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Re: ecmwf hybrid levels (fwd)

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  • Subject: Re: ecmwf hybrid levels (fwd)
  • Date: Mon, 22 Jun 2009 16:50:13 -0600 (MDT)
Hiya,

I'm interested in the Grib header information in the ECMWF data files.
An octal dump  shows a blank header, ie

Here's an od of a header from a file.


                                           7   7   7   7  \0  \0  \0  \0
15674460  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0
15674500   G   R   I   B


The 7   7   7   7 is the end of the previous grib record, then there are all
nulls to the word G R I B which is the begining of the Grib message. I didn't see information in any of the grib headers. Also Grib1Dump didn't find any header information. 

I'm looking for hybrid information in a Grib header.

Thanks,
Robb...

--------------------------------------------------------------------
                        Header : GRIB1
                    Discipline : 0 Meteorological Products
                  GRIB Edition : 1
                   GRIB length : 1558180
Originating Center : 98 European Center for Medium-Range Weather Forecasts (RSMC) 
        Originating Sub-Center : 0 WMO Secretariat
Product Definition : 0 Forecast/Uninitialized Analysis/Image Product 
            Parameter Category : -1 Meteorological Parameters
                Parameter Name : 133 Q Specific_humidity
               Parameter Units : kg kg-1
                Reference Time : 2008-09-07T00:00:00Z
                    Time Units : hour
          Time Range Indicator : product valid at RT + P1
                   Time 1 (P1) : 0
                   Time 2 (P2) : 0
       Generating Process Type : 132 Unknown
                    Level Type : 109 hybrid level
                 Level Value 1 : 26.0
                 Level Value 2 : 0.0
                    GDS Exists : true
                    BMS Exists : false
         Number of data points : 1038240
                     Grid Name : Latitude/Longitude Grid
                     Grid Shape: 0 spherical
         Spherical earth radius: 6367.47





 testdata/grid/grib/grib2/ecmwf/

ECMWF.2008.09.07.T00Z.uad_HGrbF00.A08334081908


is described here apparently:
http://www.ecmwf.int/products/data/technical/model_levels/model_def_91.html and according to this:
http://www.ecmwf.int/research/ifsdocs/DYNAMICS/Chap2_Discretization4.html#961180 "The values of the and for all are stored in the GRIB header" 
should be:

The values of a and b for all are stored in the GRIB header"


John,

Here's an od of a header from the above file.

                                           7   7   7   7  \0  \0  \0  \0
15674460  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0
15674500   G   R   I   B
The 7 7 7 7 is the end of the previous grib record, then there are all nulls to the word G R I B which is the begining of the Grib message. I didn't see information in any of the grib headers. Also Grib1Dump didn't find any header information. If they are referring to the above file name ECMWF.2008.09.07.T00Z.uad_HGrbF00.A08334081908
I looked for product ID information and I found the similar information to the NCEP information using header patterns 

TTAAii  CCCC  YYGGgg    Product                      Area

HHAA50  ECMF  YYHH00    500 hPa geopotential height  analysis          (NH)

What header information are referring too and where is the documentation?

yes, thats the question. is it in section 2? can you contact ecmwf to find out?