Why is it colder at high altitudes?

Answer 1

Consider the way a refrigerator works: a gas (refrigerant) is compressed and it gets hot, this passes through the hot coils at the back of the fridge to cool down. The cool compressed gas is then allowed to expand suddenly through a nozzle in the freezer, and the gas gets very cold, which makes the freezer cold. The gas then returns to the compressor for re-compression and completes the cycle.

Assume you had an insulated floppy balloon of air (as in a gondola balloon) at sea level at 20 degrees centigrade, at the same pressure as the surrounding air. You then carry the big floppy balloon to the top of Everest. The air pressure in the atmosphere decreases the higher you go up because less air is pushing down on you the higher you go up. Because the air pressure is lower, and the air in the balloon expands (it was a very floppy gondola balloon, and can expand freely). As we saw with the refrigerator, when a gas expands, it gets cold! Hence the air in the balloon will be much colder than at sea level, as is all the air around it.

See also: http:/en.wikipedia.org/wiki/High_altitude

Answer 2

I think it maybe because at a high altitude your exposed to higher radiation, because (if in a plane) you are above the clouds. Clouds help block some radiation from passing down to earth, by absorbing the radiation into the water molecules. (I think that's it any way :S)

Answer 3

There is a direct correlation in as much that the atmosphere absorbs some radiation but it's not as straight forward as that. Firstly the term radiation is not specific and can refer to any wavelength across the electromagnetic spectrum and can also refer to ionising particle radiation. Secondly there are other factors at play that effect the amount of radiation of differing sorts penetrating the atmosphere. Solar winds particularly during a period of sunspot activity tend too shield the earth from cosmic radiation. Those same solar winds carry ionising radiation which is usually deflected by the earth's magnetosphere, but will still penetrate the atmosphere to some degree especially when particularly active. Then there is the ozone layer and ionosphere to trap radiation as well. With out going into too much detail just remember the further you go from the earth's surface the less of a barrier there is and if it was not for those barriers you wouldn't be here to ask the question.

Answer 4

Pressure does not increase with altitude. It is the opposite; pressure decreases with altitude. The reason for this is that there is less atmosphere to exert pressure as you increase in altitude.

Answer 5

It does not. For the lower atmosphere as you go up in altitude the air gets cooler.

Answer 6

Radiation is more intense at high altitudes and near the Earth's poles because there is less atmospheric absorption. This results in less shielding, and therefore a more intense radiation.

Answer 7

At higher altitudes there is less atmosphere to absorb certain radiations, especially UV rays.