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 J?lich
D-52425 J?lich
Ph: +49 2461 61 2831
> Date: Tue, 18 Mar 2014 12:10:44 -0700 (PDT)
> From: Mike Godin <mikegodin at yahoo.com>
> To: "CF-metadata at cgd.ucar.edu" <CF-metadata at cgd.ucar.edu>
> Subject: [CF-metadata] Classification of a "trajectory" with
> asynchronous time coordinates
> Message-ID:
> <1395169844.32180.YahooMailNeo at 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 at 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
------------------------------------------------------------------------------------------------
------------------------------------------------------------------------------------------------
Received on Wed Mar 19 2014 - 01:53:35 GMT
