Clear-Air Turbulence

Clear-air turbulence is the turbulent movement of air with no visible warning signs such as clouds, occurring where air masses moving at very different speeds meet. It develops most often in the high troposphere, at roughly 7,000 to 12,000 metres, near the tropopause and within jet streams, and can also occur at lower altitudes near mountain ranges, driven by wind shear at the edges of jet streams, temperature gradients, Rossby waves, mountain waves and gravity waves at the tropopause. Because pilots often cannot see it coming, sudden encounters can put significant stress on aircraft structure; most incidents cause only passenger discomfort but some have caused serious injury, and a small number of documented cases have involved aircraft breaking apart in flight, with climate change projected to increase its intensity in the coming decades.