Hello All,
Karl has raised an objection to the wording ".... not the skin ...." which was carried
over from the current CF Standard Name definition for sea_surface_temperature in my suggested
update. The update is intended to correct a currently erroneous reference to
"surface_temperature" as skin temperature. Karl's objection, which also applies to the
existing definition (and appears to date back to v1 fo the list), could be accomodated by a simple
change:
‘Sea surface temperature is usually abbreviated as "SST". It
is the temperature of sea water near the surface (including
the part under sea-ice, if any). More specific terms
sea_surface_skin_temperature and surface_temperature
are available for the skin and interface
temperature respectively. For the temperature of sea water at a
particular depth or layer, a data variable of
sea_water_temperature with a vertical coordinate axis should
be used.’
regards,
Martin
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Today's Topics:
1. Re: Confusing skin temperature and interface temperature
(Karl Taylor)
----------------------------------------------------------------------
Message: 1
Date: Mon, 7 Mar 2016 17:47:05 -0800
From: Karl Taylor <taylo...@llnl.gov>
To: Peter Minnett <pminn...@rsmas.miami.edu>,
alison.pamm...@stfc.ac.uk, craig.don...@esa.int
Cc: cf-metadata@cgd.ucar.edu, kenneth.ca...@noaa.gov,
anne.ocarr...@eumetsat.int, edward.m.armstr...@jpl.nasa.gov
Subject: Re: [CF-metadata] Confusing skin temperature and interface
temperature
Message-ID: <56de2f19.2080...@llnl.gov>
Content-Type: text/plain; charset="utf-8"; Format="flowed"
Dear Peter, Craig and all,
For observations I am not arguing that all the different ocean
temperature definitions aren't needed. In describing observations I
understand that skin and surface temperature are not identical. My
statement was that by construction (almost all) current models assume
that the temperature is vertically uniform (i.e., the water is perfectly
mixed and homogeneous) throughout the upper most layer, so in *those*
models the statement that the "sea_surface_temperature" is "not the skin
or interface temperature" is *wrong*.
The CF standard name description of "sea_surface_temperature" is
somewhat vague by design: "the temperature of sea water near the
surface". Because it is vague, it *could* defensibly be used to
represent any more precisely defined near-surface temperature, including
"sea_surface_skin_temperature", "sea_surface_subskin_temperature", or
"sea_surface_foundation_temperature".
Even for observations it would be wrong to say "sea water near the
surface is not the skin temperature".
Since skin temperature is near the surface and sea_surface_temperature
is vague, it might in fact be the same as skin temperature (e.g., if
sea_surface_temperature in fact recorded the conductive
diffusion-dominated sub-layer at a depth of approximately 10-20
micrometers below the air-sea interface). Again, usually in models,
sea_surface_temperature most emphatically does provide the model's best
(only!) estimate of skin temperature.
If the description were changed to read:
"It is the temperature of sea water near the surface (including the part
under sea-ice, if any), and not necessarily the skin temperature".
I would be happy.
Better yet, why not include in the discussion the following points:
1) surface temperature, sea_surface_temperature,
sea_surface_skin_temperature, sea_surface_subskin_temperature, and
sea_surface_foundation_temperature are all terms that might apply to the
temperature of sea water.
2) When the temperature represents a horizontal spatial average,
surface_temperature represents the mean of the temperature over all
surface types in the domain, whereas the other temperatures do not.
3) The sea_surface_temperature is imprecise because it represents a
near-surface temperature sampled within (or averaged over) the portion
of the column extending from the surface down to perhaps several
meters. In many ocean models, the temperature does not vary in that
portion of the column so sea_surface_temperature might be the
appropriate standard_name. Note that in this case, if part of the
horizontal domain represented by this temperature is under sea ice, the
temperature would not be the same as surface_temperature (which would
include contributions from the surface of the sea ice).
4) The other CF standard names for ocean temperatures have more precise
definitions, and so those names should be used whenever they apply.
best regards,
Karl
On 3/7/16 7:06 AM, Peter Minnett wrote:
Dear Alison, Craig, Karl et al.,
I have refrained from entering this discussion until now as Craig has
made the points carefully and succinctly. But I think there's a
fundamental issue at stake about what these definitions are for.
My view is that definitions such as these are intended to provide a
framework for communication that accurately but briefly represents our
best understanding of the physics of the upper ocean and lower
atmosphere. Thus, the definitions should not be constrained, or
adapted, to reflect our current measurement or modelling capabilities
as these, we expect, will improve with time. If, at some point in the
future, we learn something new about how the thermal structure of the
upper ocean behaves, then maybe the definitions will have to be
revised, but for now I believe our definitions should be based on our
understanding of the physical behavior of sea water near the air-sea
interface. And this is what we tried to achieve with the GHRSST
definitions.
Best regards,
Peter
--------------------------------------------------------
Peter J. Minnett
Professor, Department of Ocean Sciences
Speaker, RSMAS School Council.
Rosenstiel School of Marine and Atmospheric Science
University of Miami
4600 Rickenbacker Causeway
Miami, FL 33149-1031, USA
Chairman, Science Team of the Group for High Resolution Sea-Surface
Temperature (GHRSST)
Tel: +1 (305) 421-4104 Fax: +1 (305) 421-4696
email: pminn...@rsmas.miami.edu
http://www.rsmas.miami.edu/people/faculty-index/?p=peter-minnett
https://www.ghrsst.org/
On 3/7/2016 6:41 AM, alison.pamm...@stfc.ac.uk wrote:
Dear Craig and Karl,
Thanks both for your comments. It is clear that we need some more
discussion on this topic. I will be making an update to the standard
name table tomorrow but will defer any changes to the sea surface
temperature names until we can all agree a position on this.
Best wishes,
Alison
------
Alison Pamment Tel: +44 1235 778065
Centre for Environmental Data Analysis Email:
alison.pamm...@stfc.ac.uk <mailto:j.a.pamm...@rl.ac.uk>
STFC Rutherford Appleton Laboratory
R25, 2.22
Harwell Campus, Didcot, OX11 0QX, U.K.
*From:*Craig Donlon [mailto:craig.don...@esa.int]
*Sent:* 07 March 2016 02:18
*To:* Pamment, Alison (STFC,RAL,RALSP)
*Cc:* taylo...@llnl.gov; cf-metadata@cgd.ucar.edu; Kenneth Casey;
Peter Minnett; Anne O'Caroll; Edward Armstrong
*Subject:* Re: [CF-metadata] Confusing skin temperature and interface
temperature
Dear Alison and Karl:
Thanks for the discussion here. The key issue is that model teams
need to be more precise as to which SST variable is being used. As
more advanced systems begin to fully couple ocean and atmosphere,
begin to perform radiance assimilation etc the need for each of the
different SST variables becomes readily apparent.
I would not like to see any of the current CF SST definitions watered
down in the manner proposed. But rather to ask Karl to define what
he means by SST in the modelling context that he is working?
Then we may hope to resolve the issue efficiently.
Regards
Craig
--
*** Sent from my iPhone ***
--
Dr Craig Donlon
Sentinel-3 Mission Scientist,
Principal Scientist for Oceans and Ice
European Space Agency/ESTEC
Keplerlaan 1, 2201 AZ
Noordwijk
The Netherlands
e: craig.don...@esa.int
t: +31 (0)715 653687
f: +31 (0)715 655675
m: +31 (0)627 013244
Skype: crazit
On 3 Mar 2016, at 19:53, <alison.pamm...@stfc.ac.uk
<mailto:alison.pamm...@stfc.ac.uk>> <alison.pamm...@stfc.ac.uk
<mailto:alison.pamm...@stfc.ac.uk>> wrote:
Dear Karl,
Thanks for your comments on this. Clearly we need to get this
right before I make any changes in the standard name table.
I recall that the sea surface skin, subskin and foundation
temperatures were introduced primarily to describe satellite
radiometer data because the existing sea_surface_temperature name
was too vague. I have the impression that modellers sometimes use
the word ?skin? as being synonymous with the interface at the
bottom of the atmosphere and I think that was probably the
intention behind its use in the current definition. By contrast,
the observational community have a very specific definition for
the sea skin: ?the conductive diffusion-dominated sub-layer at a
depth of approximately 10 - 20 micrometers below the air-sea
interface?. So I think there is scope for some confusion here
since the more specific sea surface temperature names were
introduced.
As far as standard name definitions are concerned, the main thing
is to ensure we provide clear guidance as to when a particular
name should be used and to explain the relationships between
similar names. I take your point that some models may be
deliberately formulated to have sea_surface_temperature (by which
I assume you mean the top layer of the model) the same as the
interface temperature. I assume you would still label it with a
standard name of sea_surface_temperature, even though in this
case it would be directly comparable with a variable with
standard name surface_temperature and we should probably explain
that in the definition.
Do models ever output variables that you would actually want
label as ?skin?, ?subskin? or ?foundation? temperatures (as
defined in the existing standard names)? If not, then perhaps it
is best to simply note in the definition that the other names
exist and that they have very specific definitions. This avoids
the issue around the word ?skin?.
These points would then lead to a definition something like the
following:
?Sea surface temperature is usually abbreviated as "SST". It is
the temperature of sea water near the surface (including the part
under sea-ice, if any), and is not necessarily the same as the
interface temperature at the bottom of the atmosphere, whose
standard name is surface_temperature. Some models are formulated
such that sea_surface_temperature and surface_temperature are the
same in ice free sea areas. The standard names
sea_surface_skin_temperature, sea_surface_subskin_temperature and
sea_surface_foundation_temperature can be used to describe the
temperature in specific layers close to the sea surface and are
often used to describe satellite observations. For the
temperature of sea water at a particular depth or layer, a
standard name of sea_water_temperature with a vertical coordinate
axis should be used.?
Does that sound OK? Does it include all the necessary information?
Best wishes,
Alison
------
Alison Pamment Tel: +44 1235 778065
Centre for Environmental Data Analysis Email:
alison.pamm...@stfc.ac.uk <mailto:j.a.pamm...@rl.ac.uk>
STFC Rutherford Appleton Laboratory
R25, 2.22
Harwell Campus, Didcot, OX11 0QX, U.K.
*From:*CF-metadata [mailto:cf-metadata-boun...@cgd.ucar.edu] *On
Behalf Of *Karl Taylor
*Sent:* 02 March 2016 20:26
*To:* cf-metadata@cgd.ucar.edu <mailto:cf-metadata@cgd.ucar.edu>
*Subject:* Re: [CF-metadata] Confusing skin temperature and
interface temperature
Dear Alison and all,
For "sea_surface_temperature", there is a problem stating
definitively that it is "not the skin or interface temperature".
In most models the skin and interface temperatures over ice-free
(i.e., open) ocean are indeed the same as sea_surface_temperature
(by construction). I think it would be more accurate (and less
misleading) to say it is "not *necessarily* the skin or interface
temperature". You could also add to the list
"sea_surface_foundation_temperature" here because in models it
too is often the same as sea_surface_temperature". Models are
evolving, so this might not indefinitely be the case.
thanks,
Karl
On 3/2/16 9:40 AM,
<mailto:alison.pamm...@stfc.ac.uk>alison.pamm...@stfc.ac.uk wrote:
Dear Martin, All,
No objections have been received to the proposed definition
change and it is now accepted for publication in the standard
name table.
The name will in future appear as:
sea_surface_temperature (canonical units: K)
?Sea surface temperature is usually abbreviated as "SST". It
is the temperature of sea water near the surface (including
the part under sea-ice, if any), not the skin or interface
temperature, whose standard names are
sea_surface_skin_temperature and surface_temperature,
respectively. For the temperature of sea water at a
particular depth or layer, a data variable of
sea_water_temperature with a vertical coordinate axis should
be used.?
In response to Martin?s proposal I received an email from
Craig Donlon (original proposer of many of the current
sea_surface_X_temperature names). Craig and his team support
the Martin?s proposal and additionally point out an error
that occurs in the definition of the following names:
sea_surface_skin_temperature
sea_surface_subskin_temperature
in which the first sentence reads ?The surface called
"surface" means the lower boundary of the atmosphere? even
though the temperatures are not in fact measured at the
sea-air boundary. The suggestion is to delete the initial
sentence from the definitions. I note also that a similar
situation currently exists with the standard name
sea_surface_foundation_temperature even though that
temperature generally refers to a depth of 1 ? 5 m below the
sea surface.
I agree with Craig that the sentence should be deleted. I
think it was probably included by accident because most
?surface? standard names do indeed refer to the interface
between the bottom of the atmosphere and whatever lies
beneath. I plan to remove the sentence from the definitions
of these three names at the next standard name table update
unless any objections are received in the meantime.
Best wishes,
Alison
------
Alison Pamment Tel: +44 1235 778065
Centre for Environmental Data Analysis Email:
alison.pamm...@stfc.ac.uk <mailto:j.a.pamm...@rl.ac.uk>
STFC Rutherford Appleton Laboratory
R25, 2.22
Harwell Campus, Didcot, OX11 0QX, U.K.
*From:*Pamment, Alison (STFC,RAL,RALSP)
*Sent:* 03 February 2016 15:32
*To:* Juckes, Martin (STFC,RAL,RALSP);
cf-metadata@cgd.ucar.edu <mailto:cf-metadata@cgd.ucar.edu>
*Subject:* RE: Confusing skin temperature and interface
temperature
Dear Martin,
Thank you for pointing this out. I agree that since the
introduction of the very precisely defined
sea_surface_skin_temperature name, the definition of the more
generic name is confusing. I agree with your suggested
amendment and unless anyone objects within the next seven
days the change will be accepted and added at the next update
of the standard name table.
Best wishes,
Alison
*From:*Juckes, Martin (STFC,RAL,RALSP)
*Sent:* 02 February 2016 16:07
*To:*
<mailto:cf-metadata@cgd.ucar.edu>cf-metadata@cgd.ucar.edu;
Pamment, Alison (STFC,RAL,RALSP)
*Subject:* Confusing skin temperature and interface temperature
Hello All,
The CF Standard Name sea_surface_temperature includes the
statement that it is "./... not the skin temperature, whose
standard name is surface_temperature/". The last phrase here
is incorrect: the standard name of the skin temperature
is/sea_surface_skin_temperature/, not /surface_temperature/.
Can the definition be modified to read ".. /not the skin or
interface temperature, whose standard names are
sea_surface_skin_temperature and surface_temperature
respectively/"?
regards,
Martin
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