Question

What happens to air temperature as altitude increases? And why?

Answer 1

It drops up to a certain point.

Explanation:

The atmosphere has a fixed top. So as you climb in altitude the amount of atmosphere above you decreases. Since there is less atmosphere the weight of that mass of atmosphere is also less. The weight of the atmosphere is atmospheric pressure.

Gay-lussac's law states that pressure and temperature are proportional, so when one drops so does the other.