Physical processes represented by the Monin–Obukhov bulk formula for momentum are investigated with field observations. We discuss important differences between turbulent mixing by the most energetic non-local, large, coherent turbulence eddies and local turbulent mixing as traditionally represented by K-theory (analog to molecular diffusion), especially in consideration of developing surface-layer stratification. The study indicates that the neutral state in a horizontally homogeneous surface layer described in the Monin–Obukhov bulk formula represents a special neutrality regardless of wind speed, for example, the surface layer with no surface heating/cooling. Under this situation, the Monin–Obukhov bulk formula agrees well with observations for heights to at least 30 m. As the surface layer is stratified, stably or unstably, the neutral state is achieved by mechanically generated turbulent mixing through the most energetic non-local coherent eddies. The observed neutral relationship between u∗\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$u_*$$\end{document} (the square root of the momentum flux magnitude) and wind speed V at any height is different from that described by the Monin–Obukhov formula except within several metres of the surface. The deviation of the Monin–Obukhov neutral u∗-V\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$u_*-V$$\end{document} linear relation from the observed one increases with height and contributes to the deteriorating performance of the bulk formula with increasing height, which cannot be compensated by stability functions. Based on these analyses, estimation of drag coefficients is discussed as well.

中文翻译：

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了解由 Monin-Obukhov 动量传递公式表示的物理过程

用实地观察研究了由 Monin-Obukhov 动量公式表示的物理过程。我们讨论了由能量最高的非局部、大、相干湍流涡旋产生的湍流混合与传统上由 K 理论（类似于分子扩散）表示的局部湍流混合之间的重要区别，特别是考虑到表层分层的发展。研究表明，Monin-Obukhov 体积公式中描述的水平均质表面层中的中性状态代表一种特殊的中性，无论风速如何，例如，表面层没有加热/冷却。在这种情况下，Monin-Obukhov 体积公式与至少 30 m 的高度观测值非常吻合。由于表层分层，稳定或不稳定，中性状态是通过机械产生的湍流混合通过最具活力的非局部相干涡流来实现的。u∗\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} 之间观察到的中性关系\setlength{\oddsidemargin}{-69pt} \begin{document}$$u_*$$\end{document}（动量通量大小的平方根）和风速 V 在任何高度都不同于莫宁-奥布霍夫公式，除了表面几米内。Monin–Obukhov 中性的偏差 u∗-V\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$u_*-V$$\end{document} 与观察到的线性关系随着高度的增加而增加，并导致性能恶化体积公式随着高度的增加而无法通过稳定性函数进行补偿。基于这些分析，还讨论了阻力系数的估计。