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首页> 外文期刊>Atmospheric research >Characterizing three types of negative narrow bipolar events in thunderstorms
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Characterizing three types of negative narrow bipolar events in thunderstorms

机译：在雷暴中表征三种类型的负窄双极事件

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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：具有16 Hz-2.5 MHz和VHF功率传感器（Log-RF）的带宽的快速天线（FM）的数据用于检查负窄双极事件或NNBES。主要重点是在低空（<8.0 km）nnbes上，发起负云到地（-cg）闪光灯;以前已经研究过很少的低空NNBES。相比之下，还检查了24个高空（> 8.0公里）NNBES。发现低空NNBES具有两个称为NNBE（L）和NNBE（H）的类型。 NNBE（L）S具有典型的NBES的双极性FA波形，而NNBE（H）S具有单极的FA波形。假设NNBE（H）S可以是NNBE（L）S的弱版本，其中双极波形的第二个过冲部分太弱而无法检测到FA传感器噪声。 33 NNBE（L）和NNBE（H）S发生在平均海拔6.2 km（范围4.6-7.8 km），平均范围标准化（至100km）幅度为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属性比高海拔NNBES的相同性质和发起斜拉箱（IC）闪光的正NBE的相同性质较小且较弱;这些分析表明-CG闪烁比IC闪烁更容易启动。 868 -cg闪烁的FA和log-rf数据的目视检查显示，只有33次闪烁（4％）之前只有NNBE（L）或NNBE（H），所以可能做了96％的-CG闪光灯不以nnbe开头。

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