Set the radiation source type
source type
source solar [file] [unit]
where type is either solar or thermal.
Solar radiation is per default output in W/(m2 nm) for spectral and
mol_abs_param LOWTRAN calculations. For all other mol_abs_param options
the output is integrated over the wavelength band.
Thermal radiation is per default output in W/(m2 cm-1), if the bandwidth
is equal to 1 cm-1 (default for mol_abs_param LOWTRAN calculations).
Otherwise the output is the integrated flux over the
wavenumber interval specified by thermal_bandwidth, thermal_bands_file,
or by the mol_abs_param option (kato, kato2, kato2.96,
fu, or avhrr_kratz).
The optional second argument file specifies the location of file holding the extraterrestrial spectrum.
The file must contain two columns. Column 1 is the wavelength in nm, and column 2 the corresponding extraterrestrial flux. The user may freely use any units he/she wants for the extraterrestrial flux. The wavelength specified grid defines the wavelength resolution at which results are returned. However, the wavelength range is determined by wavelength. source solar file may be omitted for thermal radiation calculations (source thermal) as well as transmittance and reflectivity calculations. If omitted, the output resolution equals the internal wavelength grid which the model chooses for the radiative transfer calculation. Comments start with #. Empty lines are ignored.
For some purposes it is useful to tell libRadtran the units of the spectrum. This can be done with the optional third argument. Possible choises for unit are per_nm, per_cm-1 or per_ck_band. If unit is set to per_nm libRadtran assumes that the unit of the spectrum is W/(m2 nm), if set to per_cm-1 it assumes W/(m2 cm-1).
Note that source solar file is ignored if mol_abs_param is specified.