Turbulence Structures in the Very Stable Boundary Layer Under the Influence of Wind Profile Distortion
Turbulence Structures in the Very Stable Boundary Layer Under the Influence of Wind Profile Distortion
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DOI：
10.1029/2022jd036565
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发表时间：
2022-10
期刊：
影响因子：
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通讯作者：
Changxing Lan;Heping Liu;G. Katul;Dan Li;D. Finn
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文献类型：
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作者：
Changxing Lan;Heping Liu;G. Katul;Dan Li;D. Finn
在非常稳定的边界层（VSBL）中，亚细观运动的“混合物”通常会导致地面以上平均风速最大值升高，成为湍流产生的新来源。这种新的湍流动能来源增强了湍流混合并导致平均风廓线畸变（WPD）。结果，风廓线的这种瞬态畸变调整了经典对数定律。解决 WPD 引起的湍流如何调节流动结构、湍流通量和跨层稳定状态的转变仍然是一个挑战。利用在 62 米高的塔上四个层面测量的涡流协方差数据来解决这些问题。结果表明，WPD 会引发向下渗透的大湍流涡流，从而增强垂直混合并提高跨层湍流传输效率。结果，湍流强度和通量增加。随着 WPD 的增强，由大涡引起的湍流通量和湍流通量传输也会增强，导致从非常稳定状态过渡到弱稳定状态。由于WPD引起的大涡的影响，大涡湍流普朗特数不会明显偏离统一，并且湍流动能和势能之间的分配与梯度理查森数线性相关。
In very stable boundary layers (VSBL), a “cocktail” of submeso motions routinely result in elevated mean wind speed maxima above the ground, acting as a new source of turbulence generation. This new source of turbulent kinetic energy enhances turbulent mixing and causes mean wind profile distortion (WPD). As a results, this transient distortion in the wind profile adjusts the classical log‐law. Addressing how WPD‐induced turbulence regulates flow structures, turbulent fluxes, and transitions in stability regimes across layers remains a challenge. Eddy covariance data measured at four levels on a 62‐m tower are employed to address these questions. It is shown that the WPD initiates large turbulent eddies that penetrate downward, leading to enhanced vertical mixing and comparable turbulent transport efficiencies across layers. As a consequence, turbulence intensity and fluxes are increased. As the WPD is intensified, turbulent fluxes and turbulent flux transport caused by large eddies are also enhanced, leading to a transition from very stable to weakly stable regimes. Due to the influence of WPD‐induced large eddies, the large‐eddy turbulent Prandtl number does not deviate appreciably from unity and the partitioning between turbulent kinetic and potential energies is linearly related to the gradient Richardson number.