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 <[email protected]> > To: [email protected] > 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 <[email protected]> > >>To: CF Metadata Mail List <[email protected]> > >>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 > >>[email protected] > >>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: [email protected] > >_______________________________________________ > >CF-metadata mailing list > >[email protected] > >http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > > _______________________________________________ > CF-metadata mailing list > [email protected] > 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: [email protected] _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
