Electric field change and VHF waveforms of Positive Narrow Bipolar Events in Mississippi thunderstorms
Electric field change and VHF waveforms of Positive Narrow Bipolar Events in Mississippi thunderstorms
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DOI：
10.1016/j.atmosres.2020.105000
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发表时间：
2020-04
影响因子：
5.5
通讯作者：
S. Bandara;T. Marshall;S. Karunarathne;M. Stolzenburg
中科院分区：
文献类型：
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作者：
S. Bandara;T. Marshall;S. Karunarathne;M. Stolzenburg
使用快速天线（FA，带宽 16 Hz - 2.6 MHz）和 VHF 天线（Log-RF，带宽 186–192 MHz）研究了密西西比雷暴中的正窄双极事件（+NBE）。使用两个传感器确定了 201 个正 NBE 的波形特征。 +NBE 按两种方式分类：根据 FA 波形分为 A-D 型，根据 +NBE 相对于其他闪电事件的发生情况分为三组，称为孤立、非孤立和 INBE。 （INBE 启动云内闪存。）188 个正 NBE 的 FA 波形特性与之前的研究基本一致。 +NBE 的 VHF 波形特性此前尚未研究过。 201 个正 NBE 的 VHF 功率范围为 0.1-88.4 kW，平均值为 7.8 kW。 C 型和 D 型正 NBE 往往比 A 型和 B 型（平均功率为 1.9 和 4.0 kW）更有能量（平均 VHF 功率为 9.2 和 13.2 kW）。 +NBE 的 INBE 组的 VHF 功率范围 (0.2–88.4 kW) 比非隔离组和隔离组的组合功率范围 (0.1–26.7 kW) 更大。 INBE 组的平均峰值功率 (9.9 kW) 也比非隔离组和隔离组（分别为 4.0 和 8.7 kW）更大。然而，53% 的 INBE 的峰值 VHF 功率< 5 kW，因此 INBE 不需要很大的功率来启动云内闪光。对于 201 个阳性 NBE 中的 90%，FA 峰值幅度与 Log-RF 峰值功率之间的时间差幅度≤2 μs，但 FA 峰值幅度与 Log-RF 峰值功率几乎没有相关性。
Positive Narrow Bipolar Events (+NBEs) in Mississippi thunderstorms were studied using fast antennas (FA, bandwidth 16 Hz - 2.6 MHz) and VHF antennas (Log-RF, bandwidth 186–192 MHz). The waveform characteristics of 201 positive NBEs were determined using both sensors. The +NBEs were classified in two ways: by FA waveform into Types A-D and by +NBE occurrence relative to other lightning events into three groups called Isolated, Not-Isolated, and INBE. (An INBE initiates an intracloud flash.) The FA waveform properties of 188 positive NBEs were mainly in reasonable agreement with previous studies. The VHF waveform properties of +NBEs have not been studied previously. The VHF powers of 201 positive NBE ranged from 0.1–88.4 kW with an average value of 7.8 kW. Types C and D positive NBEs tended to be more energetic (average VHF powers of 9.2 and 13.2 kW) than Types A and B (average powers of 1.9 and 4.0 kW). The INBE group of +NBEs had a larger range of VHF powers (0.2–88.4 kW) than the combined power range of the Not-Isolated and Isolated groups (0.1–26.7 kW). The INBE group also had a larger average peak power (9.9 kW) than the Not-Isolated and Isolated Groups (4.0 and 8.7 kW, respectively). However, 53% of INBEs had peak VHF power < 5 kW, so an INBE does not require a large power to initiate an intracloud flash. For 90% of the 201 positive NBEs the magnitude of the time difference between the FA peak amplitude and the Log-RF peak power was ≤2 μs, but the FA peak amplitude showed almost no correlation with the Log-RF peak power.