自动与人工观测数据的差异   总被引：41，自引：5，他引：41       下载免费PDF全文

胡玉峰 《应用气象学报》2004,15(6):719-726

该文概述了造成自动观测与人工观测数据差异的各种原因，其中包括仪器的测量原理与观测方法不同，观测时间和空间不同，采样方式与算法不同，观测时次不同等等。通过对比分析基本气象要素，如气压、气温、地温、风向风速、降水、湿度等的两种观测数据，认为自动气象站的观测结果更接近大气中的实际情况。自动站对气压、气温和风向风速的观测有明显的优势，但在雨量累计量的测量和高温高湿下的湿度测量效果不理想。  相似文献   

Including prior information in the estimation of effective soil parameters in unsaturated zone modelling   总被引：2，自引：0，他引：2  

J Mertens  H Madsen  D Jacques 《Journal of Hydrology》2004,294(4):251-269

In this paper we propose a methodology to include prior information in the estimation of effective soil parameters for modelling the soil moisture content in the unsaturated zone. Laboratory measurements on undisturbed soil cores were used to estimate the moisture retention curve and hydraulic conductivity curve parameters. The soil moisture content was measured at 25 locations along three transects and at three different depths (surface, 30 and 60 cm) on an 80×20 m hillslope for the year 2001. Soil cores were collected in 84 locations situated in three profile pits along the hillslope. For the estimation of the effective soil hydraulic parameters the joint probability distribution of measured parameter values was used as prior information. A two-horizon single column 1D MIKE SHE model based on Richards' equation was set-up for nine soil moisture measurement locations along the middle transect of the hillslope. The goal of the model is to simulate the soil moisture profile at each location. The shuffled complex evolution (SCE) algorithm has been applied to estimate effective model parameters using either wide parameter ranges, referred to as the ‘no-prior’ case, or the joint probability distribution of measured parameter values as prior information (‘prior’ case). When the prior information is incorporated in the SCE optimisation the goodness-of-fit of the model predictions is only slightly worse compared to when no-prior information is incorporated. However, the effective parameter estimates are more realistic when the prior information is incorporated. For both the no-prior and prior case the generalised likelihood uncertainty estimation procedure (GLUE) was subsequently used to estimate the uncertainty bounds (UB) on the model predictions. When incorporating the prior information more parameter sets were accepted for the estimation of the predictive uncertainty and the parameter values were more realistic. Moreover, UB better enclosed the observations. Thus, incorporating prior information in GLUE reduces the amount of model evaluations needed to obtain sufficient behavioural parameter sets. The results indicate the importance of prior information in the SCE and GLUE parameter estimation strategies.  相似文献   

基于COM+对Web地图服务性能影响的建模与分析     

陈引川  王青山  龙明  张立朝 《北京测绘》2006,(2):5-7,37

Web地图服务的后台是否使用COM+服务对其性能影响非常大。本文通过分析两种方式的原理模型并通过测试实验来比较这两种方式对Web服务系统性能的影响,得出使用COM+服务后,Web地图服务的稳定性与响应速度有明显提高。  相似文献   

Calibration framework for a Kalman filter applied to a groundwater model     

Jean-Philippe Drécourt  Henrik Madsen  Dan Rosbjerg 《Advances in water resources》2006

The paper presents a novel approach to the setup of a Kalman filter by using an automatic calibration framework for estimation of the covariance matrices. The calibration consists of two sequential steps: (1) Automatic calibration of a set of covariance parameters to optimize the performance of the system and (2) adjustment of the model and observation variance to provide an uncertainty analysis relying on the data instead of ad-hoc covariance values. The method is applied to a twin-test experiment with a groundwater model and a colored noise Kalman filter. The filter is implemented in an ensemble framework. It is demonstrated that lattice sampling is preferable to the usual Monte Carlo simulation because its ability to preserve the theoretical mean reduces the size of the ensemble needed. The resulting Kalman filter proves to be efficient in correcting dynamic error and bias over the whole domain studied. The uncertainty analysis provides a reliable estimate of the error in the neighborhood of assimilation points but the simplicity of the covariance models leads to underestimation of the errors far from assimilation points.  相似文献   

Stochastic modelling and risk analysis of groundwater pollution using FORM coupled with automatic differentiation     

Husam Baalousha  Jürgen Kngeter 《Advances in water resources》2006,29(12):1815-1832

The first order reliability method (FORM) has been widely used in probabilistic modelling of groundwater problems. The FORM approach requires an iterative optimization procedure to find out the system failure point (the most probable point).The advantages of this approach are that it does not require many computations in comparison with other methods when applied to simple problems, and it produces reasonably accurate results. However, it has been found that the computations of FORM can equal or exceed that of other methods in case of large number of variables.In this paper, a new implementation of FORM was proposed with more efficiency and accuracy than the traditional FORM method. In the proposed approach, automatic differentiation is used to obtain the gradient vector of the limit state function, which is required by FORM, instead of using finite difference estimation. This way, the first order derivative was obtained with a very good accuracy, and with less computational effort. Based on the obtained results, it is found that the proposed implementation of FORM is a very good tool for probabilistic risk assessment and uncertainty analysis in groundwater problems.  相似文献   

相空间地震波初至时刻拾取          下载免费PDF全文

姜少之  张志禹 《地震工程学报》2006,28(1):11-14

提出了一种新的地震波初至时刻拾取的方法,即将原始时间序列信号映射到相空间当中,通过其相空间图的特征进行初至时刻的拾取。相对于非常耗时的传统方法,本方法使得运算速度提高,结果更加精确稳定。  相似文献   

单相双电源自动切换装置的研制     

高跃雄  高振强  张仰辉 《山西地震》2006,(2):47-48

叙述了单相双电源自动切换装置的设计要求及思路,实际使用证明该装置完全达到了设计要求,指出,该装置的使用可实现供电系统自动化,可用于“十五”项目的建设。  相似文献   

基于振幅和瞬时频率的震相自动识别方法     

李山有  朱海燕  武东坡  宋晋东 《世界地震工程》2006,22(4):1-4

为了充分反映地震信号振幅增大和频率改变的特征,发展了一种以振幅和瞬时频率比乘积为特征参量的震相自动识别方法。谐波信号和有限实际地震记录的应用表明,本方法具有较高的识别精度。  相似文献   

网上测绘相关文献的查找方法     

XIAO Xuebin Library of Wuhan University  Wuhan  China 《测绘科技情报》2006,(2)

掌握一个好的文献资料的查找方法对于我们的工作、学习、日常生活以及科学研究都有很大的帮助。本文阐述了利用Internet网查找测绘相关文献的方法,并介绍了一些测绘相关网站和网络数据库,还介绍了从Internet网上获取测绘文献的三种方式,以及在查找信息的过程中所使用的一般方法和选择检索词的技巧。  相似文献   

面要素汉字注记自动配置的一种算法   总被引：4，自引：0，他引：4  

李艳 《测绘学院学报》1998,(1)

地图注记的计算机配置是地图自动化生产、电子地图制作与显示以及地理信息系统中不可缺少的组成模块。文中着重讨论了面状要素汉字注记的原则、特点 ,对现有一些算法进行了改进 ,提出了一种面状要素汉字注记自动配置的新算法  相似文献