Atmoshphere

The troposphere is the part of the atmosphere up to an altitude of 4 to 8 miles. Here rising air e.g. being pushed up a mountain rarifies i.e. its pressure decreases, so by by Boyle's Law (which states that, the pressure of a fixed volume of gas is proportional to its temperature [and vice versa]) the temperature drops (the molecular particle explanation of this effect is that as molecules are further apart at low pressure, they vibrate slower i.e. their average kinetic energy (which temperature is proportional to) is lower.

The temperature of the stratosphere (7 miles to 30 miles altitude) is actually nearly constant with altitude (only rises slightly), and could be due to a slightly greater effect of the solar radiation, which is reflected less and absorbed more by the increased proportion of whiteness of visible light (wavelengths 400-700 nm) compared to the ultraviolet and infrared radiation by the gases in the ozone layer (greenhouse effect).

A complication occurs when temperature inversion occurs i.e. when cold air undercuts warm air so that air is warmer at a higher altitude even in the troposphere (google the words in bold for the causes of this).

I hope this helps, although we need assistance for more detail: calllllllliiiiiiiinnnng - geography nerds!!

M.