SHDOM: Correlated K-distribution File Format
The CKD file has the correlated k-distribution information for a
series of spectral bands for a particular atmospheric profile. This file
is made by another program (e.g. ckdfu.f) from a profile. Each band,
i.e. a range of wavenumbers, has a k-distribution associated with it.
The k-distibution is performed as a discrete sum over probability
intervals (the delta g in the notation of Fu and Liou, 1993). A
radiative transfer calculation is done for each "k" in the sum, which
represents the gaseous absorption. The distribution of gases in the
atmosphere is assumed to horizontally uniform, and so the absorption
coefficients depend only on height. Thus the CKD file specifies the
absorption coefficient (in km^-1) for each height, "k" in the sum, and
each band. The delta g's are the weights with which the separate
radiative transfer results are added together.
There are three sections in the CKD file.
- The band information.
- The atmosphere information.
- The absorption coefficients for each band and g range.
The format is:
Comment line
Number of bands
Comment line
For each band:
band num, waveno1, waveno2, solar flux, number of k's, all the delta g's
Number of z levels
Two comment lines
For each atmospheric level from the top down:
height, (other profile information is not used)
Comment line
For each band and level:
band number, level number, all the k_i's
Notes: waveno1 and waveno2 are the starting and ending wave numbers in
cm^-1 of the bands; solar flux is the top of the atmosphere solar
irradiance in W/m^2 for overhead sun. The level numbers start with 1
at the top of the atmosphere. The levels in the CKD file are completely
independent of the levels in the SHDOM run, though they should cover the
SHDOM levels. The k-distributions should start with the lowest k's
(they are used in the reverse order in the program).