degrib msg and submsg

[Wesley Ebisuzaki]

Bernd,

     IMHO grib1 is doomed as grib2's compression is too good (~1/5 of grib1
size for operational model files)  and compression will increase as the
world goes
to higher resolution files.  Since grib1 is 1/3 the size of a netcdf
file, you will
see pretty big (uncompressed) netcdf files.   (Your 4x expansion is a big
underestimate.)

       Wesley






Bernd Becker wrote:
> Wesley,
>
> see below:
>
> On Tue, 2007-10-09 at 10:33 -0400, Wesley Ebisuzaki wrote:
>
>> Patrick,
>>
>> Patrick Reuter wrote:
>>
>>> Dear all,
>>>
>>> I download grib2 files and have problems to degrib into Grads.
>>>
>>> I have the following inventory :
>>>
>>> 1:115:d=2007100706:HGT:850 mb:15 hour fcst
>>> 2:227347:d=2007100706:TMP:850 mb:15 hour fcst
>>> 3:315793:d=2007100706:RH:850 mb:15 hour fcst
>>> 4.1:411471:d=2007100706:UGRD:850 mb:15 hour fcst
>>> 4.2:411471:d=2007100706:VGRD:850 mb:15 hour fcst
>>>
>>> And I want to extract BOTH the UGRD/VGRD values. Here are my degrib
>>> commands :
>>>
>>> ./degrib grib2file -C -msg 4.1 -Flt -Interp -GrADS -out UGRD
>>> ./degrib grib2file -C -msg 4.2 -Flt -Interp -GrADS -out VGRD
>>>
>>>
>> The notation 4.1 (message #4, submessage #1) is unique to wgrib2.  You
>> should consult the degrib documentation to see how they handle submessages.
>>
>> If all else fails, you can also use wgrib2 to convert submessages to
>> messages by
>>
>>           wgrib2 -grib new_grib old_grib
>>
>>
>>> The first command works fine, but in the second command, I always get
>>> the following error message :
>>>
>>> ERROR: In call to Grib2Convert.
>>> ERROR: In call to ReadGrib2Record.
>>> ERROR: Unpack library error code (0 2)
>>>
>>> In other words, since the VGRD data is always stored in GRIB2
>>> submessages, I can't access to it.
>>>
>>> Is anybody familiar with my problem ?
>>>
>>> Thanks in advance
>>>
>>>   Patrick
>>>
>> BTW if the grib2 files are lat-lon/mercator/gaussian-grid then you should
>> consider converting the files into netcdf using wgrib2.  The netcdf files
>> can be opened by GrADS using the sdfopen command.  I believe that
>> degrib can produce netcdf files too.
>>
>>
>
> Is netcdf the death-knell for GRIB1 and 2 data on a global scale?
> I suppose the NEtcdf files will be about 4 times larger  on average.
> This would increase I/O times and storage requirements.
>
> When will NetCdf use compression?
>
> Thanks,
> Bernd.
>
>
>>    Wesley
>>
> --
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