Scale interactions in the equatorial ocean

赤道海洋的尺度相互作用

• 批准号: 0751962
• 负责人: Kelvin Richards
• 金额: $ 52.83万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-05-01 至 2013-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0751962&HistoricalAwards=false
• 关键词: Scale; interactions; equatorial; ocean

This project is directed at understanding the formation of small vertical scale features inthe equatorial thermocline, their interaction with other scales, and the overall impact on the larger scale dynamics of equatorial flows. The investigation is undertaken in the context of the wind forced basin scale flow. The stimulus comes from observations of such small vertical scale features in the thermocline of the equatorial Pacific and findings emerging from recent theoretical and numerical work. In addition to the familiar barotropic/baroclinic instabilities of the zonal mean flow, equatorial currents are also subject to instabilities that favor much smaller vertical scales of the order of tens of meters but with relatively large meridional and zonal extents. A manifestation of small vertical scale features in the equatorial thermocline is the presence of the interleavingof water masses. Previous work suggests that such features have a significant impact on the basin scale dynamics. We have devised a series of numerical experiments to elucidate the properties of these small vertical scale structures and their interaction with other scales. Making use of the considerable computational resource of the Japanese Earth Simulator we are able to put this study in the context of the basin wide dynamics.Intellectual Merit: The extraordinary richness in spatial scales coupled with the high temporal variability of the equatorial ocean raises a number of intriguing and important questions concerning the scale selection process of features, meridional versus zonal coherence, and the potential interaction between scales. The small scale features themselves can induce considerable mixing of tracers, momemtum and potential vorticity, affecting the development of other modes and the large scale state. Our investigation covers aspects of equatorial dynamics that have only recently started to be studied. We will capitalize on new findings on the stability of equatorial flows. The outcome will be an improved understanding of equatorial dynamics and the impact of multi scale interactions in the system.Broader Impacts: The robustness of climate predictions depends on the effectiveness of atmosphere and ocean models to capture the essential physics of the problem. The ocean state affects the seasonal and interannual variability of the coupled system. The ocean state is itself very sensitive to the form and level of lateral and vertical mixing. Here we plan to explicitly model the mixing induced by small vertical-scale structures in the equatorial thermocline and their overall impact on the basin-scale dynamics. The characteristics of the small vertical scale features are themselves dependent on the broader scale flow on intraseasonal through to interannual timescales. We have the intriguing possibility of multiple scale interactions on a broad range of space and time scales. The present study will go some way to assessing what aspects of these interactions need to be taken into account in climate models. A graduate student will be employed on the project. The student will receive training in fluid dynamics, numerical modeling and analysis of observations.

该项目旨在了解赤道温跃层中小垂直尺度特征的形成，它们与其他尺度的相互作用，以及对赤道气流大尺度动力学的总体影响。该调查是在风强迫流域尺度流动的背景下进行的。这种刺激来自于对赤道太平洋温跃层中这种小的垂直尺度特征的观测，以及最近的理论和数值工作中出现的结果。除了常见的纬向平均气流的正压/斜压不稳定性外，赤道气流也受到不稳定性的影响，这种不稳定性有利于几十米量级的小得多的垂直尺度，但具有相对较大的纬向和纬向范围。在赤道温跃层中小垂直尺度特征的一个表现是水团的交错存在。以前的工作表明，这些功能有一个显着的影响，流域尺度的动态。我们设计了一系列的数值实验，以阐明这些小的垂直尺度结构的属性和它们与其他尺度的相互作用。利用日本地球模拟器的大量计算资源，我们能够将这项研究放在流域范围的动力学背景下进行。赤道海洋的空间尺度异常丰富，加上时间上的高度变化，提出了一些有趣的重要问题，涉及特征的尺度选择过程，纬向与纬向一致性，以及尺度之间潜在的相互作用。小尺度特征本身可以引起示踪剂、动量和位涡的大量混合，从而影响其他模态的发展和大尺度状态。我们的调查涵盖了赤道动力学方面，最近才开始研究。我们将利用关于赤道气流稳定性的新发现。其结果将是更好地了解赤道动力学和多尺度相互作用的影响在system.Broader影响：气候预测的鲁棒性取决于大气和海洋模型的有效性，以捕捉问题的基本物理。海洋状态影响耦合系统的季节和年际变化。海洋状况本身对横向和垂直混合的形式和程度非常敏感。在这里，我们计划明确模拟混合诱导的小垂直尺度结构在赤道温跃层和盆地尺度动力学的整体影响。小垂直尺度特征的特征本身取决于更广泛的尺度流动的季节内到年际的时间尺度。我们在广泛的空间和时间尺度上存在多尺度相互作用的有趣可能性。本研究将在一定程度上评估这些相互作用的哪些方面需要在气候模型中考虑。一名研究生将受雇于该项目。学生将接受流体动力学，数值建模和观察分析的培训。