Horizontal path temperature fluctuation measurements were made on board a KC-135 aircraft, at altitudes ranging from 30,000 to 48,000 feet, such that the altitudes below, in, and above the tropopause were sampled. In general, we find that there is a low background level ofturbulence, and there appears to be superimposed on this background higher level turbulent "patches' . These patches are a few kilometers in extent, and the boundaries of these patches are abrupt with the transition to background taking place in distances ofapproximately 50meters. These abrupt boundaries are consistent with the optical measurements taken at the same thne. The measured structure functions are ofthe form D(r) r" with 0.2 n 2 down to scale sizes of 20 cm, which was the limiting resolution ofthe instrumentation. Each ifight segment was conducted under constant conditions (i.e., speed, temperature, altitude). Contrary to expectations, the log slopes of either the power spectral densities or ofthe structure functions are often non-Kolmogorov, as characterized by a k5"3 power spectral density, or by a structure function ofthe form This statement must be tempered, however, by uncertainties in the frequency response ofthe temperature sensor. In addition, the data show regions in which the expected functional relationship (rP +.> k-(P1)) between the structure function and power spectral density does not hold. These characteristics of high altitude turbulence suggest that past measurement techniques used to measure c2 may be inapplicable in the high altitude regime, and c2 as a sole descriptor ofturbulence may be incomplete.

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