How is clear air turbulence defined?

Clear air turbulence is specifically defined as turbulence that occurs in clear skies, away from any noticeable weather phenomena like clouds or storms. It is often associated with wind shear, which is a sudden change in wind speed or direction over a short distance in the atmosphere. This wind shear can create unstable air currents, leading to unexpected bumps during flight.

The nature of clear air turbulence means that it can occur at high altitudes and is particularly common near the jet streams, where strong wind patterns are present. This turbulence is distinct from turbulence caused by weather systems, such as low clouds or thunderstorms, which typically have visible indicators and can often be anticipated more easily by pilots. Therefore, the definition that best captures the essence of clear air turbulence is that it is turbulence devoid of clouds due to wind shear, highlighting the clear conditions in which it occurs and the mechanism behind it.