Dear Philip,
My take is that the land_surface_skin_temperature and the
surface_temperature are likely very close in value, since the
surface_temperature is an infinitesimally thin layer at the bottom level
of the atmosphere which interfaces with the land skin (soil) below -
hence, the definition stating that they can be taken to be equivalent.
The land_surface_skin_temperature proposal is motivated by a new
observational data product which is the radiating temperature of a very
thin, top layer of the land surface. This quantity does not currently
exist in the CF standard name set, but has an analogue in
sea_surface_skin_temperature. The surface_temperature name was added to
CF because it is a standard model variable, I believe. Someone please
correct me if I am wrong, but the radiating temperature of the Earth in
models is often simply referrred to as the "surface temperature," so I
wanted to draw a connection between the model quantity and the
observable land_surface_skin_temperature in the definition such that
they are effectively the same thing. This seems to be one of those
situations where there are two quantities, one created for an observed
quantity and the other for a model quantity, but the two quantities
likely have very similar values. I guess the question is whether or not
this is permissible within CF.
Sincerely,
Jonathan Wrotny
On 10/3/2013 1:30 PM, Cameron-smith, Philip wrote:
Hi Jonathan (Wrotny), Jonathan (Gregory), et al.,
I am a little surprised.
It is explicitly stated in the proposed description that land_surface_skin_temperature
"can be taken to be equivalent to" surface_temperature over land areas.
In the description for surface_temperature, it indicates that it can apply to
just land using cell_methods. Indeed, in the CF convention, example 7.6
explicitly states this:
Example 7.6. Mean surface temperature over land and sensible heat flux
averaged separately over land and sea.
float surface_temperature(lat,lon);
surface_temperature:cell_methods="area: mean where land";
I also note that surface_temperature is already an alias for
surface_temperature_where_land (which I think is deprecated)
Why is a new std_name needed? What am I missing?
It is true that there is a variable called sea_surface_skin_temperature, but it
appears that this was introduced for different reasons. Specifically, it
looks like sea_surface_temperature was created to refer to the water _near_ the
surface to distinguish it from the 'skin'. sea_surface_skin_temperature then
differs from surface_temperature because it refers to the interface under
sea-ice rather than above sea-ice.
Best wishes, as always :-),
Philip
-----------------------------------------------------------------------
Dr Philip Cameron-Smith, [email protected], Lawrence Livermore National Lab.
-----------------------------------------------------------------------
-----Original Message-----
From: CF-metadata [mailto:[email protected]] On Behalf
Of Jonathan Gregory
Sent: Thursday, October 03, 2013 9:35 AM
To: [email protected]
Subject: Re: [CF-metadata] Surface temperatures
Dear Jonathan
The new proposal looks fine to me. Thanks. I see that you don't have to
define the thickness of the layer; instead, you are defining it implicitly
through the method of diagnosis. Others may have views, of course.
Cheers
Jonathan
----- Forwarded message from Jonathan Wrotny <[email protected]> -----
Date: Wed, 2 Oct 2013 11:26:27 -0400
From: Jonathan Wrotny <[email protected]>
User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:17.0) Gecko/20130801
Thunderbird/17.0.8
To: Jonathan Gregory <[email protected]>, "cf-
[email protected]"
<[email protected]>
Subject: Re: [CF-metadata] Surface temperatures
Dear Jonathan Gregory,
I am getting back to this reply after a long time - sorry, I was
pulled in a few different directions lately. Hopefully, it is
possible to bring back to life a submission that I had made for the
land_surface_skin_temperature.
Revisiting my previous proposal and a few e-mails by Karl Taylor and
Evan Manning, I have made some modifications to the definition of this
standard name so that I can incorporate some suggestions by Karl and
Evan. Here is my current proposal:
Standard Name:land_surface_skin_temperature
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 towards space through the atmosphere. Not
all of the emitted surface radiation originates at the soil.Some may
come from various terrestrial features (e.g., vegetation, rivers,
lakes, ice, snow cover, man-made objects).Thus, the land surface skin
temperature is the aggregate temperature of an effective layer which
includes the soil and terrestrial features at the surface (if they
occur).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 sea_surface_skin temperature,
depending on the underlying medium.
Canonical Units:K
Thanks for still considering this proposal. Sincerely,
Jonathan Wrotny
On 8/1/2013 12:56 PM, Jonathan Gregory wrote:
Dear all
I agree with Karl than in CF standard names "land" means "non-sea",
whereas sea-ice is part of sea. Hence I would support adding
land_surface_skin_ temperature, for use by applications which classify
locations as land or sea.
However I also agree with Evan that one can approach this more
generally, and therefore I would also support the addition of
surface_skin_temperature, with which an area-type could be specified,
if anyone wants to follow that approach (we only add names when they
are needed).
The quotations that Evan made show that we need to change the
definitions where they mention "skin". This is because in these new
names "skin" is being given a more precise and practical meaning,
motivated by observational methods, whereas the surface_temperature
names were introduced for models, in which the skin can be a notional
and infinitesimally thin layer.
Best wishes
Jonathan
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