[CF-metadata] identification of vector components

From: Jonathan Gregory <j.m.gregory>
Date: Tue, 24 Apr 2012 16:01:45 +0100

Dear Mark

I see your point of view, and when we discussed this on the phone it did not
sound like a large issue to me. I agree with you that X/Y and lon/lat are
related ideas in CF. However, it appears there are some concerns.

As you say, as a data-producer, where the vector component is aligned to the
data grid you have to use a different standard name according to whether the
grid is lon-lat or not. However, there are other reasons why you have to be
aware of this too. Specifically, to write a CF-compliant file, if the grid
is not lon-lat you have to provide 2D lon and lat aux coord vars. If the grid
is lon-lat you won't provide these. The program writing the data must be aware
of the distinction, and can use it to decide which standard names to use.

If the file is correctly written then, as a data-consumer, you can decide
whether eastward/northward would be identical with x/y simply by inspecting the
standard_names of the coordinate variables.

Can similar tests be used with Grib conversion? I assume that Grib must provide
sufficient metadata to indicate whether the grid is lon-lat.

Best wishes

Jonathan
Received on Tue Apr 24 2012 - 09:01:45 BST