Re: a very large grib file

It may not be too hard to fix NCL such that it could read GRIB 1 files
that
are greater than 2GB. I will experiment with this.

wgrib can only read past the 2GB point if it is compiled and run on a
64 bit machine,
using 8-byte longs.
However, you could use wgrib repeatedly to split off initial chunks
of the GRIB file into a set of files less than 2GB.
  -dave

On Mar 9, 2007, at 7:41 AM, Dennis Shea wrote:

>> I have a grib file of 7 Gb. Can NCL split this file into smaller
>> pieces, either
>> by retaining the format or by converting it to NetCDF? Current NCL
>> functions
>> seem not to be supporting files larger than 2 Gb. If NCL cannot
>> handle files
>> like this at all, could you suggest a way for doing this task?
>> _______________________________________________
>
> [1] smaller grib files
>
> NCL does not write GRIB so the answer is "no".
>
> [2] It could be converted to netCDF. However, the file
> size would be larger. NCL supports netCDF files
> greater than 2GB but no single variable can be > 2GB
>
> GRIB's strength is that it is efficient at storing data.
> Convert GRIB to float and storing as netCDF usually
> results in a netCDF files that is 2-3 time larger
> than the original GRIB file.
>
> [3] suggestion ... use "wgrib" to partition the grib file
> into smaller files.
>
> http://www.cpc.ncep.noaa.gov/products/wesley/wgrib.html
>
> see the "tricks" section
>
> ftp://ftp.cpc.ncep.noaa.gov/wd51we/wgrib/tricks.wgrib
>
> [4] comment: GRIB is a record format not a file format.
> In fact, it only recognizes 2-dimensional horizontal grids.
> NCL scans the grib records and creates the multidimensional
> records that look like netCDF variable/files.
>
>
> Perhaps an NCL developer can add more?
>
> Regards,
> D
> _______________________________________________
> ncl-talk mailing list
> ncl-talk_at_ucar.edu
> http://mailman.ucar.edu/mailman/listinfo/ncl-talk

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Received on Fri Mar 09 2007 - 11:00:38 MST