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纬向切变基流中的非线性正压Rossby波 总被引:2,自引:0,他引:2
在半地转近似下,用相角函数方法得到了包含纬向基流及其切变的非线性常微分方程。利用常微分方程解的拓扑性质的定性理论,直接得到该方程存在有限振幅的周期波解与孤立波解即非线性正压Rossby波解存在的条件,由此分析了纬向切变基流对波解存在的影响。最后利用函数逼近法求得了非线性正压Rossby波解的显式表达式。结果表明,纬向切变基流对波的影响不仅表现在波的存在方面,而且还表现在波的形态方面,反映了波的非线性特点和基流对波动的作用。 相似文献
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通过对二维准动量无辐散、无摩擦、密度非均匀分布的层结大气中基本气流切变对非线性方程组行波解的影响问题的研究,证明:(a)在对称稳定(q=N2F2-S4>0)的大气中:非线性行波解为周期解,且其周期与相应的线性周期解的周期相等;(b)在对称非稳定(q=N2F2-S4≤0)的大气中:存在两类非线性行波解,其性质是由参数B决定的。B=(N2sin2φ-2S2sinφcosφ+F2cos2φ)/σ2。(1)当B>0时为周期解,且其周期与相应的线性周期解的周期相等;(2)当B≤0时为孤立波解。 相似文献
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本第一部分,在一个简化的二层模式中,求解大气波动方程,得到了二维波状起伏地形上扰动流线的分析解,研究在上、下两层大气中,不同的温度廓线和风速廓线情况下,地形引起扰动流场形式,同时讨论了支配扰动振幅的大气因子和地形特征。章第二部分,利用大气非静力方程组求出几种大气条件下流场扰动的数值解,并和分析解做了比较。 相似文献
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本文利用Hamilton函数求得包含地形的半地转正压模式中存在有限振幅周期波解与孤立波解的条件,并给出了波解的解析式,得到一些有意义的结果。 相似文献
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陆维松 《南京气象学院学报》1995,18(2):155-165
在斜压准地转两层流体的动量、能量和环流给定时,使用变分法,首次求得斜压流体最小位涡拟能解,此解正是斜压近常定有限振幅准确解。当通道长宽比、流体平均深度和能量三者都大于各自的临界值,且环流无垂直切变时,此准确解为有限振幅斜压Rossby波,否则,此准确解为纬向流。本文还首次提出“不相容原理”,即斜压大气有限振幅近常定Rossby波的正压和斜压两分量全波数不能相同。这表明这两种近常定波具有相当不同的水 相似文献
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在计算机比较普及的今天,计算机时时被病毒困扰着,由于病毒经常攻击计算机,所以需要对计算机解病毒。在解病毒的过程中,产生一个免疫程序,如cpav.rpt,chklist.cps等等,这类程序占存储空间不大,一般几十bit到几kbit.在一般情况下,这么小的存储空间对程序无多大影响。但在一些存储满了的磁盘上,就会出现问题。如存储了较大字库的软磁盘,因一张软盘存储不下,需多张软盘存放,用backuP到几张软盘上。在这些软盘上,除最后一张软盘可能不满外,其余软盘都满的(0bitesfree)。在这种情况下,如果对这个软盘解病毒,就会在软盘后面… 相似文献
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William L. Briggs 《Dynamics of Atmospheres and Oceans》1980,4(2):67-99
Early studies of the wind-driven ocean problem were concerned with finding steady solutions of the equations of motion, first by analytic, and later by numerical methods. The problem is characterized by an Ekman number (?) and a Rossby number (α). Prior to this study, steady solutions were confined to the ranges α, ? < < 1.In this work the problem is considered in a circular domain with lateral friction and a partial-slip boundary condition. Steady solutions are found analytically in the new regime α > 1. Furthermore, for large enough values of ?, steady solutions are determined numerically in the intermediate range between this high-α regime and the classical low-α regime. That is, for some values of ?, steady solutions can be found through all values of α. Numerical evidence suggests that below a critical value of ?, steady solutions in this intermediate range exist, but cease to be stable. Similar results have been obtained with bottom friction and with different boundary conditions. 相似文献
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This survey is concerned with the new developments on existence and uniqueness of solutions of some basic mod-els in atmospheric dynamics, such as two-and three-dimensional quasi-geostrophic models and three-dimensional balanced model. The main aim of this paper is to introduce some results about the global and local (with respect to time) existence of solutions given by the authors in recent years, but others' important contributions and the literature on this subject are also quoted. We discuss briefly the relationships among the existence and uniqueness, physical in-stability and computational instability. In the appendixes, some key mathematical techniques in obtaining our results are presented, which are of vital importance to other problems in geophysical fluid dynamics as well. 相似文献
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Keith W. Ayotte 《Boundary-Layer Meteorology》1997,83(2):285-309
This paper describes an adjoint method for data assimilation intoupstream boundary conditions of numerical modelsusing optimal control theory. Mathematical formalisms are given along with the numerical implementation of the schemein a column model of the atmospheric boundary layer. The optimized mean and turbulence profiles are used as an upstream solutionin a model of turbulent flow in complex terrain. To contrast thiswith other methods, two solutions for flow over an isolatedhill are calculated, one with an optimized upstream solution andone with a simple surface-layer formulation for the upstream solution.These two solutions are compared to observations and analytical theory. The adjoint optimization method is shown to producesolutions of flow in complex terrain that are substantively differentat the two solutions, with the optimized solution giving more accurate results. 相似文献
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本文研究了斜压效应对地转动量Ekman流的影响。利用两变量奇异摄动方法求得了边界层中风场及顶部垂直速度的前二级一致有效渐近解析解,解中明显地反映了斜压情形地转风随高度变化(即热成风)的影响,尤其是其中一级近似解完全由热成风影响所致。在边界层顶垂直速度的解中导出了三种由斜压效应引起的Ekmon抽吸新物理因子,即热成风形变、热成风涡度及热成风涡度交叉项等抽吸因子。分析表明,这些因子只在具有水平温度梯度不均匀的系统(譬如锋区)中方能出现。文中还对锋区内上述三种抽吸因子的动力特征作了具体的分析,指出在锋区这样的强斜压系统中,此三种抽吸因子的贡献是显著的。下一文中,我们将利用本文所得理论解对斜压效应进行具体的定量计算。 相似文献
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The temperature and wind profiles in abaroclinic atmospheric boundary layer (ABL) are investigated.Assuming stationary conditions, the turbulent state in the ABL forstable and neutral conditions is uniquely determined by the Rossbynumber, the external stratification parameter and two externalbaroclinic parameters. A simple two-layer baroclinic model isdeveloped. It consists of a surface layer (SL) and overlyingEkman-type layer. The system of dynamic and heat transfer equations isclosed using K-theory. In the SL the turbulent exchangecoefficient is consistent with the results of similarity theorywhile in the Ekman layer it is assumed constant. The universalfunctions in the resistance, heat and humidity transfer laws arededuced from the analytical solutions for the wind and temperatureprofiles. The solutions of the ABL resistance laws for theinternal ABL parameters, necessary for the calculations of the ABLprofiles, are approximated in terms of the external ABLparameters. Favourable agreement of model results with theavailable experimental data is demonstrated. 相似文献
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Lu Weisong 《Acta Meteorologica Sinica》1989,3(1):90-97
Based on a non-frictional and non-divergent nonlinear barotropic vorticity equation and its solutions oftravelling waves,the criteria for linear and nonlinear barotropic instability are gained respectively at an equilibriumpoint of the equation on a phase plane.The linear and nonlinear analytical solutions to instability waves arealso found.The computational results show that if their amplitudes are equal at the initial time,the amplitudeincrements of nonlinear instable barotropic wave are always less than those of linear instable barotropic wave.The nonlinear effects can slow down the exponential growth of linear instability.The time needed for makingthe amplitude double that of initial time by instabilities,is about 6h for linear instability and about 18h fornonlinear instability,the latter is in agreement with the observations in the real atmosphere. 相似文献
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青藏高原大地形对冷涌作用的理论研究 总被引:5,自引:0,他引:5
本文从包含大地形效应的线性浅水波方程组出发,考虑青藏高原大地形为由西向东等科率倾斜,导得两类重力波解,一类是两个高频重力惯性波解,另一类是由地形激发的低频地形重力波解。后者与Kelvin波有某些类似之处。它们分别类似于数值试验所得冷锋迅速南下和冷涌强风速中心沿青藏高原大地形东侧边缘较慢向南传播的重力波。特别当无地形时,则低频波消失,仍有高频波。还求得了重力波波射线的传播路径为次摆线方程,这与数值试验所得冷涌强风速中心环绕青藏高原大地形东侧边缘的弧形路径颇为一致。且沿大地形下游沿海地区可能存在地形重力波波导管。 相似文献
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切变气流中地形强迫激发的非线性长波 总被引:1,自引:0,他引:1
经推导得到了包括地形和耗散的FKdV-Burgers方程,利用数值解讨论了地表强迫激发的弧波演变以及移动性孤波与地形的相互作用,结果显示,对于α〉0或α〈0,不论是在气旋式切变气流还是反气旋式切变气流中,地形都能在强迫激发出定常孤波,在其下游产生调制椭圆余弦波列的背风波,当α=0时,在反气旋式切变气流中强迫区产生的是大振幅定常孤波,气旋式切变气流中强迫区产生的是复杂的非定常孤波,地形强迫产生的m= 相似文献