As I indicated, I think if we're to be more specific, the standard_name should be something like 'number_of_realizations_at_creation' and the first sentence should finish "within its originally created ensemble".
John On Oct 31, 2014, at 07:50, Hedley, Mark <[email protected]> wrote: > I'm happy to be more specific and stick with > 'original ensemble' > as it meets my use cases just fine. > > So, I think that the proposal stands as: > > standard_name: > number of realizations > > units: > '' > > description: > In a model or operational forecast, the number of member realizations within > a given ensemble. This provides context for any specific realization, for > example orienting a member relative to its original group (even if the group > is no longer intact). > > many thanks > mark > > From: John Graybeal [[email protected]] > Sent: 30 October 2014 23:14 > To: Hedley, Mark > Cc: CF Metadata List > Subject: Re: [CF-metadata] realization | x of n > > Glad you liked the text! > > Regarding 'given ensemble' vs 'original ensemble', how can we resolve the > ambiguity? That is, if you use this attribute, how will the user know what > ensemble the attribute is in reference to? > > If the 'common practice among forecasters' (and required capability) is > exclusively describing the originating ensemble, I propose the name and text > should reflect that narrower definition, to avoid misuse. (I'm hoping for > this case.) > > If the common practice includes both use cases, somehow the user needs to > derive which meaning applies -- either we need to define two standard names, > or suggest in the definition that the variable name or long_name should > resolve it, or something. (We could be deliberately vague as well, but a > sentence like "This could refer to either the original ensemble for this > realization, or a more recent collection in which the realization occurs." > would help make that explicit.) > > John > > On Oct 30, 2014, at 10:44, Hedley, Mark <[email protected]> wrote: > >> Thank you for the feeedback >> >> John: >> I like the text >> In a model or operational forecast, the number of member realizations >> within a given ensemble. This provides context for any specific realization, >> for example orienting a member relative to its original group (even if the >> group is no longer intact). >> I would like to use this as is in the proposal. >> >> > Reviewing this and going back to your original request, there is still a >> > likely point of confusion for users -- it isn't obvious that "given >> > ensemble" refers not to the currently constituted collection, but to the >> > one originally created with this realization. >> >> > If you want that to be the use case for this standard_name (for everyone), >> > I think 'within a given ensemble' needs to explicitly say something like >> > 'within its originally created ensemble'. And perhaps the standard name >> > itself should follow that thought, something like >> > 'initial_number_of_realizations'. >> >> I had thought about this, but my consideration was that there are ensembles >> which are created after the fact, not necessarily in the 'originally >> created' set; e.g. multi-model ensembles. I considered leaving the name so >> that it could be used in this context as well. This is not a strong use >> case for me, so I would be content to be more specific if that is preferred, >> but I didn't see the need to, so I left it more general. I'm happy to be >> guided on this aspect. >> >> >> Jonathan: >> > Maybe you are dealing with an intermediate case, having a subset of the >> > ensemble members, and you want to record how many there originally were in >> > total. Is this a common use case? It seems rather surprising to me. But >> > I'm not sure that's what you mean. >> >> Yes, this is what I mean. I have one of the ensemble members, I have chosen >> it from the collection and passed it to a friend, for reasons best known to >> myself; I want to label it as member x from emsemble of size y. I am >> confidently assured this is common practice amongst forecasters and the >> capability is required. It has been an explicit part of the GRIB >> specification for years. >> >> >> seven of nine >> > But this seems different. It's not the number of members there are, but >> > the ordinal number (7) of this particular member. Why can't that be >> > recorded in a variable with the existing standard_name of realization? >> >> there are two pieces of information here, in CF terms this is: >> realization = 7 >> number_of_realizations = 9 >> I just unpacked this into a single label, to illustrate the information >> wanted (but I seem to have reduced clarity again; never mind). >> >> mark >> >> From: John Graybeal [[email protected]] >> Sent: 30 October 2014 17:10 >> To: Hedley, Mark >> Cc: CF Metadata List >> Subject: Re: [CF-metadata] FW: realization | x of n >> >> Hi Mark, >> >> It is a worry if the definition is a repetition or variant of the words in >> the name. In particular, the word 'realization' will be meaningful to >> modelers/forecasters but not universally. >> >> My first desire was to generalize the term (e.g., 'how many entities are in >> a collection of that type of entity'), but I suspect that will be annoying >> to the primary users. So can we make it specific and say >> In a model or operational forecast, the number of member realizations >> within a given ensemble. This provides context for any specific realization, >> for example orienting a member relative to its original group (even if the >> group is no longer intact). >> Or else, define what we mean by 'realization' and 'ensemble'. >> >> Reviewing this and going back to your original request, there is still a >> likely point of confusion for users -- it isn't obvious that "given >> ensemble" refers not to the currently constituted collection, but to the one >> originally created with this realization. >> >>> In my use case, the whole ensemble is not present, I only have a subset of >>> the members. I have a metadata element telling me how many members there >>> were at the time the ensemble was created, which I would like to encode. >> >> >> If you want that to be the use case for this standard_name (for everyone), I >> think 'within a given ensemble' needs to explicitly say something like >> 'within its originally created ensemble'. And perhaps the standard name >> itself should follow that thought, something like >> 'initial_number_of_realizations'. >> >> John >> >> >> ______________________________________ >> From: CF-metadata [[email protected]] on behalf of Jonathan >> Gregory [[email protected]] >> Sent: 30 October 2014 16:40 >> To: [email protected] >> Subject: [CF-metadata] FW: realization | x of n >> >> Dear Mark >> >> > Please may people raise any further concerns about a new standard name: >> > number_of_realizations >> > with a canonical unit of >> > '' >> > and a description of >> > The number of member realizations within a given ensemble. >> >> My concern is probably the same one as before. Sorry about that. Does this >> mean the number of members the ensemble has got? If it does, why does it >> differ >> from the ensemble dimension? If the ensemble dimension has been collapsed to >> size 1, we could record this in cell_methods. Maybe you are dealing with an >> intermediate case, having a subset of the ensemble members, and you want to >> record how many there originally were in total. Is this a common use case? >> It seems rather surprising to me. But I'm not sure that's what you mean. >> >> > This name enables a single member from an ensemble to explicitly be >> > labelled, e.g. >> > seven_of_nine >> > which is often required in operational forecasting. >> >> But this seems different. It's not the number of members there are, but the >> ordinal number (7) of this particular member. Why can't that be recorded in a >> variable with the existing standard_name of realization? >> >> Cheers >> >> Jonathan >> _______________________________________________ >> CF-metadata mailing list >> [email protected] >> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >> >> >> On Oct 30, 2014, at 01:40, Hedley, Mark <[email protected]> wrote: >> >>> Thank you for the discussion on the number of realizations in an ensemble. >>> >>> Please may people raise any further concerns about a new standard name: >>> number_of_realizations >>> with a canonical unit of >>> '' >>> and a description of >>> The number of member realizations within a given ensemble. >>> >>> This name enables a single member from an ensemble to explicitly be >>> labelled, e.g. >>> seven_of_nine >>> which is often required in operational forecasting. >>> >>> I would like this to be added to the standard name list. >>> >>> thank you >>> mark >>> _______________________________________________ >>> CF-metadata mailing list >>> [email protected] >>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >> >> _______________________________________________ >> CF-metadata mailing list >> [email protected] >> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
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