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随机水文过程受到随机性和确定性因素的综合影响,其时间序列不仅具有反映遗传特性的纯随机成分,还含有反映变异特性的确定性跳跃、趋势、周期成分和随机性相依成分,使得随机水文过程表现出复杂的变化形态和演变规律.为了对上述复杂的变化形态和演变规律进行统一认识,本文从随机过程模拟和时间序列分析两个角度描述了非一致性水文序列的遗传和变异特性或规律,同时对非一致性水文频率计算途径进行比较,说明非一致性研究面临的主要问题.在此基础上,本文借鉴生物基因概念来定义水文基因,并分别利用常规矩、权函数矩、概率权重矩、线性矩等描述水文基因的构建和表达过程;同时定义跳跃、趋势、周期、相依和纯随机成分为构成水文基因的5种水文碱基,综合考虑非一致性水文序列的遗传成分和变异成分,并阐述其遗传、变异和进化原理,以揭示水文要素概率分布遗传、变异和进化的演变规律. 相似文献
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跳跃变异是环境变化影响下水文过程发生急剧变化的一种重要表现形式,体现了水文非线性系统对外界干扰的响应.目前研究主要是对序列跳跃变异发生的时间、次数等进行识别和检验,但缺乏对其变异程度进行定量描述和分级,给开展流域环境变化研究及其影响评价带来很大困难.本文选取相关系数作为基础指标,提出了一种理论严密且便于应用的水文序列跳跃变异分级方法,并利用统计试验验证了文中方法对变异点显著性的检验精度,以及跳跃变异分级原理的合理性和分级方法的可靠性.经推导相关系数与跳跃变异相对幅度的关系,选取不同显著水平下的若干典型相关系数值作为分级阈值,将跳跃变异程度划分为无变异、弱变异、中变异、强变异、巨变异5个等级.通过应用于分析我国不同气候区的5个实测水文序列,结合物理成因分析验证了该方法的实用性. 相似文献
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近年来由于受全球气候变化和频繁人类活动的影响,水文序列的纯随机成分叠加了跳跃、趋势、周期、相依中的任意一种或多种变异成分,急需明确采用何种指标度量它们变异的程度.本文定义了基于Hurst系数与Bartels统计量的水文变异度以衡量其变异程度,采用蒙特卡洛统计试验方法检验并分析了它们对不同变异成分的敏感性.结果表明: 当水文序列存在跳跃、趋势变异时,Hurst变异度和Bartels变异度均能反映其变异状况,但Hurst变异度对微弱的跳跃或趋势变异更敏感;当序列存在周期变异时,仅Bartels变异度能反映序列的周期变异程度;当序列存在相依变异时,Hurst变异度和Bartels变异度均能反映其变异程度,但Bartels变异度能反映更加微弱的相依变异程度;Hurst变异度、Bartels变异度均随着4种成分变异幅度的增大而增大,说明Hurst变异度、Bartels变异度可以衡量水文序列的变异程度.以澜沧江流域各气象站气温序列为例,发现各站气温出现了向上的趋势或跳跃变异,说明整个流域近年来出现了气候变暖的现象,且上、下游气温变异度更高,体现出本文所提方法的实用性. 相似文献
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非一致性水文频率分析是变化环境下工程水文计算需要解决的主要问题之一.本文从随机水文序列组成的角度,将不同时间尺度下的非一致性水文现象概化为具有遗传、变异与进化特性或规律的水文过程,据此借鉴生物基因理论提出水文基因的概念,并定义常规矩基因为水文序列的各阶原点矩和中心矩.为了识别与检验水文基因的各组成成分,创建了水文基因诊断系统.为了阐述水文基因的遗传、变异与进化原理,以P-Ⅲ分布为例详细描述了常规矩基因的构建与表达过程.以澜沧江流域允景洪站年最小1月流量序列为例,对上述基于常规矩基因的非一致性水文频率计算方法进行了可行性和实用性验证.结果表明: 该方法能以水文基因变异识别为基础,揭示非一致性水文序列的演变规律,不仅为变化环境下工程水文计算提供了新的研究途径,也能为水安全评价提供重要的参考依据. 相似文献
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全球气候变化和频繁人类活动导致水文序列的二阶矩变异现象日益凸显,样本的“一致性”内涵发生了变化,只考虑均值一阶矩变异的非一致性水文序列分析方法不再适用于所有的非一致性问题,基于样本一致性的传统最低通航水位综合历时曲线设计方法给枯水期低水位下的船舶通航带来了更大的安全隐患,使得最低通航水位更加不能满足航运设计需求.本文运用水文变异诊断系统分别检验水文序列的均值和方差二阶矩变异,在此基础上,结合时间序列的分解合成原理,提出枯水期非一致性最低通航水位综合历时曲线设计法.并以澜沧江流域的允景洪站为计算实例,比较分析现状与过去远期、过去近期不同时期的设计水位值,以及考虑二阶矩变异、仅考虑均值变异、未考虑变异3种不同情况下的设计水位值.结果表明: 方差变异成分改变了允景洪站设计水位值的变化趋势,并且与仅考虑均值变异的设计水位值的差值低至-1.11 m,与未考虑变异的设计水位值的差值低至-1.01 m,从而揭示了方差变异对设计水位的影响以及二阶矩变异分析在航道规划设计中的重要意义. 相似文献
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跳跃变异是全球气候变化背景下水文过程发生剧烈变异的重要表现形式,其准确识别对认识水文过程发生的变化及开展实际水文水资源工作具有重要意义.针对目前传统方法在样本两端有时检验结果不可靠、多种方法检验结果常常不一致等问题,本文通过对常用的12种变异点检验方法对比研究,基于赋权方式提出了水文跳跃变异综合加权识别方法,并利用Monte-Carlo统计试验验证了该方法的可靠性.结果表明: 12种跳跃变异检验方法的效率受变异点前变差系数(Cv)、变异点前偏态系数(Cs)、均值变幅系数、Cv变幅系数、Cs变幅系数等因素的影响较大,但与序列均值无明显关系.以各方法的性能差异为基础,基于统计试验结果对各检验方法赋予权重.其中,滑动秩和检验法和滑动游程检验法的权重最高,RS检验法的权重最低.通过赋权方式,可以在各方法检测结果不一致时选取综合权重最大的变异点作为最终结果.将该方法应用于澜沧江下游戛旧年径流极大值(1日、3日、5日、7日、1月)序列进行分析,结果显示各个序列均在2004年发生了明显跳跃变异,且与该流域水文过程变化、水利工程建设等物理成因十分吻合,验证了该方法的合理性和可靠性. 相似文献
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水文过程及其尺度响应 总被引:2,自引:0,他引:2
水文循环机制涉及到各个尺度界面的水文过程关系.水文变量(降雨、径流等)随时间和空间变化很大,是与尺度响应的非线性过程.尺度转换是建立合适的参数去描述这些过程, 涉及到如何穿越不同尺度约束体系(水文过程)的限制.基于对水文响应及其尺度转换认识所建立起来的现行水文模型的主流是还原分析方法,采用小尺度演绎方法,过度参数化成为习以常规,导致无资料流域预测结果的很大不确定性.因此,尺度转换是水文过程研究所面临的主要难点和热点问题.水文模型只有建立在对尺度相关的水文过程深刻理解基础上,对于预测水文响应才是有效的.预测径流在时间和空间的结果是根据径流系统穿越尺度过程的动态分析得出的,把尺度分析转变于水文变量的谱分析,即通过水文变量的谱相分析,认识发生在不同尺度范围内潜在的秩序和规律,研究他们形成的机制,寻求决定水文过程规则的通用表达方式,开发尺度转换的方法. 相似文献
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流域径流泥沙对多尺度植被变化响应研究进展 总被引:16,自引:0,他引:16
植被变化与流域水文过程构成一个反馈调节系统,是目前生态水文学研究的重点对象.由于植被自身的生长发育以及受自然因素和人为干扰的作用,植被变化具有多尺度性;由于受流域水文环境的异质性和水文通量的变化性的影响,流域水文过程也同样具有多尺度性.因此,只有通过对不同尺度生态水文过程分析,才能揭示流域径流泥沙对植被变化的响应机理.从不同时空尺度回顾了植被生长、植被演替、植被分布格局变化、造林以及森林经营措施等对流域径流泥沙影响的主要研究成果;概括了目前研究采用的3种主要方法,即植被变化对坡面水流动力学影响的实验室模拟、坡面尺度和流域尺度野外对比观测实验以及水文生态模型模拟方法;分析了植被变化与径流泥沙响应研究要考虑的尺度问题,从小区尺度上推至流域尺度或区域尺度时应考虑不同的生物物理控制过程.研究认为,要确切理解植被与径流泥沙在不同时空尺度的相互作用,必须以等级生态系统的观点为基础,有效结合生态水文与景观生态的理论,从地质-生态-水文构成的反馈调节入手,系统地理解植被变化与径流泥沙等水分养分之间的联系及反馈机制,建立尺度转换的基础.同时,作为有效的研究工具,今后水文模型的发展应更加注重耦合植被生理生态过程以及景观生态过程,从流域径流泥沙对多尺度植被变化水文响应的过程与机制入手,为植被恢复与重建、改善流域水资源状况和流域生态环境奠定基础. 相似文献
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The impact of temporally correlated fluctuating environments (coloured noise) on the extinction risk of populations has become a main focus in theoretical population ecology. In this study we particularly focus on the extinction risk in strongly correlated environments. Here, we found that, in contrast to moderate auto-correlation, the extinction risk was highly dependent on the process of noise generation, in particular on the method of variance scaling. Such scaling is commonly applied to avoid variance-driven biases when comparing the extinction risk under white and coloured noise. We show that for strong auto-correlation often-used scaling techniques lead to a high variability in the variances of the resulting time series and thus to deviations in the subsequent extinction risk. Therefore, we present an alternative scaling method that always delivers the target variance, even in the case of strong auto-correlation. In contrast to earlier techniques, our very intuitive method is not bound to auto-regressive processes but can be applied to all types of coloured noises. We strongly recommend our method to generate time series when the target of interest is the effect of noise colour on extinction risk not obscured by any variance effects. 相似文献
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水文模型是水文过程研究的有效工具,初损率(λ)是径流模型SCS-CN模型的参数,对模拟流域水文过程具有重要意义。为了确定生物结皮对λ的影响,提高该模型在黄土高原生物结皮广泛分布的退耕地的预测精度,本研究以陕西省定边县鹰窝山涧流域不同盖度的生物结皮坡面为对象,采用模拟降雨试验,分析土壤潜在最大入渗量(S)与实际入渗量(F)的关系,以及生物结皮盖度对λ的影响,并修订了λ;在此基础上,采用陕西省安塞县纸坊沟流域生物结皮径流小区的模拟降雨试验数据校验了参数修订后的模型。结果表明: 生物结皮坡面S与F的关系式为: S/F=2.5×60/T(其中T为降雨历时);模型参数λ与生物结皮盖度(CBSC)呈极显著负相关关系,二者关系式为: λ=0.0791×e(-0.015×CBSC),R2=0.60;较λ取标准值,依生物结皮盖度修订λ后,SCS-CN模型Nash效率系数提高338.7%,合格率提升16.1%。研究结果为黄土高原生物结皮坡面λ的确定提供了科学依据,对准确评估黄土高原退耕还林(草)工程的水文效应具有重要意义。 相似文献
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The dams in the upper reaches of the Yangtze River are highly concentrated. Dam construction can effectively solve water shortage problems; however, the natural hydrological regimes of rivers have changed to varying degrees under the influence of water conservancy projects. In this study, a comprehensive method is proposed to analyze the hydrological regime changes in a river impacted by a dam through the evaluation of hydrological periodicity, hydrological frequency and hydrological parameters. Hydrological periodicity is used to evaluate the time series from the vertical multiyear perspective, while hydrological frequency is used to evaluate the time series from the horizontal one-year perspective. The two parameters have complementary roles. The indicators of hydrologic alteration and environmental flow component parameters are used to analyze the changes in various hydrological factors affected by the dam. The results demonstrate that the construction of dams can change the multiyear periodicity of the flow and reduce the peak flow. As a result, downstream fish may be unable to sense the reduced floods and fail to spawn. The indicators of hydrologic alteration and environmental flow component parameters can complement each other and can be used to evaluate changes in a hydrological regime influenced by a dam. This comprehensive method can be used to analyze how the hydrological regime is affected by this dam. 相似文献
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Anatoly P. Shevyrnogov Alexei V. Kartushinsky Galina S. Vysotskaya 《Aquatic Ecology》2002,36(2):153-164
This work describes avenues to use satellite information to analyse dynamic processes in aquatic ecosystems. Information for this analysis, was retrieved from AVHRR satellite sensor data. This information consisteds of time series of images of radiation temperature and turbidity. We expect this information will be of great value in analysing inland water bodies. Methods to process satellite information using original software and data processing techniques are proposed. For the investigation of the process and analyses of satellite information Shira Lake (Khakasia, Siberia) was used as a case study. To study the variability of the surface temperature and turbidity of the Lake in summer, the satellite and ground-truth data of the lake was applied. This study represents the first evaluation of the dynamic processes for Lake Shira based on satellite, ground-truth and modelling data. We developed algorithms and software to process satellite images to enable the reconstruction of time dependence of temperature and spectral reflectance of water bodies in the visible range, and to make computer-animated films visualising the spatial and temporal dynamics of the study parameters. The analyses of morphometric, meteorological and hydrological characteristics of Lake Shira have provided a realistic opportunity for processing the satellite information and to develop numerical models of variability of the hydrological regime of the lake. The results obtained demonstrate the feasibility of systematically retrieving the spatial information from the satellite data on the dynamics of the surface water temperature and of the suspended matter in the lake. 相似文献
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The gating of ion channels has widely been modeled by assuming the transition between open and closed states is a memoryless process. Nevertheless, the statistical analysis of an ionic current signal recorded from voltage dependence K(+) single channel is presented. Calculating the sample auto-correlation function of the ionic current based on the digitized signals, rather than the sequence of open and closed states duration time. The results provide evidence for the existence of memory. For different voltages, the ion channel current fluctuation has different correlation attributions. The correlations in data generated by simulation of two Markov models, on one hand, auto-correlation function of the ionic current shows a weaker memory, after a delayed period of time, the attribute of memory does not exist; on the other hand, the correlation depends on the number of states in the Markov model. For V(p)=-60 mV pipette potential, spectral analysis of ion channel current was conducted, the result indicates that the spectrum is not a flat spectrum, the data set from ionic current fluctuations shows considerable variability with a broad 1/f -like spectrum, alpha=1.261+/-0.24. Thus the ion current fluctuations give information about the kinetics of the channel protein, the results suggest the correlation character of ion channel protein nonlinear kinetics regardless of whether the channel is in open or closed state. 相似文献