The shape of the barchan dunes of Southern Morocco

Sauermann, Gerd; Rognon, Pierre; Poliakov, Alexei N. B.; Herrmann, Hans J.

doi:10.1016/s0169-555x(00)00047-7

Cited by 152 publications

(170 citation statements)

References 9 publications

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“…For large dunes, w ≪ W and the integral is estimated as 2ρ s vLℓ ⊥ H/W . Using v ∝ L −1 [14,15], we conclude that the transverse aspect ratio H/W should, for given wind and influx conditions, not depend on dune size if the horn width w does not, in accord with field observations [11,20].…”

Section: Transverse Profilessupporting

confidence: 62%

“…The insets demonstrate exemplarily that all windward profiles are well represented by with α ≈ 3.0 for dunes and α ≈ 1.8 for heaps (H e , L e are defined in figure 1b). Such collapse of the windward profiles is strongly supported by field data [1,20]. Moreover, the height-length relations for diverse masses and wind speeds can be superimposed on a single master curve by rescaling lengths and heights by their values H c , L c at the shape transition.…”

Section: Longitudinal Profilesmentioning

confidence: 58%

“…This implies that asymptotically large dunes, which should have a universal scale-invariant shape, are most easily produced in water [3,4,10]. The similarity rule (1) is well supported by a comparison of aeolian and submarine dunes [10,14,20]. However, there may be some evidence [5,25] that it overestimates the scale factor between dunes on Earth and on Mars.…”

Section: Similarity Hypothesismentioning

confidence: 90%

“…For a schematic sketch that introduces some of the terminology see figure 1. By identifying and isolating the mechanisms that are essential for dune formation, a mathematical minimal model could recently be formulated [15,16], and was shown to reproduce generically field observations reporting systematic shape variations [20]. In particular, shape transitions from dunes (with slipface) to smooth heaps as a function of sand mass were predicted [1,15,16].…”

Section: Introductionmentioning

confidence: 99%

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The shape of barchan dunes

Kroy

Fischer

Obermayer

2005

J. Phys.: Condens. Matter

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Abstract. Barchans are crescent-shaped sand dunes forming in aride regions with unidirectional wind and limited sand supply. We report analytical and numerical results for dune shapes under different environmental conditions as obtained from the so-called 'minimal model' of aeolian sand dunes. The profiles of longitudinal vertical slices (i.e. along the wind direction) are analyzed as a function of wind speed and sand supply. Shape transitions can be induced by changes of mass, wind speed and sand supply. Within a minimal extension of the model to the transverse direction the scale-invariant profile of transverse vertical cuts can be derived analytically.

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Section: Transverse Profilessupporting

confidence: 62%

Section: Longitudinal Profilesmentioning

confidence: 58%

Section: Similarity Hypothesismentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The shape of barchan dunes

Kroy

Fischer

Obermayer

2005

J. Phys.: Condens. Matter

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“…Besides the field measurements, several controlled experiments and, recently, numerical simulations to model the dunes, had been proposed and made [2,4,[6][7][8][9][10][11][12][13]; however, field measurements are still fundamental to have information on the links of some specific features, such as the migration rates, with the sand composition and environmental conditions [14,15].…”

Section: Introductionmentioning

confidence: 99%

The GNU Image Manipulation Program Applied to Study the Sand Dunes

Sparavigna¹

2013

ijSciences

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Abstract:The study of sand dunes and their migration rates requires large length and time scales. Therefore, the use of time series of satellite images turns out to be important because it allows remote measure and control of the dunes. To obtain information from the satellite images we can use GIMP, the GNU Image Manipulation Program, which is freely available on the Web. Here we discuss some of its features and how they can be applied to study the sand dunes.

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Deviations from self-similarity in barchan form and flux: The case of the Salton Sea dunes, California

Pelletier

2013

J. Geophys. Res. Earth Surf.

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[1] Barchans are the type of aeolian dune associated with a relatively uniform wind direction, incomplete sand coverage of the substrate, and low vegetation cover. Here I present an analysis of the morphology and migration rates of 40 dunes in the Salton Sea dune field using historical aerial orthophotographs, airborne laser swath mapping, terrestrial laser scanning, and measurements of the aerodynamic roughness length derived from wind velocity profiles. The data demonstrate that the Salton Sea dunes deviate from self-similarity such that smaller dunes have a lower ratio of slip face height to crest height and a lower slope, on average, compared with larger dunes and that smaller dunes migrate more slowly than would be predicted based on an inverse relationship between migration rate and dune height. The lack of self-similarity in barchans has been attributed to the dependence of speed-up ratios on dune size and the presence of a finite saturation length in the physics of aeolian transport. Here I argue that deviations from self-similarity at this study site are more likely due to the systematic decrease in aerodynamic roughness length with increasing elevation on stoss slopes. The data set I developed should prove useful to the aeolian geomorphic community for the further testing of models for barchan evolution.

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The shape of the barchan dunes of Southern Morocco

Cited by 152 publications

References 9 publications

The shape of barchan dunes

The shape of barchan dunes

The GNU Image Manipulation Program Applied to Study the Sand Dunes

Deviations from self-similarity in barchan form and flux: The case of the Salton Sea dunes, California

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