THE TURBULENCE CLIMATOLOGY OF THE UNITED STATES BETWEEN 20,000 AND 45,000 FEET ESTIMATED FROM AIRCRAFT REPORTS AND METEOROLOGICAL DATA

The climatology of clear-air turbulence is defined herein as the likelihood that an aircraft or missile will encounter turbulent air at a given locality, altitude, and time of year. Turbulence data of three types were used in this study; these include observations by instrumented research aircraft, balloon tracks measured by FPS-16 radar, and turbulence reports made by pilots. The FPS-16 tracks of rising Jimsphere and Rose balloons were obtained during studies of detailed wind profiles. We investigated their potential value in identifying turbulent layers. The subjective turbulence reports from pilots collected during special five-day reporting periods comprise by far the largest volume of data available. Meteorological conditions for these periods were analyzed by computer from standard rawinsonde data and were correlated with the turbulence reports. Optimum multiple regression equations between turbulence frequency and the mean and standard deviation of the vertical vector wind shear were obtained. In summer a different regression equation was found than in other seasons.