北京和广州地区云闪初始击穿电场变化特征

Variation Characteristics of Cloud Flashes Initial Breakdown Electric Field Observed in Beijing and Guangzhou

对比分析了北京和广州地区各100例云闪初始阶段前30 ms快电场变化波形上初始击穿脉冲的特征。依据脉冲的结构特征,两地区的云闪初始击穿脉冲可分为单极性单峰型、单极性多峰型、双极性单峰型和双极性多峰型脉冲,两地区均以单极性和单峰型脉冲为主。对脉冲参量特征的统计发现,脉冲的10%-90%上升时间、半峰值宽度地区差异性小于脉冲类型差异性;双极性单峰型脉冲的半峰值宽是单极性单峰型的1.2倍。不同类型脉冲过零时间的中值、平均值在10μs左右量级,且广州地区较北京地区的大;云闪初始击穿脉冲宽度平均值显著小于相同地区正地闪的,而脉冲间隔显著大于正地闪的。初始击穿脉冲最为集中的出现在云闪最初的1~2 ms,其比例随时间以显著的负指数分布下降。研究发现,双极性脉冲的过零时间与脉冲宽度之间、起始半周期峰值幅度与过冲幅度之间均存在较好的线性关系。

The fast electric field change data within the first 30 ms of cloud flashes are compared and analyzed to study the characteristics of initial breakdown pulses of cloud flashes in Beijing and Guan- gzhou（100 cases each）. The initial breakdown pulses of cloud flashes in the two regions are categorized into four types according to the characteristics of pulse structures, including unipolar pulse with single peak, unipolar pulse with multiple peaks, bipolar pulse with single peak and bipolar pulse with multiple peaks. Unipolar pulses and pulses with single peak are the main types of pulses in both two regions. It is found that pulse ty time and half peak pe difference has much more influence on pulse parameters such as 10%--90% width than that of regional difference. The average value of half peak width of rising bipolar pulse with single peak is 1.2 times of that of unipolar pulse with single peak. The average values and me- dian values of zero crossing time of different types of pulses are in the order of 10 I^S, and those values are found to be bigger in Guangzhou than that in Beijing. In the same place, the average value of pulse width of initial breakdown pulses of cloud flashes is found to be significantly smaller than that of positive cloud to ground flashes, but the average value of pulse interval of cloud flashes is significantly bigger than that of positive cloud to ground flashes. The highest occurrence probability of initial breakdown pulses is within 1 --2 ms of the beginning of cloud flashes, and the occurrence probabilities of pulses decrease with time in a significant negative exponential are shown between zero crossing time and distribution. pulse width Studies have found that obvious liner correlations and between peak amplitude of initial half cycle and overshoot amplitude of bipolar pulses.