The tropopause is the higher limit of the Troposphère and the lower limit of the Stratosphère. It constitutes also the limit of the Biosphère and is the coldest part of the lower atmosphere.

Its altitude varies according to the seasons and the latitudes, going from 8 with the pole S and 18 Kilomètres with the equator with an average altitude of 11 km. The tropopause is higher during the be than the Hiver.

The Température of the atmosphere decreases with altitude starting from the ground until the tropopause, then increases thereafter because of the absorption of the rays Ultraviolet by the Ozone present in stratosphere.