Dear ferreters,
I cannot open multi-netCDF files (mc files) in ferret anymore. They are created with nc2mc (http://www.pa.op.dlr.de/~PatrickJoeckel/nc2mc/index.html) on Linux. It works fine in v6.72, but in v6.84, the following error message is issued:
**netCDF error NetCDF: Unknown file format (OPeNDAP/netCDF Error code -51) Data set: <whatever mc file>
Please find attached a very simple example I made by hand containing only a time dimension and 6 time points. Both single files are recognized normally, but the mc file causes the above error in v6.84.
So it must be a change in ferret between v6.72 and v6.84. From the changelogs, I gathered that between these versions:
1) the number of dimensions was increased from 4 to 6
2) all coordinate axes are now treated as double precision.
http://ferret.pmel.noaa.gov/Ferret/documentation/release-notes/version-6-8-release-notes/
3) "Ferret adheres more closely with the CF conventions for axis directions"
http://ferret.pmel.noaa.gov/Ferret/documentation/release-notes/version-6-8-2-release-notes/
http://ferret.pmel.noaa.gov/Ferret/documentation/release-notes/version-6-7-3-release-notes/
4) "Ferret v6.8.2 is linked with NetCDF 4.2"
http://ferret.pmel.noaa.gov/Ferret/documentation/release-notes/version-6-8-2-release-notes/
To 3) I first guessed that mc files don't work anymore if the contained single files include an axis that is decreasing-ordered (which is the case for our large 3-D files), but my simple example without decreasingly ordered axes seems to prove that theory wrong.
Many thanks in advance for your help.
Best wishes,
Hella
P.S: Ferret documentation for descriptor files
http://ferret.pmel.noaa.gov/Ferret/documentation/users-guide/converting-to-netcdf/CREATING-A-MULTI-FILE-NETCDF-DATA-SET