Dear Raymond,

Thanks.  For now,  I have just converted the .nc files.

Cheers,

Marshall

On 26 Jul 2013 08:52, "Raymond Arritt" <rwarritt@gmail.com> wrote:
Dear Marshall,

With regard to the error,


 Opening /home/mmdoka/Downloads/RegCM-4.4-rc6/PreProc/DATA/SURFACE/GTOPO_DEM_30s
 .nc
 NetCDF: Unknown file format

I got an error like this too.  In my case it was caused by not having a current netCDF library linked to my code.  The RegCM group is now distributing files in a new version of netCDF that has transparent compression.  The benefit is that this decreases the file size by about 40% or so (sometimes more).

If this is the problem there are two options to fix it:  (1) you could rebuild the code using the most current version of netCDF 4 with HDF5 support, or (2) you could convert the files from the new format back to the old format (netCDF 3) using the command:

 nccopy -k 1  file1.nc file2.nc

Here file1.nc is the file that you currently have, in the new netCDF format.  The command will create file2.nc in the old netCDF format. Then file2.nc should be readable using your current build.

For example you could do something like

nccopy -k 1 GTOPO_DEM_30s.nc temp.nc
mv temp.nc GTOPO_DEM_30s.nc

Good luck!  I hope this is helpful for you.

Ray Arritt

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