基于单多普勒天气雷达产品的强对流天气预报预警方法   总被引：15，自引：10，他引：15  

廖玉芳  潘志祥  郭庆 《气象科学》2006,26(5):564-571

本文对发生在常德新一代天气雷达探测区内的强对流天气(雷雨大风、冰雹、龙卷)在雷达回波强度场及速度场上的表现特征进行了归类分析,既用实例证实了美国强对流天气在多普勒天气雷达产品上的表现特征同样适用于中国,又对其表现特征进行了完善。在此基础上建立了适用于当地的基于单多普勒天气雷达产品的强对流天气预报方法,并根据雷达实时体扫资料对强对流天气进行语音、文字自动报警以及对风暴移向、移速进行预报作了实用性的探讨。在多普勒天气雷达产品应用还处在探索、起步阶段的我国,该方法为制作强对流天气预报提供了较系统的预报思路。  相似文献   

3836C波段双线偏振多普勒雷达及其在一次降水过程中的应用研究   总被引：6，自引：5，他引：6       下载免费PDF全文

曹俊武刘黎平  陈晓辉陈刚 《应用气象学报》2006,17(2):192-200

该文介绍了2004年完成的在北京市气象局升级改造后的3836C波段双线偏振多普勒雷达的技术状况, 并通过对2004年11月9日北京地区一次大范围层状云降水观测资料的分析, 讨论了其探测资料的质量情况和对降水粒子的探测性能, 同时还根据零度层亮带内不同相态降水粒子的散射和空间取向等特征建立了一种利用双线偏振雷达观测资料识别零度层亮带的方法, 并利用该雷达的观测资料对识别结果做分析检验, 最后讨论了零度层亮带内各种降水粒子相态的变化规律。研究结果表明:除线性退极化比L_DR未作分析外, 3836雷达探测到的这次降雨过程的分析结果与国外双线偏振雷达的研究结果相似, 其对降水粒子相态结构的反映比较有效合理。建立的零度层亮带识别模式合理, 识别得到的结果能反映零度层亮带的特征。通过对零度层亮带内各偏振参数的变化特点分析, 从双偏振雷达测量参数的角度解释了“零度层亮带”现象的形成是由于在零度层以下的冰相粒子融化成大雨滴然后再裂碎为小雨滴, 从而造成在该层内水平偏振反射率因子Z_H、差分反射率因子Z_DR先增大后减小、水平/垂直偏振波零延迟相关系数ρ_hv (0) 先减小后增大的规律。  相似文献   

Bar-top hollows: A new element in the architecture of sandy braided rivers     

Jim Best  John Woodward  Phil Ashworth  Greg Sambrook Smith  Chris Simpson 《Sedimentary Geology》2006,190(1-4):241-255

Discrete hollows in the bar tops of the South Saskatchewan River are described that form a newly-recognized morphological element of sandy braided rivers. These bar-top hollows, which are up to 1.7 m deep and may extend for 10–30 m down and across flow, have a circular to ovoid planform and are shown, through use of ground penetrating radar, to be filled by a series of distinct, often angle-of-repose, foresets. The hollows form by both erosion and bar-top deposition and may be generated by bar-tail accretion, cross-bar channel cutoff and subsequent fill or lateral accretion at the bar-head. Bar-top hollows occur in the upper part of the bar depositional sequence and may thus prove useful indicators for braid bar reconstruction in ancient sediments, and should not be confused with channel scour.  相似文献   

灾害天气的识别和自动预警   总被引：4，自引：0，他引：4  

《广西气象》2006,27(4):20-23

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Spatial patterns in thunderstorm rainfall events and their coupling with watershed hydrological response   总被引：1，自引：0，他引：1  

Efrat Morin  David C. Goodrich  Robert A. Maddox  Xiaogang Gao  Hoshin V. Gupta  Soroosh Sorooshian 《Advances in water resources》2006

Weather radar systems provide detailed information on spatial rainfall patterns known to play a significant role in runoff generation processes. In the current study, we present an innovative approach to exploit spatial rainfall information of air mass thunderstorms and link it with a watershed hydrological model. Observed radar data are decomposed into sets of rain cells conceptualized as circular Gaussian elements and the associated rain cell parameters, namely, location, maximal intensity and decay factor, are input into a hydrological model. Rain cells were retrieved from radar data for several thunderstorms over southern Arizona. Spatial characteristics of the resulting rain fields were evaluated using data from a dense rain gauge network. For an extreme case study in a semi-arid watershed, rain cells were derived and fed as input into a hydrological model to compute runoff response. A major factor in this event was found to be a single intense rain cell (out of the five cells decomposed from the storm). The path of this cell near watershed tributaries and toward the outlet enhanced generation of high flow. Furthermore, sensitivity analysis to cell characteristics indicated that peak discharge could be a factor of two higher if the cell was initiated just a few kilometers aside.  相似文献   

Seasonal changes in ground‐penetrating radar signature observed at a polythermal glacier,Bylot Island,Canada     

T. D. L. Irvine‐Fynn  B. J. Moorman  J. L. M. Williams  F. S. A. Walter 《地球表面变化过程与地形》2006,31(7):892-909

In recent years, ground‐penetrating radar (GPR) has been increasingly used for characterization of subglacial and englacial environments at polythermal glaciers. The geophysical method is able to exploit the dielectric difference between water, air, sediment and ice, allowing delineation of subsurface hydrological, thermal and structural conditions. More recent GPR research has endeavoured to examine temporal change in glaciers, in particular the distribution of the cold ice zone at polythermal glaciers. However, the exact nature of temporal change that can be identified using GPR has not been fully examined. This research presents the results of three GPR surveys conducted over the course of a summer ablation season at a polythermal glacier in the Canadian Arctic. A total of approximately 30 km of GPR profiles were collected in 2002 repeatedly covering the lower 2 km of Stagnation Glacier, Bylot Island (72°58′ N 78°22′ W). Comparison between profiles indicated changes in the radar signature, including increased noise, appearance and disappearance of englacial reflections, and signal attenuation in the latter survey. Further, an area of chaotic returns in up‐glacier locations, which was interpreted to be a wet temperate ice zone, showed marked recession over the course of the ablation season. Combining all the temporal changes that were detected by GPR, results indicate that a polythermal glacier may exhibit strongly seasonal changes in hydrological and thermal characteristics throughout the ice body, including the drainage of 17 000 m³ of temporarily stored intra‐glacial meltwater. It is also proposed that the liquid water content in the temperate ice zone of polythermal glaciers can be described as a fraction of a specific retention capacity. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

双偏振天气雷达同时收发模式的一种改进方法   总被引：2，自引：0，他引：2  

梁海河  徐宝祥  刘黎平  葛润生 《大气科学》2006,30(4):635-644

目前,双偏振多普勒天气雷达的同时发射方式受到了普遍关注,作者针对该方式中偏振参量差分反射率存在较大误差的问题,研究了双发射通道相位差与差分反射率精度的关系,以及双通道发射功率差、接收机增益等对差分反射率的影响.在此基础上,给出了双偏振同时发射方式的一种改进方案,并讨论了该方案的优势和特点,设计了双偏振多普勒天气雷达同时发射方式下回波信号的处理框图.  相似文献   

VAD技术三种仰角策略反演风场的比较和应用   总被引：6，自引：1，他引：6  

李杰  顾松山  胡中兵  林科学 《南京气象学院学报》2006,29(2):220-227

对不同天气情况的资料分别采用单仰角VAD方法和多仰角VAD方法进行风场反演，比较了这两种算法的反演结果，提出了融合两种方法优点的自适应仰角取样方法，并进行反演比较，结果表明：单仰角和多仰角策略各有所长，采用自适应仰角取样策略结合两种方法优点，在某些场合下可以获得更有参考价值的VAD反演结果。  相似文献   

一次强对流过程的三维数值模拟   总被引：12，自引：5，他引：12  

于华英  顾松山  刘鹏  陈章法  黄小玉 《南京气象学院学报》2006,29(3):305-313

利用中国科学院大气物理研究所建立的完全弹性三维雹云数值模式（IAP-CSM3D），模拟了2004年4月23日横扫湘中湘南大部分地区的飑线强对流过程的流场、雷达回波和含水量等宏、微观物理量的分布及其演变。分析了冰雹形成的微物理过程，结果表明，冰雹粒子主要由冻滴（CNfh）和霰（CNgh）转化形成，其中冻滴的贡献比较大，冰雹主要是通过撞冻过冷水过程（CLch、CLrh）长大。将多普勒雷达实测资料同模拟的气流结构进行比较可见，雷达观测到散度随高度的变化与模式模拟的气流结构一致；模式输出的雷达回波强度及回波顶高与雷达观测事实相近。  相似文献   

2004年末黄淮暴雪的特点分析和数值模拟   总被引：8，自引：4，他引：8  

王东勇  刘勇  周昆 《气象》2006,32(1):30-35

利用多普勒天气雷达资料和中尺度数值模式模拟分析了2004年12月20日夜里起到22日黄淮出现的大范围暴雪天气过程。发现黄淮地区暴雪天气形成的原因和特点明显不同于梅雨锋暴雨。多普勒雷达探测资料可以很好地反映这场暴雪的特点:对流高度不高,平均高度3~4km左右,最高不超过8km。在强降雪时近地面925hPa附近伴有很强的超低空急流,东北偏东风,风速达12~14m·s-1。高低空垂直切变明显,有很强的斜压性。高分辨率的中尺度数值模式可以很好地模拟出这次过程的演变和特点。  相似文献