Theory of mountain waves of large amplitude

Rotors are defined as regions containing flow in the opposite direction to the main stream and are shown to exist when the wave amplitude is large enough. Equations are derived for computing rotor flow in an infinitely deep atmosphere. The problem of choosing an appropriate second boundary condition in steady flow over a ridge is complicated when the amplitude is finite because the shape of obstacle obtained depends on the airstream characteristics as well as upon the mathematical form given to it. Probably under some actual conditions the oncoming airstream is modified by the presence of the mountain. Because of the great variety of airstreams and mountains no general case can be illustrated. The particular cases chosen illustrate rotor flow. These particular cases do, however, each represent a set of cases in which all the non‐dimensional numbers involved have the same value. Known cases of rotors in the Sierra Nevada and at Cross Fell are cited to illustrate the theory.