Influence of the earth rotation on the interfacial wave solutions and wave-induced tangential stress in a two-layer fluid system

Interfacial waves and wave-induced tangential stress are studied for geostrophic small amplitude waves of two-layer .uid with a top free surface and a .at bottom. The solutions were deduced from the general form of linear .uid dynamic equations of two-layer .uid under the f -plane approximation, and wave-induced tangential stress were estimated based on the solutions obtained. As expected, the solutions derived from the present work include as special cases those obtained by Sun et al. (2004. Science in China, Ser. D, 47(12): 1147–1154) for geostrophic small amplitude surface wave solutions and wave-induced tangential stress if the density of the upper layer is much smaller than that of the lower layer. The results show that the interface and the surface will oscillate synchronously, and the in.uence of the earth’s rotation both on the surface wave solutions and the interfacial wave solutions should be considered.     

A Numerical Investigation of the Eyewall Evolution of a Tropical Cyclone

In this study, a high-resolution numerical simulation is conducted to investigate the eyewall evolution of Typhoon Imbudo (2003). The eyewall contraction, breakdown, and reformation are successfully simulated by the model. The eyewall accordantly shrinks throughout the whole troposphere prior to landfall, while it exhibits di erent variations after landfall in the lower and upper troposphere, respectively. It is found that the dry air advected into the storm inner core through a low-θe channel, the reduced surface latent heat transfer, and the increased in ows in the coastal region are associated with the eyewall contraction.Accompanied with the high-to-low wavenumber change in the vortex Rossby waves, the initial polygonal eyewall transforms to an elliptical one. Such a wavenumber change is likely associated with the change of interaction between the rainbands and the eyewall. The corresponding features of the time-averaged and vertical dynamic and thermodynamic structures are also examined during the storm passage. A tangential wind budget analysis indicates that a strong acceleration due to the contributions of both the eddy and the mean circulation is located in the lower layer in the eyewall during pre-landfall, and the mean circulation contribution to the change in the tendency of the azimuthally averaged tangential wind counteracts the eddy contribution.     

初始弹性模量的研究

切线模量是增量本构中很重要的一个力学参数,研究其规律性意义很大,本文将从初始弹性模量方面对其进行探讨研究,推导出初始切线模量与围压、超固结比、初始孔隙比之间的关系式,并对杭州某一区域的软土进行了三轴试验进行验证。     

FY-3C微波温度计资料的台风“威马逊”垂直结构研究

风云三号C星(FY-3C)携带的微波温度计(MWTS)辐射资料能够穿透非降水云,因此非常适合热带气旋的监测和结构研究。本文使用MWTS观测资料和逐步多元线性回归方法反演晴空和有云两种不同大气状况下的垂直温度廓线。晴空条件下,使用MWTS通道3—10的观测亮温进行大气温度廓线的反演,而有云情况下,仅使用通道5—10,并且两种状况下的逐步线性回归反演都通过1%的信度检验。研究结果表明在晴空状况下,大气各层温度反演的均方根误差都在1.4 K以下,足够精确到可以用于热带气旋上层暖心结构的反演。通过对台风"威马逊"周围温度廓线的反演研究,可以清楚地观察到200 hPa高度层上台风的暖心结构和沿着台风中心的温度梯度热结构,明显优于美国国家环境预报中心(NCEP)再分析资料得到的台风暖心结构。在大气温度廓线反演基础上,先由采用静力平衡计算各层大气台风"威马逊"周围的位势高度场,再由梯度风平衡计算台风周围的水平切向风,结果显示最大风速半径约80km,最大风速达51m/s,且由低层向高层逐步减弱。     

局部曲面正切曲率与流线曲率的水流路径算法

在局部特殊地形如细窄的沟渠等地带,水流方向可能是惟一的,即当前点的水应全部流入下游惟一的格网点,此时若采用多流向算法不仅会导致水流方向产生较大误差,而且可能影响区域汇水面积的精确计算。为解决此问题,本文提出了一种水流路径算法,该算法通过以各格网点为中心建立3×3窗口范围内的局部趋势面,利用该点在局部趋势面中的正切曲率和流线曲率选取合适的单流向或多流向算法来确定并计算该点的水流流向及流量分配比例。最后通过实例证明了该方法在水流累积量计算中的良好效果,并在一定程度上为格网DEM沟谷段和分水线段的提取奠定了基础。     

轴对称主动土压力问题的滑移线解

地基中竖向孔支护结构的设计需要以其所受主动土压力为依据,为此常需计算竖向孔开挖后孔壁主动土压力。含竖向圆孔地基是轴对称问题,基于平面应变假设的经典朗肯土压力理论或库仑土压力理论显然不适用,而现有求解轴对称条件下主动土压力方法多采用完全塑性假定或其他假定环向应力与大主应力之比（环向压应力系数?）为常数的方法,理论上不够严谨且误差较大。建立轴对称问题滑移线方程,采用使主动土压力为最大的目标的方法,采用迭代法求解环向压应力系数?,分析了?受土体参数和轴对称竖向孔几何参数影响规律,进而求解轴对称竖向孔孔壁主动土压力的精确值,理论上更为严谨,结果更为合理,并对比平面应变条件下的土压力结果,总结了轴对称条件下主动土压力的规律。     

Dynamic and Numerical Study of Waves in the Tibetan Plateau Vortex简

In terms of its dynamics, The Tibetan Plateau Vortex （TPV） is assumed to be a vortex in the botmdary layer forced by diabatic heating and friction. In order to analyze the basic characteristics of waves in the vortex, the governing equations for the vortex were established in column coordinates with the balance of gradient wind. Based on this, the type of mixed waves and their dispersion characteristics were deduced by solving the linear model. Two numerical simulations with triple-nested domains--one idealized large-eddy simulation and one of a TPV that took place on 14 August 2006---were also carried out. The aim of the simulations was to validate the mixed wave deduced from the governing equations. The high-resolution model output data were analyzed and the results showed that the tangential flow field of the TPV in the form of center heating was cyclonic and convergent in the lower levels and anticyclonic and divergent in the upper levels. The simulations also showed that the vorticity of the vortex is uneven and might have shear flow along the radial direction. The changing vorticity causes the formation and spreading of vortex Rossby （VR） waves, and divergence will cause changes to the n~otion of the excitation and evolution of inertial gravity （IG） waves. Therefore, the vortex may contain what we call mixed ：inertial gravity-vortex Rossby （IG-VR） waves. It is suggested that some strongly developed TPVs should be studied in the future, because of their effects on weather in downstream areas.     

中蒙边界中生代推覆-伸展递进转换及地壳尺度的切向剪切

中蒙边界一带发育中生代大型推覆和伸展构造。亚干伸展变质核杂岩从开始形成到最终(早白垩世)成型是一个长期递进发育过程,早期深层次透入性韧性伸展剪切主要发生于170～135Ma,有迹象显示在228～170Ma已经开始。这与中生代推覆事件在时代上重合,且运动指向相同,即上盘均向南东,显示推覆与伸展同时、同向的递进转换。提出地壳尺度切向剪切构造模式:在上地壳近水平简单剪切和水平挤压叠加构成一般剪切而形成推覆;而在中下地壳近水平简单剪切和上下挤压(重力作用)叠加构成一般剪切而发育同向伸展拆离剪切带(C'),随着上地壳的增厚和下地壳的减薄,该伸展剪切带向上扩展形成变质核杂岩。     

切向风速水平廓线对台风路径和强度的影响

用一个β平面的准地转模式和一个高分辨率的f平面准地转模式，实施了6组试验，研究了初始台风切向风速水平廓线对台风路径和强度的影响。结果表明：切向风速峰值区狭窄，最大风速半径较小的廓线，与偏西北方向的路径以及强度维持或增强相对应；峰值区宽平，最大风速半径较大的廓线，与北折转向的路径以及强度衰减相对应。