Numerical Methods for Layered Models of Ocean Circulation

海洋环流分层模型的数值方法

• 批准号: 0107495
• 负责人: Robert Higdon
• 金额: $ 14万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-09-15 至 2005-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0107495&HistoricalAwards=false
• 关键词: Numerical; Methods; Layered; Models; Ocean

The goal of this project is to develop numerical methods for layered (isopycnal) models of the general ocean circulation. In such models, the vertical coordinate is not linear distance, but instead is potential density or some other related quantity. When an isopycnal model is discretized in the vertical, the effect is to represent the ocean as a stack of layers that are approximately immiscible. This corresponds to the observation that the upper and lower regions of the ocean are approximately isolated thermodynamically from each other. However, this isolation is not complete, and in an isopycnal model the exchanges that do occur are under the control of the modeler. This type of model shows great promise for representing the long-term behavior of ocean dynamics. In the present project, the principal investigator will develop and incorporate methods for solving the momentum equation in a flux form for which momentum, not velocity, is the dependent variable. It appears that the momentum formulation may give more reliable results, such as in situations where layer thicknesses tend to zero because of layer interfaces intersecting the top or bottom of the fluid domain. This approach may also be valuable in modeling vertical transport in the ocean. Non-oscillatory or nearly non-oscillatory advection algorithms will be used to solve the momentum equation. Such methods will be analyzed and incorporated into a two-level time-stepping algorithm that the investigator has recently developed for formulations of the governing equations in which the fast and slow time scales are split into separate subsystems. The resulting algorithms will be tested on model problems for which the solution behavior is known. As time permits, the PI will then pursue the implementation and testing of these methods in existing, operational models of ocean circulation. During this project the PI will be in regular contact with ocean modelers at Oregon State University and at Los Alamos National Laboratory.The long-term objective of this work is to contribute to an understanding of the global climate system. An important tool towards understanding this system consists of computer simulations involving coupled models of the atmosphere, ocean, sea ice, and terrestrial effects. With such simulations one can test the response of the earth's climate to changes in external forcing, such as increased emissions of greenhouse gases. The world's oceans store and transport tremendous amounts of heat energy, so the oceans play a crucial role in our climate system. When the circulation of the ocean is simulated on a computer, one is using the computer to obtain approximate solutions to mathematical equations that describe the evolution of fluid flows. The goal of the present project is to improve the methods that are used to solve those equations.

该项目的目标是为一般海洋环流的分层(等密度)模式开发数值方法。在这样的模型中，垂直坐标不是线性距离，而是势密度或其他一些相关的量。当在垂直方向上离散等轴面模型时，其效果是将海洋表示为一堆近似不相容的层。这与海洋的上部和下部区域在热力学上大致相互隔离的观察结果相一致。然而，这种隔离是不完全的，在等叶模型中，确实发生的交换是在建模者的控制下进行的。这种类型的模型在描述海洋动力学的长期行为方面显示出巨大的前景。在本项目中，首席研究人员将开发和合并以流量形式解动量方程的方法，对于该流量形式，动量而不是速度是因变量。动量公式似乎可以提供更可靠的结果，例如，在由于层界面与流体区域的顶部或底部相交而导致层厚度趋于零的情况下。这种方法在模拟海洋中的垂直传输方面也可能是有价值的。动量方程的求解将采用无振荡或近无振荡的平流算法。这些方法将被分析并纳入研究人员最近为建立控制方程而开发的两级时间步进算法中，在该算法中，快时间尺度和慢时间尺度被分成不同的子系统。所得到的算法将在解的行为已知的模型问题上进行测试。在时间允许的情况下，PI将继续在现有的海洋环流业务模型中实施和测试这些方法。在该项目期间，国际海洋研究所将与俄勒冈州立大学和洛斯阿拉莫斯国家实验室的海洋模型专家保持定期联系。这项工作的长期目标是促进对全球气候系统的了解。理解这一系统的一个重要工具是计算机模拟，它涉及大气、海洋、海冰和陆地效应的耦合模型。通过这样的模拟，人们可以测试地球气候对外力变化的反应，例如温室气体排放的增加。世界海洋储存和运输了大量的热能，因此海洋在我们的气候系统中起着至关重要的作用。当在计算机上模拟海洋的循环时，人们使用计算机来获得描述流体流动演变的数学方程的近似解。本项目的目标是改进用于求解这些方程的方法。