Numerical Models - Dune Worlds: How Windblown Sand Shapes Planetary Landscapes - page 237

Fig. 19.10 Different barchan
forms on Mars are compared with
those in tank experiments (see
Sect. 17.4 ) and from numerical
simulations. The agreement is
striking. Image courtesy of
Erwan Reffet

address the quantitative relationships that remote sensing
data provide on the arrangement of different dunes in dif-
ferent settings. Some heuristic models have been applied to
explain trends across a dune field (e.g., Jerolmack et al.
2012) although whether such approaches have predictive,
rather than explanatory, utility remains to be seen. (This
model discusses the variation of dune morphology across
the White Sands dunefield in the context of a thickening
boundary layer, although perhaps this may be simply
another way of looking at the hierarchical roughness dis-
cussed

modeling of dune morphology and evolution by the tech-
niques described in the previous section has received much
attention recently and has made substantial progress in
reproducing much of what is observed in a wide range of
settings.
One factor at work is the balance of sand fluxes on a
barchan. As sand saltates across (with presumably a uni-
form rate across the field), then a large barchan with a larger
width will intercept more sand than a small one. However,
barchans 'leak' sand through their arms, and this leakage is
more significant for small barchans. So, left to themselves, by Pelletier (2009)—see later). The forward-