ON THE ANALYSIS OF CLEAR AIR TURBULENCE BY USE OF RAWINSONDE DATA1

Regions of clear air turbulence in the upper troposphere and lower stratosphere are classified into four groups, and the characteristics of each group are summarized. An empirical turbulence index is defined that describes meteorological conditions associated with a type of turbulent region that is relatively large and that sometimes contains severe turbulence. The turbulence index, Richardson's number, and other meteorological quantities are described in relation to a clearly defined case of turbulence observed by a research aircraft. For the period March 12–24, 1902, vertical shear, lapse rate, Richardson's number, and the turbulence index were calculated by electronic computer from rawinsonde data over the United States. These computed quantities are compared with pilot reports of turbulence. Individual maps are presented that illustrate substantial agreement between computed quantities and turbulence reports. Standard statistical tests show that both Richardson's number and the turbulence index have definite skill in turbulence analysis. Suggestions are given for further improvement of criteria for analyzing turbulence. To enhance turbulence research and operational analysis, the writers believe that a turbulence sensor operated as an integral part of the radiosonde system is very desirable.