Just a data point: Back in the day, I was told (on-list I thought) that sea_surface_temperature was effectively deprecated, at least for measurements. I understood that to be the reason for the explicit language that it was _not_ any of the other concepts -- just to make clear people should not be using it.
john
--------------------------------------
John Graybeal
jbgraybeal at mindspring.com
On Mar 7, 2016, at 17:47, Karl Taylor <taylor13 at llnl.gov> wrote:
> 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: pminnett at 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.pamment at 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.pamment at stfc.ac.uk
>>> STFC Rutherford Appleton Laboratory
>>> R25, 2.22
>>> Harwell Campus, Didcot, OX11 0QX, U.K.
>>>
>>>
>>> From: Craig Donlon [mailto:craig.donlon at esa.int]
>>> Sent: 07 March 2016 02:18
>>> To: Pamment, Alison (STFC,RAL,RALSP)
>>> Cc: taylor13 at llnl.gov; cf-metadata at 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.donlon at 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.pamment at stfc.ac.uk> <alison.pamment at 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.pamment at stfc.ac.uk
>>> STFC Rutherford Appleton Laboratory
>>> R25, 2.22
>>> Harwell Campus, Didcot, OX11 0QX, U.K.
>>>
>>>
>>> From: CF-metadata [mailto:cf-metadata-bounces at cgd.ucar.edu] On Behalf Of Karl Taylor
>>> Sent: 02 March 2016 20:26
>>> To: cf-metadata at 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, alison.pamment at 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.pamment at stfc.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 at 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: cf-metadata at 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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