hybrid S-Z coordinates?

[esatel]

Hi all,

Does anyone have a suggestion as to how to represent hybrid coordinates (S-Z, with Z in the bottom) in the new standard as in SELFE? I have seen posting that included this as a topic but I did not see any resolution of the issue.

 

Thanks,

Eli

[Bert Jagers]

Hi Eli,

The new standard uses the same conventions for the vertical coordinate
as the standard CF-conventions.
This means that you have basically two options:
1) Explicitly specify the vertical coordinates for all points and
layers, e.g. z(nnodes,nlayers).
2) Use a CF formula for the vertical coordinates; do you mean S or
sigma? If you mean sigma then the ocean_sigma_z_coordinate does what you
need. If you mean S then you need to contact the CF community to define
a convention for ocean_s_z_coordinate.

Cheers,

Bert
-----

> --
> You received this message because you are subscribed to the Google
> Groups "UGRID Interoperability" group.
> To view this discussion on the web visit
> https://groups.google.com/d/msg/ugrid-interoperability/-/lAI_Rsn3X5wJ.
> To post to this group, send email to
> ugrid-inter...@googlegroups.com.
> To unsubscribe from this group, send email to
> ugrid-interoperab...@googlegroups.com.
> For more options, visit this group at
> http://groups.google.com/group/ugrid-interoperability?hl=en.





DISCLAIMER: This message is intended exclusively for the addressee(s) and may contain confidential and privileged information. If you are not the intended recipient please notify the sender immediately and destroy this message. Unauthorized use, disclosure or copying of this message is strictly prohibited.
The foundation 'Stichting Deltares', which has its seat at Delft, The Netherlands, Commercial Registration Number 41146461, is not liable in any way whatsoever for consequences and/or damages resulting from the improper, incomplete and untimely dispatch, receipt and/or content of this e-mail.

[Bert Jagers]

Hi all,

Triggered by Eli's question I just noticed that the
ocean_sigma_z_coordinate requires that the layers are numbered positive
down (since the layers k<=nlayers are defined to be on top; see the
section on
http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.6/apd.html). How
common is this numbering convention actually? We have a long lasting
in-house discussion about layer numbering order. We have in-house model
codes that

a) count layers positive increasing down (k = 1 at surface, k = kmax
near bed) - sigma layer code
b) count layers positive increasing up (k = 1 bottom most layer, k =
kmax topmost layer) - z layer code

and I remember that other codes may

c) count layers negative increasing up (k = -kmax near bed, k = -1 at
surface)

- For simulation engines: what is the convention are you using in your
code? And what do you write to NetCDF file?
- For post-processing tools: does it matter for you what convention is used?

Best regards,

Bert

[esatel]

Thanks, This makes sense.

[Rich Signell]

Folks,
Just be aware that not all the CF-compliant vertical coordinates are
currently coded into some of the libraries that take advantage of CF
-- in particular, I think the latest NetCDF-Java only implements the
ocean_sigma_coordinate and ocean_s_coordinate for ocean coordinates,
so the sigma-over-z may need to be added to the code if you are trying
to use NetCDF-Java dependent toolboxes like NCTOOLBOX. The good
news is that this is pretty easy, and Unidata can usually get stuff
added quickly to the next release....

-Rich

> --
> You received this message because you are subscribed to the Google Groups
> "UGRID Interoperability" group.
> To view this discussion on the web visit

> https://groups.google.com/d/msg/ugrid-interoperability/-/jzu2hkkPuIoJ.

>
> To post to this group, send email to
> ugrid-inter...@googlegroups.com.
> To unsubscribe from this group, send email to
> ugrid-interoperab...@googlegroups.com.
> For more options, visit this group at
> http://groups.google.com/group/ugrid-interoperability?hl=en.

--
Dr. Richard P. Signell (508) 457-2229
USGS, 384 Woods Hole Rd.
Woods Hole, MA 02543-1598

[Rich Signell]

From my experience, the layer convention for stretched vertical
coordinate models seems pretty evenly split:

FVCOM, HYCOM, POM: 1st layer is surface
ROMS, SELFE: 1st layer is bottom

-Rich

> --
> You received this message because you are subscribed to the Google Groups
> "UGRID Interoperability" group.