基于大涡模拟和局部滤波同化方法的海洋环流模式

A large eddy simulation turbulence model and a local filtering assimilation method for ocean circulation problems

结合最小二乘法极值原理,提出了一种基于局部谱展开的滤波同化方法,把测量数据和数值计算过程中出现的高频短波滤掉,并将高度计数据同化到了求解过程中.结果既增加了数值稳定性,又提高了数值模拟的准确性.针对在海洋环流问题中水平的流动性质和垂直的不同的特点,我们还将大涡模拟的思想和直接涡黏的思想分别应用于水平方向和垂直方向,给出的方法是一种适用于海洋环流和浅水环流问题的大涡模拟湍流模式.对热带和北太平洋一年四季非定常季风作用下环流的数值模拟表明,提出的方法非常有效,数值结果与实际相当吻合.

A local spectral filtering expansion method is proposed, which is a data assimilation method. Using this method, the high frequency waves in computation and measurement can be filtered. TOPEX/Poseidon altimetric sea surface height (SSH) data are assimilated into a large eddy simulation model to drive the circulation of the tropical and north Pacific Ocean. With data assimilation, the root mean square method is used to estimate optimizing data between the simulated SSH field and the observed SSH field. In large scale motions of circulations in coastal seas and shallow-water problems, different characteristics of flow on the horizontal plane and in the vertical direction are expected. A new large eddy simulation model (LES) is proposed. There are some differences between the present method and the other LES models. The philosophy of the large eddy simulation and the directional eddy viscosity method are applied to the horizontal plane and to the vertical direction, respectively. Comparing with the other LES models in which there is no difference between horizontal viscosity and vertical viscosity, the proposed method is more reasonable. Numerical results agree very well with the observed results.