Jonathon,
Thanks. The picture is clearer now, but I think I still have a question or two. Let me try to summarize first, then ask the questions:
Ok, so for example, we have the simple case of the variable containing the physical variable of sea water temperature:
float t_an(time, depth, lat, lon) ;
t_an:standard_name = "sea_water_temperature" ;
t_an:long_name = "Objectively Analyzed Mean of Sea Water Temperature" ; // Expanded long_name following Steve's comment
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" ; // added space between dimension and method, following Jonathan's comment
t_an:grid_mapping = "crs" ;
t_an:units = "degrees_celsius" ;
t_an:FillValue = 9.96921e+36f ;
And, I would point out there there are cell bounds variables as well for lat, lon, depth, and a climatology_bounds for climatological time (time axis is a climatological time axis). So, we have a standard name, plus cell_methods.
The next case for these data is where we have a statistical value that is contained in the variable, but where no standard_name modifier exists? here is an example then for standard deviation of that sea water temperature:
float t_sd(time, depth, lat, lon) ;
t_an:standard_name = "sea_water_temperature" ; // Use the physical parameter's standard_name, following Jonathan's comment
t_an:long_name = "Temporal Standard Deviation about the Statistical Mean Sea Water Temperature" ; // Expanded long_name following Steve's comment
t_an:comment = "The temporal standard deviation about the statistical mean Sea Water Temperature in each grid-square at each standard depth level" ; // just highlighting changes compared to our existing draft
t_an:cell_methods = "area: mean depth: mean time: standard_deviation" ; // sequence is correct I think, take area-depth mean first, then compute standard deviation over time
t_an:grid_mapping = "crs" ;
t_an:units = "degrees_celsius" ;
t_an:FillValue = 9.96921e+36f ;
Seems simple enough, though I do need to confirm with Tim that the variable is in fact a temporal standard deviation. Now the third case is where there exists a relevant standard_name modifier, for example, for the standard error of the mean:
float t_se(time, depth, lat, lon) ;
t_an:standard_name = "sea_water_temperature standard_error" ; // Use the physical parameter's standard_name plus modifier, following Jonathan's comment
t_an:long_name = "Standard Error about the Statistical Mean Sea Water Temperature" ; // Expanded long_name following Steve's comment
t_an:comment = "The standard error about the statistical mean Sea Water Temperature in each grid-square at each standard depth level" ; // just highlighting changes compared to our existing draft
t_an:cell_methods = "area: mean depth: mean" ; // Is this correct?? Since we have a standard name modifier, and no cell_methods string for standard error?
t_an:grid_mapping = "crs" ;
t_an:units = "degrees_celsius" ;
t_an:FillValue = 9.96921e+36f
So, my question arises in this last example, where a standard name modifier exists. I guess this is the part I don't understand?. is there no reference to cell_methods for the time dimension in the standard error variable t_se? If so, why is there a standard_error standard_name modifier but not one for standard_deviation?
Thanks, Ken
On Mar 25, 2013, at 1:40 PM, Jonathan Gregory <j.m.gregory at reading.ac.uk> wrote:
> Dear Ken
>
>> Thanks for your response too (copied here? is it bad form in a listserv to consolidate responses like this?)
>
> I think it's convenient, myself!
>
>> That answer seems so easy and obvious that I wonder if I asked the question properly! I'll have to ask Tim to be sure, but I think the standard deviation is the standard deviation over time, of means generated in each time-area-depth cell.
>
>> But I think the question still remains about being able to use a standard name, which we would like to do of course? I am pretty sure in this example for this standard deviation variable we should NOT use sea_water_temperature for standard_name, and that it would be good if there were more standard name modifiers to choose from. If there were, perhaps we could set standard name to something like "sea_water_temperature standard_deviation".
>
> You *should* use sea_water_temperature as the standard_name. The standard_name
> alone is not to be regarded as the description of the metadata. It has to be
> taken in combination with cell_methods and modifiers. Maybe it seems more
> surprising that a temporal standard deviation of sea_water_temperature has
> sea_water_temperature for its standard name, but it's really the same kind of
> idea - i.e. a statistic - as a temporal mean or a temporal maximum, isn't it.
> Even if it was variance its standard_name would be sea_water_temperature, and
> in that case the units would be different too.
>
> Cheers
>
> Jonathan
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 Tue Mar 26 2013 - 06:32:14 GMT
