Dear Mike, what you describe sounds to me like a textbook example of what the netcdf4 groups could accomplish without any quirks. Since you do have a separate time axis for each variable, it doesn't make much sense in my view to force them to co-exist in one file at one "level". As far as I understand CF, this would require to define a "master time axis", which would serve as the time "coordinate". Or else, all time axes would be auxiliary coordinate variables, which also doesn't make much sense in a discovery framework. We did have a discussion on "group-aware CF" a while ago - maybe this is the time to resurrect this?
Best regards, Martin ================== PD Dr. Martin G. Schultz IEK-8, Forschungszentrum Jülich D-52425 Jülich Ph: +49 2461 61 2831 > Date: Tue, 18 Mar 2014 12:10:44 -0700 (PDT) > From: Mike Godin <mikego...@yahoo.com> > To: "CF-metadata@cgd.ucar.edu" <CF-metadata@cgd.ucar.edu> > Subject: [CF-metadata] Classification of a "trajectory" with > asynchronous time coordinates > Message-ID: > <1395169844.32180.yahoomail...@web141004.mail.bf1.yahoo.com > > > Content-Type: text/plain; charset="utf-8" > > I am considering a file from a sampling system that follows a trajectory, but > which collects each variable independently of each other. It would have with > a header that looks like the following (adapted from "Example H.13. A single > trajectory recording atmospheric composition."): > > ? ?dimensions: > ? ? ? time_lon = 42; > ? ? ? time_lat = 55; > ? ? ? time_z = 435; > ? ? ? time_O3 = 335; > ? ? ? time_NO3 = 5357; > > ? ?variables: > ? ? ? double time_lon(time_lon) ;? > ? ? ? ? ? time_lon:standard_name = "time"; > ? ? ? ? ? time_lon:long_name = "time_lon" ; > ? ? ? ? ? time_lon:units = "days since 1970-01-01 00:00:00" ; > ? ? ? float lon(time_lon) ;? > ? ? ? ? ? lon:standard_name = "longitude"; > ? ? ? ? ? lon:long_name = "longitude" ; > ? ? ? ? ? lon:units = "degrees_east" ; > ? ? ? double time_lat(time_lat) ;? > ? ? ? ? ? time_lat:standard_name = "time"; > ? ? ? ? ? time_lat:long_name = "time_lat" ; > ? ? ? ? ? time_lat:units = "days since 1970-01-01 00:00:00" ; > ? ? ? float lat(time_lat) ;? > ? ? ? ? ? lat:standard_name = "latitude"; > ? ? ? ? ? lat:long_name = "latitude" ; > ? ? ? ? ? lat:units = "degrees_north" ; > ? ? ? double time_z(time_z) ;? > ? ? ? ? ? time_z:standard_name = "time"; > ? ? ? ? ? time_z:long_name = "time_z" ; > ? ? ? ? ? time_z:units = "days since 1970-01-01 00:00:00" ; > ? ? ? float z(time_z) ;? > ? ? ? ? ? z:standard_name = ?altitude?; > ? ? ? ? ? z:long_name = "height above mean sea level" ; > ? ? ? ? ? z:units = "km" ; > ? ? ? ? ? z:positive = "up" ;? > ? ? ? ? ? ?z:axis = "Z" ;? > ? ? ? ? ? ? > ? ? ?double time_O3(time_O3) ;? > ? ? ? ? ? time_O3:standard_name = "time"; > ? ? ? ? ? time_O3:long_name = "time_O3" ; > ? ? ? ? ? time_O3:units = "days since 1970-01-01 00:00:00" ; > ? ? ? float O3(time_O3) ;? > ? ? ? ? ? O3:standard_name = ?mass_fraction_of_ozone_in_air?; > ? ? ? ? ? O3:long_name = "ozone concentration" ; > ? ? ? ? ? O3:units = "1e-9" ; > ? ? ? ? ? O3:coordinates = "time_O3 lon lat z" ; > > ? ? ?double time_NO3(time_NO3) ;? > ? ? ? ? ? time_NO3:standard_name = "time"; > ? ? ? ? ? time_NO3:long_name = "time_NO3" ; > ? ? ? ? ? time_NO3:units = "days since 1970-01-01 00:00:00" ; > ? ? ? float O3(time_NO3) ;? > ? ? ? ? ? NO3:standard_name = ?mass_fraction_of_nitrate_radical_in_air?; > ? ? ? ? ? NO3:long_name = "NO3 concentration" ; > ? ? ? ? ? NO3:units = "1e-9" ; > ? ? ? ? ? NO3:coordinates = "time_NO3 lon lat z" ; > > ? ?attributes: > ? ? ? :featureType = "????"; > > The data points could be sampled to generate a header exactly like the > example from the standard, but in doing so, one would lose information > about the timing of each variable's values, and would either end up with data > loss, or a much larger file. ?So I'm wondering: is this a valid "H.4.2. Single > trajectory"? ?If not, is it something that can be annotated as a valid CF > metadata file without altering the measured data? > > Thanks, Mike Godin > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: <http://mailman.cgd.ucar.edu/pipermail/cf- > metadata/attachments/20140318/6625043f/attachment.html> > > ------------------------------ > > Subject: Digest Footer > > _______________________________________________ > CF-metadata mailing list > CF-metadata@cgd.ucar.edu > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > > > ------------------------------ > > End of CF-metadata Digest, Vol 131, Issue 1 > ******************************************* ------------------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------------------ Forschungszentrum Juelich GmbH 52425 Juelich Sitz der Gesellschaft: Juelich Eingetragen im Handelsregister des Amtsgerichts Dueren Nr. HR B 3498 Vorsitzender des Aufsichtsrats: MinDir Dr. Karl Eugen Huthmacher Geschaeftsfuehrung: Prof. Dr. Achim Bachem (Vorsitzender), Karsten Beneke (stellv. Vorsitzender), Prof. Dr.-Ing. Harald Bolt, Prof. Dr. Sebastian M. Schmidt ------------------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------------------ _______________________________________________ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata