Local Wind Regime Induced by Giant Linear Dunes: Comparison of ERA5-Land Reanalysis with Surface Measurements
Local Wind Regime Induced by Giant Linear Dunes: Comparison of ERA5-Land Reanalysis with Surface Measurements
复制标题
DOI：
10.1007/s10546-022-00733-6
复制
发表时间：
2022-08
影响因子：
4.3
通讯作者：
C. Gadal;P. Delorme;C. Narteau;G. Wiggs;M. Baddock;J. Nield;P. Claudin
中科院分区：
文献类型：
--
作者：
C. Gadal;P. Delorme;C. Narteau;G. Wiggs;M. Baddock;J. Nield;P. Claudin
沙丘的形成和发育是地形、风、沙相互作用的结果。虽然这些变量之间的反馈在一个单一的和相对较小的沙丘的规模进行了很好的研究，一个周期性的大规模沙丘模式对大气流动的平均影响仍然受到很大的限制，由于迫切缺乏数据在主要沙海。在这里，我们比较当地的地面风的ERA 5-土地气候再分析的预测在纳米比亚的四个地点，无论是内部和外部的纳米布沙海的巨大的线性沙丘领域。在沙海以北的沙漠平原上，观测和预测吻合得很好。白天沙海沙丘间地区也是如此。然而，在夜间，一个额外的风分量与巨大的沙丘方向一致的测量，与ERA 5-土地再分析预测的东风相反。对于给定的沙丘方向和测得的风制度，我们将观察到的风偏差（过）的湍流大气边界层的日常循环。在夜间，一个浅的边界层诱导流动限制在巨大的沙丘，导致大的流动偏差，特别是对较慢的东风。在白天，由于边界层较厚，风速较高，巨型沙丘对大气流动的反馈要弱得多。最后，我们建议，约束机制和相关的风偏转引起的巨型沙丘可以解释较小规模的次级沙丘，它在沙丘间地区的主要沙丘模式的倾斜伸长的发展。
Emergence and growth of sand dunes results from the dynamic interaction between topography, wind flow and sediment transport. While feedbacks between these variables are well studied at the scale of a single and relatively small dune, the average effect of a periodic large-scale dune pattern on atmospheric flows remains poorly constrained, due to a pressing lack of data in major sand seas. Here, we compare local measurements of surface winds to the predictions of the ERA5-Land climate reanalysis at four locations in Namibia, both within and outside the giant linear dune field of the Namib Sand Sea. In the desert plains to the north of the sand sea, observations and predictions agree well. This is also the case in the interdune areas of the sand sea during the day. During the night, however, an additional wind component aligned with the giant dune orientation is measured, in contrast to the easterly wind predicted by the ERA5-Land reanalysis. For the given dune orientation and measured wind regime, we link the observed wind deviation (over) to the daily cycle of the turbulent atmospheric boundary layer. During the night, a shallow boundary layer induces a flow confinement above the giant dunes, resulting in large flow deviations, especially for the slower easterly winds. During the day, the feedback of the giant dunes on the atmospheric flow is much weaker due to the thicker boundary layer and higher wind speeds. Finally, we propose that the confinement mechanism and the associated wind deflections induced by giant dunes could explain the development of smaller-scale secondary dunes, which elongate obliquely in the interdune areas of the primary dune pattern.