Wind Profile Parameters of Various Canopies as Influenced by Wind Velocity and Stability
Wind Profile Parameters of Various Canopies as Influenced by Wind Velocity and Stability
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风速和稳定性对各种檐篷风廓线参数的影响
DOI：
10.2480/agrmet.31.61
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发表时间：
1975
影响因子：
1.3
通讯作者：
T. Maki
中科院分区：
文献类型：
--
作者：
T. Maki
作者通过实验研究了空气动力特性对各种座舱盖表面粗糙度的依赖关系，以验证在以前的论文（Maki，1975）中提出的一个新方程。该关系表示如下：lnh-d/z 0 =（κκ2/c）h-d/z 0（1），式中h为平均株高，d为零平面位移，z 0为空气动力学粗糙度，κ为卡门常数，c为作者获得的经验常数。本文利用玉米冠层上方风速廓线资料，研究了玉米冠层空气动力学特性随生长的变化。z 0随摩擦速度（u*）的增大而增大，d随玉米冠层和玻璃杆模型冠层的增大而增大。由方程（1）得到的d与z 0的关系，c为0.47，结果表明，人工粗糙度元素的d和z 0值随表面积密度（SAD）的增大而增大，的元素增加。对角排列类型（D）获得的z 0值大于正方形排列类型（S）获得的z 0值。在SAD观测范围内，D型的d值随SAD的增加而增加，而S型的d值几乎不变，有效株高（He）与平均株高（h）的比值随总表面积密度（TSAD）的增加而增大，在TSAD最大值处，He/h趋于1. 0。发现将d和z 0与粗糙度元素的高度关联的方程对于SAD为0.05cm ~ 2/cm ~ 3或更高的表面是有效的。为了使方程对稀疏种植的表面有效，应引入随SAD减小的有效植物高度。该方程可应用于中等稳定和不稳定条件下的情况，因为方程（3）仅对这些条件有效。然而，这还有待于在观察性研究中进行检验。
The author experimentally studied the dependence of aerodynamic characteristics on the surface roughness of various canopies to verify a new equation proposed in a previous paper (Maki, 1975). The relation is expressed as follows:lnh-d/z0=(κκ2/c)h-d/z0 (1), where h is mean plant height, d zero-plane displacement, z0 aerodynamic roughness length, κ von Karman's constant and c an empirical constant obtained by the author.Changes of aerodynamic characteristics of a teosinte canopy with growth were investigated by use of the data of wind velocity profiles above the canopy.The magnitude of z0 increased with friction velocity (u*) and the reverse was the case for d of a teosinte canopy and glass rod model canopies.The relation between d and z0 obtained from equation (1) with a value of c, 0.47, was found to be in good agreement with experimental values of d and zo on various plant canopies.The d and z0 values of artificial roughness elements increased generally as the surface area density (SAD) of the elements increased. The values of z0 obtained for a diagonal arrangement type (D) were larger than those for a square arrangement type (S). The d value increased appreciably with SAD in the case of D type, but for S type it was almost constant in the observed region of SAD.The ratio of the effective plant height (He) to the mean plant height (h) increased with increment of the total surface area density (TSAD) asymptotically to 1.0 at the highest range of TSAD. The equation that relates d and z0 to the height of roughness elements was found to be valid for a surface of them with SAD of 0.05cm2/cm3 or above. In order for the equation to be valid for a sparsely planted surface, an effective plant height which decreases with SAD should be introduced.Equation (11) was deduced to take into account the stability correction on the relation as indicated by equation (1). This equation could be applied to cases under moderately stable and unstable conditions, because equation (3) is valid only for these conditions. However, it is yet to be checked in observational studies.