Dear Ken This email is about your specific question relating to the use of the CF standard as it currently is. By the way, I applaud your efforts to provide CF-compliant datasets from NODC and to help others in the ocean data world to make CF-compliant datasets.
I am about to make another posting about the more general question. I don't think the CF standard gives any instruction about what the cell_methods should be when the standard_name contains a modifier. I would say that, because the standard_error values belong with the data values, the ancillary variable that contains the standard_error should have all the same metadata as the data variable, except for the addition of the standard_name modifier. So I would put t_an:standard_name = "sea_water_temperature standard_error" ; t_an:cell_methods = "area: mean depth: mean time: mean" ; for the ancillary variable of standard error, if the data variable has "area: mean depth: mean time: mean". This means the SE variable is completely self-describing. If the ancillary variable were seen as entirely dependent on the data variable, you could argue that it didn't need any metadata such as standard_name and cell_methods, because it would implicitly inherit all the metadata of its data variable. For this kind of reason, bounds variables actually do not need units or standard names; they are regarded as dependent on the coordinate variables they belong to. However in the case of ancillary variables, CF doesn't make such a strong link. The ancillary_variables attribute is a kind of convenience or courtesy feature, which allows the user to locate the ancillary variables more easily, but those variables are themselves independent variables, rather than subservient. One reason for that design is that the ancillary variables might be in different netCDF files from the variables to which they are ancillary e.g. you might have a file for the temperatures, another file for their standard errors, and another for the number of observations. If this is the case, they need to be able to describe themselves properly. By the way, in my version of udunits, degrees_celsius is not legal. It will accept only degree_Celsius out of the four variants singular/plural c/C. Maybe this is a difference between udunits 1 (which I have) and udunits 2. Best wishes Jonathan _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
