Name: Mark M.
Why does it get colder in the morning once the sun starts to
The temperature of a particular place on the earth is a function of the
difference between the incoming radiation (mostly from the sun) and the
outgoing radiation emitted by the earth into space. Assuming no airman moves
in to confuse the situation and a clear sky, the temperature will begin
falling in the afternoon as the balance leans toward the outgoing radiation
and continues to drop through the night. This fall will continue until the
sun is high enough to tip the balance to incoming radiation. This will not
be immediately as the sun rises. The exact time will be controlled by a
number of atmospheric factors.
All that said, your observation is frequently valid. It does often continue
to cool for a time following sunrise.
It is not unusual, especially when there
is no cloud cover, for the temperature
to continue to decrease for up to an hour
(a half hour is common) after sunrise.
The Sun is so low on the horizon that it
has very little heating effect on the
ground. So, energy can continue to escape from
the ground and the lower atmosphere, thereby
continuing to cool the air near the ground.
David R. Cook
Atmospheric Research Section
Environmental Research Division
Argonne National Laboratory
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Update: June 2012