Dear John
The same section 7.4 of the CF standard describes the CF convention for this,
which uses the bounds of the time coordinates to encode the range of years
to which the data applies e.g. Examples 7.8 and 7.9. Is this what you mean?
Cheers
Jonathan
----- Forwarded message from John Wilkin <wilkin at marine.rutgers.edu> -----
> Date: Fri, 4 Jan 2013 16:12:18 -0500
> From: John Wilkin <wilkin at marine.rutgers.edu>
> To: cf-metadata at cgd.ucar.edu
> Subject: [CF-metadata] convention for climatological time units
>
> Is there an accepted convention for describing the units of a
> climatological time axis? e.g. monthly averages January, February
> etc.
>
> The CF Conventions (Section 7.4)
> http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.4/cf-conventions.html#climatological-statistics
> note the COARDS recommendation of using year ZERO:
>
> "For compatibility with COARDS, time coordinates should also be
> recognised as climatological if they have a units attribute of
> time-units relative to midnight on 1 January in year 0 i.e. since
> 0-1-1 in udunits syntax"
>
> But the document goes on to discourage this:
>
> "We do not recommend this convention because (a) it does not provide
> any information about the intervals used to compute the climatology,
> and (b) there is no standard for how dates since year 1 will be
> encoded"
>
> Looking at how others have handled this there is a tendency to choose
> an arbitrary base date, e.g. the World Ocean Atlas at NODC
> http://data.nodc.noaa.gov/thredds/dodsC/woa09/temperature_monthly_1deg.nc.html
> uses "days since 2008-1-1" when there is no actual relevance to year
> 2008 at all. All the climatologies at ERDDAP use "seconds since
> 1970-01-01".
>
> Thanks,
> John.
>
> --
> John L Wilkin | jwilkin at rutgers.edu | ph: +1-609-630-0559
> web: marine.rutgers.edu/~wilkin | cal: tinyurl.com/jwilkincalendar
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----- End forwarded message -----
Received on Sat Jan 05 2013 - 06:48:34 GMT
