Hi Antonio-
On 11/6/13 10:02 AM, "Antonio S. Cofiño" wrote:
Just a warning.
The dimension order is not trivial for the CDM. For the time dimesion it
could be has a different meaning.
In my example
float tas(ensemble=5, time1=121, height=1, lat=126, lon=201);
It would be interpreted (implicitly) as Time coordinate axis (forecast
time).
And in your example:
float Total_precipitation(time=1, ens=11, lat=27, lon=51);
It would be interpreted as RunTime coordinate axis. The CDM has the
concept of 2D time coordinates, and the order for dimensions are
non-trivial.
Good point. However, in my case, I use the CF axis attribute (T) on my
time coordinate which explicitly labels it as the time coordinate
instead of the runtime coordinate (which doesn't have support in CF).
So, I should qualify my earlier statement that the CDM doesn't care of
the order as long as you identify the coordinate axes using the CF or
CDM standards (axis or _CoordinateAxisType attributes). The canonical
order for the axes in the CDM is:
(runtime, time, ensemble, z, y, x)
(see ucar.nc2.constants.AxisType)
Looking at the source, at one point, it was:
(runtime, ensemble, time, z, y, x)
So it might be that since time implicitly now comes before ensemble, my
order might work, even without the axis identifier. But it is good
practice to identify the axes explicitly.
Don
--
Antonio S. Cofiño
Grupo de Meteorología de Santander
Dep. de Matemática Aplicada y
Ciencias de la Computación
Universidad de Cantabria
http://www.meteo.unican.es
El 06/11/2013 16:24, Don Murray (NOAA Affiliate) escribió:
All-
This provides an example of the different ways that an ensemble
dimension can be used and that the CDM can handle. For Antonio's
example, the dimension ordering is:
float tas(ensemble=5, time1=121, height=1, lat=126, lon=201);
:_CoordinateAxes = "ensemble time1 height lat lon ";
:standard_name = "air_temperature";
:long_name = "Surface air temperature";
:units = "Celsius";
with ensemble as the leftmost dimension
In the ensemble files I generate, they are:
float Total_precipitation(time=1, ens=11, lat=27, lon=51);
:_FillValue = 9999.0f; // float
:units = "kg m-2";
:long_name = "Total_precipitation_Accumulation (Accumulation for
Mixed Intervals) @ surface";
I put time in the leftmost dimension.
The nice thing is that the CDM does not care! You can structure it
according to your needs.
Don
On 11/5/13 12:59 PM, Cofiño Gonzalez, Antonio Santiago wrote:
Roland,
This is an example with Ensemble coordinate axis
http://www.meteo.unican.es/thredds/catalog/WRFUC/2013110412/catalog.html?dataset=OPERWRF12DatasetScan/2013110412/oper_gfs_mgrama_2013110412_d02.ncml
Antonio S. Cofiño
Santander Meteorology Group
University of Cantabria
El 05/11/2013, a las 16:45, "Roland Schweitzer - NOAA Affiliate"
<roland.schweitzer@xxxxxxxx <mailto:roland.schweitzer@xxxxxxxx>>
escribió:
Hi,
I see hints in the Java netCDF API that it can understand a grid that
has an ensemble axis. What's not clear to me is how one constructs a
netCDF data source (either in the file or via some sort of TDS
aggregation) that represents the ensemble. The CF conventions
document doesn't seem say anything about ensembles.
Google is failing me, can anybody offer some examples or documentation
links for data sources with an ensemble axis?
Thanks,
Roland
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--
Don Murray
NOAA/ESRL/PSD and CIRES
303-497-3596
http://www.esrl.noaa.gov/psd/people/don.murray/
