Description

Turbulence is caused by the relative movement of disturbed air through which an aircraft is flying. Its origin may be thermal or mechanical and it may occur either within or clear of cloud. The absolute severity of turbulence depends directly upon the rate at which the speed or the direction of airflow (or both) is changing, although perception of the severity of turbulence which has been encountered will be affected by the mass of the aircraft involved.

Significant mechanical turbulence will often result from the passage of strong winds over irregular terrain or obstacles. Less severe low level turbulence can also be the result of convection occasioned by surface heating.