I was helping
The collaborators of the Mediterranean Forecast System are trying to get
their model output into CF conventions, but they cannot, because they
have a generalized sigma coordinate that varies spatially on their
lon/lat grid. They need the following definition, which is basically
the same as ocean_sigma_coordinate, except that we specify sigma (k,j,i)
instead of just sigma(k):
------------------------------------------------------------------------------------------------------
Ocean generalized sigma coordinate
standard_name = "ocean_generalized_sigma_coordinate"
/Definition:/
z(n,k,j,i) = eta(n,j,i) + sigma(k,j,i)*(depth(j,i)+eta(n,j,i))
where z(n,k,j,i) is height, positive upwards, relative to ocean datum
(e.g. mean sea level) at gridpoint (n,k,j,i), eta(n,j,i) is the height
of the ocean surface, positive upwards, relative to ocean datum at
gridpoint (n,j,i), sigma(k,j,i) is the dimensionless coordinate at
vertical gridpoints (k,j,i), and depth(j,i) is the distance from ocean
datum to sea floor (positive value) at horizontal gridpoint (j,i).
The format for the formula_terms attribute is:
formula_terms = "sigma: var1 eta: var2 depth: var3"
--------------------------------------------------------------------------------------------------------
This would also allow people who use "S-coordinate" models that are more general than the specific functional form adopted in the CF 1.0 "ocean_s_coordinate" to specify their vertical coordinate.
--
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 Tue Dec 21 2004 - 10:33:55 GMT
