Dear Ken The cell_methods would indicate standard deviation. This allows you to say whether you mean standard deviation over time, latitude, longitude or whatever dimension, so it's more precise - which one do you mean, in fact?
By the way, in cell_methods there should be a space after ":" e.g. "area: mean". Best wishes Jonathan ----- Forwarded message from "Kenneth S. Casey - NOAA Federal" <[email protected]> ----- > From: "Kenneth S. Casey - NOAA Federal" <[email protected]> > Date: Fri, 22 Mar 2013 13:29:11 -0400 > To: [email protected] > X-Mailer: Apple Mail (2.1499) > CC: Tim Boyer <[email protected]>, Ajay Krishnan <[email protected]> > Subject: [CF-metadata] Question from NODC about interplay of standard name > modifiers, cell_methods, etc. > > Hi Everyone, > > At US NODC we are trying to sort out how to best document a gridded dataset > that contains a number of variables. For example, we have a sea water > temperature gridded dataset, and it contains 6 variables: > > objectively analyzed mean > statistical mean > number of observations > standard deviation > standard error of the mean > 'grid points' > > We are currently documenting, for example, the objective analyzed mean > temperature variable in this netCDF file like this: > > float t_an(time, depth, lat, lon) ; > t_an:standard_name = "sea_water_temperature" ; > t_an:long_name = "Objectively Analyzed Mean" ; > t_an:comment = "Objectively analyzed climatologies are the > objectively interpolated mean fields for an oceanographic variable at > standard depth levels for the World Ocean." ; > t_an:cell_methods = "area:mean depth:mean time:mean" ; > t_an:grid_mapping = "crs" ; > t_an:units = "degrees_celsius" ; > t_an:FillValue = 9.96921e+36f ; > > That makes reasonable sense to an application client because the variable > contains a temperature value, so the standard_name makes sense. Also, cell > methods here represent how the data in the cells are compiled. They do not > directly describe the "thing" in those cells but what kinds of procedures > where used (in this case, the grid cell, with time, lat, lon, and depth > dimensions, is a computed by calculating mean). We think this is the > correct way to represent this particular variable. > > But what we should do for the statistical variables is less clear. We can > use standard name modifiers to provide reasonable standard names, but only > four are defined currently: > > http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.6/apc.html > > detection_minimum, number_of_observations, standard_error, and status_flag > > How would we handle the variables like standard deviation? Right now, we > could not provide a standard name with a modifier, so we'd have to rely on > long_name and comment attributes which is not very satisfactory. We > wouldn't want to use > > t_standard_deviation:standard_name = "sea_water_temperature" ; > > because the values in the variable are not sea water temperature, they are > the standard deviation of sea water temperature. Is the solution to propose > some new standard name modifiers, or are we missing something? This issue > seems like it should be a fairly common problem. > > Thanks, > Ken > > > > Kenneth S. Casey, Ph.D. > Technical Director > NOAA National Oceanographic Data Center > 1315 East-West Highway > Silver Spring MD 20910 > 301-713-3272 x133 > http://www.nodc.noaa.gov > > > > _______________________________________________ > CF-metadata mailing list > [email protected] > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata ----- End forwarded message ----- _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
