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Research on Lightning Activity in the Tropics

热带地区闪电活动研究

基本信息

批准号：
05045027
负责人：
ISHII Masaru
金额：
$ 3.84万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-05045027/
关键词：
Lightning Tropics Lightning Discharge Lightning Location

项目摘要

1. In the first year, the lightning location system, consisting of three electromagnetic pulse receivers, was installed. These receivers are precisely time-synchronized by GSP,and observe lightning electromagnetic pulses including their incoming directions. In the second year, a fourth station was added to improve the performance of the system.2. A new technique of lightning location, which combines the direction finding and the time-of-arrival techniques, is employed in the Java lightning location system. The theoretical analysis shows that the new technique is quite effective in increasing the detection efficiency without much deteriorating the location accuracy. The time-of-arrival technique requires at least three stations simultaneously receiving the same electromagnetic pulse to locate its source, whereas two stations only are required in the new technique. The influence of the apparent propagation delay of the electromagnetic pulse over land due to its finite conductivity is theoretically investigated, and the similarity of the theoretical and observed results proves that the finite ground conductivity really affects the location accuracy. These newly obtained results are published on the Transactions of IEE of Japan.3. The analysis of data for one and a half years reveals the following lightning characteristics in the tropics. The yearly variation is characterized by the rainy season and the dry season. Lightning activity is observed almost every day during the rainy season roughly from October until April. The characteristics of lightning do not much differ from those of summer in Japan, though the lightning flash density is about one order higher on the Java Island. The diurnal variation exists and differs on the land and on the sea. These characteristics of lightning in the maritime-continent area are revealed for the first time, and will be presented at the International Conference on Atmospheric Electricity in June 1996.

1. 在第一年，安装了由三个电磁脉冲接收器组成的闪电定位系统。这些接收器通过GSP精确地进行时间同步，并观察闪电电磁脉冲，包括它们的入射方向。第二年，又增加了第四个监测站，以提高系统的性能。在Java闪电定位系统中，采用了一种新的闪电定位技术，将测向技术和到达时间技术相结合。理论分析表明，该方法在不影响定位精度的前提下，有效地提高了检测效率。到达时间技术需要至少三个台站同时接收同一电磁脉冲来定位其源，而新技术只需要两个台站。从理论上研究了电磁脉冲在地面上有限的电导率对视传播延迟的影响，理论结果与观测结果的相似性证明了有限的地面电导率确实影响了定位精度。这些新成果发表在日本《电子工程学报》上。对一年半的数据分析揭示了热带地区闪电的以下特征。年变化的特点是雨季和旱季。大约从10月到4月，雨季期间几乎每天都有闪电活动。虽然爪哇岛的闪电密度比日本高一个数量级，但其闪电特征与日本的夏季并无太大差异。这种日变化在陆地和海洋上都存在，并且有所不同。这是首次揭示海洋-大陆地区闪电的这些特征，并将在1996年6月举行的国际大气电学会议上提出。