Title: Near-surface coherent structures in an intense tropical cyclone: conditional eddies and vertical momentum fluxes Show Chinese title

Title: 强烈热带气旋中的近地表相干结构：条件涡旋和垂直动量通量

Abstract: The intermittency of coherent turbulent structures in the tropical cyclone boundary layer makes them challenging to fully characterize, especially regarding their impact on momentum dynamics in the eyewall. Furthermore, the fine spatial and temporal model resolution needed to resolve these structures has long impeded their understanding. Using the output of a large eddy simulation (with 31-m horizontal and 15-m vertical grid spacing), we investigate the three-dimensional structure of conditionally averaged eddies associated with extreme Reynolds stress events in the near-surface region of a category 5 tropical cyclone. For ejection events, we find (using two- and three-dimensional analysis) that the structure of the conditional eddy is a vortex core roughly inclined toward the direction of the mean flow in the inflowing boundary layer, outer and inner eyewall region. For sweep events, this vortex core is less coherent. The nature of the educed eddies found in this study suggests a similarity between the coherent structures in simpler wall-bounded turbulent flows and those in complex environmental flows. Show Chinese abstract

Abstract: 热带气旋边界层内相干湍流结构的间歇性使其难以被完全表征，特别是在它们对眼墙动量动力学影响方面更是如此。 此外，为了解析这些结构所需的高度精细的空间和时间模型分辨率长期以来阻碍了对其的理解。 利用大型涡模拟（水平31米和垂直15米网格间距）的结果，我们研究了五级热带气旋近地面区域与极端雷诺应力事件相关的条件平均涡旋的三维结构。 对于喷出事件，我们发现（使用二维和三维分析）条件涡旋的结构是在流入边界层、外部和内部眼墙区域的大致倾斜于平均流方向的涡核。 对于扫掠事件，这个涡核的连贯性较差。 本研究中发现的涡旋的本质表明，简单壁面约束湍流流场中的相干结构与复杂环境流场中的相干结构之间存在相似性。