Hello,
> I don't think the convention should sanction attaching a
> cell_methods to a coordinate variable *instead* of attaching it to a
> regular variable.
I agree. The cell methods on a coordinate (e.g. time) would describe
the coordinate values, not the data variable values (e.g.
air_temperature) which are geolocated by the coordinate.
David
---- Original message from Karl Taylor (06AM 01 Jun 15)
> Date: Mon, 1 Jun 2015 06:59:06 -0700
> From: Karl Taylor <taylor13 at llnl.gov>
> To: cf-metadata at cgd.ucar.edu
> Subject: Re: [CF-metadata] Are cell_methods attributes OK for coordinate
> variables?
> User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:31.0)
> Gecko/20100101 Thunderbird/31.7.0
>
> 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
>
> _______________________________________________
> 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
Received on Tue Jun 02 2015 - 01:50:44 BST
