Dear Jonathan,
Night is indeed commonly used. Marine Air Temperature measurements taken
during the day are usually heavily contaminated by solar radiation and
the heat-island effect and so are discarded to produce Nighttime Marine
Air Temperature.
However the definition of nighttime is "specialised" for these purposes.
It is defined as Sunset+1 Hrs to Sunrise+1 Hrs (i.e on local time to the
ob). To further complicate the issue the data I am storing are time
averaged global gridded fields with the definition of sunrise and sunset
being used to filter what observations go into the average. Suggestions
on how to capture this would be happily received.
"difference_from_climatology" sounds absolutely fine. However, how and
where should the climatology be specified (of course this question would
be just as valid for the anomaly form)? There are several available
climatologies and it is important to capture which is used in a standard
fashion.
Kind regards
Julian
On Fri, 2006-12-01 at 18:51 +0000, Jonathan Gregory wrote:
> Dear Julian
>
> I have two issues concerning your two standard names!
>
> assuming_night: I think it would be more appropriate to regard an average over
> night as a particular kind of time-processing rather than an assumed condition.
> I would therefore suggest a cell_methods entry of "time: mean (night)". That
> is legal, but not standardised, since most things in () in cell_methods are
> regarded as comments. If it is commonly needed, "night" could be standardised.
>
> anomaly: At present there are four "anomaly" standard names in the table, but
> I tend to think that they are a mistake to have included, because (a) it is
> not well defined what "anomaly" means and (b) every quantity might be
> anomalised, doubling the size of the stdname table. For other cases like (b)
> we introduced standard name modifiers, so I would propose we introduce a
> modifier of "difference_from_climatology", which is more explicit than
> "anomaly". You would then use
> standard_name="air_temperature difference_from_climatology".
>
> What do you think?
>
> Best wishes
>
> Jonathan
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--
Dr Julian Hill Marine Data Research Scientist
Met Office Hadley Centre for Climate Prediction and Research
FitzRoy Road Exeter EX1 3PB United Kingdom
Tel: +44 (0)1392 884278 Fax: +44(0)1392 885681
"Making our forecasts essential to everyone, every day."
Received on Mon Dec 04 2006 - 01:47:27 GMT
