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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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The study concerns the propagation of easterly wave (EW) at tropics as west-moving soliton more steady both in ionn and velocity as evidenced in the dynamic framework.Under the impact of different circulation patterns over the regions of western Pacific trade wind,South-Asia monsoon and their transition,such a soliton becomes tapering off during its westward movement and degrading to a common dispersive wave on the whole,followed by dismtegra-non when striking the South-China Sea monsoon segment,thereby indicating that the sea sector is inaccessible to the soliton When no monsoon trough is present over the South Asian monsoon area around 30癗 or the monsoon depression ]S shallow,it is likely to have west-travelling soliton,which suggests the incursion of the EW into the South-Asian monsoon region. 相似文献
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β近似下,在等压面上的锋区可变换成孤立子.因此,为了了解锋面形成和维持的动力机制,本文从锋面方程组出发,设基态流场定常,利用地转动量假定及在平衡态附近按Taylor级数展开的方法,最后导出KdV方程。通过讨论,我们得出,锋面是由于非线性过程与频散过程共同作用并达到平衡而形成的,其中形变场对锋面形成是至关重要的.在线性情况下形成不了锋面.锋面移速与锋区强度、基态流场及非绝热加热等有关,而等压面上锋区宽度与锋面强度、切变场等有关,与形变场无直接关系.斜压性对锋面形成是必须的,而凝结加热也具有重要的辅助作用. 相似文献
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G.C. Das 《Planetary and Space Science》2004,52(7):581-586
It has been shown that the Korteweg-de Vries equation, derived in inhomogeneous plasma, finds difficulty in obtaining the complete soliton solution and its propagation in plasma and thus fails to exhibit the actual nature of plasma acoustic-wave. The key here lies in the use of an approach, known as sine-Gordon method, which describes successfully soliton propagation along with its precursor. The study shows that the soliton, due to the interaction of negative ions, collapses expecting a source of soliton radiation. Moreover, inhomogeneity, along with weak ionization, effects the precursor to grow faster by generating the energy from its main soliton. The results are interesting in the light of having a parallel observation on radiation, and the formation of dip and hump solitons as similar to those observations made by the scientific satellites. 相似文献
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