Hi Benno, Jonathan, Chris,
Would you mind if I forward your email exchange to the MetOceans Domain
Working Group of the OGC? They are grappling with similar time issues, but
I don't think they have considered the relationship to trajectories that
Benno has raised.
-- Ben
On Tue, May 17, 2011 at 12:33 PM, Benno Blumenthal
<benno at iri.columbia.edu>wrote:
> I think what Jonathan said
>
>
> Therefore I think it would be sensible to add some more general names which
>> you could use, such as reference_time and elapsed_time. You might say that
>> a "time" is expressed by udunits as an elapsed_time since a
>> reference_time.
>>
>
>
> is pretty much on the mark: I was using the word "period" because the
> standard_name's grammar suggests using period for a time interval and saving
> "time" for temporal with reference time, though "elapsed_period" sounds a
> bit strange to my ears.
>
> As for my using "forecast_reference_time", I am willing to accept the
> judgement that it is not what I want, but I can't say that it is all that
> clear. Forecasts are integrations from initial conditions a.k.a the
> analysis, which is precisely what happens in a trajectory -- the terms used
> in defining forecast_reference_time are mostly ill-defined, particularly
> what is the "time of the analysis" -- in practice it is the sampling time of
> the most recent data in the forecast, plus the processing time it takes to
> get the data to the forecast, which means essentially that the forecaster
> gets to define it -- it does not have an absolute (standardized) meaning.
>
> Benno
>
>
> On Tue, May 17, 2011 at 12:31 PM, Christopher Barker <
> Chris.Barker at noaa.gov> wrote:
> > On 5/17/11 9:17 AM, Jonathan Gregory wrote:
> >>
> >> Dear Benno
> >>
> >>> CF has standard names forecast_reference_time, forecast_period and
> >>> time which are interrelated in a particular way.
> >>>
> >
> > note, from the standard name table:
> >
> > """
> > The forecast reference time in NWP is the "data time", the time of the
> > analysis from which the forecast was made. It is not the time for which
> the
> > forecast is valid; the standard name of time should be used for that
> time.
> > """
> >
> > So this really is a concept specific to forecasts, and not at all what
> you
> > want. Similarly for forecast_period.
> >
> >>> 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:
> >
> > I think you have the really standard time here, usually simply the "time"
> > array (expressed in time-since-a-reference-datetime). What does "period"
> > mean in your case?
> >
> > -Chris
> >
> >
> > --
> > Christopher Barker, Ph.D.
> > Oceanographer
> >
> > Emergency Response Division
> > NOAA/NOS/OR&R (206) 526-6959 voice
> > 7600 Sand Point Way NE (206) 526-6329 fax
> > Seattle, WA 98115 (206) 526-6317 main reception
> >
> > Chris.Barker at noaa.gov
> > _______________________________________________
> > CF-metadata mailing list
> > CF-metadata at cgd.ucar.edu
> > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
> >
>
>
>
> --
> 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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>
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Received on Tue May 17 2011 - 13:06:36 BST
