Sorry, I was not clear, I think. I was proposing time(reftime,leadtime) time:standard_name="time"; time:units = "days since 1970-01-01 00:00:00";
a 2D variable which gives the actual time corresponding to each reftime, leadtime pair -- it can be computed as the unit-corrected sum of reftime and leadtime, but that is irrelevant, it is explicitly in the file. On Tue, May 17, 2011 at 4:29 PM, Karl Taylor <[email protected]> wrote: > I wonder what the units for "time" (=reftime+leadtime) would be, since > reftime is different for each trajectory? > Karl > > On 5/17/11 1:24 PM, Benno Blumenthal wrote: > > Aside from avoiding the use of the word "time" for anything that is not > "days since" or equivalent, I would do it as you described. Instead of > time I would use "leadtime" or "L", particularly so that I could define > "time" (reftime + leadtime) (with standard_name "time") and include that as > well in the variable list. > > On Tue, May 17, 2011 at 3:02 PM, Karl Taylor <[email protected]> wrote: > >> Hi Benno, >> >> This isn't really a comment on your email, but a question (only somewhat >> related) occurred to me. When you store multiple trajectories (or >> forecasts), each started from a difference reference, but sampled in the >> same way (at equal intervals), how should this be done? Suppose, for >> example, you want to store ozone data from 10 freely moving balloons, with >> samples taken hourly following release (for 24 hours), but each balloon >> released at a different time. Would you do this as follows? >> >> dimensions: >> time = 24 ; >> ref_time=10 >> variables: >> float O3(time,ref_time) ; >> O3:long_name = "mole_fraction_of_ozone_in_air" ; >> O3:units = "1e-9" ; >> O3:coordinates = "lon lat z" ; >> double time(time) >> time:standard_name = "elapsed_time??? or relative_time???" >> time:long_name = "elapsed time since the beginning of the trajectory" >> time:units = "hr" >> double ref_time(ref_time) ; >> ref_time:standard_name = "reference_time???" ; >> ref_time:long_name = "time when balloon was released and the reference >> for elapsed_time (relative_time)" >> ref_time:units = "days since 1970-01-01 00:00:00" ; >> float lon(time,ref_time) ; >> lon:standard_name = "longitude" ; >> lon:units = "degrees_east" ; >> float lat(time,ref_time) ; >> lat:standard_name = "latitude" ; >> lat:units = "degrees_north" ; >> float z(time,ref_time) ; >> z:standard_name = "height_above_reference_ellipsoid" ; >> z:units = "km" ; >> z:positive = "up" ; >> >> Note the possible standard_names (I think, suggested by others). >> >> Best regards, >> Karl >> >> >> >> >> On 5/17/11 8:46 AM, Benno Blumenthal wrote: >> >> CF has standard names forecast_reference_time, forecast_period and >> time which are interrelated in a particular way. >> >> I have a trajectory dataset which also has reference_time, period, >> and time which are interrelated in the same way, but forecast is not >> an appropriate descriptor: the reference_time is the start of the >> trajectory, the period is the time relative to the start_time along >> the trajectory. >> >> I am wondering how important "forecast" is in the semantics of these >> particular standard_names -- does it really have to be a forecast? >> After all, these are the standard names for the time coordinates, e.g. >> independent variables, while forecast is a property of the dependent >> variables, i.e. how they were computed. >> >> Do we need more general names? Am I taking the current names too literally? >> >> >> >> _______________________________________________ >> CF-metadata mailing list >> [email protected] >> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >> >> > > > -- > Dr. M. Benno Blumenthal [email protected] > International Research Institute for climate and society > The Earth Institute at Columbia University > Lamont Campus, Palisades NY 10964-8000 (845) 680-4450 > > > _______________________________________________ > CF-metadata mailing list > [email protected] > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > > -- Dr. M. Benno Blumenthal [email protected] International Research Institute for climate and society The Earth Institute at Columbia University Lamont Campus, Palisades NY 10964-8000 (845) 680-4450
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