Definition
The layer of Earth's atmosphere located above the stratosphere and below the thermosphere, extending roughly from 30 to 50 miles (about 50 to 85 km) above the surface, in which temperature decreases with increasing altitude.
Plain English
A high layer of the atmosphere that sits well above where airplanes fly. As you go higher within this layer, the air gets colder.
Context Anchor
Seen in aviation weather and atmosphere discussions, especially when the handbook explains the layers above the part of the atmosphere where most flying and weather occur.
Derivation
From the Greek 'mesos' meaning 'middle' and 'sphaira' meaning 'sphere' or 'ball.' It is literally the 'middle layer' of the atmosphere, sitting between the lower layers (where weather and most flight occurs) and the very high layers near space.
Why Pilots Care
Pilots do not normally operate in the mesophere, but knowing where it fits helps keep the atmosphere’s layers straight when studying aviation weather and aircraft operating environments.
Grounding Statement
The mesosphere is far above normal flight; it is the layer where most meteors burn up as they fall toward Earth.
Intuition Check
Do not confuse the mesophere with the layer where most weather happens. Routine clouds, winds, and storms are much lower in the atmosphere.
Example Sentence 1
The textbook explained that the mesosphere lies above the stratosphere and is too high for conventional aircraft to operate in.
Example Sentence 2
Temperature trends in the mesophere help explain why certain upper-level wind patterns form.