자료: WeatherQuestions.com, http://www.weatherquestions.com/What_is_infrared_radiation.htm
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What is infrared (heat) radiation? |
| Infrared (IR) radiation is just as important to the Earth's weather and climate as sunlight is. For every bit of sunlight that the Earth receives, an equal amount (on average) of IR radiation must travel from the Earth back to outer space. Everything emits infrared radiation -- you usually don't notice it, though, because it is weak, and you can't see it like you can sunlight. The radiant heat you feel from an oven or a fire is infrared radiation. Greenhouse gasesin the atmosphere, especially water vapor, trap some of this infrared radiation, and keep the earth habitable for life. Clouds also trap some of this radiation. The reason why the air cools so quickly on a clear, dry evening is because the lack of humidity and clouds allows large amounts of IR radiation to escape rapidly to outer space. |
| Interesting facts: |
| FEELING INFRARED RADIATION FROM THE GROUND Here's an experiment you can try. On a clear dry evening after a sunny day, as the sun is setting, extend your arm out over the ground (grass, dirt, or even better a driveway or parking lot. Turn your hand over, back and forth, several times -- palm facing down, then up, then down, etc. You will be able to feel the difference in the amount of IR radiation reaching the top and bottom of your hand. The reason for this is that the sky is emitting much less radiation downward than the ground is emitting upward. |
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