Hello, In the original proposal for an ensemble like axis we used the standard_name 'realization' because it included things that weren't obviously model ensembles - they may be forecasts or projections generated by statistical methods - but that could be handled in a way similar to model ensembles. The paper: http://www.climateprediction.net/wp-content/publications/nature_allen_051000.pdf is an example of this sort of technique.
The use of 'realization' has been questioned before on this list - so I'd be very happy to review its use. If 'ensemble' is more familiar and useful then that would be fine. (I think this can be handled with aliases - is that right?) I think there is a complication with ensemble based statistics (sorry I haven't followed this latest thread close enough to know whether it has been talked about). You often weight each ensemble memember e.g. based on some estimate of that ensemble member's likelihood - before calculating the ensemble statistic. I think there is a thread somewhere like http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2007/046103.html which discussed this previously. Now apologies: in my usual useless style on this list - I probably won't manage to follow this up in any detail - but since Jonathan mentioned me I thought I needed to try to fill in some background. Jamie > -----Original Message----- > From: Jonathan Gregory [mailto:[email protected]] > Sent: 15 November 2013 17:09 > To: [email protected] > Cc: [email protected]; Steve Hankin; Kettleborough, > Jamie; Hedley, Mark > Subject: [CF-metadata] Standardizing how ensemble > (realization) axes are encoded > > Dear all > > This is partly a reply to various off-list emails. > > I don't believe that the current CF standard says anything > specifically about > ensemble axes. We did discuss introducing axis="E" but that > wasn't adopted. The > axis attribute is generally redundant (the same came be > deduced from mandatory > units, positive att or standard_name). I think it would be > better to use the > standard_name to indicate an ensemble axis, whether collapsed or not. > > Jamies Kettleborough has reminded us that we introduced the > standard_name of > realization for ensemble members. (I did have a memory of > that, but I searched > the table for a spelling with S rather than Z!) So I withdraw > my suggestion of > new standard names for this. I think that the existing > convention permits a > cell_methods entry of "realization: METHOD", when there is no > dimension named > "realization", to indicate that an ensemble axis has been > collapsed using > the METHOD stated. In the case where a cell_methods entry > gives a name that is > not a dimension name, it's interpreted as a standard name, > and it means "over > all available values". > > Cheers > > Jonathan > _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
