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Name: Mark M.
Status: student
Age: 20s
Location: N/A
Country: N/A
Date: 2001


Question:
Why does it get colder in the morning once the sun starts to rise?


Replies:
Mark -

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.

Larry Krengel


Mark,

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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