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<mailto:J.A.Pamment at rl.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<mailto: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<mailto:J.A.Pamment at 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 at cgd.ucar.edu<mailto: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<mailto: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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