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本文在半地转近似下讨论了纬向切变基流中的非线性正压Rossby波,给出了存在波解的切变基流条件。 相似文献
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线性和非线性地形罗斯贝波 总被引:1,自引:0,他引:1
本文在半地转概念下,讨论了线性和非线性地形罗斯贝波的稳定性及其解。指出:线性和非线性稳定性判据形式一致。在线性时,地形东西向及南北向坡度对稳定波动的周期和传播速度有明显影响,其解为周期函数;在不稳定时,解为非周期函数。二级近似时其解为孤立波形式——不稳定时,在地形不同位置可形成东移或西移的孤立波槽或孤立波脊;而在稳定时只形成孤立波槽。三级近似时解出现间断点。 相似文献
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D. W. Hughes 《地球物理与天体物理流体动力学》2013,107(1-4):99-142
Abstract Recent calculations suggest that the bulk of the solar toroidal field may be stored in a thin, convectively stable region situated between the convection zone proper and the radiative zone. Determining the stability properties of such a field is therefore important with implications for both the generation and escape of magnetic flux. The plane layer, linear stability analysis of Hughes (1985) is extended to incorporate the effects of uniform rotation. Detailed studies are made of interchange, or “axisymmetric” modes and of undular, or wavelike, motions, considering modes of both low and high frequency. The force due to rotation acts to constrain the fluid motions, a feature which is strongly stabilizing for direct modes, but can, in certain circumstances, be destabilizing for oscillatory motions. For the interchange modes we show that the instability discussed at length by Hughes (1985), driven by fields increasing with height, is still present and indeed may be enhanced by rotational effects. We also study the more conventional instabilities, discussing the transformation between direct and oscillatory modes and considering in detail some peculiar properties of the oscillatory instabilities. The more relevant instabilities in an astrophysical context are likely to be undular modes. Previous studies of low frequency modes driven by top heavy field gradients are extended to consider modes of various frequencies for a wide range of parameter values. Of particular interest is the occurrence of two distinct modes of instability for bottom heavy field gradients. We also exhibit some of the peculiar stability boundaries which can result when none of the competing influences in the problem is dominant. 相似文献
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在半地转近似[1]下,利用层结大气中的涡度方程、散度方程、连续方程和绝热方程结合行波解的方法得到了关于垂直速度的单一变量方程。这是与KdV方程相应的非线性常微分方程,可得到椭圆余弦波或弧立波。此波动的频率有两种,表明层结大气中存在着两种性质不同的非线性波动。其一是东传的惯性重力椭圆余弦波,另一是混合Rossby-重力椭圆余弦波,其性质介于Rossby椭圆余弦波与西传的惯性重力椭圆余弦波之间。这两种非线性波的相速不但与波数和振幅有关,而且与β因子和静力稳定度有关,即纬度越低,则传播越慢;大气越稳定,则传播越快。 相似文献
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A steady-state, spatial, large-scale, non-linear problemof the air massmotion along an undulating mountain ridge is consideredin the framework of bulktheory. The ridge is assumed to be so high that the airmass cannot top it, and, insteadof the actual ridge itself, a high vertical wall withsinuousities identical to those of theridge is considered. It is assumed that the air massis bounded above by an inversioninterface (idealized inversion layer) overlain by ageostrophic, polytropic, atmospherethat is thermally homogeneous along the horizontaland stably stratified with aconstant geostrophic wind blowing along the meandirection of the ridge. Theinversion strength (potential temperature deficit) isnot constant and considered as anadditional dependent variable. Because of the Earth'srotation effects, the air massflow to the left of the ridge and that to the rightof the ridge differ considerably intheir features. The fact that the characteristictransverse linear scale of the problem(the generalized Rossby radius of deformation) issmall compared with thelongitudinal scale permits making simplificationsthat result in a semi-geostrophicmodel of the boundary-layer type. Then the problemcan be reduced to an ordinarydifferential equation, which admits a closed-formsolution. Analysis of the solutionenables one to deduce some general features ofthe process under investigation suchas, for example, orographic front formation,a transition from sub-critical to super-criticalwind and others. 相似文献
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热带大气和海洋的半地转适应和发展运动 总被引:5,自引:2,他引:3
半地转适应和半地转发展是热带大气和海洋运动的两种基本形态,它们在时间上是可分的,反映了不同的物理过程。当初始扰动作用于大气或海洋时,首先将激发出重力惯性波,当重力惯性波频散后,建立起半地转的平衡状态,此后运动进入到以Rossby波(长波或短波)、Kelvin波和混合波中的Rossby短波为主导的发展状态。文中研究的纬圈半地转适应和发展运动,是Gill长波近似模式的理论基础。同时研究了经圈半地转适应和发展运动,实际上这相当于短波近似模式,它可以应用到研究海洋经圈边界附近的一类问题。 相似文献
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