Dear Jonathan, Thanks a lot for your clarification. I was not aware about the CF checker. Such validator is a great idea! Best regards Alex
On 09/11/13 21:47, Jonathan Gregory wrote: > 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 -- Alexander Barth GeoHydrodynamics and Environment Research, MARE, AGO University of Liège, Sart-Tilman B5, 4000 Liège, Belgium Phone: +32-4-3663664 Fax: +32-4-3669729 Email: [email protected] _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
