Location of molecular scattering or absorption optical depth file.
mol_tau_file sca/abs filename
- sca
-
Usually, the Rayleigh scattering cross section is calculated from the air pressure provided in atmosphere_file (scaled with pressure). Use this parameter only if you really want to specify the optical depth directly (e.g. for a model intercomparison). The optical thickness profile may be either monochromatic or spectral.
- abs
-
Usually, molecular absorption is calculated from trace gas concentrations provided in atmosphere_file (scaled with mol_modify O3 300 DU, etc.). Use this option only if you want to specify the optical depth directly (e.g. for a model intercomparison) or for a line-by-line calculation. If a spectral mol_tau_file is specified, the wavelength grid defined there is used as the internal wavelength grid for the radiative transfer calculation, if not defined otherwise with wavelength_grid_file.
The file can be either of the following three formats:
- Monochromatic
-
Column 1 is the altitude in km Column 2 is the absorption optical depth of each layer.
- Spectral, ASCII
-
The first line contains the level altitudes in decreasing order; the following lines contain the wavelength [nm] in the first column and then the absorption optical depths of each layer.
- Spectral, netcdf
-
An example is available at the libRadtran homepage, the file UVSPEC.O2A.afglms.cdf is a line-by-line spectrum of the oxygen A-Band around 760nm, calculated for the mid-latitude summer atmosphere. The advantage of netcdf compared to ASCII is that it is much faster to read, and that the file is a self-contained, including data and a description of the variables and arrays. It is therefore particularly useful for line-by-line calculations where usually many spectral data points are involved.
Comments start with #. Empty lines are ignored.