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> 3. z coordinate required, with values in any vertical coordinate system. > 4. z coordinate required, may be a "nominal" value (just a string description) > 5. No z coordinate required.> > I would lean towards 4, but could be convinced of 5 or 3. We > should however recommend the data provider add as much info as > possible, and make sure there is a standard way to do so.I think it should be 5, but if there is a Z value, it should be 3. In the atmosphere, raobs measure pressure and it is converted to height so the "real" z coordinate is not convertible to meters. And as I mentioned earlier, if you require 1 or 2, you cannot store satellite derived winds in that format because you have no height value. ... if there is no Z value, what do I do if you go with 4? Just have a string called "unknown"?
I agree with these arguments of Don's. Also, in a case where the data is on a "special" level which can only be named, rather than given a numerical z-coord, that should be indicated by the standard name (though I note John Graybeal's reservation about this, which is that the same instrument might be producing data of different stdnames when used for different purposes). I agree with you, of course, that if the z-coord exists meaningfully it should be provided, to make the data more useful. However, our usual kind of policy in CF would be to make this a recommendation, rather than a requirement. There is lots of optional metadata that good practice would include when relevant. Too many *requirements* are a deterrent to adoption of the standard. Best wishes Jonathan