Dust Devil Populations and Statistics

The highly-skewed diameter and pressure drop distributions of dust devils on Earth and Mars are noted, and challenges of presenting and comparing different types of observations are discussed. The widely- held view that Martian dust devils are larger than Earth\u27s is critically-assessed: the question is confounded somewhat by different observation techniques, but some indication of a ~3x larger population on Mars is determined. The largest and most intense (in a relative pressure sense) devils recorded are on Mars, although the largest reported number density is on Earth. The difficulties of concepts used in the literature of \u27average\u27 diameter, pressure cross section, and area fraction are noted in the context of estimating population-integral effects such as dust lifting

Ice-vapor equilibrium fractionation factor of hydrogen and oxygen isotopes: Experimental investigations and implications for stable water isotope studies

International audienc

Evolution and Features of Dust Devil‐Like Vortices in Turbulent Rayleigh‐Bénard Convection—A Numerical Study Using Direct Numerical Simulation

Dust devils are convective vortices with a vertical axis of rotation that are made visible by entrained soil particles. These soil particles contribute to the atmospheric aerosol input, influencing the Earth radiation budget. Quantifying this contribution requires reliable information about the statistics of dust devils, their formation process, and how they are maintained. In the past, this information was mainly derived from field experiments and large-eddy simulations (LESs). Field experiments suffer from the erratic occurrence of dust devils and the limited area that can be monitored reliably. In LESs, dust devils cannot be resolved completely, especially close to the ground. Additionally, they are affected by numerical features of surface boundary conditions, as well as subgrid-scale models in an unknown way. To mitigate these limitations, we employ direct numerical simulations (DNSs) to improve our understanding of dust devils. We comprehensively investigate the statistics and structure of dust devils for Rayleigh numbers up to 1011 using DNS of Rayleigh-Bénard convection between two plates for the first time. We find that dust devil-like structures occur in DNS with Rayleigh numbers much lower than in the atmosphere (≥107). These results support previous DNS studies in which vortices with vertical axes were observed but not further investigated. The dust devil statistics strongly depend on the Rayleigh number and velocity boundary conditions, but depend little on the aspect ratio of the model domain. Simulated dust devils show very similar properties to convective vortices analyzed in LESs of the atmospheric boundary layer. © 2021. The Authors

Particle Lifting Processes in Dust Devils

Particle lifting in dust devils on both Earth and Mars has been studied from many different perspectives, including how dust devils could influence the dust cycles of both planets. Here we review our current understanding of particle entrainment by dust devils by examining results from field observations on Earth and Mars, laboratory experiments (at terrestrial ambient and Mars-analog conditions), and analytical modeling. By combining insights obtained from these three methodologies, we provide a detailed overview on interactions between particle lifting processes due to mechanical, thermal, electrodynamical and pressure effects, and how these processes apply to dust devils on Earth and Mars. Experiments and observations have shown dust devils to be effective lifters of dust given the proper conditions on Earth and Mars. However, dust devil studies have yet to determine the individual roles of each of the component processes acting at any given time in dust devils