云闪K过程的三维时空特征  

The 3D Spatial and Temporal Evolution of K Process in Intra-cloud Flash

作　　者：刘恒毅[1] 董万胜[1] 张义军[1] 

机构地区：[1]中国气象科学研究院灾害天气国家重点实验室/雷电物理和防护工程实验室,北京100081

出　　处：《应用气象学报》2017年第6期700-713,共14页Journal of Applied Meteorological Science

基　　金：国家自然科学基金青年科学基金项目(41405005);国家自然科学基金项目(41375037);中国气象科学研究院基本科研业务费(2016Y002)

摘　　要：K过程是闪电放电过程中的一种放电事件。该文使用两套VHF宽带干涉仪2010年夏季在广州从化地区获取的3次云闪三维闪电辐射源定位数据,分析其中的K过程时空发展特征与地面电场特征。结果表明:宽带干涉仪观测到的K过程主要由快速发展的负极性放电事件组成,按定位结果的分布可划分为3个阶段:负极性反冲先导发生在云闪起始区域下方,沿正先导一端已有路径向闪电起始区域传播;部分反冲先导能进人之前负先导建立的通道并快速发展;反冲先导将原有通道激活后进一步促进负先导继续发展。同时使用辐射源三维定位数据计算了8次反冲先导的平均发展速度,反冲先导的发展速度为10~6~10~7 m·s^(-1)量级,与负地闪中的负极性直窜先导相似,但均小于回击速度。K process is a kind of discharge event in lightning. The study on evolution features of this event helps to increase understanding on the mechanism of lightning initiation and developing. 3 D lightning imaging data of 3 intra-cloud flashes are used to describe and analyze spatial and temporal characteristics of K events and corresponding electric field＇ s changing waveforms. These 3 D location data are recorded by2 VHF broadband interferometers at Conghua, Guangdong Province, in the summer of 2010, providing the developing image of lightning discharges with a temporal resolution of 5 μs and a spatial resolution better than 500 m. The VHF radiation of lightning is recorded by a high-speed oscilloscope with a sample rate of 1 GS · s^-1. Both fast and slow filed change antennas are employed in two broadband interferometer systems. Their decade time constants are 1 ms and 8 s,respectively. Changing waveforms of the electric field are record by an A/D card working synchronously with the oscilloscope used to record the VHF signal of lightning.Results show that K process is a kind of fast negative breakdown discharge and can be divided into 3 stages according to the distribution of VHF radiation sources located by broadband interferometers. In the first stage, negative recoil leaders occur under the initiation position of intra-cloud lightning. progress along the path of pre-existing positive leader, heading to the initiation region of lightning. In the second stage, some negative recoil leader can progress fast in the channel established by the previous negative leader of lighting initiation stage and induce a relatively large variation of electric field on the ground. In the last stage, the negative recoil leader reactivates the channel of negative leader in lighting initiation stage and facilitates the negative breakdown at the end of existing path. Speeds of the new air breakdown processes happen at the end of existing path are generally reduced to an order of 10-4 -10-5 m · s^-1. The evolution speeds of 8 reco

关 键 词：K过程 K变化 反冲先导 宽带干涉仪 闪电 

分 类 号：P427.3[天文地球—大气科学及气象学]