[CF-metadata] downward_air_velocity

From: Jonathan Gregory <j.m.gregory>
Date: Fri, 12 Sep 2014 13:44:16 +0100

Dear Ben

> > It imposes a small cost by increasing the number of standard_names that
> > have to be defined, but it's very easy to agree such pairs of standard_names,
>
> If I could have a say on this, I would prefer that the standard chooses just one. Having the possibility of a dual set of names only serves the purpose of complicating implementation of anything trying to parse the data. Flipping the sign of a value is a trivial task, both for the writer and reader, so doing that to satisfy a "simpler standard" is IMHO likely to be a cheaper option than dealing with the increased namespace. This generally would not cause any precision issues with the values being stored either.

That's a reasonable point of view which has been argued before. We have not
done that because we don't see as the role of CF to prescribe what data should
be stored, only to provide ways to describe it. If we tried to be prescriptive,
it might either (a) prevent people from using CF, or (b) using it incorrectly,
because it didn't quite fit their needs, but they didn't want to change how
they did things.

However, in practice most projects which generate CF data (like CMIP) have
their own further conventions, which usually do prescribe more precisely what
should be stored, in terms of standard names. So for any particular project
your preference above is met, but it may differ from project to project.

Best wishes

Jonathan
Received on Fri Sep 12 2014 - 06:44:16 BST