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To learn about what's going on, see About the Archive Site.
On Wed, 26 Aug 2009, Tor Christian Bekkvik wrote:
Thank You, It helps to know what to look for (GridIndex, GridDefRecord). But It
is still unclear how to get these, given a variable or its Gridset:
mNCdataset = NetcdfDataset.openDataset(this.mFilename, true, null);
mNCgridDataset = new ucar.nc2.dt.grid.GridDataset(mNCdataset);
for (ucar.nc2.dt.GridDataset.Gridset gs :
mNCgridDataset.getGridsets())
{ for (GridDatatype gg : gs.getGrids())
{ VariableEnhanced variable = gg.getVariable();
//gets U and V variables here.
...
(When interpreting and joining U&V variable components, info from
GridDefRecord etc. only gives meaning when associated with these
variables)
Tor, Your are correct the COMPONENT FLAG is not available in the NetCDF API,so I added it yesterday as the GRIB_VectorComponentFlag attribute. The values are either: easterlyNortherlyRelative or gridRelative. Example:
float Categorical_Freezing_Rain_Perturb_pos_surface(time1=64, lat=181,
lon=360);
:units = "";
:long_name = "Categorical_Freezing_Rain_Perturb_pos @ surface";
:missing_value = NaNf; // float
:GRIB_param_discipline = "Meteorological_products";
:GRIB_param_category = "Moisture";
:GRIB_param_name = "Categorical_Freezing_Rain";
:GRIB_param_id = 2, 0, 1, 193; // int
:GRIB_product_definition_type = "Individual ensemble forecast";
:GRIB_level_type = 1; // int
:GRIB_forecasts_in_ensemble = "10";
:GRIB_VectorComponentFlag = "easterlyNortherlyRelative";
float Categorical_Freezing_Rain_Cntrl_low_surface(time1=64, lat=181,
lon=360);
The netCDF-Java 4.1 snapshot release will include this change
in the next day or so. The current plan is for 4.1 to become
our stable release in mid-September.
Robb...
Regards,
Tor C
On Thu, 20 Aug 2009, Robb Kambic wrote:
> On Thu, 20 Aug 2009, Tor Christian Bekkvik wrote:
>
>>
>> Hi,
>> I am using NetCDF to read GRIB/GRIB2 files. Almost everything works
>> fine, but some GRIB parameters seems to be unavailable via the NetCDF
>> API. I this case, I could not find
>> "RESOLUTION AND COMPONENT FLAGS (GDS OCTET 17)" from the GRIB file.
>> , at least not in the NetCDF attributes..
>>
>> (Details: This GDS parameter from the GRIB file tells how to
>> interpret direction from combined U- and V- components. (In my case,
>> current vectors from weather data) Text from GRIB standards
>> documentation:
>>
>> TABLE 7 - RESOLUTION AND COMPONENT FLAGS (GDS OCTET 17):
>> Bit 5:
>> 0 u- and v-components of vector quantities resolved relative
>> to easterly and northerly directions
>>
>> 1 u and v components of vector quantities resolved relative
>> to the defined grid in the direction of increasing x and y
>> (or i and j) coordinates respectively
>>
>> )
>>
>>
>>
>> - How could we get this GRIB parameter ?
>>
>
>
Tor,
The information is available in the CDM stack, ie
GridIndex index;
List<GridDefRecord> hcsList = index.getHorizCoordSys(); for (GridDefRecord gds
: hcsList) {
String windflag = gds.getParam(GridDefRecord.WIND_FLAG)
}
In my first response it was a mistake to move the discussion from the
netCDF-Java library to the lower level GRIB library without an explanation. The
purpose was to show you the code snipet of how the value was obtained.
Hopefully I didn't confuse you.
Robb...
>>
>>
>> Thanks,
>>
>> Tor Chr Bekkvik
>>
>>
>>
>>
>>
>>
>>
>>
>>
>
>==============================================================================
=
> Robb Kambic Unidata Program Center
> Software Engineer III Univ. Corp for Atmospheric
> Research
> rkambic@xxxxxxxxxxxxxxxx WWW: http://www.unidata.ucar.edu/
=============================================================================== Robb Kambic Unidata Program Center Software Engineer III Univ. Corp for Atmospheric Research rkambic@xxxxxxxxxxxxxxxx WWW: http://www.unidata.ucar.edu/ ===============================================================================
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