共查询到17条相似文献，搜索用时 250 毫秒
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切变基本纬向流中非线性赤道Rossby长波 总被引：5，自引：1，他引：4
为了解决观测和理论研究中的一些问题以及更好地了解热带大气动力学 ,有必要进一步研究基本气流的变化对大气中赤道Rossby波动的影响 .本文研究分析基本气流对赤道Rossby长波的影响 ,利用一个简单赤道 β平面浅水模式和摄动法 ,研究纬向基本气流切变中非线性赤道Rossby波 ,推导出在切变基本纬向流中赤道Rossby长波振幅演变所满足的非线性KdV方程并得到其孤立波解 .分析表明 ,孤立波存在的必要条件是基本气流有切变 ,而且基流切变不能太强 ,否则将产生正压不稳定 . 相似文献
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行星波传播理论虽然已有很多研究,但是大多以纬向对称基流为主,无法解释东西风带之间相互作用的事实.鉴于此,本文从理论上系统讨论了纬向对称和水平非均匀基流中定常和非定常波动的传播特征.首先,对纬向对称基流中波动传播的周期特征进行分析后发现,西风中位相东传超长波周期大于30 d,而东风中位相西传超长波的周期则小于30 d.之后,从传播的空间以及周期特征等方面系统研究了水平非均匀基流中球面波动传播理论,得到以下结论:经向基流使得定常波可以穿越东风带,在南北两半球间传播,为东西风带之间的相互作用提供了理论解释;强的经向流使得波动传播具有单向性;亚澳季风区低层纬向1波呈低频特征. 相似文献
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热带斜压大气的适应运动和发展运动 总被引：6，自引：1，他引：5
研究了热带斜压大气中的适应运动和发展运动 .当以重力惯性波为特征的适应过程基本完成后 ,运动进入缓变的发展或演变阶段 .发展运动可以是纬圈半地转平衡的 (即长波近似的Gill模式 ) ,也可以是经圈半地转平衡的 (短波近似 ) .分析了这两种半地转发展模式的特点后 ,提出了低频近似的发展模式 .在低频动力系统中 ,包括了除重力惯性波外 ,由Mastuno指出的所有热带基本运动 ,即Kelvin波、Rossby波和混合波中的Rossby短波 .因此 ,这个模式能反映热带运动更多的动力学行为 . 相似文献
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除介质各向异性之外,地球内部介质的横向非均匀性也是控制面波速度变化的重要因素.本文基于振型耦合和多重散射的地震波传播理论,数值模拟并分析了在具有均匀介质背景的三维异常体——上地幔横向非均匀介质中传播时,地震面波的振幅与偏振等动力学响应参数;其中分别模拟了不同周期入射、不同角度入射和不同尺度非均匀介质模型等多种情形下面波波场,并对横向非均匀性诱导的面波偏振异常进行了分析.结果表明,相对于长周期面波而言,短周期面波的振幅和偏振方向受横向非均匀性的影响更大,特别是偏振方向对地球结构的非均匀性更为敏感;切向分量存在横向非均性引起的Rayleigh与Love面波耦合现象;异常体边界处表现出强的面波波场响应. 相似文献
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研究了在中高纬度下考虑推广的β平面,研究了基本气流具有弱切变的非线性正压Rossby波,得到了偶极子阻塞形成的一个理论及其影响的问题.采用多重尺度法的方法,获得了Rossby波包满足非线性Schr9dinger方程的结果,通过δ效应对波包的波数产生影响,从而对Rossby的频率产生影响.指出:当Rossby波的波数满足k~2/3-Fm~24k~2+4/3F(k为纬向波数,m为经向波数)时,大气中周期Rossby波可以产生调制不稳定,形成包络Rossby孤立波.由于δ效应会对波数产生影响,推广了大气阻塞理论的结果. 相似文献
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The dynamics of solitary Rossby waves (SRWs) embedded in a meridionally sheared, zonally varying background flow are examined using a non-divergent barotropic model centered on a midlatitude g -plane. The zonally varying background flow, which is produced by an external potential vorticity (PV) forcing, yields a modified Korteweg-de Vries (K-dV) equation that governs the spatial-temporal evolution of a disturbance field that contains both Rossby wave packets and SRWs. The modified K-dV equation differs from the classical equation in that the zonally varying background flow, which varies on the same scale as the disturbance field, directly affects the disturbance linear translation speed and linear growth characteristics. In the limit of a locally parallel background flow, equations governing the amplitude and propagation characteristics of SRWs are derived analytically. These equations show, for example, that a sufficiently large (small) translation speed and/or a sufficiently weak (strong) background zonal shear favor transmission (reflection) of the SRW through (from) the jet. Conservation equations are derived showing that time changes in the domain averaged amplitude ("mass") or squared amplitude ("momentum") are due to zonal variation in both the linear, long-wave phase speed and linear growth; dispersion and nonlinearity do not affect the "mass" or "momentum". Provided (1) the background PV forcing is sufficiently small, or (2) the background PV forcing is meridionally symmetric and the disturbance is a SRW, the dynamics of the disturbance field is Hamiltonian and mass and energy are thus conserved. Numerical solutions of the K-dV equation show that the zonally varying background flow yields three general classes of behavior: reflection, transmission, or trapping. Within each class there exists SRWs and Rossby wave packets. SRWs that become trapped within the zonally localized jet region may exhibit the following behaviors: (1) an oscillatory decay to a steady state at the jet center, (2) the creation of additional SRWs within the jet region, or (3) a steady-state wherein the solution has a smoothed step-like structure located downstream along the jet axis. 相似文献
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考虑了经向风应力和纬向风应力联合作用下热带大洋的响应问题.结果表明,只有一阶的经向风应力或具有辐合辐散的经向风应力才对最后的速度场和位势场造成影响.零阶的扰动温跃层和纬圈流受风应力的直接驱动和Kelvin波、Rossby短波的影响,而Rossby短波由经向风应力直接造成;二阶模则受风应力的直接驱动和Rossby短波的作用,同时经向风应力也产生了附加的Rossby短波.另外,在西边界处存在很强的暖水补充到赤道的现象,经向风应力有使暖水向赤道输送的作用,而西风应力使西边界处的暖水向东输送. 相似文献
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In tropical areas, when the zonal or meridional geostrophic equilibrium is destroyed, inertial gravity wave will be excited
by ageostrophic motion, with the dispersion of the wave, a new zonal or meridional geostrophic balance will be established
again, and it follows an invariant of semi-potential vorticity. Based on the invariant, it should be pointed out that the
direction of the zonal or meridional semi-geostrophic adaptation depends mainly upon the meridional characteristic scale of
initial disturbance. For the zonal (meridional) semi-geostrophic adaptation, if the zonal characteristic scale of initial
disturbance is big (small) enough, then the adaptation process always represents the mutual adjustment between the pressure
field and zonal (meridional) flow. 相似文献
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Fanbing Xue 《中国科学D辑(英文版)》1998,41(6):586-591
In consideration of the characteristics of spectral average of the Rossby wave trains and the adoption of a climatic mean
stream field as the basic stream field, an approximate analytical formula for the period of atmospheric low-frequency oscillation
(LFO) and the group velocity is deduced from a barotropic and non-divergent linearized vorticity equation. All the action
centers of atmosphere are found to be the oscillators of low frequency. The LFO propagates southward across the streamlines
in the wind field with a southward component or propagates northward across the streamlines in the wind field with northward
component instead of along a great circle. The switch of the propagation direction takes place near the top of ridge or the
bottom of trough. The angle between the wave rays and the zonal direction can be determined.
Project supported by the National Natural Science Foundation of China (Grant No. 49175241). 相似文献
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Conservation laws of wave action and potential enstrophy for rossby waves in a stratified atmosphere
David M. Straus 《Pure and Applied Geophysics》1983,121(5-6):917-946
The purpose of this article is to discuss the evolution of wave energy, enstrophy and action for atmospheric Rossby waves
in a variable mean flow. The presentation is theoretical, but does not represent original research; rather, it is pedagogic
in nature. The work of a number of people has been drawn together into a unified account, with much of the algebra implicit
in previous work made explicit here. The central results are that wave energy is conserved only when there are no spatial
variations in the mean flow, and wave action is conserved even in the presence of such variations as long as they are not
in the longitudinal direction. Finally, wave enstrophy is conserved in the presence of arbitrary (slow) mean flow variations. 相似文献