Measuring a transverse dune field in the Lençóis Maranhenses

In this work, we present measurements of the height profile, wind velocity and sand flux performed on transverse dunes in the dune field known as “Lençóis Maranhenses”, northeastern Brazil. From the measured profile, we selected one dune to measure the air shear stress and the sand flux and compared the results with the theoretical predictions from a dune model in two dimensions recently introduced. We find that the numerical results give a reasonable fit to the field data. Our measurements show that transverse dunes with approximately the same height present a variable brink position relative to the crest, as opposed to the case of barchan dunes. The model is used to simulate transverse dune fields in two dimensions from a flat sand bed with small oscillations, using a phenomenological definition for the separation streamlines at the lee side of the dune. We found that our model is able to reproduce transverse dune fields with similar inter-dune distances and dune aspect ratios as in the measured field.