Wind Shear and Turbulence on Titan : Huygens Analysis

Wind shear measured by Doppler tracking of the Huygens probe is evaluated, and found to be within the range anticipated by pre-flight assessments (namely less than two times the Brunt-Vaisala frequency). The strongest large-scale shear encountered was ~5 m/s/km, a level associated with 'Light' turbulence in terrestrial aviation. Near-surface winds (below 4km) have small-scale fluctuations of ~0.2 m/s , indicated both by probe tilt and Doppler tracking, and the characteristics of the fluctuation, of interest for future missions to Titan, can be reproduced with a simple autoregressive (AR(1)) model. The turbulent dissipation rate at an altitude of ~500m is found to be 16 cm2/sec3, which may be a useful benchmark for atmospheric circulation models.