Nocturnal wind‐directional shear in complex terrain
Nocturnal wind‐directional shear in complex terrain
复制标题
复杂地形夜间风向切变
DOI：
10.1002/qj.2369
复制
发表时间：
2014
影响因子：
8.9
通讯作者：
N. Seaman
中科院分区：
文献类型：
--
作者：
L. Mahrt;S. Richardson;D. Stauffer;N. Seaman
在弱风的夜间边界层中，近地面的风向可能会随高度而变化。定向剪切是由瞬态模式和浅层地形引起的运动引起的。本研究探讨了大的定向剪切夜间数据收集在最低的10米，从三个现场程序。在两个宽谷高侧壁的定向剪切是由瞬态运动的山谷冷池。相比之下，浅窄山谷内的定向剪切主要由地形引起的山谷下排水流控制，尽管山谷侧壁的大小和高度比其他两个山谷小得多。总矢量切变的方向剪切的相对贡献被检查作为风速和稳定性的函数。
In the weak‐wind nocturnal boundary layer, the wind direction near the surface may vary substantially with height. The directional shear is caused by transient modes and shallow, terrain‐induced motions. This study examines the large directional shear for nocturnal data collected in the lowest 10 m from three field programs. The directional shear in two broad valleys with high sidewalls is dominated by transient motions within the valley cold pool. In contrast, the directional shear within a shallow narrow valley is dominated by terrain‐induced down‐valley drainage flows, in spite of the fact that the magnitude and height of the valley sidewalls are much smaller than the other two valleys. The relative contribution of the directional shear to the total vector shear is examined as a function of wind speed and stability.