Submeso Motions and Intermittent Turbulence Across a Nocturnal Low-Level Jet: A Self-Organized Criticality Analogy
Submeso Motions and Intermittent Turbulence Across a Nocturnal Low-Level Jet: A Self-Organized Criticality Analogy
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DOI：
10.1007/s10546-019-00441-8
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发表时间：
2019-03
影响因子：
4.3
通讯作者：
D. Cava;L. Mortarini;U. Giostra;O. Acevedo;G. Katul
中科院分区：
文献类型：
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作者：
D. Cava;L. Mortarini;U. Giostra;O. Acevedo;G. Katul
稳定边界层的标志之一是湍流（主动）和非湍流（被动）状态之间的转换。在非常稳定的条件下，边界层变得分层，充分发展的湍流被限制在地表附近的浅层区域。在这个近地表的静止区域，湍流是微弱的，间歇的，与地面分离的。这些条件促进了低空急流的发展，低空急流通过升高的切变层重新给湍流注入能量。Monin-Obukhov相似理论在层状稳定边界层中失效，从而使混合和输运性质的量化对数值模型具有挑战性。在本研究中，使用电报近似分析了来自高（140 m）气象塔的多级时间序列，以研究与一般类型的包括自组织临界性的间歇性模型的类比。湍流与自组织临界之间的类比仅限于描述湍流与非湍流状态之间切换的流动变量符号变化的聚类性质。电报近似为湍流运动、低空射流和亚中观运动主导的时期的群集和外部和内部间歇性提供了新的视角。其中一些时期的特点是没有湍流，但偶尔被间歇性湍流事件的爆发所打断。活跃-非活跃状态的切换概率和非活跃状态的寿命（与间歇性湍流爆发有关）在标度律方面显示了自组织临界性行为的证据。自组织临界和间歇湍流的共存可能为尺度定律和相似参数的起源提供新的视角，从而改善稳定边界层数值模型的性能。
One of the hallmarks of the stable boundary layer is the switching between turbulent (active) and non-turbulent (passive) states. In very stable conditions, the boundary layer becomes layered with fully-developed turbulence confined to a shallow region near the surface. In the quiescent region above this near-surface layer, the turbulence is weak, intermittent and detached from the ground. These conditions promote the development of a low-level jet that re-energizes the turbulence through an elevated shear layer. The Monin–Obukhov similarity theory fails in the layered stable boundary layer thereby making the quantification of mixing and transport properties challenging for numerical models. In the present study, multi-level time series from a tall (140 m) meteorological tower are analyzed using the telegraphic approximation to investigate analogies with a general class of intermittency models that include self-organized criticality. The analogy between turbulence and self-organized criticality is restricted to clustering properties of sign changes of flow variables for describing switching between turbulent and non-turbulent states. The telegraphic approximation provides a new perspective on clustering and on external and internal intermittency for periods dominated by turbulent motions, a low-level jet and submeso motions. Some of these periods are characterized by the absence of turbulence but occasionally punctuated by bursts of intermittent turbulent events. The switching probability of active–inactive states and the lifetimes of inactive states (related to intermittent turbulent bursts) show evidence of self-organized-criticality like behaviour in terms of scaling laws. The coexistence of self-organized criticality and intermittent turbulence may offer new perspectives on the genesis of scaling laws and similarity arguments, thereby improving the performance of numerical models in the stable boundary layer.