[CF-metadata] Getting back to ensembles

[Francisco Doblas-Reyes]

Hi,

It seems that the only point from the original message posted by Jonathan
http://www.cgd.ucar.edu/pipermail/cf-metadata/2006/001397.html
is the issue of whether to use the standard_name attribute or to create 
a new type.

Taking into account the type of data we try to encode, I fully support 
his proposal of the variable having "a dimension which serves as an 
index over the members of an ensemble, in which the ensemble members are 
derived from different models, integrations, institutions supplying the 
data, etc., and the data from each ensemble member is a function of the 
same spatio-temporal coordinates and/or other physical independent 
variables".

To provide metadata identifying the members of the multi-forecast system 
ensemble, the option of using "auxiliary coordinate variables (with 
values not necessarily unique or ordered) with the ensemble index 
dimension to contain metadata identifying the institution (string), 
source (string), experiment_id (string) and realization (numeric or 
string) of the data". This agrees quite well with the requirements in my 
original posting:
http://www.cgd.ucar.edu/pipermail/cf-metadata/2006/001147.html
although additional metadata may be required.

We intend to make the string-valued metadata self-describing, and a web 
site will be provided with additional information. The use of a table 
specifying a string-valued "vocabulary" with attributes of the auxiliary 
coordinate variables may require some additional experience and, surely, 
the participation of more forecast institutions.

We plan to make available in the coming days a Thredds server with 
examples of multi-forecast system files using the criteria described 
above (with the standard_name attribute). This might be helpful by 
providing some examples.

Best wishes
Paco
-- 
________________________________________

Francisco J. Doblas-Reyes
European Centre for Medium-Range
Weather Forecasting (ECMWF)
Shinfield Park, RG2 9AX
Reading, UK

Tel: +44 (0)118 9499 655
Fax: +44 (0)118 9869 450
f.doblas-reyes at ecmwf.int
_______________________________________