一次浙北梅雨锋大暴雨和强雷电的成因分析

Discussion on the Formation of Meiyu Front Torrential Rainfall and Severe Thunderstorm Case in North Zhejiang

利用常规气象资料、NCEP FNL资料、中尺度自动站资料、大气电场资料、多普勒雷达和风廓线雷达等资料,探讨了2016年6月20日浙北梅雨锋大暴雨和强雷电的成因。结果表明:本次暴雨过程中以低强度负闪为主,正闪频率较低但强度高,雨强与闪电有较好的对应关系;暴雨带距地面静止锋以南50~150 km,与700~850 hPa水汽辐合中心重合;环境大气湿层深厚、高不稳定层结、对流有效位能呈狭长分布以及弱的对流抑制能量等特点有利于持续性暴雨的发生,中层浅薄干区和中等偏强垂直风切变有利于对流风暴的维持与发展;雷达回波结构紧密,具有典型的列车效应,高度集中在0℃层以下,为低质心暖云降雨,持续风向和风速的辐合有利于MCS的维持和发展;降雨和闪电的五个阶段都对应强单体影响,雷达回波强度能较好地反映降雨强度,回波高度则与闪电强度有较好的对应关系;风廓线雷达能清楚地反映垂直方向上风向风速的波动变化,降雨和闪电的五个阶段都有波动过境,波动高度和深厚程度与降雨和闪电强度的对应关系较好,波动高与低对应闪电强与弱,波动深厚与浅薄对应降雨强与弱;3000 m高度风场是雨带变化的主要引导气流,也是产生"列车效应"的重要原因之一,低空急流和超低空急流为暴雨提供了充足的动力和水汽。

Using conventional meteorological observations,NCEP FNL data,mesoscale automatic meteorological observation data,atmospheric electric field data,Doppler weather radar and wind profile radar data,the cause of Meiyu front torrential rainfall and severe thunderstorm event that occurred over north Zhejiang on June 20 of 2016 was discussed in this paper.The results show that the torrential rainfall process is main in low intensity negative flash,and the positive flash is in low frequency but high intensity.Rainfall intensity has a good corresponding with flashes.The rainstorm belt is in the south of the ground stationary front,50 to 150 km from the front edge,and overlaps with the 700~850 hpa moisture convergence center.The characteristics of deep wet layers,high unstable stratification,narrow distribution of convective potential energy and weak convective suppression energy are beneficial to the occurrence of continuous rainstorm.Shallow dry area in middle layer and medium to strong vertical wind shear are favorable for the maintenance and development of convective storm and increase the precipitation efficiency.Radar echoes have compact structure and typical train effects,and echoes height concentrated under 0℃,which indicates that it is low-mass center warm cloud precipitation.The convergence of sustained wind direction and speed is beneficial to the maintenance and development of MCS.The five stages of rainfall and lightning correspond to the strong monomer effect,the echo intensity can well reflect the rainfall intensity,and the echo height has a good correspondence with the lightning intensity.The wind profile radar can clearly reflect the fluctuation in the vertical direction.During the five stages of precipitation and lightning,there are fluctuations passing over Huzhou.The fluctuation height and thickness have a good correspondence with rainfall and lightning intensity.High and low fluctuation corresponds to strong and weak lightning,and thick and shallow fluctuation corresponds to strong and weak rainfall.The wind field at 3000 m is the main guiding airflow for the change of rain belt,and also one of the important reasons for the train effect.Low level jet stream and super low level jet stream provide sufficient power and water vapor for the rainstorm.