Grant-in-Aid for International Scientific Research.
|Research Institution||Gifu University|
WATANABE Teiji Gifu Univ., Faculty of Eng., Prof., 工学部, 教授 (20021595)
WANG D Gifu Univ., Faculty of Eng., Assistant Prof., 工学部, 助手 (20273120)
TAKAGI Nobuyuki Gifu Univ.Faculty of Eng., Asociate Prof., 工学部, 助教授 (80179415)
NAKAMURA Kouichi Nagoya Inst.of Tech., Dept of Information, Asociate Prof., 電気工学科, 助教授 (10024283)
NAKANO Minoru Toyata College of Tech., Dept.of Tech., Prof., 情報工学科, 教授 (50023685)
KAWASAKI Zenichiro Osaka Univ.Dept.of Eeg., Asociate Prof., 工学部, 助教授 (60126852)
郭 昌明 中国上海気象研究所, 所長, 教授
劉 欣生 中国科学院蘭州高原大気物理研究所, 所長, 教授
GUO C Shanghai Inst.of Mesoscale Meteorol., CAS,China, Prof., Director
LIU X Lanzhou Inst.of Plateau Atoms.Phys., CAS,China, Prof., Director
|Project Fiscal Year
1996 – 1996
Completed(Fiscal Year 1996)
|Budget Amount *help
¥3,400,000 (Direct Cost : ¥3,400,000)
Fiscal Year 1996 : ¥3,400,000 (Direct Cost : ¥3,400,000)
|Keywords||Plateau thunderstorms / Cloud-to-ground discharge / Positive discharge / Negative discharge / Return stroke / Electric field change / 高原雷 / 対地放電 / 正極性放電 / 負極性放電 / 帰還雷撃 / 電界変化 / 雷 / 放電 / 雷雲 / 正極性落雷|
A comprehensive observation on lightning occurred in an inner land plateau area called Lanzhou, northwest of China, was conducted during July 1 to August 20 of 1996. Data including simultaneous 5-station slow electric field changes, lightning video photos as well as radar echoes was obtained. Following are some primary results we have got by using this data :
1. Concerning the thunderstorms in summer in the inner land plateau area of China, the percentage of positive cloud-to-ground (CG) discharge over all of the CG discharge was higher than that in other place, and varied with thunderstorms. It seems that the above property did not depend on the height of-10 C temperature layr or the maturity of thunderstorms.
2. Statistical characteristics, such as multiple-strike number and the slow front risetime of an electric waveform produced by a return stroke of positive CG discharges, are similar to that of the winter thunderstorms in Hokuriku reported sofar.
3. The height of negative charge lay
r was 3-5km above the ground, which is consistent with the height of-10 C temperature layr. The magnitude of average charges transferred to ground by each strike was about two times of that of negative CG discharges of common summer thunderstorms.
4. For the positive CG discharge, the ratio of the lightning whose time difference between the beginning of relative preliminary inter-cloud weak discharge and the occurrent of return stroke was longer than 100 ms was about 60%.
5. The occurrence of pulses being company with return strokes varies with the discharge polarity. About 50% of pulses occurred over the time before the return stroke for the negative one, while most of them occurred at the time of return stroke for the positive one.
6. The average persistent time of continuous current and the average persistent time of leaders were 38ms and 51ms respectively for positive CG discharges.
7. The average risetime of slow front of the first stroke was 11 microsecond for negative discharges and 24 microsecond for the positive one. For the continuing stroke, the average rise-time was 4 microsecond and 14 microsecond for negative and positive respectively. All of them were more than two times longer of those of common summer thunderstorms.
8. It seems that there was a close relation between the slow front persistent time of a continuing stroke and the inter-stroke interval time of this strike. The longer the interval time was, the longer the slow front risetime.
9. For the continuing stroke, the analysis also indicates that the longer the slow front risetime was, the bigger the amplitude of the stroke electric field change. No such a relationship was found for the first stroke.
10. The average ratios of the part of electric field change of slow front over the peak change were 46% and 21% for the first stroke and the continuing stroke respectively for negative discharge, and were 54% and 27% respectively for positive one. All of these percentages are as the same as those of the common summer thunderstorms. Less