[CF-metadata] new vertical coordinate

From: Jonathan Gregory <j.m.gregory>
Date: Fri, 30 Jun 2006 13:31:24 +0100

Dear Balaji and Beate

> gal-chen(k) = ztop*( z(k,j,i)-zs(j,i) )/( ztop-zs(j,i) )

gal_chen * (1-zs/ztop) = z - zs

so z = zs(i,j)(1 - gal_chen(k)/ztop) + gal_chen(k)

which is a particular case of the hybrid-height coordinate

z = a(k) + b(k)*zs(i,j)

where the Gal-Chen coordinate and ztop determine a and b together.

> ztop is required to lie above all topography (zs), so no singularity.
> when z=zs, gal-chen=0 (terrain-following gal-chen isoline);
> when z=ztop, the gal-chen isoline is at constant height also.

a=0 and b=1 for terrain-following levels, a=const and b=0 for altitude levels.

Hence I don't think we need a new coordinate, just a new formula giving a and
b in terms of gal-chen and ztop, which might supplied as an alternative for
a and b in the case of hybrid height.

Cheers

Jonathan
Received on Fri Jun 30 2006 - 06:31:24 BST