[CF-metadata] CF and multi-forecast system ensemble data

From: Jonathan Gregory <j.m.gregory>
Date: Wed, 18 Oct 2006 13:15:57 +0100

Dear Paco

----- Forwarded message from Francisco Doblas-Reyes <Francisco.Doblas-Reyes at ecmwf.int> -----

> A NetCDF file with multi-forecast system ensemble data requires, at
> least, the experiment id to be a dimension of the file. For instance,
> ensembles generated with different models, which are part of the same
> multi-model ensemble forecast, need to be identified in case the user
> wishes to give different weights to the models or needs to bias correct
> them separately. That is the reason why the information can not be
> encoded as global attributes and we require the new standard names.

For that purpose, perhaps you could use the new standard name of realization,
which was recently added for a similar purpose. To quote from Alison's posting:

realization; 1; realization is used to label a dimension that can be thought of
as a statistical sample, e.g., labelling members of a model ensemble.

This is expected to be a dimensionless number. If you need to use strings,
we probably need a different standard name.

> Concerning the use of time coordinates, we can try to use two variables
> (reftime and leadtime) with standard names forecast_reference_time and
> forecast_period but using a single time dimension, as in your example of
> structure (b). I prefer the use of forecast_period because it makes more
> obvious that we are dealing with forecasts.

That makes sense to me. If structure (b) is acceptable to you, I am happy.

Best wishes

Jonathan
Received on Wed Oct 18 2006 - 06:15:57 BST