一次热带低压“弱回波”的短时强降水特征分析

使用常规天气、自动站、3D云图、单站雷达回波、Web GIS雷达拼图和风廓线雷达等资料,采用统计、对比分析和特征提取等方法,对影响江西宜春的2013年第7号强台风"苏力"(热带低压)短时强降水进行分析。结果表明:①"苏力"(热带低压)短时强降水期间,宜春处于低压中心偏东,并受台风眼南侧大片云系影响,螺旋雨带自北向南气旋式移动,强降水中心也表现为自西北向东南方移动特征。②0714过程表现为"弱回波"特征,回波结构紧密,呈带絮状,回波强度只有35~45dBz。③短时强降水影响前后,单站气象要素表现为温度平稳,湿度饱和,气压较低且随强降水产生而平缓上升,2min平均风速较小,强降水期间出现风向切变,具有典型暴雨特点,降水持续时间较长,并伴随超短时强降水出现。④"苏力"台风低压在短时强降水影响期,风廓线雷达产品水平风向风速上,高层为西北风,低层为西南风,整体风速均匀,为大范围12~20m/s的风区,并探底到600m高度,高低层存在风向风速垂直切变,但切变强度要小于其他强对流天气;径向速度为正速度,最大达8m/s,出现在最强雨强阶段;速度谱宽高低层中大小值交替出现;信噪比SNR达60~70dB;垂直风速受雨滴末速度影响,达到8m/s;大气折射率结构常数C2n因台风系统降水雨滴大和雨滴数量密集而表现出极大值-15~-14m-2/3。

Characteristics analysis of short time strong precipitation process in a weak echo tropical depression

By using routine synoptic data,meteorological elements from AWS,3D cloud pictures,data of radar echoes from a single station,Web GIS radar mosaic products and wind profiler products,based on the methods of statistics,contrast analysis and feature extraction,the short time strong precipitation process in No.7 strongest Typhoon Soulik （tropical depression）in 2013 over Yichun city of Jiangxi province was analyzed.The results show that during the short time strong precipitation process of Typhoon Soulik（tropical depression）,Yichun is controlled by the low-pressure center in the east and influenced by a wide range of spiral cloud at the south of typhoon eye.The strong precipitation center is found move from northwest to southeast when the spiral rain band counterclockwise move from north to south.The 0714 Typhoon Soulik process shows weak echo with closely structure and banded and flocculent integration.The echo intensity is only 35 -45 dBz.Before and after short time strong precipitation,meteorological elements of single station appear steady temperature and saturated humidity.The air pressure is lower and rises gently after strong precipitation occurred with small 2min average wind speed.There is wind direction shear during strong precipitation.This process have typical characteristic of the rainstorm that a longer rainfall duration and with ultra-short time strong precipitation.The characteristics of wind profiler products are more obvious during short time strong precipitation of Typhoon Soulik （tropical depression）.On the horizontal wind direction and speed of wind profiler,it can be seen that upper air prevails northwest wind and lower altitude presents southwest wind.The overall wind speed is average within the range of 12-20 m/s,and the lowest height dip is at 600 m AGL.There is a vertical shear of wind direction and speed in upper and lower air,but the shear strength is obvious smaller than other severe convection weather.The radial velocity is positive and its largest value is 8 m/s that emerges at the strongest rainfall intensity.Velocity spectrum width displays large value or small ones alternately between upper and lower altitude.The SNR is up to 60-70 dB.The vertical wind velocity is up to 8 m/s that is influenced by raindrops terminal velocity.The structure constant C2n of atmospheric refractivity presents maximum value from -15 m^-2/3 to -14 m^-2/3 ,which is mainly caused by larger and dense raindrops in typhoon precipitation.