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

合作研究：海洋中尺度涡流的能量一致、分辨率感知、参数化

• 批准号: 1536360
• 负责人: Alistair Adcroft
• 金额: $ 36.41万
• 依托单位: Princeton University
• 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: 2015-10-01 至 2019-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1536360&HistoricalAwards=false
• 关键词: Collaborative; Research; Energetically; consistent; resolution

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.

这个项目的目的是开发一个框架来参数化涡旋效应，它可以在高和低模式分辨率下应用。虽然建模小组在提高海洋气候模型的空间分辨率方面做出了重大努力，但较长期的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分辨率更高的模型。因此，在“非涡动”和“允许涡流”分辨率下表示亚格子涡旋效应的适当参数对于我们产生充分的海洋气候模拟的能力至关重要。此外，在该项目中进行的理想化模拟研究将为了解中尺度涡旋和湍流能量循环的性质提供有价值的见解。这项工作进一步为本科生实习生、研究生和博士后研究员提供了宝贵的培训。他们将学习海洋湍流理论、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(重新)建立芝加哥大学的物理海洋学研究和教育。为了实现广泛适用的参数化，这项研究将利用子网格涡动动能的显式预算，它结合了Eden和GreatBatch(2008)和Jansen(2014)的想法。这允许关闭与目前对湍流涡旋能量循环的理解一致的子格子涡旋效应，同时足够简单和通用，易于在一系列海洋气候模型中实施，而不会增加大量的计算成本。次网格尺度通过斜压不稳定的参数化，以及动能和辐合的湍动级联，与分解的流动交换能量。正如Jansen和Hold(2014)所讨论的，湍流能量和拟能级联的适当表示需要包括从次网格尺度到可分辨流动的能量“后向散射”，这到目前为止从未被包括在现实的海洋模型中。本研究主要围绕三个方面展开：(1)发展了一种基于EKE预算的非涡旋模式的涡旋参数化方法，该模式的斜压不稳定仍未完全解决。(2)发展了一种基于EKE预算的“允许涡旋”分辨率的涡旋参数化方案，其中合理的涡类扰动可以被显式地模拟，但分辨率仍然不足以完全分辨中尺度涡旋。(3)将这两种极限情况结合成一个广义框架，适用于多种解决方案。最后一步是至关重要的，因为给定分辨率的模型在海洋的某些部分可能是“允许涡流的”，而在海洋的其他部分可能是“非涡流的”(Hallberg，2013)。以EKE预算为基础的办法自然有助于制定一种能够在这两个制度之间充分过渡的参数。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。这一层次将允许团队开发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。成功与否将通过将理想化的数值模拟与更高分辨率的参考模拟进行比较来衡量，最终将通过展示全球海洋模型重现海洋观测的改进能力来衡量。