大气中的波流相互作用研究进展   总被引：2，自引：1，他引：1  

何金海  胡亮  杨松 《热带气象学报》2008,24(1):1-10

简要回顾了近年来关于波动同纬向平均流相互作用的研究进展,重点讨论了E-P通量和波作用守恒理论的研究进展,同时,还介绍了波流作用稳定性问题的理论研究动态.  相似文献   

基于小波变换的大安地区年降水量变化特征   总被引：3，自引：0，他引：3  

卢文喜  陈社明  王晨子  刘磊  贾洪玮  吕德全 《吉林大学学报(地球科学版)》2010,40(1):121-127

基于小波分析的方法,对吉林省大安地区1959—2007年的年降水量序列的变化特征进行了分析。经分析表明,大安地区年降水量在其计算时域内各时间尺度分布不均匀,具有明显的局部化特征;其中4～6 a尺度主要发生在1959—1969年和1984年之后,10～12 a尺度主要发生在1965—1999年,20～25a尺度在整个计算时域内均有发生。不同时间尺度下,降水量偏多、偏少交替变化也不相同。此外,分析结果显示该地区年降水量具有4 a、10 a和21 a左右的主周期,其中4 a周期为第一主周期。  相似文献   

毫秒(ms)脉冲星计时观     

倪广仁  柯熙政  杨廷高  李孝辉 《天文研究与技术》2003,(3):47-55

简介了国际上脉冲星计时研究的成果。主要评述中国在脉冲星计时研究方面的进展和观点:某些ms脉冲星可以用作天然的高精度的频率标准源。ms脉冲星时(PTens)的长期稳定度随观测时间的加长而提高,同时,它具有寿命长,稳定、可靠、不需要维修等优点。尽早适时地建立专门用于测量ms脉冲星时(PTens)的脉冲星钟系统网络是有益的。我国正在建设用于脉冲星脉冲到达时间(TOA)测量的50m射电望远镜,和正在研究(FAST)500m射电望远镜。论述了脉冲星时间尺度的建立是可行的,脉冲星时和原子时可以"交叉比对,相互检验,并肩发展"。研究表明综合脉冲星时的长期稳定度明显优于原子时。阐述了把小波分析方法应用于时间尺度,研究结果比较传统方法有明显的优势。对国际间的合作提出建议。并展望了中国的脉冲星计时规划。  相似文献   

Aircraft Observations of the Development of Thermal Internal Boundary Layers and Scaling of the Convective Boundary Layer Over Non-Homogeneous Land Surfaces   总被引：1，自引：0，他引：1  

Michail A. Strunin  Tetsuya Hiyama  Jun Asanuma  Tetsuo Ohata 《Boundary-Layer Meteorology》2004,111(3):491-522

This study investigates the convective boundary layer (CBL) that develops over anon-homogeneous surface under different thermal and dynamic conditions. Analysesare based on data obtained from a Russian research aircraft equipped with turbulentsensors during the GAME-Siberia experiment over Yakutsk in Siberia, from April to June 2000.Mesoscale thermal internal boundary layers (MTIBLs) that radically modified CBLdevelopment were observed under unstable atmospheric conditions. It was found thatMTIBLs strongly influenced the vertical and horizontal structures of virtual potentialtemperature, specific humidity and, most notably, the vertical sensible and latent heatfluxes. MTIBLs in the vicinity of the Lena River lowlands were confirmed by clouddistributions in satellite pictures.MTIBLs spread through the entire CBL and radically modify its structure if the CBL isunstable, and strong thermal features on the underlying surface have horizontal scalesexceeding 10 km. MTIBL detection is facilitated through the use of special parameterslinking shear stress and convective motion.The turbulent structure of the CBL with and without MTIBLs was scaled usingthe mosaic or flux aggregate approach. A non-dimensional parameterL_Rau/L_hetero (where L_Rau is Raupach's length and L_hetero is the horizontal scale of the surface heterogeneity)estimates the application limit of similarity and local similarity scaling models forthe mosaic parts over the surface. Normalized vertical profiles of wind speed, airtemperature, turbulent sensible and latent heat fluxes for the mosaic parts withL_RauL_hetero < 1 could be estimated by typical scalingcurves for the homogeneous CBL. Traditional similarity scaling models for the CBLcould not be applied for the mosaic parts with L_Rau/L_hetero > 1.For some horizontally non-homogeneous CBLs, horizontal sensible heat fluxes werecomparable with the vertical fluxes. The largest horizontal sensible heat fluxes occurred at the top of the surface layer and below the top of the CBL.Formerly affiliated to the Frontier Observational Research System for Global ChangeFormerly affiliated to the Frontier Observational Research System for Global Change  相似文献   

Empirical Global Relations Converting M S and m b to Moment Magnitude   总被引：1，自引：0，他引：1  

E. M. Scordilis 《Journal of Seismology》2006,10(2):225-236

The existence of several magnitude scales used by seismological centers all over the world and the compilation of earthquake catalogs by many authors have rendered globally valid relations connecting magnitude scales a necessity. This would allow the creation of a homogeneous global earthquake catalog, a useful tool for earthquake research. Of special interest is the definition of global relations converting different magnitude scales to the most reliable and useful scale of magnitude, the moment magnitude, M _W. In order to accomplish this, a very large sample of data from international seismological sources (ISC, NEIC, HRVD, etc.) has been collected and processed. The magnitude scales tested against M _W are the surface wave magnitude, M _S, the body wave magnitude, m _b, and the local magnitude, M _L. The moment magnitudes adopted have been taken from the CMT solutions of HRVD and USGS. The data set used in this study contains 20,407 earthquakes, which occurred all over the world during the time period 1.1.1976–31.5.2003, for which moment magnitudes are available. It is shown that well-defined relations hold between M _W and m _b and M _S and that these relations can be reliably used for compiling homogeneous, with respect to magnitude, earthquake catalogs.  相似文献   

一种分离暴雨过程天气尺度和次天气尺度特征的方法   总被引：2，自引：0，他引：2       下载免费PDF全文

魏凤英  朱福康 《大气科学》2003,27(2):191-202

作者提出利用奇异谱主分量重建技术进行气象变量场尺度分离的新构想,并设计出尺度分离的具体实施方法.使用此方法对1998年7月下旬长江流域强暴雨过程的卫星观测亮温(TBB)场进行了试验性尺度分离.结果表明,该分离技术可以将这次暴雨过程天气尺度和次天气尺度系统的基本结构清晰地分离出来.在天气尺度场上,长江流域呈现出明显的切变线上连续性对流云系的特征.在次天气尺度场上,可以清楚地显现出偶极子系统的演变特征,其活动与暴雨过程有很好的对应.  相似文献   

非静力模式中几种垂直网格计算特性的对比研究   总被引：8，自引：0，他引：8  

Liu Yudi  Ji Zhongzhen  Wang Bin 《大气科学进展》2002,19(3):528-543

从非静力滞弹性方程组出发，将惯性重力波的水平波长分几百公里、几十公里和几公里三种情况，从频率、群速和各速的垂直尺度范围等方面对现有的几种垂直网格进行比较讨论。结果表明：在非静力模式中，CP网格和LZ网格适合于各种不同水平尺度惯性重力波的模拟；L网格和LY网格适合于水平尺度为几十公里以上的惯性重力波的模拟；LTS网格和CPTS网格比较适合于水平尺度的几十公里以下的惯性重力波的模拟。  相似文献   

不同时空尺度的泥石流预报技术体系     

韦方强  徐晶  江玉红  张继 《山地学报》2007,25(5):616-621

降水诱发的泥石流是我国主要的泥石流灾害类型。降水是该类泥石流灾害预报的关键动态因子,不同的降水监测和预报技术与方法决定了泥石流预报的不同时空尺度。分析了不同降水监测和预报技术的时空尺度和时空分辨率,并以此为基础,结合下垫面条件分析,建立了不同时空尺度的泥石流预报体系框架:大中区域泥石流预报(数值天气预报)─中小区域泥石流预报(多普勒天气雷达)─单沟泥石流预报(多普勒天气雷达和地面降水遥测)。具体的技术体系包括下垫面条件分析、降水监测和预报方法以及预报结果的表述与发布。  相似文献   

德兴金山金矿田不同尺度构造特征及其与成矿作用的关系   总被引：5，自引：1，他引：5       下载免费PDF全文

李晓峰  王春增  易先奎  冯佐海  王义天 《地质论评》2007,53(6):774-782

德兴市金山金矿田是与赣东北深大断裂带内次一级剪切带有关的中温热液矿床。其矿石类型主要由与断裂充填有关的小尺度石英脉组成，这些石英脉主要呈纹层状。不同尺度的构造研究表明，金山金矿是同构造的产物，递进变形作用与成矿作用密切相关，在成矿过程中，普遍发育压溶作用，导致早期的石英颗粒发生溶解以及形成黄铁矿压力影。金山金矿蚀变硫化物以黄铁矿为主，说明成矿流体中硫主要以H2S和HS-形式存在。断层阀机制引起压力波动，进而导致成矿流体的相分离和水—岩反应，是金山金矿的主要成矿机制。  相似文献   

Monitoring and predicting channel change in a free‐evolving,small Alpine river: Ridanna Creek (North East Italy)     

Rossella Luchi  Walter Bertoldi  Guido Zolezzi  Marco Tubino 《地球表面变化过程与地形》2007,32(14):2104-2119

The recent (25 years) morphodynamics of a proglacial reach of the Ridanna Creek, North‐East Italy, evolving in the absence of human constraints, has been investigated by means of an intensive field activity and of the analysis of aerial photographs. The study reach mostly displays a braided morphology, with sharp downstream variations of valley gradient, sediment size and formative conditions within the main channel. These discontinuities are associated with different processes of channel adjustment at different timescales, which have been quantified by coupling hydrological with morphological information. Several processes of channel change and variations in braiding intensity have been documented along the whole reach and highlight how a regular, weakly meandering main channel may significantly affect the morphodynamics of the braided network. A first attempt to predict the morphological instability of this main channel at the observed spatial scales through existing linear theories of curved river channels shows a good agreement with field observations. Finally, the complete hydro‐morphodynamical characterization of such an undisturbed alpine river reach can provide a relevant contribution to the definition of reference conditions for Alpine rivers required by the EU Water Framework Directive. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献