Chris,
On Mar 22, 2013, at 3:38 PM, Chris Barker - NOAA Federal <chris.barker at noaa.gov> wrote:
> On Fri, Mar 22, 2013 at 11:05 AM, Jonathan Gregory
> <j.m.gregory at 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.Barker at noaa.gov
> _______________________________________________
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Kenneth S. Casey, Ph.D.
Technical Director
NOAA National Oceanographic Data Center
1315 East-West Highway
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301-713-3272 x133
http://www.nodc.noaa.gov
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Received on Fri Mar 22 2013 - 14:15:03 GMT
