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 <taylor13 at llnl.gov
> <mailto: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
> <mailto: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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Received on Tue May 17 2011 - 14:29:50 BST
