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

[Kenneth S. Casey - NOAA Federal]

Chris, On Mar 22, 2013, at 3:38 PM, Chris Barker - NOAA Federal <chris.bar...@noaa.gov> wrote: On Fri, Mar 22, 2013 at 11:05 AM, Jonathan Gregory <j.m.greg...@reading.ac.uk> wrote: 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? I think you need a definition of the cell boundaries also: http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.6/cf-conventions.html#cell-boundaries Thanks… I think we have those in the actual files already and I was only copying and pasting a subset of the info. We'll double check to make sure they are in there.  I know we include in our NODC netCDF templates the recommendation to include the bounds attribute pointing to the variables containing the bounds (see http://www.nodc.noaa.gov/data/formats/netcdf/, for grids here is the NODC CDL template: http://www.nodc.noaa.gov/data/formats/netcdf/grid.cdl) and we are following our own templates :-)  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 ; from this, I can tell that the value is a mean over area, depth and time -- but what area? what depths? what time? I'd probably assume the area of a single grid box (though that's not totaly defined here, and probaly the full water depth, but I'm not at all sure about time: mean over one time step?> monthly mean? yearly? As I mentioned we do (I think) already include the specific bounds, but note that each of these files contains data for a specific temporal period either monthly, seasonally, or annually.   this brings u sa question for me: how would one define a cell bounds that was "the full water depth". Good question… if you had a variable that was for example the mean temperature in 1 deg by 1 deg by full water depth cell, you would have a two-D gridded data variable (dims of lat and lon).  I think you would then have a bounds attribute that would point to your lat- and lon- bounds (easy enough) variables, and then a z-bounds variable that would specify the depth of the water column in each grid cell? Hmmm… but something seems off with that because depth is not a coordinate variable in the case of a two-dimensional grid.   Ken -Chris -- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/OR&R            (206) 526-6959   voice 7600 Sand Point Way NE   (206) 526-6329   fax Seattle, WA  98115       (206) 526-6317   main reception chris.bar...@noaa.gov _______________________________________________ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata 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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