Clear-air turbulence

For other uses, see Clear air turbulence (disambiguation).

In meteorology, clear-air turbulence (CAT) is the turbulent movement of air masses in the absence of any visual clues such as clouds, and is caused when bodies of air moving at widely different speeds meet.

The atmospheric region most susceptible to CAT is the high troposphere at altitudes of around 7,000–12,000 m (23,000–39,000 ft) as it meets the tropopause. Here CAT is most frequently encountered in the regions of jet streams. At lower altitudes it may also occur near mountain ranges. Thin cirrus clouds can also indicate high probability of CAT.

CAT can be hazardous to the comfort, and occasionally the safety, of air travelers,[1] as the aircraft pilots often cannot see and anticipate such turbulences, and a sudden encounter can impart significant stress to the airframe.

CAT in the jet stream is expected to become stronger and more frequent because of climate change,[2] with transatlantic wintertime CAT increasing by 60% (light), 95% (moderate), and 150% (severe) by the time of CO2 doubling.[3]

  1. ^ Wragg, David W. (1973). A Dictionary of Aviation (first ed.). Osprey. p. 93. ISBN 9780850451634.
  2. ^ Williams, P. D. and Joshi, M. M. (2013). "Intensification of winter transatlantic aviation turbulence in response to climate change", Nature Climate Change, 3(7), pp. 644–648. doi:10.1038/nclimate1866.
  3. ^ Williams, P. D. (2017). "Increased light, moderate, and severe clear-air turbulence in response to climate change". Advances in Atmospheric Sciences, 34(5), pp. 576–586. doi:10.1007/s00376-017-6268-2.