But if the skin layer's absorptivity is greater at angles where the OLR intensity is less, then
the equilibrium skin temperature will be colder.
Not exact matches
Because the two
temperatures (
skin and air) seek
equilibrium, the higher difference between air and
skin make women feel colder.
Radiative
equilibrium at small LW optical thickness occurs when the whole atmosphere has a
temperature such that the Planck function is about half of that of the surface (a
skin temperature), whereas at larger LW optical thicknesses, the
equilibrium profile has a signficant drop in the Planck function through the atmosphere, approaching half the OLR value at TOA and approaching the surface value towards the surface — of course, convection near the surface will bring a closer match between surface and surface - air
temperatures.
(PS a
skin temperature can be lower than the brightness
temperature of the OLR because a very thin layer at the top of the atmosphere will absorb a tiny fraction of OLR, thus barely affecting OLR, but must in
equilibrium emit that same amount of energy both upwards and downwards; if it were as warm as the brightness
temperature of the OLR then it would emit twice what it absorbs and thus cool.
The
skin layer planet is optically very thin, so it doesn't affect the OLR significantly, but (absent direct solar heating) the little bit of the radiant flux (approximatly equal to the OLR) from below that it absorbs must be (at
equilibrium) balanced by emission, which will be both downward and upward, so the flux emitted in either direction is only half of what was absorbed from below; via Kirchhoff's Law, the
temperature must be smaller than the brightness
temperature of the OLR (for a grey gas, Tskin ^ 4 ~ = (Te ^ 4) / 2, where Te is the effective radiating
temperature for the planet, equal to the brightness
temperature of the OLR — *** HOWEVER, see below ***).
In the absence of solar heating, there is an
equilibrium «
skin temperature» that would be approached in the uppermost atmosphere (above the effective emitting altitude) which is only dependent on the outgoing longwave (LW) radiation to space in the case where optical properties in the LW part of the spectrum are invariant over wavelength (this
skin temperature will be colder than the
temperature at the effective emitting altitude).
However, the
skin layer, absent solar heating, has an
equilibrium temperature that is smaller than the brightness
temperature of the radiation from below at those wavelengths where the
skin layer absorbs.
Starting with zero atmospheric LW absorption, adding any small amount cools the whole atmopshere towards a
skin temperature and warms the surface — tending to produce a troposphere (the forcing at any level will be positive, and thus will be positive at the tropopause; it will increase downward toward the surface if the atmosphere were not already as cold as the
skin temperature, thus resulting in atmospheric cooling toward the
skin temperature; cooling within the troposphere will be balanced by convective heating from the surface at
equilibrium, with that surface + troposphere layer responding to tropopause - level forcing.)
re inline comment on 24, What I noted was that the ocean
skin equilibrium referenced in RC 5 Sept 06 could be influenced by variations in ocean currents and the cryosphere to affect atmospheric
temperature on the scale of decades.
Aaron Lewis @ 24 — «What I noted was that the ocean
skin equilibrium referenced in RC 5 Sept 06 could be influenced by variations in ocean currents and the cryosphere to affect atmospheric
temperature on the scale of decades»
So the existing pressure regime permits changes in the rate of energy flow independently of
temperature such that the warmer
skin does not change the
equilibrium temperature of the ocean bulk.
More DLR therefore fails to achieve a net slowdown in energy throughput and the
equilibrium temperature of the subskin and bulk ocean fails to rise despite the rise in
temperature of the ocean
skin.