As I understand it, the reason for the introduction of the skin temperature (and other sea surface temperatures) is that originally sea_surface_temperature encompassed everything (in its 100 years of use) from a bucket somewhere in the first 10 meters, to a satellite measuring the first few millimeters. More precise names were needed.
I expect a similar situation applies on land. Even if past practice may only penetrate the service 10 centimeters, that's noticeably different than a satellite measuring a few millimeters. If that's at all true, having the refined term makes sense to me. John On Jun 17, 2013, at 05:41, Jonathan Gregory <[email protected]> wrote: > Dear Jonathan and Jim > > In my previous email, I was trying to explain why an interface temperature > is a physical meaningful concept, which Jonathan asked about. This is actually > an applicable concept in models, as I said, and it is the idea which I (at > least) had in mind when the name was put in the standard name table. Like CF > in general, the standard name table was originally created for the purpose of > model metadata, and was later to extended to observations. This quantity is an > idealisation, not an observable quantity. > > The heat capacity of a layer 12 micrometers thick is so small that I suppose > there is practically no difference between the skin temperature and the > interface temperature, on the timescales you're interested in. Is that > correct, > do you think? If so, it seems to me that it would be fine to use the existing > name of surface_temperature for this quantity. You propose the new name on the > analogy of the sea_surface_skin_temperature. The same argument would apply to > that as well. I can't remember the reason why it was thought necessary to make > a distinction between surface_temperature and sea_surface_skin_temperature, > though I do recall quite a lot of discussion about it. > > It is also fine to introduce land_surface_skin_temperature as well, I would > say. The data-writer has a choice. They could use surface_temperature if that > is accurate enough, but if they wish to be more precise about what material > layer it applies to, the skin temperature names could be used. > > Best wishes > > Jonathan > > 13/06/17 13:20:03 house > On Fri, Jun 14, 2013 at 02:45:28PM -0400, Jonathan Wrotny wrote: >> Date: Fri, 14 Jun 2013 14:45:28 -0400 >> From: Jonathan Wrotny <[email protected]> >> User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:17.0) Gecko/20130509 >> Thunderbird/17.0.6 >> To: Jim Biard <[email protected]> >> CC: "[email protected] List" <[email protected]> >> Subject: Re: [CF-metadata] new standard name: land_surface_skin_temperature >> >> Dear Jim, >> >> Thanks for your comments. They all make sense to me and I'm on >> board with your suggested definition. I'll just wait for others to >> comment, if needed, then we can converge on a final definition. >> Sincerely, >> >> Jonathan >> >> On 6/14/2013 2:11 PM, Jim Biard wrote: >>> Jonathan, >>> >>> I still don't believe that the surface temperature concept that >>> Jonathan Gregory has ever been what people were intending when >>> they make the surface_temperature standard name, but I'll abide by >>> whatever folks decide. >>> >>> On a different front, I don't think the definition of the standard >>> name should include statements about technology used (measured by >>> an infrared radiometer?). The definition should speak only to the >>> measured quantity, without reference to the way in which you >>> happen to be measuring it. Likewise, there is no need for the >>> statement regarding variability of the quantity. Also, the >>> surface in this name is not the lower boundary of the atmosphere. >>> It is the upper boundary of the land. An non-volatile object in a >>> hard vacuum has a surface skin temperature. >>> >>> Given all that, I'd suggest this for your definition: >>> >>> Standard Name: land_surface_skin_temperature >>> >>> Definition: The land surface skin temperature is the aggregate >>> temperature of the "skin" of the land surface, which extends >>> vertically approximately 12 micrometers below the land surface. >>> >>> If people really think it needs to be spelled out even further, >>> add the sentence "The land surface is the upper boundary of the >>> land." >>> >>> Grace and peace, >>> >>> Jim >>> >>> Jim Biard >>> Research Scholar >>> Cooperative Institute for Climate and Satellites <http://www.cicsnc.org/> >>> Remote Sensing and Applications Division >>> National Climatic Data Center <http://www.ncdc.noaa.gov/> >>> 151 Patton Ave, Asheville, NC 28801-5001 >>> >>> [email protected] <mailto:[email protected]> >>> 828-271-4900 >>> >>> >>> >>> Follow us onFacebook <https://www.facebook.com/cicsnc>! >>> >>> On Jun 14, 2013, at 1:54 PM, Jonathan Wrotny <[email protected] >>> <mailto:[email protected]>> wrote: >>> >>>> Dear Jonathan Gregory, >>>> >>>> Thanks for your reply...this certainly helps to clear things up >>>> for me. I now better understand the meaning of the >>>> "surface_temperature" standard name with the temperature defined >>>> by heat fluxes at an interface, and not based on an actual >>>> medium. >>>> >>>> This also makes it obvious to me that my proposed standard name >>>> "land_surface_skin_temperature" does not currently exist within >>>> CF and could serve as an analogue to >>>> "sea_surface_skin_temperature." To summarize, 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 Wrotny >>>> >>>> On 6/14/2013 1:22 PM, Jonathan Gregory wrote: >>>>> Dear Jonathan >>>>> >>>>> I defer to Roy about the various sea water temperature names. >>>>> >>>>> It is physically meaningful to have a temperature which doesn't relate to >>>>> any >>>>> material layer. If there is no matter associated with it, it must have >>>>> zero >>>>> heat capacity, so the temperature is determined by requiring an exact >>>>> balance >>>>> of heat fluxes. For this to be possible, the heat fluxes concerned must >>>>> depend >>>>> on the temperature, which of course they generally do. Obviously this is >>>>> an >>>>> idealisation, but a surface interface temperature of this kind really can >>>>> exist in a model, although it's not an observational quantity. A model can >>>>> obtain such a temperature by solving simultaneously for the heat fluxes >>>>> that >>>>> are balanced at the interface. >>>>> >>>>> Best wishes >>>>> >>>>> Jonathan G >>>>> _______________________________________________ >>>>> CF-metadata mailing list >>>>> [email protected] >>>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >>>> >>>> _______________________________________________ >>>> CF-metadata mailing list >>>> [email protected] <mailto:[email protected]> >>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >>> >> > >> _______________________________________________ >> CF-metadata mailing list >> [email protected] >> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > > _______________________________________________ > CF-metadata mailing list > [email protected] > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata ------------------------------------ John Graybeal Senior Data Manager, Metadata and Semantics T +1 (408) 675-5545 F +1 (408) 616-1626 skype: graybealski Marinexplore 920 Stewart Drive Sunnyvale, CA _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
