Aeolian Geomorphology and its Simulation – Aeolian Sand Dunes

Abstract

No matter from the viewpoint of occupied area or from the complexity of dynamical behavior, sand dunes and sand dune fields are the most significant manifestation of aeolian geomorphology system. Small-scale sand ripples can not grow into large-scale sand dunes, and sand dunes have distinct characteristics compared with sand ripples. The spatial and temporal scale in the formation and evolution of a sand dune is much larger than that of a sand ripple, and field observation and simulation on sand dunes are more difficult than on sand ripples. For example, the fundamental task in simulating the formation and evolution of dune field is to solve the trans-scale problem, that is, the transition from the small scale physical processes (such as the transport of sand particles) to the large scale physical processes (such as the formation and evolution of dune fields). Obviously, such trans-scale transition is not a simple linear superposition. In other words, it is impossible to characterize the formation and evolution of a dune field by modeling the process of every sand particle, which brings an infinite number of degrees of freedom into the modeling. Apart from capability limitation of present computers, the characteristics and physical mechanism of the formation and evolution of dune field are inherently different from those for sand movement and sand ripples. However, the dynamical behaviors of large-scale dune fields are definitely related with sand movement. Therefore, ignorance or complete parameterization of sand movement would possibly cause mis-reflecting the real formation and evolution physical process of dune field.