基于高时间分辨率快电场变化资料的北京地区地闪回击统计特征
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Characteristics of Cloud-to-Ground Lightning Return Strokes in Beijing Based on High Temporal Resolution Data of Fast Electric Field Change
| 中文摘要: |
| 利用2014年北京闪电网观测到的4站及以上同步高时间分辨率闪电快电场变化资料，对北京地区5次雷暴过程中304次正地闪和1467次负地闪的回击特征进行了统计分析，主要包括：回击次数、10%～90%上升时间、下降时间、半峰值宽度、回击间隔、回击峰值电场强度、回击间隔和回击序数的关系等。结果表明，正、负地闪中单回击地闪所占比例分别为91.1%和24.2%，单次负地闪的平均回击次数为3.8次，观测到的最大回击数可达20次。304次正地闪首次回击的10%～90%上升时间、下降时间和半峰值宽度的算术平均值分别为4.2 μs、14.5 μs和6.2 μs；29次正地闪继后回击对应值分别为3.6 μs、12.6 μs和5.7 μs；1467次负首次回击的对应值分别为2.4 μs、23.9 μs和5.3 μs；4109次负继后回击的对应值分别为1.7 μs、19.5 μs和3.4 μs。正、负地闪回击间隔的几何平均值分别为106 ms和59 ms。负地闪回击间隔呈对数正态分布，平均回击间隔随着回击序数的增加有逐渐减小的趋势。最后，还对70次正回击、421次负首次回击和789次负继后回击峰值电场进行了统计，将其归一化到100 km的平均值分别为11.2 V/m、7.2 V/m和5.0 V/m。平均来看，负地闪首次回击峰值电场比继后回击峰值电场大1.4倍，但是有23.5%的继后回击峰值电场大于其对应的首次回击。 |
| Abstract: |
| Return stroke waveform characteristics of 304 positive cloud-to-ground (CG) flashes and 1467 negative CG flashes observed during five storms in Beijing region were analyzed based on high temporal resolution data of fast electric field change collected by Beijing Lightning Network (BLNET). Characteristic parameters presented in this work are:The number of strokes per flash, 10%-90% risetime, falling time, full width at half maxmum (FWHM), interstroke interval, peak electric field and the relationship between the interstroke interval and stroke order, etc. The results indicate that the percentages of single stroke in positive and negative CG flashes were 91.1% and 24.2%, respectively. The average number of stroke per flash for negative CG flashes was 3.8 and the max stroke number was 20. The arithmetic means of 10%-90% risetime, falling time, and half-peak width for the 304 first strokes of positive CG flashes were 4.2 μs, 14.5 μs, and 6.2 μs; the corresponding values for the 29 subsequent strokes of positive CG were 3.6 μs, 12.6 μs, and 5.7 μs; the corresponding values for the 1467 negative first strokes were 2.4 μs, 23.9 μs, and 5.3 μs, and the corresponding values for the 4109 negative subsequent strokes were 1.7 μs, 19.5 μs, and 3.4 μs, respectively. In addition, interstroke intervals of positive and negative CG flashes showed a more or less log-normal distribution and yielded the geometric mean values of 106 ms and 59 ms. Moreover, the geometric mean interstroke interval for negative CG flashes of particular multiplicity tended to decrease with the stroke order. Finally, peak electric fields of the 70 positive, 421 negative first, and 789 negative subsequent strokes, when normalized to 100 km, were 11.2 V/m, 7.2 V/m, and 5.0 V/m, respectively. On average, peak electric field for the first stroke was 1.4 times larger than its subsequent counter part for negative CG flashes. However, about 23.5% of subsequent return strokes were stronger than the corresponding first stroke. |
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