一次磁层亚暴期间磁场偶极化的尾向传播

利用TC1、Cluster和Polar结合极光和同步高度及地磁的观测,研究了2004年9月14日1730～1930 UT时间段的亚暴偶极化过程.此前行星际磁场持续南向几个小时.亚暴初发(Onset)开始于1823 UT.2 min之后,同步高度的LANL 02A在子夜附近观测到了明显的能量电子增强（Injection）事件,而TC1在1827UT左右在磁尾(-10,-2, 0)RE (GSE)观测到了磁场BX的突然下降,伴随着等离子体压强和温度的突然增加及磁场的强烈扰动.在(-16, 1, 3)RE (GSE) 的Cluster上相同的仪器观测到相同的现象,只是比TC1观测到的晚大约23 min,在1850 UT左右.虽然Polar在更靠近地球的较高纬度(-75, 35, -40)RE (GSE)附近,也在1855 UT左右观测到了这种磁场偶极化现象.以上的观测时序表明TC1、Cluster观测到的磁场偶极化比亚暴偶极化初始发生分别晚4 min和27 min.说明偶极化由近磁尾向中磁尾传播.详细计算表明偶极化源区的位置大约在X=-77RE～-86RE,而传播速度大约为70 km·s-1.在这个事件中亚暴的物理图像可能是中磁尾的近地重联产生的地向高速流到达近磁尾,为近磁尾的亚暴触发创造了条件;亚暴在近磁尾触发之后,磁场偶极化峰面向中磁尾传播.     

基于形态学的海洋锋形态特征提取

根据形态学梯度理论:不同尺寸的结构元素适合不同空间尺度的特征提取,结构元素尺寸的过大或者过小都会达不到最佳的特征边缘提取效果,从结构元素的尺寸δ与海洋锋横断面宽度γ和海流流幅的空间尺度λ的理论关系图推导中,提出δ,γ和λ的最佳定量关系:δ=γ/2,且δ<=λ/2,旨在对海洋锋形态特征进行提取。最后,以黑潮和墨西哥湾流为实验数据,进行海洋锋形态特征的自动提取,实验结果表明该定量关系的正确性和有效性。     

Controls on the mechanisms of fluid infiltration and front advection during regional metamorphism: a stable isotope and textural study of retrograde Dalradian rocks of the SW Scottish Highlands

Vein-controlled retrograde infiltration of H₂O-CO₂ fluids into Dalradian epidote amphibolite facies rocks of the SW Scottish Highlands under greenschist facies conditions resulted in alteration of calcite-rich marble bands to dolomite and spatially associated ¹⁸O enrichment of about 10%. on a scale of metres. Fluid inclusion data indicate that the retrograde fluid was an H₂O-salt mixture with a low CO₂ content, and that the temperature of the fluid was about 400d? C. Detailed petrographic and textural (backscattered electron imaging) studies at one garnet-grade locality show that advection of fluid into marbles proceeded by a calcite-calcite grain edge flow mechanism, while alteration of non-carbonate wall-rock is associated with veinlets and microcracks. Stable isotopic analysis of carbonates from marble bands provides evidence for advection of isotopic fronts through carbonate wall-rocks perpendicular to dolomite veins, and fluid fluxes in the range 2.4–28.6 m³/m² have been computed from measured advection distances. Coincidence of isotope and reaction fronts is considered to result from reaction-enhanced kinetics of isotope exchange at the reaction front. Front advection distances are related to the proportion of calcite to quartz in each marble band, with the largest advection distance occurring in nearly pure calcite matrix. This relationship indicates that fluid flow in carbonates is only possible along fluid-calcite-calcite grain edges. However, experimental constraints on dihedral angles in calcite-fluid systems require that pervasive infiltration occurred in response to calcite dissolution initiated at calcite-calcite grain junctions rather than to an open calcite pore geometry. The regional extent of the retrograde infiltration event has been documented from the high δ¹⁸O of dolomite-ankerite carbonates from veins and host-rocks over an area of least 50 × 50 km in the SW Scottish Highlands. Isotopically exotic ¹⁸O-rich retrograde fluids have moved rapidly upwards through the crust, inducing isotopic exchange and mineral reaction in wall-rocks only where lithology, pore geometry or mineral solubilities, pressure and temperature have been appropriate for pervasive infiltration to occur.     

Trace metal fronts in Scottish coastal waters

Dissolved cadmium and copper concentrations have been determined in 76 surface water samples in coastal and ocean waters around Scotland by anodic stripping voltammetry (ASV). A trace metal/salinity ‘front’ is observed to the west, north and north-east of Scotland separating high salinity ocean water (>35 × 10⁻³) with low concentrations of dissolved Cd and Cu from lower salinity (<35 × 10⁻³) coastal water containing higher concentrations of Cd and Cu. Mean Cd concentrations in ocean and coastal waters are 7 ng dm⁻³ (0·06 n ) and 11 ng dm⁻³ (0·10 n ) respectively; for Cu the respective levels are 60 ng dm⁻³ (0·95 n ) and 170 ng dm⁻³ (2·68 n ). The observed distribution is attributed principally to freshwater runoff and the advection of contaminated Irish Sea water into the study area.     

Spring phytoplankton bloom in the fronts of the East China Sea

Frontal areas between warm and saline waters of the Kuroshio currents and colder and diluted waters of the East China Sea (ECS) influenced by the Changjiang River were identified from the satellite thermal imagery and hydrological data obtained from the Coastal Ocean Process Experiment (COPEX) cruise during the period between March 1^st and 10^th, 1997. High chlorophyll concentrations appeared in the fronts of the East China Seas with the highest chlorophyll-a concentration in the southwestern area of Jeju Island (~2.9 mg/m³) and the eastern area of the Changjiang River Mouth (~2.8 mg/m³). Vertical structures of temperature, salinity and density were similar, showing the fronts between ECS and Kuroshio waters. The water column was well mixed in the shelf waters and was stratified around the fronts. It is inferred that the optimal condition for light utilization and nutrients induced both from the coastal and deep waters enhances the high phytoplankton productivity in the fronts of the ECS. In addition, the high chlorophyll-a in the fronts seems to have been associated with the water column stability as well.     

渤海的潮混合特征及潮汐锋现象

人们对黄海的潮汐锋现象已有一些报道和研究[1～4],但对渤海的潮汐锋现象却没有进行过认真的分析和讨论,迄今只有赵保仁[1]在讨论黄海的潮汐锋时,指出过渤海海峡的潮汐锋现象;而黄大吉等[5]在数值计算渤海的温度变化时也指出在渤海内部存在着潮汐锋现象,但却没有进行深入的分析和给出任何实测证据.本文试图根据方国洪和曹德明最近在渤海取得的潮汐潮流数值计算结果1),计算由Simpson等[6]提出的陆架海的潮混合层化参量,来讨论渤海的潮混合特征;并进一步利用实测水文资料和海面温度的卫星遥感图像来说明渤海潮汐锋的分布和变化特征.     

Interaction of a nonstationary ionization-shock front with an inhomogeneous interstellar medium

We consider the interaction of an ionization-shock front with isothermal waves in an H I region. Based on a two-front model in the linear approximation, we have detected a significant (approximately by an order of magnitude) periodic amplification of perturbations as they penetrate from the interstellar medium into an H II region. Numerical simulations have revealed that even when the shock-and ionization-front velocities differ and the relative density perturbations in the interstellar medium are ～10^?1, the variations in gas parameters near the ionization front are comparable to those observed at the boundaries of H II regions.     

Reply to Comment on ‘Marine GIS: Identification of mesoscale oceanic thermal fronts’

Geographic information service (GIService) has become popular in the last decade to develop applications for addressing global challenges. Performance is one of the most important criteria to help users select distributed online GIService for developing geospatial applications including natural hazards and emergency responses. However, performance accuracy is limited by the single-location-based evaluation mechanism while service performance is dynamic in space and time between end-users and services. We propose a spatiotemporal performance evaluation mechanism to improve the accuracy. Specially, a cloud and volunteer computing mechanism is proposed to collect performance information of globally distributed GIServices. A global spatiotemporal performance model is designed to integrate spatiotemporal dynamics for better performance evaluation for users from different regions at different times. This model is tested to support GIService selection in global spatial data infrastructures (SDIs). The experiment confirms that the proposed model provides more accurate evaluations for global users and better supports geospatial resource utilizations in SDIs than previous mechanisms. The methodology can be adopted to improve the services of other regional and global distributed operational systems.     

中国海洋产业的结构与布局研究展望

海洋产业结构与布局是海洋经济地理学研究的核心领域与主体内容,国内相关文献日益丰富,但海洋产业结构与布局研究尚未形成完整体系。梳理现有文献发现:国内研究存在起步晚、发展缓慢,高层次研究成果少且增长慢,以区域实证研究为主、理论创新研究较少等问题,现有研究集中在6方面:①海洋产业结构与布局的内涵、规律及其与陆域布局差异探索;②沿海省份或大城市海洋产业结构的现状与问题、结构优化与主导产业选择、产业结构绩效评价、竞争力与趋势研究;③区域海洋产业布局模式及优化政策支撑体系研究;④海洋资源与环境的产业承载力评价及海洋功能区划研究;⑤海洋产业集群,尤其是港航集群的初步探索;⑥国外海洋产业发展态势、统计标准与区域海洋产业合作探索。本文初步总结了国内对海洋产业结构与布局研究文献的增长规律,并立足于海洋产业结构与布局研究趋势,指出未来应加强海洋产业结构与布局的前沿领域及理论体系探索,并为我国海洋经济示范区建设提供科学指导。