2007 年南海夏季风季节内振荡的北传及影响因子

利用2007年全球降水气候计划GPCP(the Global Precipitation Climatology Project)卫星红外窗口导出的全球降水指数GPI(the Global Precipitation Index)的日降水资料及频率-波数分析方法,分析2007年南海夏季风季节内振荡(Intraseasonal Oscillation,ISO)的传播特征,并使用美国国家环境预报中心(NCEP)/美国大气研究中心(NCAR)再分析的逐日资料,探讨影响其传播的主要因子.结果表明,南海夏季风ISO有明显的北传趋势,并且明显比南传分量占优.影响南海夏季风ISO北传的主要因子是平均纬向风垂直切变和平均经向风对异常水汽的输送.之所以异常经向风对平均水汽的输送及海-气相可作用的影响在南海地区不重要,而在印度季风区有一定的贡献,是因为平均水汽和纬向风分布在两个地区的差异.     

南海夏季风的低频特征

利用１９７５－１９９３年（其中１９７８年缺）的向外长波辐射（ＯＬＲ）资料,分析了南海低频振荡的季节变化特征及其与南海夏季建立和活动的关系。结果表明：南海低频振荡在夏季期间比冬季风期间明显较强,南海夏季风一般在初夏第一个较强低频荡的负值位相开始建立;南海夏季风期间低频振荡的环流实体是ＩＴＣＺ的南北振荡和西太平洋高压西脊点的东西摆动,低频振荡与现海季风的活跃和中断（或减弱）密度相关;南海低频振荡与大气     

赤道平流层QBO与我国7月雨型的关联

根据1953～1991年赤道平流层纬向风资料分析,得出我国东部地区7月份主要雨带位置与赤道平流层30～50 hPa平均纬向风准两年振荡（以下简称赤道平流层QBO）有较好的关联。在西风位相条件下,我国7月主要雨带位置较偏北;在东风位相条件下,我国7月主要雨带位置易偏南。它们之间的关系主要是通过对对流层环流的影响相联系的。利用赤道平流层纬向风的变化规律并结合冬季北太平洋对流层环流特征,对我国7月主要雨带类型的预报,有一定实用意义。     

Nonlinear sloshing in a floating‐roofed oil storage tank under long‐period seismic ground motion

A hybrid analytical and FEM is proposed to investigate the nonlinear sloshing in a floating‐roofed oil storage tank under long‐period seismic ground motion. The tank is composed of a rigid cylindrical wall and a flat bottom, whereas the floating roof is treated as an elastic plate undergoing large deflection. The contained liquid is assumed to be inviscid and incompressible, and the flow is assumed to be irrotational. The method of analysis is based on representation of the liquid motion by superposing the analytical modes that satisfy the Laplace equation and the rigid wall and bottom boundary conditions. The FEM is then applied to solve the remaining kinematic and dynamic boundary conditions at the moving liquid surface coupled with the nonlinear equation of motion of the floating roof. This requires only the discretization of the liquid surface and the floating roof into finite elements, thus leading to a computationally efficient and accurate method compared with full numerical analysis. As numerical examples to illustrate the applicability of the proposed method, two oil storage tanks with single‐deck type floating roofs damaged during the 2003 Tokachioki earthquake are studied. It is shown that the nonlinear oscillation modes with the circumferential wave numbers 0, 2 and 3 caused by the finite liquid surface elevation as well as the membrane action due to large deflection of the deck produce excessively large stresses in the pontoon, which may cause the catastrophic failure of pontoon followed by the submergence of the roof. Copyright © 2012 John Wiley & Sons, Ltd.     

南半球降水对南极海冰涛动异常的响应

运用NCAR/CAM3全球大气环流模式,结合气候学诊断方法,分析了南极海冰涛动异常对南半球降水的影响,并对可能的作用机理进行了初步探讨。结果表明,南半球中纬度降水对海冰涛动异常的响应较为显著,且异常响应的空间分布与海冰涛动类似,分别在南美洲大陆以东大西洋和以西太平洋的广阔海域上存在两个正负值中心。 数值模拟结果显示,海冰涛动异常可以通过改变地表热通量,影响对流层中层大气,进而驱动费莱尔环流的上升支,加强或减弱费莱尔环流的强度,最终对南半球中纬度地区的降水分布产生影响。在阿蒙森/别林斯高晋海外围海冰异常偏少的海域,向上的热通量增加,局地加热会使得费莱尔环流的上升支异常偏强,费莱尔环流的经向输送增强,对应其在中低纬的下沉支也偏强,局地下沉气流异常偏强则会抑制降水的生成,导致降水异常偏少。在威德尔海外围海冰异常偏多的海域,经向环流和降水的响应几乎相反,但因受西南极半岛和南美洲陆面作用的影响,对应经度带费莱尔环流对海冰异常的响应较弱。     

利用易县形变综合观测资料检测日本地震所激发的地球自由振荡

基于形变数字化观测资料,利用功率谱密度估计方法,在没有对易县形变综合观测资料进行任何(固体潮及气压)改正的情况下,获取了2011年3月11日日本发生巨大地震激发的0S4～0S37基频球型自由振荡。并于PREM模型理论自由振荡的周期进行对比分析,得出实测周期与PREM预测振荡周期是相吻合,除0S10周期的相对误差为0.29%,其余周期误差均小于0.1%左右。所得的结论对进一步研究地球的内部结构和震源机制具有一定的意义。     

大万山岸式振荡水柱波力电站的输出功率

中国科学院广州能源研究所在位于南海的珠海市大万山岛建成一座岸式振荡水柱型示范波力电站。波力电站具有喇叭口前港，属多振荡型。广州能源研究所于１９８９年、１９９０年及１９９１年分别对其做了三次短期海上实测，其中包括对Ｗｅｌｓ透平发电机组的海上运行试验，证明该电站具有良好的实海况发电性能。电站的总能量俘获宽度比约为１０～４０％。本文对电站作了概述，并给出了电站实海况运行的结果。在该电站原有结构基础上，广州能源研究所已将其改建成一座２０ｋＷ的波力电站，并于１９９６年２月试发电成功。     

Experimental investigation of slip‐stick behaviour in granular materials

This paper presents the results of an experimental programme to study load oscillation in granular materials. Spherical glass beads were used in the investigation. Cylindrical specimens were compressed under axisymmetric triaxial loading condition at 25,100,250 and 400 kPa confining pressures. The test parameters included: (i) particle size; (ii) gradation (uniform versus non‐uniform specimens); (iii) confining pressure; (iv) loading rate; and (v) specimen density. In general, a slight post‐peak principal stress softening was observed as well as a continuous volume increase (dilation) even at relatively high strains. This appears to be caused by the uniform shape and smooth surface of the spherical particles. Load oscillations were observed in the very small, small, and well‐graded beads at each confining pressure. For the medium beads, the oscillations appeared at high confining pressure (250 and 400 kPa), and they did not appear in the large beads. The influences of the confining pressure, loading rate, particle size, gradation and specimen density on load oscillation are presented and discussed. Copyright © 2006 John Wiley & Sons, Ltd.     

A singular spectrum analysis on Holocene climatic oscillation from lake sedimentary record in Minqin Basin, China

The total organic carbon (TOC) content series from the lake sediment of Minqin Basin (100°57′–104°57′E, 37°48′–39°17′N) in northwestern China, which has a 10 000-year-long paleo-climatic proxy record, was used to analyze the Holocene climate changes in the local region. The proxy record was established in the Sanjiaocheng (SJC), Triangle Town in Chinese, Section (103°20′25″E, 39°00′38″N), which is located at the northwestern boundary of the present Asian summer monsoon in China, and is sensitive to global environmental and climate changes. Applying singular spectrum analysis (SSA) to the TOC series, principal climatic oscillations and periodical changes were studied. The results reveal 3 major patterns of climate change regulated by reconstructed components (RCs). The first pattern is natural long-term trend of climatic change in the local area (Minqin Basin), indicating a relatively wetter stage in early Holocene (starting at 9.5 kaBP), and a relatively dryer stage with a strong lake desiccation and a declined vegetation cover in mid-Holocene (during 7–6 kaBP). From 4.0 kaBP to the present, there has been a gradually decreasing trend in the third reconstructed component (RC3) showing that the local climate changed again into a dryer stage. The second pattern shows millennial-centennial scale oscillations containing cycles of 1 600 and 800 years that have been present throughout almost the entire Holocene period of the last 10 000 years. The third pattern is a millennial-centennial scale variation with a relatively smaller amplitude and unclear cycles showing a nonlinear interaction within the earth’s climate systems.     

吸积盘物理:稳定性和振动

研究了环绕致密天体的吸积盘的稳定性质和振动模式。特别关注了在热致和粘滞扰动作用下稳定的对流起支配作用的盘外流。还研究了相对论性吸积盘的振动模式。一些在盘内的捕获的 ,非衰减的模式也许可以用来解释X射线双星和活动星系核中所观测到的准周期振动。