影响登陆台风降水量的主要因素分析

利用常规观测和自动站加密资料、卫星云图、雷达及NCEP再分析资料,诊断分析1521号台风“杜鹃”登陆福建减弱过程中造成宁波异常强降水原因,结果表明：本次宁波强降雨是由“杜鹃”减弱后的外围云系在加强西进的副高边缘通过对流发展引发的,伴有强雷电,具有低质心降水特点;中低层大范围、长时间持续的水汽能量输送给本次强降水提供了必要的水汽条件,水汽通量散度出现负值、极小值、变大与强降水的开始、增幅、结束有提前12 h的预示期;能量场的梯度大小和位置对台风暴雨的预报有较好的指示作用,强降水发生在能量场梯度大值区出现12 h之后;本次大暴雨过程发生在对流不稳定条件下,并伴有和暖湿气流相联系的湿位涡水平分量的发展,触发了垂直涡度的增长;中尺度辐合线的位置和强度对未来1 h降水预报有非常好的指示作用。

     

人工回灌过程中富里酸和Cu(Ⅱ)对多孔介质悬浮物堵塞的影响

地下水人工回灌是解决地下水超采问题的有效措施,悬浮颗粒物堵塞是影响回灌进行的技术瓶颈。目前多数研究聚焦在悬浮物堵塞方面,然而地表回灌水中重金属离子以及腐殖质对多孔介质物理堵塞的影响缺乏研究。本研究采用室内渗流砂柱试验研究富里酸、Cu(Ⅱ)以及两者共存对多孔介质悬浮物堵塞的影响,分别采用高岭土（SS组）、富里酸+高岭土（SS+FA组）、富里酸+Cu(Ⅱ)+高岭土（SS+FA+Cu组）配置模拟回灌用水。研究结果表明：（1）回灌结束时,SS组、SS+FA组、SS+FA+Cu组多孔介质整体相对渗透系数K’分别降至0.233,0.095,0.182。SS组和SS+FA+Cu组在中上层（0~7.50 cm）相对渗透系数K’均降至0.28以下,而在底层（7.50~10.50 cm）相对渗透系数K’仅降至0.45左右,说明2组多孔介质中上层重度堵塞（0相似文献   

高频GNSS形变波的震相识别：模拟实验与实例分析

高频GNSS震时形变波震相及识别是GNSS地震学的重要内容.在实时数据处理基础上,本文利用振动台的高频GNSS观测实验,并结合近期部分大震的高频GNSS形变波震相特征进行研究.数据处理结果表明,实时处理与事后处理的精度在同一量级,且与采样率无关.通过与同址观测强震仪和地震计记录的对比及特定震相的频谱分析,发现高频GNSS可完整记录P波、S波、Love波及Rayleigh波震相,影响震相记录的主要因素是GNSS定位精度与震级,而仅当震中距很小时,采样率将产生一定影响.研究结果得出：基于地震波传播规律,利用高频GNSS台阵记录的形变波空间分段特征,结合震相运动轨迹及其他地震波记录,可实现实时高频GNSS形变波的震相识别.     

An unsplit complex frequency-shifted perfectly matched layer for second-order acoustic wave equations

The perfectly matched layer(PML) boundary condition has been proven to be effective for attenuating reflections from model boundaries during wavefield simulation. As such, it has been widely used in time-domain finite-difference wavefield simulations. The conventional PML has poor performance for near grazing incident waves and low-frequency reflections. To overcome these limitations, a more complex frequency-shifted stretch(CSF) function is introduced, which is known as the CFSPML boundary condition and can be implemented in the time domain by a recursive convolution technique(CPML). When implementing the PML technique to second-order wave equations, all the existing methods involve adding auxiliary terms and rewriting the wave equations into new second-order partial differential equations that can be simulated by the finite-difference scheme, which may affect the efficiency of numerical simulation. In this paper, we propose a relatively simple and efficient approach to implement CPML for the second-order equation system, which solves the original wave equations numerically in the stretched coordinate. The spatial derivatives in the stretched coordinate are computed by adding a correction term to the regular derivatives. Once the first-order spatial derivatives are computed, we computed the second-order spatial derivatives in a similar way; therefore, we refer to the method as two-step CPML(TS-CPML). We apply the method to the second-order acoustic wave equation and a coupled second-order pseudo-acoustic TTI wave equation. Our simulations indicate that amplitudes of reflected waves are only about half of those computed with the traditional CPML method, suggesting that the proposed approach has computational advantages and therefore can be widely used for forwarding modeling and seismic imaging.     

全球风险和脆弱性评估方法及其尺度转换的局限性

近年来,国际上采用一系列指标,从全球的、区域的视角测度风险和脆弱性的工作不断增多.从全球尺度看,风险和脆弱性评估方法主要包括:UNDP的灾害风险指数、哥伦比亚大学的热点项目,以及哥伦比亚国家大学环境研究所开发的美洲项目;从区域尺度看,以GTZ和印度尼西亚社区合作伙伴共同开发的基于社区的风险指数最为典型.通过国际主要文献的综述,介绍了几种主要评估方法的目标、框架、测算指标和基本要求,分析了这些评估方法在应用中的局限性,指出了不同方法在空间尺度降次、升级转换过程中的不足和难点.     

无锡市现代农业评价体系构建

发展现代农业是促进我国"三农"问题解决的最有效途径之一,也是今后我国农业发展的根本方向。因而亟需建立一套科学的现代农业评价体系,以便对现代农业发展的水平进行评定并指导现代农业建设实践。该评价体系由农业生产、农村发展、农民生活3个方面构成,并以层次分析法赋予各指标权重。同时,以无锡市现代农业发展为实例对指标进行赋值。研究结果表明,无锡市现代农业正处于程度较高的发展期,但仍存在很大的发展空间。针对其发展过程中出现的问题,今后应采取提升农业规模化、机械化水平,加强信息化建设以及促进农民增收等应对措施。     

脉动与地震关系的初步探讨

为探索地震的前兆,对一些较大地震前地脉动特征的变化作了简要的分析,发现1975年2月4日的海城7.3级地震前数天,近震中的地震台上（△≈20公里）,脉动振幅异常减小;初步分析还表明,大震发生前,脉动方向以及脉动各分量相关系数的变化等现象也是值得引起注意的。     

A LAYERED NUMERICAL MODEL FOR SIMULATING THE GENERATION AND PROPAGATION OF INTERNAL TIDES OVER CONTINENTAL SLOPE I. MODEL DESIGN

A layered three-dimensional nonlinear numerical model was constructed to simulate the generation and propagation of internal tides over the continental slope. The simulation was split into external mode computation (EMC) and internal mode computation (IMC) to minimize the computational load. IMC was carried out once after EMC was implemented N times. As to EMC, a semi-implicit numerical scheme was applied in such a way that the pressure gradient terms and the velocity divergence terms were discretized semi-implicitly, but the other terms were discretized explicitly. Eulerian-Lagrangian explicit discretization was applied to the convective terms simultaneously. As a result, the stability of EMC did not depend on the wave celerity and time step was not limited by the CFL condition. More than that, use of the conjugate gradient accelerated Jacobi method further improved the computational efficiency of the model.     

NaCl胁迫下杂交稻农艺性状配合力及遗传力分析

采用4×4不完全双列杂交设计,在NaCl胁迫下对杂交水稻主要农艺性状进行了配合力和遗传力分析.结果表明,在调查的10个性状中有4个性状受NaCl胁迫影响差异较大,母本的千粒重及父本的粒厚一般配力差异显著,杂交组合的株高、粒厚、结实率及千粒重特殊配合力差异极显著,其中杂交组合N28S×中花14具有较高的配合力,受NaCl胁迫影响较低。株高及千粒重的广义遗传力和狭义遗传力均较高,可作为杂交水稻耐盐性的选育依据。     

A new carbon and oxygen balance model based on ecological service of urban vegetation

The application of human induced oxygen consumption and carbon emission theory in urban region was summed up and on this base a new model of urban carbon and oxygen balance (UCOB) was constructed by calculating the carbon and oxygen fluxes. The purpose was to highlight the role of vegetation in urban ecosystems and evaluate the effects of various human activities on urban annual oxygen consumption and carbon emission. Hopefully,the model would be helpful in theory to keep the regional balance of carbon and oxygen,and provide guidance and support for urban vegetation planning in the future. To test the UCOB model,the Jimei District of Xiamen City,Fujian Province,China,a very typical urban region,was selected as a case study. The results turn out that Jimei′s vegetation service in oxygen emission and carbon sequestration could not meet the demand of the urban population,and more than 31.49 times of vegetation area should be added to meet the whole oxygen consumption in Jimei while 9.60 times of vegetation area are needed to meet the carbon sequestration targets. The results show that the new UCOB model is of a great potential to be applied to quantitative planning of urban vegetation and regional eco-compensation mechanisms.