Hi Don,
I'm not quite fan of the FMRC. Basically at the beginning they are cool
and in many cases are enough, functional and efficient.
The problem that I usually face, with FMRC, is when I wan a fine grain
control on how data it's been aggregated, and I'm finish building my
ad-hoc ncml aggregations.
With respect to time coordinates with "special" calendars, the
netcdf-java it's good handling them:
https://docs.unidata.ucar.edu/netcdf-java/5.2/javadoc/ucar/nc2/time/Calendar.html
but sometimes the TDS has issues with those kind on "non-standard"
calendars. I think FMRC is one of that cases, but is a guess.
Regards
Antonio
On 24/4/20 16:41, Don Murray via netcdf-java wrote:
Thanks again, Antonio. The ECMWF link is very helpful.
Do you know if the FMRC can handle a calendar attribute on the time?
I'm dealing with monthly data and would like to "use months since"
with a 360day calendar (I know months since is frowned upon, but with
a 360day calendar, it's a fixed 30day period).
Thanks again for your help. I'll let you know if I have more questions.
Don
On 4/23/20 2:09 PM, Antonio S. Cofiño wrote:
Hi Don,
Yes you need to register into the system, because some datasets are
restricted. If you want to access please sign-up
http://meteo.unican.es/udg-tap/
and let me know. I can provide you a temporal access.
Although the dataset it's encoded in GRIB1 format, it's been exposed
as one "netcdf" entity, with all variables and coordinates. Attached
you can find the resulting CDL for the "netcdf" entity.
For this dataset the realization coordinate was not recognized by the
netcdf-java I have had to impose it and create all aggreagtions, also
on the runtime coordinate.
If you want a Guide about encoding products you may be find
interesting this guide:
https://confluence.ecmwf.int/display/COPSRV/Guide+to+NetCDF+encoding+for+C3S+providers
Let me know if that helps
Regards
Antonio
On 22/4/20 22:28, Don Murray via netcdf-java wrote:
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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