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arXiv 2007.08161physics.flu-dynphysics.geo-ph
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对流边界层近地层中的温度廓线、羽流和谱

Temperature profiles, plumes and spectra in the surface layer of convective boundary layers

Keith G. McNaughton, Subharthi Chowdhuri

发表信息：
AIP Advances (2020)
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摘要：

我们调查的温度模式和对流边界层（CBLs）的热传输的角度来看，这些是新兴的远离平衡，复杂的动力系统的属性。我们引入了一个双温（2 T）玩具模型来定义羽流的横截面积，并将温度梯度，温度变化和热传输的标度特性连接到这个区域。我们检查温度（$T$）的概率密度函数和$w$ - $T$联合概率密度函数，$T$光谱和$wT$ cospectrum内和表面摩擦层以上观察。这里$w$是垂直速度。在对$T$谱和$wT$余谱的讨论中，我们着重讨论了SFL上的羽流和通量事件的自相似性。我们解释的$T$光谱中的波数的混合长度尺度的$z^{1/2}$的依赖性，反映了羽流的横截面积，因此与$z^{-1/2}$形式的温度分布，其中$z$是观察高度。我们介绍了新的缩放结果$T$光谱和$wT$ cospectures从内表面摩擦层（SFL），从SLTEST实验的数据的基础上。我们证实了早期的结果表明，$T$光谱和$wT$ cospectures的缩放行为的变化低于$z/z_s<0.1$，其中$z_s$的高度的SFL的高度，并显示与随机扩散的属性。最后，我们对比我们的解释浮力的作用，作为一个系统范围内的行动，在CBL流与理查森，其想法通知目前的解释的统计流体力学模型的边界层流动。

英文摘要：

We survey temperature patterns and heat transport in convective boundary layers (CBLs) from the perspective that these are emergent properties of far-from-equilibrium, complex dynamical systems. We introduce a two-temperature (2T) toy model to define the cross-sectional areas of plumes, and connect the scaling properties of temperature gradients, temperature variance and heat transport to this area. We examine temperature ($T$) probability density functions and $w$-$T$ joint probability density functions, $T$ spectra and $wT$ cospectra observed both within and above the surface friction layer. Here $w$ is vertical velocity. In our discussion of $T$ spectra and $wT$ cospectra we focus on the self-similarity property of the plumes and flux events above the SFL. We interpret the $z^{1/2}$ dependence of the mixed length scale for wavenumbers in the $T$ spectra as reflecting the cross-sectional areas of the plumes, and so with the $z^{-1/2}$ form of the temperature profile, where $z$ is observation height. We introduce new scaling results for $T$ spectra and $wT$ cospectra from within the surface friction layer (SFL), based on a data from the SLTEST experiment. We confirm earlier results showing that the scaling behaviours of $T$ spectra and $wT$ cospectra change for heights below $z/z_s<0.1$, where $z_s$ the height of the SFL, and come to display properties associated with random diffusion. We conclude by contrasting our interpretation of the role of buoyancy as a system-wide action in CBL flows with that of Richardson, whose ideas inform the current interpretation of the statistical fluid mechanics model of boundary-layer flows.

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