CF folk:
To my chagrin, I just recently realized two things that should be
fixed with the CF 1.0 convention with regard to the handling of
dimentionless vertical coordinates in ocean models.
1. I discovered that "ocean s-coordinate" transformation I supplied is
overly
restrictive. Here is what exists in the CF 1.0 standard:
standard_name = "ocean_s_coordinate"
/Definition:/
z(n,k,j,i) = eta(n,j,i)*(1+s(k)) + depth_c*s(k) +
(depth(j,i)-depth_c)*C(k)
C(k) = (1-b)*sinh(a*s(k))/sinh(a) +
b*[tanh(a*(s(k)+0.5))/(2*tanh(0.5*a)) - 0.5]
with
formula_terms = "s: var1 eta: var2 depth: var3 a: var4 b:
var5 depth_c: var6"
------------------------------------------------------------------------------------------------------------
But C(k) can be any monotonic function from 0 to 1, not just this
function with
specific sinh and tanh functions. The C(k) should be input, not a, b
and the function.
I would therefore like to replace the existing CF1.0 definition with this:
standard_name = "ocean_s_coordinate"
/Definition:/
z(n,k,j,i) = eta(n,j,i)*(1+s(k)) + depth_c*s(k) +
(depth(j,i)-depth_c)*C(k)
with
formula_terms = "s: var1 eta: var2 depth: var3 C: var4
depth_c: var5"
How best to go about this? I would bet that the IDV is the only
application
that has used the "ocean s-coordinate", so one option would be to just
switch it
immediately and tell the IDV folk, no? (treat it like a bug, even though
is really isn't a bug).
Alternatively, we could come up with a new name like "ocean
s2-coordinate", but
this seems silly since "ocean s-coordinate" would be a subset of the new
one.
2) I realized that "ocean sigma-coordinate" is just a subset of "ocean
s-coordinate"
(If C(k) is specified to be the same as s(k)). Should we therefore
eliminate ocean s-coordinate?
Thanks,
Rich
--
Richard P. Signell rsignell at usgs.gov
U.S. Geological Survey Phone: (508) 457-2229
384 Woods Hole Road Fax: (508) 457-2310
Woods Hole, MA 02543-1598
Received on Mon Oct 25 2004 - 14:56:19 BST
