A type of cold-air downslope flow at the bottom of the boundary layer where the two dominant processes are advection and buoyancy. Once fully developed, this idealized flow is constant in time as long as cold air is supplied or produced. Wind speed increases with the square root of downslope distance, and flow depth increases linearly with distance. Typical depths are 2–10 m. See katabatic wind, slope flow, gravity flow, drainage wind.