degrib msg and submsg

[Bernd Becker]

Wesley,


Hmmm,  assume you maintain a forecast  archive
and from one day to the next, you switch from grib 1 data to grib 2
data. Each grib  file has its meta data stored separately in one ctl and
idx file each.
Is it  then possible to read the whole archive in one grads job,
despite the mix of grib1 and grib 2 data?
(when) is grads able to read grib2 data?

Many thanks,
Bernd.

On Tue, 2007-10-09 at 13:55 -0400, Wesley Ebisuzaki wrote:
> 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
> >>
> > --
> > Bernd Becker   The Monthly Outlook
> > Met Office  FitzRoy Road  Exeter   Devon EX1 3PB  United Kingdom
> > Tel.: +44 (0) 1392 884511 Fax: +44 (0)870 900 5050
> > E-mail:bernd.becker at metoffice.com  -  http://www.metoffice.com
> >
--
Bernd Becker   The Monthly Outlook
Met Office  FitzRoy Road  Exeter   Devon EX1 3PB  United Kingdom
Tel.: +44 (0) 1392 884511 Fax: +44 (0)870 900 5050
E-mail:bernd.becker at metoffice.com  -  http://www.metoffice.com