Dune Initiation in a Bimodal Wind Regime
Dune Initiation in a Bimodal Wind Regime
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DOI：
10.1029/2020jf005757
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发表时间：
2020-11-01
影响因子：
3.9
通讯作者：
Valdez, Andrew
中科院分区：
文献类型：
--
作者：
Delorme, Pauline;Wiggs, Giles F. S.;Valdez, Andrew
早期的底形通过风、沙输送和表面地形之间复杂的相互作用发展成成熟的沙丘。根据不同的环境和风力条件，驱动沙丘形成的机制，并最终，新生沙丘的形状可能会显着不同。在沙量充足的情况下，沙丘的出现和生长可以用耦合的输运和水动力方程的线性稳定性分析来研究。到目前为止，这种分析只应用于单向风的现场证据。然而，在世界上的许多地区和其他星球上，风况往往是双峰或多峰的。在这里，我们调查现场证据的原型沙丘形成下的双峰风制度，通过应用线性稳定性分析，发展中的原型沙丘领域。利用线性稳定性理论和实验研究的最新进展，结合在美国科罗拉多大沙丘国家公园为期一个月的野外考察中的现场风、泥沙输运和地形测量，我们预测了原沙丘场的空间特征（方向和波长）和时间演化（生长速率和迁移速度）。我们发现，理论预测比较以及测量沙丘属性的特点是高分辨率数字高程模型测量重复地面激光扫描。我们的研究结果表明，线性稳定性分析是一个定量的预测原型沙丘发展的桑迪表面的双峰风制度。这一结果是重要的，因为它提供了重要的线性稳定性分析的验证，解释的启动和发展的沙丘走向成熟，在一个复杂的自然环境。
Early-stage bedforms develop into mature dunes through complex interactions between wind, sand transport, and surface topography. Depending on varying environmental and wind conditions, the mechanisms driving dune formation and, ultimately, the shape of nascent dunes may differ markedly. In cases where sand availability is plentiful, the emergence and growth of dunes can be studied with a linear stability analysis of coupled transport and hydrodynamic equations. Until now, this analysis has only been applied using field evidence in unidirectional winds. However, in many areas of the world and on other planets, wind regimes are more often bimodal or multimodal. Here, we investigate field evidence of protodune formation under a bimodal wind regime by applying linear stability analysis to a developing protodune field. Employing recent development of the linear stability theory and experimental research, combined with in situ wind, sediment transport, and topographic measurements during a monthlong field campaign at Great Sand Dunes National Park, Colorado, USA, we predict the spatial characteristics (orientation and wavelength) and temporal evolution (growth rate and migration velocity) of a protodune field. We find that the theoretical predictions compare well with measured dunefield attributes as characterized by high-resolution Digital Elevation Models measured using repeat terrestrial laser scanning. Our findings suggest that linear stability analysis is a quantitative predictor of protodune development on sandy surfaces with a bimodal wind regime. This result is significant as it offers critical validation of the linear stability analysis for explaining the initiation and development of dunes toward maturity in a complex natural environment.