Discrete wavelet‐based trend identification in hydrologic time series     

Yan‐Fang Sang  Zhonggen Wang  Changming Liu 《水文研究》2013,27(14):2021-2031

Trend identification is a substantial issue in hydrologic series analysis, but it is also a difficult task in practice due to the confusing concept of trend and disadvantages of methods. In this article, an improved definition of trend was given as follows: ‘a trend is the deterministic component in the analysed data and corresponds to the biggest temporal scale on the condition of giving the concerned temporal scale’. It emphasizes the intrinsic and deterministic properties of trend, can clearly distinguish trend from periodicities and points out the prerequisite of the concerned temporal scale only by giving which the trend has its specific meaning. Correspondingly, the discrete wavelet‐based method for trend identification was improved. Differing from those methods used presently, the improved method is to identify trend by comparing the energy difference between hydrologic data and noise, and it can simultaneously separate periodicities and noise. Furthermore, the improved method can quantitatively estimate the statistical significance of the identified trend by using proper confidence interval. Analyses of both synthetic and observed series indicated the identical power of the improved method as the Mann–Kendall test in assessing the statistical significance of the trend in hydrologic data, and by using the former, the identified trend can adaptively reflect the nonlinear and nonstationary variability of hydrologic data. Besides, the results also showed the influences of three key factors (wavelet choice, decomposition level choice and noise content) on discrete wavelet‐based trend identification; hence, they should be carefully considered in practice. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

The influence of dam and lakes on the Yangtze River streamflow: long‐range correlation and complexity analyses     

Qiang Zhang  Yu Zhou  Vijay P. Singh  Xiaohong Chen 《水文研究》2012,26(3):436-444

Employing long‐range correlation, complexity features and clustering, this study investigated the influence of dam and lake‐river systems on the Yangtze River flow. The impact of the Gezhouba Dam and the lake systems on streamflow was evaluated by analysing daily streamflow records at the Cuntan, the Yichang and the Datong station. Results indicated no evident influence of the Gezhouba Dam on streamflow changes. Distinct differences in scaling behaviour, long‐range correlation and clustering of streamflow at the Datong station when compared with those at the Cuntan and Yichang stations undoubtedly showed the influence of water storage and the buffering effect of the lake systems between the Datong station and other two hydrological stations on streamflow in the lower Yangtze River basin. Decreased regularity, enhanced long‐range correlation and increased clustering of streamflow in the lower Yangtze River basin due to the effect of water storage of the lake systems were corroborated. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

环境水利学在中国的兴起与发展          下载免费PDF全文

方子云 《水科学进展》1990,1(1):55-59

本文阐述了环境水利学的定义与内容,提出了环境水利学的五大任务,并根据每一个任务分别说明了在中国的发展情况。最后。提出了如何发展这一学科的一些设想.  相似文献   

从人口资源与生态环境的观点分析我国国情与农村经济发展   总被引：7，自引：0，他引：7  

周立三 《地理学报》1990,45(3):257-263

本文从人口与资源、生态环境等方面,简要地探讨了我国国情与农村经济发展的趋向,论述了人口与资源、环境的制约因素。认为只有通过严格控制人口,强化人力开发利用;节约资源,增加投入,挖掘潜力;增强环境保护意识,推行综合防治措施等有效途径,辩证地处理好生存与发展的关系,才能保证我国农村经济获得持续稳定协调发展。  相似文献   

熔体结构与酸性熔岩的某些特征          下载免费PDF全文

周金诚 《岩石矿物学杂志》1988,7(3):215-221

在流纹质岩浆中,存在两种不混溶的熔体,一种熔体富SiO_2贫FeO,另一种则相反。从熔体结构的角度看,前一种熔体富桥氧,后者则富自由氧。水的解聚作用可以改变流纹质岩浆的结构,即降低它的聚合程度,因此,含水流纹岩浆的粘度低于玄武岩浆的粘度,从而使流纹岩中流纹构造发育。 实际工作中应避免混淆流纹岩与酸性熔结凝灰岩。  相似文献   

The Characteristics of Migration of Ore Solutions in No.6 East Tin Deposit of the Songshujiao Orefield, Gejiu     

Jiang Zhuwei  Zhou Dapeng 《《地质学报》英文版》1989,63(4):405-416

No. 6 East tin deposit in the Songshujiao orefield, Gejiu, is characterized by one-stage hydrothermal activity and monotonous country rocks. The authors selected this deposit and used the multivariate statistical analysis to study the types of association of main ore-forming elements at different temperatures and pressures and their distribution in the deposit. On that basis combined with the structural analysis of the deposit, the recto-geochemical features of No.6 East tin deposit have been revealed and the direction and channel of migration of the ore solutions in faults and the deposit have been deduced. This research can appropriately elucidate the control of faults on the migration of ore solutions and the sites where ore solutions are dispersed and accumulated, thus providing the theoretical basis for the prediction of hydrothermal deposits in question.  相似文献   

大震前小震活动条带的定量分析方法的初步研究          下载免费PDF全文

周仕勇  王海涛 《地震工程学报》1989,11(S1):69-72

近年来,大震发生前出现小震活动条带的现象已引起国内外地震工作者的普遍关注。  相似文献   

磁法勘探在新疆尉犁县且干布拉克蛭石、磷灰石矿床普查评价中的应用效果     

周厚嘉  张万祥 《新疆地质》1989,(2)

尉犁县且干布拉克蛭石矿为特大型,磷灰石矿为大型.蛭石、磷灰石均赋存于磁性较强的透辉石岩及超基性岩中,矿体与围岩间有较明显的磁性差异,含矿母岩70%被第四系覆盖.利用地面磁测,较好地圈定了含矿母岩的边界,提供了含矿体的平面形态及产状,为勘查缩小了靶区.磁法勘探不仅是直接找磁铁矿床及某些有关金属矿床的有效方法,而且在间接寻找非金属矿床上亦能发挥作用.  相似文献   

钻孔孔径的变化对γ测井解释含量的影响     

周明海 《铀矿地质》1989,5(2):102-107

钻孔孔径变化与矿床类型、钻进孔径、矿化岩性、矿层品位、矿层厚度、冲冼液的性质以及工程切穿矿层的时间有着密切的关系。孔径变化对γ测井解释含量、矿床储量的增减影响甚大。理论和实践证明,专门性的孔径测量,是提高γ测井质量、准确确定矿层品级的重要措施之一,对提高矿床经济效益也具有重要意义。  相似文献   

北京市区冬季大气气溶胶空气动力学尺度谱分布的研究   总被引：1，自引：2，他引：1  

赵德山  汤大钢  周舟 《大气科学》1988,12(2):140-146

本文讨论了北京市区冬季大气气溶胶空气动力学尺度的各种谱分布,发现平均粒子谱为单峰型,而平均表面积谱和平均质量谱则通常为三峰型。但是,表面积谱和质量谱随时间变化明显。 三峰型质量谱与国外给出的城市双峰型质量谱差别显著,揭示了我国目前城市气溶胶污染所具有的一种带普遍性的重要特性。  相似文献