Re: status africa data

[Robb Kambic <rkambic@xxxxxxxxxxxxxxxx>]

On Fri, 5 Jun 2009, Ethan Davis wrote:

> Robb Kambic wrote:
> > There is also a problem with the TOM_REALFORECASTS.20080112_v1_pf.grb grib
> > that has ~50 perturbations in the file. The variables look the same to
> > the our grib reader because ECMWF uses local additions to the PDS
> > section to distinguish the variables. Using the ECMWF decoder gribex,
> > the following local use information was displayed.
> >
> > ECMWF local usage identifier.               30
> >  Class.                                       1
> >  Type.                                       11
> >  Stream.                                   1035
> >  Version number or Experiment identifier.  0001
> >
> > I don't know what this means but it probably identifies the variables so
> > they aren't treated the same. According to the WMO documentation it states:
> >
> > 29-40    Reserved: need not be present
> > 41-nn    Reserved for originating center use
> >
> > So ECMWF is complying with the Grib1 specfications.
>
> I'm not sure I understand how this is in compliance. Since 29-40 are
> reserved, shouldn't they be using 41 or above for the local usage
> identifier?

Ethan,

They do, look at:

http://www.ecmwf.int/publications/manuals/libraries/gribex/localDefinition1.html

The problem I see is that it describes the ensemble information but so far 
I haven't found out how they distinguishing the perturbations.  The PDS is 
106 bytes long, the ensemble information stops at byte 52. The information 
in bytes 53-106 appears to be the same for every record. So that doesn't 
help. I'll have to create a support message about this problem.

Robb...




> Ethan

===============================================================================
Robb Kambic                                Unidata Program Center
Software Engineer III                      Univ. Corp for Atmospheric Research
rkambic@xxxxxxxxxxxxxxxx                   WWW: http://www.unidata.ucar.edu/
===============================================================================