Thanks Jonathan,
I didn't think of that dependency. So, if
varN:coordinates = "lat lon";
varN:cell_methods = "lat: point lon: point";
for *all* variables 'varN' that relate to 'lat' and 'lon' as
coordinates, then the 'bounds' attributes on 'lat' and 'lon' are
superfluous and can be skipped. If any one of the variables refers to
'lat'/'lon' by means of a cell method other than 'point', e.g. 'mean',
then it must be specified what range/cell the cell_method relates to
i.e. 'bounds' should be required. That seems more like a consistency
*requirement* than merely a recommendation. If 'cell_methods' is not
specified on one or more variables, then the need for 'bounds' becomes
more fuzzy. The discussion on the default interpretation for
'cell_methods' in Section 7.3 suggests that one might distinguish
between extensive quantities like 'cloud_area_fraction' and intensive
quantities like 'sea_surface_height'. The former might require it,
whereas it would be optional in the latter case. However, in order to
avoid too complex logic, I would agree with a general recommendation to
include 'bounds' when 'cell_methods' is missing on one or more variables.
Best regards,
Bert
--------
Jonathan Gregory wrote:
Dear Bert
I agree that it is important to distinguish whether values are points or
averages. This distinction is made in CF by cell_methods, which indicates
the interpretation for each axis. We already recommend that cell_methods be
included for all spatiotemporal axes, so I suppose the checker should warn
if this is not so. Furthermore, we already have a recommendation that bounds
should be included unless cell_methods says the data applies to grid-points;
that answers Karl's comment, I think. (I'd forgotten this recommendation.)
Best wishes
Jonathan
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