P-Vector Spirals and Determination of Absolute Velocities

A simple method to invert the absolute geostrophic velocity on potential-density surfaces is developed based on McDougall's (1988) conservation statements on potential-density surfaces and Chu's (1995) and McDougall's (1995) P-vector concept. This method has a capability to handle a system with diapycnal velocities and non-coincidence of potential-density and neutral surfaces. The validity of the inversion is the existence of the P-vector spirals instead of the existence of the velocity spirals (usually called the -spirals). We use a climatological T,S dataset for the Atlantic Ocean from the National Oceanographic Data Center (NODC) to show the benefit of using P-vector spirals in inverting the velocity field.     

Tides and Turbulent Mixing in the North of Taiwan Island

Microstructure and hydrological profiles were collected along two cross-shelf sections from the deep slope to the shallow water in the north of Taiwan Island in the summer of 2006. While the tidal currents on the shelf were dominated by the barotropic tide with the current ellipse stretched across the shelf, significant internal tides were observed on the slope. The depth-mean turbulent kinetic energy(TKE) dissipation rate on the shelf was 10~(-6)W kg-1, corresponding to a diapycnal diffusivity of 10~(-2)m~2s~(-1). The depth-mean TKE dissipation rate on the slope was 1 × 10~(-7)W kg-1, with diapycnal diffusivity of 3.4 × 10~(-4)m~2s~(-1). The shear instability associated with internal tides largely contributed to the TKE dissipation rate on the slope from the surface to 150 m, while the enhanced turbulence on the shelf was dominated by tidal or residual current dissipations caused by friction in the thick bottom boundary layer(BBL). In the BBL, the Ekman currents associated with the northeastward Taiwan Warm Current were identified, showing a near-bottom velocity spiral, which agreed well with the analytical bottom Ekman solution.     

SIMULATED FINE STRUCTURES OF SPIRAL RAINBANDS IN TYPHOON CHANCHU (2006)

In this study, fine structures of spiral rainbands in super Typhoon Chanchu (2006) are examined using an Advanced Research Weather Research and Forecast (WRF-ARW) model simulation with the finest grid size of 2 km. Results show that the simulation reproduces well Typhoon Chanchu’s track, intensity and basic structures. According to their locations and features, spiral rainbands are classified into principal, secondary, inner and distant rainbands, and their dynamic and thermodynamic features are investigated. The principal rainbands remain quasi-stationary with respect to Chanchu’s center and exhibit a wavenumber-1 feature with their outer edges separated by dry air. The secondary rainbands that occur on the radially inward side of the principal rainbands move around Chanchu''s center. The inner rainbands are closest to the center. They propagate both radially outward and azimuthally with time. The distant rainbands are located outside the inner-core region, and have stronger and continuous updrafts compared to the other rainbands. Distant rainbands are inward-sloping with height along the radial direction and have a cold pool in the low layers, whereas the principal and secondary rainbands lean radially outward with height. The inner rainbands do not show tilting with height along the radial direction. However, there are few vertical tilting cells along the azimuthal orientation among the four types of rainbands. The simulated radar reflectivity cores in all rainbands are collocated with the maxima of updrafts and equivalent potential temperatures in the low layer, indicating the important roles of energy supply in the boundary layer in determining the development of the rainband convection.     

长螺旋钻孔压灌桩嵌岩技术的改进与应用

普通长螺旋钻孔压灌桩适用于砂层、砾石层、硬土层及软岩层,不适用于硬度较高的岩石层。经改进钻头,加装加压系统、冷却系统后,长螺旋钻孔压灌桩可用于块石填土层、卵石层及较软—较硬基岩的钻进,拓宽了适用范围。工程实践证明,该嵌岩技术使用效果良好,具有推广价值。     

线路测量中确定方向转点的简便方法

介绍了在线路测量中,当中线方向受阻时确定方向转点的简便方法——中线支距法,并对其原理、计算、操作方法、精度评定进行了分析与实践。     

天体,地球,生物的一种自相似律——对数螺线

自相似是指自然和社会现象中,部分与整体之间,广泛存在着的放大对称（ｄｉｌａｔａ－ｔｉｏｎ ｓｙｍｍｅｔｒｙ）它们不仅在形态上,时空关系上,而且在信息,功能和能量等各个方面都表出的自相似特征,天体中,从众多的硕大的旋状星云,到坠落于地球上的微波的陨砂,陨尘,普遍存在着螺旋状的结构形态。地球上从变形矿物的包体至巨型的旋涡状构造,从岩石圈表层,直至外地核的深处,也都能发现螺旋形结构的存在,生物世界人植物     

超新星遗迹与银河系旋臂结构

从分子云演化的过程来讨论银河系中可能存在的超新星遗迹数目．对银河系分子云的观测已经得到了许多可靠的数据．如果这一研究结果在分子云方面能使理论值和观测值相匹配,那么由此导得的超新星事件结果也有一定的可靠性．结果表明,在内银河系中,可能存在的超新星遗迹约为（７７５±１２）τ５．旋臂结构并不会提高超新星的诞生率,它仅使超新星遗迹的分布有所变化,即在旋臂区域增加,而在臂间区域减少．