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Re: status africa data




Hiya,

After talking to Tom Yoksas, he said that I should get new test data as the datasets has change. New data was obtained and it was split according to forecast hours, 6-240 and 246-360.

The TOM_Hindcasts type data only has one GDS so it was not split. The
TOM_REALFORECASTS was split according to above forecast hours and it
was indexed.



TOM_REALFORECASTS.F246-360.20080112_v1_cf.grb.gbx
TOM_REALFORECASTS.F246-360.20080112_v1_pf.grb.gbx
TOM_REALFORECASTS.F6-240.20080112_v1_cf.grb.gbx
TOM_REALFORECASTS.F6-240.20080112_v1_pf.grb.gbx

TOM_REALFORECASTS.F6-240.20080112_v1_pf.grb
TOM_REALFORECASTS.F6-240.20080112_v1_cf.grb
TOM_REALFORECASTS.F246-360.20080112_v1_pf.grb
TOM_REALFORECASTS.F246-360.20080112_v1_cf.grb

TOM_REALFORECASTS.20080112_v1_pf.grb
TOM_REALFORECASTS.20080112_v1_cf.grb

TOM_Hindcasts.20080619.20010619.PF_v2.grb
TOM_Hindcasts.20080619.20010619.CF_v2.grb
TOM_Hindcasts.20080619.20010619.PF_v2.grb.gbx
TOM_Hindcasts.20080619.20010619.CF_v2.grb.gbx

The TOM_REALFORECASTS has 2 types of datasets, the v1_pf.grb type has 3
variables that range forecast F6-360. The v1_cf.grb has the same
3 variables X 51 perturbations X forecast F6-360. As stated previously,
I don't know how the perturbations are distinguished from one another.
I looking into it.

Robb...

On Fri, 5 Jun 2009, John Caron wrote:

Robb Kambic wrote:
Hiya,

As stated before, the NCEP data with multiple grids was split using LDM pqact actions. Since that's not possible for the africa data, the grid_id in the PDS section was used to split the data. But, the africa data had grid_id = 255 for both grids so no split occurred. The data is organized according to forecast time, first grid has forecasts 6-240 and second grid has forecasts 246-360. The first grid has higher resolution then the second grid. I can probably modify a current program to do the split.
yes, you have to split by reading the gds, not through pqact.

There is also a problem with the TOM_REALFORECASTS.20080112_v1_pf.grb grib
what is this dataset?

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.

The other 3 types of ECMWF files don't contain the perturbations so they could be split according to forecast times.

My question, is where do I go from here?
Apparently this is the same problem as in BUFR - local tables. So I suppose we have to get the local tables from ecmwf ?

Robb...



Section 1 - Product Definition Section.
 ---------------------------------------
 Code Table 2 Version Number.               128
 Originating centre identifier.              98
 Model identification.                      130
 Grid definition.                           255
 Flag (Code Table 1)                   10000000
 Parameter identifier (Code Table 2).       167
 Type of level (Code Table 3).                1
 Value 1 of level (Code Table 3).             0
 Value 2 of level (Code Table 3).             0
 Year of reference time of data.              8  (2008)
 Month of reference time of data.             1
 Day of reference time of data.              12
 Hour of reference time of data.              0
 Minute of reference time of data.            0
 Time unit (Code Table 4).                    1
 Time range one.                              6
 Time range two.                              0
 Time range indicator (Code Table 5)          0
 Number averaged.                             0
 Number missing from average.                 0
 Century of reference time of data.          21
 Sub-centre identifier.                       0
 Units decimal scaling factor.                0


ECMWF local usage identifier.               30
 Class.                                       1
 Type.                                       11
 Stream.                                   1035
 Version number or Experiment identifier.  0001


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


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