Where is clear air turbulence most likely to be encountered?

• A. The Jet Stream
• B. In low-level valleys
• C. Near coastlines
• D. In strong surface winds

Answer: (A)

Clear air turbulence happens where there is strong wind shear in the upper atmosphere, often in and around the jet stream. The jet stream is a fast-moving, narrow band of air high in the sky where winds can change quickly with both speed and direction. That rapid variation creates turbulent air pockets even when there are no visible clouds, making it a common source of clear air turbulence for high-flying aircraft.

Low-level valleys cause mechanical turbulence from terrain touching the flow, but that’s near the surface and not the clear-air, high-altitude type. Near coastlines or in strong surface winds can produce turbulence too, but they’re typically due to surface-to-lower-atmosphere effects or convective activity, not the clear-air variety that pilots worry about in the upper atmosphere.