SHDOM Optical Property Generation Overview
The optical property file generation system for SHDOM has been upgraded
to be more flexible and accurate. Instead of the cloudprp
program, there are now three Fortran 90 programs:
make_mie_table.f90 and make_ice_table.f90 for making
scattering tables and propgen.f90 for generating the property
file from a particle properties file. The particle properties file
specifies the mass content (g/m^3) and effective radius (microns) of
each particle component at each grid point. The make_mie_table
program generates scattering tables for gamma or lognormal size
distributions of spherical particles, while make_ice_table
generates scattering tables in the shortwave for gamma distributions of
one of eight ice crystal shapes using Ping Yang's single scattering
properties. The program plotscattab.f90 makes a plotting file
of phase functions versus angle from the Legendre series in a scattering
table file. The propgen program allows an arbitrary mixture of any
number of pure components at each grid point. The extinction and single
scattering albedo from all the components are combined exactly, while
phase functions existing in the scattering tables and newly created
phase functions are chosen so that the phase function error is smaller
than user specified tolerances. The result is a tabulated phase function
format property file for SHDOM with a small as possible memory
requirement that closely approximates the desired optical property
distribution.
The example Unix script run_propgen_example shows how to make
scattering tables and run propgen to generate a property file for SHDOM.
Scattering tables are made at two wavelengths for lognormal
distributions of spherical dust aerosols, gamma distributions of cloud
water droplets, and gamma distributions of plate and rough aggregate ice
crystals. The example particle file nauru19990707.part
specifies the mass content and effective radius distributions for a
horizontally uniform aerosol layer (particle type 1) from the surface to
1.4 km, a broken cumulus water cloud layer (type 2) from 0.59 to 2.03
km, and a cirrus layer made of plates and aggregates (types 3 and 4)
from 8.75 to 14.75 km. The two-dimensional (X-Z) cumulus and cirrus
cloud distributions are derived from the ARM millimeter-wave cloud radar
on Nauru Island. The distribution includes an IDL program
plot_propgen_example.pro which plots the components of the
particle file, the resulting extinction and single scattering fields,
and radiance output from SHDOM (requires other IDL files in the SHDOM
distribution).