What causes clear air turbulence?

• A. The Jet Stream
• B. Thunderstorms
• C. Convective currents from the surface
• D. Frontal boundaries

Answer: (A)

Clear air turbulence occurs where there is strong wind shear in the upper atmosphere, and the jet stream is the most common source of that shear. The jet stream is a fast-moving ribbon of air high in the atmosphere. As you fly near or through its core, wind speeds and directions can change abruptly over short distances. Those rapid changes in airspeed and direction create turbulent eddies that shake an aircraft even when there are no clouds or storms in the area.

Thunderstorms and convective currents from the surface involve visible weather and convective activity, which typically produce turbulence associated with clouds and precipitation. Frontal boundaries also bring turbulence tied to shifting air masses and weather fronts, often with visible weather as well. But the hallmark of clear air turbulence is the wind shear in the upper atmosphere near the jet stream, which is why this option is the best answer.