ATLANTA – We’ve hit another cold snap in metro-Atlanta, and early risers are shivering the most just after sunrise.
It makes sense that the sun would warm you, and yet the temperature continues as the sun rays begin to hit us.
During the day, the sun bakes the earth, but the ground can’t hold onto all of that warmth. It’s emitting radiation all the time.
Here’s where it gets interesting. When the sun drops so its rays are hitting us at a certain angle, the earth starts losing more heat than it absorbs. On a typical winter day that begins around 3 o’clock in the afternoon.
Once the sun sets, the ground rapidly loses its heat.
“Until sunrise, the surface continues to lose more energy than it receives, thus continues to cool,” says Dr. David Stooksbury, Graduate Coordinator at the Atmospheric Sciences Program at the University of Georgia.
When the sun appears again logic tells you the temperature will begin to climb.
But it takes time.
Again, it’s the angle of the sun.
At dawn, the rays are too weak to overcome the amount of radiation leaving the ground. The temperature continues to dip until the sun is at just the right spot.
Once the sun is in the right position to counteract the earth’s loss of warmth, then the temperature can start to climb.
There are variables. Clouds can trap heat.
“The less clouds and water vapor in the air, the more radiation is lost to space which enhances cooling,” says Dr. Greg Huey of Georgia Tech’s Earth and Atmospheric Sciences Department.
Cold fronts can move in during the day. But generally, don’t expect the arrival of the sun to warm you right away.
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