Dust devils: Characteristics of the forward motion from a Saharan survey

Abstract

Dust devils have been proposed as a tool to investigate martian near-ground wind conditions. However, further studies are needed in order to fully understand how background atmospheric conditions affect dust devil forward motion. One of the main issues is related to the lack of synchronous acquisition of the dust devils forward speed and ambient wind measurements. <P />This work aims to present an effective methodology to retrieve the dust devil translational velocity using the horizontal wind time series acquired by a single stationary anemometer, and utilize this method to deeply investigate its relation with the ambient velocity. <P />For this purpose, we first tested the reliability of our method using the data acquired during an intensive week-long dust devil survey, during which we deployed a meteorological station coupled with a camera in a Sahara desert site. After confirming the technique by comparing the results with the ones obtained with the camera, we applied the method to a meteorological data set of 338 dust devil events we acquired in a previous Saharan campaign. We studied the characteristics of the forward velocity, observing how it closely matches the ambient wind regime, with ~70% of the events lying in a range of 20° and 1 m/s from the ambient velocity measured at 4.5 m. Our results indicate how the vortex forward speed follows a vertical profile similar to the boundary layer wind, confirming the effectiveness of the dust devils monitoring for the study of the surface winds.