Tropopause

Rising from the planetary surface of the Earth, the tropopause is the atmospheric level where the air ceases to become cool with increased altitude and becomes dry, devoid of water vapor.

[3][4] In the absence of inversions and not considering moisture, the temperature lapse rate for this layer is 6.5 °C per kilometer, on average, according to the U.S. Standard Atmosphere.

Since the tropopause responds to the average temperature of the entire layer that lies underneath it, it is at its maximum levels over the Equator, and reaches minimum heights over the poles.

[14] Researchers at Harvard have suggested that the effects of Global Warming on air circulation patterns will weaken the tropical tropopause layer cold trap.

Thus, in some sense, the tropical tropopause layer cold trap is what prevents Earth from losing its water to space.

Vigorous thunderstorms, for example, particularly those of tropical origin, will overshoot into the lower stratosphere and undergo a brief (hour-order or less) low-frequency vertical oscillation.

[citation needed] Most commercial aircraft are flown in the lower stratosphere, just above the tropopause, during the cruise phase of their flights; in this region, the clouds and significant weather perturbations characteristic of the troposphere are usually absent.