DISCONTINUOUS FLOW OF TURBID DENSITY CURRENTS II.INTERNAL HYDRAULIC JUMP     

Jiahua FAN Prof.  Sr.Engr. 《国际泥沙研究》2005,(2)

1 INTERNAL HYDRAULIC JUMPS AND LOCAL WATER ENTRAINMENT Traveling and stationary internal hydraulic jumps in two-layer flow can occur in the following situations (Fig. 1). When a stratified fluid flows over an obstacle created by a sudden blockage, the layer of increased depth within the heavier fluid will propagate upstream as a traveling hydraulic jump. When the heavier fluid overtops the obstacle it will flow along the downstream face of the obstacle as a supercritical flow…  相似文献   

青岛气温和降水的突变特征分析   总被引：3，自引：0，他引：3  

陈志梅  刘兆桐  张晓慧  于莉莉 《山东气象》2006,26(1):1-4

利用M-K法和信噪比法分析近百余年青岛市年平均气温和降水量的突变点,研究青岛市气候突变特征。结果表明:近百余年青岛市气温在不同时间尺度内反映出了不同的突变特点,年平均气温突变点在1988年,是一次增暖性突变,在20世纪30年代、50年代末及70年代初也发生了转折。青岛市的年降水量在1939-2002年间也发生了突变,突变点在1980年,80年代后进入一个相对少雨阶段。  相似文献   

Parameterization of Entrainment in a Sheared Convective Boundary Layer Using a First-order Jump Model   总被引：1，自引：0，他引：1  

Si-Wan Kim  Soon-Ung Park  David Pino  Jordi Vilà-Guerau de Arellano 《Boundary-Layer Meteorology》2006,120(3):455-475

Basic entrainment equations applicable to the sheared convective boundary layer (CBL) are derived by assuming an inversion layer with a finite depth, i.e., the first-order jump model. Large-eddy simulation data are used to determine the constants involved in the parameterizations of the entrainment equations. Based on the integrated turbulent kinetic energy budget from surface to the top of the CBL, the resulting entrainment heat flux normalized by surface heat flux is a function of the inversion layer depth, the velocity jumps across the inversion layer, the friction velocity, and the convection velocity. The developed first-order jump model is tested against large-eddy simulation data of two independent cases with different inversion strengths. In both cases, the model reproduces quite reasonably the evolution of the CBL height, virtual potential temperature, and velocity components in the mixed layer and in the inversion layer.The part of this work was done when the first author visited at NCAR.  相似文献   

500 hPa高度场的信号场突变与我国暴雨的发生规律性研究   总被引：3，自引：0，他引：3  

黄嘉佑  杨扬  周国良 《大气科学》2002,26(5):625-632

作者在500hPa高度信号场与我国暴雨发生的规律研究基础上,进一步寻找高度信号场能显示与暴雨的突变现象有关的异常信号出现的地区和描述指标.发现异常信号出现的地区大致可分为三个区域:我国境外西部、我国内陆地区和我国境外东部,可以反映区域信号场的主要特征,并由此形成信号场指标.研究表明,利用致洪暴雨发生日的前期信号场指标序列,其累积距平和逐日滑动平均值与我国暴雨出现有密切关系.对我国年度暴雨短期预报分析有一定的参考价值,可以作为传统天气动力诊断与预测的补充工具.  相似文献   

太阳活动百年尺度的跃变与气候跃变的相关分析   总被引：10，自引：5，他引：5  

冯松  汤懋苍 《高原气象》1998,17(3):266-270

讨论了２５００多年来太阳黑子周期长度（ＳＣＬ）的跃变特征,发现有在年尺度上ＳＣＬ基本在平均值附近变化,而其变率则存在明显的跃变现象,当ＳＣＬ的变率增大时,气候随之发生冷跃变,反之,则发生暖跃变。小冰期内,太阳活动弱且不稳定,与地球气候冷且不稳定具有同时性。  相似文献   

Instability and Diffusion in the Elliptic Restricted Three-body Problem     

Xinhao Liao  Donald G. Saari 《Celestial Mechanics and Dynamical Astronomy》1998,70(1):23-39

The importance of the stability characteristics of the planar elliptic restricted three-body problem is that they offer insight about the general dynamical mechanisms causing instability in celestial mechanics. To analyze these concerns, elliptic–elliptic and hyperbolic–elliptic resonance orbits (periodic solutions with lower period) are numerically discovered by use of Newton's differential correction method. We find indications of stability for the elliptic–elliptic resonance orbits because slightly perturbed orbits define a corresponding two-dimensional invariant manifold on the Poincaré surface-section. For the resonance orbit of the hyperbolic–elliptic type, we show numerically that its stable and unstable manifolds intersect transversally in phase-space to induce instability. Then, we find indications that there are orbits which jump from one resonance zone to the next before escaping to infinity. This phenomenon is related to the so-called Arnold diffusion. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

MULTI-SCALE ANALYSES OF SURFACE AIR TEMPERATURE VARIATIONS FOR THE NORTHERN HEMISPHERE AND CHINA DURING THE LAST ONE HUNDRED YEARS   总被引：1，自引：0，他引：1  

尤卫红  林振山 《Acta Meteorologica Sinica》1996,(2)

Using multi-resolution theory of wavelet analysis,this paper studies the multi-scale structureof surface air temperature variations for the Northern Hemisphere and China during the last onehundred years.The results show that the climatic variations for the Northern Hemisphere can bedescribed as 3 hierarchies corresponding to the larger-scale changes.They are the cold period be-fore 1919,the warm period from 1920 to 1978 and the warmer period after 1979.The larger-scalehierarchical changes obviously show qualities of climate jump.The years 1920 and 1979 are thejump points of climate change.The surface air temperature variations for China are not entirelyanalogous to the Northern Hemisphere,and the main contrasts are that China is in the cold periodafter 1955 and the jump point of warming is 1987.The surface air temperature variations for theNorthern Hemisphere and China during the last one hundred years obviously show the hierarchicalstructure of multi-scale changes and the qualities of climate jump.  相似文献   

甘肃“5.5”黑风暴跃变分析   总被引：1，自引：0，他引：1  

朱姝  周亚军 《气象》1996,22(10):8-12

用递归相似理论对１９９３年５月５日发生在甘肃省金昌市的一次特大黑风暴过程作了跃变分析，该理论中的跃变定义为身前数个状态不能完全表达当前状态的程度。  相似文献   

FX-3600P计算机程序在磁异常数据处理有关问题中的应用     

徐宝慈 《吉林大学学报(地球科学版)》1988,(2)

经反复摸索、实践,充分利用FX-3600P袖珍计算机的现有性能,开发扩充新功能,井结合巧妙的编制程序,给出了磁异常数据处理中几个常规方法(磁异常延拓、分量转换、频谱计算等)的循环程序。部分题目上实现了以小机器算大题目,为数据处理工作提供了一个快速、简便、经济的新途径。  相似文献   

周期 2 ,3,5及其气候突变点预测     

付遵涛  刘式达  陈炯  刘式适  梁爽 《地学前缘》2003,10(2):415-418

一个混沌气候时间序列含有各种各样的周期 ,其中周期 2 ,3和 5是最基本的周期 ,它们又是气候突变时间层次映射的主要角色。根据周期 2 ,3和 5的突变时间规律 ,它基本符合子波变换所导得的微分方程的解 ,由周期 1的突变时间可以预测周期 2 ,3和 5的突变时间。文中对北半球气温和中国气温的突变时间做了预测 ,预测效果较好。  相似文献