Dear Martin It's legal to have more than one axis of a given standard_name but it is possibly inconvenient, because analysis software could not use the standard_ name of those two coordinate variables to distinguish them; instead, it would have to use the long_name or the variable name, which is not a CF-like method.
Another possibility would be to introduce new standard_names, which are more precise, such as area_type_of_land_use and area_type_of_vegetation in this case, while also keeping area_type as the union. That would require a rearrangement of the area_type table. On the whole, I think in this case it would be best to introduce a new combined area_type of pastures_of_c4_plant_functional_types i.e. flatten it. I guess this will also be more convenient for analysts than having to search the combination of two dimensions. You are right of course that doing this could turn the area_type table into an N^2 or even an N^n problem, which would be unmanageable, but if this is the *only* use-case, or even if we had a dozen such use-cases, it is not a problem. Thus, I would say we cross this bridge when we come to it, rather than anticipating a problem which hasn't arisen yet. Best wishes Jonathan On Fri, Jan 06, 2017 at 11:43:57AM +0000, [email protected] wrote: > Date: Fri, 6 Jan 2017 11:43:57 +0000 > From: [email protected] > To: [email protected], [email protected], [email protected] > CC: [email protected], [email protected] > Subject: Composite area types in CMIP6 data > > Hello, > > In CMIP6 we have a request for some data on pasture land with C4 functional > type. We already have CF area types for pasture and c4 plants in general. We > could construct the required information as follows: > > float pastureFracC4(time, lat, lon) ; > pastureFracC4:coordinates = "type ftpye" ; > pastureFracC4: standard_name = "area_fraction"; > ...... > char type(strlen) ; > type:long_name = "Pasture Land" ; > type:standard_name = "area_type" ; > char ftype(strlen) ; > ftype:long_name = "Plant Functional Type" ; > ftype:standard_name = "area_type" ; > data: > type = "patsures" ; > ftype = "c4_plant_functional_types"; > > This would provide the information that the variable pastureFracC4 refers to > areas that are both "pastures" and "c4_plant_functional_types". An altenative > would be to add a new area type, but I have the feeling that the area_type > list will become unmanagable if we keep adding new terms for combinations of > existing terms. Can anyone see a problem with using two area_type > coordinates? > > regards, > Martin _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
