Collaborative Research: Inertially Unstable Currents and Internal Waves

合作研究：惯性不稳定电流和内波

• 批准号: 0526033
• 负责人: Rudolf Kloosterziel
• 金额: --
• 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: 2005
• 资助国家: 美国
• 起止时间: 2005-09-01 至 2007-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0526033&HistoricalAwards=false
• 关键词: Collaborative; Research; Inertially; Unstable; Currents

0525776/0526033Inertial instability has been widely studied in meteorology where it is considered a source of clearair turbulence, rain bands, squall lines and atmospheric gravity waves. It has received much lessattention in oceanography probably because it is generally thought to occur only for anticyclonically (clockwise) sheared parallel flows or anticyclones of strengths not typically observed in the ocean. However, there are many observations of anticyclonic currents in the ocean that are marginally stable, and this suggests that inertial instability may be the primary mechanism by which anticyclonic shear and anticyclonic vortices are maintained at stable or marginally stable values. The criterion for inertial instability is often quoted as Rossby number less than minus one, where a negative Rossby number implies anticyclonic flow However this criterion applies only to flows in homogeneous fluids like the mixed layer with no vertical shear In stratified flow that is vertically sheared as is commonly the case inertial instability can also occur with Rossby numbers between -1 and 0. Furthermore, even cyclonically sheared flows or cyclonic vortices for which Ro is greater than zero can be inertially unstable if the vertical shear is strong enough. It is also interesting that this instability can occur when the Richardson number is well above a quarter that is, in flows that are stable to the Kelvin Helmholtz instability, a controlling factor in oceanic flows. In other words, flows that are stable with regard to the well known Richardson number criterion can, in fact, be unstable because of inertial instability. It is therefore possible that inertial instability is frequently a controlling factor in oceanic flows without having been recognized as such. This renewal proposal will continue studies of inertial instability with the object of providing a fundamental basis for understanding the role that inertial instability plays in the worlds oceans. Under prior NSF funding, the investigators have performed a systematic numerical study of the effect of varying basic parameters on the inertial instability of idealized model vortices with no vertical shear and with weak vertical shear. In addition, the resulting analytical model, based on plane parallel horizontally sheared flow, is able to explain and predict much of the fundamental results of the numerical studies. From these investigations, there are now guidelines for exploring further. The previous studies will be extended to much more realistic models of oceanic vortices. Through a series of numerical simulations the effects of inertial instability will be studied in a variety of model vortices over a wide range of the essential parameters.Intellectual Merit: By undertaking our investigation of inertial instability, we hope to improve our understanding of the role that inertial instability plays in stabilization and maintenance of oceanic currents and eddies.Broader Impacts: As a broader impact, these studies should provide guidance for those attempting to develop parameterizations for ocean models and criteria for determining likely locations for intense internal wave generation and inertial instability. Because of the intrinsically small vertical scales of inertial instability, it is usually not resolved by ocean models. Thus, the simulated flows can become and stay inertially unstable. This unphysical behavior must be corrected to maintain currents in the models at physically realizable levels, but a proper parameterization of the effects of the instability can be obtained only through increased understanding. This collaborative research project will foster an international collaboration with professor Orlandi at the University of Rome and one of his graduate students.

0525776/0526033的纯稳定性已在气象学中被广泛研究，在气象学中，它被认为是Clearair湍流，雨带，偏斜线和大气重力波的来源。它在海洋学中的注意力较少可能是因为通常认为它仅用于抗旋风（顺时针）剪切的平行流或强度的强度，通常在海洋中观察到的强度。但是，海洋中有许多稳定的反流行电流的观察结果，这表明惯性不稳定性可能是稳定或边缘稳定值以稳定或稳定值保持反流行剪切和反气旋涡流的主要机制。 The criterion for inertial instability is often quoted as Rossby number less than minus one, where a negative Rossby number implies anticyclonic flow However this criterion applies only to flows in homogeneous fluids like the mixed layer with no vertical shear In stratified flow that is vertically sheared as is commonly the case inertial instability can also occur with Rossby numbers between -1 and 0. Furthermore, even cyclonically sheared如果垂直剪切足够强大，则RO大于零的流量或旋风涡旋可能会暂时不稳定。 有趣的是，当理查森（Richardson）的数字远高于四分之一的流量，这可能会发生这种不稳定性，而该四分之一的流量是稳定的开尔文·赫尔姆霍尔茨（Kelvin Helmholtz）不稳定的流量，这是海洋流中的控制因素。换句话说，关于众所周知的Richardson数字标准的流量实际上是由于惯性不稳定而不稳定的。因此，惯性不稳定性通常是海洋流中的控制因素，而不会被认为。该更新提案将继续研究惯性不稳定，目的是为了解惯性不稳定在世界海洋中发挥的作用提供基本依据。在先前的NSF资金下，研究人员对不同的基本参数对理想化模型涡流的惯性不稳定性的影响进行了系统的数值研究，没有垂直剪切，并且垂直剪切弱。此外，基于平面平行的水平剪切流的结果分析模型能够解释和预测数值研究的基本结果。从这些调查中，现在有进一步探索的指南。先前的研究将扩展到更现实的海洋涡流模型。通过一系列数值模拟，将在各种模型涡流中研究惯性涡流的效果。IntlectualFure：通过对惯性不稳定的研究进行研究，我们希望能够提高对惯性不稳定在稳定和维持的指导下的影响，以实现惯性不稳定的作用。海洋模型的参数化和标准，用于确定强烈的内波产生和惯性不稳定的位置。由于惯性不稳定性的本质垂直尺度很小，因此它通常不会被海洋模型解决。因此，模拟的流可以成为并惯性地保持不稳定。必须校正这种非物理行为以在模型中保持电流的物理可实现的水平，但是只能通过增加理解才能获得不稳定性影响的适当参数化。这个合作研究项目将与罗马大学的奥兰迪教授和他的一位研究生建立国际合作。