Areas of non-occurrence as well as ar eas of occurrence of high level clear air turbulence (CAT) over the South Pacific Region were determined for a five-day period in September 1965. Latitude-longitude 'square' of 2.5° were used for tabulation of the flight data. Flights were divided into (1) flights at and below 30,000 ft and (2) flights above 30,000 ft. Frequency distributions and percentages of CAT occurrences were computed for geographical distributions, flight elevations and for various parameters mainly of a meteorological nature. In a study covering all flight squares the most successful parameter was vertical wind shear in the layer 10,000 ft below the maximum wind. Thirty-five percent of flights encountered CAT, which was mostly light. No severe or extreme CAT was reported. In a study covering a restricted area Richardson's number was the best of the six parameters investigated.
J. R. Colquhoun (Thu,) studied this question.