Resolution of the size/distance degeneracy of the dust devils signals observed with a stationary meteorological station

Abstract

The monitoring of dust devils using only a meteorological station is limited by the size/distance degeneracy that affects the acquired time series. It is not possible to retrieve directly information on their morphology, translational motion, distance of passage and vortex intrinsic parameters as the core pressure drop and maxima rotational speed. We propose a simple model to estimate the distance of passage (commonly referred to as impact parameter) of the dust devils encounters from the station, monitored using a 2D anemometer. Our technique is based on the study of an easily recognizable feature of the signal trend, univocally connected to the vortex distance of passage. In order to test the model, we have analyzed the measurements acquired during a Sahara field campaign. Our meteorological station was equipped with a camera, to compare the modeled distances with the ones obtained from the images. For all the acquired events the experimental results are in good agreement with the model. Overall, we observed dust devils passing between 3 m and 150 m from the station, assessing the reliability of the technique over a wide range of distances. The evaluation of the impact parameter allows to fully characterize the meteorological encounters and to retrieve the vortex intrinsic parameters. The simplicity of the procedure makes it a powerful tool in the study of the relations among different vortex features (e.g., dust concentration and induced electric field) and their dependence on the distance from the station, easily applicable to past and future terrestrial and martian surveys.