Dear all,
I think the common meaning of "land" in climate models and in climate
observations distinguishes "terrestrial" regions from "marine" regions.
Thus, we have terrestrial plants, terrestrial water storage, terrestrial
water fluxes, terrestrial glaciers (which seems a bit redundant), etc.,
and all of these comprise the "land" surface. Thus, in CF, I think
"land" should include all it's components: vegetation, lakes, puddles,
snow, glacial ice, etc. Sea ice, on the other hand, belongs to the
marine environment and should be considered "sea".
The above division fits nicely into how most models treat these two very
different regions. Usually sea ice is part of the ocean model (or
closely coupled to it, since the ocean can move sea ice around), and the
"land model" can include all the land components, from vegetation to snow.
I therefore think we should avoid terms as "nonsea", as that would be
identical to "land".
I agree that there seems to be a consensus that we adopt a new standard
name -- land_surface_skin_temperature .
To help users understand that it is likely to be a measure of the same
thing as "surface_temperature", at least in models, I would modify the
proposed definition along the following lines:
Definition: The land surface skin temperature is the temperature of a
land point or the land portion of a region as inferred from infrared
radiation emitted directly from the surface to space, without being
absorbed by the atmosphere. Not all of the emitted surface radiation
originates at the soil. Some comes from various terrestrial features
(e.g., vegetation, rivers, lakes, ice, snow cover). In models the
radiating temperature of the surface is usually the
"surface_temperature", which then can be taken to be equivalent to
land_surface_skin_temperature or ocean_surface_skin temperature,
depending on the underlying medium.
I would also add this last sentence to the definition of
"sea_surface_skin_temperature".
Best regards,
Karl
On 7/16/13 10:00 AM, Evan Manning wrote:
> 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
> <mailto: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 <mailto:jim.biard at noaa.gov>
> 828-271-4900 <tel:828-271-4900>
>
>
>
> Follow us onFacebook <https://www.facebook.com/cicsnc>!
>
> On Jul 16, 2013, at 11:59 AM, Evan Manning
> <Evan.M.Manning at jpl.nasa.gov <mailto: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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Received on Wed Jul 17 2013 - 18:22:39 BST
