Study on the mechanism and prediction of lightning flashes in winter with large peak currents and energies

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K03681
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17030:Human geosciences-related
• Research Institution: Gifu University
• Principal Investigator: Wu Ting 岐阜大学, 工学部, 准教授 (50789774)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 冬季雷 / 雷三次元観測 / 落雷被害

Outline of Final Research Achievements

During this project, using the three-dimensional lightning mapping system FALMA, we carried out observations of lightning flashes with large peak currents and energies that frequently occur along the coast of the Japan Sea. The main achievements are as follows. (1) For the first time we clarified the basic characteristics of strong negative strokes with peak currents larger than 150 kA and elucidated their clear differences with normal negative strokes. (2) We made a statistical analysis of peak currents of positive strokes and established their relationship with characteristics of preliminary breakdown and stepped leaders. (3) We developed a machine-learning method for the classification of lightning return strokes with high accuracy, which is the basis for large-scale statistical analyses such as the comparison of lightning strokes in winter and summer.

Free Research Field

大気電気

Academic Significance and Societal Importance of the Research Achievements

日本海沿岸には、夏季ではめったに発生しない巨大なピーク電流を持つ落雷がしばしば起きる。このような巨大落雷は送電鉄塔や大型風車等の施設に大きな被害をもたらしている。本研究では、負極性と正極性両方の巨大落雷の特徴を解明した。特に今まで知られていない負極性の巨大落雷の特徴を初めて明らかにした。負極性巨大落雷は沿岸部の陸地に集中する傾向も判明したので、大型風車等の施設の落雷被害の主な原因になっている可能性が高い。また、正極性落雷のピーク電流値は雷撃の前駆放電過程との関連性を明らかにした。強いピーク電流を持つ正極性落雷を発生する雷雲の電荷構造も判明した。これらの成果は巨大落雷を予測する可能性を示した。