摘要
超强台风"韦帕"(Wipha)是2007年登陆中国大陆最强的台风,在浙江省造成了特大暴雨。利用宁波和舟山双多普勒天气雷达同步观测资料,对"韦帕"的两条螺旋雨带进行了双雷达三维风场反演;并综合利用组网雷达拼图数据等资料,对螺旋雨带的三维精细结构进行了分析。研究表明:(1)两条螺旋雨带的三维结构有很多相似之处。螺旋雨带内部低层有多个强回波区,水平速度大值区主要分布在强回波带上;强回波带的低层有较强的上升气流,最强上升气流超过4 m/s。在螺旋雨带中存在多个辐合辐散对、上升下沉气流对,这对于螺旋雨带的维持和进一步发展具有重要作用。在沿着台风中心的垂直剖面内,螺旋雨带内部的强回波区向雨带外侧倾斜。雨带外侧2 km高度以下的低层有较强的内流,最大值为5 m/s;雨带内侧有较强的外流,2 km高度以上均受外流控制;内流和外流在雨带中部低层汇合抬升。切向速度的强中心出现在3 km高度,速度值随高度增加而逐渐减小。(2)两个时段的螺旋雨带也存在差异。前一个时段的螺旋雨带对流发展更旺盛,45 dBZ的回波高度为4.8 km,而后一个时段的螺旋雨带45 dBZ的回波高度仅3.2 km。垂直剖面内,前一个时刻螺旋雨带低层辐合更强,最强辐合值超过-15×10-4s-1,正是由于低层的强辐合和充足的水汽供应,才使得雨带内部中低层的回波发展旺盛。
The super typhoon Wipha(0713) was the strongest typhoon that landed on China mainland in 2007,which caused heavy precipitation in Zhejiang Province.The three-dimensional wind fields of two outer spiral rainbands were retrieved from Ningbo and Zhoushan dual-Doppler radar data.The 3-D structure of the rainbands was analyzed with the retrieved wind.The result clearly shows that the two rainbands have some similarities.There are some strong reflectivity zones in the low level of the spiral rainbands,and the strong horizontal wind speed zones correspond with the strong reflectivity zones.There are some strong updrafts in the low and middle levels of the stronger reflectivity bands where some convergence centers are found.There are downdrafts in both outer sides of the rainbands.The convergence-divergence couple and the updraft-downdraft couple play important roles in the maintenance and development of the heavy rainfall.In the vertical-cross section along the radial direction of the typhoon center,the reflectivity core in the spiral rainband tilts outward with height.There is a strong inflow toward the typhoon center below 2 km level on the outer side and outer edge of the rainband whose maximum value is 5 m/s.There is a strong outflow away from the typhoon center on the inner side and the inside of the rainband.The outflow and the inflow at the low level cause the convergence above the center of the rainband.The maximum tangential speed exists at the low level of the rainband.There are also some differences between the two spiral rainbands.The convergence at the low level of the first rainband is stronger than that of the second one.In the vertical cross-section,the maximum convergence is more than-15×10^-4 s^-1 in magnitude at the low level of the first rainband.Due to the stronger convergence and the abundant water vapour at the low level,the convection of the first spiral rainband is more active than that of the second one.The reflectivity core of the first spiral rainband greater than 45 dBZ is 4.8 km high while the reflectivity core of the second spiral rainband is only 3.2 km.
出处
《大气科学学报》
CSCD
北大核心
2010年第3期271-284,共14页
Transactions of Atmospheric Sciences
基金
国家自然科学基金资助项目(40605014)
科技部国家重点基础研究发展规划项目(2004CB418305)
科技部国家高技术研究发展计划(2007AA061901)
中国气象科学研究院灾害天气国家重点实验室基本科研项目(2008LASWZI01)
关键词
台风
螺旋雨带
双多普勒天气雷达
风场反演
三维结构
typhoon
spiral rainband
dual-Doppler weather radar
wind retrieval
3-D structure