Fine‐scale modeling of the boundary layer wind field over steep topography
Fine‐scale modeling of the boundary layer wind field over steep topography
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DOI：
10.1029/2007wr006544
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发表时间：
2008-09
影响因子：
5.4
通讯作者：
N. Raderschall;M. Lehning;C. Schär
中科院分区：
文献类型：
--
作者：
N. Raderschall;M. Lehning;C. Schär
本文介绍了风场的适应陡峭和复杂的地形使用精细尺度数值模拟。这项工作的动机是需要高分辨率的流场来预测雪崩预警目的的雪输送和积雪发展。应用非静力和可压缩的大气预报模式高级区域预报系统（ARPS）陡峭的高山地形，边界层流模拟和评估对测量。模拟了特定初始和边界条件下风场对陡峭地形的适应性。我们研究中使用的地形长度为500米，典型高度为150米，最大坡度为45°。数值试验与理想化的三角形脊进行，以找到一个适当的模式配置。该分析表明，需要一个水平间距至少为25 m、近地表垂直间距为3 m的高分辨率网格来再现小尺度流动特征，如加速、分离和再循环。流动分离的发生对初始和边界条件、坡度角和表面粗糙度非常敏感。模式模拟结果与试验场实测结果的对比表明，模拟结果较好地再现了典型的风场特征。模拟的风场已被用于驱动数值三维雪堆模型，该模型在Lehning等人的配套论文中提出。（2008）。
This paper describes the adaptation of wind fields to steep and complex terrain using fine‐scale numerical modeling. The work is motivated by the need of high‐resolution flow fields to predict snow transport and snow cover development for avalanche warning purposes. Applying the nonhydrostatic and compressible atmospheric prediction model Advanced Regional Prediction System (ARPS) to steep alpine topography, the boundary layer flow was simulated and evaluated against measurements. The adaptation of the wind field to steep terrain for specific initial and boundary conditions was simulated. The topography used in our study has a length scale of 500 m, a typical height of 150 m, and maximum slopes of 45°. Numerical experiments with idealized triangular ridges were conducted to find an adequate model configuration. This analysis indicates that a high‐resolution grid with horizontal spacing of at least 25 m and vertical spacing of 3 m near the surface is necessary to reproduce small‐scale flow features such as speed‐up, separation, and recirculation. The onset of flow separation is highly sensitive to initial and boundary conditions, slope angle, and surface roughness. The results of the comparison between the model simulations and measurements on our experimental site show that typical wind field characteristics are well reproduced. The simulated wind fields have been used to drive a numerical three‐dimensional snow drift model, which is presented in a companion paper by Lehning et al. (2008).