Hi all,
Normally CF doesn't prohibit extra attributes being defined, so I'm not
sure whether the checker should be objecting. That being said, I don't
think the convention should sanction attaching a cell_methods to a
coordinate variable *instead* of attaching it to a regular variable
because then software attempting to determine what the cell_methods are
would have to look both places. Currently, software can always find
*all* the cell_methods in a single place-- attached to the variable.
best regards,
Karl
On 6/1/15 2:35 AM, David Hassell wrote:
> Hello Mahalo, Charlie,
>
> My gut feeling was "it shouldn't", but I then thought "why not?" after
> I couldn't think of any counter examples hwich would cause problems.
>
> Section 7.3 doesn't disallow it, I think, and I don't think there will
> be any conflict or ambiguity arising from its use. Appendix A would
> need to be updated and perhaps some text in 7.3 highlighting that it
> is OK, clarifying that the variable (the time coordinate in your
> example) "defines its own cells"?
>
> This is similar to the recent (ongoing) thread on allowing a
> coordinate variable to have an ancillary_variables attribute.
>
> Does that still make sense?
>
> All the best,
>
> David
>
>
> ---- Original message from Charlie Zender (05PM 31 May 15)
>
>> Date: Sun, 31 May 2015 17:17:35 -0700
>> From: Charlie Zender <zender at uci.edu>
>> To: CF Metadata Mail List <cf-metadata at cgd.ucar.edu>
>> Subject: [CF-metadata] Are cell_methods attributes OK for coordinate
>> variables?
>> User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101
>> Thunderbird/31.4.0
>>
>> Aloha CFers,
>>
>> Is it correct to add a cell_methods = "time: mean" attribute to the
>> time coordinate when the coordinate is averaged over time?
>> NCO's ncra does this (though the NERC CF checker doesn't like it).
>> It's clear from the CF docs that ncra time-averaging a variable like
>> wind(time) from an array to a degenerate (size 1) array should
>> add a cell_methods = "time: mean" attribute to wind.
>> Yet should it add cell_methods to the time coordinate itself?
>>
>> My take is that it should. The time_bounds variable, if any,
>> will show the original extent of the temporal range, and the time
>> coordinate value contains the mean of the original range.
>> Yet an NCO user is making a good case that cell_methods are only
>> for non-coordinate variables. His point is that many variables with
>> different cell_methods can all contain the same coordinate, so that
>> the coordinate should not have cell_methods. My response is that
>> cell_methods refers to the bounds variable of the coordinate, not
>> the coordinate values themselves.
>>
>> Is the question clear? If not, I can supply CDL...
>>
>> Mahalo,
>> Charlie
>>
>> p.s. the CF list archives on the CF homepage poinst to
>> http://mailman.cgd.ucar.edu/pipermail/cf-metadata
>> and that URL currently (and for the past ~week) yields this error:
>> The requested URL /pipermail/cf-metadata/ was not found on this server.
>> --
>> Charlie Zender, Earth System Sci. & Computer Sci.
>> University of California, Irvine 949-891-2429 )'(
>> _______________________________________________
>> CF-metadata mailing list
>> CF-metadata at cgd.ucar.edu
>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>
> --
> David Hassell
> National Centre for Atmospheric Science (NCAS)
> Department of Meteorology, University of Reading,
> Earley Gate, PO Box 243,
> Reading RG6 6BB, U.K.
>
> Tel : +44 118 3785613
> E-mail: d.c.hassell at reading.ac.uk
> _______________________________________________
> CF-metadata mailing list
> CF-metadata at cgd.ucar.edu
> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <
http://mailman.cgd.ucar.edu/pipermail/cf-metadata/attachments/20150601/9b54885e/attachment.html>
Received on Mon Jun 01 2015 - 07:59:06 BST
