electronic state. Astrophys J Suppl Ser 2015;216:15. https://doi.org/10.1088/0067-0049/216/1/15

The full author lists are in docs/src/citing.md.

Develop

julia --project=. -e 'using Pkg; Pkg.test()'