Modeling of aeolian dunefields [a.6,t.1]

We employ discrete models to recreate aeolian dunefield morphologies. The basic model incorporates two mechanisms: sand transport, induced by wind, and gravitational shaping (avalanching). By incorporating these features we are able to model dunes whose individual shape and collective patterns are similar to those observed in nature. The main parameters that control the different morphologies are the sand availability (how much sand there is in our modeling basin) and the wind direction variability. For example, unidirectional wind tends to form transverse dunes or barchan dunes while more complex wind patterns could form star dunes and network dunes. An important inclusion to the model is a nonlinear shear-velocity-increase. The shear-velocity corresponds to the velocity dependence of the wind as it is accelerated (decelerated) over the windward (leeward) slope of a dune. The addition of a nonlinear term on the shear-velocity is necessary to reduce dune growth, resulting in an equilibrium dune field configuration.