Meteorological characterization of the Moroccan dust devils and implications for dust lifting processes

In this report we present the analysis of Moroccan dust devils observed in a field campaign performed in 2014. Our main objective is to use a huge set of measured physical parameters to study the environmental conditions where... [ view full abstract ]

In this report we present the analysis of Moroccan dust devils observed in a field campaign performed in 2014.
Our main objective is to use a huge set of measured physical parameters to study the environmental conditions where dust devils occur and characterize them in a more exhaustive way than in the past. In particular we focus on the dust devils induced electric field, an aspect which is still poorly understood.
This analysis has several implication for Mars science. Dust devils are one of the main processes that drive the injection of dust in Martian atmosphere, thus impacting the global climate. In addition, the atmospheric electrical phenomena are an important factor for the atmospheric chemistry and the habitability of the planet, through their role in the production of oxidized constituents.
The field campaign has been performed in the West Sahara, in the Merzouga region, an area very active from the aeolian point of view.
We performed our work using a fully equipped meteorological station that acquires synchronized measurement of wind speed, wind direction and air temperature at differente heights. Further more we also acquire other parameters like pressure, solar radiation, air and soil humidity, dust lifting processes and electric field.
The data were collected continuously 24 h/day, for about two months during the dust storm season using an high sampling rate.
We developed a new type of semi-automatic dust devils detection algoritm starting from the fluctuation of the electric field. We focused on the events that overtake an established electric fluctuation threshold and then we checked for atmosferic pressure and wind (speed and direction) variations. The selected events have been manually controlled to remove the false positives.
We present the typical time evolution of the weather variables for many single dust devils events, and the relation between the variation of these parameters with their background values.
We also show the relations found between the wind and the pressure variations, sand and dust lifted.
For the first time we show how the dust devils electric field is connected to the other physical parameters like pressure and vortex speed.
Our study will also help the analysis of future acquisition of the DREAMS station on board of the ExoMars 2016 mission. DREAMS will operate in dust envoironment with high probability to detect also dust devils and will collect the first measures of Martian atmosferic electric field.