Observations of electric fields sounding in the mature stage of a thunderstorm

In the summer of 2021, observations of balloon-borne electric field within thunderstorms were conducted in Nanchang City, Jiangxi Province, China. On 24 August, two electric field profiles were obtained during the mature stage of a local thunderstorm in Nanchang City, Jiangxi Province, China. The initial sounding (S1) and subsequent sounding (S2) were initiated with a 6 mins interval. However, S1 entered the weak echo region from the leading edge of the thunderstorm and entered the 30 dBZ region at an altitude of 6 km, while the second sounding (S2) entered from the cloud base and entered the strong echo region at approximately 0°C. At altitudes more than 6 km, the observations were synchronized (with a horizontal distance of 3-4 km). The results showed that two sounding balloons traversed a total of eight and eleven charge regions for S1 and S2, respectively, and the predominant charge regions conformed to the tripole charge structure. The synchronized observations above 6km indicated that the distribution of charge regions within the thunderstorm indeed exhibits horizontal inhomogeneity. In addition, an anomalous negative charge region was identified in the upper portion of the thunderstorm, with a depth ranging from 2.3 to 2.7 km, which is larger than the normal negative screening layer. It is notable that a pair of charges with negative upper and positive lower charges is observed at 8.5 and 10 km, which is difficult to explain reasonably using non-inductive charging mechanisms. This indicates the complexity of the formation of charge region within clouds.2021年夏季，中国江西省南昌市开展了雷暴内气球搭载电场（balloon-borne electric field）观测实验。8月24日，在南昌当地一次雷暴成熟阶段获取了两份电场廓线数据。初始探空（S1）与后续探空（S2）的发射间隔为6分钟。不过，S1从雷暴前缘进入弱回波区，并在海拔6公里处进入30 dBZ（分贝反射率因子）区域；而S2则从云底进入，并在约0℃高度处进入强回波区。在海拔6公里以上的空域，两次探空实现了同步观测（水平距离3~4公里）。研究结果显示，S1和S2分别穿越了8个和11个电荷区，主导电荷分布符合三极性电荷结构（tripole charge structure）。6公里以上的同步观测表明，雷暴内部的电荷区分布确实存在水平非均质性。此外，在雷暴上部发现了一个厚度为2.3~2.7公里的异常负电荷区，其厚度大于常规负屏蔽层。值得注意的是，在海拔8.5公里和10公里处观测到一对上下排布的电荷结构：上部为负电荷，下部为正电荷，这一现象难以通过非感应起电机制（non-inductive charging mechanisms）进行合理解释，反映了云内电荷区形成过程的复杂性。