Collaborative Research: Interaction of eddies with mixed layers

将推导中尺度涡旋与上层海洋湍流混合相互作用的参数化，并在气候模式中进行测试。在海洋环流模式中使用的中尺度参数化通常只表示涡流对可用势能的绝热释放，正如Gent和McWilliams所建议的那样。在海洋上层，涡旋通量发展为非绝热成分，因为密度通过强混合保持垂直均匀，而地转运动在边界附近被限制为水平运动。此外，在小尺度上，中尺度应变相互作用并改变湍流混合。这些非绝热表面涡旋通量的动力学及其与小尺度湍流的相互作用尚未完全了解，目前也没有在海洋模式的表面混合层中参数化。取而代之的是，锥形格式被用来转换绝热涡旋通量格式在表面。耦合气候模式对这种渐缩格式的选择非常敏感。本文提出了一种基于变换欧拉平均值的涡流参数化方法。该方法为处理绝热内部和绝热表面边界层的涡流通量提供了一个统一的框架。该项目包括：1)分析具有上层海洋涡输送关键信息的观测数据集；2)明确解析混合层全范围运动的高分辨率过程模型；3)基于数值效率与观测和模拟所得理论信息之间的折衷，推导新的参数化方案。该小组的主要重点将是在GFDL、NCAR和GSFC模拟中心目前使用的耦合气候模型中实施和测试新的参数化方案。这项研究旨在改进大气和海洋的最先进模型，以研究地球气候及其未来可能发生的变化。因此，它具有很大的社会影响。该项目还将有助于培养一批博士后和研究生，在观察、理论和建模之间架起桥梁。

Parameterizations for the interaction of mesoscale eddies with turbulent mixing in the upper ocean will be derived and tested in climate models. Mesoscale parameterizations used in ocean general circulation models typically represent only the adiabatic release of available potential energy by eddies, as suggested by Gent and McWilliams. In the upper ocean, eddy fluxes develop a diabatic component because density is maintained vertically homogeneous by strong mixing while geostrophic motions are constrained to be horizontal near the boundary. Furthermore mesoscale strain interacts and modifies turbulent mixing at small scales. The dynamics of these diabatic surface eddy fluxes and their interactions with small-scale turbulence are not fully understood, and are not currently parameterized in the surface mixed layers of ocean models. Instead, tapering schemes are used to turn of the adiabatic eddy flux schemes at the surface. Coupled climate models are very sensitive to the choice of this tapering scheme. Here a new approach to eddy parameterizations, based on the Transformed Eulerian Mean is proposed. The new approach provides a unified framework for the treatment of eddy fluxes in the adiabatic interior and in the diabatic surface boundary layer.The project involves 1) analysis of observational data sets with key information on eddy transport in the upper ocean, 2) high resolution process models that explicitly resolve the full range of motions in the mixed layer, and 3) the derivation of new parameterization schemes based on a compromise between numerical efficiency and the theoretical information learned from observations and simulations. The main focus of the Team will be to implement and test the new parameterization schemes in the coupled climate models currently used in the modeling centers at GFDL, NCAR, and GSFC. This research is aimed at improving state of the art models of the atmosphere and ocean for study of the climate of the Earth and how it might change in the future. Thus it is of great societal impact. The project will also contribute to the education of a number of post-doctoral and graduate students bridging between observations, theory, and modeling.