Turbopause

Part of speech: noun

Definitions

1. The level in the upper atmosphere, roughly near 100 kilometres up, where turbulent mixing stops keeping the air uniformly blended
2. An atmospheric boundary at about 100 kilometres altitude marking where the air ceases to stay evenly mixed and lighter gases begin to separate
3. The height in the atmosphere, around 100 km above the surface, that divides the well-mixed lower air from the layer above it

Etymology: "Turbopause" is a technical coinage from the mid-20th century, built from "turbo-", a combining form meaning "turbulence" (from Latin "turbo," a whirlwind or spinning top), and "-pause," taken from "tropopause" and "stratopause" as the name for an atmospheric boundary layer. The pattern is deliberate: the "-pause" ending marks a level where one atmospheric layer gives way to another, and the prefix names the physical quality that defines the boundary. The term refers to the altitude, roughly 100 kilometres up, where the air becomes turbulent and mixing dominates over the gentle layering found below. Above it, gases separate by weight rather than being stirred together. Because the word is a modern scientific compound rather than an old descriptive term, its meaning rests entirely on this physical distinction, which is what the two parts of the name encode.