Earth Sciences and Image Analysis Laboratory, NASA Johnson Space Center (http://eol.jsc.nasa.gov)[]{data-label="fig:transv_photo"}](Figure1.eps){width="80.00000%"}

An example of a field of transverse dunes in China is shown in Figure \[fig:transv\_photo\]. Normally transverse dunes have more irregular patterns and even smaller hierarchies of smaller transverse dunes can be found in a field of big transverse dunes. Strong winds coming essentially from the same direction are the main environment where this type of dune can be found. proposed that in highly mobile environments cross winds distort the dune shape.

![Two dimensional cut through a single transverse dune profile $h(x)$ (solid line) and the sand flux $q(x)$ (dashed line) over it. The wind is coming from the left.[]{data-label="fig:transv_single"}](Figure2.eps){width="80.00000%"}

In Figure \[fig:transv\_single\] a dune of a height of about $27$ m is depicted which is part of a two dimensional calculation of our model. This dune is situated between other similar dunes which together result in a simulation of a dune field of a length of four kilometers. The dashed curve shows the sand flux which is set to zero at the slip face where the shear stress is not strong enough to entrain sand. This occurs in the region of flow separation, defining the boundary between quasi-laminar 