SHDOM: Property File Format

The properties of the medium may be input in three different formats. 1) the standard format specifies the extinction, scattering albedo, temperature, and Legendre phase function expansion at every grid point; 2) the extinction only format only specifies extinction at every grid point, while the other quantities are given in the header part; and 3) the tabulated phase function format specifies all properties except the phase function for each grid point, while many phase functions are tabulated in the header. All file types are plain ascii and read by Fortran free format (so most "lines" may be broken across lines). With a small code change (commenting in calls to read_property_size_netcdf and read_properties_netcdf in shdom90.f90) the tabulated phase function format property file may be read in netcdf format. Note: Chi1 is 3 times the asymmetry parameter.

The standard file format has two header lines: the first line has the size of the grid; the second line contains the X and Y grid spacing and the Z levels. There is then one line per grid point giving the properties. The format is as follows:

    Nx  Ny  Nz
    delX  delY  Z1  ...  Zn
    IX IY IZ Temp Extinct Albedo NumL Chi1 . . . ChiL
     . . . 
 
where IX, IY, and IZ are the spatial indices (1,...,Nx, etc.), Temp is the grid point temperature in Kelvin, Extinct is the extinction in units inverse of the grid spacing units, Albedo is the single scattering albedo, NumL is the Legendre series degree, and Chi(n) are the coefficients of the Legendre expansion of the phase function. Chi1 is 3*g, where g is the asymmetry parameter.

The extinction only format has five header lines: the first line must begin with 'E'; the second has the grid size; the third has the grid spacing and Z levels; the fourth has the temperatures in Kelvin of the Z levels; the fifth has the single scattering albedo, the degree of the Legendre expansion of the phase function, and then the Legendre coefficients. There is one line for every grid point containing the grid point indices and the extinction; if the NY is 1 then only the X and Z indices are given. The format is as follows:

    E
    Nx  Ny  Nz
    delX  delY  Z1 ... Zn
    T1 ... Tn
    Albedo  NumL  Chi1 ...  ChiL
    IX IZ Extinct   or   IX IY IZ Extinct
      . . .
 

The tabulated phase function format has a 4+NUMPHASE header lines, where NUMPHASE is the number of phase functions: the first line must begin with 'T'; the second has the grid size; the third has the grid spacing and Z levels; the fourth has the number of phase functions; and the following "lines" have the phase functions containing the degree of the Legendre expansion and then the Legendre coefficients. There is one line for every grid point containing the grid point indices, the temperature (Kelvin), the extinction, scattering albedo, and phase function index (1 to NUMPHASE) to the table in the header. The format is as follows:

    T
    Nx  Ny  Nz
    delX  delY  Z1 ... Zn
    numphase
    NumL  Chi1 ...  ChiL       (for each phase function)
      . . . 
    IX IY IZ  Temp Extinct Albedo  Iphase
 
The first Z level is the bottom surface and the last is the top surface. The Legendre coefficients are normalized so that Chi0 (which is not listed) is always 1. The Legendre coefficients do not actually need to be all on one line; in fact, propgen uses multiple lines for phase functions with more than 200 terms.