基于交叉〖CDF*2〗平行法的双偏振雷达差分反射率硬件定标     

赵世颖  李柏  陈晓辉  王振会 《气象科技》2015,43(5):775-782

双偏振天气雷达具有改善测雨精度及识别降水粒子相态的能力,但其系统自身有可能会对差分反射率因子（ZDR）的测量精度产生明显的偏差,从而降低气象产品的可靠度。美国利用升级为双偏振的WSR 88D进行了大量试验,认为需要校正传输信号在发射和接收通道路径上引起的差异。本文根据其试验报告,以我国研制的车载C波段双偏振多普勒雷达作为试验平台,对比分析后得出产生ZDR系统误差的主要来源为：发射通路、接收通路与天线支路。因此,使用交叉与平行法消除测试信号及设备产生的差异影响,对3部分路径重要节点进行测量并计算出水平、垂直两通道的相对偏差值,进而订正ZDR。其中,天线支路偏差值长期稳定,可相应减少测量次数;发射、接收通路的偏差值会随设备运行产生随机变化,需定期进行测量。以体扫模式最高仰角下的干雪为自然目标物的方法来验证定标的效果,结果表明此方法可较好地订正ZDR的系统误差,为今后偏振雷达业务应用提供了一套消除ZDR系统误差的有效方法。  相似文献   

Diagnostic evaluation of conceptual rainfall–runoff models using temporal clustering     

N. J. de Vos  T. H. M. Rientjes  H. V. Gupta 《水文研究》2010,24(20):2840-2850

Given the structural shortcomings of conceptual rainfall–runoff models and the common use of time‐invariant model parameters, these parameters can be expected to represent broader aspects of the rainfall–runoff relationship than merely the static catchment characteristics that they are commonly supposed to quantify. In this article, we relax the common assumption of time‐invariance of parameters, and instead seek signature information about the dynamics of model behaviour and performance. We do this by using a temporal clustering approach to identify periods of hydrological similarity, allowing the model parameters to vary over the clusters found in this manner, and calibrating these parameters simultaneously. The diagnostic information inferred from these calibration results, based on the patterns in the parameter sets of the various clusters, is used to enhance the model structure. This approach shows how diagnostic model evaluation can be used to combine information from the data and the functioning of the hydrological model in a useful manner. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Revised empirical garnet–biotite–muscovite–plagioclase geobarometer in metapelites          下载免费PDF全文

C. M. Wu 《Journal of Metamorphic Geology》2015,33(2):167-176

The garnet–biotite–muscovite–plagioclase (GBMP) barometer was empirically revised for P–T conditions of 1–14 kbar and 450–840 °C, using 263 metapelitic rock samples from all over the world. This barometer is based on activity models for garnet, biotite and plagioclase identical to those of the well‐calibrated garnet–biotite thermometer and the garnet–aluminosilicate–plagioclase–quartz (GASP) barometer. The GBMP barometer is less temperature dependent than the GASP barometer and can be applied to either Al₂SiO₅‐absent or Al₂SiO₅‐bearing metapelites. The total error of the GBMP barometer is estimated to be about ±1.2 kbar on considering input temperature error and analytical errors of chemical compositions of the phases involved. The random error of the GBMP barometer is evenly distributed with respect to pressure, temperature and mineral composition. Simultaneous application of the GBMP barometer and the garnet–biotite thermometer identifies the correct stability field for Al₂SiO₅‐bearing metapelites. Application of the GBMP barometer to metapelitic rocks within the same geological terranes or thermal contact aureoles yielded similar pressures within error. A spreadsheet for implementing the proposed GBMP geobarometer is supplied on the journal's website.  相似文献   

The value of remotely sensed surface soil moisture for model calibration using SWAT          下载免费PDF全文

Dipangkar Kundu  R. Willem Vervoort  Floris F. van Ogtrop 《水文研究》2017,31(15):2764-2780

Remotely sensed (RS) data can add value to a hydrological model calibration. Among this, RS soil moisture (SM) data have mostly been assimilated into conceptual hydrological models using various transformed variable or indices. In this study, raw RS surface SM is used as a calibration variable in the Soil and Water Assessment Tool model. This means the SM values were not transformed into another variable (e.g., soil water index and root zone SM index). Using a nested catchment, calibration based only on RS SM and optimizing model parameters sensitive to SM using particle swarm optimization improved variations in streamflow predictions at some of the gauging stations compared to the uncalibrated model. This highlighted part of the catchments where the SM signal directly influenced the flow distribution. Additionally, highlighted high and low flow signals were mostly influenced. The seasonal breakdown indicates that the SM signal is more useful for calibrating in wetter seasons and in areas with higher variations in elevation. The results identified that calibration only on RS SM improved the general rainfall–runoff response simulation by introducing delays but cannot correct the overall routing effect. Furthermore, catchment characteristics (e.g., land use, elevation, soil types, and precipitation) regulating SM variation in different seasons highlighted by the model calibration are identified. This provides further opportunities to improve model parameterization.  相似文献   

Snow process monitoring in montane forests with time‐lapse photography          下载免费PDF全文

Chunyu Dong  Lucas Menzel 《水文研究》2017,31(16):2872-2886

A camera network with hourly resolution was used to monitor the complex snow processes in montane forest environments. We developed a semi‐automatic procedure to interpret snow depths from the digital images, which exhibited high consistency with manual measurements and station‐based recordings. To extract snow interception dynamics, six binary classification methods were compared. The MaxEntropy classifier demonstrated better performance than the other methods under conditions of varying illumination and was therefore selected as the method used for quantifying snow in tree canopies. Snow accumulation and ablation on the ground, as well as snow loading and unloading in the forest canopies, were investigated using snow parameters derived from the time‐lapse photography monitoring. The influences of meteorologic conditions, forest cover, and elevation on the snow processes were also considered. Time‐lapse photography proved to be an effective and low‐cost approach for collecting useful information on snow processes and facilitating the set‐up of hydrological models.  相似文献   

Parameter uncertainty of the AWBM model when applied to an ungauged catchment          下载免费PDF全文

Md Mahmudul Haque  Ataur Rahman  Dharma Hagare  Golam Kibria 《水文研究》2015,29(6):1493-1504

In this study, a quantitative assessment of uncertainty was made in connection with the calibration of Australian Water Balance Model (AWBM) for both gauged and ungauged catchment cases. For the gauged catchment, five different rainfall data sets, 23 different calibration data lengths and eight different optimization techniques were adopted. For the ungauged catchment case, the optimum parameter sets obtained from the nearest gauged catchment were transposed to the ungauged catchments, and two regional prediction equations were used to estimate runoff. Uncertainties were ascertained by comparing the observed and modelled runoffs by the AWBM on the basis of different combinations of methods, model parameters and input data. The main finding from this study was that the uncertainties in the AWBM modelling outputs could vary from ?1.3% to 70% owing to different input rainfall data, ?5.7% to 11% owing to different calibration data lengths and ?6% to 0.2% owing to different optimization techniques adopted in the calibration of the AWBM. The performance of the AWBM model was found to be dominated mainly by the selection of appropriate rainfall data followed by the selection of an appropriate calibration data length and optimization algorithm. Use of relatively short data length (e.g. 3 to 6 years) in the calibration was found to generate relatively poor results. Effects of different optimization techniques on the calibration were found to be minimal. The uncertainties reported here in relation to the calibration and runoff estimation by the AWBM model are relevant to the selected study catchments, which are likely to differ for other catchments. The methodology presented in this paper can be applied to other catchments in Australia and other countries using AWBM and similar rainfall–runoff models. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Using MODFLOW code to approach transient hydraulic head with a sharp‐interface solution          下载免费PDF全文

Carlos Llopis‐Albert  David Pulido‐Velazquez 《水文研究》2015,29(8):2052-2064

Saltwater intrusion problems have been usually tackled through analytical models because of its simplicity, easy implementation and low computational cost. Most of these models are based on the sharp‐interface approximation and the Ghyben–Herzberg relation, which neglects mixing of fresh water and seawater and implicitly assumes that salt water remains static. This paper provides insight into the validity of a sharp‐interface approximation defined from a steady state solution when applied to transient seawater intrusion problems. The validation tests have been performed on a 3D unconfined synthetic aquifer, which include spatial and temporal distribution of recharge and pumping wells. Using a change of variable, the governing equation of the steady state sharp‐interface problem can be written with the same structure of the steady confined groundwater flow equation as a function of a single potential variable (?). We propose to approach also the transient problem solving a single potential equation (using also the ? variable) with the same structure of the confined groundwater flow equation. It will allow solving the problem by using the classical MODFLOW code. We have used the parameter estimation model PEST to calibrate the parameters of the transient sharp‐interface equation. We show how after the calibration process, the sharp‐interface approach may provide accurate enough results when applied to transient problems and improve the steady state results, thus avoiding the need of implementing a density‐dependent model and reducing the computational cost. This has been proved by comparing results with those obtained using the finite difference numerical code SEAWAT for solving the coupled partial differential equations of flow and density‐dependent transport. The comparison was performed in terms of piezometric heads, seawater penetration, transition zone width and critical pumping rates. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

On the use of multi‐algorithm,genetically adaptive multi‐objective method for multi‐site calibration of the SWAT model     

Xuesong Zhang  Raghavan Srinivasan  Michael Van Liew 《水文研究》2010,24(8):955-969

With the availability of spatially distributed data, distributed hydrologic models are increasingly used for simulation of spatially varied hydrologic processes to understand and manage natural and human activities that affect watershed systems. Multi‐objective optimization methods have been applied to calibrate distributed hydrologic models using observed data from multiple sites. As the time consumed by running these complex models is increasing substantially, selecting efficient and effective multi‐objective optimization algorithms is becoming a nontrivial issue. In this study, we evaluated a multi‐algorithm, genetically adaptive multi‐objective method (AMALGAM) for multi‐site calibration of a distributed hydrologic model—Soil and Water Assessment Tool (SWAT), and compared its performance with two widely used evolutionary multi‐objective optimization (EMO) algorithms (i.e. Strength Pareto Evolutionary Algorithm 2 (SPEA2) and Non‐dominated Sorted Genetic Algorithm II (NSGA‐II)). In order to provide insights into each method's overall performance, these three methods were tested in four watersheds with various characteristics. The test results indicate that the AMALGAM can consistently provide competitive or superior results compared with the other two methods. The multi‐method search framework of AMALGAM, which can flexibly and adaptively utilize multiple optimization algorithms, makes it a promising tool for multi‐site calibration of the distributed SWAT. For practical use of AMALGAM, it is suggested to implement this method in multiple trials with relatively small number of model runs rather than run it once with long iterations. In addition, incorporating different multi‐objective optimization algorithms and multi‐mode search operators into AMALGAM deserves further research. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

利用激光三角法进行快速车辙检测   总被引：2，自引：0，他引：2  

李清泉  雷波  毛庆洲  傅智能 《武汉大学学报(信息科学版)》2010,(3)

为了实现实时车辙测量及绘制足够密集的路面剖面线,分别设定全局和局部阈值,利用局部梯度极大值及邻域灰度进行激光线判断和提取;提出了基于Delaunay三角网的标定点网格建立及测量点的物方坐标反算方法。实验路段的检测结果表明,车辙检测仪的检测结果与人工检测结果符合得较好,可以作为路面车辙测量的可靠工具。  相似文献   

开放型摄影测量实验基地的设计与建立   总被引：1，自引：1，他引：0  

龚涛  冉将军  冯威  孔健 《测绘科学》2010,35(3)

摄影测量技术的学习和掌握离不开实验。文中提出建立开放型摄影测量实验基地模式,该基地应该具有如下功能:航空摄影,航测控制测量与调绘,数码相机检校,航测内业处理与测图。在该基地上,学生可以根据摄影测量的学习内容,选择相关实验项目,理论联系实际地学习掌握摄影测量基本理论和方法;学生也可以在基地上自主设计、模拟摄影测量生产过程,训练摄影测量技能,并进行摄影测量试验研究。该实验基地的设计理念和建立模式,将为高校现有摄影测量课程的教学和实验提供一种创新形式。  相似文献