Saturation transients in saltation and their implications on dune shapes

We present a model for dune formation that takes saturation transients in the saltation layer into account. We show that these transients introduce a characteristic length scale that is crucial for dune formation and the macroscopic shape of dunes, albeit determined by intrinsic properties of the saltation kinetics. Finally, we demonstrate that our model can explain the scale dependence of the shape of barchan dunes revealed in recent field measurements.