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 ...

Introduction: Sand dunes in Earth’s large deserts are similar in size and relationship to substrate and topography to the tens of thousands of dunes seen on the surface of Titan by Cassini. Field studies of large dunes can thus inform our understanding of the evolution of similar dunes on Titan. A recent field study to the Namib Sand Sea yielded valuable results concerning the morphology, inter...

Barchans are crescentic dunes propagating on a solid ground. They form dune fields in the shape of elongated corridors in which the size and spacing between dunes are rather well selected. We show that even very realistic models for solitary dunes do not reproduce these corridors. Instead, two instabilities take place. First, barchans receive a sand flux at their back proportional to their widt...

Aeolian desert sand dunes birth from wind flow and sand bed interactions: depending on wind properties and sand availability, they can adopt several different shapes from huge motionless star dunes to small and fast mobile barchan dunes. These latter have a characteristic crescentic shape and form on hard ground with low sand supply under a monodirectional wind . Here, a 3d barchan model based ...

The rate of movement for 3and 10-cm-high granule ripples was documented in September of 2006 at Great Sand Dunes National Park and Preserve during a particularly strong wind event. Impact creep induced by saltating sand caused 24 granules min 1 to cross each cm of crest length during wind that averaged 9 m s 1 (at a height well above 1 m), which is substantially larger than the threshold for sa...

Thirty-four grass species were collected for phytolith analysis from a variety of coastal environments in the southeastern USA (Georgia, Florida, and Louisiana), including salt marshes, freshwater/brackish marshes, pine/oak forests, maritime hardwood forests, and sand dunes. Phytoliths produced by these modern grasses include a large diversity of shapes and types. We propose a preliminary relat...

Understanding the situation, behavior and the nature of sand dunes and also their location, transport and deposition are very important. On the other hand, the importance of sand dunes is due to the impacts that they have on water and soil resources, flora and fauna and human infrastructure. This study, looks at the development patterns of sand dunes in Mesr erg region. In the first part, data ...

Despite radically different environmental conditions, terrestrial and martian dunes bear a strong resemblance, indicating that the basic processes of saltation and grainfall (sand avalanching down the dune slipface) operate on both worlds. Here, we show that martian dunes are subject to an additional modification process not found on Earth: springtime sublimation of Mars' CO(2) seasonal polar c...

We propose a minimal model for aeolian sand dunes. It combines an analytical description of the turbulent wind velocity field above the dune with a continuum saltation model that allows for saturation transients in the sand flux. The model provides a qualitative understanding of important features of real dunes, such as their longitudinal shape and aspect ratio, the formation of a slip face, th...