[A-AS07] Extreme weathers and disasters in urban environments in East Asia and relationship to climate change

[AAS07-05] An estimation of neutralizing charge over a surface in thunderstorm with lightning

*Yumiko Yamashita¹, Atsushi Nagao¹, Naomichi Nakamura¹, Toshishisa Masuda¹, Takashi Ikeda¹, Yousuke Sato², Masaru Inatsu², Mitsuteru Sato² (1.NTT Space Environment and Energy Laboratory, 2.Faculty of Science, Hokkaido University)

Keywords:Lightning, Electric field mill, inverse problem

To protect our society(e.g. damage to infrastructure[Nakamura et al., 2018])) from lightning strikes, highly accurate predicting a point and time of outbreak of lightning and deploying the protectors near the point would be useful to protect us from lightning threats(e.g. [Nakamura et al., 2018]). Therefore, we pay attention to a new lightning prediction system having better accuracy with microscope variable not be hardly used the existing short-term prediction systems(e.g. lightning cast[Kasahara, 2011], TITAN[Dixon and Wiener, 1993]) as input data. To connect to modeling the time development of the charge distribution which is one of microscope variables with the electric field data, we try to estimate multi-dimensional neutralizing charge. In this study, we demonstrate identifying the domain in the neutralizing phenomenon that occurs with two-dimensional before three-dimensional in a thundercloud when lightning occurs. The data of electric field on the ground have been used and estimation of neutralizing with lightning strikes, under two assumptions that the ground surface is a perfect conductor and that the charge distribution of each layer in a thundercloud with a tripolar structure is zero-dimensional[Jacobson and Krider, 1976]. In addition, there are few studies of the three-dimensional extension of an estimation of neutralizing charge. The our extension of estimation method is based on approximating a continuous charge distribution to a finite number of point charge and principle of superposition of electric fields. Although we need additional conditions or algorithms if number of point charges is larger than that of electric field mills, we decided the same numbers of field mills and point charges for the demonstration. An electric field mills was installed at four sites in Gunma, Japan: Takasaki City, Shibukawa City, Kiryu City, and Ota City. Electric fields is measured every 1/20 seconds and We calculated a two-dimensional neutralizing charge with a lightning occurrence and its time is Jun 28, 14:32:45.50(JST). The numerical calculation that we conducted enabled us to identify the area where the neutralizing phenomenon occurred. We also considered more effective algorithms with two-dimensional estimation, in order to archive extending the three-dimensional neutralizing estimation in a thundercloud. (2013 letters)