What defines friction turbulence in aviation?

Friction turbulence in aviation is primarily defined by the interaction between the wind and the Earth's surface, which is influenced by surface roughness. As wind flows over various terrains—such as buildings, trees, or uneven ground—the irregularities create disturbances in the air flow, leading to turbulence. This turbulence is generally more pronounced at lower altitudes where these surface features have a significant impact on the flow of air.

In essence, the rougher the surface, the more the air is disturbed, generating turbulence. This type of turbulence is particularly relevant for pilots during takeoff and landing phases of flight, as they are operating at lower altitudes where friction with the surface is a major factor affecting flight stability and control. Understanding this phenomenon helps in anticipating handling characteristics when flying in proximity to the ground.