暴雨的多普勒天气雷达速度辐合风场特征   总被引：11，自引：3，他引：8  

王彦  吕江津  周海光  王丽荣  吴彬贵 《气象》2008,34(3):63-68

多普勒天气雷达探测大范围强降水时,其多普勒速度回波特征既不同于单纯的暖(冷)平流的特征(S或反S形)也不同于纯粹的大尺度辐合(散)运动特征(弓状), 而是暖(冷)平流和辐合(散) 两种运动相结合的风场(称之为复合风场)所产生的多普勒速度特征.应用天津塘沽新一代天气雷达资料,并结合自动气象站资料和改进的EVAD 技术,分析2005年8月16日发生在海河流域的一次大范围、长时间的强降雨天气过程的多普勒天气雷达资料.结果表明:(1)当低层出现暖平流和辐合运动相结合的复合风场特征时,即多普勒天气雷达速度场产品表现为自雷达中心开始,在同一距离圈上,一侧的零速度线弯向正速度区的顺转程度明显大于另一侧的零速度线弯向负速度区的顺转程度,即负速度区面积大于正速度区的面积时,降水就增强或维持.(2)当低层出现暖平流和辐散运动相结合的复合风场特征时,对应降水减弱或停止.这种对雷达速度场的辐合辐散分析将对大范围强降水的形成、发展、维持和消散具有很好的临近预报指示作用.  相似文献   

气象卫星资料在估测热带气旋强度方向的应用进展   总被引：3，自引：1，他引：2  

刘喆  朱元竞  李万彪  韩志刚  张凤英 《热带气象学报》2008,24(5):550-556

在常规观测资料稀少的热带洋面上,气象卫星是监测热带气旋的主要工具.基于可见光和红外的Dvorak技术通过一系列经验规则,将热带气旋在卫星云图中表现出来的云系结构特征及特定的参数同其发展强度联系起来,但它无法得到气旋内部辐射信息.相对而言,波长较长的微波能穿透热带气旋中高层云系,反映出与热带气旋强度相关的暖核辐射信息.介绍了国内外利用Dvorak技术和星载微波技术估测热带气旋强度的研究进展,指出它们在应用中存在的优势和不足,同时展望了该领域在未来的发展方向.  相似文献   

Baily’s Beads Atlas in 2005 – 2008 Eclipses     

C. Sigismondi  D. W. Dunham  K. Guhl  S. Andersson  H. Bode  O. Canales  P. Colona  O. Farago  M. Fernández-Ocaña  A. Gabel  M. Haupt  C. Herold  R. Nugent  P. Oliva  M. Patel  C. Perello  W. Rothe  J. Rovira  T. Schaefer  C. Schnabel  D. Schwartz  A. Selva  W. Strickling  A. Tegtmeier  C. Tegtmeier  B. Thome  W. H. Warren 《Solar physics》2009,258(2):191-202

In the annular or total eclipses of 3 October 2005, 29 March 2006, 22 September 2006, and 1 August 2008, observational campaigns were organized to record the phenomenon of Baily’s beads. These campaigns were internationally coordinated through the International Occultation Timing Association (IOTA) at both its American and European sections. From the stations in the northern and southern zones of grazing eclipse, the eclipses have been recorded on video. Afterward, as many beads as possible have been identified by analyzing the video data of each observing station. The atlas presented in this paper includes 598 data points, obtained by 23 observers operating at 28 different observing stations. The atlas lists the geographic positions of the observing stations and the observed time instants of disappearance or reappearance of beads, identified by an angle measured relative to the Moon’s axis of rotation. The atlas will serve as a basis for determining the solar diameter. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.  相似文献   

Climatic implications of correlated Upper Pleistocene glacial and fluvial deposits on the Cinca and Gállego Rivers (NE Spain) based on OSL dating and soil stratigraphy     

Claudia J. Lewis  Eric V. McDonald  Carlos Sancho  Jos Luis Pea  Edward J. Rhodes 《Global and Planetary Change》2009,67(3-4):141-152

We correlate Upper Pleistocene glacial and fluvial deposits of the Cinca and Gállego River valleys (south central Pyrenees and Ebro basin, Spain) using geomorphic position, luminescence dates, and time-related trends in soil development. The ages obtained from glacial deposits indicate glacial periods at 85 ± 5 ka, 64 ± 11 ka, and 36 ± 3 ka (from glacial till) and 20 ± 3 ka (from loess). The fluvial drainage system, fed by glaciers in the headwaters, developed extensive terrace systems in the Cinca River valley at 178 ± 21 ka, 97 ± 16 ka, 61 ± 4 ka, 47 ± 4 ka, and 11 ± 1 ka, and in the Gállego River valley at 151 ± 11 ka, 68 ± 7 ka, and 45 ± 3 ka. The times of maximum geomorphic activity related to cold phases coincide with Late Pleistocene marine isotope stages and Heinrich events. The maximum extent of glaciers during the last glacial occurred at 64 ± 11 ka, and the terraces correlated with this glacial phase are the most extensive in both the Cinca (61 ± 4 ka) and Gállego (68 ± 7 ka) valleys, indicating a strong increase in fluvial discharge and availability of sediments related to the transition to deglaciation. The global Last Glacial Maximum is scarcely represented in the south central Pyrenees owing to dominantly dry conditions at that time. Precipitation must be controlled by the position of the Iberian Peninsula with respect to the North Atlantic atmospheric circulation system. The glacial systems and the associated fluvial dynamic seem sensitive to 1) global climate changes controlled by insolation, 2) North Atlantic thermohaline circulation influenced by freshwater pulses into the North Atlantic, and 3) anomalies in atmospheric circulation in the North Atlantic controlling precipitation on the Iberian Peninsula. Our scenario of glacial and fluvial evolution during the Late Pleistocene in northern Spain could be extrapolated to other glaciated mountainous areas in southern Europe.  相似文献   

The sensitivity of the next generation of lunar Cherenkov observations to UHE neutrinos and cosmic rays     

C.W. James  R.J. Protheroe   《Astroparticle Physics》2009,30(6):318-332

We present simulation results for the detection of ultra-high energy (UHE) cosmic ray (CR) and neutrino interactions in the Moon by radio-telescopes. We simulate the expected radio signal at Earth from such interactions, expanding on previous work to include interactions in the sub-regolith layer for single dish and multiple telescope systems. For previous experiments at Parkes, Goldstone (GLUE), and Kalyazin we recalculate the sensitivity to an isotropic flux of UHE neutrinos. We find the published sensitivity for the GLUE experiment to be too high (too optimistic) by an order of magnitude, and consequently the GLUE limit to be too low by an order of magnitude. Our predicted sensitivity for future experiments using the Australia Telescope Compact Array (ATCA) and the Australian SKA Pathfinder (ASKAP) indicate these instruments will be able to detect the more optimistic UHE neutrino flux predictions, while the square kilometre array (SKA) will also be sensitive to all bar one prediction of a diffuse ‘cosmogenic’, or ‘GZK’, neutrino flux.Outstanding theoretical uncertainties at both high-frequency and low-frequency limits currently prevent a reliable estimate of the sensitivity of the lunar Cherenkov technique for UHE cosmic ray (CR) astronomy. Here, we place limits on the effects of large-scale surface roughness on UHE CR detection, and find that when near-surface ‘formation-zone’ effects are ignored, the proposed SKA low-frequency aperture array could detect CR events above 56 EeV at a rate between 15 and 40 times that of the current Pierre Auger Observatory. Should further work indicate that formation-zone effects have little impact on UHE CR sensitivity, observations of the Moon with the SKA would allow directional analysis of UHE cosmic rays, and investigation of correlations with putative cosmic ray source populations, to be conducted with very high statistics.  相似文献   

Pb-Pb dating of black shales from the Lower Cambrian and Neoproterozoic strata, South China   总被引：2，自引：0，他引：2  

Yong-Quan Chen  Shao-Yong Jiang  Hong-Fei Ling 《Chemie der Erde / Geochemistry》2009,69(2):183-190

Black shales occur widely in the Lower Cambrian and Neoproterozoic strata on the Yangtze Platform, South China. In this study, Lower Cambrian black shales from Xiuning section and Late Neoproterozoic black shales from Weng’an section were studied and Pb isotopic compositions were analyzed following a stepwise acid-leaching technique. The ²⁰⁶Pb/²⁰⁴Pb ratios in both sections show large variations, from 18.906 to 43.737 in the Weng’an section and from 24.811 to 38.110 in the Xiuning section. In contrast, the ranges for ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb values in both sections are relatively smaller from 15.649 to 17.126 and 37.744-38.199 in the Weng’an section, and from 16.034 to 16.783 and 38.602-39.391 in the Xiuning section, respectively. These data yielded two Pb isotope isochron ages of 536±39 and 572±36 Ma, respectively. These ages well accord with other published data and we suggest that they represent the depositional ages for the Lower Cambrian Hetang Formation and the upper Neoproterozoic Doushantuo Formation in South China.  相似文献   

四川省九龙县黑牛洞富铜矿矿床黑云母40Ar-39Ar测年及其地质意义   总被引：6，自引：1，他引：5  

马国桃 《地质学报》2009,83(5):671-679

四川省九龙县黑牛洞铜矿床为近期新发现的一个规模在中型以上,产于江浪变质核杂岩中的富铜矿床。本文测试了黑牛洞铜矿床中与成矿密切相关的黑云母的40Ar/39Ar年龄为136.43±0.77 Ma,说明黑牛洞矿床形成于燕山中期。结合矿区附近李伍富铜床矿床地质特征及成矿年龄,表明黑牛洞铜矿床与李伍铜矿床为同一时期形成的矿床,两者成矿与松潘－甘孜造山带大规模岩浆热事件有关,这对于重新认识李伍铜矿床外围找矿潜力和进一步指导找矿工作具有重要意义。  相似文献   

内蒙古苏莫查干敖包萤石矿区流纹岩锆石SHRIMP定年及地质意义   总被引：5，自引：1，他引：4  

聂凤军  许东青  江思宏  胡朋 《地质学报》2009,83(4):496-504

内蒙古苏查（苏莫查干敖包）萤石矿区晚古生代火山沉积岩分布广泛,主要岩石类型有碳泥质板岩、结晶灰岩、凝灰岩、千枚岩、英安岩和流纹岩,其中碳泥质板岩和流纹岩为苏查特大型萤石矿床的顶和底板围岩。采用锆石SHRIMP UPb铅法分别对底板围岩中蚀变流纹岩和顶板围岩中未蚀变流纹岩样品进行了同位素年代测定,所获数据分别为276±10 Ma和271±8 Ma。蚀变和未蚀变流纹岩的形成时间均为海西晚期（早二叠世）。苏查萤石矿区早二叠世流纹岩是华北陆台与西伯利亚板块从碰撞挤压到松弛张裂转折期,酸性岩浆喷发活动的产物,其成岩物质来自壳、幔混合源。早二叠世流纹岩的出现不仅标志着苏查到西里庙地区海西期构造岩浆活动的终结,同时也为苏查特大型萤石矿床的成矿作用提供了动力、热力和物质来源。早二叠世流纹岩成岩时代的厘定不仅为阐明华北陆台北缘西段构造演化历史提供了科学依据,而且对于查明流纹岩的原岩性质和圈定新的萤石矿床找矿靶区也具有重要意义。  相似文献   

赣南漂塘钨矿花岗岩成岩年龄与成矿年龄的精确测定   总被引：25，自引：1，他引：24  

张文兰 《地质学报》2009,83(5):659-670

漂塘钨矿是赣南著名的钨锡多金属矿床,由漂塘本区、木梓园和大龙山三个矿段组成。多年以来,有关漂塘花岗岩成岩年龄,大多是利用邻近的西华山花岗岩的数据进行推断,而已有的年龄测试数据精度很难保证。对该矿床的成矿年龄则报道更少。本文利用单颗粒锆石U-Pb法对漂塘本区和木梓园的成矿花岗岩进行定年,获得了两条很好的U-Pb年龄谐和线,漂塘本区和木梓园成矿花岗岩的年龄分别为161.8±1Ma和 153.3±1. 9Ma。利用矿石中的白云母40Ar/39Ar同位素定年获得了漂塘本区成矿年龄为152±1.9Ma,利用矿石中的辉钼矿Re-Os同位素定年获得木梓园成矿年龄为151.1±8.5Ma。 以上年龄数据表明,矿床的成矿作用或与花岗岩侵位基本同时发生,或稍晚于花岗岩。赣南其他矿集区的一些代表性钨矿如淘锡坑、大吉山等的成矿与成岩也有这两种情况,可见这种成矿方式在赣南地区具有代表性。本文的年龄测定和近年来发表的一些年龄数据表明,赣南钨锡矿床属于华南燕山中期第一阶段陆壳重熔型花岗岩类大规模活动及其伴随的钨锡等金属大规模成矿作用的产物。  相似文献   

哀牢山-红河剪切带左行走滑作用起始时间约束   总被引：18，自引：1，他引：17  

曹淑云  刘俊来  Bernd Leiss  Axel Vollbrecht  邹运鑫  赵春强 《地质学报》2009,83(10):1388-1400

位于哀牢山-红河剪切带NW延伸方向上的点苍山变质杂岩体遭受强烈的左行走滑剪切变形、变质作用改造,岩石中保存了典型的高温矿物组合以及由它们构成的宏观和微观高温变形构造特征,其中糜棱岩中具有极其发育的长石矿物拉伸线理而形成典型的L与LS型构造岩是其一个明显的特征。本文对点苍山地区高温糜棱岩主要矿物开展了显微构造与矿物变形、变形机制及组构分析,并对于遭受高温糜棱岩化改造的一个花岗质岩体开展了SHRIMP锆石U-Pb定年分析。结果表明岩石中长石、角闪石、石英等主要矿物具有典型的达角闪岩相条件下的高温晶质塑性变形和动态生长特征,它们也为走滑剪切变形活动提供了充分的微观构造证据。对于点苍山高温糜棱岩化改造的眼球状或似斑状二长花岗岩的显微构造分析结果表明,这套花岗质岩石从走滑剪切前期岩浆的侵位之后经历了早期强烈的岩浆期后交代作用—亚岩浆流动—高温固态塑性剪切变形的递进演化过程。由此可见,岩浆的上升与就位受左行走滑剪切作用的制约,岩体又遭受了强烈剪切变形改造。同时对这套构造前期就位花岗质岩石中的锆石进行定年分析,获得33.88±0.32Ma的岩浆结晶年龄,为此,我们有充分的理由认为,在点苍山地区哀牢山-红河剪切带左行走滑剪切作用的起始时间至少应该为早渐新世30.88±0.32Ma。  相似文献