人工增雨作业中闪电定位仪与雷达的综合应用     

郑传新 《气象研究与应用》2003,24(1):50-51

综合利用闪电定位仪、T213及雷达回波资料对空中雷电的生成、演变进行实时跟踪定位,对判断对流云团的位置、准确及时地指挥人工增雨作业是一种有效的方法,可以提高作业的准确率和效果。  相似文献   

8·17雷暴、冰雹过程天气分析     

吴娟 《高原山地气象研究》2003,23(1)

雷暴、冰雹天气严重影响飞行安全.本文对2002年8月17日发生在成都地区的一次雷暴、局部冰雹的天气过程进行分析和总结,为今后的工作提供一些预报经验.  相似文献   

基于水土流失防治的云南金沙江流域土地利用生态安全格局初探   总被引：24，自引：1，他引：24  

杨子生  LIANG Luohui  王云鹏 《山地学报》2003,21(4):402-409

在水土流失严重的云南金沙江流域,建立基于水土流失防治的土地利用生态安全格局是保住人民生命线的根本举措。水土流失山区土地利用生态安全格局的构建应以允许土壤流失量(即T值)为基础,一方面确保各地块的土壤流失降至最低,以保持地块的生态安全和可持续利用,另一方面使区域性的水土流失问题从根本上得到有效控制,促进区域性土地利用生态系统的安全性和可持续性,并极大地减轻中下游的泥沙淤积和洪水灾害。另外,还应因地制宜地推行多样化土地利用、发展多功能农业,建立斑块镶嵌性与生态多样性的土地利用空间格局。总体而言,云南金沙江流域土地利用生态安全格局设计应突出三大重点:(1)以坡地梯田梯地化、建立梯田梯地农业与地埂经济为重点的耕地与园地利用与治理;(2)以乔灌草结合、多层配置为重点的林地和陡坡退耕地的利用与改造;(3)着力于地面绿化(而非"空中绿化")的荒山荒地开发利用。  相似文献   

The deficient T waves of tsunami earthquakes   总被引：4，自引：0，他引：4  

Emile A. Okal  Pierre-Jean Alasset  Olivier Hyvernaud  François Schindelé 《Geophysical Journal International》2003,152(2):416-432

  相似文献   

Metamorphic history of high-pressure granulites in Payer Land, Greenland Caledonides   总被引：1，自引：1，他引：1  

S. Elvevold  K. Thrane  J. A. Gilotti 《Journal of Metamorphic Geology》2003,21(1):49-63

A high‐P granulite facies gneiss complex occurs in north‐west Payer Land (74°28′?74°47′N) in the central part of the East Greenland Caledonian (Ordovician–Devonian) orogen. High‐P metamorphism of the Payer Land gneiss complex resulted in formation of the assemblages Grt + Cpx + Amp + Qtz + Ru ± Pl in mafic rocks, and Grt + Ol + Cpx + Opx + Spl in rare ultramafic pods. Associated metapelites experienced anatexis in the kyanite stability field. Peak metamorphic assemblages formed around 800–850 °C at pressures of c. 1.4–1.7 GPa, corresponding to crustal depths of c. 50 km. Mafic granulites contain abundant reaction textures, including the replacement of garnet by symplectites of Opx + Spl + Pl, indicating that the high‐P event was followed by decompression while the granulites remained at elevated temperatures. Charnockitic gneisses from Payer Land show evidence of late Archean (c. 2.8–2.4 Ga) crustal growth and subsequent Palaeoproterozoic (c. 1.85 Ga) metamorphism. The gneiss complex experienced intense reworking during the Caledonian continental collision. On the basis of Caledonian monazite ages recorded from the high‐P anatectic metapelites, the clockwise P–T evolution and formation of the high‐P granulite facies assemblages is related to Caledonian crustal thickening, which resulted in formation of eclogites approximately 300 km north of Payer Land. The Payer Land granulites comprise a metamorphic core complex, which is separated from the overlying low‐grade supracrustal rocks (the Neoproterozoic Eleonore Bay Supergroup) by a late Caledonian extensional fault zone, the Payer Land Detachment. The steep, nearly isothermal, unloading P–T path recorded by the granulites can be explained by erosional and tectonic unroofing along the Payer Land Detachment.  相似文献   

Metamorphic evolution of the coesite-bearing ultrahigh-pressure terrane in the North Qaidam, Northern Tibet, NW China   总被引：37，自引：0，他引：37  

S. G. Song  J. S. Yang  Z. Q. Xu  J. G. Liou  R. D. Shi 《Journal of Metamorphic Geology》2003,21(6):631-644

Widespread evidence for ultrahigh‐pressure (UHP) metamorphism is reported in the Dulan eclogite‐bearing terrane, the North Qaidam–Altun HP–UHP belt, northern Tibet. This includes: (1) coesite and associated UHP mineral inclusions in zircon separates from paragneiss and eclogite (identified by laser Raman spectroscopy); (2) inclusions of quartz pseudomorphs after coesite and polycrystalline K‐feldspar + quartz in eclogitic garnet and omphacite; and (3) densely oriented SiO₂ lamellae in omphacitic clinopyroxene. These lines of evidence demonstrate that the Dulan region is a UHP metamorphic terrane. In the North Dulan Belt (NDB), eclogites are characterized by the peak assemblage Grt + Omp + Rt + Phn + Coe (pseudomorph) and retrograde symplectites of Cpx + Ab and Hbl + Pl. The peak conditions of the NDB eclogites are P = 2.9–3.2 GPa, and T = 631–687 °C; the eclogite shows a near‐isothermal decompression P–T path suggesting a fast exhumation. In the South Dulan Belt (SDB), three metamorphic stages are recognized in eclogites: (1) a peak eclogite facies stage with the assemblage Grt + Omp + Ky + Rt + Phn at P = 2.9–3.3 GPa and T = 729–746 °C; (2) a high‐pressure granulite facies stage with Grt + Cpx (Jd < 30) + Pl (An24–29) + Scp at P = 1.9–2.0 GPa, T = 873–948 °C; and (3) an amphibolite facies stage with the assemblage Hbl + Pl + Ep/Czo at P = 0.7–0.9 GPa and T = 660–695 °C. The clockwise P–T path of the SDB eclogites is different from the near‐isothermal decompression P–T path from the NDB eclogites, which suggests that the SDB was exhumed to a stable crustal depth at a slower rate. In essence these two sub‐belts formed in different tectonic settings; they both subducted to mantle depths of around 100 km, but were exhumed to the Earth's surface separately along different paths. This UHP terrane plays an important role in understanding continental collision in north‐western China.  相似文献   

New constraints on metamorphism in the Rauer Group, Prydz Bay, east Antarctica   总被引：12，自引：0，他引：12  

D. E. Kelsey  R. W. White  R. Powell  C. J. L. Wilson  C. D. Quinn 《Journal of Metamorphic Geology》2003,21(8):739-759

Abstract Granulite facies metapelites of the Mather and Filla Paragneisses within the Rauer Group, east Antarctica, possess markedly different compositions. The metamorphic evolution of the two metapelite types has been interpreted as temporally distinct, with the Rauer Group preserving at least two distinct granulite facies tectonothermal episodes. Calculated P–T pseudosections and orthopyroxene Al content indicate the revised maximum‐preserved P–T conditions within the Mather Paragneiss to lie in the vicinity of 950–975 °C and 10–10.6 kbar, less extreme than previous estimates. The range of possible P–T paths for the Mather Paragneiss consistent with mineral textural relationships and pseudosections contoured for mineral proportion are significantly shallower (dP/dT) than previous estimates. A near‐isothermal decompression P–T path, and extreme peak metamorphic conditions, are not necessary to explain the development of preserved mineral reaction textures. The Filla Paragneiss contains pelitic assemblages less amenable to rigorous quantitative analysis. Nevertheless, possibilities for the shared or otherwise metamorphic evolution of the Mather and Filla Paragneisses may be postulated on the basis of calculated pseudosections in the context of existing geochronology for the Rauer Group and preserved microstructures. A shared evolution, most likely during Pan‐African granulite facies metamorphism, is plausible and consistent with mineral assemblage development, geochronology and microstructures. A revised interpretation of the Rauer Group's preserved metamorphic evolution may warrant the revision of existing tectonic models, applicable also to the remainder of Prydz Bay. More generally, the employed approach may incite a revision of peak P–T and P–T paths in other granulite facies terranes.  相似文献   

贵州乐康二叠／三叠系界线剖面的有机碳同位素异常及其意义   总被引：6，自引：0，他引：6  

吴明清 《矿物学报》1998,18(1):17-22

本文研究了贵州望谟乐康深水槽谷相二叠／三叠系界线剖面的有机碳同位素记录。研究结果表明,乐康剖面上二叠统δ13Corg值的变化幅度不大,越过第34层进入第35层以后,在WL－16号样品层位上,δ13Corg值突然从WL－15号样品的-25．419‰降低到-28．235‰,衰减幅度达到近3‰;其后δ13Corg值逐渐回升,并进入下三叠统。根据δ13Corg值的突然衰减正好发生在第34,35层的界线过渡层内这一事实,我们认为乐康剖面的P／T界线应划在第35层的WL－16号样品层位上。由于沉积有机物的碳同位素组成与海洋生物原始生产率（primaryproductivity）密切相关,因此,贵州乐康二叠／三叠系界线剖面的有机碳同位素变化曲线,不仅可以作为精确划分地层界线的一种新的有效手段,而且反映了海洋原始生产率的变化情况。  相似文献   

Book Reviews     

《The Professional geographer》1998,50(2):269-285

Golledge, Reginald G. and Stimson, Robert J., Spatial Behavior: A Geographic Perspective Gradus, Yehuda and Lipshitz, Gabriel, The Mosaic of Israeli Geography Hardwick, Susan Wiley and Holtgrieve, Donald G., Geography for Educators: Standards, Themes, and Concepts Imrie, Rob, Disability and the City: International Perspectives Howe, Jim; McMahon, Ed and Propst, Luther, Balancing Nature and Commerce in Gateway Communities Johnson, Troy R., The Occupation of Alcatraz Island: Indian Self-Determination and the Rise of Indian Activism Gordon, Terry G.; Kilpenen, Jon T. and Gritzner, Charles F., The Mountain West: Interpreting the Folk Landscape Keeling, David J., Contemporary Argentina: A Geographical Perspective Lamb, H. H., Climate, History and the Modern World Merriam-Webster's Geographical Dictionary Papadopoulos, Alex G., Urban Regimes and Strategies: Building Europe's Central Executive District in Brussels Parnwell, Michael J. G. and Bryant, Raymond L., Environmental Change in South-East Asia: People, Politics and Sustainable Development Peet, Richard and Watts, Michael, Liberation Ecologies: Environment, Development, Social Movements Raberg, Per, The Life Region: The Social and Cultural Ecology of Sustainable Development Simon, David, Transport and Development in the Third World Rees, Philip; Stillwell, John; Convey, Andrew and Kupiszewski, Marek (eds), Population Migration in the European Union Sousan, John; Shrestha, Bharat K. and Uprety, Laya P., The Social Dynamics of Deforestation: A Case Study from Nepal Smith, David A., Third World Cities in Global Perspective: The Political Economy of Uneven Urbanization  相似文献   

对T63L16所作月延伸预报准确率的评估   总被引：2，自引：0，他引：2  

张存杰  董安祥 《气象》1998,24(10):38-42

对国家气候中心１９９６年１－１２月和１９９７年１－８月用Ｔ６３Ｌ１６模式所做的５７次月延伸预报５００ｈＰａ高度场进行了检验评估,并对 系统性误差进行了分析和订正。同时对西北气候变化有较大影响的在循环流系统的环流特征量进行了检验,并给出了订正偏差。  相似文献