"Paul Hyett" wrote in message
...
In uk.sci.weather on Sat, 28 Apr 2007, Bernard Burton
wrote :

Clouds absorb and re-radiate downwards the upwelling long-wave radiation
from the surface. When cloud cover replaces clear sky the surface
radiation
continues, but can no longer escape to space. The air temperature near
the
surface rises towards the ground temperature

Do you mean the *cloud* temperature here, as the temperature at ground
level is invariably lower than at 4ft on clear nights?

until a new balance is
achieved.
--
Paul Hyett, Cheltenham (change 'invalid83261' to 'blueyonder' to email me)

No, I mean the ground temperature. The ground surface temperature reacts
quickest to the cloud cover, as there is usually a flux of heat from deeper
in the ground towards the surface. The ground surface temperature under
clear skies will fall rapidly until the heat loss by radiation is balanced
by the heat flux from lower in the ground (ignoring latent heat). The whole
ground temperature structure and air temperature structure will eventually
reach equilibrium in which the sum of all the heat losses is balanced by the
gains, provided that the external conditions (eg cloud cover, wind speed,
incoming radiation (from sun)), remain constant.

--
Bernard Burton
Wokingham, Berkshire, UK.

Satellite images at:
www.woksat.info/wwp.html
or
www.btinternet.com/~wokingham.weather/wwp.html