[CF-metadata] WRF staggered grids and vertical coordinates

[Jonathan Gregory]

Dear John

It's not clear to me why we need this level of abstraction. If the basic grids
can be described already by CF, is it really essential to have extra
conventions to describe the relationships of grids, since this can be deduced
at run-time? Conventions of this kind would introduce redundancy and hence the
possibility of inconsistency. Maybe it is worth that price, but I'd be happier
if we had a clear statement of why - is that possible?

Thanks. Best wishes

Jonathan