[CF-metadata] Example of forecast data

From: Jonathan Gregory <j.m.gregory>
Date: Wed, 23 Jul 2003 08:55:02 +0100

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
Received on Wed Jul 23 2003 - 01:55:02 BST