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首页> 外文期刊>Nonlinear processes in geophysics >Universal dependences between turbulent and mean flow parameters in stably and neutrally stratified Planetary Boundary Layers
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Universal dependences between turbulent and mean flow parameters in stably and neutrally stratified Planetary Boundary Layers

机译：稳定和中性分层行星边界层中湍流和平均流量参数之间的通用相关性

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We consider the resistance law for the planetary boundary layer (PBL) from the point of view of the similarity theory. In other words, we select the set of the PBL governing parameters and search for an optimal way to express through these parameters the geostrophic drag coefficient C-g=u(*)/U-g and the cross isobaric angle et(where u(*) is the friction velocity and U-g is the geostrophic wind speed). By this example, we demonstrate how to determine the "parameter space" in the most convenient way, so that make independent the dimensionless numbers representing co-ordinates in the parameter space, and to avoid (or at least minimise) artificial self-correlations caused by the appearance of the same factors (such as u(*)) in the examined dimensionless combinations (e.g. in C-g=u(*)/U-g) and in dimensionless numbers composed of the governing parameters. We also discuss the "completeness" of the parameter space from the point of view of large-eddy simulation (LES) modeller creating a database for a specific physical problem. As recognised recently, very large scatter of data in prior empirical dependencies of C-g and alpha on the surface Rossby number Ro=U-g vertical bar fz(0)vertical bar(-1) (where z(0) is the roughness length) and the stratification characterised by mu was to a large extent caused by incompactness of the set of the governing parameters. The most important parameter overlooked in the traditional approach is the typical value of the Brunt-Vaisala frequency N in the free atmosphere (immediately above the PBL), which involves, besides Ro and mu, one more dimensionless number: mu(N)=N/vertical bar f vertical bar. Accordingly, we consider C-g and alpha as dependent on the three (rather then two) basic dimensionless numbers (including mu N) using LES database DATABASE64. By these means we determine the form of the dependencies under consideration in the part of the parameter space representing typical atmospheric PBLs, and provide analytical expressions for C-g and alpha.
机译：我们从相似性理论的角度考虑了行星边界层（PBL）的阻力定律。换句话说，我们选择一组PBL控制参数，并寻求一种最佳方式来通过这些参数来表达地转阻力系数Cg = u（*）/ Ug和等压交叉角e​​t（其中u（*）是摩擦速度，Ug是地转风速）。通过此示例，我们演示了如何以最方便的方式确定“参数空间”，从而使代表参数空间中坐标的无量纲数字独立，并避免（或至少最小化）人为的自相关通过在检查的无量纲组合（例如，Cg = u（*）/ Ug）和由控制参数组成的无量纲数中出现相同的因子（例如u（*））来实现。我们还将从大型涡流仿真（LES）建模人员为特定物理问题创建数据库的角度讨论参数空间的“完整性”。正如最近所认识到的那样，表面上Cg和alpha的先前经验依赖性中的数据散布非常大。Rossby数Ro = Ug垂直线fz（0）垂直线（-1）（其中z（0）是粗糙度长度），并且以mu为特征的分层很大程度上是由控制参数集的不精确性引起的。传统方法中被忽略的最重要参数是自由大气中（紧邻PBL之上）的Brunt-Vaisala频率N的典型值，除了Ro和mu之外，它还涉及另一个无因次数：mu（N）= N /竖线f竖线。因此，我们使用LES数据库DATABASE64将C-g和alpha依赖于三个（而不是两个）基本无量纲数（包括mu N）。通过这些方法，我们可以确定代表典型大气PBL的参数空间部分中所考虑的依赖项的形式，并提供C-g和alpha的解析表达式。

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