Characteristics Of Chaotic Attractors In Atmospheric Boundary-Layer Turbulence

In this paper, the attractors of turbulent flows in phase space are reconstructed by the time delay technique using observed data of atmospheric boundary-layer turbulence, which include high resolution temperature, humidity andthree-dimensional wind speed measurements in Gansu province and Beijing, China. The correlation dimensions and largest Lyapunov exponents have been computed. The results indicate that all the largest Lyapunov exponents in different conditions of time, site and atmospheric stability are greater than zero. This means that the atmospheric boundary-layer turbulence system is really chaotic and has appropriate low-dimensional strange attractors whose dimension numbers range from 3 to 7 and vary with different variables (dynamical variables or non-dynamical variables) and atmospheric stability. Turbulent kinetic energy is first applied to reconstruct the attractor of turbulence, and is found to be feasible.     

Lyapunov 指数预报模式

考虑到系统在吸引子附近的演化行为是指数辐散的，我们把浑沌理论和统计原理相结合，提出了Lyapunov指数预报模式。个例试验的结果是令人满意的。     

地震道的非线性混沌反演——Ⅰ.理论和数值试验

全文以地震道反演的数值实验为例,根据混沌理论讨论了非线性地震反演的以下特性:1.对于带误差的地震数据和极其平滑的初始模型,逐次线性化的迭代过程产生的输出序列最终走向无序,这是非线性反演系统本身的特性决定的;2.迭代（非线性反演）系统是由Poin-care映的或系统方程描述的;3.可以根据地震反问题的特点,用多种不同的方法定义相应的Lyapunov指数,它们的数值和组合是非线性反演系统状态的有效指示;4.取决于系统参数的选取,发现在二维相空间有奇异吸引子的对应物.总之,从混沌理论的角度来研究纯数学的非线性地震反问题,可以揭示某些过去鲜为人知的内在规律性.本文为全文的上篇,主要讨论前两个问题,即理论和地震道反演数值试验结果.     

THE SIMULATION OF THE RELATION BETWEEN FRACTAL DIMENSION AND THE SPECTRUM OF TURBULENCE*

In this paper, we study the relation between the energy spectrum exponent of turbulence and fractal dimension, and give two empirical formulas.     

Prediction analysis of long-term memory effect for calamity gray series

Are human able to foresee the future? For thou-sands of years close attention has been paid to this issue. At the present day, in order to survive from competition and to predominate over the nature, hu-man抯 desire of forecasting things has become more and more intense. Compared to conquering space, more people yearn for being able to control the time. From ancient to the present, mankind always dream of contacting the past, governing the present and tran-scending the future. Recent years in…     

受多因素影响的水位流量关系单值化整编方法

对受洪水涨落率影响、下游支(干)流洪水顶托影响及人工水利工程影响的水位流量关系，提出了用计算机综合处理的校正因数一落差指数拟合法，较好地解决了水位流量关系单值化的问题，满足现行的《水文资料整编规范》要求，具有一定的推广价值。     

R/S分析及其在地震磁效应研究中的应用

将重标极差法（R／S，Rescaled range analysis）这一时间序列分析方法引入到地震地磁前兆观测资料的处理和分析当中，并应用该方法对陕西关中地区3个地磁台站在1996～1998年间Z分量观测数据进行处理。分析了地磁Z分量赫斯特指数变化与1998年1月5日泾阳肘。4．8地震的关系，发现地震前2～4个月地磁Z分量出现明显小于0．5的异常变化，背离了地磁场正常的长程相关趋势性增强的变化规律，预示了此次地震的发生。这些结果表明该方法能够挖掘出丰富的地磁前兆信息，在地震前兆观测资料的非线性处理中具有良好的应用前景。     

基于小波多尺度分析的奇性指数：一种新地震属性

传统的地震解释主要是观测地震振幅及相位的变化，但是地震振幅也会掩盖地下介质中真实的地质情况.在许多情况下，重要的地质信息可能是通过与振幅特征无关的奇异性参数来传递的.本文提出奇异性指数，即Hlder指数α（又被称为Lipschitz指数），可以作为一种新的地震属性，它能够准确反映数据中的奇点的位置和奇异性强度.Hlder指数α是对某一点上或某一点周围很小的范围内的奇异性强度的度量，大的α值表示低的奇异性（或高的正则性）.研究表明α可以作为一种自然的能够精确刻画地层边界的地震属性.本文根据这一思想，对合成和实测的地震数据进行了小波基础上的多尺度分析研究，结果表明由本文的算法得到的α提高了对地层边界划分的能力，而这些地层界面在传统的地震振幅显示则不明显.     

Effects of dam operation and land use on stream channel morphology and riparian vegetation

Dams are well known for influencing channel and vegetation dynamics downstream, but little work has focused on distinguishing effects of land use and channel responses to the impoundment. In this paper, we examined interacting effects of a dam and land use on downstream changes in channel morphology and riparian vegetation along an agricultural stream system in northern California. Measurements of planform channel morphology, vegetation area, and land use were mapped along multiple stream segments based on a chronological sequence of historical aerial photographs over a 34-yr period prior to operation of the dam in 1983 and over a 17-yr period after dam operation, and compared to a nearby, undammed reference stream. A two-factor analysis of covariance (ANCOVA) was used to examine the effect of the dam on changes in bankfull area, stream length, and riparian vegetation area while accounting for the effect of land use and distance downstream. The dammed stream's bankfull area contracted 94% after dam operation. Prior to dam operation, bankfull area decreased when land use area increased, but not after operation of the dam. Stream length varied 64% less after dam operation as a consequence of less frequent episodic channel migration and entrenchment. The area of riparian vegetation was decreasing during the pre-dam period, but then increased 72% after operation of the dam. Across time periods, decreases in the area of riparian vegetation were also associated with increases in land use area in both the dammed and reference stream. After operation of the dam, reduced peak discharges and sediment reduction likely lead to channel incision and constrained channel migration, which allowed vegetation to increase 50% on less accessible, abandoned banks. Rating curve and hydraulic exponent analyses based on stream gauge measurements corroborate statistical analyses of the mapped changes. In conclusion, we found that operation of the dam and land use patterns together influenced spatial and temporal changes in channel morphology and riparian vegetation. Use of a nearby undammed reference stream in conjunction with multivariable analysis of spatially and temporally replicated observations provided an effective framework for unraveling interacting effects of dams and land use activities on stream channel and vegetation dynamics.     

On the characterization of aerosols using the Ångström exponent in the Athens area

Ground-based spectroradiometric measurements were taken in the atmosphere of Athens during May 1995 in order to investigate various atmospheric conditions. This study focuses on the Ångström exponent α, which is the slope of the logarithm of the aerosol optical depth (AOD) versus the logarithm of the wavelength, lnλ, and is commonly used to characterize the wavelength dependence of AOD and to provide some basic information on the aerosol size distribution. Using the Volz method, Ångström exponent values, α, were derived in five narrow spectral bands, 340–380, 380–440, 440–500, 500–670 and 670–870 nm. Also using both Volz and least-squares fit methods α values were derived for the whole spectrum 340-870 nm.The results show that α depends strongly on the wavelength interval used due to the curvature of the lnAOD versus lnλ line. Using the spectral dependence of the Ångström exponent and the relationship between α computed in different spectral bands with AOD, an attempt to investigate on the aerosol types is made. The results obtained are rather contradictory and the determination of a dominant aerosol type in the Athens area is not clear. Nevertheless, in the most cases the anthropogenic aerosols seem to be the dominant type with rather significant contributions of coarse-mode particles due to particle growing or due to mixing processes with other aerosol types.