[CF-metadata] Vertical Coordinate Systems

From: Jonathan Gregory <j.m.gregory>
Date: Mon, 28 Jul 2003 17:03:21 +0100

Dear Juerg

> But why the positive
> attribute? Is the positive attribute not only applicable to 1-dimensional
> coordinate variables?
I think this is something we'll have to decide.

I see what you are getting at with the generalised height coordinate: you
regard Z as a function of model level, x and y, and see this as analogous
to having pressure as a dimensional vertical coordinate being a function of
dimensionless sigma, x and y (via ps), for instance.

However, I still think that a better scheme is to name it in the coordinates
attribute. It can be identified by its standard_name and units if not by a
positive attribute. It isn't really a "function" of model level, x and y in
the sense for which formula_terms was intended. There is no computation
involved - it's just a look-up. I see an auxiliary coordinate variable
Z(zlay,yc,xc) as analogous, for instance, to a 2D longitude variable
longitude(yc,xc).

Cheers

Jonathan
Received on Mon Jul 28 2003 - 10:03:21 BST