On the Intensity of First Return Strokes in Positive Cloud‐To‐Ground Lightning in Winter
On the Intensity of First Return Strokes in Positive Cloud‐To‐Ground Lightning in Winter
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DOI：
10.1029/2022jd037282
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发表时间：
2022
期刊：
影响因子：
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通讯作者：
Ting Wu;Daohong Wang;N. Takagi
中科院分区：
文献类型：
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作者：
Ting Wu;Daohong Wang;N. Takagi
分析了 14 站点快速天线闪电测绘阵列在一个冬季观测到的约 700 次正云对地闪电的第一次回击 (RS) 强度。根据 RS 电场变化 (E-change) 波形的范围归一化峰值幅度估计的峰值电流用于表示其强度。研究发现，正RS的峰值电流与其波形参数（包括脉冲宽度、上升时间、下降时间和半峰宽度）呈正相关。雷电起始和第一个RS之间的时间差与正RS的峰值电流密切相关，强正RS通常与较小的时间差相关。正 RS 的峰值电流还与前面的先导脉冲的幅度相关。在 674 个正 RS 中，232 个前面有正引导脉冲，这些脉冲的幅度与 RS 的峰值电流正相关。分析峰值电流大于 150 kA 的强正 RS 并与强负 RS 进行比较。虽然强负 RS 通常会产生与典型 RS 波形不同的异常 E 变化波形，但强正 RS 不具有这种特殊特征。最强的正 RS 通常发生在闪电启动后很短的时间内（通常小于 10 毫秒），并且更有可能与正初步击穿脉冲相关。据推测，这些最强的 RS 之前通常有一个速度约为 106 m/s 的快速向下的正先导。讨论了导致强正 RS 的电荷结构。
Intensities of about 700 first return strokes (RSs) in positive cloud‐to‐ground lightning flashes observed by a 14‐site Fast Antenna Lightning Mapping Array in one winter season are analyzed. Peak currents estimated from range‐normalized peak amplitudes of electric field change (E‐change) waveforms of RSs are used to represent their intensities. It is found that peak currents of positive RSs are positively correlated with their waveform parameters including pulse width, rise time, fall time and half‐peak width. Time differences between lightning initiation and first RSs are closely related with peak currents of positive RSs, with strong positive RSs usually associated with small time differences. Peak currents of positive RSs are also related with amplitudes of preceding leader pulses. Out of 674 positive RSs, 232 are preceded by positive leader pulses, and amplitudes of these pulses are positively correlated with peak currents of RSs. Strong positive RSs with peak currents larger than 150 kA are analyzed and compared with strong negative RSs. While strong negative RSs usually produce abnormal E‐change waveforms that are generally different from typical RS waveforms, strong positive RSs do not have such special features. Strongest positive RSs usually occur within a very short time (usually smaller than 10 ms) after lightning initiation and are more likely to be associated with positive preliminary breakdown pulses. It is inferred that these strongest RSs are usually preceded by a fast downward positive leader with a speed on the order of 106 m/s. Charge structures responsible for strong positive RSs are discussed.