A two-column file, defining water cloud property files (see wc_file) in the first
column and the corresponding weights in the second column.
wc_ipa_files file
The radiative transfer calculation is performed independently for each
cloud column and the result is the weighted average of all independent
columns. If ic_ipa_files and wc_ipa_files are both
defined, both must have the same columns in the same order, otherwise
uvspec will complain. See
examples/UVSPEC_WC_IPA_FILES.INP for an example.