'Cross-section' molecules are those whose absorption coefficient
k is tabulated as a function of wavenumber, pressure and temperature
than calculated from individual line parameters. These are usually the heavier
and more complex molecules not included in the HITRAN 'line' database.
The RFM assigns indices ≥100 to the
most common of these, but any arbitrary molecule can be used.
The FILXSC can represent
files in the original HITRAN .xsc format, as well
the RFM .xsc format (which is the
HITRAN format with extra header records inserted).
However you will first need to concatenate the original HITRAN
files into a single file,
eg if you've downloaded a set of files N2O5*xsc from the
HITRAN web-site, then
cat N2O5*.xsc > n2o5.xsc
If a filename template DEFXSC is supplied, identified by
containing a '*' character,
first all the explicitly
specified files are read, then '*' character in the template is
expanded to the lower-case absorber name of any remaining
molecules (using the 'fnn' form for CFCs).
Cross-section data is provided as absorption coefficient
spectra measured at a set of arbitrary (p,T) coordinates.
For particular path (p,T) conditions,
the RFM interpolates using triangulation or, for points outside the
triangulation domain, interpolation to the value at the closest boundary
f11.xsc ! Cross section data for CFC-11
f12.xsc ! Cross section data for CFC-12
./rfm_files/*.xsc ! Other data, eg './rfm_files/f22.xsc'