Hi all,
I'm still curious about something:
Suppose we have the temperature field stored from one member of an
ensemble of size 10. We want to make the size of the ensemble known to
the user. We store 10 as a scalar variable with standard name
"ensemble_size", but how does that scalar get associated with our
temperature variable (other than it having being stored in the same file)?
cheers,
Karl
On 7/22/15 1:59 AM, Hedley, Mark wrote:
Hello John, Karl et al
I'm not sure I agree with John's last statement. I think that an
ensemble is a defined collection of members, so my need is the need
for ensemble size to be defined explicitly.
The distinction that not all members may be present characterises the
need for this metadata descriptor, rather than just using the
dimension size of realization, which does not meet my requirement.
On reflection, I think that I prefer Karl's name of 'ensemble_size'
To restate my use case, I have a data set from an ensemble, where
there is a coordinate variable called 'realization'. Let's say there
are 23 members, this dimension is size 23.
I want to reference the number of members in the ensemble, whilst
sub-setting the data variable in various ways.
The suggestion is to add a scalar coordinate to my original dataset,
which contains the number of members in the ensemble. Then any
sub-setting operation will retain this coordinate, and I will always
be able to state that this member is member 0 of 23, 5 of 23 etc
One requirement I have is to slice this variable, to result in a 2D
data array, 2 1D coordinate variables: latitude and longitude; with
all other coordinates as scalars.
If it is reasonable to talk about an ensemble as a defined collection
of members, then I agree with Karl, that a standard_name of
'ensemble_size' fits the bill. The description fits my use case nicely
many thanks
mark
------------------------------------------------------------------------
*From:* CF-metadata [[email protected]] on behalf of
John Graybeal [[email protected]]
*Sent:* 22 July 2015 05:52
*To:* Karl Taylor
*Cc:* CF Metadata List
*Subject:* Re: [CF-metadata] original_ensemble_size
Karl,
To my understanding (then and now), the use case is explicitly not
what your definition describes. The entire point of the request was to
provide a label that was clearly distinguished from the typical
concept of ensemble size.
John
On Jul 21, 2015, at 16:36, Karl Taylor <[email protected]
<mailto:[email protected]>> wrote:
Dear all,
I wonder if the following might also meet requirements of the use case:
name: *ensemble_size*
*
*
description: The number of member realizations in an ensemble. This
name provides context for any specific realization, which might not
be co-located with the other members of the ensemble.
Karl
On 7/20/15 9:49 PM, John Graybeal wrote:
To save others the lookup, the use case phrasing that Mark signed on
to were these words: "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." The entire
thread is titled 'realization | x of n', but it is pretty, umm, rich
with detail.
The last email before discussion went silent appears to be mine:
Modified to fit Mark's use case, I think suitable text is:
name: *original_ensemble_size*
*
*
description: The number of member realizations in the originally
constituted 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).
This does not mention forecasting, preserves the origination
concept, and gives a bit of context, without constraining the
application. It could even be an ensemble of observations, or cat
videos, or ... you get the idea.
I will let someone else provide the example of how that is
associated with the variable, it will be more authoritative!
John
On Jul 20, 2015, at 14:42, Karl Taylor <[email protected]
<mailto:[email protected]>> wrote:
Hi Mark,
I didn't quite understand how the standard name gets associated
with a variable (containing 1 or more realizations from the
ensemble). Someone said it was through a scalar coordinate
variable, but I don't see how the ensemble member is a function of
the ensemble size, so why would this be appropriate?
Could you supply an example?
Also, I didn't follow why "original" was included in "original
ensemble size". Surely, you wouldn't report this number unless you
thought the ensemble size was pretty much set and wouldn't change.
In that case there shouldn't be a need for a "modified ensemble
size", so wouldn't "ensemble size" suffice?
thanks,
Karl
On 7/20/15 9:24 AM, Hedley, Mark wrote:
Hello CF
Late last year we had a discussion about storing
original_ensemble_size
in a CF file
http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2014/thread.html#57756
There were a few options discussed, with John Graybeal making the
suggestion
original_ensemble_size
/description: The number of members constituting an ensemble./
for a new standard_name definition, which seemed to fit the case
very well
It does not seem to have been adopted into the standard names list
as yet.
Please may this name and definition be adopted, or reasons not to
detailed here?
thank you
mark
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