Which of the following is associated with clear air turbulence?

Clear air turbulence is primarily associated with the interference caused by jet streams. Jet streams are fast-flowing air currents found in the atmosphere at high altitudes, often near the boundaries between different air masses. When aircraft fly through these regions, particularly where the jet stream flows through stable air, they can experience sudden changes in wind speed and direction, leading to turbulent conditions.

This type of turbulence occurs without visual clues such as storm clouds, making it particularly challenging for pilots, as they may not be able to predict its onset based solely on weather radar or visual observations. The presence of storm clouds, stable atmospheric conditions, and high humidity levels are not typically relevant to clear air turbulence, which specifically involves the interaction of airflows, especially in and around jet streams.