Spatiotemporal characteristics of positive cloud-to-ground lightning discharges and bidirectional leader of the lightning

作     者：Krehbiel Paul 

作者机构：New Mexico Institute of Mining and Technology Socorro New Mexico 87801 USA 

出 版 物：《Science China Earth Sciences》 (中国科学（地球科学英文版）)

年 卷 期：2006年第49卷第2期

页      面：212-224页

核心收录：

学科分类：07[理学] 070601[理学-气象学] 0708[理学-地球物理学] 0706[理学-大气科学] 0704[理学-天文学] 

基　　金：supported by the National Natural Science Foundation of China(Grant No.40475002) the Ministry of Science and Technology of China(Grant No.2003BA904B10) 

主　　题：positive CG lightning, radiation characteristics, bidirectional leader. 

摘      要：The three-dimension spatiotemporal development characteristics of positive cloud-to- ground (CG) lightning discharges have been analyzed by using the data measured by the lightning mapping array system with high time and space resolution. The results indicate that a positive CG lightning discharge can be divided into three stages based on the characteristics of its development. The first stage is discharge process in cloud with a long duration preceding the return stroke. This process with an average of 370 ms propagated at velocity of 105 m/s and produced intensive radiation with a magnitude equal to that of the negative leader. During this stage, the lightning channels de-veloped horizontally in the positive charge region with few branches as the negative polarity break-down. During the stage after the return stroke of the positive CG lightning, the lightning channels propagated at velocity of 2 times faster than that before the return stroke. This stage involved lots of positive fast impulses and corresponded to the continuing current process producing less and dis-persed radiation points and more intensive radiation powers. During the final stage of the positive CG lightning, the lightning channels developed at velocity equal to that before the return stroke and the radiation points appeared mainly at the ends of channel. The spatiotemporal development character-istics of the positive CG lightning are very different from that of the negative CG lightning. All of the radiation points of the positive CG lightning appeared in the positive charge region of cloud. Little or no radiation was detected during the positive leader just before the return stroke. The duration of the positive CG lightning was an average of 730 ms. The positive CG lightning discharges with lasting time of 500―600 ms were 43%. 90% of the positive CG lightning discharges involved one return stroke, the most return stroke number being four. The current of the return stroke was an average of 36.5