Nature and Intensity of Clear Air Turbulence

The phenomenon of CAT is reviewed indicating the role of wind shear, gravity waves, Richardson number and other indices in relation to turbulence intensity. Standard CAT intensity criteria are reviewed, including vertical accelerations, derived gust velocities, and airspeed fluctuations. Various descriptive criteria are reviewed along with some newer concepts such as “chop”. A panel has teen established to up-date the current intensity criteria. A research flight program is now underway which will furnish a more complete understanding of CAT and a basis for a more quantitative set of intensity criteria.