Dear Karl
As I wrote in a previous posting, I think surface_temperature is either a some-
what vague concept, to be used when it is not critical to say exactly what is
meant (that's fine - standard names have always supported a range of precision
in concepts), or it's an idealisation which really refers to an energy balance
at the interface. The latter concept is applicable in models, and then does
not necessarily have any matter associated with it.
Best wishes
Jonathan
----- Forwarded message from Karl Taylor <taylor13 at llnl.gov> -----
> Date: Thu, 20 Jun 2013 09:15:36 -0700
> From: Karl Taylor <taylor13 at llnl.gov>
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> To: cf-metadata at cgd.ucar.edu
> Subject: Re: [CF-metadata] new standard name: land_surface_skin_temperature
>
> Dear all,
>
> O.K. I withdraw my suggestion to deprecate sea_surface_skin_temperature.
>
> I do think the definitions should say how skin temperature differs
> from surface temperature. Maybe someone can explain that in a few
> words.
>
> As I understand it, temperature is only defined when molecules are
> involved. So surface_temperature I think should be defined as the
> temperature of the surface molecules on the ocean or land/vegetated
> surface. I don't think there are any useful observational
> measurements of this temperature either in the ocean or land.
> Models do calculate these a surface temperature, and as I understand
> it models use this as their surface radiating temperature so in that
> sense the temperature is identical to skin_temperature, I would
> think.
>
> It sounds to me like in land observations, at least, the
> skin_temperature is not precisely defined because the effective
> radiating layer depends presumably on what wavelengths are being
> sensed. To precisely say what the temperature represents one would
> have to show what fraction of the radiation originated from
> different depths. saying 10-20 microns of course gives an idea
> about this, but it isn't precise.
>
> Also, the definition of land_surface_skin_temperature should clearly
> indicate (when it represents an area mean) whether it is meant to be
> the area mean of the soil or of the "solid or liquid surface" as
> seen from above which might include vegetation, puddles, etc. [as
> an aside, I wonder if the thickness of the layer producing the
> radiation varies much from one material to the next.]
>
> It does seem a shame to me that users looking for
> surface_temperature information will now have to search both for
> surface_temperature and surface_skin_temperature, but I'll accede to
> the clear majority that thinks both are necessary.
>
> best regards,
> Karl
>
> On 6/20/13 4:56 AM, Jonathan Gregory wrote:
> >Dear Karl
> >
> >Like Roy, I don't think we should deprecate sea_surface_skin_temperature.
> >Although I cannot remember the arguments - which must be apparent in the
> >mailing list archive - I do recall that it was a careful and long discussion
> >with Craig which led to the introduction of the various SST names.
> >
> >Therefore adding land_surface_skin_temperature seems fine to me if there is
> >a need to be precise about this as an observable quantity, which relates
> >to a particular layer, even though it's very thin. The definition should note
> >that if this precise meaning is not intended, the name surface_temperature
> >could be used, which strictly refers to the temperature at the interface.
> >
> >Best wishes
> >
> >Jonathan
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----- End forwarded message -----
Received on Thu Jun 20 2013 - 10:24:58 BST
