[CF-metadata] cell measures for non-horizontal planes

David Hassell d.c.hassell at reading.ac.uk
Wed Oct 7 09:37:48 MDT 2015


I was wondering if anyone can help clear something up for me: Can an
"area" cell measure variable span non-horizontal axes? For example,
could you have an area cell measure for X-Z cells? And if so, what
could its standard name be? E.g.

  float cell_area(longitude, height):
      cell_area:measure = "area";
      cell_area:units = "m2";
      cell_area:standard_name = ?????????????

I know that the standard_name attribute is optional, thus the two part

There is a standard name "cell_area" (= the horizontal area of a
gridcell), but not one for areas of arbitrarily orientated planes.

The conventions (section 7.2) do not explicitly disallow
non-horizontal planes (that's three negatives in half a sentence!),
but if they're allowed then the assumption is, I think, that the plane
of the area is implied by the variable's dimensions and there is no
applicable standard name. This is tricky if the cell measure variable
does have X and Y dimensions, as in example 7.3. This example uses the
standard name "area" for its cell measure variable, but this name is
not in the table - I presume that "cell_area" is meant. I'll raise a
defect ticket for this if required.

Many thanks and all the best,


David Hassell
National Centre for Atmospheric Science (NCAS)
Department of Meteorology, University of Reading,
Earley Gate, PO Box 243,
Reading RG6 6BB, U.K.

Tel   : +44 118 3785613
E-mail: d.c.hassell at reading.ac.uk

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