日本地球惑星科学連合2019年大会

講演情報

[E] ポスター発表

セッション記号 M (領域外・複数領域) » M-IS ジョイント

[M-IS05] New technologies to monitor thunderstorm and severe weather activities

2019年5月28日(火) 10:45 〜 12:15 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:佐藤 光輝(北海道大学 大学院理学研究院)、高橋 幸弘(北海道大学・大学院理学院・宇宙理学専攻)、久保田 尚之(北海道大学)、山下 幸三(足利大学工学部)

[MIS05-P03] A method for locating lightning discharges using tweek atmospherics

*菅野 将史1大矢 浩代2塩川 和夫3中田 裕之2鷹野 敏明2 (1.千葉大学大学院融合理工学府、2.千葉大学大学院工学研究科、3.名古屋大学宇宙地球環境研究所)

Locating accuracy for lightning discharges of world-wide lightning location (WWLLN) is high to be less than 10 km [Rodger et al., 2005], although the accuracy of horizontal propagation distance for tweek atmospherics is low to be ~60 km [Santolik and Kolmasova, 2017]. Tweek atmospherics are very low frequency (VLF)/extremely low frequency (ELF) waves radiated from lightning discharges, and propagate between the Earth surface and the bottom of the ionosphere for a long distance (several thousand kilometers). In this study, we improve the estimation method for the tweek propagation distance, and compare between the lightning location estimated from tweek propagation distance by intersection method with those from the WWLLN data and cloud images derived by the MTSAT-2 satellite. We used two wideband VLF data observed at Kagoshima (31.48°N, 130.72°E) and Moshiri (44.37°N, 142.27°E), Japan, at 12:20-12:22 UT, on 23 August, 2013. The main point of the improvement was modification for the width of window on dynamic spectra drawn by maximum entropy method. The accuracy of the estimation became higher and the error for the propagation distance became the half of the original estimation, by using narrow window for the beginning, and wide window for the end of the tweek signals. We estimated the lightning location by both automatic and manual methods. In the manual method, the estimated location of lightning for the two-minute data was in good agreement with thick clouds observed by the MTSAT-2 satellite. However, in the automatic method, the location of the lightning was in disagreement with cloud images, because the accuracy of triggered times were not sufficient due to overlapping tweeks or noises such like short pulses just before the tweeks. In the presentation, we discuss the estimation method for the lightning location in detail.