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 <taylor13 at llnl.gov> 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?
>
>
>
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>
>
--
Dr. M. Benno Blumenthal benno at iri.columbia.edu
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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