Macroscopic Flow Disequilibrium Over Aeolian Dune Fields
Macroscopic Flow Disequilibrium Over Aeolian Dune Fields
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DOI：
10.1029/2020gl088773
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发表时间：
2020-09-28
影响因子：
5.2
通讯作者：
Jerolmack, D. J.
中科院分区：
文献类型：
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作者：
Gunn, A.;Schmutz, P.;Jerolmack, D. J.
风成沙丘场是由风沙形成的自组织格局。沙丘是地形上的粗糙元素，对大气边界层（ABL）施加阻力，创造了形式和流动之间的自然耦合。虽然阻力对ABL的稳态影响已经得到了很好的研究，但由于粗糙度转变引起的非平衡效应却鲜为人知。在这里，我们研究了ABL与整个沙丘场之间的大尺度耦合。在美国新墨西哥州白沙地区的野外观测表明，顺风沙丘场边缘从光滑的playa向粗糙的沙丘转变的顺风风速和沙通量下降，影响了整个类似于10公里长的沙丘场。使用解释观测结果的系统理论，我们将其推广到其他粗糙场景。研究发现，通过过渡性ABL动力学，沙丘场内外粗糙度对风沙沉积均有影响。
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 similar to 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.