Dear Karl
I agree with Seth that this isn't anticipated by the design of the convention,
which assumes that the mean over seasons is composed of a number of complete
seasons. Is this a real use-case, with a DJF mean made by including JF from one
NH winter and D from another? It seems a bit odd to me. I wouldn't compute a
monthly mean of anything if 2/3 of the days were missing in the month. But,
following this logic, your original choice of "1999-12-1" to "2011-3-1" is OK,
and it "just happens" that Dec 1999 and Jan-Feb 2011 are actually not included,
as if they were missing data. Their omission is not recorded by the climatology
bounds but, equally, if Dec 2005 or Jan-Feb 2008 (for example) were missing
when computing the mean you would not know about it from the climatology
bounds. So perhaps it doesn't matter.
To spell out exactly which months were used, it would be necessary to record
also the time coordinate and bounds before the collapse. In various tickets we
have discussed but not agreed a convention for doing that, as extra info.
Alternatively you could record it as unstandardised info as a comment in () in
the cell_methods, as you note.
Best wishes
Jonathan
----- Forwarded message from Karl Taylor <taylor13 at llnl.gov> -----
> Date: Wed, 10 Feb 2016 15:37:01 -0800
> From: Karl Taylor <taylor13 at llnl.gov>
> To: cf-metadata at cgd.ucar.edu
> Subject: [CF-metadata] How to build CF-compliant seasonal climatology when
> data begins within a season
> User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:38.0)
> Gecko/20100101 Thunderbird/38.5.1
>
> Dear CF community,
>
> In representing the seasonal climatology based on data available for
> the period January 1, 2000 through December 31 2010, what would be
> the correct climatology_bounds?
>
> climatology_bounds = "1999-12-1", "2011-3-1",
> "2000-3-1", "2010-6-1",
> "2000-6-1", "2010-9-1",
> "2000-9-1", "2010-12-1" ????
>
> I would note that this seems to capture the idea that we are
> reporting seasonal means, but it also seems to indicate that this is
> based in part on data from Dec. 1999 and Jan.-Feb. 2011, when it
> isn't. Is this the best I can do? [Of course the convention can
> never tell us if data are complete in forming a climatology. If 1
> year were missing, this would not affect the attributes.]
>
> I suppose the in the cell_methods attribute ("time: mean over days
> time: mean over years" I could add non-standardized information (as
> permitted by CF), for example: "time: mean over days time: mean
> over years (with data from the period 2000-1-1 to 2011-1-1)"
>
> thanks for any suggestions,
> Karl
>
>
>
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----- End forwarded message -----
Received on Thu Feb 11 2016 - 13:20:40 GMT
