CDO

Hello; I have large (~100GB) 30 days outputs and I would like to split that in monthly output and do monthly averages.

I did that in the past for much smaller files merging it first in one file than splitting it (maybe that was dumb but worked).

Now I am trying to do:

cdo -monmean file1.nc file2.nc file3.nc out.nc

and

cdo -splitmon file1.nc file2.nc file3.nc out.nc

And got the following error:

cdo (Abort): Unprocessed Input, could not process all Operators/Files

also tried cdo -splitmon file[1-3].nc out.nc with the same errors.

And cdo mergetime -apply,splitmon file[1-3].nc out.nc with wrong results..

Any help and smarter way to do it?

Many thanks

Carlos