Collaborative Research: Probing internal gravity wave dynamics and dissipation using global observations and numerical simulations

该项目将利用最先进的高分辨率全球和区域重力波模型以及重力波的理论和观测，绘制内部重力波耗散和混合的时空地理，以及潜在的动力学。该研究将采用全球模式、区域模式、观测和理论，朝着未来模式中IW耗散和混合自然产生而不被参数化的方向迈出第一步。该项目将支持东非肯尼亚的两所海洋与环境科学暑期学校，以补充自2015年以来每年成功举办的西非暑期学校，累计有数百名非洲参与者和数十名美国参与者参加。主要研究人员假设，IW谱在全球IW模式中的表现是足够真实的，因此模式可以对IW耗散的时空分布以及由此引介的IW诱导的混合作出有用的预测。他们还假设，就像湍流的大涡模拟可以隐式地解决惯性子范围一样，通过适当选择耗散方案、模式分辨率、大气强迫频率和非流体静力学的启用，模型中隐式地解决IW连续体可能是可以实现的。将运行区域IW模式，以确定分辨率限制和消散机制对模拟IW谱的影响。区域IW模拟和IW理论将用于探讨IW频谱和耗散背后的动力学。耗散将使用四种不同的方法进行映射：使用传统的傅立叶技术计算谱通量，使用新的粗粒化技术计算谱通量，作为IW转化率和通量散度的残余，以及从应用于高频流的模型耗散算子计算谱通量。模拟的能量耗散率将与基于观测的耗散估计进行比较，这些耗散估计来自应用于ARGO浮子和船载CTD管线的精细结构方法，以及来自nsf资助的EM-APEX浮子组的微观结构测量。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。

This project will map the space-time geography of internal gravity wave (IW) dissipation and mixing, and the underlying dynamics, using state-of-the-art high-resolution global and regional IW models along with theory and observations of IWs. The research will employ global models, regional models, observations, and theory to take a first step towards a future in which IW dissipation and mixing arise naturally in models, without being parameterized. The project will support two summer schools on ocean and environmental science in Kenya, East Africa, to complement the successful West African summer schools that has been run every year since 2015, with cumulative participation of several hundred African participants and several dozen US participants.The Principal Investigators hypothesize that the representation of the IW spectrum in global IW models is sufficiently realistic for the models to make useful predictions about spatial and temporal distributions of IW dissipation and, by extension, IW-induced mixing. They also hypothesize that much as an inertial subrange is implicitly resolved by Large Eddy Simulations of turbulence, an implicitly resolved IW continuum in models may be within reach with appropriate choices of dissipation schemes, model resolutions, atmospheric forcing frequency, and enabling of nonhydrostatic dynamics. Regional IW models will be run to determine the impacts of resolution limitations and dissipation mechanisms on the modeled IW spectrum. Regional IW simulations and IW theory will be used to probe the dynamics underlying the IW spectrum and dissipation. Dissipation will be mapped using four different methods: as spectral fluxes computed using traditional Fourier techniques, as spectral fluxes computed using new coarse-graining techniques, as a residual of IW conversion rates and flux divergences, and as computed from model dissipation operators applied to high-frequency flow. Modeled energy dissipation rates will be compared to observation-based estimates of dissipation, from fine-structure methods applied to ARGO floats and ship-based CTD lines, and from microstructure measurements including those from a new NSF-funded set of EM-APEX floats.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.