Exploration of Anisotropy and Inhomogeneity of Ocean Boundary Layer Turbulence

海洋边界层湍流的各向异性和不均匀性探索

• 批准号: 2344156
• 负责人: Andrey Shcherbina
• 金额: $ 119.59万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-04-15 至 2027-03-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2344156&HistoricalAwards=false
• 关键词: Exploration; Anisotropy; Inhomogeneity; Ocean; Boundary

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.

海洋表面边界层是一个湍流区域，控制着海气通量与海洋深层之间的相互作用。由于区域和全球数值模式不能完全解析OSBL过程，因此采用简化的参数化方案来逼近OSBL过程。最近的证据表明，不同参数化之间的差异和其他错误可能是由物理的有限和理想化的表示造成的，例如假设小尺度湍流在方向（各向同性）和位置（均匀性）上是均匀的。由于切变、分层和波浪的影响，预计OSBL湍流将偏离这一理想模式。该项目将首次利用随水流漂移的声学仪器对OSBL湍流的各向异性和非均匀性进行直接观测研究。这些定制仪器将有声束指向水平、垂直和对角线，在多个方向上进行湍流统计的直接和同时观测，包括从厘米到几十米的尺度，从而解决它们的各向异性和不均匀性。该项目的观察结果将产生经验见解和综合数据集，可用于模拟和湍流闭包的开发、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，预测范围从局部现象到更广泛的全球气候动力学。了解海洋湍流的非均匀性和各向异性将澄清用于表征湍流的各种技术的错误、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修正发展。该项目将支持一些互补的应用物理实验室外展工作，旨在广泛扩大公众对科学的认识和参与。它将为APL STEM发展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西澳大学、周边社区学院和技术学校的本科生的联系。该项目将部署两个拉格朗日浮子，每个浮子都配备一对定制的声学多普勒电流分析器（adcp），每个浮子上总共提供10个声学多普勒波束，指向水平、垂直和对角线。这些光束组合使用，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划分。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加强对海洋边界层湍流偏离均匀性和各向同性理想模式的程度的理解。对海洋湍流的更全面的描述将导致对驱动和控制海洋湍流的复杂过程的更深入的理解。这将有助于阐明湍流产生、耗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。该项目将具体解决一些突出的科学问题，例如：OSBL湍流中各向同性惯性子范围的范围是多少？各向异性的大小和分布是什么？各向异性能被预测和参数化吗？各向异性如何影响海洋湍流的测量和参数化？该奖项反映了美国国家科学基金会的法定使命，并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，被认为值得支持。