We analyze boundary layer velocity and temperature measurements acquired by aircraft at 22 Hz. The calculated longitudinal velocity third-order structure function yields approximate agreement with Kolmogorov's four-fifths law for the scale range ~10--100 m with a downscale energy flux of ~4¿10-5 m2 s-3. For scales greater than ~10 km the sign is reversed, implying an inverse energy cascade with an estimated flux of ~10-5 m2 s-3 associated with two-dimensional stratified turbulence. The mixed structure function of longitudinal velocity and squared temperature increment follows Yaglom's four-thirds law in the same scale range, yielding an estimated downscale temperature variance flux of ~5¿10-7 K2 s-1. Analysis of higher-order structure functions yields anomalous scaling for both velocity and temperature. The scaling also reveals second-order multifractal phase transitions for both velocity and temperature data. Above the transition moments, asymptotes varying with the number of realizations argue against the log-Poisson model. The log-L¿vy model is better able to explain the observed characteristics. ¿ 2001 American Geophysical Union