I would not recommend UGRID for non-standard but structured (e.g logically
rectangular) grids. I'm not aware of anyone planning to turn in data on a
completely unstructured grid in CMIP6.
Thanks, and best wishes to everyone for 2018,
Karl Taylor writes:
In CMIP we require that both missing_value and _FillValue be defined as
1.e20 for requested variables that occupy only a portion of the global grid.
For bounds variables, I'll suggest that when needed, both _FillValue and
missing_value also be defined as 1.e20. That way software that relies on
either one will work.
My understanding of UGRID is that it provides for a much fuller description
of a grid than CF. For CMIP, I think we can recommend UGRID be used for
non-standard grids, but I'm reluctant to require it. Most grids for most
purposes I think can be adequately described with the CF-mandated
attributes. Does anyone disagree?
thanks,
Karl
On 1/1/18 4:47 PM, Chris Barker wrote:
On Wed, Dec 20, 2017 at 2:21 PM, Karl Taylor <taylo...@llnl.gov
<mailto:taylo...@llnl.gov>> wrote:
My sense is that no one violently opposes the use of missing_value
to fill unused vertices for grid cells with fewer than the maximum
number of vertices.
I'm pretty sure this has been brought this up before (at least suggesting
that UGRID be consulted )but UGRID uses _FillValue , rather than
missing_value:
http://ugrid-conventions.github.io/ugrid-conventions/#2d-flexible-mesh-mixed-triangles-quadrilaterals-etc-topology
I have no recollection as to why that was chosen, but I encourage you not
to do something different than an existing standard without good reason.
For CMIP6 some models may need to define grids with a few cells
having one less vertex than the majority. I am (much too late in
the process) writing down the data requirements for CMIP6 model
output,
Any reason CMIP shouldn't specify the UGRID standard and be done with it?
If there is something missing from the UGRID standard that is needed,
please let us know, and ideally propose an addition.
-CHB
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