Dust Devils Research Articles

The Development of Simulated Dust-Devil-Like Vortices

Abstract In this study, the cause of rotation in simulated dust-devil-like vortices is investigated. The analysis uses a numerical simulation of an initially resting, dry, atmosphere, in which uniform surface heating leads to the development of a growing convective boundary layer (CBL). As soon as convective mixing sets in, regions of weak vertical vorticity develop at the lowest model level. Using forward trajectories, this vorticity is shown to originate from horizontal baroclinic production and simultaneous reorientation into the vertical within the descending branches of the convective cells. The requirement for vertical vorticity production in the downdraft cells is shown to be a nonaxisymmetric horizontal footprint of the downdraft regions. The resulting vertical vorticity is not initially associated with rotation. However, as the CBL matures, like-signed vortex patches merge, the vertical vorticity magnitude increases due to stretching, and deformation in the vortex patch decreases, leading to the development of vortices. The ultimate origin of the vortices is thus initially horizontal vorticity that has been produced baroclinically and that has subsequently been reoriented into the vertical in sinking air. Significance Statement Dust devils are concentrated vortices consisting of rapidly rising buoyant air, which may pose a risk to small aircraft and light structures on the ground. Although these vortices are a common occurrence in convective boundary layers, the origin of the vorticity within these vortices has not yet been fully established. The present study uses a numerical simulation of an evolving convective boundary layer and analyzes air parcel trajectories to identify the origin of vertical vorticity at the surface during dust-devil formation. The work contributes an answer to the long-standing question of what causes dust devils to spin.

Spectral location for the universal scaling regime in Martian atmospheric turbulence

Atmospheric turbulence, irregular fluctuations of the fluid state, is studied on Mars. Universality of the turbulence spectrum underpins atmospheric models where computational requirements preclude full fidelity simulations of the smallest scales. However, there are discrepancies among reports on the existence and spectral location of universal scaling in Martian atmospheric data. Here, results indicate the smallest resolvable structures from Martian wind speed data are still associated with the energetic regime, which may ultimately explain why multiple reports have not found a consistent Kolmogorov-like spectral regime on Mars. Universal spectral scaling of wind data from Perseverance’s Mars Environmental Dynamics Analyzer is used to estimate the thresholds that separate three turbulence regimes: energetic, inertial, and molecular dissipation. Wind measurements at 2-Hz, the fastest sampling rate for direct wind sensor measurements on Mars, resolves turbulence in the energetic regime and approaches the inertial regime, which is consistent with reported Martian dust devil sizes.

Physical Modeling of Structure and Dynamics of Concentrated, Tornado-like Vortices (A Review)

Physical modeling is essential for developing the theory of concentrated, tornado-like vortices. Physical modeling data are crucial for interpreting real tornado field measurements and mathematical modeling data. This review focuses on describing and analyzing the results of a physical modeling of the structure and dynamics of tornado-like vortices, which are laboratory analogs of the vortex structures observed in nature (such as “dust devils” and air tornadoes). This review discusses studies on various types of concentrated vortices in laboratory conditions: (i) wall-bounded, stationary, and tornado-like vortices, (ii) wall-free, quasi-stationary, and tornado-like vortices, and (iii) wall-free, non-stationary, and tornado-like vortices. In our opinion, further progress in the development of the theory of non-stationary concentrated tornado-like vortices will determine the possibility of setting up the following studies: conducting experiments in order to study the mechanisms of vortex generation near the surface, determining the factors contributing to the stabilization (strengthening) and destabilization (weakening) of the generated vortices, and to find methods and means of controlling vortices.

Albedo analysis of dust devil-induced slope streaks and tracks on Mars

Despite frequent observations of slope streaks and dust devil tracks on the same slopes in various regions on Mars, only a few instances in Arabia Terra have documented slope streaks directly triggered by dust devils. Here we present new observations of dust devil-induced slope streaks in Elysium Planitia and Amazonis Planitia. These observations represent a rare opportunity to study the erosional effects of both dust devils and slope streaks on the martian surface. Since dust devil tracks and the triggered streaks are formed basically simultaneously and are therefore subject to similar alteration processes, e.g., settling dust from the atmosphere, the relative albedo of these features can be determined using high-resolution orbital images. Our relative albedo analyses of twelve dust devil-induced slope streaks revealed that slope streaks appear substantially darker than the respective dust devil tracks. These observations might indicate a stronger erosion of fine-grained material by slope streaks compared to dust devils.

Results from the InSight atmospheric imaging campaign

NASA's InSight lander monitored the Martian atmosphere while conducting its primarily geophysical investigation. Atmospheric imaging was used to study dust and ice at the site for over two Mars years in 2018–2022. An optical depth record, including dust and ice, was derived from systematic sky imaging in the mornings (for the first part of the mission) and evenings. Optical depths ranged from 0.5 to 1.9 but were typically under 1. Dust storms were seen at expected times in late northern autumn and early winter, including one shortly after landing, along with one late summer storm in January 2022. The optical depth record closely matched that of Curiosity, 600 km to the south, except for the expected additional water ice content during the aphelion cloud belt (ACB, spring to early summer). In addition to ice hazes, the ACB included discrete clouds, whose motion was tracked to show northeasterly to southeasterly daytime winds. While InSight recorded many meteorological vortices, no dust devils were seen, requiring that dust-devil occurrence was <10−3 times as common as during Spirit rover dust devil seasons.

First quantitative characterization of the Martian dust devil dimensions determined from InSight data

In a pioneer study, the dimensions height H and width D of Martian dust devils are determined considering a simple model, in which the principal contribution to the magnetic field generated by a dust devil, comes from the swirling motion of their negatively charged lighter particles. Finally, a linear relation between H/D and the pressure drop associate to the dust devils is found. This relationship is a new and very conspicuous result determined in the present study. The reliability of this result should be assured revisiting this work with the data provided by future missions, as the Exobiology on Mars (ExoMars) project, when these data sets be available.

Novel design of multi-point injection system for laboratory simulation of Martian low-pressure dust devils

The Martian surface is frequently traversed by dust devils, presenting formidable challenges to exploration missions and posing significant safety risks. Establishing a ground-based simulation device for low-pressure Martian dust devils is essential for conducting reliability testing and research on extreme environments relevant to Mars rovers. This study introduces a Martian dust devil simulator comprising a simulation cabin and multi-point injectors. This apparatus facilitates the investigation of velocity and pressure distribution patterns within the flow field under varying operational conditions by adjusting injector positions, inlet pressure, and internal pressure. The simulator's design allows it to replicate Martian dust devil velocity fluctuations from 0 to 50 m/s and pressure variations spanning 100–1500 Pa, thereby meeting crucial criteria for simulating Martian atmospheric conditions. Through computational fluid dynamics (CFD) simulation, we analyzed the characteristics of dust devils generated by the simulation device and scrutinized the flow field properties following the coupling of sand-dust particles with airflow. The observed dust devil flow field closely resembles the Vastitas Borealis vortex. Additionally, experimental research was conducted. Comparing experimental, simulated, and theoretical models revealed a high degree of consistency in the internal flow field characteristics of the simulated dust devils. The apparatus's versatility extends to simulating various dust devil morphologies, offering significant potential for conducting model experiments pertinent to Martian probes and facilitating future crewed Mars exploration endeavors.

Saltation‐Induced Dust Emission of Dust Devils in the Convective Boundary Layer—An LES Study on the Meter Scale

AbstractDust devils are vertically oriented, columnar vortices that form within the atmospheric convective boundary layer (CBL) of dry regions. They are able to lift a sufficient amount of soil particles including dust to become visible and are considered as a potentially important dust source for the atmosphere. Mineral dust, a key component of atmospheric aerosols, influences the climate by affecting the radiation budget and cloud formation. Current estimates of the contribution of dust devils to the global, regional, and local dust release vary considerably from less than 1% to more than 50%. To address this uncertainty, we perform the highest resolved large‐eddy simulation (LES) study on dust emission in the CBL to date, using the PALM model system and the saltation‐based Air Force Weather Agency (AFWA) dust emission scheme. Our results show that under desert‐like conditions, dust devils are responsible for an average of 5% of regional dust emissions, with temporary maxima of up to 15%. This contrasts with previous measurement‐based (&gt;35%) and LES‐based estimates (∼0.1%). Local emissions of dust devils (up to 10 mg m−2 s−1) are 1–3 orders of magnitude higher than the emission in the surroundings. This makes dust devils important for air quality and visibility. Additionally, our study reveals previously unknown large‐scale convective dust emission patterns. These patterns are tied to the CBL's cellular flow structure and are the main cause of dust release. Contrary to other studies, our findings clarify the important role of saltation‐induced dust emission.

Model for the cyclonic bias of convective vortices in a rotating system

In convective fluids, small vortices develop between neighboring convective cells. Familiar in the atmosphere in the form of dust devils and water spouts, these convective vortices have been seen in simulations of oceanic convection where the vortices exhibit an unexplained bias towards cyclonic rotation despite having a large Rossby number. Here we use large eddy simulations (LES) of an idealized oceanic convective mixed layer and vary independently the Coriolis acceleration and the surface buoyancy flux to investigate the development of the cyclonic bias of convective vortices. While large convective vortices are biased for sufficiently large values of the Coriolis parameter, small convective vortices do not exhibit a clear bias. Using Lagrangian particles, we find that the large convective vortices develop through the merger of many small convective vortices. We propose a statistical theory to predict the cyclonic bias of large convective vortices composed of many small unbiased convective vortices and test the theory using LES results. We apply the theory to typical convective conditions and find that convective vortices in upper ocean mixed layers are expected to exhibit a bias, while convective vortices in the terrestrial and Martian atmospheres are expected to be largely unbiased. Published by the American Physical Society 2024

An Accurate and Automated Convective Vortex Detection Method for Long-Duration Infrasound Microbarometer Data

Abstract Heating of the surficial layer of the atmosphere often generates convective vortices, known as “dust devils” when they entrain visible debris. Convective vortices are common on both Earth and Mars, where they affect the climate via dust loading, contribute to wind erosion, impact the efficiency of photovoltaic systems, and potentially result in injury and property damage. However, long-duration terrestrial convective vortex activity records are rare. We have developed a high-precision and high-recall method to extract convective vortex signatures from infrasound microbarometer data streams. The techniques utilizes a wavelet-based detector to capture potential events and then a template matching system to extract the duration of the vortex. Since permanent and temporary infrasound sensors networks are present throughout the globe (many with open data), our method unlocks a vast new convective vortex dataset without requiring the deployment of specialized instrumentation. Significance Statement Convective vortices, or “dust devils,” contribute to regional dust loading in Earth’s atmosphere. However, long-duration convective vortex activity records are rare. We came up with a way to autonomously detect the pressure signatures left by convective vortices striking low-frequency sound, or “infrasound,” sensors. Since permanent infrasound stations have been active for decades, our method has the potential to add orders-of-magnitude more events than previously catalogued.

First results of the potential gradient variation in a tropical station in South America (Ica, Peru)

Measurements of the potential gradient (PG) under fair weather conditions at new locations are crucial for monitoring the global electric circuit. In this study, we analyzed the variations in PG recorded in Ica city, Peru, during the period from March 2018 to December 2022. Our analysis involved a detailed comparison of PG with various meteorological parameters such as rainfall, wind speed and direction, dust storms, dust devils and fog to establish the characteristic PG curve under fair weather conditions (referred to as the standard curve). We identified a significant threshold of 3.5 m/s for strong winds, which helps prevent the influence of sea breeze and dust lifting on PG. Our results showed the impact of 'Paracas' dust storms on PG, which aligns with patterns observed in other arid regions worldwide. Subsequently, we calculated monthly, seasonal, and annual averages of the standard curve which showed a response likely associated with local convective processes on the PG diurnal variation. Furthermore, the seasonal variation of PG reveals higher values during June, July, and August compared to December, January, and February. These differences are attributed to seasonal changes in aerosol concentrations, potentially influenced by biomass-burning activities in Peru. Additionally, we performed a wavelet transform analysis of PG hourly values. We found the periodicities of 1 day, ∼188 days, and 360 days which are related to the diurnal, semiannual and annual periods. During the months between January and March 2018 was found an intense period of ∼45-day likely associated with one of the strongest Madden-Julian Oscillation events. Through this comprehensive investigation, we deepen our understanding of the intricate relationships among meteorological conditions, sea breeze, dust storms, and the PG in arid regions like Ica.

Lab-based Martian analogue experiments investigating electric and magnetic fields of dust devils

Dust devils – rotating vortices of lofted particulates formed by convection from solar heating - are a prevalent aspect of Martian weather.Within a dust devil, particles become charged though triboelectrification, and observations of terrestrial dust devils have revealed electric and magnetic fields. Understanding the behaviour of these aeolian events is vital for mission planning and duration, for example, with the Insight lander as a prime example of a mission cut short due to obscuration of solar panels by lofted dust, which is highly likely to be charged. Charged dust devils on Mars strongly imply the existence of electric discharges due to the low breakdown field. The existence of discharges would in turn imply a global electric circuit on the planet – with implications for organic chemical formation and methane losses.This work presents a laboratory-based experimental set up for investigation into both electric and magnetic fields and the feasibility of using Martian analogue dust as alternative to in-situ measurements. In a dust devil, there are two main driving motions – a vertical separation of small and large particles, and the characteristic tight spiralling motion. The experimental set-up splits these components, allowing investigation into each. It is made up of a carefully designed cylindrical tank into which dusts or powders can be dropped to allow triboelectric charging as they fall under gravity. The base of the tank has a Faraday cup for charge measurement and there is also a field mill looking into the tank from the top. The rotational component is achieved using a paddle arrangement for samples placed in the base of the tank. Electric and magnetic fields have successfully been detected from charged dust with this system.

Martian Dust Devil Detection Based on Improved Faster R-CNN

Martian Dust Devil Detection Based on Improved Faster R-CNN

An atmospheric vortex and its induced loading on a bluff body

Atmospheric vortices such as tornadoes are responsible for some of the most extreme winds on Earth and generate tremendous amounts of damage. Characteristics of atmospheric vortices and induced loading in bluff bodies remain largely unknown, presenting a challenge for safe infrastructure design. Experimental and computational studies have investigated loading from tornado-like vortices and design standards are beginning to address tornado loading, however full-scale validation is lacking. For the first time and unprecedented detail, we show the characteristics and the loading induced in a bluff body by an atmospheric vortex (i.e., dust devil). The analysis indicates that vortices load bluff bodies differently than winds in the atmospheric boundary layer and that current design practice may be insufficient to deal with vortex-induced loading. Moreover, it is shown that a feasible way of characterizing vortex phenomena and their effects on bluff bodies can be through dust devil capture.

Using the Perseverance MEDA-RDS to identify and track dust devils and dust-lifting gust fronts

In the framework of the Europlanet 2024 Research Infrastructure Transnational Access programme, a terrestrial field campaign was conducted from 29 September to 6 October 2021 in Makgadikgadi Salt Pans (Botswana). The main goal of the campaign was to study in situ the impact of the dust devils (DDs) on the observations made by the radiometer Radiation and Dust Sensor (RDS), which is part of the Mars Environmental Dynamics Analyzer instrument, on board NASA’s Mars 2020 Perseverance rover. Several DDs and dust lifting events caused by non-vortex wind gusts were detected using the RDS, and the different impacts of these events were analyzed in the observations. DD diameter, advection velocity, and trajectory were derived from the RDS observations, and then, panoramic videos of such events were used to validate these results. The instrument signal variations produced by dust lifting (by vortices or wind gusts) in Makgadikgadi Pans are similar to those observed on Mars with the RDS, showing the potential of this location as a Martian DD analog.

Dust Lifting Observations With the Mars Science Laboratory Navigation Cameras

AbstractMartian dust lifting is believed to occur through two primary mechanisms: dust devils and wind stress forced dust lifting. Gale Crater's varied terrain and meteorology provide a unique in situ perspective on Martian dust lifting, with the Mars Science Laboratory Curiosity rover passing through both conditions and locations detrimental to dust lifting (e.g., the crater floor) and those with active sand motion and frequent dust lifting (e.g., the Bagnold Dunes). Between Ls = 248° in Mars Year 33 and Ls = 51° in Mars Year 37, over ∼3.5 Mars years and 2,300 sols, the rover's Navigation Cameras took 1,260 dedicated image sequences to search for dust lifting. Approximately 42.7% of all sequences, and 9.5% of the total images have shown active dust lifting, both dust devils and linear/straight‐line wind stress dust lifting. 79% of dust lifting events are classified as dust devils, while ∼16% are linear wind stress dust lifting and the remainder are of an indeterminate type. We analyze this large catalog of dust lifting events to provide ground truth on theoretical and model expectations of dust lifting and show that dust lifting in Gale Crater occurs throughout the Martian year, is strongly peaked in frequency near solar noon (even after accounting for observational biases), and that dust lifting shows an affinity for sand‐covered surfaces which highlights the importance of saltating sand grains for Martian dust lifting in both dust devils and wind stress forced lifting.

Observation and numerical simulation of dust devils at the Hong Kong International Airport in sea breeze situation

Dust devils at Hong Kong International Airport in two consecutive days in the summer of Hong Kong are documented. They are found to be related to the sea breeze convergence lines and are anticyclonic. The background meteorological conditions under which the dust devils occur are documented. The computer simulation of the tiny anticyclonic flow at the sea breeze convergence line is studied. This paper discusses the difficulties in the micro-scale simulation of the sea breeze circulation in an area of complex terrain and the successful reproduction of the sense of rotation of the dust devil flow. It is hoped that the paper could be a useful reference for the studies of dust devils in the literature.

Improving resilience of sensors in planetary exploration using data-driven models

Improving the resilience of sensor systems in space exploration is a key objective since the environmental conditions to which they are exposed are very harsh. For example, it is known that the presence of flying debris and Dust Devils on the Martian surface can partially damage sensors present in rovers/landers. The objective of this work is to show how data-driven methods can improve sensor resilience, particularly in the case of complex sensors, with multiple intermediate variables, feeding an inverse algorithm (IA) based on calibration data. The method considers three phases: an initial phase in which the sensor is calibrated in the laboratory and an IA is designed; a second phase, in which the sensor is placed at its intended location and sensor data is used to train data-driven model; and a third phase, once the model has been trained and partial damage is detected, in which the data-driven algorithm is reducing errors. The proposed method is tested with the intermediate data of the wind sensor of the TWINS instrument (NASA InSight mission), consisting of two booms placed on the deck of the lander, and three boards per boom. Wind speed and angle are recovered from the intermediate variables provided by the sensor and predicted by the proposed method. A comparative analysis of various data-driven methods including machine learning and deep learning (DL) methods is carried out for the proposed research. It is shown that even a simple method such as k-nearest neighbor is capable of successfully recovering missing data of a board compared to complex DL models. Depending on the selected missing board, errors are reduced by a factor between 2.43 and 4.78, for horizontal velocity; and by a factor between 1.74 and 4.71, for angle, compared with the situation of using only the two remaining boards.

Gentle Perseverance Lifts the Veil on Martian Dust

AbstractObservations with sensitive photodiode detectors on the Perseverance rover (Hueso et al., 2023, https://doi.org/10.1029/2022JE007516; Vicente‐Retortillo et al., 2023, https://doi.org/10.1029/2022je007672) to detect dust devils and track formation, and movies of the Ingenuity helicopter's downwash impingement on the Martian surface (Lemmon et al., 2022a, https://doi.org/10.1029/2022je007605; Lemmon et al., 2022b, https://doi.org/10.1029/2022gl100126), together with in‐situ meteorological data, give new insights into the important problem of dust‐lifting on Mars, a phenomenon which influenced the lifetime of recent rovers and landers. These results, together with new low‐gravity wind tunnel experiments on parabolic flights and interpretation of the large blast pattern from lander retrorockets, indicate that particle motion and visible darkening on Mars can result from aerodynamic pressures of only 1–5 Pa, considerably less than previously thought.

Description of Martian Convective Vortices Observed by InSight and Implications for Vertical Vortex Structure and Subsurface Physical Properties

AbstractConvective vortices (whirlwinds) and dust devils (dust‐loaded vortices) are one of the most common phenomena on Mars. They reflect the local thermodynamical structure of the atmosphere and are the driving force of the dust cycle. Additionally, they cause an elastic ground deformation, which is useful for retrieving the subsurface rigidity. Therefore, investigating convective vortices with the right instrumentation can lead to a better understanding of the Martian atmospheric structures as well as the subsurface physical properties. In this study, we quantitatively characterized the convective vortices detected by NASA's InSight (∼13,000 events) using meteorological (e.g., pressure, wind speed, temperature) and seismic data. The evaluated parameters, such as the signal‐to‐noise ratio, event duration, asymmetricity of pressure drop profiles, and cross‐correlation between seismic and pressure signals, are compiled as a catalog. Using these parameters, we investigated (a) the vortex structure and (b) the subsurface physical properties. Regarding the first topic, we tried to illustrate the vertical vortex structure and its link to the shape of the pressure profiles by combining the asymmetrical features seen in the observed pressure drops and the terrestrial observations of dust devils. Our results indicate that most of the vortices move with the wall tilted in the advection direction. Concerning the second topic, selecting the highly correlated events between pressure perturbation and ground response, we estimated the subsurface rigidity at the InSight landing site down to 100 m depth. Our results indicate that the subsurface structure can be modeled with two layers having a transition at 5–15 m depth.