Location of file defining aerosol optical pproperties.
aerosol_file type file
type defines the file type, which can be one of the following:
- gg
-
Location of aerosol asymmetry parameter file.
The file must have two columns. Column 1 is the altitude in km. Column 2 is the asymmetry parameter of each layer. The asymmetry parameter defined with this option is constant with wavelength. If you require spectral dependence please use aerosol_file explicit. Comments start with #. Empty lines are ignored.
- ssa
-
Location of aerosol single scattering albedo file.
The file must have two columns. Column 1 is the altitude in km. The altitude grid must be exactly equal to the altitude grid specified in the file atmosphere_file. Column 2 is the single scattering albedo of each layer. The single scattering albedo defined with this option is constant with wavelength. If you require spectral dependence please use aerosol_file explicit. Comments start with #. Empty lines are ignored.
- tau
-
Location of aerosol optical depth file.
The file must have two columns. Column 1 is the altitude in km. The altitude grid must be exactly equal to the altitude grid specified in the file atmosphere_file. Column 2 is the aerosol optical depth of each layer. To allow wavelength-dependent aerosol optical thickness please use either aerosol_angstrom or aerosol_file explicit. Comments start with #. Empty lines are ignored.
- moments
-
Set the aerosol phase function moments to the values specified in the aerosol moments file.
The file contains one column with arbitrary number of Legendre terms of the phase function. The phase function
is
(1) where
is the m'th moment and
is the m'th Legendre polynomial. If not specified, a Henyey-Greenstein phase function is assumed where the asymmetry parameter g is either a default value depending on the aerosol type or it may be specified using aerosol_modify set gg. The phase function will be the same for all altitudes and wavelengths. See aerosol_file explicit if more flexibility is wanted. May only be used together with the cdisort or fdisort2 solver in combination with the option disort_icm moments.
- explicit
-
A way to specify aerosol optical depth, single scattering albedo, and phase function moments for each layer.
The file must have two columns where column 1 is the altitude in km. The second column is a the name of a file which defines the optical properties of the layer starting at the given altitude. The files specified in the second column must have the following format:
- Column 1:
-
The wavelength in nm. These wavelengths may be different from those in source solar file. Optical properties are interpolated to the requested wavelengths.
- Column 2:
-
The extinction coefficient of the layer in units km-1.
- Column 3:
-
The aerosol single scattering albedo of the layer.
- Column 4-(nmom+4):
-
The moments of the aerosol phase function.
For some simple examples see the files examples/AERO_*.LAYER. Note that if using the rte_solver cdisort it makes good sense to make the number of moments larger than number_of_streams. For rte_solver fdisort1 and rte_solver polradtran the number of moments included in the calculations will be number_of_streams+1. Higher order moments will be ignored for these solvers. Please note that the uppermost line of the aerosol_file explicit denotes simply the top altitude of the uppermost layer. The optical properties of this line are consequently ignored. There are two options for this line: either an optical property file with zero optical thickness is specified or ”NULL” us used.