一次雹暴的闪电特征和电荷结构演变研究  

Total lightning characteristics and the electric structures e- volution in a hailstorm

作　　者：郑栋[1,2] 张义军[1,3] 孟青[1] 吕伟涛[1] 易笑园[4] 

机构地区：[1]中国气象科学研究院雷电物理和防护工程实验室,北京100081 [2]中国科学院研究生院,北京100039 [3]中国气象科学研究院灾害天气国家重点实验室,北京100081 [4]天津市气象局,天津300074

出　　处：《气象学报》2010年第2期248-263,共16页Acta Meteorologica Sinica

基　　金：国家自然科学基金(40475002);国家重点基础研究发展规划项目(2004CB418300)

摘　　要：综合利用SAFIR3000三维闪电定位系统的全闪定位资料与雷达结合对2005年5月31日发生于北京的一次冰雹过程的闪电活动和电荷结构演变特征进行了综合分析。结果表明:该雷暴的闪电活动有两次活跃期,第一个活跃期产生了降雹,降雹结束后,闪电活动突然减少,之后的活跃期产生了更多的闪电,其中一部分处于云砧区。闪电活动峰值超前降雹5 min左右,闪电活动中的地闪仅占6.16%,但正地闪占总地闪的比例达20%,且降雹前的正地闪比例较降雹后要高,降雹发生后,正地闪很少发生。降雹阶段,参与放电的主要电荷区表现为反极性结构,-40℃左右区域为参与放电的主负电荷区,-15℃左右区域为参与放电的主正电荷区,在正电荷区之下,短暂存在一个较弱的负电荷区。降雹结束后,电荷结构经历了持续的快速调整过程,在第2次闪电活跃期,参与放电的主要区域表现为正常的三极性结构,即上正-中负-下正,受西风气流的影响,此三极性结构出现倾斜。动力和微物理过程的分析表明,闪电活动和电荷结构的特征与雷暴云内的动力、微物理过程紧密相关。文中对反极性电荷结构形成的可能机理进行了讨论,并且认为,具有强烈上升气流的灾害性天气可能更易形成反三极性的电荷结构,并在下部两个电荷区的作用下产生较多的正地闪。Total lightning data observed by the SAFIR3000 3-D lightning locating system were combined to the data of radar to analyze the characteristics of the lightning activities and electric structures of a hailstorm occurring in Beijing on 31 May 2005. The results indicated that there were two active periods for lightning activities during the hailstorm process.The hail shooting was found in the first period.After the end of the hail shooting,lightning frequency was decreased suddenly.However,more lightning activities occurred in the second period with lots of them appearing in the cloud anvil region.The peak time of lightning activities was prior to the hail shooting about 5 minutes.Only 6.16%of the total lightning discharges were cloud-to-ground （CG） lightning discharges.Among them,20%were positive cloud-to-ground（PCG） lightning discharges.In addition, the PCG lightning discharges before the hail shooting were more than those after the hail shooting.In the stage of the hail shooting,the electric structure of the hailstorm was inverted,i.e.,the main negative charge region lay around the-40℃-level, and the main positive charge region lay around the-15℃-level.In addition,a weak negative charge region had existed below the positive charge region transitorily.With fast and persistent adjustment after the hail shooting,the electric structure changed to a pattern of usual tripole with the upper positive charge,the middle negative charge and the lower positive charge configurated.However,the electric structure was tilted under the action of the west wind in the middle and upper levels.It was found that lightning activities and electric structures showed a close relationship with dynamic and microphysical processes in the hailstorm.The reason why the inverted electric structure formed was discussed in the article.It was believed that it was easier for severe storms with very strong updraft to form inverse tripolar electric structure than for usual storms and produce more PCG lightning under the effect of the lower

关 键 词：闪电活动 电荷结构 非感应起电机制 双向先导传输 

分 类 号：P427.3[天文地球—大气科学及气象学]