急流在梅雨期持续暴雨过程中的作用   总被引：11，自引：6，他引：5  

赵娴婷  魏建苏  朱定真 《气象科学》2011,31(2):211-216

本文利用实况资料和客观分析资料,对造成江苏2010年7月9-14日的暴雨过程中高低空急流特点、配置及对暴雨的影响进行了分析.结果表明:高空动量下传,引起低空扰动加强,从而使得低空急流加强和维持.低层高能的平流为江苏境内暴雨和大暴雨的产生提供了充足的能量.低空西南风急流是暴雨产生的重要因子,仅在700 hPa出现强劲西南风急流,就可以导致江苏境内的强降水发生.分析还表明:阶段性暴雨起始的时候,暴雨落区上方都出现了负散度和正散度相互交错的情况,直至6h后才有高空辐散低空辐合的典型形势.高低层急流配置和次级环流的维持为暴雨的持续提供了有利条件.  相似文献   

南海中北部陆缘横波速度结构及其构造意义   总被引：6，自引：2，他引：4       下载免费PDF全文

卫小冬  赵明辉  阮爱国  丘学林  郝天珧  吴振利  敖威  熊厚 《地球物理学报》2011,54(12):3150-3160

纵横波联合勘探可以得到更多关于岩石圈层岩性、物性等介质属性方面的信息,有效提高地壳物质组成的约束性.在纵波速度结构模型的基础上,通过射线追踪和走时拟合对OBS2006-3地震剖面径向分量的转换震相进行了横波速度结构模拟.结果表明:沉积层1、沉积层2的横波速度分别为0.7～0.9 km/s和1.6～1.7 km/s,波速...  相似文献   

对汶川8.0级地震前四川地区地形变类观测异常的研究     

程万正  苏琴  孙毅 《四川地震》2011,(1):1-10

研究给出四川地区跨断层短水准、短基线和固定形变台在汶川8.0级地震前出现的异常现象.四川地区跨断层流动垂直、水平形变观测场地观测,在汶川8.0级地震前出现中长期趋势异常的场地数为6个,1个为长期趋势异常,其余5个为中期趋势异常.异常观测场地比为6/31=0.19.其中,龙门山断裂带所在的川北地区有4处跨断层流动短水准观...  相似文献   

Preliminary study of lateral variation in crustal structure of Northeast China from teleseismic receiver functions     

Youlin Chen  Ruifeng Liu Zhibin Huang  Li Sun Array Information Technology  Maryl  USA China Earthquake Networks Center  Beijing  China 《地震学报(英文版)》2011,(1)

We conducted comprehensive receiver function analyses for a large amount of high-quality broadband teleseismic waveforms data recorded at 19 China National Digital Seismic Network (CNDSN) stations deployed in Northeast China.An advanced H-κ domain search method was adopted to accurately estimate the crustal thickness and vP/vS ratio.The crust has an average thickness of about 34.4 km.The thinnest crust occurs in the central region of Northeast China,while the thickest crust is beneath the Yanshan belt.The v...  相似文献   

长江中下游浅水湖泊沉积物腐殖质组分赋存特征   总被引：9，自引：3，他引：6  

易文利  王圣瑞  杨苏文  赵海超  金相灿  王国栋 《湖泊科学》2011,23(1):21-28

应用化学方法,对长江中下游浅水湖泊表层沉积物有机质含量、腐殖质组成及结合形态进行了研究.结果表明:①长江中下游浅水湖泊11个沉积物的有机质含量变化较大.在0.98%-11.0%之问波动.污染程度重的沉积物中有机质含量均较污染程度轻的高.其有机质的分布特征与沉积物污染程度和湖泊周边的人类活动有关.②腐殖质组成中,胡敏酸(...  相似文献   

长江中下游地区铜矿体综合找矿模型     

刘因  李功成 《火山地质与矿产》2011,(1):17-22

本文在收集研究长江中下游地区主要铜矿床的发现和勘查过程、矿床地质特征、物化探异常特征、勘查方法等大量资料的基础上,对矿体特征进行了归纳,提出了将长江中下游主要铜矿体划分为二型四式的矿体类型划分方案。分别建立了四种类型铜矿体的找矿模型,并建立了铜矿体综合找矿模型。  相似文献   

Lower crustal melting via magma underplating: Elemental and Sr–Nd–Pb isotopic constraints from late Mesozoic intermediate–felsic volcanic rocks in the northeastern North China Block     

CHAOWEN LI  FENG GUO  WEIMING FAN 《Island Arc》2011,20(4):477-499

Ar–Ar dating, major and trace element analyses, and Sr–Nd–Pb isotope results of two groups of Lower Cretaceous (erupted at 126 and 119 Ma, respectively) intermediate–felsic lava from the northeastern North China Block (NCB) suggest their derivation from melting of mixtures between the heterogeneous lower crust and underplated basalts. Both groups exhibit high‐K calc‐alkaline to shoshonitic affinities, characterized by light rare earth element (LREE) and large ion lithophile element (LILE) enrichment and variable high field strength element (HFSE, e.g. Nb, Ta and Ti) depletion, and moderately radiogenic Sr and unradiogenic Nd and Pb isotopic compositions. Compared with Group 2, Group 1 rocks have relatively higher K₂O and Al₂O₃/(CaO + K₂O + Na₂O) in molar ratio, higher HFSE concentrations and lower Nb/Ta ratios, and higher Sr–Nd–Pb isotope ratios. Group 1 rocks were derived from a mixture of an enriched mantle‐derived magma and a lower crust that has developed radiogenic Sr and unradiogenic Nd and Pb isotopic compositions, whereas the Group 2 magmas were melts of another mixture between the same mantle‐derived component and another type of lower crust having even lower Sr, Nd, and Pb isotopic ratios. Shift in source region from Group 1 to Group 2 coincided with a change in melting conditions: hydrous melting of both the underplated basalt and the lower crust produced the earlier high‐Nb and low‐Nb/Ta melts with little or no residual Ti‐rich phases; while the younger low‐Nb and high‐Nb/Ta magmas were melted under a water‐deficient system, in which Ti‐rich phases were retained in the source. Generation of the two groups of intermediate–felsic volcanic rocks was genetically linked with the contemporaneous magma underplating event as a result of lithospheric thinning in the eastern NCB.  相似文献   

用拉萨点大地测量资料检测青藏高原地壳的增厚   总被引：3，自引：0，他引：3  

邢乐林  孙文科  李辉  杨光亮 《测绘学报》2011,40(1):41-44

青藏高原地壳的隆升与增厚,是一个复杂的热点问题.印度板块和欧亚板块的碰撞挤压导致地壳的隆升与增厚,已被地质、构造学等方面资料证实,但利用大地测量资料定量确定高原地下地壳增厚速率的很少.基于此,利用高精度绝对重力测量资料及GPS结果定量检测高原拉萨点地下地壳增厚速率((3.9±0.8)cm/a),并给出简单的动力学模型,...  相似文献   

长江流域夏季气温变化型及其成因Ⅰ：年际变化与遥相关   总被引：2，自引：1，他引：1  

蔡佳熙  管兆勇 《气象学报》2011,69(1):99-111

采用中国气象局整编的气温资料、NCEP/NCAR再分析资料、哈得来月平均海温资料以及CPC(NOAA)指数,分析了长江流域夏季气温的变化型及其成因.结果表明:长江中下游地区夏季气温呈现出全区一致、南北反相以及东西反相3种分布型,且这3种分布型分别是中国同号气温异常变化、南北反号气温异常以及东西反号气温异常分布背景下的局部反映.上述这3种气温异常型具有显著的年际和年代际变化特征,其中在年际尺度上具有2-5年的周期,反映出在年代际背景下的年际变化;在年际尺度上,3种异常型分别对应不同特点的环流型,并且高度场在长江中下游地区上空的垂直分布均呈准正压结构;3种异常型对应的环流型的维持分别与来自大西洋穿越极区的波列,由地中海沿亚洲急流东传的波列以及北半球环状模有关.同时,全区一致型和南北反相型与P-J型波列联系紧密,其中南北反相型与该波列联系更为紧密;全区一致型与Nino3海温指数呈负相关关系,其中超前一季的负相关最大.南北反相型与Nino3海温指数超前2季相关最高,与Nino4海温指数同时相关最高.东西反相型则与Nino3海温指数同时相关最高,与Nino4海温指数超前3季相关最高.这些结果可为进一步认识长江流域夏季气温变化规律和极端天气气候事件的预测提供线索.  相似文献   

A mechanism for the origin and development of the large-scale dunefield on the right flank of the lower reach of Laoha River, Northeast China     

Guang Han  GuiFang Zhang  Li You  Liang Zhou  Lin Yang  XueYong Zhao  YuLin Li  TongHui Zhang 《寒旱区科学》2015,7(1):0029-0039

By viewing satellite imagery, a striking large-scale dunefield can be clearly perceived, with a size of nearly 63 km long and 11 km wide, and trending NE–SW, on the right flank of the lower Laoha River, Northeast China. By means of remote sensing imagery analysis and field observation as well as a comparison with a small-scale dunefield on the right flank of the lower Xiangshui River, analogous to the case of the lower Laoha River, this paper presents a new mechanism for its origin and development. The results show that:(1) the large-scale dunefield bears a tile-style framework overwhelmingly composed of transverse barchanoid ridges perpendicular to the predominant winds, and inlaid diverse blowouts.(2) The small-scale dunefield, referred to as a primary structural unit of the large one, is typical of an incipient dunefield, following the same rules of evolution as the larger.(3) A succession of barchanoid ridge chains can steadily migrate downwind in much the same manner as surface wave propagation in air or water stimulated by an incised valley, and ultimately tend to bear roughly the same wavelength and amplitude under stable climate and hydrologic regimes.(4) The first ridge chain acquires its sand source substantially from the downwind escarpments exposing the loose Quaternary sandy sediments to the air, while the ensuing ridges derive their sands dominantly from in situ deflation of the underlain Quaternary loose sandy sediments in blowouts, partly from the upwind ridges through northern elongated horns. Theoretically, the sands from riparian escarpments can be transported by wind to the downwind distal end of a dunefield after sufficient long duration.(5) The lower Laohahe region experienced probably three significant climatic changes in the past, corresponding to the three active dune belts, suggesting that once a large-scale dunefield occurs, it is nearly impossible to be completely stabilized, at least in its central portions. At present, seasonal shrinkage and stagnation of the lower Laoha River, widespread farming and afforestation in the valley, and establishing windbreaks downwind of the valley as well as surrounding the dunefield, appear to have significantly modified local flow fields and sand sources, engendering significant degradation of the dunefield.  相似文献