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" <kenneth.casey at noaa.gov> -----
> From: "Kenneth S. Casey - NOAA Federal" <kenneth.casey at noaa.gov>
> Date: Fri, 22 Mar 2013 13:29:11 -0400
> To: cf-metadata at cgd.ucar.edu
> X-Mailer: Apple Mail (2.1499)
> CC: Tim Boyer <tim.boyer at noaa.gov>, Ajay Krishnan <ajay.krish at gmail.com>
> 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
>
>
>
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----- End forwarded message -----
Received on Fri Mar 22 2013 - 12:05:33 GMT
