摘要
利用龙岩S波段双偏振天气雷达,对2019年5月16日发生在福建西南部的特大暴雨过程进行了分析。结果表明:(1)南支槽东移、低空西南急流维持,以及低层中小尺度切变线和地面辐合线的南压是此次暴雨的主要影响系统。低层高能高湿,高层辐散、低层辐合,为强降水的发生提供了充足的水汽和热力条件。特大暴雨落区发生在切变线南侧及低空急流和超低空急流的左前侧。深厚的湿层配合较弱的垂直风切变,雨滴不容易蒸发,有利于产生高效率降水。(2)速度图上多次出现弱的中气旋或尺度较大的涡旋,并伴随着两次切变线南压过程,尤其是第二次切变线后部深厚持久的中气旋给连城北部造成局地特大暴雨。强回波右后侧新生回波单体发展合并加强形成了持续短时强降水过程,存在明显的列车效应。对流单体在地面辐合线附近生成,并移入西南气流辐合区及不稳定能量大值区,使回波加强发展,产生强降水,这是对流系统稳定维持的重要原因之一。低空急流峰值较降水峰值提前1~2 h出现,对强降水有一定的预报参考意义。(3)差分相移率(KDP)是指示强降水的最典型指标,KDP和强降水对应非常好,大范围的KDP指示了强降水的影响时间和降雨强度。最大降水强度时,KDP值大于4°/km,对应差分反射率因子(ZDR)值也达到4~5 dB,说明极端强降水中心的降水雨滴直径大而且数浓度相当大。整个强降水时段内,相关系数CC一直保持在0.93~0.99。径向剖面显示多普勒速度的上升气流区,ZDR柱、KDP柱指示强上升气流对应的过冷水滴集聚区。
Based on the Longyan S-band dual polarization weather radar,the extremely severe torrential rain process in the warm area of southwestern Fujian province on 16 May 2019 is analyzed.The results show that:(1)The main influencing systems of this extreme rainstorm were the eastward movement of the South Branch,the maintenance of the low-level southwest jet and the southward moving of the low-level small and medium-scale shear line and the surface convergence line.The low-level high energy and high humidity,high-level divergence and low-level convergence provided sufficient water vapor and thermodynamic conditions for the occurrence of the extremely severe precipitation.The location of the extremely severe rainfall was in the south side of shear line and the left-front sides of low-level jet and ultra-low-level jet.The deep humid layer combined with weak vertical wind shear made the raindrops difficult evaporate,which is conducive to the generation of severe precipitation.(2)Weak mesocyclones or large-scale vortices appeared many times on the velocity diagram,accompanied by two southward moving processes of shear line.Especially,the deep and persistent mesocyclones behind the second shear line triggered the localized extremely severe torrential rain in the north of Liancheng.In addition,the new echo cell developed,merged and strengthened at the right rear side of the strong echo,generating a continuous short-time severe rainfall process,and there was obvious“train effect”.One of the important reasons for the stable maintenance of the convective system is that the convective cell was generated near the surface convergence line and moved into the southwest airflow convergence area and the area with large values of unstable energy,which made the echoes strengthen,develop and produce intense rainfall.The peak value of low-level jet appeared 1—2 hours ahead of the peak value of precipitation,which has a certain reference value for forecasting severe rainfall.(3)KDP is the most typical indicator of heavy rainfall.KDP
作者
张红梅
张深寿
连晨方
Zhang Hongmei;Zhang Shenshou;Lian Chenfang(Longyan Meteorological Office, Longyan 364000, China)
出处
《气象与环境科学》
2021年第2期16-24,共9页
Meteorological and Environmental Sciences
基金
福建省自然科学基金项目(2019J01099)
福建省龙岩市科技计划项目(2018LYF5025)。
关键词
特大暴雨
双偏振雷达
列车效应
ZDR柱
KDP柱
heavy rainstorm
dual polarization weather radar
train effect
ZDR column
KDP column
