CLEAR-AIR TURBULENCE AND ITS ANALYSIS BY USE OF RAWINSONDE DATA

This investigation of clear-air turbulence has several parts. The first section reviews selected aspects of turbulence, and emphasizes the large size and persistent nature of certain areas of moderate or severe turbulence. The next section is an investigation of turbulence in pronounced jet stream flow over mountains. In order to test the utility of standard upper-air data in turbulence analysis, values of Richardson's number and the turbulence index were determined by electronic computer in eight layers between 500 and 150 mb at all rawinsonde stations in the United States during the period 12-24 March 1962. These values are compared with turbulence reports made by pilots of jet aircraft and collected by the Clear-Air Turbulence Project. Several maps are presented that illustrate substantial agreement of computed quantities with the turbulence reports. Standard statistical tests show that both the Ri and TI numbers have definite skill in turbulence analysis, and that combined use of the two numbers is more accurate than use of either one separately. Suggestions are given for further improvement of criteria for analyzing turbulence. Experiments in gridpoint analysis of turbulence and in objective turbulence forecasting are recommended.