lee waves

of Lee Waves (schematic drawing)
1 = Mountain
2 = Wind
3 = Rotor
4 = Lee Wave
5 = typical cloud (lenticularis)
6 = typical cloud (cumulus)] Lee waves, in meteorology, are waves in a stream of air when the wind moves over mountains. They always occur in groups on the lee side of mountains. Usually a horizontal turbulence is generated at the lee side of the first moutain (following the air stream), the so called rotor. Both, lee waves themselves as well as the rotor may be indicated by typical clouds which do not move with the wind as clouds usually do. At the vertex of the wave usually exists a cloud in shape of a lens (lenticularis). The rotor may generate a cumulus cloud in its raising part. Lee waves provide a possibility for gliders to gain altitude when soaring.

See also