广州市冬夏季热岛的空间格局及其差异分析     

王芳  卓莉  冯艳芬 《热带地理》2007,27(3):198-202

利用2003年夏季和冬季两景Landsat ETM图像的热红外波段反演了广州市地表温度(LST)的空间变化,并对冬季和夏季热岛空间分布特征的差异及成因进行了分析。结果表明,广州市冬季和夏季热岛的空间分布具有明显的规律性,并且空间分布、强度差异很大;夏季热岛集中区主要是建筑物和道路等非渗透表面组成地域以及人口最密集区域,冬季热岛的分布主要与工业区和运输业的分布相伴。引起这种差异的原因主要是城市能耗布局、下垫面性质、冬夏季生物学和热学特征综合作用的结果。  相似文献   

Seismic anisotropy of the Slave craton, NW Canada, from joint interpretation of SKS and Rayleigh waves   总被引：2，自引：0，他引：2  

David Snyder  Marianne Bruneton 《Geophysical Journal International》2007,169(1):170-188

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Pre-eruptive and syn-eruptive conditions in the Black Butte, California dacite: Insight into crystallization kinetics in a silicic magma system     

Molly C. McCanta  Malcolm J. Rutherford  Julia E. Hammer 《Journal of Volcanology and Geothermal Research》2007,160(3-4):263-284

A series of experiments and petrographic analyses have been run to determine the pre-eruption phase equilibria and ascent dynamics of dacitic lavas composing Black Butte, a dome complex on the flank of Mount Shasta, California. Major and trace element analyses indicate that the Black Butte magma shared a common parent with contemporaneously erupted magmas at the Shasta summit. The Black Butte lava phenocryst phase assemblage (20 v.%) consists of amphibole, plagioclase (core An_77.5), and Fe–Ti oxides in a fine-grained (< 0.5 mm) groundmass of plagioclase, pyroxene, Fe–Ti oxides, amphibole, and cristobalite. The phenocryst assemblage and crystal compositions are reproduced experimentally between 890 °C and 910 °C, ≥ 300 MPa, X_H2O = 1, and oxygen fugacity = NNO + 1. This study has quantified the extent of three crystallization processes occurring in the Black Butte dacite that can be used to discern ascent processes. Magma ascent rate was quantified using the widths of amphibole breakdown rims in natural samples, using an experimental calibration of rim development in a similar magma at relevant conditions. The majority of rims are 34 ± 10 μm thick, suggesting a time-integrated magma ascent rate of 0.004–0.006 m/s among all four dome lobes. This is comparable to values for effusive samples from the 1980 Mount St. Helens eruption and slightly faster than those estimated at Montserrat. A gap between the compositions of plagioclase phenocryst cores and microlites suggests that while phenocryst growth was continuous throughout ascent, microlite formation did not occur until significantly into ascent. The duration of crystallization is estimated using the magma reservoir depth and ascent rate, as determined from phase equilibria and amphibole rim widths, respectively. Textural analysis of the natural plagioclase crystals yields maximum growth rates of plagioclase phenocryst rims and groundmass microlites of 8.7 × 10^− 8 and 2.5 × 10^− 8 mm/s, respectively. These rates are comparable to values determined from time-sequenced samples of dacite erupted effusively from Mount St. Helens during 1980 and indicate that syneruptive crystallization processes were important during the Black Butte eruptive cycle.  相似文献   

Determining magma flow in sills,dykes and laccoliths and their implications for sill emplacement mechanisms     

Ken Thomson 《Bulletin of Volcanology》2007,70(2):183-201

Three-dimensional seismic data from the Faeroe-Shetland Basin provides detailed information on the relationships between sills, dykes, laccoliths and contemporaneous volcanic activity. The data shows that sills are predominantly concave upwards, being complete or partial versions of radially or bilaterally symmetrical forms that possess flat inner saucers connected to a flat outer rim by a steeply inclined sheet. Such morphologies are only partially modified by pre-existing faults. Sills can be sourced from dykes or the steep climbing portions of deeper sills. Both sills and dykes can provide magma to overlying volcanic fissures and sills can be shown to feed shallow laccoliths. Magma flow patterns, as revealed by opacity rendering, suggest that sills propagate upwards and outwards away from the magma feeder. As an individual sill can consist of several leaves emplaced at different stratigraphic levels, and as a sill or dyke can provide magma to volcanic fissures, other sills and laccoliths, the data suggests that neutral buoyancy concepts may not provide a complete explanation for the mechanism and level of sill emplacement. Instead, the data suggests that the presence of lithological contrasts, particularly ductile horizons such as overpressured shales may permit sill formation at any level below the neutrally buoyant level. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Ken Thomson–deceased, April 2007  相似文献   

Numerical experiments on the generation of long ocean waves in coastal waters of the Buenos Aires province,Argentina     

Walter C. Dragani 《Continental Shelf Research》2007

A numerical model (two horizontal dimensions, vertically integrated) is used to investigate the generation of long ocean waves, ranging from 20 min to almost 2 h, at Buenos Aires continental shelf. The domain includes the Río de la Plata estuary and the continental shelf together and extends from 33.5° to 40.5°S latitude, and from 51° to 63°W longitude. Sea-level oscillations are modeled by forcing with passage of atmospheric cold fronts and atmospheric gravity waves. Both forcing mechanisms, which have been present during high activity lapses of long ocean waves, are mathematically implemented. After several numerical simulations, it is concluded that the pressure and wind fields associated to cold fronts do not generate long ocean waves in the area, though they do produce disturbances with periods longer than the tidal ones. On the other hand, it is so concluded that atmospheric gravity waves are an effective mechanism to force long ocean waves. Results obtained show that generation of long ocean waves is highly sensitive depending on the propagation direction and the phase speed of the atmospheric gravity waves. The long ocean wave event detected during the large-amplitude gravity-wave event of 13 October 1985 is successfully simulated. Finally, all our results suggest that atmospheric gravity waves are a highly effective mechanism forcing for the generation of long ocean waves in Buenos Aires coastal waters.  相似文献   

Unstructured,anisotropic mesh generation for the Northwestern European continental shelf,the continental slope and the neighbouring ocean     

Sébastien Legrand  Eric Deleersnijder  Eric Delhez  Vincent Legat 《Continental Shelf Research》2007

A new mesh refinement strategy for generating high quality unstructured meshes of the Northwestern European continental shelf, the continental slope and the neighbouring ocean is presented. Our objective is to demonstrate the ability of anisotropic unstructured meshes to adequately address the challenge of simulating the hydrodynamics occurring in these three regions within a unique mesh. The refinement criteria blend several hydrodynamic considerations as the tidal wave propagation on the continental shelf and the hydrostatic consistency condition in steep areas. Several meshes illustrate both the validity and the efficiency of the refinement strategy. The selection of the refinement parameters is discussed. Finally, an attempt is made to take into account tidal ellipses, providing another cause for anisotropy in the mesh.  相似文献   

Continuous,Direct Gas-Geochemical Monitoring in Hydrothermal Vents: Installation and Long-Term Operation on Nisyros Island (Greece)     

Manfred Teschner  Eckhard Faber  Jürgen Poggenburg  Georgios E. Vougioukalakis  Georgios Hatziyannis 《Pure and Applied Geophysics》2007,164(12):2549-2571

In this paper the installation and long-term operation of a system for continuous monitoring of fumarolic gases is described. Several physicochemical and gas-geochemical parameters such as the concentration of CO₂, H₂S and CO in the fumarolic emissions, as well as the temperatures of the hydrothermal steam and soil in close vicinity of the fumarole and steam pressure are measured in short-time intervals (typically 15 seconds). Data are logged on-site and in parallel transferred to a remote station by digital telemetry. Specially developed software enables the real-time observation of the local conditions in the crater and full bidirectional control of the monitoring system. Fluctuations in the monitored parameters are also reported. From the data presented it can be concluded that environmental conditions (direction and strength of wind, precipitation) will interact with some of the parameters monitored. These influences can only be revealed by continuously operated monitoring systems.  相似文献   

Simulation analysis on the regulation of overflow ecological water consumption in arid areas——A case study in the Canmrik ecological area of the mainstream zone of the Tarim River     

CHEN Xi  HUANG Yue  QIAN Jing  LIU HaiLong  FENG XianWei  LIU Ying  BAO AnMing  WANG WeiSheng 《中国科学D辑(英文版)》2007,50(Z1)

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南沙群岛岛礁地形地貌TM影像特征分析   总被引：3，自引：2，他引：3  

潘春梅  丁谦  曹文玉 《国土资源遥感》2002,(2):34-37,60

根据南沙海区的地形地貌特征，利用TM图像，对不同的珊瑚礁、珊瑚沙发育状况和岛礁的地质特征与生态特征进行了分析，研究了水下礁、滩的物质组份、发育程度及TM影像特征，提出了30m以浅岛礁分类方法，查清了南沙海域岛、礁、滩、沙的形态和分布，细化并完善了南沙群岛岛礁分类。  相似文献   

从上海市热岛演变看城市绿化的重要意义   总被引：15，自引：6，他引：15  

丁金才  周红妹  叶其欣 《气象》2002,28(2):22-24

近40年来，上海城市热岛面积扩大了7－8倍，强度增强了一倍，导致了高温灾害的增加。上海热岛的迅速扩张和增强始于20世纪80年代，与上海城市的建设有明显的对应关系。如何合理规划城市建设，减缓热岛效应影响，以保证上海城市的健康和可持续发展，已成为一个迫切需要解决的问题。近几年来显示出的上海中心城区热岛强度减弱趋势表明，城市绿化建设对减缓城市热岛效应具有重要意义。  相似文献