Absorption API

Absorption provides HITRAN line-list reading, line-shape models, interpolation models, and absorption cross-section evaluation.

HITRAN Data Management

vSmartMOM.artifact Function

julia

artifact(molecule::AbstractString, database::AbstractString = "hitran")

Given a molecule name, retrieve the path to its HITRAN line-by-line .par file.

The data source depends on the active HITRAN edition (see set_hitran_edition!):

"artifact" (default): Uses legacy HITRAN 2016 data from Julia Artifacts
Any other edition (e.g., "HITRAN2024"): Uses data downloaded from hitran.org, auto-downloading on first access if not already cached.

Example

julia

# Default: HITRAN 2016 from Artifacts
path = artifact("CO2")

# After switching edition:
set_hitran_edition!("HITRAN2024")
path = artifact("CO2")  # downloads from hitran.org on first call

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vSmartMOM.fetch_hitran Function

julia

fetch_hitran(molecule::AbstractString; numin=0, numax=150000,
                edition="HITRAN2024", force=false)

Download HITRAN line-by-line data for a molecule directly from hitran.org.

Analogous to HAPI's fetch(). Resolves the molecule name to all its isotopologue global IDs and queries the HITRAN API. Data is cached locally; subsequent calls return the cached path unless force=true.

Arguments

molecule: Molecule name (e.g., "CO2", "H2O", "O3")
numin: Lower wavenumber bound in cm⁻¹ (default: 0)
numax: Upper wavenumber bound in cm⁻¹ (default: 150000)
edition: Label for this download (default: "HITRAN2024")
force: Re-download even if cached (default: false)

Returns

Path to the downloaded .par file

Example

julia

path = fetch_hitran("CO2")
path = fetch_hitran("O3"; numin=500, numax=3000, edition="HITRAN2024")

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vSmartMOM.fetch_hitran_by_ids Function

julia

fetch_hitran_by_ids(name::AbstractString, iso_ids::Vector{Int};
                numin=0, numax=150000, edition="HITRAN2024", force=false)

Download HITRAN data using explicit global isotopologue IDs.

Lower-level variant of fetch_hitran for when you need specific isotopologues. Global IDs can be looked up via Absorption.mol_globalID(mol, iso).

Arguments

name: Label for the file (typically molecule name)
iso_ids: Vector of HITRAN global isotopologue IDs
numin, numax, edition, force: Same as fetch_hitran

Returns

Path to the downloaded .par file

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vSmartMOM.set_hitran_edition! Function

julia

set_hitran_edition!(edition::AbstractString)

Set the active HITRAN edition. Valid values:

"artifact" — use legacy HITRAN 2016 data from Julia Artifacts (default)
Any other string (e.g., "HITRAN2024") — use data downloaded from hitran.org, stored in a local scratch-space cache. Data is auto-downloaded on first access.

Example

julia

set_hitran_edition!("HITRAN2024")  # switch to latest HITRAN
set_hitran_edition!("artifact")    # back to legacy

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vSmartMOM.get_hitran_edition Function

julia

get_hitran_edition()

Return the currently active HITRAN edition string.

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vSmartMOM.available_hitran_editions Function

julia

available_hitran_editions()

List all locally available HITRAN editions. Always includes "artifact" (legacy HITRAN 2016). Additional editions appear as they are downloaded to the scratch cache.

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vSmartMOM.hitran_info Function

julia

hitran_info(molecule::AbstractString)

Return metadata for the given molecule under the current HITRAN edition.

For "artifact" edition, returns basic info. For downloaded editions, returns the full metadata from the .meta.toml file (edition, download date, wavenumber range, SHA256, source URL).

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vSmartMOM.hitran_is_cached Function

Check whether HITRAN data for a molecule is already cached for the given edition.

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Cross-Section Workflow

vSmartMOM.Absorption.compute_absorption_cross_section Function

julia

compute_absorption_cross_section(model::HitranModel, grid, pressure, temperature; wavelength_flag=false)

Compute absorption cross-section from HITRAN line-by-line data.

Sums Voigt (or Doppler/Lorentz) line shapes over all transitions in the HITRAN table within the grid range. Uses a batched kernel to process all lines in a single launch for efficient GPU/CPU execution.

Arguments

model::HitranModel: Model with HITRAN data, broadening, wing_cutoff, CEF
grid: Wavenumber [cm⁻¹] or wavelength [nm] grid
pressure::Real: Pressure (hPa)
temperature::Real: Temperature (K)
wavelength_flag::Bool=false: If true, grid is wavelength in nm

Returns

Array: Absorption cross-section (cm²/molecule) at each grid point

source

julia

compute_absorption_cross_section(model::InterpolationModel, grid, pressure, temperature; wavelength_flag=false)

Compute absorption cross-section by interpolating a pre-computed lookup table.

Uses BSpline interpolation over (ν, p, T). Faster than line-by-line for repeated calls.

Arguments

model::InterpolationModel: Pre-computed interpolator with ν_grid, p_grid, t_grid
grid: Wavenumber [cm⁻¹] or wavelength [nm] grid
pressure::Real: Pressure (hPa)
temperature::Real: Temperature (K)
wavelength_flag::Bool=false: If true, grid is wavelength in nm

Returns

Array: Interpolated absorption cross-section (cm²/molecule) at each grid point

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vSmartMOM.Absorption.absorption_cross_section Function

julia

absorption_cross_section(model, grid, pressure, temperature; wavelength_flag=false)

Calculate absorption cross-section. Convenience wrapper around compute_absorption_cross_section.

Arguments

model::AbstractCrossSectionModel: HitranModel or InterpolationModel
grid: Wavelength [nm] or wavenumber [cm⁻¹] grid (see wavelength_flag)
pressure::Real: Pressure (hPa)
temperature::Real: Temperature (K)
wavelength_flag::Bool=false: If true, grid is wavelength in nm; else wavenumber in cm⁻¹

Returns

Vector: Absorption cross-sections (cm²/molecule) at each grid point

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vSmartMOM.Absorption.read_hitran Function

julia

read_hitran(filepath; mol=-1, iso=-1, ν_min=0, ν_max=Inf, min_strength=0)

Read and parse a HITRAN line-by-line data file into a HitranTable.

Filters lines by molecule, isotopologue, wavenumber range, and minimum line strength. Uses fixed-width column parsing per the HITRAN format specification.

Arguments

filepath::String: Path to HITRAN .par or .hitran file
mol::Int=-1: Filter by molecule ID (-1 = all)
iso::Int=-1: Filter by isotopologue ID (-1 = all)
ν_min::Real=0: Minimum wavenumber (cm⁻¹)
ν_max::Real=Inf: Maximum wavenumber (cm⁻¹)
min_strength::Real=0: Minimum line intensity at 296 K

Returns

HitranTable: Struct with line parameters (νᵢ, Sᵢ, γ_air, γ_self, E″, etc.)

Throws

HitranEmptyError: If no lines match the filter criteria

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vSmartMOM.Absorption.make_hitran_model Function

julia

make_hitran_model(hitran::HitranTable, 
                  broadening::AbstractBroadeningFunction; 
                  wing_cutoff::Real=40, 
                  vmr::Real=0, 
                  CEF::AbstractComplexErrorFunction=HumlicekWeidemann32SDErrorFunction(), 
                  architecture::AbstractArchitecture = default_architecture())

Convenience function to make a HitranModel out of the parameters (Matches make_interpolation_model)

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vSmartMOM.Absorption.make_interpolation_model Function

julia

make_interpolation_model(hitran::HitranTable, 
                broadening::AbstractBroadeningFunction, 
                wave_grid::AbstractRange{<:Real}, 
                p_grid::AbstractRange{<:Real},
                t_grid::AbstractRange{<:Real}; 
                wavelength_flag::Bool=false,
                wing_cutoff::Real=40, 
                vmr::Real=0, 
                CEF::AbstractComplexErrorFunction=HumlicekWeidemann32SDErrorFunction(),
                architecture::AbstractArchitecture = default_architecture())

Using a HitranModel, create an InterpolationModel by interpolating the lineshape function at the given pressure and temperature grids

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julia

make_interpolation_model(absco::AbscoTable, wave_grid, p_grid, t_grid; 
                         wavelength_flag=false, architecture=default_architecture())

Create an InterpolationModel from ABSCO tabulated cross-section data.

Linearly interpolates the pre-computed cross-sections onto the specified pressure and temperature grids. Uses the ABSCO format (ν, p, T) for the lookup table.

Arguments