ANALYSIS OF CLEAR AIR TURBULENCE DURING APRIL 1960

Abstract

Clear air turbulence (C-A-T) occurrences over the United States reported by pilots in April 1960 are analyzed with reference to weather conditions, wind speed, horizontal and vertical wind shear, thermal stability, and jet stream location and curvature. The day-by-day plot of the occurrences shows that the peak of the C-A-T activity was associated with sharp and well developed troughs which extended far to the south. In the analysis of the data, it is found useful to separate the cases east and west of 103° W. longitude. The cases west of 103° W. indicate greater importance of higher stability and less importance of large horizontal wind shear. The cases east of 103° W., away from the influence of the western mountains, indicate greater importance of decreased stability when combined with either large horizontal or vertical wind shear. Well developed jet streams were apparent with the occurrences in both areas. However, the western cases show a preponderance of cyclonic curvature while the eastern cases show nearly equal division between cyclonic and anticyclonic curvature.