Cloud-to-ground lightning flash characteristics from June 1984 through May 1985
Cloud-to-ground lightning flash characteristics from June 1984 through May 1985
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DOI：
10.1029/jd092id05p05640
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发表时间：
1987-05
影响因子：
--
通讯作者：
R. Orville;R. Weisman;R. Pyle;R. Henderson
中科院分区：
文献类型：
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作者：
R. Orville;R. Weisman;R. Pyle;R. Henderson
美国东海岸安装了探测闪电云对地打击的磁测向网络。实时记录时间、位置、闪光极性、行程数和峰值信号幅度。从1984年6月1日到1985年5月31日的一年中，九个测向仪的结果被展示出来。这些数据被记录在从缅因州到北卡罗来纳州以及远至俄亥俄州的西部；分析仅限于测向仪300公里范围内的闪光。从720,284次降低负电荷的首次回击中获得了峰值信号强度的测量。假设这些回程的中值峰值电流为30kA。还假设回程速度是恒定的。由此得到的分布表明，很少有负冲程的峰值电流超过100kA。还测量了17,694次降低正电荷的首次回击的峰值信号强度。这些冲程的中值峰值电流为45kA，有些峰值电流可达300-400kA。对于积极的中风和消极的中风做出了相同的假设。对于负的和正的首次回击，中值峰值信号强度，以及我们相信的峰值电流，从夏天到冬天都翻了一番。地面闪电的正极性在整个夏季和初秋都不到5%，然后在冬季增加到50%以上，并在初春恢复到10%以下。据观察，一次击打的阳性闪光率全年约为90%。观察到，一次击打的负面闪光的百分比从夏季的40%增加到1月份的约80%，到春季又回到不到50%的水平。
A magnetic direction-finding network for the detection of lightning cloud-to-ground strikes has been installed along the east coast of the United States. Time, location, flash polarity, stroke count, and peak signal amplitude are recorded in real time. Results are presented from nine direction finders for 1 year, June 1, 1984, through May 31, 1985. The data were recorded from Maine to North Carolina and as far west as Ohio; analyses were restricted to flashes within 300 km of a direction finder. Measurements of peak signal strength have been obtained from 720,284 first return strokes lowering negative charge. These return strokes are assumed to have a median peak current of 30 kA. It is also assumed that the return stroke speed is constant. The resulting distribution indicates that few negative strokes have peak currents exceeding 100 kA. Measurements have also been obtained of peak signal strength from 17,694 first return strokes lowering positive charge. These strokes have a median peak current of 45 kA, with some peak currents reaching 300–400 kA. The same assumptions are made for positive strokes as for negative strokes. The median peak signal strength, and we believe the peak current, doubles from summer to winter for both negative and positive first return strokes. The polarity of ground flashes is observed to be less than 5% positive throughout the summer and early fall, then increases to over 50% during the winter, and returns to less than 10% in early spring. The percent of positive flashes with one stroke is observed to be approximately 90% throughout the year. The percent of negative flashes with one stroke is observed to increase from 40% in the summer to approximately 80% in January, returning to less than 50% in the spring.