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排序方式: 共有9543条查询结果,搜索用时 15 毫秒
941.
942.
943.
Quasi-shear wave coupling in weakly anisotropic 3-D media 总被引:2,自引:0,他引:2
944.
本文以能量和波函数的各级微扰近似的基态展开式为基础,推导出任一力学量的矩阵元F_(mn)的各级微扰近似表示式。并且指出只要构成能量展式的级数收敛很快,满足能够应用微扰的条件,那么对于任一力学量F的微扰计算,只要计算矩阵元F_(mn)的前二级近似就已足够精确。 相似文献
945.
ANALYSES OF THE DYNAMIC EFFECTS ON WINTER CIRCULATION OF THE TWO MAIN MOUNTAINS IN THE NORTHERN HEMISPHERE——Ⅱ.VERTICAL PROPAGATION OF PLANETARY WAVES 下载免费PDF全文
A linear,hemispheric and stationary spectral model with multilayers in the vertical was employed to simulate thevertical propagation of waves triggered by mountains.Results show that,in cooperation with the East Asia zonal meanflow,Tibetan Plateau can excite a strong wavenumber 1 perturbation in the stratosphere with its ridge and trough lo-cated over the Pacific and Atlantic Oceans respectively.On the other hand,the stratospheric wavenumber 1 perturbationcaused by the mechanical forcing of the Rocky Mountains in cooperation with the North America zonal mean flow isvery weak.Calculations from observational data of the vertical profile of critical wavenumber for vertically propagatingwaves imply that the tropospheric wavenumber 1 perturbation can hardly penetrate the North America tropopause up-wards,whereas it can freely propagate through the East Asia tropopause into the stratosphere.Two-dimensional E-Pcross-sections obtained from both observational data and simulated results also demonstrate that waves excited by theRocky Mountains are refracted towards low latitudes in the troposphere during their upward propagation:whereas,inaddition to the above mentioned equatorward leaning branch,the wavenumber 1 and 2 planetary waves excited by theTibetan Plateau possess another branch which is refracted to high latitudes during upward propagation and penetratesthe tropopause into the stratosphere.It is therefore concluded that the difference in the horizontal and vertical wavepropagations in the two hemispheres is a result of the different dynamical forcing induced by the two main mountains inthe Northern Hemisphere. 相似文献
946.
The wave rays and their seasonal variation of stationary and low-frequency Rossby waves are studied by using the Runge—Kutta
scheme. The results show that for stationary waves the rays can reach lower latitudes in winter, and are limited in higher
latitudes in summer. The main differences between the stationary and low-frequency wave rays are that low—frequency waves
can propagate across the equator and the easterlies will not be an obstacle on their propagation. It explained to some extent
the interaction of disturbances between the Northern and Southern Hemispheres. The lower wave frequencies and the stronger
easterly flow are, the more difficult low—frequency waves will be to propagate across the equator. The waves with 20-day period
are easier to propagate across the equator than that with 50—day period. The winter is the most favorable season for low—frequency
waves to propagate into another hemisphere. 相似文献
947.
948.
The propagation features of extremely low frequency electromagnetic waves through the multicomponent ionospheric plasma are studied. It is shown that at relatively lower frequencies refractive index for right hand mode is higher than the left-hand mode, which is reversed at higher frequencies. The thermal temperature of plasma particle causes decrease in phase and group velocities of both right and left-hand modes. The crossover frequencies for different plasma models are computed and variation with ion concentration and thermal velocity is studied. Explicit expression for group velocity and travel time has been derived and studied numerically. Finally, we have presented simulation of the ion whistler spectrograms for Hydrogen, Helium and Oxygen ions present in the ionospheric plasma. The results are compared with the experimentally detected hydrogen and helium ion whistlers. The importance of the present study in the exploration of ionospheric plasma is illustrated. 相似文献
949.
本文用微分方程定性理论方法分析了地形对有限振幅Rossby波的稳定性影响。结果表明:地形北坡有利于波动出现不稳定,南坡使波动稳定;西坡使导式波动不稳定但使曳式波动稳定,东坡使导式波动稳定但使曳式波动不稳定。 相似文献
950.