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Characterizing three types of negative narrow bipolar events in thunderstorms

机译：表征雷暴中三种负性窄双极事件类型

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Data from fast antennas (FM) with bandwidth of 16 Hz-2.5 MHz and VHF power sensors (Log-RF) with bandwidth of 186-192 MHz are used to examine negative narrow bipolar events, or NNBEs. The main focus is on low-altitude ( 8.0 km) NNBEs that initiate negative cloud-to-ground (-CG) flashes; very few low-altitude NNBEs have been studied previously. For comparison, 24 high-altitude ( 8.0 km) NNBEs are also examined. The low-altitude NNBEs are found to have two types called NNBE(L) and NNBE(H). NNBE(L)s have a bipolar FA waveform typical of NBEs while NNBE(H)s have a unipolar FA waveform. It is hypothesized that NNBE(H)s may be weak versions of NNBE(L)s in which the second, overshoot part of the bipolar waveform is too weak to detect amid the FA sensor noise. Together the 33 NNBE(L)s and NNBE(H)s occurred at an average altitude of 6.2 km (range 4.6-7.8 km), had average range-normalized (to 100 km) amplitude of 0.4 V/m (range 0.06-1.5 V/m), and had average VHF power of 130 W (range 1-1300 W). These low-altitude NNBE properties are substantially smaller and weaker than the same properties of the high-altitude NNBEs and of positive NBEs that initiate intracloud (IC) flashes; these analyses indicate that -CG flashes are easier to initiate than IC flashes. Visual inspection of the FA and Log-RF data of 868 -CG flashes showed that only 33 flashes (4%) were preceded by either an NNBE(L) or NNBE(H), so 96% of the -CG flashes investigated probably did not begin with an NNBE.
机译：来自带宽为16 Hz-2.5 MHz的快速天线（FM）和带宽为186-192 MHz的VHF功率传感器（Log-RF）的数据用于检查负窄双极事件或NNBE。主要关注于低空（<8.0 km）NNBE，它们启动负向云对地（-CG）闪烁；以前很少研究低空NNBE。为了进行比较，还检查了24个高海拔（> 8.0 km）NNBE。低空NNBE具有两种类型，分别称为NNBE（L）和NNBE（H）。 NNBE（L）具有NBE典型的双极性FA波形，而NNBE（H）具有单极性FA波形。假设NNBE（H）可能是NNBE（L）的弱版本，其中双极性波形的第二个过冲部分太弱，无法在FA传感器噪声中检测到。 33个NNBE（L）和NNBE（H）一起出现在平均高度6.2 km（范围4.6-7.8 km）上，平均范围归一化（至100 km）振幅为0.4 V / m（范围0.06-） 1.5 V / m），平均VHF功率为130 W（范围1-1300 W）。这些低空NNBE属性比高空NNBE和引发云内（IC）闪烁的正NBE的相同属性要小得多和较弱；这些分析表明，-CG闪烁比IC闪烁更容易启动。目视检查868 -CG闪烁的FA和Log-RF数据表明，只有33次闪烁（4％）之前是NNBE（L）或NNBE（H），因此研究的96％-CG闪烁可能是不是以NNBE开头。

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