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Name: Tyra
Status: student
Grade: 4-5
Location: GA
Country: N/A
Date: 10/31/2005


Question:
Why is it so hot in the daytime in deserts and so cold at night?


Replies:
The sky above a desert is usually very clear. So during the day the ground absorbs most of the sunlight that strikes it -- heating the surrounding air. At night the reverse happens. The hot ground (and air) radiate the heat absorbed during the day back into space causing the temperature to drop rather rapidly. So it is all about converting visible radiation into heat (infrared radiation) and re-radiating that back into space.

Vince Calder


Dear Tyra-

The main reason there are such big temperature differences between day and night in the desert is there is very little moisture in the air in the deserts. We measure the moisture in the air with a number called "relative humidity."

Moisture in the air "holds" the heat, much like a blanket over you holds your body heat when you sleep. So, places like islands in the tropics, or in jungles, where there is lots of moisture in the air, have small differences between daytime and nighttime temperatures. These differences in weather conditions, like desert weather and jungle weather are called "climate." The jungle climate is much different from a desert climate.

Wendell D. Bechtold, Meteorologist
Forecaster, National Weather Service
Weather Forecast Office, St. Louis, MO


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