SHDOM: Terminology
The medium properties (extinction, single scattering albedo, Legendre
expansion of the phase function, temperature) are input at grid points
from a "property file". These fields are defined spatially (X, Y, and Z
spacing) by the "property grid", which is defined by the input file and
is not the actual spatial grid used for computatations. The internal
grid used for computation has two components: the "base grid" is
regularly spaced (even in X and Y, even or not in Z) and is defined by
input parameters NX, NY, NZ, and GRIDTYPE; the "adaptive grid" is all
the grid cells including those defined by subdividing the base grid
cells. New cells are made by "cell splitting", which is the process of
figuring out which cells need to be subdivided and dividing them in half
to create new grid points. The "sequence acceleration" is a method to
reduce the number of iterations by extrapolating the source function to
where it is hoped the ultimate solution is. The iterations proceed
until the "solution criterion" is reached, when the source function is
changing by sufficiently small amounts that convergence is declared.
The "spherical harmonic terms" are the series expansion of the angular
dependence of the source function. The angular dependence is also
represented by "discrete ordinates", which are discrete directions
(mu_i, phi_i) at which the source function or radiance is specified.
Angles are specified by mu, which is the cosine of the zenith angle,
and phi, which is the azimuth angle, counter-clockwise from the X axis.
"Delta-M scaling" is a standard method of reducing the forward
scattering peak in the phase function, by scaling the phase function,
single scattering albedo, and extinction so the solution to the
radiative transfer equation is the same. The "independent pixel"
approximation is a standard method of solving for horizontal domain
averaged radiative properties of an inhomogeneous medium by averaging
the results of 1D radiative transfer on separate columns.