[CF-metadata] Request for new standard name for components ofplatform_speed_wrt_ground

From: Jonathan Gregory <j.m.gregory>
Date: Wed, 31 Aug 2011 10:44:09 +0100

Dear Nan

> Water velocities are defined more consistently, with eastward_
> northward_ and upward_sea_water_velocity having parallel names/
> definitions, and allowing the e/n terms to be used with or without
> a vertical component.
...
> I think the latter is a better way to handle platform motion,
> because it's more flexible and consistent. It does put the onus
> on the user to look for a vertical component if they're going to
> calculate speeds

I agree with this. The definitions of the E/N components should not imply
that there is, or is not, a vertical component too.

> The treatment of air velocity - wind - in CF is a little bit
> problematic, IMHO; wind is assumed to be a 2D vector.
> If you have a 3-component air velocity record, I'm not sure how you're
> supposed to record the e/n components in CF.

You use eastward wind, northward wind, and upward air velocity. I think the
use of these terms is what you advocate, and the confusing thing is the
definition of "wind": "Wind is defined as a two-dimensional (horizontal) air
velocity vector, with no vertical component." I think what this means is that
we don't use the word "wind" for the vertical component, that's all. This
situation arises because this was a case when the standard_name table adopted
the common term i.e. wind. If we had said "air velocity" for all components
we wouldn't have had the problem. As you know, when we assign standard names
it can be an awkward choice between a term normally used and a longer, more
consistent and self-explanatory term.

Best wishes

Jonathan
Received on Wed Aug 31 2011 - 03:44:09 BST