我国北方地区雷电活动的时空特征   总被引：25，自引：3，他引：22  

张敏锋  刘欣生  葛正谟 《高原气象》2000,19(3):277-284

利用地闪定位仪（ＤＦ）探测了我国大兴安岭（东北地区）和北京地区的雷电活动。文中详细分析了地闪的空间分布,并讨论了不同地区各雷电参量的时间变化规律。两地区雷电活动的季节变化与日变化均有较大差异。这些差异的产生可能与本地区的天气背景及地理特征有密切的联系。要较深入地了解上述差异产生的可能原因,将雷电活动与天气因子的给合讨论是必需的。  相似文献   

中国东北松嫩平原地下水水化学特征与演变规律   总被引：32，自引：0，他引：32       下载免费PDF全文

章光新  邓伟  何岩  Ramsis Salama 《水科学进展》2006,17(1):20-28

在全球气候变化和高强度人类活动的影响下,松嫩平原地下水环境日益恶化,已成为制约生态环境建设和经济社会发展的重要因素。选取具有典型代表意义的洮儿河流域作为研究区,对地下水进行系统取样分析,综合运用描述性统计、相关性分析、离子比例系数和Piper三角图示法,全面系统地研究地下水水化学的时空变异特征与演变规律,揭示了风化溶滤、蒸发浓缩、阳离子交换和人为混合是控制地下水质演变的主要水文化学过程,从而为流域乃至松嫩平原盐渍土区水资源可持续开发利用和管理提供科学依据。  相似文献   

时态GIS的空间实体关联技术应用研究   总被引：1，自引：0，他引：1  

俞松  唐新明  雷兵  杨平  周晓青 《测绘科学》2006,31(3):117-118,126

在自然界中大多数现实世界的实体都是动态的,地图上的公路、铁路、居民地等只是相对于一个很短的时间里是静态的,经过一个长的时间这些实体都将发生改变。本文根据不同时态地理实体的各种特征比较,将两个时态的数据进行关联,建立几何、位置和属性的变化模型,将这个动态的过程表现出来。试验表明,本文的算法是有效的。  相似文献   

面向对象时空数据模型的研究   总被引：4，自引：0，他引：4  

宋玮  王家耀  郭金华 《测绘科学技术学报》2006,23(4):235-238

时空数据模型是建立TGIS的基础.首先指出了建立时空数据模型中应该考虑的问题,同时指出面向对象时空数据模型的优越性;然后提出了面向对象的时空数据模型.指出地理世界抽象是由时空属性对象组成,每个时空属性对象由空间、属性、时间3部分组成.系统分析了时空属性对象各个组成部分之间的关系并通过UML进行了表达.最后,以地籍管理中的宗地为例说明了该数据模型的实现.  相似文献   

对空间数据不确定性研究的思考   总被引：2，自引：0，他引：2  

李德仁 《测绘科学技术学报》2006,23(6):391-392,395

对GIS中空间数据不确定性研究中存在的问题进行思考后提出了5点建议.主要包括:1) 要区分GIS中确定性目标和不确定性目标;2) 要区分用离散点逼近曲线/曲面的逼近误差和离散点自身量测误差及其传播;3) 要研究GIS中的几何不确定性,更要重视研究属性和时态不确定性;4) 要研究空间数据质量,更要研究空间信息服务的质量;5) 空间数据不确定性研究要努力向实际应用转化.  相似文献   

黔东南暴雨气候特征及其地形影响   总被引：2，自引：2，他引：2  

顾欣田楠  潘平珍 《气象科技》2006,34(4):441-445

利用1960~2000年贵州省黔东南地区降水观测资料,统计分析黔东南地区暴雨时空分布特征,进一步揭示其活动规律及主要影响因素。结果表明:黔东南地区暴雨有显著年代际变化特征,存在准15年的周期变化,并与贵州降水和长江中下游降水呈同位相;存在两个暴雨多发中心,夜间暴雨较多。黔东南暴雨地域分布极为复杂,局地性暴雨较多,这与黔东南特殊地形有着密切关系,地形因素是影响黔东南地区暴雨的重要原因,对形成上述特征的气候学成因做了初步讨论。  相似文献   

Decreasing Reference Evapotranspiration in a Warming Climate—A Case of Changjiang (Yangtze) River Catchment During 1970–2000   总被引：1，自引：0，他引：1  

许崇育  龚乐冰  姜彤  陈德亮 《大气科学进展》2006,23(4):513-520

This study deals with temporal trends in the Penman-Monteith reference evapotranspiration estimated from standard meteorological observations, observed pan evaporation, and four related meteorological variables during 1970–2000 in the Yangtze River catchment. Relative contributions of the four meteorological variables to changes in the reference evapotranspiration are quantified. The results show that both the reference evapotranspiration and the pan evaporation have significant decreasing trends in the upper, the middle as well as in the whole Changjiang (Yangtze) River catchment at the 5% significance level, while the air temperature shows a significant increasing trend. The decreasing trend detected in the reference evapotranspiration can be attributed to the significant decreasing trends in the net radiation and the wind speed.  相似文献   

对空间数据不确定性研究的思考     

李德仁 《测绘学院学报》2006,(6)

对GIS中空间数据不确定性研究中存在的问题进行思考后提出了5点建议。主要包括:1)要区分GIS中确定性目标和不确定性目标;2)要区分用离散点逼近曲线/曲面的逼近误差和离散点自身量测误差及其传播;3)要研究GIS中的几何不确定性,更要重视研究属性和时态不确定性;4)要研究空间数据质量,更要研究空间信息服务的质量;5)空间数据不确定性研究要努力向实际应用转化。  相似文献   

Joint processing and analysis of seismic gravity measurements in Capital Circle area     

贾民育马丽  刘少明张晶孙少安  王武星 《地震学报(英文版)》2006,19(4):438-447

In Capital Circle area, there are three groups of repeated gravity measurements observed by different institutes using different instruments or methods. The simultaneous adjustment of absolute and relative measurements and the elimination of systematic error among the relative measurements have been carded out in this paper. Thus an unified temporal gravity change system with absolute reference has been established. On the basis of this, the crustal subsidence effect on gravity, which belongs to non-tectonic factor, is analyzed and the station displacement corrections are carried out, so that the long-wave disturbance is eliminated. So far our following aims are realized： the advantages of the absolute and relative measurement methods are complementary to each other; the contradiction and environment disturbance are eliminated; the amounts of information are enlarged; the sampling interval of time domain is compressed. In a word, the ability of identifying the tectonic activity process is enhanced. The results show that： there are systematic errors between the two groups of relative measurements and within the data of 10 campaigns ; the uneven local crustal subsidence in the southeast of the study area results in a linear rise of gravity value at 10 stations; they can be corrected by the regression analysis. The maps of revised temporal gravity change can obviously and integrally reflect the Ms=5.0 earthquake in Guye on October 6, 1995.  相似文献   

Can Damage Mechanics Explain Temporal Scaling Laws in Brittle Fracture and Seismicity?     

Donald L. Turcotte  Robert Shcherbakov 《Pure and Applied Geophysics》2006,163(5-6):1031-1045

Time delays associated with processes leading to a failure or stress relaxation in materials and earthquakes are studied in terms of continuum damage mechanics. Damage mechanics is a quasi-empirical approach that describes inelastic irreversible phenomena in the deformation of solids. When a rock sample is loaded, there is generally a time delay before the rock fails. This period is characterized by the occurrence and coalescence of microcracks which radiate acoustic signals of broad amplitudes. These acoustic emission events have been shown to exhibit power-law scaling as they increase in intensity prior to a rupture. In case of seismogenic processes in the Earth's brittle crust, all earthquakes are followed by an aftershock sequence. A universal feature of aftershocks is that their rate decays in time according to the modified Omori's law, a power-law decay. In this paper a model of continuum damage mechanics in which damage (microcracking) starts to develop when the applied stress exceeds a prescribed yield stress (a material parameter) is introduced to explain both laboratory experiments and systematic temporal variations in seismicity.  相似文献