Exploration of Anisotropy and Inhomogeneity of Ocean Boundary Layer Turbulence

海洋表面边界层是控制海气通量与海洋深层之间相互作用的湍流区域。由于区域和全球数值模式不能完全解决OSBL过程，简化的参数化方案来近似它们。最近的证据表明，不同的参数化和其他错误之间的差异可能是由于物理学的有限和理想化的表示，如假设小尺度湍流是均匀的方向（各向同性）和位置（均匀性）。由于剪切、层化和波浪的影响，OSBL湍流预计会偏离该理想模型。该项目将提供OSBL湍流各向异性和不均匀性的第一次直接观测研究，并使用随水流漂移的声学仪器进行测量。这些定制仪器将具有水平、垂直和对角指向的声束，以在多个方向上对湍流统计进行直接和同时的观测，涵盖从厘米到几十米的尺度，从而解决其各向异性和不均匀性。该项目的观测结果将产生经验性的见解和全面的数据集，可用于模拟和湍流闭合的开发，改进和基准测试。因此，该项目将有助于提高我们预测地球系统动态的能力，从局部现象到更广泛的全球气候动态。了解海洋湍流的不均匀性和各向异性将澄清与用于表征湍流的各种技术相关的误差，偏差和局限性，并导致对现有观测和更好的未来观测实践的校正。该项目将支持应用物理实验室旨在普遍扩大公众对科学的认识和参与的一些补充性外联工作。它将为APL STEM开发项目协调员提供专门的项目支持，以开发APL正在进行和未来的外展项目，促进与当地学校以及就读于华盛顿大学、周边社区学院和技术学校的本科生的联系。每个浮标都配备有一对定制的声学多普勒海流剖面仪（ADCP），在每个浮标上提供总共10个声学多普勒波束，水平、垂直和对角指向。这些组合使用的光束将收集速度波动的多个方向的二阶和三阶统计数据，从而估计湍流能量和能量通量如何在尺度和方向上分配。观测将在湍流潮汐通道和海洋气候站P站点（北太平洋）进行，提供各种强迫条件。该项目的主要影响将是增进对海洋边界层湍流偏离均匀性和各向同性理想模型的程度的了解。对海洋湍流的更全面描述将导致对驱动和控制海洋湍流的复杂过程的更深入理解。它将有助于澄清湍流产生、消散和能量转移的机制，从而更全面地了解海洋流动的动力学。该项目将专门解决一些突出的科学问题，如：什么是OSBL湍流的各向同性惯性子范围的程度？各向异性的大小和分布是什么？各向异性可以预测和参数化吗？各向异性如何影响海洋湍流的测量和参数化？该奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估的支持。

Ocean Surface Boundary Layer is a turbulent region that governs the interaction between air-sea fluxes and the ocean's deeper layers. Since the regional and global numerical models cannot fully resolve OSBL processes, simplified parameterization schemes are used to approximate them. Recent evidence suggests that discrepancies between different parameterizations and other errors may result from the limited and idealized representation of physics, such as the assumption that small-scale turbulence is uniform by direction (isotropy) and location (homogeneity). OSBL turbulence is anticipated to deviate from this idealized model due to the influences of shear, stratification, and waves. This project will provide the first direct observational study of anisotropy and inhomogeneity of OSBL turbulence with measurements from acoustic instruments that drift with the water flow. These custom instruments will have acoustic beams pointing horizontally, vertically, and diagonally to carry out direct and simultaneous observations of turbulence statistics in multiple directions, encompassing scales from centimeters to tens of meters, thereby resolving their anisotropy and inhomogeneity. The observations from this project will produce both an empirical insight and a comprehensive dataset that could be used for development, refinement, and benchmarking of simulations and turbulence closures. Thus, this project will contribute to the evolution of our capacity to forecast the dynamics of the Earth's system across scales ranging from local phenomena to the broader spectrum of global climate dynamics. Understanding the inhomogeneity and anisotropy of ocean turbulence will clarify the errors, biases, and limitations associated with various techniques used to characterize turbulence and lead to the development of corrections for existing observations and better future observational practices. This project will support a number of complementary Applied Physics Laboratory outreach efforts aimed at general broadening of public awareness and participation in science. It will provide dedicated line-item support for APL STEM Development Program Coordinator to develop ongoing and future outreach projects at APL, facilitate connections to local schools as well as undergraduate students attending UW, surrounding community colleges, and technical schools.This project will deploy two Lagrangian floats, each equipped with a pair of customized Acoustic Doppler Current Profilers (ADCPs) providing a total of 10 acoustic Doppler beams on each float pointing horizontally, vertically, and diagonally. These beams, used in combinations, will gather multiple directional second- and third-order statistics of velocity fluctuations, thereby estimating how turbulence energy and energy flux is partitioned across scales and directions. The observations will be conducted in a turbulent tidal channel and at the Ocean Climate Station P site (North Pacific) providing a variety of forcing conditions. The primary impact of the project will be an enhanced understanding of the extent to which ocean boundary layer turbulence deviates from the idealized model of homogeneity and isotropy. A more comprehensive description of ocean turbulence will lead to a deeper understanding of the complex processes that drive and govern turbulence in the ocean. It will help clarify the mechanisms responsible for turbulence generation, dissipation, and energy transfer, leading to a more comprehensive understanding of the dynamics of oceanic flows. The project will specifically address a number of outstanding scientific questions, such as: What is the extent of the isotropic inertial subrange in OSBL turbulence? What is the magnitude and distribution of anisotropy? Can anisotropy be predicted and parameterized? How does anisotropy affect the measurements and parameterization of ocean turbulence?This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.