[CF-metadata] new vertical coordinate

[V. Balaji]

I have usually seen Gal-Chen defined as

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

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.

Jonathan Gregory writes:

> Dear Beate
>
>>> Dear cf-metadata,
>>> I proposed to include following (not dimensionless) vertical coordinate to
>>> cf-conventions:
>>>
>>>
>>> Atmosphere Gal-Chen height coordinate (after Gal-Chen and Somerville,
>>> 1975)
>>> standard_name = "atmosphere_gal-chen_height_coordinate"
>>> Definition:
>>> z(n,k,j,i) = zs(j,i) + gal-chen(k)*(1-ztop/zs(j,i))
>
> Maybe it should be zs/ztop? In that case I think this would be a special
> case of the hybrid height coordinate, which already defined as
>
> z=a(k)+b(k)*zs
>
> Jonathan
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-- 

V. Balaji                               Office:  +1-609-452-6516
Head, Modeling Systems Group, GFDL      Home:    +1-212-253-6662
Princeton University                    Email: v.balaji at noaa.gov