Dear Alex
> I have a question on the time variable of a monthly climatologies collecting e.g. all data from
> 1900-01-01 to 2000-12-31.
> As I understand the standard
> (http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.6/cf-conventions.html#climatological-statistics),
> I should use the following:
>
> dimensions:
> time=12;
> nv=2;
> variables:
> float temperature(time,lat,lon);
> temperature:cell_methods="*time: mean within years time: mean over years*";
> double time(time);
> time:climatology="climatology_bounds";
> time:units="days since 1900-1-1";
> double climatology_bounds(time,nv);
> data: // time coordinates translated to date/time format
> time="1900-1-16", "1900-2-16", "1900-3-16", "1900-4-16", ... "1900-12-16";
> climatology_bounds="1900-1-1", "2000-2-1",
> "1900-2-1", "2000-3-1",
> ....
> "1900-11-1", "2001-12-1";
>
>
> I use the standard Gregorian calendar. Can you confirm that the used cell_methods and
> climatology_bounds are correct?
They look correct to me. Although the standard calendar is the default, it
would do no harm, and might be informative, to include a calendar attribute.
You can check that your metadata is correct by using the CF checker on the
CF website.
> I am not so sure about the cell method since the WOA 2009 climatology uses "time:mean within
> *months* time:mean over *months*" for monthly climatologies
> (http://data.nodc.noaa.gov/thredds/dodsC/woa/WOA09/NetCDFdata/temperature_monthly_1deg.nc.info).
That is incorrect. I think the CF checker would report that error. It would be
good if NODC could correct the error - I wonder if we have any NODC subscribers
on this list.
> I am wondering if it would not have been easier to define climatology_bounds as an array with the
> starting and end dates of *all *subintervals (not just the start for the first and the end of the
> last subinterval). It would be simpler to find out to which time slice of the climatological
> variable an individual observation would relate to. It would also allow to make climatologies over
> other cycles (e.g. tides) or non-periodic processes (e.g. ENSO).
To calculate climatologies over arbitrary periods, you would need the original
monthly data, wouldn't you, not the monthly climatology. A non-climatological
dataset has time bounds for each individual time interval, as you describe.
Best wishes
Jonathan
Received on Sat Nov 09 2013 - 13:47:37 GMT
