Dear John,
I agree that sea_surface_temperature is vague, and when possible folks
should specify instead foundation, subskin, skin, or
surface_temperature. No one has yet said what the difference is between
skin temperature and surface_temperature, so I guess you could
substitute one for the other, as you wish.
cheers,
Karl
On 6/20/13 10:58 AM, John Graybeal wrote:
Confirming what Jonathan says, sea_surface_temperature was was used to describe
data (including observations going many decades back) that reflected a variety
of locations -- right at the interface (with remote sensors), or varying
distances under the skin (with in situ sensors, including buckets dipped in the
water and measured on the ship). The existing body of data using that concept
made it broad beyond utility.
The somewhat sloppy vertical range definitions were influenced by measurement
technologies and the physics underlying them.
The recommended practice, at the conclusion of the process adding the 3 new
variables, was that no new data should use the term sea_surface_temperature,
because it was too meaningless. (Not sure if that got captured anywhere in the
definitions.) All new data should use one of the 3 new concepts (skin, subskin,
foundation), according to the precise meaning. There was discussion of
deprecating the original term, but people felt it was necessary at times, e.g.
for older data sets with unknown measurement characteristics.
John
On Jun 20, 2013, at 09:24, Jonathan Gregory <[email protected]> wrote:
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 <[email protected]> -----
Date: Thu, 20 Jun 2013 09:15:36 -0700
From: Karl Taylor <[email protected]>
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.5; rv:16.0)
Gecko/20121026 Thunderbird/16.0.2
To: [email protected]
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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John Graybeal
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Marinexplore
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