Coldest Time of Day
Why is the coldest time of day right after the sunrises???
I would expect the sun to heat the earth and the coldest time of day be
before visible light hits the surface and the sky is still dark.
The earth continuously radiates heat into space and receives heat from space.
The change in temperature is controlled by the balance between these
as the sun begins to rise, the balance is tipped toward a loss of heat...
therefore temperature goes down.
Because the Sun is so low to the horizon at sunrise, most of the energy is
absorbed by the distant atmosphere. Meanwhile, for cloudless skies at
least, energy from the Earth's surface continues to be lost to the
atmosphere directly above. Thus, the lowest temperature of the night can
still occur after sunrise.
meteorologist working at Argonne National Laboratory
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Update: June 2012