The nocturnal low-level jet (LLJ) and orographic (gravity) waves play an important role in the generation of turbulence and pollutant dispersion and can affect the energy production by wind turbines. Additionally, gravity waves have an influence on the local mixing and turbulence within the surface layer and the vertical flux of mass into the lower atmosphere. On 25 September 2017, during a field campaign, a persistent easterly LLJ and gravity waves were observed simultaneously in a coastal area in the north of France. We explore the variability of the wind speed, turbulent eddies, and turbulence kinetic energy in the time–frequency and space domain using an ultrasonic anemometer and a scanning wind lidar. The results reveal a significant enhancement of the turbulence-kinetic-energy dissipation (by 50%) due to gravity waves in the LLJ shear layer (below the jet core) during the period of wave propagation. Large magnitudes of zonal and vertical components of the shear stress (approximately 0.4 and 1.5 m² s⁻², respectively) are found during that period. Large eddies (scales of 110 to 280 m) matching the high-wind-speed regime are found to propagate the momentum downwards, which enhances the mass transport from the LLJ shear layer to the roughness layer. Furthermore, these large-scale eddies are associated with the crests while comparatively small-scale eddies are associated with the troughs of the gravity wave.

夜间低空急流 (LLJ) 和地形（重力）波在湍流和污染物扩散的产生中起着重要作用，并且会影响风力涡轮机的能源生产。此外，重力波对表层内的局部混合和湍流以及进入低层大气的质量垂直通量有影响。2017 年 9 月 25 日，在一次野外活动中，在法国北部的一个沿海地区同时观测到持续的东风低空急流和重力波。我们使用超声波风速计和扫描风激光雷达在时频和空间域中探索风速、湍流涡流和湍流动能的变化。结果表明，在波传播期间，由于 LLJ 剪切层（喷射核心下方）中的重力波，湍流-动能耗散显着增强（增加了 50%）。剪切应力的大量纬向和垂直分量（大约 0.4 和 1.5 m²  s ^-2，分别）在该期间被发现。发现与高风速状态匹配的大涡流（110 到 280 m 的尺度）向下传播动量，这增强了从低速急流剪切层到粗糙层的质量传输。此外，这些大尺度的涡流与波峰相关，而相对较小的涡流与重力波的波谷相关。