[CF-metadata] Proposal for better handling vector quantities in CF

From: Jonathan Gregory <j.m.gregory>
Date: Fri, 9 Dec 2011 18:37:16 +0000

Dear John

I prefer the idea that Thomas has put forward of an umbrella, rather than
containing the vector/tensor components in one data variable, because

* I really don't like the idea of units being mixed within a data variable.
I think things with different units must certainly be different quantities
and could not be regarded as the same field. You can get away with it if they
are all m s-1, for instance, but not so easily if the vertical one is orders
of magnitude different from the horizontal, and not at all if the vector is
expressed in polar coordinates.

* I think it would be very inconvenient, and would break a lot of existing
software, if the coordinates were not what they appeared to be, because an
offset had to be added. Also, in general, the component fields of a staggered
grid do not have the same dimensions, as well as differing in the coordinates.

* It avoids the need to define a convention for labelling vector/tensor
components.

* It is completely backwards-compatible as regards the component fields, which
are exactly as before; we're just adding some separate information linking
them. This seems neat to me.

Best wishes

Jonathan
Received on Fri Dec 09 2011 - 11:37:16 GMT