江苏省近45a极端气候的变化特征

利用江苏省35个测站1960—2004年45 a的逐日最高温度、最低温度、日降水量资料集,分析了近45 a江苏省极端高温、极端低温以及极端降水的基本变化特征。结果表明:(1)多年平均年极端高温的空间分布表现为西高东低,而极端低温则表现为自北向南的显著增加,极端降水的发生频次自南向北逐渐减少;(2)极端高温在江苏中部以及南部大部分地区有上升趋势,而西北地区则有弱的下降趋势;全省极端低温表现为显著的升高趋势;极端降水频次在南部地区有增加的趋势,北部减少趋势,中部则无变化趋势。(3)江苏极端高温、低温和极端降水的年际和年代际变化具有区域性差异,其中极端降水频次变化的区域性差异最为明显。     

热带山区高时空分辨率NDVI融合精度及其影响因素分析

高时空分辨率NDVI时序数据作为遥感应用中的重要数据源,对土地覆被动态变化监测具有重要意义,特别是在地表高程变化显著、气候条件复杂、景观异质性强烈的热带山区。虽然当前学者们提出了诸多时空数据融合模型,但针对这些模型在热带山区的NDVI数据融合精度及其影响因素分析尚不多见。对此,本文选取3类时空数据融合方法(权重函数法、概率统计法和多种混合法)中具有代表性的4个模型:STARFM(Spatial and Temporal Adaptive Reflectance Fusion Model)、RASTFM(Spatial and Temporal Adaptive Reflectance Fusion Model)、ESTARFM(Enhanced Spatial and Temporal Adaptive Reflectance Fusion Model)、BSFM(Bayesian Spatiotemporal Fusion Model)(STARFM、ESTARFM为权重函数法;BSFM为概率统计法;RASTFM为多种混合法),选择位于我国热带山区的纳板河流域作为研究区。对融合模型的...     

台风珍珠和鲇鱼北折路径对比分析

“珍珠”（0601,Chanchu）和“鲇鱼”（1013,Megi）都是发生北折路径的台风,通过分析发现导致台风珍珠和鲇鱼路径北折的天气形势变化有一些相同点：都发生在环境场的调整中,有西风槽影响华南的副热带高压,使之减弱东退、台风移速减慢,然后副热带高压加强并从台风南部向西南伸展、与赤道高压打通,其西侧的偏南气流与越赤道气流会合引导台风向北移动;同时有弱冷空气南侵。上述环境场的突然变化导致引导气流方向发生突然变化,是这两个台风西行北折的重要原因。引导气流分析还发现,秋台风鲇鱼最佳引导气流所在高度低于初夏台风珍珠。另外,不同的路径预报方法、不同的模式和超级集合预报提供了各种台风路径预报信息,在应用这些信息时要密切结合实况天气形势的变化,进行路径预报订正。     

河套地区一次寒潮天气的环流形势分析

利用常规气象观测资料和Micaps提供的相关资料,对2009年9月19—20日在河套地区发生的寒潮天气的环流形势及物理量进行分析。分析表明:在寒潮爆发前期,500hPa系统,蒙古西部的冷中心强度≥-32℃,且温度场滞后于高度场,为冷空气爆发南下提供了最基本条件;700hPa河套地区及上游≥16m.s-1的西北风急流基本形成,等温线与等高线交角≥45°且10个纬距内有4条及以上等温线的密集区;850hPa河套地区有≥16℃的暖中心,高空槽前后的西北风速≥18 m.s-1,温度线与高度线的夹角>45°;地面蒙古气旋的暖性性质为寒潮爆发的前期提供了有利的热力条件,地面冷锋后部冷高压轴线接近南北向,且冷高压中心强度≥1040hPa,3h变压≥3hPa。     

西藏加查拉岗村巨型古滑坡发育特征与形成机理研究

青藏高原地质构造活跃,内外动力作用强烈,加之气候异常变化,区内大型滑坡发育。以雅鲁藏布江断裂附近新发现的拉岗村古滑坡为研究对象,在现场调查、槽探揭露、地质测年和工程地质分析等基础上,对其发育特征及成因机制进行了分析研究。研究表明,(1)拉岗村滑坡属巨型岩质滑坡,体积达3.6×107 m3,最大水平滑动距离约3050m,滑坡后壁与堆积体前缘高差达965m,最大运动速率达78.1m/s,具明显高速远程特征;(2)受冷冻风化和冰体"楔劈"作用影响,滑坡后部岩体崩裂,全新世以来气候变化冰川逐渐消退,融雪降水入渗加剧劣化岩体结构,降低岩体强度;(3)根据14 C和10Be测年结果,拉岗村古滑坡形成于距今4140~9675a,沿雅鲁藏布江断裂发生的强震可能是该滑坡的直接诱因,岩体受到地震抛掷力作用,原有节理裂隙和新生破裂面发生张剪-拉裂破坏迅速贯通,首先沿断裂附近碎裂结构岩体发生破坏,上部岩体随之失稳并高速下滑。该研究可为认识青藏高原断裂带内大型古滑坡的形成机理提供借鉴。     

Efficiency of base isolation systems in structural seismic protection and energetic assessment

This paper concerns the seismic response of structures isolated at the base by means of High Damping Rubber Bearings (HDRB). The analysis is performed by using a stochastic approach, and a Gaussian zero mean filtered non‐stationary stochastic process is used in order to model the seismic acceleration acting at the base of the structure. More precisely, the generalized Kanai–Tajimi model is adopted to describe the non‐stationary amplitude and frequency characteristics of the seismic motion. The hysteretic differential Bouc–Wen model (BWM) is adopted in order to take into account the non‐linear constitutive behaviour both of the base isolation device and of the structure. Moreover, the stochastic linearization method in the time domain is adopted to estimate the statistical moments of the non‐linear system response in the state space. The non‐linear differential equation of the response covariance matrix is then solved by using an iterative procedure which updates the coefficients of the equivalent linear system at each step and searches for the solution of the response covariance matrix equation. After the system response variance is estimated, a sensitivity analysis is carried out. The final aim of the research is to assess the real capacity of base isolation devices in order to protect the structures from seismic actions, by avoiding a non‐linear response, with associated large plastic displacements and, therefore, by limiting related damage phenomena in structural and non‐structural elements. In order to attain this objective the stochastic response of a non‐linear n‐dof shear‐type base‐isolated building is analysed; the constitutive law both of the structure and of the base devices is described, as previously reported, by adopting the BWM and by using appropriate parameters for this model, able to suitably characterize an ordinary building and the base isolators considered in the study. The protection level offered to the structure by the base isolators is then assessed by evaluating the reduction both of the displacement response and the hysteretic dissipated energy. Copyright © 2003 John Wiley & Sons, Ltd.     

测井曲线旋回分析在碳酸盐岩层序地层研究中的应用*

在碳酸盐岩台地沉积层序的研究中,通过旋回计数和厚度测量,采用费希尔图解法解析高频米级旋回或副层序的叠置形式和空间结构,进而标定三级沉积层序的界面,是目前普遍采用的一个方法。但是,这一方法目前主要用于露头层序地层学研究,而在地下油气勘探区受到极大的限制。文中提出了一种新的计算方法,它可以根据测井资料求取任一地层段沉积旋回的个数和厚度。根据数值模拟,详细讨论了海平面变化周期和幅度与沉降速率、沉积速率的相关关系,提出高频沉积旋回的分布模式和叠加样式可以指示低频海平面变化的轨迹,这为划分三级沉积层序、标定层序界面提供了理论依据。最后,以川西北地区中三叠统雷口坡组为例,说明了应用自然伽马测井资料进行数据处理的流程和步骤,以及根据旋回厚度累积偏差曲线标定层序界面的位置、识别旋回谱系标志。     

高频地波雷达海杂波背景下的船只目标检测研究进展

针对海杂波对高频地波雷达目标检测的干扰问题,分目标处于海杂波谱区之内和之外两种情况综述了海杂波背景下的目标检测方法。对于海杂波内目标检测的难题,介绍了一种基于现场海态同步观测信息的检测新思路以及初步验证结果。对国内外相关研究进展的归纳总结和新思路的提出,为提出更加有效的海杂波干扰下的目标检测方法提供了重要的参考。     

Summer Monsoon and Annual Variability of Sea Surface Slope and Their Effects on Alongshore Current near Qingdao

Based on the monthly mean sea level data obtained from 3 years‘ (1999--2001) tide-gauge measurements, the annual variability of the sea level near Qingdao and Jiaozhou Bay is studied and discussed in this paper. Results show that the sea surface height at all the tide gauges becomes higher in summer than that in winter,with an obvious seasonal variability. Furthermore the sea surface height measured at a short distance outside the bay is lower than that in the bay, showing a sea surface slope downward from north to south. The reasons for the formation of the slope are explained as well. The dynamic action of the summer monsoon and the sea surface slope, and their effects on the monthly mean current are studied by means of dynamics principles. The importance of the summer monsoon and the pressure gradient generated by the sea surface slope, with their effects on the alongshore current, is pointed out and emphasized in this paper.     

武汉绕城公路东北段主要工程地质问题研究

为了给项目的设计和施工提供科学依据，对武汉绕城公路东北段软土、膨胀土、砂土地震液化、岩溶、深路堑、高填路基、筑路材料等潜在的地质灾害进行了详细评价，通过采用工程地质测绘及钻探、触探、物探、试验分析等多种勘探、测试手段，对沿线的各种工程地及其危害表现形式进行计算分析，预测施工过程及工程建成后可能出现的岩土工程问题，提出了相应的施工方法，对同类工程的建设具有指导意义。