Vladoiu, AndaAndaVladoiuLien, Ren-ChiehRen-ChiehLienKunze, EricEricKunzeMa, BarryBarryMaEssink, SebastianSebastianEssinkYang, Yiing JangYiing JangYangChang, Ming-HueiMing-HueiChangJan, SenSenJanChen, Jia-LinJia-LinChenYang, Kai-ChiehKai-ChiehYangYeh, Yu-YuYu-YuYeh2025-12-312025-12-312025-11https://www.scopus.com/pages/publications/105021003379https://scholars.lib.ntu.edu.tw/handle/123456789/734923Finescale properties of Kelvin–Helmholtz (KH)-like shear instabilities on the trailing edge of a nonlinear lee wave generated by the Kuroshio impinging on a seamount were measured using a towed CTD chain, shipboard ADCP, and echosounder. Lee-wave vertical velocity amplitudes vary in phase with the upstream semidiurnal along-stream current. The instabilities are analogous to atmospheric billows induced by a recirculation on the trailing edge of mountain lee waves. A total of 135 KH billows were identified in a 4-day-long time series roughly 300 m downstream of the center of the lee wave. The KH billows have heights H = 52 ± 11 m, widths L = 162 ± 72 m, and aspect ratios H/L = 0.39 ± 0.18. Positive reduced shear squared S2-4N2 (where S is the vertical shear magnitude and N is the buoyancy frequency) in the shear-stratified billows suggests actively growing instabilities, with comparable contributions from across-and along-flow vertical shear. Billow cores are convectively unstable (N2 < 0). Large turbulent kinetic energy dissipation rates ~O (10-5) Wkg-1 are inferred from density overturns. Density, shear, and inferred turbulence properties vary with billow aspect ratios. As H/L increases, density gradients smear out. For 122 billows with H/L < 0.6, dissipation rates increase by one order of magnitude with increasing H/L. These observations of ~1-m vertical and ~5-m horizontal resolution billow structures and density overturn dissipation rates can provide a reference for future high-Reynolds-number direct numerical simulations.MixingShear structure/flowsTurbulencejournal article10.1175/jpo-d-24-0235.1