Construction of design hyetographs for locations without observed data     

Gwo‐Fong Lin  Ming‐Chang Wu  Guo‐Rong Chen  Shen‐Jung Liu 《水文研究》2010,24(4):481-491

A design hyetograph which represents the time distribution of design rainfall depth corresponding to a duration and a return period is essential in hydrologic design. However, for locations without observed data (ungauged sites), construction of design hyetographs is a difficult task because of the lack of data. Hence, an approach based on self‐organizing map (SOM) is proposed in this paper to construct design hyetographs at ungauged sites. SOM, which is a special kind of artificial neural networks (ANNs), is a powerful technique for extracting and visualizing salient features of data and for solving classification problems. The proposed approach is composed of three steps: classification, assignment and construction. First, the SOM‐based classification is performed to analyse gauged sites' design hyetographs. Second, based on the concept of indicator kriging, a method is developed to assign an ungauged site of interest to a certain cluster. Third, based on the spatial information, the clustering results, and the design hyetographs of gauged sites, the design hyetograph at the site of interest is constructed using the reciprocal‐distance‐squared method. An application is conducted to assess the advantages of the proposed approach over the conventional approaches. Moreover, cross‐validation tests are applied to evaluate the performance of the accuracy and the robustness of the proposed approach. The results confirm the improvement in performance by using the proposed approach instead of conventional approaches. The proposed approach is useful for constructing design hyetographs at ungauged sites. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Improving the forecasts of extreme streamflow by support vector regression with the data extracted by self‐organizing map          下载免费PDF全文

Ming‐Chang Wu  Gwo‐Fong Lin  Hsuan‐Yu Lin 《水文研究》2014,28(2):386-397

During typhoons or storms, accurate forecasts of hourly streamflow are necessary for flood warning and mitigation. However, hourly streamflow is difficult to forecast because of the complex physical process and the high variability in time. Furthermore, under the global warming scenario, events with extreme streamflow may occur that leads to more difficulties in forecasting streamflows. Hence, to obtain more accurate hourly streamflow forecasts, an improved streamflow forecasting model is proposed in this paper. The computational kernel of the proposed model is developed on the basis of support vector machine (SVM). Additionally, self‐organizing map (SOM) is used to analyse observed data to extract data with specific properties, which are capable of providing valuable information for streamflow forecasting. After reprocessing, these extracted data and the observed data are used to construct the SVM‐based model. An application is conducted to clearly demonstrate the advantage of the proposed model. The comparison between the proposed model and the conventional SVM model, which is constructed without SOM, is performed. The results indicate that the proposed model is better performed than the conventional SVM model. Moreover, as regards the extreme events, the result shows that the proposed model reduces the forecasting error, especially the error of peak streamflow. It is confirmed that because of the use of data extracted by SOM, the improved forecasting performance is obtained. The proposed model, which can produce accurate forecasts, is expected to be useful to support flood warning systems. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

复合坐标系在非开挖竣工验收中的应用          下载免费PDF全文

魏宏超  刘健  黄寒静  林阳 《探矿工程》2012,39(Z1):139-141

随着非开挖水平定向钻进（HDD）技术的发展和推广应用,清晰而准确的反映施工轨迹与设计轨迹的偏差成为评判工程质量的一个重要指标。本文应用极等间距网与笛卡尔坐标系结合构成的复合坐标系,将非开挖施工轨迹与设计轨迹的偏差绘制在坐标系中,直观的反映了施工后实际轨迹与设计轨迹的偏差程度,对轨迹的验收具有非常直观可靠的意义。  相似文献   

热带气旋的螺旋度特性   总被引：18，自引：1，他引：18  

陈华  谈哲敏 《热带气象学报》1999,15(1):81-85

将螺旋度的概念引入热带气旋，对热带气旋螺旋度的结构特征及其在热带气旋发展过程中的演变过程进行了研究。结果表明，热带气旋这种具有较强螺旋性的天气系统，其发展过程也就是螺旋度增强的过程。螺旋度对热带气旋稳定过程的维持及其长久的生命期具有重要的作用。  相似文献   

A computerised decision support system for rural policy formulation     

Philip M. Watson  Richard A. Wadsworth 《International journal of geographical information science》2013,27(4):425-440

Abstract

A primary goal of the NERC/ESRC Land Use Programme (NELUP) was to design and build a decision support system (DSS) to model rural land use and its change due to environmental and agricultural policy. The effects of policies are measured in terms of economic, ecological and hydrological parameters, with land use and land cover being the uniting factors. The DSS incorporates access to a large database and a suite of complex models. The DSS is user-friendly, produces meaningful graphics, and is almost entirely mouse-driven. This paper describes the NELUP view of policy making and DSS, the NELUP database and the DSS models and interface philosophy and design. The results of workshops, conducted with potential users of the DSS, are discussed and summarised.  相似文献   

Extensions of GAP‐tree and its implementation based on a non‐topological data model     

Changxiu Cheng  Fangqu Niu  Jun Cai  Yanlu Zhu 《International journal of geographical information science》2013,27(6):657-673

This paper discusses extensions of GAP‐trees from three aspects and its implementation based on non‐topological structure in order to enhance access to large vector data sets. First of all, we apply cartographic generalization rules to build a generalization procedure of the GAP‐tree, which makes coarse representations more consistent with human cognition. Second, we replace the three‐dimensional (pseudo‐) Reactive‐tree index with a 2D R‐tree index and a B‐tree index to improve the system efficiency. Finally, we compress a binary GAP‐tree into multi‐way GAP‐trees in order to reduce data redundancy. The shallower multi‐way GAP‐trees not only eliminate redundant data but also accelerate the system's response time. The extensions have been successfully implemented in PostgreSQL. A test of Beijing's land‐use data at the 1:10 000 scale demonstrates that the extended GAP‐trees are efficient, compact, and easy to implement.  相似文献   

Non‐hyperbolic common reflection surface     

Sergey Fomel  Roman Kazinnik 《Geophysical Prospecting》2013,61(1):21-27

The method of common reflection surface (CRS) extends conventional stacking of seismic traces over offset to multidimensional stacking over offset‐midpoint surfaces. We propose a new form of the stacking surface, derived from the analytical solution for reflection traveltime from a hyperbolic reflector. Both analytical comparisons and numerical tests show that the new approximation can be significantly more accurate than the conventional CRS approximation at large offsets or at large midpoint separations while using essentially the same parameters.  相似文献   

Biodegradation of Acetamiprid by Isolated Bacterial Strain Rhodococcus sp. BCH2 and Toxicological Analysis of Its Metabolites in Silkworm (Bombax mori)          下载免费PDF全文

Swapnil S. Phugare  Jyoti P. Jadhav 《洁净——土壤、空气、水》2015,43(2):296-304

  相似文献   

梅雨期3类不同形成机制的暴雨   总被引：4，自引：1，他引：3  

刘建勇  谈哲敏  张熠 《气象学报》2012,70(3):452-466

通过对1998—2007年观测资料的分析,根据影响梅雨期暴雨发生、发展机制的不同,将梅雨期暴雨分为外强迫型、自组织型和非组织化局地型3种类型。外强迫型主要包括冷槽推进型、西南涡移出型和北槽南涡型,该类型暴雨主要是由大尺度环流的动力强迫抬升和冷空气侵入形成的不稳定层结共同作用而产生;在3类外强迫型中,高低空急流相互作用和冷槽的影响形式有很大不同。在自组织型中,暴雨对流系统具有较长生命周期,并以合并增长、上下游发展和新生中尺度涡旋等形式而传播、发展,是在切变线、水汽辐合带和低空急流等弱环境强迫下形成的一类暴雨。在非组织化局地型中,主要有山区午后强对流和副热带高压边缘对流不稳定两种形式,局地对流不稳定是暴雨产生的主要原因。不同的形成机制,导致出现了不同类型的梅雨期暴雨,相应地这些不同类型的梅雨期暴雨具有不同的预报难度。  相似文献   

华南前汛期MCS的活动特征及组织发展形式   总被引：6，自引：2，他引：4  

梁巧倩  项颂翔  林良根  蒙伟光 《热带气象学报》2012,28(4):541-551

利用卫星云图Tbb资料、常规观测资料和NCEP/NCAR再分析资料,按照Jirak对中尺度对流系统(MCS)的分类方法,将华南MCS分为MCC(中尺度对流复合体)、PECS(线状或长条状MCS)、MβCCS和MβECS(即β尺度的MCC和β尺度的PECS)4种类型,对华南前汛期MCS的时空变化特征、发生发展的组织形式和天气学背景进行了分析。结果表明:PECS是华南地区MCS的主要发展形式。4—6月MCS的发生个数逐月增多。MCS的日变化呈单峰型,主要集中于下午到上半夜形成,傍晚到半夜之间发展成熟。但具体到不同的4种类型,其日变化特征有一定差异。MCS活动分布特征与地形没有明显对应关系,全区都可有PECS发生。MCS主要以东移为主,其次的移动方向4种不同类型分别略有不同。MCS的发生发展有3种主要天气形势:500 hPa槽前西南风场型、850 hPa切变线南侧的西南风场型和地面低槽配合的Ⅰ型;500 hPa西北风场型、850 hPa切变线型和地面低槽配合的Ⅱ型;500 hPa西风槽过境型、850 hPa切变线南侧的西南风场型和地面低槽配合的Ⅲ型。孤立发展和合并增长是华南MCS的主要组织发展形式。  相似文献