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

Field Measurements of Terrestrial and Martian Dust Devils

Surface-based measurements of terrestrial and martian dust devils/convective vortices provided from mobile and stationary platforms are discussed. Imaging of terrestrial dust devils has quantified their rotational and vertical wind speeds, translation speeds, dimensions, dust load, and frequency of occurrence. Imaging of martian dust devils has provided translation speeds and constraints on dimensions, but only limited constraints on vertical motion within a vortex. The longer mission durations on Mars afforded by long operating robotic landers and rovers have provided statistical quantification of vortex occurrence (time-of-sol, and recently seasonal) that has until recently not been a primary outcome of more temporally limited terrestrial dust devil measurement campaigns. Terrestrial measurement campaigns have included a more extensive range of measured vortex parameters (pressure, wind, morphology, etc.) than have martian opportunities, with electric field and direct measure of dust abundance not yet obtained on Mars. No martian robotic mission has yet provided contemporaneous high frequency wind and pressure measurements. Comparison of measured terrestrial and martian dust devil characteristics suggests that martian dust devils are larger and possess faster maximum rotational wind speeds, that the absolute magnitude of the pressure deficit within a terrestrial dust devil is an order of magnitude greater than a martian dust devil, and that the time-of-day variation in vortex frequency is similar. Recent terrestrial investigations have demonstrated the presence of diagnostic dust devil signals within seismic and infrasound measurements; an upcoming Mars robotic mission will obtain similar measurement types

History and Applications of Dust Devil Studies

Studies of dust devils, and their impact on society, are reviewed. Dust devils have been noted since antiquity, and have been documented in many countries, as well as on the planet Mars. As time-variable vortex entities, they have become a cultural motif. Three major stimuli of dust devil research are identified, nuclear testing, terrestrial climate studies, and perhaps most significantly, Mars research. Dust devils present an occasional safety hazard to light structures and have caused several deaths

Dust Devil Sediment Transport: From Lab to Field to Global Impact

The impact of dust aerosols on the climate and environment of Earth and Mars is complex and forms a major area of research. A difficulty arises in estimating the contribution of small-scale dust devils to the total dust aerosol. This difficulty is due to uncertainties in the amount of dust lifted by individual dust devils, the frequency of dust devil occurrence, and the lack of statistical generality of individual experiments and observations. In this paper, we review results of observational, laboratory, and modeling studies and provide an overview of dust devil dust transport on various spatio-temporal scales as obtained with the different research approaches. Methods used for the investigation of dust devils on Earth and Mars vary. For example, while the use of imagery for the investigation of dust devil occurrence frequency is common practice for Mars, this is less so the case for Earth. Modeling approaches for Earth and Mars are similar in that they are based on the same underlying theory, but they are applied in different ways. Insights into the benefits and limitations of each approach suggest potential future research focuses, which can further reduce the uncertainty associated with dust devil dust entrainment. The potential impacts of dust devils on the climates of Earth and Mars are discussed on the basis of the presented research results

Applications of electrified dust and dust devil electrodynamics to Martian atmospheric electricity

Atmospheric transport and suspension of dust frequently brings electrification, which may be substantial. Electric fields of 10 kVm-1 to 100 kVm-1 have been observed at the surface beneath suspended dust in the terrestrial atmosphere, and some electrification has been observed to persist in dust at levels to 5 km, as well as in volcanic plumes. The interaction between individual particles which causes the electrification is incompletely understood, and multiple processes are thought to be acting. A variation in particle charge with particle size, and the effect of gravitational separation explains to, some extent, the charge structures observed in terrestrial dust storms. More extensive flow-based modelling demonstrates that bulk electric fields in excess of 10 kV m-1 can be obtained rapidly (in less than 10 s) from rotating dust systems (dust devils) and that terrestrial breakdown fields can be obtained. Modelled profiles of electrical conductivity in the Martian atmosphere suggest the possibility of dust electrification, and dust devils have been suggested as a mechanism of charge separation able to maintain current flow between one region of the atmosphere and another, through a global circuit. Fundamental new understanding of Martian atmospheric electricity will result from the ExoMars mission, which carries the DREAMS (Dust characterization, Risk Assessment, and Environment Analyser on the Martian Surface)-MicroARES (Atmospheric Radiation and Electricity Sensor) instrumentation to Mars in 2016 for the first in situ measurements

TRACERS AND POTENTIAL VORTICITIES IN OCEAN DYNAMICS

The Ertel potential vorticity theorem for stratified viscous fluids in a rotating system is analyzed herein. A set of ‘‘tracers,’’ that is, materially conserved scalar quantities, and the corresponding Ertel potential vorticities are used to obtain an absolute fluid velocity determination (including both horizontal and vertical components) that generalizes earlier formulations known in the literature within the framework of the beta-spiral method. Potential vorticity fields, respectively, of (i) density, (ii) potential temperature, (iii) salinity, and (iv) the latter’s potential vorticities ratio are analyzed in order to infer properties of steady, or quasi-steady, nonhorizontal or slightly viscous currents. For horizontal flows, general conservative properties of a large class of tracer potential vorticities are found and discussed. These ideas are then applied to various steady cases of physical interest, such as density fronts and thermohaline currents. These arguments, together with observational data, are used to obtain some interesting results, even if the values obtained are affected by large experimental errors. Using this method allows the ratio of the vertical and horizontal components of the velocity field to be estimated with greater certainty. Further insight is also gained into a purely hydrological identification of the no-motion level, a classical difficulty in hydrology

Substantiation of the optimum screen brightness parameters of the interactive panel to reduce the risk of general and visual fatigue of schoolchildren

The digital transformation of modern education contributes to the active introduction of interactive panels (IP) into the educational process, replacing traditional chalkboards. Minimizing possible risk factors when using an IP also requires considering the visual characteristics of its screen. At present, there are no results of such studies in the scientific literature. The purpose of this work was to substantiate the optimal range of IP screen brightness when it is used in the classroom to prevent general and visual fatigue of schoolchildren. We analysed research articles describing studies in visual hygiene, lighting engineering, display technologies, etc. Our study involved measuring brightness and pulsation coefficient of a working IP screen. Ranges of IP screen brightness that could produce harmful effects on children's health have been empirically established. With the help of a specially designed questionnaire, complaints of students attending the 4th grade of secondary schools were studied to identify general and visual fatigue, as well as factors caused by the IP and negatively affecting the respondents’ well-being. The relative risk values are calculated, namely a probability that these complaints would occur in schoolchildren, depending on parameters of IP screen brightness. The optimal range of IP screen brightness is justified for a working mode that significantly reduces the probability of students complaining about general and visual fatigue. Monitoring and correction of IP screen brightness mode during classes will reduce the risks of students' health disorders. It is necessary to continue research to substantiate the optimal visual characteristics of the IP screen based on investigating indicators describing the functional state of the child's body