[CF-metadata] Cell bounds associated with coordinate variable rather than data variable

From: Jonathan Gregory <j.m.gregory>
Date: Thu, 22 Oct 2009 08:40:17 +0100

Dear Ethan

You are right, boundary variables are associated with coordinate variables.
That is because you need to supply point coordinates as well as cell bounds.
I think it is usually natural to regard both the extent of a cell and the
coordinate of the point as aspects of the definition of the cell. Of course for
extensive quantities, like accumulated precipitation, the cell bounds are
more important, and the coordinate value is more arbitrary. I would argue that
it is helpful to have different time coordinate variables for each of your
data variables. They happen to have the same-size dimension in your example,
but the bounds and coordinates don't correspond, and it could be confusing to
share the time axes, when really they are not the same. If the time-coordinate
is taken to be the middle of the interval, as people often do, the 3-h bounds
have coordinates 1.5, 4.5, 7.5, ..., while the 6-h bounds have coordinates
3, 6, 9, ... These should not share a coordinate variable.

Best wishes

Jonathan
Received on Thu Oct 22 2009 - 01:40:17 BST