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 <taylor13 at llnl.gov> 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 <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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>
>
--
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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