Macroscopic flow disequilibrium over aeolian dune fields

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Authors

Andrew Gunn , Phillip Schmutz, Matt Wanker, Doug Edmonds , Ryan Ewing, Douglas Jerolmack

Abstract

Aeolian dune fields are self-organized patterns formed by wind-blown sand. Dunes are topographic roughness elements that impose drag on the atmospheric boundary layer (ABL), creating a natural coupling between form and flow. While the steady-state influence of drag on the ABL is well studied, non-equilibrium effects due to roughness transitions are less understood. Here we examine the large-scale coupling between the ABL and an entire dune field. Field observations at White Sands, New Mexico, reveal a concomitant decline in wind speed and sand flux downwind of the transition from smooth playa to rough dunes at the upwind dune-field margin, that affects the entire ∼10-km long dune field. Using a simple theory for the system that accounts for the observations, we generalize to other roughness scenarios. We find that, via transitional ABL dynamics, aeolian sediment aggradation can be influenced by roughness both inside and outside dune fields.

DOI

https://doi.org/10.31223/osf.io/s32vc

Subjects

Atmospheric Sciences, Earth Sciences, Geomorphology, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics, Sedimentology

Keywords

sediment transport, geomorphology, Aeolian, Atmospheric Boundary Layer, Dunes, Land-Atmosphere

Dates

Published: 2020-05-08 17:32

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License

GNU Lesser General Public License (LGPL) 2.1

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