Hello Jonathan (W),
As far as the four sea surface temperature standard names go, they refer to the temperature of different thicknesses at the top of the water column. Roughly speaking these are:
sea_surface_temperature - top 10-20m
sea_surface_foundation_temperature - top 1-5m
sea_surface_subskin_temperature - top couple of mm
sea_surface_skin_temperature - top 10-20 microns
I think your confusion may be caused by what I think is an error in the definition of sea_surface_temperature, which currently states 'and not the skin temperature, whose standard name is surface_temperature'. This should surely read 'and not the skin temperature, whose standard name is surface_skin_temperature'.
My understanding of air-sea interface temperature is that it is the temperature of thin layers of air and water that are in physical contact. I would expect these to be numerically equal and correspond to the Standard Names 'sea_surface_skin_temperature' and 'surface_temperature_where_open_sea'.
Hope this helps.
Cheers, Roy.
From: CF-metadata [cf-metadata-bounces at cgd.ucar.edu] On Behalf Of Jonathan Wrotny [jwrotny at aer.com]
Sent: 13 June 2013 18:04
To: Jonathan Gregory
Cc: cf-metadata at cgd.ucar.edu List; Karl Taylor
Subject: Re: [CF-metadata] new standard name: land_surface_skin_temperature
Dear Jonathan Gregory,
A few days ago, I submitted a proposal for a new standard name, land_surface_skin_temperature. This name would essentially be the land analogue for the "sea_surface_skin_temperature" standard name. However, through some of the dialogue on the CF mailing list re: this submission, a few related questions have arose:
1) What is meaning of the "surface_temperature" standard name? The definition states that it is the temperature of the interface, and not the medium above or below. What does this mean? There has be some medium to have a temperature.
2) The "sea_surface_temperature" definition seems to incorrectly refer to the "surface_temperature", when it should refer instead to the "sea_surface_skin_temperature." But, I can't say this for sure in light of question #1.
3) Karl Taylor has raised the question that if someone searches for surface temperature, this is the same as the skin temperature. So, there could be some ambiguity between the surface temperature and surface skin temperature names in CF, which may or may not be intended.
4) After question #1-3 are determined, this should presumably make it easier to determine the role of the proposed "land_surface_skin_temperature" name.
Sorry to put so many questions in one post, but it seemed like my latest post generated several questions, and I thought putting them all in one place might make things a little less confusing. Thanks in advance for your feedback.
Sincerely,
Jonathan Wrotny
On 6/10/2013 12:54 PM, Jonathan Wrotny wrote:
Jim,
This is a good question and you raise a good point. I have to admit that I too am a little confused by the definition of "surface temperature" in the CF database. My initial interpretation was that this quantity refers to the temperature at the lowest level of the atmosphere, i.e. just above the surface, so that it is actually an air temperature. But, how can the "surface temperature" be an air temperature (or a skin temperature, for that matter) if it is "not the bulk temperature of the medium above or below (the interface)"?
Could someone help please clarify the "surface temperature" quantity?
Jonathan Wrotny
On 6/10/2013 12:30 PM, Jim Biard wrote:
I'd appreciate it if someone would take the time to help an ignorant soul understand how a non-physical boundary such as the interface between the land surface and the atmosphere can have a temperature. It sure seems to me that you need some material in order to have a temperature, and such an interface seems to have none.
Jim Biard
Research Scholar
Cooperative Institute for Climate and Satellites
Remote Sensing and Applications Division
National Climatic Data Center
151 Patton Ave, Asheville, NC 28801-5001
jim.biard at noaa.gov
828-271-4900
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On Jun 10, 2013, at 11:52 AM, Jonathan Wrotny <jwrotny at aer.com> wrote:
Dear Jonathan Gregory,
I have not yet replied to this e-mail yet from you...thanks for the information on the meaning of the various surface temperatures.
Yes, the land skin temperature is actually different from the "surface_temperature" standard name since it corresponds to the skin, and not the interface, temperature. So, I do believe that an additional name will need to be added to account for this land analogue to "sea_surface_skin_temperature." Here is my current proposal:
Standard Name: land_surface_skin_temperature
Definition: The surface called "surface" means the lower boundary of the atmosphere. The land surface skin temperature is the temperature measured by an infrared radiometer, but measurements from microwave radiometers operating at GHz wavelengths also exist. It represents the aggregate temperature of the skin surface where ?skin? means the surface medium viewed by a sensor to a vertical depth of approximately 12 micrometers.
Measurements of this quantity are subject to a large potential diurnal cycle which is primarily due to the balance between heating during the day by solar radiation and continual cooling from terrestrial (long-wave) radiation emitted by the skin surface.
Canonical Units: K
Sincerely,
Jonathan
On 6/7/2013 3:47 AM, Jonathan Gregory wrote:
Dear Jonathan W
If my interpretation of all of the surface temperature names is
correct, then there may need to be a modification to the current
definition of "sea_surface_temperature." In particular, this
definition states "It is the temperature of sea water near the
surface (including the part under sea-ice, if any), and not the skin
temperature, whose standard name is surface_temperature." However,
it seems to me that the "surface_temperature" is the
atmosphere/medium interface temperature, and not the temperature of
the medium below the interface (e.g. the skin temperature). So, I'm
wondering if the above sentence in quotes incorrectly refers to the
"surface_temperature" when perhaps it should refer to the
"sea_surface_skin_temperature"?
Yes, I think you are right. This definition of sea_surface_temperature may
predate the introduction of sea_surface_skin_temperature. The SST is neither
the true interface temperature (for which the name is surface_temperature) nor
the "skin" temperature, but a bulk temperature applying to a rather ill-defined
upper layer of the ocean. There isn't a land analogue for SST.
If land skin temperature is different from surface_temperature of the
interface, a new name is needed for it, I agree.
Cheers
Jonathan
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