Wind flow caused, affected, or influenced by mountains. Orographic effects include both dynamic, in which mountains disturb or distort an existing approach flow, and thermodynamic, in which heating or cooling of mountain-slope surfaces generates flow. Dynamic effects include aerodynamic obstacle effects, mountain waves, channeling, orographic blocking, and processes leading to foehn, bora, and gap winds. Thermodynamic effects include anabatic winds, katabatic winds, valley breezes, and mountain breezes. See also mountain–valley wind systems, mountain–plains wind systems.