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Thread: Why is the temperature lower up in the mountains?

  1. #1 Why is the temperature lower up in the mountains? 
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    During a skiing trip we had a rather fruitless discussion about why temperature is lower up in the mountains. Maybe anyone here can give me a proper answer.

    I always thought that the surface of the earth was absorbing sunlight resulting in a raise in temperature. But surely mountains are even better exposed to the sun than the rest!?


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  3. #2  
    Universal Mind John Galt's Avatar
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    The air is thinner and less able to retain heat.

    Air is heated for the most part indirectly from the land. i.e. most of the sun radiation reaches the ground and heats the air above it. At sea level you are warmed by air moving from an adjacent 'block' that has been heated by air immediately above ground. In the mountains the air is likely to have come from several hundred or thousand metres above the ground that is warming it.


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  4. #3  
    Forum Cosmic Wizard SkinWalker's Avatar
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    Environmental lapse rate. That's the reason for declining temperatures with altitude. It isn't constant, because there are always changing variables, but the general rule of thumb is a decrease of 6.5 degrees Celsius per kilometer (3.6 deg F / 1000 ft).

    Temperature in the air is related to pressure. As altitude increases, pressure also decreases. Rising air masses expand and cool adiabatically (think about the release of compressed air from a spray can and how the can cools).

    The ski slopes you were on, however, were probably warmer than they would have been if you applied the environmental lapse rate alone. This is because you are right: the mountains do absorb some heat from the Sun's rays. Thus, the temperature in mountainous regions is often warmer than the same altitude over non-mountainous regions.

    The lapse rate stops, though, at about 8-10 km where temperature levels off and then starts to increase through the stratosphere. This is because of the ozone molecules that are absorbing energy from the Sun. At the mesosphere, the temperature again declines to around -90 deg F until you reach the thermosphere, where it steadily increases again. The temperature at the high end of the thermosphere (this is where aurora borealis forms) can reach as high as 120 deg F or more. But you would never feel it if you were unexposed because there are so few atoms of atmosphere to come into contact with.

    Hope that helped
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  5. #4  
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    Thanks a lot for your explanations! I have already passed them on...:-)
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