Location of molecular absorption optical depth file.
molecular_file file
Usually, molecular absorption is calculated from trace gas concentrations provided in atmosphere_file (scaled with ozone_column, 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 molecular_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 transmittance_wl_file. molecular_tau_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.





Arve Kylling 2010-03-10