Re: [netcdf-java] Storing forecast ensembl model data in netCDF

Thanks, Antonio. With GRIB it seems straight forward. I have netCDF files that I'm trying to use and am tryint to figure out how to structure them. Are any of the datasets on your site backed by netCDF instead of GRIB? Looks like I need a user/pass to get in to see the details.

Don

On 4/22/20 1:17 PM, Antonio S. Cofiño wrote:
Hi Don,

On 4/22/20 5:24 PM, Don Murray via netcdf-java wrote:
Hi All-

I'm looking at storing forecast model data (NMME and GEFS) in netCDF format and am wondering if anyone out there is doing that and using netcdf-java to access and subset.

Yes. You can take a look at:

https://meteo.unican.es/trac/wiki/udg/ecoms/dataserver/catalog

In particular System4, CFSv2 and glosea5 datasets which corresponds to different seasonal forecasts systems.


For GRIB data, netcdf-java/THREDDS uses a 2D time dimension with dimensions (reftime, time, ens, lat, lon) where time is stored as time(reftime, time). I'm looking for examples that use netCDF as the storage format, particularly if they are served up via THREDDS.  I'm using the ucar.nc2.dt.grid classes to read netCDF files at the present.

In particular we are using netcdf-java for accessing data from client side and TDS from server side to aggregate data in common datasets.

In the attached files you can find the opendap info for on of the datasets which includes "realization" coordinate and 2D time, among level, lat and lon coordinates (level it's a particular case).

https://www.unidata.ucar.edu/software/netcdf-java/v4.3/v4.2/javadocAll/ucar/nc2/ft/grid/Grid.html#makeSubset(ucar.ma2.Range,%20ucar.ma2.Range,%20ucar.ma2.Range,%20ucar.ma2.Range,%20ucar.ma2.Range,%20ucar.ma2.Range)

The client use de makeSubset method from the Grid object which allows to subset along the realization coordinate and 2D time:

https://www.unidata.ucar.edu/software/netcdf-java/v4.3/v4.2/javadocAll/ucar/nc2/ft/grid/Grid.html

The dataset are the original GRIB1 files aggregated using netcdf-java ncml aggregation and published it by TDS.

This is been used from a different R packages we developed, but in particular the central part it's the loadeR which interacts directly with the netcdf-java API (by rJava):

https://github.com/SantanderMetGroup/loadeR

You have some academic reference and use cases there.

Please, let me know if you need more info.

Regards

Antonio


--
Antonio S. Cofiño
Dep. de Matemática Aplicada y
         Ciencias de la Computación
Universidad de Cantabria
http://www.meteo.unican.es


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--
Don Murray
NOAA/PSL and CU-CIRES
303-497-3596
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