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中文摘要：
利用浙江省新一代多普勒雷达组网资料,选取在浙江东南沿海近乎同一地点登陆的3个台风进行研究。从登陆前6 h到登陆后7 h,对比分析3个台风在登陆前后的雷达回波和降水结构时空变化特征。利用单多普勒雷达四维变分风场反演技术,对温州多普勒雷达探测资料进行了风场反演。结合利用雷达回波强度资料,对3个台风登陆前后1 h在云岩、昌禅等地造成特大暴雨的中尺度对流系统的三维结构及其演变特征进行了详细分析。结果表明,台风强度与其螺旋云带中的对流单体密切相关。台风强度愈强,其中低层环状平均回波强度就愈强,对流活动也就愈旺盛,降水强度也愈大。台风登陆前,回波（雨带）从眼墙向外围传播。台风登陆后,随着台风外围回波（雨带）明显减弱,台风眼墙回波（雨带）则明显增强,台风眼区逐渐被强回波所取代,使台风登陆后眼墙的平均雨强比登陆前增大。台风登陆后1 h,由于低（高）层水平辐合（散）增强,强对流回波中倾斜的上升（下沉）气流明显增大,使对流运动更加活跃,造成登陆后1 h的降雨量显著增强。台风强度与登陆后1 h降雨量的增强幅度成正比。台风强度越强,垂直风切变就越大,垂直切变风速大值区与最大降雨区有较好的对应关系。台风登陆后1 h,垂直切变风速的明显增加对登陆台风螺旋雨带中的中小尺度对流的加强和维持起到了非常重要的作用。
英文摘要：
This study investigated temporal and spatial variations of the reflectivity and precipitation structure within 300 km radius of typhoon center by using the reflectivity data taken from the Doppler radars located in Zhejiang province.Three typhoons making landfall along the southeastern coast of Zhejiang province in China have been selected to examine the changes of the precipitation distribution from 6 h before landfall to 7 h after landfall.The three-dimensional wind fields are retrieved from the Wenzhou Doppler radar data using the 4D-Var wind retrieval technology.The 3D structure of the mesoscale convective system producing the most severe heavy rainfall at Yunyan and Changchan is analyzed with the single-Doppler radar retrieved wind and radar reflectivity observed by the Wenzhou Doppler radar.The results show that the stronger the typhoon intensity is,the bigger the reflectivity of the middle and low levels is,and the more severe the mesoscale convective system and the precipitation rate are.The axisymmetric component of typhoon echo（rainfall）,represented by the radial distribution of the azimuthal mean reflectivity,reveals that echo（rainfall） spreads outward from the typhoon eyewall before landfallling.The mean echo（rainfall rate） in the inner-core region increases abruptly,accompanied with the rapid contraction of the precipitation areas toward typhoon center when typhoons are approaching the coast.The mean rainfall rate in the typhoon eyewall will intensify after landfall.The single-Doppler radar retrieved wind fields indicate that,at 1 h after typhoon landfalling,with the enhanced convergent（divergent） wind fields in the low（upper） levels,the tilted upward movement in the mesoscale convective system is enhanced and the precipitation rate is increased obviously.The typhoon intensity is proportional to the increases of the precipitation rate.The stronger the typhoon intensity is,the bigger the vertical winds shear value is.The area of the maximum vertical wind shear value is correspondin
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