An experimental study of the structure of the air-flow above ocean surface waves

近年来，在量化大气和海洋之间的动量交换方面取得了相当大的进展。表面波对海-气动量通量的作用已经得到了很好的证实，但我们对气流动力学的物理理解仍然不完整。这阻碍了我们开发改进的基于物理的参数化以实现更好的天气和海况预报的能力，特别是在大风和极端条件下。在这个项目中，该小组建议对现有数据集进行进一步分析，该数据集包括在实验室中在短表面波上方的近地表气流中进行的广泛的高分辨率2D速度测量。预计这项工作将有助于更好地了解建立准确的(海洋-大气和海洋-波浪-大气)天气和气候耦合模型所必需的海-气界面的详细的小尺度物理。此外，这项研究的数据产品可能会被证明是有用的，与当前和未来的大涡模拟(LES)和直接数值模拟(DNS)进行比较。这个项目将支持一名研究生的博士工作。表面波在大气和海洋边界层耦合动力学中的重要性得到了很好的认识。相比之下，这种现象的大气对应物，即气流分离产生的近地表大气湍流与表面波的耦合，却没有得到足够的重视。到目前为止，我们对近地表湍流(波或切变产生的)和表面波之间的耦合的不完全理解仍然是发展改进的海-气动量通量参数化的障碍。近地表大气边界层中的湍流部分是由破裂引起的气流分离产生的，因此该小组将特别关注湍动能(TKE)和表面波之间的相干和耦合。建议使用的数据涵盖了从1.4(非常年轻的海浪)到66.7(老海浪)不等的波年龄Cp/u&amp；，因此涵盖了与场相关的大范围条件。该团队建议通过三重速度分解来提取湍流和波相干速度场，这种分解是通过波和锁相坐标系实现的。然后，研究小组将评估湍流的动能平衡，他们将特别关注相位相干湍流与表面波之间的相互作用。

In recent years, considerable progress has been made in quantifying the exchange of momentum between the atmosphere and the ocean. The role of surface waves on the air-sea momentum flux is well established but our physical understanding of the airflow dynamics remains incomplete. This impedes our ability to develop improved physically based parameterizations for better weather and sea state predictions, especially in high winds and extreme conditions. In this project, the team proposes the further analysis of an existing dataset consisting of extensive high resolution 2D velocity measurements taken in the laboratory in the near surface airflow above short surface waves. It is anticipated that this work will lead to an improved understanding of the detailed, small scale physics at the air-sea interface that is necessary to build accurate coupled (ocean-atmosphere and ocean-wave-atmosphere) models of weather and climate. Furthermore, data products from this study will likely prove useful for comparison with current and future Large Eddy Simulation (LES) and Direct Numerical Simulation (DNS). This project will support the Ph.D. work of a graduate student.The importance of the surface wave in the dynamics of the coupled atmospheric and oceanic boundary layers is well recognized. In contrast, the atmospheric counterpart of this phenomenon, that is the coupling of the near surface atmospheric turbulence generated by airflow separation with the surface waves, has received less attention. To date, our incomplete understanding of the coupling between the near surface turbulence (wave or shear generated) and the surface waves remains a roadblock to the development of improved air-sea momentum flux parameterizations. Turbulence in the near surface atmospheric boundary layer is in part generated by breaking-induced airflow separation, the team thus will focus in particular on the coherence and coupling between the turbulent kinetic energy (TKE) and the surface waves. The data proposed to use covers wave ages Cp/u∗ varying from 1.4 (very young waves) to 66.7 (old waves) thus encompassing a large range of field-relevant conditions. The team proposes to extract turbulent and wave-coherent velocity fields by means of a triple velocity decomposition made possible by a wave- and phase-locked coordinate system. The team will then evaluate the turbulent kinetic balance and they will especially focus on the interaction between phase coherent turbulence and the surface waves.