Collaborative Research: Energetically consistent, resolution aware, parameterization of meso-scale eddies in the ocean

这个项目的目的是开发一个框架参数化涡效应，它可以应用于高和低模式分辨率。虽然模拟小组在提高海洋气候模型的空间分辨率方面投入了大量精力，但长期全球气候模拟才刚刚开始进入“允许涡流”的状态。在可预见的未来，许多理想化的研究以及古气候模拟将继续依赖于分辨率更低的模型。因此，充分的参数化表示亚网格涡效应在“非涡动”和“涡动允许”的决议是至关重要的，我们有能力产生足够的海洋气候模拟。此外，理想化的模拟研究，在这个项目中进行，将提供有价值的洞察力的中尺度涡旋和湍流能量循环的属性。这项工作进一步提供了有价值的培训本科实习生，研究生和博士后研究员。他们将接触海洋湍流理论、数值模型开发和模拟，以及大数据集分析，包括数值模型输出和观测数据。最后，该项目支持早期职业PI，他正在芝加哥大学（重新）建立物理海洋学研究和教育。为了实现广泛适用的参数化，本研究将使用子网格涡动动能的明确预算，该预算结合了Eden和Greatbatch（2008）以及Jansen和Held（2014）的想法。这允许封闭的子网格涡动效应，这是符合目前的理解湍流涡动能量循环，而足够简单和一般容易实现在一系列的海洋气候模型，而不增加显着的计算成本。次网格尺度通过斜压不稳定的参数化以及动能和涡度拟能的湍流级联与解析流进行能量交换。正如Jansen和Held（2014年）所讨论的，湍流能量和涡度拟能级联的充分表示需要包括从亚网格尺度到分解流的能量“后向散射”，这迄今为止从未被包括在现实的海洋模型中。本研究的主要内容有沿着三个方面：（1）在斜压不稳定性尚未完全解决的情况下，发展一种基于EKE收支的无涡模式涡度参数化。(2)发展一个EKE预算为基础的涡参数化的“涡允许”的决议，合理的涡样扰动可以明确地模拟，但分辨率仍然不足以完全解决中尺度涡。(3)联合收割机将这两种极限情况组合成一个广义的框架，它适用于广泛的解决方案。最后一步至关重要，因为给定分辨率的模型可能在海洋的某些部分“允许涡流”，而在海洋的其他部分“不允许涡流”（Hallberg，2013年）。基于EKE预算的方法自然有助于制定能够在这两种制度之间充分过渡的参数化。该项目的目标将使用一系列模型来实现，从理想化的过程研究到现实的全球海洋模型。这种层次结构将使团队能够开发一种基于对相关物理过程的基本理解的参数化，同时也适用于复杂的最先进的气候模型。将通过比较理想化的数值模拟与高得多的分辨率参考模拟，并最终通过显示全球海洋模型再现海洋观测的改进能力，来衡量成功与否。

The aim of this project is to develop a framework to parameterize eddy effects, which can be applied at both high and low model resolutions. While modeling groups put significant effort into increasing the spatial resolution of ocean climate models, longer-term global climate simulations are only starting to enter the "eddy-permitting" regime. Many idealized studies, as well as paleoclimate simulations, will continue to rely on models with even coarser resolutions for the foreseeable future. Adequate parameterizations representing sub-grid eddy effects at both "non-eddying" and "eddy-permitting" resolutions are thus crucial for our ability to produce adequate ocean climate simulations. Moreover, idealized modeling studies, performed in this project, will provide valuable insight about properties of mesoscale eddies and the turbulent energy cycle. This work further provides valuable training for an undergraduate intern, a graduate student and a postdoctoral researcher. They will be exposed to the theory of ocean turbulence, numerical model development and simulation, as well as analysis of big data sets, including both numerical model output and observational data. Finally, the project supports an early career PI, who is (re-)establishing physical oceanography research and education at The University of Chicago.To achieve a broadly applicable parameterization, this study will make use of an explicit budget for the sub-grid eddy kinetic energy, which combines ideas of Eden and Greatbatch (2008) and Jansen and Held (2014). This allows for a closure of sub-grid eddy effects that is consistent with the current understanding of the turbulent eddy energy cycle, while being simple and general enough to be readily implemented in a range of ocean climate models without adding significant computational cost. The sub-grid scales exchange energy with the resolved flow via parameterizations of baroclinic instability, as well as the turbulent cascade of kinetic energy and enstrophy. As discussed in Jansen and Held (2014), an adequate representation of the turbulent energy and enstrophy cascade requires the inclusion of energy "backscatter" from the subgrid-scales to the resolved flow, which so far has never been included in a realistic ocean model. This research is organized along three main thrusts: (1) Develop an EKE-budget-based eddy parameterization for non-eddying models, where baroclinic instability remains entirely unresolved. (2) Develop an EKE-budget-based eddy parameterization for "eddy-permitting" resolutions, where reasonable eddy-like disturbances can be simulated explicitly, but the resolution remains insufficient to fully resolve mesoscale eddies. (3) Combine the two limit cases into a generalized framework, which is applicable over a wide range of resolutions. The last step is crucial in light of the fact that models of a given resolution may be "eddy-permitting" in some parts of the ocean, while they are "non-eddying" in other parts of the ocean (Hallberg, 2013). The EKE-budget based approach naturally offers itself to the formulation of a parameterization that can adequately transition between these two regimes. The project goal will be achieved using a hierarchy of models, ranging from idealized process studies, to realistic global ocean models. This hierarchy will allow the team to develop a parameterization that is based in a fundamental understanding of the relevant physical processes, while also being applicable in complex state-of-the-art climate models. Success will be gauged by comparing the idealized numerical simulations to much higher resolution reference simulations, and ultimately by showing the global ocean models' improved ability to reproduce ocean observations.