API

This application aims to improve on existing line-by-line radiative transfer models by separating the data management and calculation. Data management is handled by a Database object, as described in the previous section, to eliminate the need to explicitly interact with the ascii/data files typically needed when using existing line-by-line models. Absorption spectra calculation is handled by a Spectroscopy object, which allows the user to specify which molecular lines, continua, and cross section models they would like to use.

Absorption calculation

A Spectroscopy object allow users to choose which models are used to calculate the molecular lines, various molecular continua, and absorption cross sections. Currently, the supported models are as follows:

Component	Models
lines	pyLBL, pyarts(in progress)
continua	MT-CKD
cross sections	arts-crossfit

For example, to create a Spectroscopy object using the default spectral lines model and the MT-CKD continuum, use:

from pyLBL import Spectroscopy

spectroscopy = Spectroscopy(atmosphere, grid, database, mapping=mapping,
                            lines_backend="pyLBL", continua_backend="mt_ckd",
                            cross_sections_backend="arts_crossfit")

Here the atmosphere and mapping arguments are xarray Dataset and python dictionary objects respectively that describe the input atmospheric conditions (see the previous “Atmospheric Inputs” section). The database and grid arguments are Database and numpy array objects that describe the spectral inputs (see the previous “Spectral inputs” section). The last three arguments (lines_backend, continua_backend, and cross_sections_backend) are strings that determine which models will be used for each component of the calculate (see the table above).

Absorption coefficients can be calculated using the Spectroscopy object by running:

absorption = spectroscopy.compute_absorption(output_format="all")

See the next section “Absorption Output” which discusses the output options.