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Nature 457, 1120-1123 (26 February 2009) | doi:10.1038/nature07787; Received 19 November 2007; Accepted 15 January 2009

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Giant aeolian dune size determined by the average depth of the atmospheric boundary layer

Bruno Andreotti1, Antoine Fourrière1, Fouzia Ould-Kaddour2, Brad Murray3 & Philippe Claudin1

  1. Laboratoire de Physique et Mécanique des Milieux Hétérogènes (PMMH UMR 7636 CNRS-ESPCI-P6-P7), 10 rue Vauquelin, 75005 Paris, France
  2. Laboratoire de Physique Théorique, Université Abou Bekr Belkaid, Tlemcen, Algeria
  3. Nicholas School of the Environment and Earth Sciences, Center for Nonlinear and Complex Systems, Duke University, Box 90230, Durham, North Carolina 27708-0230, USA

Correspondence to: Philippe Claudin1 Correspondence and requests for materials should be addressed to P.C. (Email: claudin@pmmh.espci.fr).

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Depending on the wind regime1, 2, sand dunes exhibit linear3, 4, crescent-shaped or star-like forms5 resulting from the interaction between dune morphology and sand transport6, 7, 8. Small-scale dunes form by destabilization of the sand bed9, 10, 11 with a wavelength (a few tens of metres) determined by the sand transport saturation length11, 12, 13. The mechanisms controlling the formation of giant dunes, and in particular accounting for their typical time and length scales, have remained unknown. Using a combination of field measurements and aerodynamic calculations, we show here that the growth of aeolian giant dunes, ascribed to the nonlinear interaction between small-scale superimposed dunes4, 10, 14, 15, is limited by the confinement of the flow within the atmospheric boundary layer16, 17. Aeolian giant dunes and river dunes form by similar processes, with the thermal inversion layer that caps the convective boundary layer in the atmosphere18 acting analogously to the water surface in rivers. In both cases, the bed topography excites surface waves on the interface that in turn modify the near-bed flow velocity. This mechanism is a stabilizing process that prevents the scale of the pattern from coarsening beyond the resonant condition. Our results can explain the mean spacing of aeolian giant dunes ranging from 300 m in coastal terrestrial deserts to 3.5 km. We propose that our findings could serve as a starting point for the modelling of long-term evolution of desert landscapes under specific wind regimes.