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Re: status africa data

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  • Subject: Re: status africa data
  • Date: Fri, 05 Jun 2009 14:22:50 -0600
Sorry, I think I spoke without understanding any of the relevant
details. Is it _bytes_ 29-40 that are reserved or the numbers 29-40 that
can't be used for "local usage ID"?

I was thinking  the line

>>> ECMWF local usage identifier.               30

was in the reserved range 29-40 but I'm guessing I'm way off on that.

Ethan

Robb Kambic wrote:
> 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
> address@hidden           WWW: http://www.unidata.ucar.edu/
> ===============================================================================
> 

-- 
Ethan R. Davis                                Telephone: (303) 497-8155
Software Engineer                             Fax:       (303) 497-8690
UCAR Unidata Program Center                   E-mail:    address@hidden
P.O. Box 3000
Boulder, CO  80307-3000                       http://www.unidata.ucar.edu/
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