[CF-metadata] Question from NODC about interplay of standard name modifiers, cell_methods, etc.

From: Kenneth S. Casey - NOAA Federal <kenneth.casey>
Date: Fri, 22 Mar 2013 13:29:11 -0400

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



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Received on Fri Mar 22 2013 - 11:29:11 GMT