【作者】 刘敏；

【导师】 汤达章；

【作者基本信息】 南京信息工程大学 ， 气象学， 2006， 硕士

【摘要】 本文主要从多普勒雷达资料入手,对一些大尺度复合风场的径向速度模拟图像均找到相似的实际回波图例与之相对应;特别对具有特殊结构的东北冷涡进行分析,探讨单部多普勒雷达探测大尺度圆周运动的一些特征。 在实际业务观测中,多普勒天气雷达探测大尺度的旋转运动时,有明显的径向速度分布特征。如在探测东北冷涡的过程中,发现东北冷涡的多普勒正、负速度中心以及零速度线的分布特征与探测中小尺度气旋及台风的特征相似。之所以出现这种多普勒径向速度特征,与东北冷涡气旋环流的分布以及多普勒雷达所探测的径向速度是分不开的:即在同一等高面或等压面上,冷涡气旋中心处的风速较小或为静风;随着气旋半径r的增大,环流圈上的风速也随之增加;当r增大到一定距离时,出现一风速大值区;而后,随着r的增大风速呈减小趋势。冷涡的这种风速变化结构,用蓝金模式来描述,是很好的近似;多普勒雷达探测东北冷涡时,某一高度上的风速大值区内的环流圈进入雷达有效探测范围内并与雷达的扫描半径相切,在多普勒雷达速度图上表现为两个正、负速度中心呈方位对称分布,我们定义径向速度值最大的环流圈为最大速度圆,其半径为R,此时r=R。定义最大速度圆上的半径R为气旋核半径,其速度为气旋的旋转速度V_max。由于东北冷涡尺度较大,多普勒雷达只能探测到该系统的一部分。本文采用蓝金模式进行数值模拟,模拟结果证实,其模拟的多普勒速度分布特征与多普勒雷达实际探测冷涡的特征极其相似。 根据模拟结果及实际多普勒速度图像特征,确定东北冷涡中心位置。我们在实际的冷涡速度图中,读取两个速度中心的位置,分别作两条和这两速度中心所在径线的垂线,两条垂线的交点即为某一高度上的冷涡中心,或者正（负）中心的位置所在径向的垂线和零速度线呈直线分布的延长线的交点,也可近似为冷涡中心。冷涡中心确定后,冷涡的移动路径也随之而定,进而冷涡移动路径与降水的对应关系也确定。 对东北冷涡系统连续观测,得到冷涡的移动路径、发展维持、增强减弱以及旋转速度、核半径、方位角变化等信息,对预报有一定的补充、指导意义; 应用多普勒天气雷达探测东北冷涡,对三次冷涡过程的速度特征进行分析,既有一定的创新,更有较高的应用价值,同时也为今后的研究工作奠定了基础。更多还原

【Abstract】 In this paper, the characteristic analysis on the special structure of north-eastern cold vortex based on Doppler radar data and some research about single Doppler radar detecting large scale cyclonic circulation have been finished. Meanwhile, some images of Doppler radial velocity have been provided for some wind profile images.The obvious character of Doppler radial velocity was found when Doppler radar detected the large-scale rotation circulation—northeastern cold vortex. The distributions of the max and min radial velocity centers as well as the zero line on Doppler radar image are very similar to the medium or small-scale cyclone and typhoon. These characters of Doppler radial velocity are associated with the cyclonic circulation distribution and the Doppler velocity. When at the same level, the wind speed of cyclonic circulation is proportion to the distance of "r"from the center to the cyclonic circle till the strongest wind region. Then the wind speed will be inverse proportion to the distance of "r"from the strongest wind region away and the wind speed of the cyclonic center is small or zero. The distribution of cyclonic circle velocity meets a part of rankine model. One of cyclonic circles (the cyclonic circles in the strongest wind region) come into the radar valid area and it is tangent with the scan radius of radar .the Doppler velocity will emerge plus and minus velocity centers. We define this cyclonic circle as the max velocity circle;the radius is "R", and the velocity as rotation speed. The Rankine model has been used in numeric model in order to prove that character. A series of numeric model results have identified that Doppler radar can detect parts of northeasterncold vortex. The northeastern cold vortex is so large that Doppler radar can only detect a part of it.Doppler radar and the numeric model image determined the center position of northeastern cold vortex. The two centers of velocity can be read from the velocity image. The intersection that two perpendicular of two radius crossing the two centers of velocity is the center of the north eastern cold vortex, or the intersection crossing perpendicular of one radius and the extended zero line, then the moving pathway and the relation between the moving pathway and precipitation will be determined.The spatial and temporal character of cold and warm advection distribution and the divergence and convergence was analyzed according to Doppler radar data, then the vary phase of the northeastern cold vortex will be identified.The information of north-eastern cold vortex including the moving pathway, the Variety of intensity, the velocity of rotation, the radius and the azimuth can be gotten by detecting this weather system continually and this research will be useful for the service and research in the future. Meanwhile, The method that uses Doppler radar data to analyze three processes of cold vortex is innovative and valuable for forecasters.更多还原