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101.
基本流场切变对赤道长Rossby波的影响 总被引:9,自引:2,他引:9
文中应用赤道β平面近似 ,建立一个简单的斜压大气半地转模式 ,在热力学方程中引入表征基本位温场 (θ)经向分布特征的无量纲参数 σ,对线性化的扰动方程进行了频率分析 ,研究基本位温场经向非均匀分布以及基本气流垂直切变对赤道纬向超长尺度 Rossby波动的影响 ,并指出仅考虑基本气流垂直切变或者基本位温场变化的作用是不合适的。定性分析结果表明 :基本位温场经向温差必然有基本气流垂直切变与其相匹配 ,而基本气流垂直切变将导致赤道长 Rossby波动不稳定并影响其纬向传播速度 相似文献
102.
103.
Srinivas R. Mehta A. J. Graduate Research Assistant. Coastal Oceanographic Engineering Department University of Florida. Gainesville. FL . U. S. A. Professor Coastal Deeanographic Engineering Department. University of Florida. Gainesville. FL U. S. A. 《国际泥沙研究》1990,(1)
I. INTRODUCTIONPrediction of mud bed erosion by forcing due to tidal currents usually requires a numerical solution of the advection--dispersion equation for sediment mass transport. Key role is of course played inthis by the bottom boundary conditions defining erosion and deposition fluxes. The issue of erosion isbriefly considered here. noting that it is customary to calculate the rate of erosion as a function of thebed shear stress in excess of the erosion shear strength of the bed (Me… 相似文献
104.
Weakening of a prestressed sawcut in Westerly granite under laboratory condition is accomplished by injecting pressurized fluid into the sawcut. After injection a sequence of stick-slips is observed while the deviatoric stress decreases successively with each stick-slip. On the basis of the experimental observation we develop a model of fault instability due to inhomogeneous and progressive weakening of the fault. According to this model, the fault surface is divided into the slipped and the locked regions, depending on whether or not the local state of stress satisfies the friction criterion. The average shear stress in the slipped region decreases with time and, in order to maintain a quasi-static equilibrium, shear stress in the remaining locked region on the fault surface increases. This situation may last until a critical state of stress on the fault is met, at which a sudden instability (stick0slip) may occur. We suggest that this mechanism of stress transfer may be a viable mechanism of induced seismicity and aftershocks, in addition to the well-known mechanism of a local increase of pore pressure. By comparing the experimental data with model predictions we show that the critical condition for slip instability is when the average shear stress over the locked region becomes equal to the value given by the friction criterion. Thus the friction criterion established for slip on fractures on which the state of stress is macroscopically uniform may also be applicable to fractures on which the stress state is macroscopically heterogeneous. 相似文献
105.
本文研究了地球磁尾等离子体片边界层内由离子束流和等离子体密度梯度联合作用产生的静电不稳定性.模型等离子体由向尾流动的冷离子束流、向地球流动的暖离子束流和背景暖电子组成,等离子体密度是非均匀的,等离子体β(热压强与磁压强之比值)很小,电子等离子体频率与电子退旋频率之比。ωe/Ωe》1.结果表明,斜传播的静电快、慢离子束流-密度漂移模能够被激发。 相似文献
106.
利用常规气象观测资料、陕西区域自动站观测资料、NCEP 1°×1°再分析资料和卫星雷达探测资料,对2012年8月13日关中西北部一次短时强降水过程的成因进行动力学诊断分析,结果表明:在有利于触发中小尺度系统发生及其发展的条件下造成了本次短时局地强降水,雨区环境大气为低层对流不稳定、中层条件对称不稳定、高层对流不稳定的混合型不稳定层结。从卫星和雷达资料分析显示强降水过程是两个不同的中小尺度系统造成,前期是中β尺度干线、辐合线触发带状对流性降水,后期是中β尺度Ω系统触发圆形状对流性强降水。短时强降水雷达反射率因子呈低质心结构,具有热带降雨型特征。 相似文献
107.
本文根据Hoskins所提出的惯性重力波不稳定判据:Ri<f/ζa,结合湿斜压大气的特点,对1996年6月29日02时发生在我国东部的一次降水过程进行了分析,得出了下列特征:西南低空急流是降水得以产生所需水汽的载体;对流层下部深厚不稳定层结是对流性降水所必须的热力层结条件;该地区对流层下部满足Rise<f/ζa,6h后该地区惯性重力波不稳定增长。在充足水汽条件下,该地区发生暴雨。 相似文献
108.
The problem of motions of charged particles or charged grains of matter in the field of two magnetic dipoles in rotation about a common center are studied by means of computing families of periodic solutions and their stability. Ten such families are found and their stability study shows that only two out of the ten have short arcs of stable members, all with low inclination to the plane of the two dipoles, while the rest of the families consist exclusively of unstable solutions. Hence the impact of adding one dipole to the configuration of the Störmer problem, leads to the conclusion that in the modified system the three-dimensional motions are basically unstable unlike those of the one-dipole case. The model magnetic field used in this study is a first approximation of the Z3model of the magnetic field of Saturn as computed from the Pioneer 11 and Voyager 1 and 2 measurements. 相似文献
109.
The behaviour of an axially pre-loaded cylindrical member of an offshore structure, hit by a supply ship, has been investigated. The effects of axial pre-loading on the dynamic properties of members, the extent of damage and propagation of dynamic instability in the tubular members have also been investigated. Numerical models have been validated using available experimental data from the literature although these are mostly static with no pre-loading. Axial pre-loading was found to change the dynamic characteristics of some cylindrical members quite dramatically while it had no significant effect on others. The study examined whether there was any change in the behaviour between local and global modes when the loading was dynamic rather than static. The effect of damping on the dynamic instability of axially pre-loaded tubes under lateral dynamic loads was also studied. It was observed that for some geometries the quasi-static response can be used to define the boundary between bounded and unbounded dynamic responses. The main contribution of this study, compared with previous investigations reported in the literature, is that both pre-loading and dynamic effects have been included. 相似文献
110.