Where the 5th dimension allows for multiple levels I meant to say.
The files NCAR produces for TIGGE are all on one fixed level, with one
fixed forecast initialization time.
Doug
On Mar 16, 2010, at 5:16 PM, Doug Schuster wrote:
> John,
>
> I think the standard names and basic template are all the same. The
> only difference is that
> the structure we're using for TIGGE has 4 variable dimensions vs 5,
> where the 5th allows for multiple forecast initialization times.
>
> On Mar 16, 2010, at 3:43 PM, John Caron wrote:
>
>> Hi Doug:
>>
>> Looks to be the same as Paco's. Do you know what was modified?
>>
>> On 3/16/2010 1:46 PM, Doug Schuster wrote:
>>> NCAR uses a modified version of Paco's file structure for TIGGE
>>> output.
>>> All ensemble members found in the file require the same "single"
>>> model initialization time, the same forecast timesteps, and
>>> identical grids types.
>>>
>>> A sample file can be found at:
>>>
>>> http://dss.ucar.edu/download/tigge/ncep_20100223000000_tp_lev_255_id_528.1.5deg.nc
>>>
>>> Here's a snippet from the file header metadata -Doug:
>>>
>>> dimensions:
>>> longitude = 240 ;
>>> latitude = 121 ;
>>> string4 = 4 ;
>>> string2 = 2 ;
>>> time = 4 ;
>>> realization = 21 ;
>>> variables:
>>> float longitude(longitude) ;
>>> longitude:data_type = "float" ;
>>> longitude:units = "degrees_east" ;
>>> longitude:axis = "X" ;
>>> longitude:standard_name = "longitude" ;
>>> longitude:valid_min = 0.f ;
>>> longitude:valid_max = 358.5f ;
>>> float latitude(latitude) ;
>>> latitude:data_type = "float" ;
>>> latitude:units = "degrees_north" ;
>>> latitude:axis = "Y" ;
>>> latitude:standard_name = "latitude" ;
>>> latitude:valid_min = -90.f ;
>>> latitude:valid_max = 90.f ;
>>> int time(time) ;
>>> time:data_type = "int" ;
>>> time:units = "hours since 1950-01-01 00:00:00" ;
>>> time:standard_name = "time" ;
>>> time:long_name = "Forecast Valid Time" ;
>>> int realization(realization) ;
>>> realization:data_type = "int" ;
>>> realization:units = "1" ;
>>> realization:standard_name = "realization" ;
>>> realization:long_name = "Number of the simulation in the
>>> ensemble" ;
>>> char forecast_type(realization, string2) ;
>>> forecast_type:data_type = "char" ;
>>> forecast_type:long_name = "Forecast type" ;
>>> char institution(realization, string4) ;
>>> institution:data_type = "char" ;
>>> institution:standard_name = "institution" ;
>>> institution:long_name = "Institution responsible for the
>>> forecast system" ;
>>> char source(realization, string4) ;
>>> source:data_type = "char" ;
>>> source:standard_name = "source" ;
>>> source:long_name = "Method of production of the data" ;
>>> char experiment_id(realization, string4) ;
>>> experiment_id:data_type = "char" ;
>>> experiment_id:standard_name = "experiment_id" ;
>>> experiment_id:long_name = "Experiment identifier" ;
>>> int perturbation_method(realization) ;
>>> perturbation_method:data_type = "int" ;
>>> perturbation_method:long_name = "Perturbation method, GRIB-2
>>> Code table 4.6" ;
>>> float tp(time, realization, latitude, longitude) ;
>>> tp:data_type = "float" ;
>>> tp:units = "kg m-2 s-1" ;
>>> tp:standard_name = "precipitation_amount" ;
>>> tp:level_name = "Ground or water surface " ;
>>> tp:level_units = "unknown" ;
>>> tp:level_value = 0.f ;
>>> tp:coordinates = "institution forecast_type source
>>> experiment_id perturbation_method" ;
>>> tp:_FillValue = 9.96921e+36f ;
>>>
>>> // global attributes:
>>> :Model_Initialization_Date_and_Time_UTC = "2010-2-23 0 UTC" ;
>>> :Conventions = "CF-1.0" ;
>>> :Institution = "NCAR" ;
>>> :Generator = "grib2_to_netcdf" ;
>>> :Created = "Wed Mar 03 04:37:58 2010" ;
>>> :Title = "TIGGE" ;
>>> :References = "For TIGGE, check http://tigge.ucar.edu" ;
>>>
>>> On Mar 16, 2010, at 1:31 PM, V. Balaji wrote:
>>>
>>>> Jonathan Gregory writes:
>>>>
>>>>> Dear John
>>>>>
>>>>>> Im not sure if we ever converged on how to write ensemble files.
>>>>> No, we didn't. If I remember correctly, we couldn't agree on the
>>>>> relationship
>>>>> between attributes and coordinates, and that was a sticking-
>>>>> point. I thought
>>>>> that we ought to allow multivalued auxiliary coord variables for
>>>>> ensemble
>>>>> axes, corresponding to attributes that might be used to describe
>>>>> a single
>>>>> model. I would give these standard_names to identify them. Paco
>>>>> started the
>>>>> discussion, and in the end he made his own decisions for what to
>>>>> do for the
>>>>> ENSEMBLES project (because CF had not concluded), so he might
>>>>> comment on it.
>>>>
>>>> http://ensembles.ecmwf.int/thredds/ensembles/stream2/seasonal/atmospheric/catalog.html
>>>>
>>>> has examples of how Paco has it set up.
>>>> (esp see the "mother of all aggregations" :-).
>>>>
>>>> It requires the ensemble to share the same space and time
>>>> discretization.
>>>>
>>>>>
>>>>>> Particularly, how does software recognize the ensemble dimension?
>>>>> We didn't agree. But at the end of the discussion, Steve also
>>>>> suggested that
>>>>> it could be identified by an axis attribute, just as you have. I
>>>>> like that
>>>>> idea too. But it could also be given a standard name, like other
>>>>> coordinate
>>>>> variables e.g. ensemble_member_identifier. I suppose the values
>>>>> of this
>>>>> coord var might be either numeric or strings, though it your
>>>>> example it is
>>>>> integer. I haven't looked at the trac ticket to see if we
>>>>> discussed these
>>>>> points before.
>>>>>
>>>>>> Perhaps we should add :axis = "Ensemble" to the model
>>>>>> coordinate variable?
>>>>> I'd suggest lower case, like most CF keywords. The other axis
>>>>> attributes are
>>>>> all single letters (X Y Z T) but I don't think it would be a
>>>>> problem to use
>>>>> a word.
>>>>>
>>>>> Best wishes
>>>>>
>>>>> Jonathan
>>>>> _______________________________________________
>>>>> CF-metadata mailing list
>>>>> CF-metadata at cgd.ucar.edu
>>>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>>>>>
>>>>
>>>> --
>>>>
>>>> V. Balaji Office: +1-609-452-6516
>>>> Head, Modeling Systems Group, GFDL Home: +1-212-253-6662
>>>> Princeton University Email: v.balaji at noaa.gov
>>>> _______________________________________________
>>>> CF-metadata mailing list
>>>> CF-metadata at cgd.ucar.edu
>>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>>
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>
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Received on Tue Mar 16 2010 - 17:19:22 GMT
