登陆台风对安阳降水的影响及其预报

在分析1966－1995年安阳区域夏季登陆台风的不同环流形势基础上，利用历史天气图资料及安阳区域实况要素资料，找出台风登陆后安阳区域产生的不同天气的预防指标，并分类建立了预报方程。     

基岩振动干扰下的动力滑坡机制研究

本文通过对边坡基底岩石振动因素的分析, 建立了单一滑面滑体受基底岩石强迫振动的模型, 采用非线性动力学方程描述滑体的变形规律, 分析了基底岩石振动过程中导致滑体移动的原因。指出在一个频带范围和力幅范围内, 基底的振动, 会引起潜在滑体位移突跳, 在滑面的法向方向上张开, 切向上错动而诱发滑坡。     

FURTHER STUDY ON THE PROPERTIES OF OPERATORS OF ATMOSPHERIC EQUATIONS AND THE EXISTENCE OF ATTRACTOR*

The equivalent operator equation is derived from the full primitive nonlinear equations of the atmospheric motion and the properties and physical senses of the operators are studied.In the infinite dimensional Hilbert space,the global asymptotic behavior of the atmosphere system with the non-stationary external forcing is studied under the assumption of the bounded external forcing.The existence theorems of the global absorbing set and the global attractor are obtained.Thus,the conclusions deduced from the large-scale atmosphere(Li and Chou 1996a;1996b) are extended to the general atmosphere.     

Fundamental solutions to Helmholtz's equation for inhomogeneous media by a first-order differential equation system

Helmholtz's equation with a variable wavenumber is solved for a point force through use of a first-order differential equation system approach. Since the system matrix in this formulation is non-constant, an eigensolution is no longer valid and recourse has to be made to approximate techniques such as series expansions and Picard iterations. These techniques can accommodate in principle any variation of the wavenumber with position and are applicable to scalar wave propagation in one, two and three dimensions, with the latter two cases requiring radial symmetry. As shown in the examples, good solution accuracy can be achieved in the near field region, irrespective of frequency, for the particular case examined, namely a wavenumber which increases (or decreases) as the square root of the radial distance from source to receiver. Finally, the resulting Green's functions can be used as kernels within the context of boundary element type solutions to study scalar wave scattering in inhomogeneous media.     

Experiments with Higdon's absorbing boundary conditions for a number of wave equations

Simulation of wave propagation for seismic purposes is usually restricted to a small portion of the earth. Artificial boundary conditions are required where the subsurface model is truncated. Absorbing boundaries should ensure that waves hitting the artificial boundaries are not reflected. The vast amount of literature on the subject suggests that “good” conditions have not been found, and only “reasonable” solutions exist. A cursory overview of existing and a few new ideas is presented that may guide the construction of suitable boundary conditions. Because the intended application of the boundary conditions was a high-order finite-difference code that runs on a parallel computer, we have restricted our attention to local boundary conditions. A fundamental problem in the design of accurate local boundary conditions is pointed out: accuracy is required to keep the amount of reflected energy small, but at the same time allows for growing low-frequency modes. We have settled for Higdon’s boundary conditions. Higdon proposes to include some damping to suppress the growing low-frequency modes. We show that third-order conditions provide acceptable results for the simple scalar wave equation and the acoustic equation. In the elastic case, an additional low-frequency growing mode may occur. This mode can be suppressed by using a dissipative boundary scheme and by increasing the amount of damping. The increase in damping results in an increase in the amount of reflected energy, which is larger than in the scalar case. Numerical experiments exhibit a reasonable performance, although some improvement would be useful, particularly in the anisotropic elastic case. This revised version was published online in July 2006 with corrections to the Cover Date.     

悬浮泥沙遥感定量的统一模式及其在珠江口中的应用

本文推导出来悬浮泥沙遥感定量的统一式,其形式包含了Gordon关系式和负指数关系式,其它各悬浮泥沙的关系式可看作是该统一式的近似。由多个例子的计算表明统一式的相关性和精度要高于目前国内外使用的悬浮泥沙定量的遥感模式。该统一式被成功地应用于珠江口伶仃洋的遥感定量分析中。     

地震反问题研究评述

本文分析了地球物理反演问题在古典提法下存在的固有缺陷,继而讨论波动方程反问题的研究进展,然后讨论地震层析成象和偏移问题,最后对当前研究中存在的问题及发展方向作一评述.     

地震活动的自组织和演化

通过余震活动资料,说明了地震活动中的自组织行为和分形现象.对于地震断裂系统,利用地震频度作为序参量,并应用绝热消去法建立了代表地震活动演化规律的序参量所满足的主方程.通过主方程的解,很好地解释了一次大地震过程中可能出现的各种地震活动现象和有序性变化.像许多物理系统一样,包括大地震震源在内的地震断裂系统,在临界点处涨落会自行扩大并对系统状态的突变起着举足轻重的作用.同时,要注意系统内部不可预测的行为,正确对待地震的预测和预报的含义.     

LOCAL POTENTIAL AND PRINCIPLE OF VORTICITY CONSERVATION

In this paper,the local potential of nondivergent flow on beta plane is derived from the motion equa-tion.The conservation principle for vorticity is obtained when the local potential tends to be minimumwith the variational technique.Some other properties st,ch as Lagrangian of vorticity equation,energyetc.are also discussed briefly in the paper.     

N层模式大气中的斜压孤立Rossby波

文中导得了N层模式的KdV方程,作为例子计算了三层模式的孤立Rossby波流型。基本气流的垂直切变、水平切变和Froude数对孤波流型都有重要影响;不同模态的孤波具有不同流型,不同高度位面上的孤波流型一般是不同的。