If heat rises, why is it always so cold in the mountains?

Question

Hot air rises, while the cooler air sinks to ground level. Then the cool air heats up and rises when it reaches the equator; and the hot air reaches the poles and cools, then also sinks. Why is it then that the the higher up in the atmosphere you are the colder it is? If the hot air currents are higher up, shouldn't it be the other way around?

Colder air is denser, therefore the hot air should rise above. The upper layers of the atmosphere are thinner (less dense.) So how does it make sense that the ground is warmer than the upper layers of the troposphere?

Answer 1

While you are correct in stating that "heat rises" this does not explain differences in temperature due to altitude.

One of the the simplest ways to understand this is to look at the opposite situation -- namely what is the typical temperature of some place at low altitude? And the answer would be "warmer". What are some of the things that are different at high & low altitude? Well "air pressure" is a big one. In fact that is how aircraft typically measure altitude.

What gives air its "pressure"? Well, as anyone who has inflated a balloon or tire knows, packing more air into something gives it more pressure. But what is doing the the "packing" out in the atmosphere? To answer this you have to think about pressure in the ocean or under any deep water. The weight of the "stuff" above makes the pressure.

So at low altitude there is an "ocean of air" above that packs in the air. And at hight altitude there is less densely packed air..

BUT how does THAT explain temperature??

Well again you have to think on the microscopic level. At the microscopic definition the meaning of "temperature" is a measure of the SPEED that particles are moving at. The "speed" of particles at low temperature is slow moving, and hot is high. When particles of air are tightly packed they bump into each other a lot and this bumping keeps them hot. When particles are not tightly packed they don't get bumped much and are slow and cool.

Finally there is "heat". Anything that is more dense tholds more heat than a less dense thing. Doesn't matter whether you are talking about air or anything else (though generally only gases have enough variability of densisty to matter, though that is a whole 'nother topic) more of it will hold more heat than less of it.

Answer 2

Good question! It stumped me and I had to google it.

As the hot air rises the pressure decreases. In a gas there is a formula that relates temperature and pressure:

PV=nRT

As you can see, pressure and temperature are directly proportional. If you half the pressure, you half the temperature. So as the hot air rises, it expands and its pressure drops. This causes the air to cool.

I'm not sure I find this explanation entirely satisfying. Does anyone have a better one?

********Update:

@Ray B

You are confusing heat capacity with temperature. You can have a thin gas at as high a temperature that you like. It even gets easier, not harder, to increase the temperature as the gas gets thinner.

Answer 3

The world is heated by light energy reflecting of the ground and converting to heat energy. This energy is conducted through the atmosphere and warms the air. As you get farther from the ground, you get farther from the reflected heat and it gets colder.

Simultaneously, as you go higher the air gets thinner, and thin air has a low heat capacity. therefore the air cannot absorb/hold much heat, there-by causing it go get colder.

Answer 4

Heat rises when its in a an area of equal pressure (a room for example). Temperature and pressure are directly protportional. As the altitude increases, the atmospheric pressure decreases so the temperature does also.

Answer 5

okay, have you ever heard that it's like, 3000 something degrees up in the outermost layer of the atmosphere, yet you'll freeze to death? temperature is based on how fast the molecules are moving, yet if the gas particles/molecules are too far apart to touch eachother, like up high where the air is super thin, then it'll still feel cold, even if the molecules are moving as fast as 500 degrees.

of course, i'm a naive middle schooler. so feel free to just tell me to shut up. [actually, dont; i'll probably get pissed off with my excessivity of hormones and puberty-triggered mood swings and all]

Answer 6

b/c it rising from the ground and the ground is still considered ground even if its a mountain

Answer 7

Ice demons live up there.

Answer 8

HAHAHA