闪电宽带电场三维定位及其回波特征

利用自制闪电宽带电场三维定位系统， 分析了山东地区一次雷暴过程闪电三维时空结构。结果表明， 在云内击穿放电整个时间序列中， 辐射源空间分布（对应强电场区分布）呈现明显的三极性分层电荷结构， 并分布在3个高度层次： 6~8 km为上部正电荷区, 4~6 km为中部负电荷, 2.5~4 km为下部次正电荷区。云内放电首先出现在中部负电荷区， 然后产生向上发展的负流光进入上部正电荷区传输， 形成向上发展的云闪； 随着雷暴发展， 产生向下发展的负流光进入下部次正电荷区， 形成向下发展的云闪， 且能维持到雷暴发展后期。结合雷达回波分析表明, 雷达回波的强度影响着闪电活动， 强回波区的增加会使得强电场区域增加， 但是强电场区域并不与最强回波区域对应， 除下部正电荷区的底部会有部分辐射源出现在回波强度为40~50 dBz的区域中以外， 大多数的辐射源出现在25~35 dBz的中等回波区范围内， 强回波区域中通常较少出现击穿放电。

Characteristics of Three-Dimensional Lightning and Radar Echo Using the Broadband Field Lightning Mapping System

The three-dimensional temporal and spatial lightning radiation sources of a thunderstorm in Shandong are located using the broadband electric field lightning mapping system which designed by us. The system takes the advantage of GPS technology to measure the arrival times of signal of lightning at each station and can be used to study the temporal and spatial development processes of lightning at a high spatial resolution. The result indicates that the temporal and spatial distributions of radiation sources (corresponding the distribution of intense electric field region) takes on tripole structure with three distinct layers during the whole intracloud discharge. The three layers locate in the heights of 6～8 km,4～6 km and 2.5～4 km,respectively. This tripole structure is inferred to correspond the tripole charge structure of a typical thunderstorm. Intracloud discharges usually originate from the middle negative charge region and then propagate upward into the upper positive charge region. With the development of the thunderstorm,many negative leaders propagated downward into the lower positive charge region and produced inverted intracloud discharges. These types of discharges sustained until the final stage of the storm. It is found that the positive cloud-to-ground flash rate increased due to the presence of the strong lower positive charge region in the thunderstorm. The comparison between the location of lightning radiation sources and radar echo shows that the intensity of radar echo affects lightning activities. Most of radiation sources located in the echo region of 25～35 dBz while a few radiation sources in the lowest positive layer appeared in the echo region of 40～50 dBz. Apperantly,the most active lightning radiation regions do not correspond with the most intense echo region,although the extension of the intense echo region could cause the extension of the active lightning radiation region.