HITRAN look-up tables¶

HITRAN line-by-line absorption cross-section LUTs and a Beer–Lambert forward model. hitran-api is imported lazily. RTM stack.

hapi_lut ¶

HAPI-driven absorption cross-section look-up tables.

Submodules

config — GasConfig / LUTGridConfig / ATMOSPHERIC_GASES.
generator — single-gas fetch / compute / wrap / save pipeline.
multi — multi-gas orchestration (separate-per-gas + combined).
beers — LUT interpolation + Beer-Lambert transmittance + the differential-ratio form used for plume-enhancement retrievals.

HAPI (hitran-api on PyPI) is imported lazily inside the generator + multi pipelines — importing this sub-package does not require HAPI, only building / fetching a LUT does.

GasConfig `dataclass` ¶

GasConfig(name: str, molecule_id: int, isotopologue_id: int, nu_min: float, nu_max: float, description: str = '')

Configuration for a single HITRAN gas species.

Attributes:

Name	Type	Description
`name`	`str`	Short name used as HAPI SourceTable id (e.g. 'CH4').
`molecule_id`	`int`	HITRAN molecule id (see `hitran.org`).
`isotopologue_id`	`int`	HITRAN isotopologue id (1 = most abundant).
`nu_min`	`float`	Lower wavenumber bound [cm⁻¹].
`nu_max`	`float`	Upper wavenumber bound [cm⁻¹].
`description`	`str`	Free-text description for dataset metadata.

LUTGridConfig `dataclass` ¶

LUTGridConfig(T_grid: ndarray = (lambda: np.array([200, 220, 240, 260, 280, 300, 320], dtype=float))(), P_grid: ndarray = (lambda: np.array([0.1, 0.2, 0.4, 0.6, 0.8, 1.0], dtype=float))(), nu_step: float = 0.01, diluent_composition: dict[str, float] | None = None)

Grid configuration shared across gases for a single LUT build.

Attributes:

Name	Type	Description
`T_grid`	`ndarray`	Temperature knots [K]. Should bracket the atmospheric range of interest (upper-troposphere ~200 K to surface ~320 K).
`P_grid`	`ndarray`	Pressure knots [atm]. Should bracket the altitude range of interest (upper-tropo ~0.1 atm to surface ~1.0 atm).
`nu_step`	`float`	Spectral step [cm⁻¹] on the output wavenumber grid. HITRAN lines have HWHMs down to ~0.005 cm⁻¹ at low pressure — step ≤ 0.01 cm⁻¹ for hyperspectral work, 0.05 cm⁻¹ for tutorials.
`diluent_composition`	`dict[str, float] \| None`	Optional override for the air diluent fractions. If None, each gas gets {'air': 1-VMR, 'self': VMR}.

get_diluent_for_gas ¶

get_diluent_for_gas(gas_name: str, vmr_nominal: float | None = None) -> dict[str, float]

Return the HAPI Diluent dict for a given gas.

If an explicit diluent_composition override was supplied at construction time it is returned verbatim; otherwise a standard {'air': 1 - VMR, 'self': VMR} split is built from DEFAULT_VMR_NOMINAL[gas_name] (falling back to 1e-6).

Source code in src/plumax/hapi_lut/config.py

def get_diluent_for_gas(
    self,
    gas_name: str,
    vmr_nominal: float | None = None,
) -> dict[str, float]:
    """Return the HAPI ``Diluent`` dict for a given gas.

    If an explicit ``diluent_composition`` override was supplied at
    construction time it is returned verbatim; otherwise a standard
    ``{'air': 1 - VMR, 'self': VMR}`` split is built from
    ``DEFAULT_VMR_NOMINAL[gas_name]`` (falling back to 1e-6).
    """
    if self.diluent_composition is not None:
        return dict(self.diluent_composition)
    if vmr_nominal is None:
        vmr_nominal = DEFAULT_VMR_NOMINAL.get(gas_name, 1e-6)
    return {"air": 1.0 - vmr_nominal, "self": vmr_nominal}