Definition
The boundary in the Earth's atmosphere between the mesosphere below and the thermosphere above, located at roughly 50 to 53 miles (80 to 85 km) above the surface. It marks the altitude where temperature stops decreasing with height and begins to increase again, and is generally the coldest region of the atmosphere.
Plain English
An invisible line high above the Earth that separates two layers of the atmosphere. Below it, the air keeps getting colder as you go up. Above it, the air starts getting warmer again. It is the coldest spot in the atmosphere.
Context Anchor
Seen in aviation weather and atmosphere-layer discussions, especially when describing the structure of the upper atmosphere.
Derivation
From the Greek 'mesos' meaning 'middle', plus 'pause' from the Latin 'pausa' meaning 'a stop' or 'cessation'. So 'mesopause' literally means 'the stop of the middle layer' — the point where the middle atmospheric layer (mesosphere) ends.
Why Pilots Care
The mesopause is not a normal cockpit operating concern for most pilots, but it helps pilots understand how the atmosphere is divided and why temperature does not change the same way at every height.
Grounding Statement
Picture the atmosphere as a stack of layers; the mesopause is the lid on the middle layer, sitting about 50 miles up, where the air is colder than anywhere else above or below.
Intuition Check
“Pause” does not mean the air stops moving. Here it means a boundary where the temperature trend changes.
Example Sentence 1
Temperatures at the mesopause can drop below -130°F, making it the coldest region in Earth's atmosphere.
Example Sentence 2
Temperature profiles show a steady drop through the mesosphere until the mesopause, after which warming begins.