Organized kinetic energy backscatter in the hurricane boundary layer from radar measurements
Organized kinetic energy backscatter in the hurricane boundary layer from radar measurements
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DOI：
10.1017/jfm.2021.632
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发表时间：
2021-08
影响因子：
3.7
通讯作者：
S. Guimond;Sydney Sroka
中科院分区：
文献类型：
--
作者：
S. Guimond;Sydney Sroka
由于系统的暖核性质，飓风的流体力学强烈依赖于边界层能量，峰值速度位于较低层。阻碍对边界层中的能量传递进行更完整描述的一个障碍是缺乏能够解决大的湍流的观测。特别是，飓风边界层中高层能量转移(后向散射)的发生和结构以及后向散射对涡旋强度的影响尚不清楚。本文对飓风丽塔(2005)峰值强度的高分辨率三维风观测进行了分析，揭示了边界层中与连贯的湍流涡旋有关的大片有组织的后向散射。由于相邻涡之间的相互作用，在后向散射区附近也发现了较强的前向散射。应力张量的两个分量是造成这种交替散射结构的主要原因，场之间的大相关系数表明：径向垂直分量(13)和方位垂直分量(23)的平均相关性分别为79%和49%。还提供了Leonard、Reynolds和交叉项应力分量。通过计算分辨尺度和涡旋尺度运动的动能收支，估计了次滤波尺度能量传递的影响。结果表明，次滤波尺度能量传输项与涡度预算中的其他项具有相同的量级，对当地时间趋势的贡献在16%~40%之间，平均贡献约30%。这些结果表明，相干湍流涡可以通过波-波非线性相互作用影响涡动力学，进而影响波-均流相互作用。这是第一次研究整个次过滤尺度的能量转移及其对飓风边界层动能收支的影响。这些发现强调了相干湍流在能量叶栅中的重要性，并有可能改进数值模拟中使用的湍流闭合方案。
Abstract The fluid mechanics of hurricanes strongly depends on boundary layer energetics due to the warm-core nature of the system with peak velocities located at lower levels. One barrier that has inhibited a more complete characterization of energy transfer in the boundary layer is a lack of observations that resolve large, turbulent eddies. In particular, the occurrence and structure of upscale energy transfer (backscatter) in the hurricane boundary layer as well as the effects of backscatter on the vortex intensity are unknown. The analysis presented here of very high-resolution, three-dimensional wind observations from Hurricane Rita (2005) at peak intensity reveals large regions of organized backscatter in the boundary layer associated with coherent, turbulent eddies. Strong forwardscatter is also found next to the backscatter regions due to the interaction between adjacent eddies. Two components of the stress tensor are primarily responsible for this alternating scatter structure, as shown by large correlation coefficients between the fields: the radial–vertical component ($\tau _{13}$) and the azimuthal–vertical component ($\tau _{23}$) with average correlations of 79 % and 49 %, respectively. The Leonard, Reynolds and cross-term stress components are also provided. The impact of the sub-filter-scale energy transfer is estimated by computing the kinetic energy budget for the resolved-scale and eddy-scale motions. The results show that the sub-filter-scale energy transfer term is of the same order as the other terms in the eddy-scale budgets, contributing between 16 % and 40 % to the local time tendency with an average contribution of approximately 30 %. These results indicate that the coherent turbulent eddies can affect the vortex dynamics through wave–wave nonlinear interactions, which can subsequently influence the wave–mean flow interactions. This is the first study to examine the full sub-filter-scale energy transfer and its impact on the kinetic energy budget in the hurricane boundary layer. These findings emphasize the importance of coherent turbulence in the energy cascade and have the potential to improve turbulence closure schemes used in numerical simulations.