Jim,
We're only half disagreeing. When there is a lake (or ice/snow?) on top of
the land, you are talking about the radiative surface at the bottom of the
atmosphere, not the top of the dirt. If I understand correctly, you only
make a special case for designated oceans.
So a more precise name might be "nonsea_surface_skin_temperature".
Then if we have 50/50 land & lake with T=310 and 290:
nonsea_surface_skin_temperature=300
sea_surface_skin_temperature=(fill value)
But 50/50 land & sea with T=310 and 290:
nonsea_surface_skin_temperature=310
sea_surface_skin_temperature=290
Ice on land would presumably be counted as land but sea ice could still be
counted as either land or sea with this terminology.
so if we have 4 equal portions
1/4 non-ice-covered non-sea (land/lake/vegetation/whatever) T=290
1/4 ice-covered non-sea T=270
1/4 non ice-covered sea T=280
1/4 ice-covered sea T=260
Then either we count sea ice as sea:
nonsea_surface_skin_temperature=280 (men of 270 and 290)
sea_surface_skin_temperature=270 (mean of 260 and 280)
Or sea ice is not sea:
nonsea_surface_skin_temperature=273.3 (men of 260, 270 and 290)
sea_surface_skin_temperature=280
-- Evan
On Tue, Jul 16, 2013 at 9:36 AM, Jim Biard <jim.biard at noaa.gov> wrote:
> Evan,
>
> I'm afraid I have to disagree. I'm working with the MODIS and VIIRS Land
> Surface Temperature products right now, and they are attempting to report
> the temperatures of the soil/rock/plants/water/etc themselves. The sea
> surface is masked off, but temperature for water such as lakes and rivers
> (and puddles) is reported. The emissivities of the various surface
> constituents are used in the algorithms that generate the products. The
> top surface of the land is definitely what is of interest. To give one
> example, the products are used in drought studies, where they are used to
> try and determine how wet the soil is.
>
> 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
>
> jim.biard at noaa.gov
> 828-271-4900
>
>
>
> Follow us on Facebook <https://www.facebook.com/cicsnc>!
>
> On Jul 16, 2013, at 11:59 AM, Evan Manning <Evan.M.Manning at jpl.nasa.gov>
> wrote:
>
> The rewording specifies that puddles are "land". What about ponds?
> lakes? rivers? great lakes? Oceans?
>
> What if we have a grid square that is 50% land at 310 K and 50% ocean at
> 290 K?
> Would it be correct to have these two variables associated with it:
> sea_surface_skin_temperature=290
> land_surface_skin_temperature=310 (i.e. T of only the non-sea portion)
> or:
> sea_surface_skin_temperature=290
> land_surface_skin_temperature=300 (i.e. mean T of land & sea portions)
>
> How does that change if instead of being 50% ocean it is 50% lakes &
> rivers?
> Or lots and lots of puddles?
>
> I think what we're interested in is not so much the top surface of the
> land as the
> lower boundary of the atmosphere. So I like "surface_skin_temperature",
> which
> could then be used with a dimension for surface categories.
>
> -- Evan
>
> About a month ago, I submitted a new standard name for the
> "land_surface_skin_temperature." While I think the consensus is now that
> this new name seems acceptable for inclusion in the CF database, there were
> some comments and suggestions by various people who pointed out that the
> proposed definition for this quantity could use some more clarification and
> other comments which pointed out similarities to the current name
> "surface_temperature." I've attempted to address both of these concerns by
> adding another line to the definition which better defines what the
> "land_surface_skin" is. My hope is that this clears up some uncertainty
> about this quantity (e.g. it is not simply the bare land surface but also
> includes various media above the land surface) and also illustrates that it
> is not the same thing as the "surface_temperature" quantity (which I
> understand as idealized, infinitesimally thin interface temperature between
> the air and land/sea and not the observable quantity that the
> "land_surface_skin_temperature" proposes to be).
>
> With this is mind, here is my latest attempt at this new name/definition:
>
> Standard Name: land_surface_skin_temperature
>
>
>
> Definition: The land surface skin temperature is the aggregate
> temperature of the ?land surface skin,? which is the portion of the land
> surface which emits infrared radiation directly to space through the
> atmosphere. The ?land surface skin? is defined as an effective layer which
> includes the upper boundary of the land combined with additional layers
> which may cover the upper land boundary (e.g. vegetation, puddles, snow,
> ice, man-made objects).
>
>
>
> Canonical Units: K
>
>
> Sincerely,
>
> Jonathan
>
> On 6/20/2013 7:56 AM, Jonathan Gregory wrote:
>
> Dear Karl
>
> Like Roy, I don't think we should deprecate sea_surface_skin_temperature.
> Although I cannot remember the arguments - which must be apparent in the
> mailing list archive - I do recall that it was a careful and long
> discussion
> with Craig which led to the introduction of the various SST names.
>
> Therefore adding land_surface_skin_temperature seems fine to me if there is
> a need to be precise about this as an observable quantity, which relates
> to a particular layer, even though it's very thin. The definition should
> note
> that if this precise meaning is not intended, the name surface_temperature
> could be used, which strictly refers to the temperature at the interface.
>
> Best wishes
>
> Jonathan
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