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Macroscopic Flow Disequilibrium Over Aeolian Dune Fields
Author(s) -
Gunn A.,
Schmutz P.,
Wanker M.,
Edmonds D. A.,
Ewing R. C.,
Jerolmack D. J.
Publication year - 2020
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2020gl088773
Subject(s) - aeolian processes , geology , geomorphology , aggradation , drag , beach morphodynamics , surface finish , geophysics , sediment transport , sediment , mechanics , physics , fluvial , materials science , structural basin , composite material
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, nonequilibrium 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 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.