Atmospheric Turbulence Measurements Obtained from Airplane Operations at Altitudes Between 20,000 and 75,000 Feet for Several Areas in the Northern Hemisphere

Measurements of clear-air turbulence by use of airplane-borne instrumentation have been obtained from NASA VGH recorders during research flights of Lockheed U-2 airplanes to altitudes of 75,000 feet over several areas of the Northern Hemisphere. An analysis of these data has indicated that for the higher altitudes (50,000 to 75,000 feet), turbulence is both less frequent and less severe than for the lower altitudes (20,000 to 50,000 feet). Turbulence appears to be present at the high altitudes (60,000 to 75,000 feet) less than 1 percent of the time. Moderately heavy turbulence appears to exist on occasion at altitudes of about 50,000 feet over Japan. As a consequence, the gust experience appears to be more severe for operations over Japan than for the other areas. Less than 50 percent of the turbulent areas exceeded 10 miles in length.