A closed, vertical circulation that develops in the lee of high mountain barriers, or in the valley between two mountain ranges, when conditions are appropriate. A form of lee eddy. At the surface the wind is in the opposite direction to the gradient wind. Rotors are often the site of extreme turbulence and the top of the circulation may be marked by a rotor cloud (such as altocumulus lenticularis.)
Subjects: Meteorology and Climatology.