东亚-太平洋遥相关型波列对夏季东北亚阻塞高压年际变化的影响   总被引：34，自引：10，他引：24  

陆日宇  黄荣辉 《大气科学》1998,22(5):727-734

利用1980～1988年9年的观测资料,分析了夏季东北亚阻塞高压的年际变化及其与江淮地区夏季降水之间的关系,指出夏季东北亚阻塞高压具有十分明显的年际变化,同时它与江淮地区夏季降水之间存在着较密切的关系:当夏季东北亚阻塞高压频发时,江淮地区降水偏多;而当夏季东北亚阻塞高压维持日数少时,江淮地区降水偏少。为考察产生上述结果的原因,我们分析了全球海温异常,并利用合成的热带西太平洋海温异常模拟研究了热带西太平洋海温异常对东北亚阻塞高压形成和维持的影响。最后指出热带西太平洋海温异常引起的东亚-太平洋型遥相关波列是产生夏季东北亚阻塞高压的年际变化及其与江淮地区夏季降水之间关系的一个重要原因。  相似文献   

考虑供需随机性的道路交通系统震害引发损失期望评估   总被引：6，自引：0，他引：6  

陈艳艳  王光远 《世界地震工程》2003,19(1):25-30

借鉴可靠度理论，通过震后交通需求及道路震后通行能力的随机性分析并考虑灾后不同阶段的交通供需特性，进行交通系统震后阻塞发生的概率分析及引发损失期望预测，从而为抗震加固决策及震后交通管理及修复提供依据。  相似文献   

2003年夏季中高纬度环流与淮河流域降水   总被引：7，自引：4，他引：7       下载免费PDF全文

龚振淞  王永光  许力 《气象》2004,30(2):30-33

研究了 2 0 0 3年夏季中高纬环流特征以及乌拉尔山、鄂霍茨克海和贝加尔湖三个地区阻高指数逐候的变化情况。 6月下旬至 7月上旬东亚中高纬出现“双阻”形势 ,造成淮河流域持续一个多月的集中强降水 ,但是在 7月底 ,鄂霍次克海阻高再度建立并持续 ,致使盛夏西太平洋副热带高压较常年偏南 ,所以雨带的位置也未能北移。因此 2 0 0 3年夏季主要雨带维持在淮河流域  相似文献   

STUDY OF THE NONLINEAR MECHANISM ABOUT THE FORMATION OF BLOCKING HIGH^*          下载免费PDF全文

ZHENG Zuguang  LI Xiuling  LIU Lihong  WU Hong 《Acta Meteorologica Sinica》2004,18(4):423-440

In this paper,a nonlinear dynamical system considering the interactions among ultra-long wave,long wave and zonal flow in a baroelinic atmosphere was found.In this system,thermal forcing and frictional dissipation are regarded as the external parameters.The procedure,in which the maps of orbit in phase space,contour of stream function and section of Poincaré mapping are combined with each other,is used to determine the distributions of system states and circulation patterns and to draw the corresponding diagrams.The results show that by using the Galerkin method,there is no essential influence of the increasing of orders of truncated-spectrum in a certain range on the distributions of system states and circulation patterns,but it makes them somewhat complexities.By contrast,the changing of distribution of thermal forcing exerts a great influence on the system.Blocking high links closely with the oscillating of the atmospheric circulation and the meridional growing intensely,while the development of synoptic wave can promote the oscillating.  相似文献   

泥石流堵断主河临界条件研究进展          下载免费PDF全文

宋志 《沉积与特提斯地质》2015,35(3):109-112

自20世纪90年代开始,泥石流堵断主河临界条件研究取得了较大进展,开展了多动态室内模拟试验、统计学的相关性分析、动量动能的理论力学分析,取得了基于不同方法的临界条件判别式,但对泥石流堵河的力学形成机制、堵河的数值模拟、堵河原型模拟试验、多时段的遥感运用等方面的研究仍需解决和深入。前人所做的临界条件往往对具体环境下的单沟能够较好适应,而对一定数量的其它泥石流堵河事件往往对比验证较差。对泥石流堵河临界条件的研究需要运用到土力学、水力学等学科的相关理论才能解决。作者认为,在前人研究的基础上,未来研究方向应着重于泥石流堵河机理研究、RS、GIS技术的应用、原型模拟堵河试验及判别式研究,也许能有效地解决泥石流堵河临界条件的科学性和正确性,为实现防灾减灾提供科学的依据。  相似文献   

滨里海盆地东缘盐构造特征及其与乌拉尔造山运动关系   总被引：1，自引：0，他引：1  

杨孝群  汤良杰  朱勇 《高校地质学报》2011,17(2):318-326

通过对滨里海盆地东缘地震剖面的解释,揭示了丰富多样的盐构造变形特征及其与乌拉尔造山运动的关系。滨里海 盆地东缘盐构造变形样式主要包括盐底辟、盐枕、盐滚、盐焊接、龟背构造和盐边凹陷等,表现出明显的分带变形特征, 自东向西依次为盐焊接带、盐滚带、盐枕带、盐底辟带。盐层控制了盐上层和盐下层的构造变形,以盐层为界,上构造层 主要发育正断层,下构造层主要发育逆断层。平衡剖面分析表明,滨里海盆地东缘盐构造变形主要经历了重力变形和差异 负载变形两个阶段,并与乌拉尔造山运动有紧密联系。乌拉尔造山运动引起滨里海盆地东缘地层发生倾向反转,进而控制 了盐层沉积及随后的重力变形和差异负载变形过程。  相似文献   

基桩对含水层渗流阻挡作用效应研究     

曹依雯  黄润秋  沈水龙  许烨霜  马磊 《岩土力学》2014,35(6):1617-1622

超高层建筑的桩基础通常会打入到深度较大的承压含水砂土层中;在承压含水层的上方通常会进行超深基坑的开挖构建超高层建筑的地下室。为了保持超深基坑的基底稳定,需要在承压含水层中进行降水施工。由于深基坑存在大量的桩基础,基桩的存在会影响降水时地下水的渗流路径,继而影响土体的渗透性状。应用室内试验研究基桩对含水层渗流阻挡作用的机制。试验采用PVC管模拟基桩,将颗粒较均匀的砂土作为试验土体,通过室内渗流试验来研究基桩对地下水渗流的影响。试验结果表明,基桩对于地下水渗流有明显的阻挡效应：基桩的数量以及布置形式会对渗透效应产生较大的影响。考虑砂土体积置换率的有效介质理论可以用来分析矩形布置的基桩对渗透系数的影响,但对梅花形布置的基桩应用有效介质理论计算所得的渗透系数会有将近20%的偏差;其原因是梅花形布置的基桩,会使渗流路径增加。基于对渗流路径的分析,提出了考虑有梅花形布置的基桩存在时等效渗透系数计算的修正方法。  相似文献   

WAVE-FLOW INTERACTIONS IN THE ATMOSPHERIC LOW-FREQUENCY VARIATION OF BLOCKING PATTERN^*          下载免费PDF全文

GAO Shouting  ZHU Wenmei  DONG Min 《Acta Meteorologica Sinica》2000,14(4):442-458

Through a simple review of low-frequency variation of blocking pattern and diagnoses of observational data and combining some experience in forecast practice,we put forward some thought about the mechanism of formation and maintenance of the blocking flow pattern from the synoptic/climatological point of view,It is emphasized that eastward moving and deepening of troughs in the upstream of the blocking high,the SST anomalies and topography effect are the main factors of impelling the variation of the blocking high.During the maintenance of Ural blocking high wave-flow interactions are studied through disposition of baroclinic trough(transient wave)and the blocking flow.This study will offer a primary basis for the further theoretical study on the formation mechanism of the blocking high.  相似文献   

1998年与1954年夏季大尺度环流特征的对比分析   总被引：7，自引：0，他引：7  

晁淑懿  李月安 《气象》2000,26(1):38-42

对比分析夏季发生在长江全流域两次特大洪涝的１９５４年和１９９８年大尺度环充的特征。指出１９５４年西北太平洋副热带高压第二次季节性北跳明显偏迟,出现在８月初,６～７月副高位置持续偏南,８月副高位置偏北;而１９９８年副高第二次季节性北跳偏早,出现在７月上旬中期,但盛夏７月下旬～８月底副高位持续偏南,这两年夏季亚洲西凤带阻塞高压活动都十分频率,１９９８年更甚。夏季赤道辐合带１９９８年明显弱于１９５４年。  相似文献   

Petrotectonic evolution of the high- to ultrahigh-pressure Maksyutov Complex, Karayanova area, south Ural Mountains: structural and oxygen isotope constraints     

Mary L. Leech  W. G. Ernst 《Lithos》2000,52(1-4):235-252

The Maksyutov Complex consists of three fault-bounded lithologic units: a quartzofeldspathic gneiss containing mafic eclogite boudins (Unit #1); a metasedimentary blueschist-facies (Yumaguzinskaya) unit; and a meta-ophiolitic mélange (Unit #2). The geologic history of the high- to ultrahigh-pressure (HP–UHP) assembly of the Maksyutov Complex is complicated by several stages of prolonged retrograde metamorphism and deformation. The Sakmara River exposes all three units near the former village of Karayanova. A structural/petrologic cross-section through the area yields new quantitative data for the complex and, regionally, for the south Urals. Analysis of the Karayanova area has identified the major structures. Regional folding within the complex is parallel to the dominant foliation trending northeast–southwest. Stereonet data show that, during exhumation, this large-scale folding was refolded about axes trending southeast. Unit #1 and the Yumaguzinskaya are tectonically and petrologically distinct units juxtaposed by west-vergent thrusting and recrystallization within the same subduction zone. A shear zone developed later between Unit #2 and the Unit #1+Yumaguzinskaya tectonic package accompanying exhumation. Field relations and petrofabric demonstrate that blueschist-facies recrystallization overprinted an earlier eclogite-facies metamorphism. Thermobarometric measurements yield P–T values of 594–637°C, 1.5–1.7 GPa for eclogite, but these conditions may reflect annealing during the early-stage exhumation at 375 Ma. Cuboid graphite aggregates testify to precursor conditions for Unit #1 within the diamond stability field, if such textures are correctly interpreted. Measured ¹⁸O/¹⁶O partitioning between pairs of coexisting phases yield three main recrystallization temperature ranges: (1) 678±83°C, attending Unit #1 eclogite-facies metamorphism; (2) 453±17°C, during transitional blueschist/greenschist-facies metamorphism for the amalgamated Unit #1+Yumaguzinskaya+Unit #2 assembly; and (3) 250±68°C, reflecting late-stage hydrothermal alteration and exhumation. Oxygen isotope data for Units #1 and #2 indicate that garnet, blue amphibole, and pyroxene crystallized in isotopic equilibrium, validating previous thermobarometric calculations for a Unit #1 retrograde metamorphic event. Variations in δ¹⁸O values for phengites suggest the possibility of late metamorphic fluid infiltration. Retrograde recrystallization at high pressure in the presence of fluids and a calculated slow exhumation rate for the Maksyutov Complex account for the fact that inferred UHP coesite and diamond were completely back-reacted during decompression.  相似文献