广州两次雷暴过程地闪与大气电场特征对比分析

Comparative analysis of characteristics of ground lightning and atmospheric electric field of two thunderstorm processes in Guangzhou

利用安装于广州塔塔顶500 m的大气电场仪(简称电场)数据、广州双偏振雷达资料、粤港澳闪电定位系统数据和ERA5再分析资料等数据,对比分析了2020年8月15日和9月23日广州两次雷暴天气过程的地闪活动特征以及地闪活动与电场变化特征的关系。结果表明:由局地热力不稳定引起的“局地性雷暴”地闪频次低、伴随弱降水,而由中尺度系统引发的“系统性雷暴”地闪频次高、伴随短时强降水。两次过程的地闪频次和电场变化呈双峰分布,地闪爆发时电场变化显著,频域能量达到峰值。“系统性雷暴”的消亡阶段电场在正负极之间大幅度缓慢波动,呈现阻尼振荡(End Of Storm-Oscillation,EOSO)特征,而“局地性雷暴”消亡时电场未出现此特征。时域下电场剧烈变化和频域能量明显提高时,意味着雷暴云团正在靠近或附近有闪电发生;电场频域能量迅速减小且集中于低频段,表明雷暴正在消亡或远离测站。电场的时频特征对雷暴的生消具有指示性作用,为电场数据与其他资料融合应用于雷电风险预警予以参考。

Based on the data from an atmospheric electric field(AEF)meter at 500 m from the top of Canton Tower,dual-polarimetric radar in Guangzhou,Guangdong-Hong Kong-Macao lightning location system and ERA5 reanalysis data,this study comparatively investigates the characteristics of cloud-to-ground lightning(CG)activity and the relationship between CG activity and variation features of AEF in two thunderstorms in Guangzhou on August 15 and September 23,2020.The results show that the“local Thunderstorm”caused by local thermal instability possesses is associated with less lightning frequency and weaker precipitation,while the“systematic Thunderstorm”caused by mesoscale system possesses is associated with higher lightning frequency and short-term heavy precipitation.The lightning frequency and variation of AEF in the two thunderstorm processes display the distributions with two peaks,and the peak of AEF variability and time-frequency domain energy correspond well to the lightning outbreak stage.In the decay of“systematic Thunderstorm”,AEF fluctuates greatly and slowly between the positive and negative poles for a relatively long time,showing the characteristic of End of Storm-Oscillation(EOSO).However,such a characteristic of the oscillation of AEF does not occur in the decay of the“local Thunderstorm”.The lightning often comes soon,when the AEF variability and time-frequency domain energy increase significantly.The thunderstorm is often dying out or moving away from the station,when the time-frequency domain energy decreases significantly and concentrates in the low frequency band.The variation characteristics of AEF in time domain and frequency domain play an indicative role in the occurrence and dissipation of thunderstorm.This can be considered as a reference for converged application of the atmospheric electric field data with other data in lightning risk early warning.