Surface length scales and shear stress: Implications for land-atmosphere interaction over complex terrain
Surface length scales and shear stress: Implications for land-atmosphere interaction over complex terrain
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DOI：
10.1029/1999wr900094
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发表时间：
1999-07-01
影响因子：
5.4
通讯作者：
Parlange, MB
中科院分区：
文献类型：
--
作者：
Albertson, JD;Parlange, MB
大气边界层（ABL）的大涡模拟（LES）代码已被开发并应用于研究空间变化的表面特性对陆地-大气界面处的面积平均表面剪切应力的影响。 LES 代码模拟了 ABL 中大尺度湍流涡旋的空间和时间演化及其输运效应。我们在此报告空间可变粗糙度场上的流动模拟。模拟动力学，并对所得时空场进行平均，以探索表面变异长度尺度对平均表面剪切应力的影响，如在大规模模型中用于估计标量通量（例如蒸发）。我们观察到平滑到粗糙和粗糙到平滑过渡的不对称响应，使得过渡的效果累积而不是抵消。研究表明，表面粗糙度的突然变化以及大气对这些斑块的响应，导致表面剪切应力的统计结构对表面斑块长度尺度的显着依赖性。发现随着水平斑块长度尺度的减小，区域平均表面应力增加。
A large eddy simulation (LES) code of the atmospheric boundary layer (ABL) has been developed and applied to study the effect of spatially variable surface properties on the areally averaged surface shear stress at the land-atmosphere interface. The LES code simulates the space and time evolution of the large-scale turbulent eddies and their transport effects in the ABL. We report here on simulations of flow over spatially variable roughness fields. The dynamics are simulated, and the resulting space-time fields are averaged to explore the effects of the surface variability length scales on the average surface shear stress, as used in large-scale models to estimate scalar fluxes, such as evaporation. We observe asymmetrical response of the smooth-to-rough and rough-to-smooth transitions, such that the effects of the transitions accumulate rather than cancel. It is shown that the presence of abrupt changes in surface roughness and the atmosphere's response to these patches create a marked dependence of the statistical structure of surface shear stress on the length scale of the surface patches. An increase in regionally averaged surface stress for decreasing horizontal patch length scale is found.