Why does the temperature decrease with the altitude?

Question

I have read that it is because the earth surface gets heated up and the the heated surface of the earth heats the layer of the atmosphere above it. So it is hotter than the air at high altitudes. But this does not explain why mountains are cooler. Can any one one please explain?

Answer 1

Temperatures usually decrease with height because the pressure decreases with height and you have less air molecules the higher up you go. Air temperature is basically a measure of kinetic energy caused by air molecules moving around and colliding. The more they collide, the more heat is built up. This means that where there is more air molecules (near the surface), there is also more molecule collisions with each other making the temperature warmest. As you go upward, the amount of molecules lessens, therefore the number of collisions are less and the temperature is not as warm
This can vary significantly from day to day and sometimes (especially on clear/cool nights) the temperature can even rise with height (inversion), but usually in the troposphere they tend to decrease. You can use Lapse rates to determine the decrease in temperatures with height.

The standard lapse rate is:
3.5 ° fahrenheit for every 1000 feet.
If you live somewhere that uses celsius, it would be 6.5° C for every kilometer.

So say, at sea level it's 59°F. You go up 5,000 Feet. If the temp decreases 3.5° for every 1,000 feet you go up, you would multiply 3.5° by 5 (since you went up 5,000 feet), and then subtract that number from the degrees fahrenheit at sea level to get your estimated temperature at that new altitude. The temp at 5,000 feet above sea level would be about 41.5° F if sea level temps were 59°F.

There are specific lapse rates you could use to measure temperature changes in temps with moutains altitudes too. Oragraphic lifting forces air to move upward on the windward side of a moutain. As this parcel of air is lifted, the temps would decrease as well, and you would used lapse rates to calculate the temperatures depending on the height. You would usually use the dry adiabetic rate, the dewpoint rate, and the moist adiebetic rate. This can get kind of complicated, but if you want to know how it's done, let me know (say something on additional details) and I will show you.

Answer 2

Temperature decrease doesn't actually happen all the way up into space. Once you reach the stratosphere, about 10km up depending on what part of the globe you're in, the temperature actually starts increasing with height. Don't get me wrong, it's still very cold, but it is no longer getting colder as you go up. In the mesosphere it begins to cool with height again, and then in the thermosphere is warms with height. The Ionosphere is pretty much space, so it cools greatly with height.

The re-radiated energy of earth is trapped more effeciantly by the ozone layer of the stratosphere, so the stratosphere will become warmer than you would expect for it's height.

Answer 3

Glad to, Jabir.
Measured temperature is a function of 2 things -
The number of molecules striking the thermometer and the energy level of those atoms.
Air at 110 degrees feels rather hot. Water at the same temperature is uncomfortalby hot. Obviously, there are many more molecules per liter of water than liters of air.
As you go to higher altitudes, the air thins. That is the number of molecules per liter lessens.
Even though the individual air molecules may have the same energy level, there are so few of them that the total energy level of a liter of air is much less. Thus you have a lower temperature.

Answer 4

I believe the air becomes thinner, as altitude increases, and so it doesn't retain heat as well. And the closer to the ground you are, the more layers of atmosphere are above you, contributing to retainment of heat.

Answer 5

Because your brain is smaller than a peanut...