青海地区一次雷暴的地闪活动及云内的电场探空观测

2016年夏季在青海大通地区获得一次局地雷暴云内的电场探空资料,结合雷达、地闪定位资料,详细分析了该雷暴的地闪活动特征及云内的电荷结构.结果显示,该雷暴过程的负地闪在时间上呈间歇性发生,在空间分布上表现为不连续,且所有的正地闪都发生于雷暴的成熟阶段.在雷暴成熟阶段与消散阶段过渡期获得云内的垂直电场廓线表明,雷暴内的电荷结构在探空阶段呈四极性,最下部为处于暖云区内负电荷区,往上依次改变极性.最上部的正电荷区由于数据丢失无法判断其上边界外,其余3个电荷区的海拔高度分别为:5.5～5.7km(3.4～2.3℃)、5.7～6.2km(2.3～-0.4℃)和6.2～6.6km(-0.9～-1.7℃),对应的电荷密度为-1.81nC·m^-3、2.47nC·m^-3和-1.76nC·m^-3.其中,下部正电荷区的强度最大,其次为上部的负电荷区.通过分析电荷区分布与正地闪活动的关系,认为暖云区内负电荷区的形成有利于诱发下部正电荷区的对地放电.

The activities of cloud-to-ground flashes and the electric field sounding results of a local thunderstorm in Qinghai region

Electric field (E) sounding data was obtained in one case of local thunderstorm in Qinghai region in summer of 2016. Combining the radar data and cloud-to-ground (CG) flashes location data, the CG flashes activities and charge structure of the thunderstorm were studied in detail. The results show that the evolution of negative CGs is intermittently and the spatial distribution is discontinuously. All the positive CG flashes occurred in the mature stage of thunderstorm. Electric field sounding data was obtained in the transitional period of the mature stage and the dissipating stage, and charge regions in the thunderstorm were figured out based on the vertical E profile. Totally four charge regions were found in the thunderstorm and charge polarities were alternate in a vertical direction with a negative charge region at the lowest in the warm cloud region. The upper boundary of the upper positive region was unknown because the sounding data was missed, the altitudes of other three charge regions were at 5.5~5.7 km (3.4~2.3℃), 5.7~6.2 km (2.3~-0.4℃) and 6.2~6.6 km (-0.9~-1.7℃), and their charge densities were -1.81 nC·m^-3, 2.47 nC·m^-3 and -1.76 nC·m^-3, respectively. The relationship between positive CG flashes and charge structure was analyzed, and we speculated that the formation of a negative charge layer in the warm cloud region was in favor of causing the positive CG flashes from the lower positive charge region.