近常定有限振幅斜压Rossby波的激发与选择性衰减和不相容两原理

EXCITATION OF NEAR STEADY FINITE-AMPLITUDE BAROTROPIC ROSSBY WAVE AND TWO PRINCIPLES OF THE SELECTIVE DECAY AND NO-COEXISTENCE

摘要:

在斜压准地转两层流体的动量、能量和环流给定时,使用变分法,首次求得斜压流体最小位涡拟能解,此解正是斜压近常定有限振幅准确解。当通道长宽比、流体平均深度和能量三者都大于各自的临界值,且环流无垂直切变时,此准确解为有限振幅斜压Rossby波,否则,此准确解为纬向流。本文还首次提出“不相容原理”,即斜压大气有限振幅近常定Rossby波的正压和斜压两分量全波数不能相同。这表明这两种近常定波具有相当不同的水平和垂直结构,与观测事实和数值试验结果一致。

关键词:不相容原理;选择性衰减;有限振幅斜压Rossby波;常定

Abstract:

When the momentum,energy and circulation of a fluid in a quasi-geostrophic baroclinic two-layer model are specified,the minimum enstrophy solution of the baroclinic fluid is first obtained by the variation method,and is none other than an exact one of nearly steady baroclinic finite-amplitude problems.If the ratio of length to breadth of the channel,the average depth of fluid and the energy are greater than their critical values respectively, and the circulation is of no vertical shear,the exact solution is the finite amplitide baroclinic Rossby waves;otherwise it is the zonal flows.″principle of no-coexistence″is first proposed meaning that all wavenumbers between the barotropic and the baroclinic components of nearly steady finite amplitude Rossby wave in the baroclinic atmosphere are not the same,This indicates that two kinds of nearly steady waves have quite different horizontal and vertical structures,results that agree with observational facts and outcome of numerical experiments.

Key words:principle of no+coexistence;selective decay;finite+amplitude;baroclinic finiteamplitude Rossby wave;near steady