Currently the snow area fraction, FR_SNOW (called snc in CORDEX), cannot be processed since it is neither a CCLM output variable nor is it calculated in the first CMOR processing step as is being done for some other variables.
The calculation of FR_SNOW should thus be included in this first processing step, e.g. in the file second.sh.
This is the formula needed for calculation of FR_SNOW taken from variables table:
Max(0.01,Min(1.,W_SNOW/0.015))*H(x)
I do not know, however, what H(x) is.
You can contact Klaus Keuler ([email protected]) on this issue.