Large-Eddy Simulations of Dust Devils and Convective Vortices

Spiga, Aymeric; Barth, Erika L.; Gu, Zhaolin; Hoffmann, Franziska; Ito, Junshi; Jemmett-Smith, Bradley; Klose, Martina; Nishizawa, Seiya; Raasch, Siegfried; Rafkin, Scot; Takemi, Tetsuya; Tyler, D.; Wei, Wei

doi:10.1007/s11214-016-0284-x

Cited by 45 publications

(43 citation statements)

References 101 publications

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“…The purpose of this study was to examine the effect of grid spacing, background wind, and surface heat flux heterogeneities on simulated dust devil-like vortices with the aim of simulating vortices as strong as observed in nature. Though previous studies could successfully reproduce the characteristic structure of dust devils, the core pressure drop of the simulated vortices was almost 1 order of magnitude too small (e.g., Cortese & Balachandar, 1993;Gheynani & Taylor, 2010;Ito et al, 2013;Kanak et al, 2000;Raasch & Franke, 2011).…”

Section: Discussionmentioning

confidence: 88%

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Toward Large‐Eddy Simulations of Dust Devils of Observed Intensity: Effects of Grid Spacing, Background Wind, and Surface Heterogeneities

et al. 2019

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Dust devils are convective vortices with a vertical axis of rotation made visible by lifted soil particles. Currently, there is great uncertainty about the extent to which dust devils contribute to the atmospheric aerosol input and thereby influence Earth's radiation budget. Past efforts to quantify the aerosol transport and study their formation, maintenance, and statistics using large‐eddy simulation (LES) have been of limited success. Therefore, some important features of dust devil‐like vortices simulated with LES still do not compare well with those of observed ones. One major difference is the simulated value of the core pressure drop, which is almost 1 order of magnitude smaller compared to the observed range of 250 to 450 Pa. However, most of the existing numerical simulations are based on highly idealized setups and coarse grid spacings. In this study, we investigate the effects of various factors on the simulated vortex strength with high‐resolution LES. For the fist time, we are able to reproduce observed core pressures by using a high spatial resolution of 2 m, a model setup with moderate background wind and a spatially heterogeneous surface heat flux. It is found that vortices mainly appear at the lines of horizontal flow convergence above the centers of the strongly heated patches, which is in contrast to some older observations in which vortices seemed to be created along the patch edges.

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Section: Discussionmentioning

confidence: 88%

“…Large-eddy simulation (LES) models are the most common method for simulating the development of dust devils in the convective boundary layer (CBL; e.g., Gheynani & Taylor, 2010;Kanak, 2005;Kanak et al, 2000;Ito et al, 2013;Raasch & Franke, 2011). For this task, the simulations have to fulfill two demands.…”

Section: Introductionmentioning

confidence: 99%

Toward Large‐Eddy Simulations of Dust Devils of Observed Intensity: Effects of Grid Spacing, Background Wind, and Surface Heterogeneities

et al. 2019

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“…Wind gusts near the surface of Mars could be quite common and may present an unseen risk to landing spacecraft. Dust devils at least appear to quite common on Mars (Spiga et al, 2016;Chapman et al, 2017;Lorenz & Jackson, 2016) A dust devil or large turbulent eddy may be responsible for the high wind speed near the surface in figure 10 (b). The Phoenix landed in afternoon when the atmosphere is at its most turbulent.…”

Section: Accepted Manuscriptmentioning

confidence: 98%

Measurement of Martian boundary layer winds by the displacement of jettisoned lander hardware

Paton

Harri

Savijärvi

2018

Icarus

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Martian boundary layer wind speed and direction measurements, from a variety of locations, seasons and times, are provided. For each lander sent to Mars over the last four decades a unique record of the winds blowing during their descent is preserved at each landing site. By comparing images acquired from orbiting spacecraft of the impact points of jettisoned hardware, such as heat shields and parachutes, to a trajectory model the winds can be measured. We start our investigations with the Viking lander 1 mission and end with Schiaparelli. In-between we extract wind measurements based on observations of the Beagle 2, Spirit, Opportunity, Phoenix and Curiosity landing sites. With one exception the wind at each site during the lander's descent were found to be <8 m s −1. High speed winds were required to explain the displacement of jettisoned hardware at the Phoenix landing site. We found a tail wind (>20 m s −1), blowing from the northwest was required at a high altitude (>2 km) together with a gust close to the surface (<500 m altitude) originating from the north. All in all our investigations yielded a total of ten unique wind measurements in the PBL. One each from the Viking landers and one each from Beagle 2, Spirit, Opportunity and Schiaparelli. Two wind measurements, one above about 1 km altitude and one below, were possible from observations of the Curiosity and Phoenix landing site. Our findings are consistent with a turbulent PBL in the afternoon and calm PBL in the morning. When comparing our results to a GCM we found a good match in wind direction but not for wind speed. The information provided here makes available wind measurements previously unavailable to Mars atmosphere modellers and investigators.

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“…Convective vortices occur during periods of strong convective heating of the surface, when the ground temperature exceeds the air temperature, warming the air above the surface. As this air rises, existing vorticity becomes more vertical and intensifies, with the air spiraling around a low-pressure region that develops in the vortex core (Balme & Greeley, 2006;Kanak, 2005;Spiga et al, 2016;Toigo et al, 2003). Rotation is randomly clockwise or counterclockwise, and vortices often occur in pairs or clusters (Balme & Greeley, 2006).…”

Section: Introductionmentioning

confidence: 99%

MarsWRF Convective Vortex and Dust Devil Predictions for Gale Crater Over 3 Mars Years and Comparison With MSL‐REMS Observations

et al. 2019

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Key Points MarsWRF output combined with thermodynamic theory is used to predict temporal and spatial trends of “dust devil activity” in Gale Crater Modeled activity and observed vortex pressure drops are both greatest in local summer, peaking ~13:00‐14:00, and smallest in winter Sensible heat flux drives increased activity as MSL climbs, but pressure drop numbers increase faster, unless a threshold activity is used

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Large-Eddy Simulations of Dust Devils and Convective Vortices

Cited by 45 publications

References 101 publications

Toward Large‐Eddy Simulations of Dust Devils of Observed Intensity: Effects of Grid Spacing, Background Wind, and Surface Heterogeneities

Toward Large‐Eddy Simulations of Dust Devils of Observed Intensity: Effects of Grid Spacing, Background Wind, and Surface Heterogeneities

Measurement of Martian boundary layer winds by the displacement of jettisoned lander hardware

MarsWRF Convective Vortex and Dust Devil Predictions for Gale Crater Over 3 Mars Years and Comparison With MSL‐REMS Observations

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