Impacts of Positional Error on Spatial Regression Analysis: A Case Study of Address Locations in Syracuse, New York   总被引：1，自引：0，他引：1  

Daniel A Griffith  Marco Millones  Matthew Vincent  David L Johnson  Andrew Hunt 《Transactions in GIS》2007,11(5):655-679

Positional error is the error produced by the discrepancy between reference and recorded locations. In urban landscapes, locations typically are obtained from global positioning systems or geocoding software. Although these technologies have improved the locational accuracy of georeferenced data, they are not error free. This error affects results of any spatial statistical analysis performed with a georeferenced dataset. In this paper we discuss the properties of positional error in an address matching exercise and the allocation of point locations to census geography units. We focus on the error's spatial structure, and more particularly on impacts of error propagation in spatial regression analysis. For this purpose we use two geocoding sources, we briefly describe the magnitude and the nature of their discrepancies, and we evaluate the consequences that this type of locational error has on a spatial regression analysis of pediatric blood lead data for Syracuse, NY. Our findings include: (1) the confirmation of the recurrence of spatial clustering in positional error at various geographic resolutions; and, (2) the identification of a noticeable but not shockingly large impact from positional error propagation in spatial auto‐binomial regression analysis results for the dataset analyzed.  相似文献   

1991年3月22日耀斑激波的传播特性   总被引：2，自引：3，他引：2       下载免费PDF全文

刘绍亮  刘四清 《地球物理学报》1996,39(3):289-295

采用ＭＨＤ数值方法研究了１９９１年３月２２日２２：４７ＵＴ日面大耀斑引起的行星际激波传播的几何特性，以及初始驱动时间对传播的影响。得出：１．该激波在黄道面投影是非对称的，最快处偏离耀斑法线向东；２．激波面偏离球面，但随着远离太阳这种偏离减小；３．总能相同时，驱动时间短的激波较强，速度较快；能量变化范围相同时，不同初速比不同驱动时间对激波传播速度影响更大。  相似文献   

预测地波定时信号传播时延的经验方法     

梁仲寰 《时间频率学报》1998,21(1):8-19

在参考文献（２,３）的基础上,提出了含有大山区的复杂陆地地波路径的分段和确定各段路径等效电导率σｃ的方法,给出如何利用接收点场强实测值和已有的理论色散修正曲线（δｔ－ｄ）＾（６）近似计算色散修正值的方法,并对４条含大山区的复杂路径信号传播时延实测值ｔｇ＾－（收）与预测值ｔｇ进行比较,结果表明：路径分为３段等效时的预测准确度要比整段等效高得多。  相似文献   

Analysis of temporal and spatial characteristics of waves in the Indian Ocean based on ERA-40 wave reanalysis     

《Applied Ocean Research》2017

Based on the 45-year (09/1957-08/2008) European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis (ERA-40) wave reanalysis dataset, this study analyzes interannual and interdecadal variabilities and intraseasonal oscillations of sea surface wind speed (WS), wind sea wave height (H^w), swell wave height (H^s) and significant wave height (H_s) in the Roaring Forties and tropical waters of the Indian Ocean, to determine swell propagation characteristics. The results show: (1) monthly variabilities of H^s in the Roaring Forties are in good agreement with those in tropical waters of the Indian Ocean; swell plays a dominant role in mixed waves throughout most of the Indian Ocean; and WS, H^w, H^s, and H_s exhibit a significant increasing trend over the 45-year study period. (2) H^s in the Roaring Forties and tropical waters of the Indian Ocean share a common period of 9.8–10.4 years on an interdecadal scale; and WS and H^s in the Roaring Forties and H^s in the tropical waters of the Indian Ocean share a common period of approximately 8 days (weekly oscillation) on an intraseasonal scale. (3) Swell of the Roaring Forties needs approximately 30 h to fully respond to the wind in this region. Approximately 84 h are required for H^s to propagate from the Roaring Forties to the tropical waters of the south Indian Ocean, while it takes approximately 132–138 h for H^s to propagate from the Roaring Forties to the tropical waters of the north Indian Ocean.  相似文献   

Hydraulic model tests for propagation of flow and sediment in floods due to breaking of a natural landslide dam during a mountainous torrent     

Takahiro Itoh  Akihiko Ikeda  Takahiko Nagayama  Takahisa Mizuyama 《国际泥沙研究》2018,33(2):107-116

During mountain torrents, large-magnitude floods may result from heavy rainfall and cause the breakage of landslide dams naturally formed by heavy rainfall, earthquakes, and so on. The characteristics of longitudinal spreading of clear water discharge and changes in flow depth must be clarified because the changes in peak depth have not yet been examined in steep-slope torrents and because there are few data on spreading of flash floods and related sedimentation in mountainous torrents. In the present study, experimental data were collected through hydraulic model tests over a rigid bed, and the spreading of water, fine sediment, bed load, and large boulders due to flooding are discussed assuming that flash flooding/debris flows occur in the upstream reach. The effects of changes in flow width, such as expansions and contractions in the flow width, as well as changes in meandering channels, sediment transportation, and spreading flow depth resulting from bores are examined using flume data for a steep-slope torrent. The data obtained in the present study reveal that fine sediment components are transported to the downstream reach if large-magnitude floods occur and that the spreading rate and peak lags of the fine sediment and water level indicate the occurrence of a flood in the upstream reach.  相似文献   

冬季欧亚中高纬大气低频振荡的传播及其与欧亚遥相关型的关系   总被引：4，自引：1，他引：3  

杨双艳  武炳义  张人禾  周顺武 《大气科学》2014,38(1):121-132

利用NCEP/NCAR再分析资料,分析了冬季欧亚中高纬大气低频振荡（LFO）的传播特征及其在年际尺度上与同期欧亚大气背景环流场之间的联系。结果表明,冬季欧亚中高纬LFO以10～30 d周期为主,且具有明显向东南方向传播的特征。其经、纬向平均移速分别约为3.4纬度/d和15经度/d。进一步分析发现,冬季欧亚中高纬LFO强度的年际变化与欧亚遥相关型（EU）密切相关。定义乌拉尔地区的脊和东亚、欧洲西北部的槽比常年弱（强）时,即EU指数小于（大于）零时,为EU负（正）位相。当对流层中上层EU处于负位相时,此时,对流层低层的西伯利亚高压强度减弱,这些因素均导致欧亚地区大尺度经向环流偏弱,环流较为平直,不利于LFO的传播;反之亦然。  相似文献   

基于震源-河谷波场数值模拟的坝址地震动参数确定方法   总被引：3，自引：0，他引：3       下载免费PDF全文

贺春晖  王进廷  张楚汉 《地球物理学报》2017,60(2):585-592

针对目前高坝坝址地震动参数确定方法的一些不足,本文尝试了一种基于地震学理论的坝址区三维地震动场生成方法.基本思路是将地震学和工程学结合,针对设定地震,建立震源-传播介质-坝址峡谷场地数值模型,通过超大规模的数值计算,模拟地震波从发震断层破裂开始到坝址场地的物理传播过程,生成坝址区的三维地震动参数.与传统基于衰减关系的地震动参数确定方法相比,这一方法可以考虑震源机制、传播介质和坝址峡谷场地效应等三大要素的影响.对于特定的坝址,可以生成符合实际地质构造、区域岩体动力特性以及坝址峡谷地质地形条件的地震动荷载分布,具有针对性,为重大高坝枢纽工程遭遇极端地震荷载作用时的抗震安全性提供了一种新的分析手段.  相似文献   

热弹性介质中波传播特征     

侯婉婷  符力耘  魏佳  王志伟 《地球物理学报》2021,64(4):1364-1374

深层-超深层油气地震勘探涉及高温介质地震波传播问题,热弹介质参数对地震波传播有重要影响.含弛豫时间修正项的Lord-Shulman双曲型耦合热弹波动方程从理论上预测了热弹性介质中存在快纵波、慢纵波(一种准静态慢纵波,简称热波)和横波的传播,两个纵波为热耗散衰减波而横波不受介质热特性的影响.本文结合平面波频散分析和格林函数法数值模拟,详细研究两个热耗散衰减波的频散和衰减特征,着重分析热导率、热膨胀系数及比热的变化对波速和衰减的影响.研究表明热导率作为主要参数决定了波速与衰减的临界变化,热膨胀系数对波速和衰减的幅度有明显影响,比热则兼顾了前两个热弹系数的影响特征.最后,利用热弹性动力学频率域的二阶格林函数进行波场快照数值模拟,展示热弹性介质中纵波、横波和热波的传播行为.  相似文献   

南大洋淡水通量的气候效应研究进展     

马浩  李春 《地球科学进展》2010,25(2):140-146

南大洋淡水通量在古气候演变中曾经发挥过重要作用,全球变暖背景下的南极融冰事件使南大洋淡水通量成为气候学家关注的焦点。从南大洋淡水通量异常对热盐环流和海平面变化的影响以及异常信号传播路径等3个方面系统分析了各种海洋—大气耦合数值模式的已有研究结果,总结了与这一问题有关的各种不同学术观点,对目前存有争议的问题进行了讨论,并对未来有价值的研究方向和全球变暖背景下这一问题的研究前景进行了展望。  相似文献   

三类物理过程对台风强度影响的研究   总被引：4，自引：2，他引：4  

任健  马镜娴  陈联寿  罗哲贤 《气象学报》2003,61(6):718-732

文中设计了一个极坐标系的准地转正压模式 ,一个直角坐标系定常台风环流条件下的准地转正压模式和一个直角坐标系非定常台风环流的准地转正压模式 ,其径向或水平格距均为 2km ,以研究三类物理过程对台风强度的影响 ,即沿方位角方向的线性平流 ,沿径向的线性平流以及非线性平流对中尺度涡旋涡量内传和台风强度变化的影响。结果指出 :沿方位角方向的线性平流可导致螺旋状涡带的形成 ;沿径向的线性平流在一定的参数集合可使涡量内传 ,台风略有增强 ;定常台风环流条件下扰动涡量的非线性平流可使内传涡量明显增加 ,台风明显增强 ;非定常台风环流条件下非线性平流的作用具有两重性 ,一方面可使内传涡量增多 ,有利于台风的增强 ,另一方面 ,在涡量内传过程中 ,原先呈同心圆轴对称的台风基流结构受到破坏 ,形成复杂流型 ,这又使台风趋于减弱。最后讨论了这些结果在台风强度预测方面的可能应用。  相似文献