Definition
The boundary in the Earth's atmosphere that separates the stratosphere below from the mesosphere above, located at approximately 50 kilometers (about 31 miles) above the Earth's surface. At the stratopause, the temperature stops rising with altitude and begins to fall again as altitude increases into the mesosphere.
Plain English
An invisible boundary high above the Earth that marks the top of the stratosphere. Below it, the air gets warmer as you go up. Above it, the air gets colder again as you go up.
Context Anchor
Seen in upper-atmosphere, weather, and standard-atmosphere discussions, especially when describing the layers above the altitudes used by normal aircraft.
Derivation
From 'strato-' (the stratosphere layer, from Latin 'stratum' meaning 'a layer') and '-pause' (from Greek 'pausis' meaning 'a stopping' or 'cessation'). Together it means 'the place where the stratosphere stops.' The same '-pause' ending appears in tropopause (top of the troposphere) and mesopause (top of the mesosphere).
Why Pilots Care
Pilots rarely fly anywhere near the stratopause, but knowing the layered structure of the atmosphere helps in understanding why temperature, pressure, and weather behave differently at different altitudes.
Grounding Statement
Picture the atmosphere as stacked layers, each separated by a boundary where temperature behavior changes direction. The stratopause is one of those ceiling lines, sitting about 31 miles up.
Intuition Check
The stratopause is not a pause in flying or weather activity. It is a named boundary between two layers of the atmosphere.
Example Sentence 1
The stratopause sits at roughly 50 kilometers altitude, well above the cruising height of any airliner.
Example Sentence 2
Specialized high-altitude missions track conditions approaching the stratopause to study atmospheric transitions.