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• 基金项目：

• 陈家宜
• 北京大学地球物理系

• 摘要：水平和垂直风向的标准差是划分大气扩散类型的有效参数.本文提出了一种合理估算σ_θ和σ_?的参数化方法.在分析中无因次湍流速度的标准差σ_v/u_*和σ_w/u_*按近年来边界层大气湍流研究所得到的规律确定,无因次风速u/u_*依高度的高低分别接近地面层的风速廓线规律和幂次律推论.结果表明σ_θ和σ_φ同时依赖于大气稳定度类型、边界层厚度、地面粗糙度和高度.在实用中地面粗糙度可按常规经验确定,大气边界层的稳定度性质和L可按P-T稳定度分类推论,但是边界层高度必须通过与温度廓线有关的信息确定.

• Abstract：Outlined here is a simplified parameterization technique to estimate standard deviation of the horizontal and vertical wind direction fluctuations, σ_θ and σ_ψ, in lower atmosphere, which have been known as more suitable indice for dispersion classification. In this approach, the nondimensional turbulent velocity fluctuations σ_γ and σ_w are formulated in terms of atmospheric boundary layer scaling, based on reported data in recent decade in the study of whole depth boundary layer. The nondimensional wind velocity u/u* is determined by using flux-profile relationships and power law respectively in surface-stress layer and outer layer.It has been shown that σ_θ and σ_ψ are dependent on parameter set of height, roughness, length of surface, and stability and depth of ABL. As a res.ult, diffusion categories can not be obtained with confidence ifonly individual parameter among them is used for determination of σ_θ and σ_ψ. Under unstable conditions, a notable result is the variation ofσ_ψ with height, which turns out to be distinctly different from that of σ_θ. Simply estimation of σ_ψ with σ_θ a appears to be in substantial error.Figures and nomograms for σ_θ and σ_ψ are presented for typical conditions of surface roughness, depth of ABL and stability of lower layer, which as ordinarily determined in Pasquill-Turner's method. Suggestions are made towards practical application of these results in interpretation of field data. The results are likely to be useful for adapting typing scheme of σ_v and σ_z.

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