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[netCDF #RJB-156641]: hgt.mon.mean.nc and nc2text

Hi Michal,

> I have been using the command "nc2text" to extract data from the "Link to
> files" data set in the link below that extracts the netCDF file "
> hgt.mon.mean.nc". This is or has always been a netCDF file and has worked
> for me over the past couple of years, yet this month for the first time the
> program is telling me "Not a netCDF file" and does not work. The file size
> of the file "hgt.mon.mean.nc" looks to be about 1/2 of what it should be
> compared to last month so I susspect the upload to the ftp server has
> failed. But I do not know if NOAA changed the format or if its corrupt just
> this month. If the format has changed then has there been an update to
> "nc2text"?. I have no idea currently.
> http://www.esrl.noaa.gov/psd/cgi-bin/db_search/DBSearch.pl?Dataset=CDC+Derived+NCEP+Reanalysis+Products+Pressure+Level&Variable=Geopotential+height&Statistic=Mean&group=0&submit=Search

NOAA changed to use netCDF-4 classic model format instead of
netCDF classic format.  The data is still in a netCDF format
that can be read by any previous netCDF program, as long as
the program is relinked to the netCDF-4 library. You are
probably using nc2text linked with the older netCDF-3 library
that did not support lossless compression of data.  This is 
a feature of netCDF-4 that many organizations are making use
of, because it results in significantly smaller data files
that can be accessed more quickly across a network.

More information about the netCDF-4 classic model format is
available from the links below:


If you compiled nc2text from source, you shouldn't have to change anything in
the program.  Instead, you need to download a more recent version of netCDF-4, 
build and install it, then compile and link nc2text to use the newly installed
netCDF C library.  You can get the new version and instructions for building 
it from here:


Russ Rew                                         UCAR Unidata Program
address@hidden                      http://www.unidata.ucar.edu

Ticket Details
Ticket ID: RJB-156641
Department: Support netCDF
Priority: Normal
Status: Closed

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