Friction wind speeds in dust devils: A field study

Abstract

Using in‐situ field measurements, we determined surface friction velocities (u * ) and aerodynamic roughness heights (z 0 ) at the base of 10 dust devils. z 0 values agree closely with previous studies in this region and range from 0.1 to 1.0 cm. The peak u * coincide with the largest wind speed measurements within the dust devil and range from 0.9 to 2.4 ms −1 . Surface friction velocities are sufficient to lift all types of windblown material from dust to pebble sized particles. Peak u * values for dust devils appear to be a linear function of the peak wind speed measured at ∼2 m height within the dust devil. This provides a simple approximation for estimating surface shear stress for dust devils.