Mark,

I don't think there is any real need for a number_of_realizations attribute or standard name. The size of the dimension associated with the coordinate variable associated with the 'realization' standard name provides the number of realizations. If the coordinate variable with this standard name is a scalar, then the number is, by implication, one. Here are a couple of examples:

1)
dimensions:
    realize = 3;
    strlen = 50;
    lat = 720;
    lon = 1440;

variables:
    float meas(realize, lat, lon);
        ...

    lat(lat);
        ...

    lon(lon);
        ...

    char realize(realize, strlen);
        standard_name = "realization";

2)
dimensions:
    strlen = 50;
    lat = 720;
    lon = 1440;

variables:
    float meas(lat, lon);
        coordinates = "realize";
        ...

    lat(lat);
        ...

    lon(lon);
        ...

    char realize(strlen);
        standard_name = "realization";

Grace and peace,

Jim

On 10/3/14, 6:52 AM, Hedley, Mark wrote:
Hello CF

The standard name
  realization
is available for use:
Realization is used to label a dimension that can be thought of asa statistical sample, e.g., labelling members of a model ensemble.

It is common practice in forecasting and some forecasting formats to explicitly state the number of members an ensemble contained.

This would be generally be expected to be a single value across an ensemble collection. As such I am not sure that a standard name and a coordinate would be the most useful way to encode this piece of information.

Thus, we could look to provide a new data variable attribute, something like
  number_of_realizations
to store this metadata.

However it is not impossible for this to vary across some coherent data set so perhaps a standard_name of
  number_of_realizations
would be a sensible approach, even if in most cases this would be a scalar coordinate

Please may I ask for some opinions on this matter?

thank you
mark


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