Results 171 to 180 of about 590 (205)
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Journal of Arid Environments, 1993
Abstract Sand dunes represent the most significant landform on the surface of Qatar Peninsula. In this study: field survey and laboratory work were undertaken; topographic maps, aerial photographs and satellite images were interpreted, to describe Qatar dunes both qualitatively and quantitatively.
N.S. Embabi, M.M. Ashour
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Abstract Sand dunes represent the most significant landform on the surface of Qatar Peninsula. In this study: field survey and laboratory work were undertaken; topographic maps, aerial photographs and satellite images were interpreted, to describe Qatar dunes both qualitatively and quantitatively.
N.S. Embabi, M.M. Ashour
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The shape of the barchan dunes of Southern Morocco
Geomorphology, 2000We present detailed shape measurements of several barchan dunes in southern Morocco, near Laâyoune. Using these data, we disprove the concept of shape invariance of barchan dunes of different sizes. Nevertheless, some parts of the barchan dune scale and we try to distinguish these from non-scaling ones.
P Rognon, H J Herrmann
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Relevant Length Scale of Barchan Dunes
Physical Review Letters, 2002A new experiment can create small scale barchan dunes under water: some sand is put on a tray moving periodically and asymmetrically in a water tank, and barchans rapidly form. We measure basic morphological and dynamical properties of these dunes and compare them to field data. These favorable results demonstrate experimentally the relevance of the so-
Hersen, Pascal +2 more
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Bidirectional winds, barchan dune asymmetry and formation of seif dunes from barchans: a discussion
Environmental Earth Sciences, 2016Barchan dunes—which have a crescent shape with two horns pointing downwind—may undergo a transition to a longitudinal (seif) dune under a bimodal wind regime. Understanding the barchan–seif dune transition is important for the research of dune field evolution and for the investigation of planetary climate and wind regimes. Two models have been proposed
Haim Tsoar, Eric J. R. Parteli
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Simulating study on barchan dune
Chinese Geographical Science, 1998Barchan dune is one of the basic forms of eolian landform, it is usually moulded by high-concentration non-saturated wind-sand flow. The formation process of barchan dune begins from “wave-grain duality” of wind-sand movement, and goes through two developmental stages of sand material accumulating (high-concertration saturated wind-sand flow) and dune ...
Yuquan Ling +3 more
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1973
IN the preceding chapter we examined the longitudinal cross- section, cut parallel to a uni-directional wind, of an imaginary transverse dune whose length was so great that the end-effects could be neglected. We saw that as this cross-section grows bigger there comes a time when the initial rounded shape is no longer stable; the top advances faster ...
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IN the preceding chapter we examined the longitudinal cross- section, cut parallel to a uni-directional wind, of an imaginary transverse dune whose length was so great that the end-effects could be neglected. We saw that as this cross-section grows bigger there comes a time when the initial rounded shape is no longer stable; the top advances faster ...
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Equilibrium versus disequilibrium of barchan dunes
Geomorphology, 2011Abstract Barchans are crescentic dunes which occur in mainly mono-directional winds. Shape, aspect ratios and velocities of these dunes have been studied as if they were in equilibrium. However, following a study of the shape and migration of 11 barchans of different sizes for 18 months in the field on Moroccan Atlantic Sahara, we show that they only
Hicham El belrhiti, Stéphane Douady
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The ecology of Qatari barchan dunes
Qatar Foundation Annual Research Forum Volume 2013 Issue 1, 2013The mobile Barchan dunes in Qatar are restricted to the southeastern region of the country. They are currently a disappearing natural habitat, due to the northwesterly Al Shamal winds which are scouring the landscape and spreading desertification as they pass. The study's aim was to understand the ecology of an active dune, in terms of resident species
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Modeling the bistability of barchan and parabolic dunes
Aeolian Research, 2018Abstract Extensive areas in arid and semi-arid regions of the world are covered by sand dunes. Sand dunes can be active, semi-active, or stable, depending on, among other factors, their vegetation and biogenic crust covers. Vegetation growth on barchan dunes can induce a transformation to parabolic dunes with long trailing arms pointed upwind.
Gershon Hanoch +2 more
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Grain-size variations on a longitudinal dune and a barchan dune
Sedimentary Geology, 1986Abstract The grain-size characteristics of the sand upon two dunes—a 40 m high longitudinal dune in the central Namib Desert and a 6.0 m high barchan in the Jafurah sand sea of Saudi Arabia—vary with position on the dunes. On the longitudinal dune, median grain size decreases, sorting improves and the grain-size distributions are less skewed and more
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