Distribution README

This tar file contains two polarized plane-parallel radiative transfer
models written by Frank Evans at Colorado State University and the 
University of Colorado.  The first is rt3 which is for randomly oriented
particles (isotropic media) and includes solar and thermal sources of
radiation.  The second is rt4 which is for horizontally oriented
particles (azimuthally symmetric media), but does only thermal sources. 
The rt3 model is described in K. F. Evans and G. L. Stephens, 1991: 
"A New Polarized Atmospheric Radiative Transfer Model", J. Quant. 
Spectrosc. Radiat. Transfer, v. 46, no. 5, pp. 413-423, 1991.
The rt4 model is briefly described in Evans, K. F., and G. L. Stephens, 
1995: "Microwave radiative transfer through clouds composed of 
realistically shaped ice crystals. Part II: Remote Sensing of Ice Clouds",
J. Atmos. Sci., v. 52, 2058-2072.   

This latest version of rt3 and rt4 allows the radiances at any level in
the input medium to be output. The output format has been changed to
that the actual radiance is output for a specified number of azimuth
angles, instead of outputting the Fourier series.  The radiances may now
be output as V and H polarization and/or brightness temperatures (the
Planck function is always used internally now).    Delta-M scaling
may be specified for rt3.

The models are written in a variant of Fortran 77 which allows long
subroutine and variable names and the use of ENDDO in DO loops.  The
arrays are currently setup for a radiance vector length of 64 (e.g. 16
angles, 4 Stokes parameters).  See the beginning  of rt3.f and
radtran3.f or rt4.f and radtran4.f for documentation on using the
programs.

This code is distributed according to the terms of the "MIT License"
in the included LICENSE file.

The following is a list of the files:

  rt3.f         main program, contains documentation at beginning
  radtran3.f    RADTRAN subroutine with documentation at beginning
  radscat3.f    subroutines
  radintg3.f        "
  radutil3.f        "
  radmat.f          "

  rt4.f         main program, contains documentation at beginning
  radtran4.f    RADTRANO subroutine with documentation at beginning
  radscat4.f    subroutines
  radintg4.f        "
  radutil4.f        "

  scatcnv.f     program to convert scattering files from rt3 format 
                  (Legendre series in scattering angle) to rt4 format.

  runmietest    Unix script to test rt3 with the Mie example from the paper.
  runtesta      Unix script for a more general test of rt3.
  runtestr      Unix script that does a test of rt4 with spherical raindrops.
  runtestc      Unix script for a test of rt4 using oriented ice columns.


    Frank Evans           May 22, 2023
    retired from the University of Colorado, Boulder
    frank.evans@Colorado.edu  or  evansgmr3@gmail.com