Dear Jonathan and Brian,
I hadn't thought about the introduction of an index dimension to describe
the length of 'time' and 'validity time'. I assume you mean something like:
dimensions:
time_index = 4 ;
variables:
double time(time_index);
double forecast_time(time_index);
float myvar(lat, lon, time, forecast_time);
If that is what you mean I think it is wise because it forces the length of
time and forecast_validity_time to be identical.
Kind regards,
Ag
> -----Original Message-----
> From: Jonathan Gregory [mailto:j.m.gregory at reading.ac.uk]
> Sent: 23 July 2003 08:55
> To: cf-metadata at cgd.ucar.edu
> Subject: [CF-metadata] Example of forecast data
>
>
> Dear Brian and Ag
>
> To me, labelling time as "reference" or "validity" simply
> appears to be adding
> precision - both concepts, not just the validity time, are
> associated with the
> process of making a forecast and they need to be
> distinguished. If we call the
> validity time just "time" and the reference time
> "forecast_reference_time"
> this is a bit asymmetrical. However, I do accept that the
> validity time is
> "more like" plain time - your proposal is analogous to having
> coordinates of
> air_pressure and reference_air_pressure (which we haven't yet
> defined as a
> standard name, but might need) for air_potential_temperature.
> Therefore I would
> be happy with not defining forecast_validity_time as a
> standard name and using
> plain time for it. People using the data will see the
> forecast_reference_time
> explicitly labelled and deduce, "Ah, in that case the one
> called just 'time'
> must be the validity time."
>
> Are we all agreed now on how to handle forecast time axes? I
> think we have
> identified two structurally different cases. If validity time
> and analysis
> time, or both, are single-valued, we have independent
> coordinates for them
> (not necessarily requiring dimensions of size one if we
> follow the proposal
> in the other thread). If they are both multivalued, we
> introduce an index
> dimension and make them both one-dimensional auxiliary
> coordinate variables
> with this dimension.
>
> Best wishes
>
> Jonathan
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Received on Wed Jul 23 2003 - 10:16:58 BST
