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Jim, Evan, CF board:
Yes, this is also the case for the future GOES-R data product that
is motivating this new standard name. It will report the land
surface temperature for all non-ocean surfaces. So, for instance,
lakes and rivers that are internal to land will have land surface
temperatures reported. The GOES-R sea surface temperature data
product, on the other hand, only reports temperatures for the
sea/ocean surface.
The purpose of my submission of "land_surface_skin_temperature" is
to add the commonly used quantity, land surface temperature
(sometimes also referred to as land surface skin temperature) to
the CF database. Just as the sea surface skin temperature is used
by the SST community for the temperature of the sea or ocean, the
land surface (skin) temperature is the quantity that refers to the
temperature of all land surfaces (which may or may not be covered
by other things - lakes, rivers, snow, vegetation, buildings,
etc.). I think this delineation motivates two standard names, the
already existing sea_surface_skin_temperature, and a new one to
cover the land surface (skin) temperature. My view is that the
science community already commonly uses these two quantities and
has for a long time, so the CF database should as well.
If this approach is taken, then I do agree with Evan that
specifically where the sea and land intersect, that some portion
of the data point will be land and some will be ocean (this
depends on the resolution of the data, of course). My guess for
this scenario is that each dataset has some unique way to
determine if the data point is "land" or "sea." However, the
GOES-R surface temperature products do not report the fraction of
land/sea for data points where land/sea intersect - they simply
report a temperature as either "sea" or "land" based on their way
of identifying the pixel as "land" or "sea."
Sincerely,
Jonathan
On 7/16/2013 12:36 PM, Jim Biard 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
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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