Mixing in the equatorial Pacific: the role of interleaving

该项目的重点是横向混合和观测到的赤道水团交错的作用。估计表明，交错的有效横向扩散系数约为1000m2s-1。在海洋环流模式(OGCM)的初步试验中发现，在赤道附近施加一个这种量级的增强混合系数，既可以限制赤道潜流(EUC)的强度，又可以减少东部冷舌的冷偏差，从而解决了困扰气候研究中海洋模式的两个问题。最终目标是提供一种适用于气候研究中海洋模式的交错参数化方案，从而提高气候模式的可靠性和预测能力。对现有观测结果的分析将与线性稳定性理论、数值过程研究和OGCM相结合，以阐明交错过程的基本物理。将量化相关的动量通量和示踪剂通量，并确定这些通量与更广泛的海洋状况尺度特征之间的关系。主要的焦点将放在惯性不稳定(和其他剪切引起的不稳定)上，作为分层形成和随后演变的主要机制。将特别注意交错过程的三维性质。双扩散垂直通量也可能起作用，其影响将被调查和量化。将开发和测试交错的参数化方案，并将调查其对为太平洋配置的OGCM特征的影响。广泛影响：任何气候预测的有用性取决于其技能和可靠性；对规划者和资源管理者的反应方式和人类社会的潜在收益具有影响。通过增加对所涉及的物理过程的了解，可以提高预报的可靠性。交错带来的混合增强很可能影响ENSO事件的发展，并可能影响其年代际变化。这项拟议的工作旨在产生对负责预测ENSO的机构以及其他研究人员直接有用的输出。这项工作与气候变异性和可预测性计划(CLIVAR)的目标直接相关，并将对即将到来的海洋生物地球化学计划有用。

This project focuses on lateral mixing and the role of the observed interleaving of water masses across the equator. Estimates suggest that the interleaving has an effective lateral diffusion coefficient of the order of 1000 m2s-1. Imposing an enhanced mixing coefficient of this magnitude close to the equator is found in preliminary experiments with an ocean general circulation model (OGCM) to both limit the strength of the Equatorial Under Current (EUC) and reduce the cold bias in the eastern cold tongue, thus resolving two problems which plague ocean models used in climate studies. The ultimate goal is to provide a parameterization scheme for interleaving suitable for ocean models used in climate studies, and thus improves the reliability and predictive skill of climate models. An analysis of existing observations will be combined with linear stability theory, numerical process studies and an OGCM to elucidate the fundamental physics of the interleaving process. Associated fluxes of momentum and tracers will be quantified and the relationship between these fluxes and the broader scale characteristics of the ocean state will be determined. The main focus will be on inertial instability (and other shear induced instabilities) as the prime mechanism for the formation and subsequent evolution of the layering. Particular attention will be paid to the three dimensional nature of the interleaving process. Double diffusive vertical fluxes may also play a role and their impact will be investigated and quantified. A parameterization scheme for interleaving will be developed and tested, and its impact on the characteristics of an OGCM configured for the Pacific Ocean will be investigated.Broader Impacts: The usefulness of any climate forecast depends crucially on its skill and reliability; with implications for the way planners and resource managers react and the potential gains by human society. The reliability of a forecast is improved through an increased understanding of the physical processes involved. The enhanced mixing brought about by interleaving may well affect the development of ENSO events and possibly its decadal variability. The proposed work is designed to have an output that is directly useful to agencies charged with making ENSO forecasts, as well as other researchers. The work is directly related to the aims of the Climate variability and predictability Program (CLIVAR) and will be useful to the forthcoming ocean biogeochemistry program.