What is the name of the boundary between Earth’s troposphere and stratosphere?

The boundary between Earth’s troposphere and stratosphere is called the tropopause.

The tropopause is not a perfectly flat surface. It is generally higher over the tropics, where it can reach about 16 to 18 kilometres, and lower near the poles, where it may be only about 8 kilometres above sea level. Its altitude also changes with season and weather systems.

In the troposphere, temperature generally decreases as altitude increases. In the stratosphere, temperature tends to increase with height because ozone absorbs ultraviolet radiation. The tropopause marks the transition between these different temperature patterns, although meteorologists define it using a specific lapse-rate criterion rather than simply a visible boundary.

Most clouds and weather occur in the troposphere, but powerful thunderstorms can briefly overshoot the tropopause. The tropopause should not be confused with the stratopause, which separates the stratosphere from the mesosphere.