Where is clear air turbulence commonly found?

Clear air turbulence (CAT) is frequently encountered in the vicinity of jet streams, particularly in an upper trough on the polar side of these fast-flowing air currents. The dynamics at play include the interaction between different air masses and the shear forces created as warm air rises and cold air descends in the atmosphere. This type of turbulence can occur in clear air, away from any visible weather phenomena, making it challenging for pilots to anticipate.

In this context, the polar side of the jet stream is characterized by rapidly changing wind speeds and directions. The upper trough creates a region where these changes can lead to sudden and intense turbulence, which is why flight crews advise caution when flying in those areas.

Clear air turbulence is less likely to be associated with urban areas, mountain ranges, or directly above cumulus clouds, where turbulence is primarily caused by other atmospheric conditions like thermal activity or orographic effects. Thus, the presence of CAT is most closely linked to the dynamics of jet streams, particularly on the polar side of upper troughs.