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A study of abyssal circulation based on the expansion in terms of vertical modes incorporating density diffusion

基于结合密度扩散的垂直模式扩展的深海环流研究

基本信息

批准号：
02640314
负责人：
MASUDA Akira
金额：
$ 0.96万
依托单位：
KYUSHU UNIVERSITY (1991-1992)The University of Tokyo (1990)
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1992
项目状态：
已结题

项目摘要

The purpose of this project is to clarify the basic dynamics of abyssal circulation by expanding the field in terms of vertical modes and investigating the behavior of each mode.Incorporating both vertical and horizontal diffusion of density makes the obtained model comparable directly with ordinary three-dimensional numerical experiments.In our model,deep western boundary layers can be either in viscous or in diffusive regimes, depending on the stratification and latitudes.Higher modes,for which horizontal diffusion works strongly,tend to have broad diffusive western boundary layers.In the poleward flowing(equator-ward) western boundary layer,deep water upwells(downwells),while the opposite sign of vertical flow is found in the narrow layer adjacent to the western coast.By virtue of density diffusion,deep water can downwell near boundaries and even in interior regions.The structural change of boundary layers and associated appearance of downwelling were explained well in terms of a new concept of diffusion of(the thickness term of)potential vorticity, which applies as well to surface layers of stratified oceans.In an extended model,effects of isolated bottom topography on abyssal circulation were investigated. In particular,by including dissipative terms,we determined the field inside the geostophic island,which had been beyond the scope the characteristic method.A direct method was developed to solve higher modes efficiently.It was used to investigate the vertical structure of ocean circulation.

本项目的目的是通过扩展垂直模式的场并研究每种模式的行为来阐明深海环流的基本动力学。考虑密度的垂直和水平扩散使所得到的模式可以直接与普通的三维数值试验相比较。在我们的模式中，深海西部边界层可以是粘性的也可以是扩散的。取决于层结和纬度。较高的模式，水平扩散工作强烈，往往有广泛的扩散西部边界层。在向极流动（赤道方向）西部边界层，深水上升流（下井），而垂直流的相反符号出现在靠近西海岸的狭窄层中。由于密度扩散，本文用位涡（厚度项）扩散的新概念很好地解释了边界层的结构变化和伴随的下沉现象，它也适用于分层海洋的表层。在一个扩展模式中，研究了孤立海底地形对深海环流的影响。特别地，通过引入耗散项，确定了特征线法无法解决的地气岛内部的场，发展了一种直接法，有效地求解了高阶模态，并将其用于研究海洋环流的垂直结构。