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Re: Problems decoding GRIB2 GFS Ensemble grids

Kevin,

The most recent version of dcgrib2 (5.9.3) will store the GRIB2 data in
the grid file without unpacking the data block, making the GEMPAK file
much smaller, and the
decoding process much faster. The older GEMPAK distributions will not be
able to read those decoded files however, since they do not know how to
unpack the GRIB2 data block, so if you use the 5.9.3 decoder, you would
want to upgrade the other programs as well, or recompile the dcgrib2
program from 5.9.3 to
use the previous packing method for the data- but you may find that
unpacking and
repacking the data in realtime is quite a load on the LDM pqact
processing (otherwise, you can use nagrib2 outside of the LDM which will
be compatible
with the previous versions).

I'll add a command line flag to the 5.9.4 dcgrib2 to allow you to select
the storage
method for backward compatibility.

Steve Chiswell
Unidata User Support




On Tue, 2006-10-10 at 01:24 +0000, Kevin R. Tyle wrote:
> Hi Steve,
> 
> Thanks for the updated files.  I can now get it to work using the
> GEMPAK5.9.3 version of dcgrib2 using the corrected tables.  However, even
> with the updated tables, versions 5.9.1 and 5.7.4 of dcgrib2 still do not
> decode.  Perhaps I shall just recompile dcgrib2 for use in these two
> distributions (which are still in operational use here) unless you have
> another idea.
> 
> Thanks,
> 
> Kevin
> 
> ______________________________________________________________________
> Kevin Tyle, Systems Administrator               **********************
> Dept. of Earth & Atmospheric Sciences           address@hidden
> University at Albany, ES-235                    518-442-4578 (voice)
> 1400 Washington Avenue                          518-442-5825 (fax)
> Albany, NY 12222                                **********************
> ______________________________________________________________________
> 
> On Mon, 9 Oct 2006, Steve Chiswell wrote:
> 
> > Kevin,
> >
> > The GEMPAK GRIB2 parameter tables use 4 numbers to define the parameter
> > name.
> > The 4th column is the parameter template, which allows different names
> > to be assigned depending on the type ofaccumulation, average, ensemble
> > etc. used.
> > Log messages from dcgrib2 under "decode_grib2 -34" about unknown
> > parameter
> > mean that the decoder tables need to be updated (in particular, entries
> > for ensemble PDTs 1 and 11 in column 4).
> >
> > Updated g2varswmo2.tbl and g2varsncep1.tbl tables which include the
> > ensemble entries can be downloaded from:
> >
> > http://www.unidata.ucar.edu/downloads/gempak/tables/
> >
> > Steve Chiswell
> > Unidata User SUpport
> >
> >
> >
> >
> > On Mon, 2006-10-09 at 21:26 +0000, Kevin R. Tyle wrote:
> > > I've been attempting to decode the GFS ensemble data from the "new"
> > > CONDUIT NCEP ftp directory, as described in
> > > http://www.unidata.ucar.edu/data/conduit/ldm_idd/ensemble_files.html#GRIB2.
> > > However, dcgrib2 is not able to determine the GEMPAK parameter name, and
> > > no GEMPAK grid is created.  I've attached the output from the dcgrib2 log.
> > >
> > > gec00.t12z.pgrb2af48
> > >
> > > Any ideas?
> > >
> > > Thanks,
> > >
> > > Kevin
> > >
> > > ______________________________________________________________________
> > > Kevin Tyle, Systems Administrator               **********************
> > > Dept. of Earth & Atmospheric Sciences           address@hidden
> > > University at Albany, ES-235                    518-442-4578 (voice)
> > > 1400 Washington Avenue                          518-442-5825 (fax)
> > > Albany, NY 12222                                **********************
> > > ______________________________________________________________________
> > --
> > Steve Chiswell <address@hidden>
> > Unidata
> >
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-- 
Steve Chiswell <address@hidden>
Unidata