Storm-Driven Near-Inertial Waves and Mixing in the Western North Pacific

西北太平洋风暴驱动的近惯性波和混合

• 批准号: 1459173
• 负责人: Ren-Chieh Lien
• 金额: $ 244.63万
• 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: 2015
• 资助国家: 美国
• 起止时间: 2015-04-15 至 2021-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1459173&HistoricalAwards=false
• 关键词: Storm; Driven; Near; Inertial; Waves

Quantification and understanding of ocean mixing remains one of the most challenging problems in physical oceanography and ocean climate. The accurate representation (parameterization) and distribution of mixing in ocean circulation models is critical to correctly reproduce a wide range of processes from precipitation in the western equatorial Pacific to the strength of the meridional overturning cell and biogeochemical cycles. Near-inertial waves are one of three major sources of deep-ocean mixing. Little is known about their energy pathways beyond their wind generation and that only 15-25% of the wind-forced near-inertial wave energy radiates equatorward as low mode waves. These waves contain half the kinetic energy and most of the vertical shear in the ocean. About a terawatt of inertial wind power is injected by a few dozen mid-latitude fall and winter storms. While numerical and observational evidence points to the bulk of the inertial wind power being lost in the near-field of storm forcing, dissipating and mixing immediately below the surface layer, there has been little observational work to investigate this major piece of the inertial energy budget in detail. As well as determining the fate of wind-forced near-inertial waves, the proposed work will quantify the climatologically-important depth dependence of turbulent mixing in the pycnocline. The project investigators will consult with numerical modelers to how to improve parameterizations for internal-wave-driven turbulent mixing based on their observational findings. A graduate student will be trained in data analysis and interpretation and the project scientists will continue their local public outreach efforts.An innovative observational strategy is proposed to determine the zero-order near-field fate of inertial wind power and the vertical distribution of upper-ocean mixing following storms. An array of twelve profiling floats with electro-magnetic current meters and temperature microstructure sensors will be deployed in the western North Pacific near the inertial wind power gain maximum for a fall-winter season. Using bi-directional Iridium communications, dynamic sampling will focus on storm responses. The instruments will repeatedly profile every three hours between ~ 3 m of the surface and 500-m depth, collecting roughly five thousand profiles of temperature, salinity, horizontal velocity and turbulent temperature-variance dissipation rate. These measurements will provide about fifty independent depth-time series of the surface mixed-layer and upper pycnocline storm responses following five to ten fall and winter storms for a random variety of ocean eddy states. Harmonic fits will separate near-inertial, sub-inertial and higher-frequency signals. The measurements will quantify where and how near-inertial shear contributes to turbulence mixing, as well as estimate radiative losses.

海洋混合的量化和理解仍然是物理海洋学和海洋气候中最具挑战性的问题之一。海洋环流模式中混合的精确表示（参数化）和分布对于正确再现从赤道西太平洋降水到赤道翻转单体和海洋地球化学循环强度的广泛过程至关重要。近惯性波是深海混合的三个主要来源之一。除了风力发电外，人们对它们的能量途径知之甚少，只有15-25%的风力近惯性波能量作为低模波向赤道辐射。这些波包含了海洋中一半的动能和大部分的垂直切变。大约一太瓦的惯性风力是由几十个中纬度的秋季和冬季风暴注入的。虽然数值和观测证据表明，大部分惯性风力损失在近场的风暴迫使，消散和混合直接低于表层，一直很少有观测工作来调查这一主要部分的惯性能量预算的细节。以及确定风强迫的近惯性波的命运，拟议的工作将量化的湍流混合在密度跃层的气候重要的深度依赖。项目研究人员将与数值模拟人员协商，如何根据他们的观测结果改进内波驱动湍流混合的参数化。一名研究生将接受数据分析和解释方面的培训，项目科学家将继续在当地开展公共宣传工作，提出了一项创新的观测战略，以确定惯性风力的零阶近场命运和风暴后海洋上层混合的垂直分布。一个由12个带有电磁流速计和温度微结构传感器的剖面浮标组成的阵列将部署在北太平洋西部靠近秋冬季节惯性风力增益最大值的地方。利用双向铱通信，动态采样将侧重于风暴反应。这些仪器将每三小时在表面~ 3米和500米深度之间重复进行剖面测量，收集大约五千份温度、盐度、水平速度和湍流温差耗散率的剖面。这些测量将提供大约50个独立的深度-时间序列的表面混合层和上层密度跃层风暴响应后，五至十个秋季和冬季风暴的随机变化的海洋涡动状态。谐波拟合将分离近惯性、亚惯性和高频信号。这些测量将量化近惯性剪切在何处以及如何对湍流混合做出贡献，并估计辐射损失。