A vocabulary of landscape — a landscape of words
1469 entries
inversion
An inversion is a layer of atmosphere where temperature rises with height instead of falling, which is backwards to the normal state and which shuts down vertical mixing. Cold air sits under warm air and stays there. Inversions trap fog, smoke, and haze at the surface, produce the sharp-edged cloud sea that fills a valley below a summit, and are why a mountaintop in winter can be warmer than the town below it.
Etymology
The word is Latin for a turning upside down, and it is the same word used for inverted word order in grammar and an inverted chord in music. Meteorologists borrowed it in the nineteenth century for exactly the sense it already had: the ordinary arrangement stood on its head.
Notes
Cold air is dense and runs downhill, so on a clear still night it drains into hollows and pools there. Sound behaves oddly under an inversion too, bending back down toward the ground, so noises carry unusually far on a still cold morning.