This category is about wave soaring.
Leewaves (mountain waves) are atmospheric internal gravity waves and were discovered 1933 by German glider pilots above the Riesengebirge. Wind driven air parcels hitting a mountainlike obstacle are being deflected upwards and will, in a stably stratified atmosphere, return to their initial height setting up an oscillatory up-down motion. Such a wave system, which often exhibits typical phenomena as interference and wave breaking, is frequently made visible by stationary, lense shaped clouds, socalled lenicularis (text by mountainwave project).