[M-IS13] Atmospheric electricity: Application of technology for reducing disaster risks

[MIS13-P06] A study of prediction method for lightning strike locations by statistical analysis of cloud particles and lightning discharge paths in summer thunderstorm

*YAMACHI ATSUYA¹, Hiroshi Kikuchi¹, Yasuhide Hobara¹, Eiichi Yoshikawa², Yoshitaka Nakamura³, Tomoo Ushio⁴ (1.The University of Electro Communications, 2.Japan Aerospace Exploration Agency, 3.Kobe City College of Technology, 4.University of Osaka)

Keywords:weather radar, lightning discharge

Severe phenomena such as torrential rain and lightning strikes are increasing, and severe phenomena are mainly caused by cumulonimbus clouds that develop locally and suddenly. The X-band meteorological dual polarization phased array radar (MP-PAWR) was developed for the purpose of observing cumulonimbus clouds that develop locally and over a short period of time. MP-PAWR enables high-frequency, high-precision observations, and is expected to provide detailed observations of cumulonimbus clouds. In addition, research is underway to use observation data of lightning discharges to predict severe phenomena, and the University of Electro-Communications and JAXA have begun observations using LF band three-dimensional lightning location equipment in the Kanto region in 2020. Lightning discharges are often associated with the internal structure and polarization parameters of rain clouds, and have been considered important indicators for predicting lightning strikes and heavy rain. However, there have been few cases in which high-temporal resolution and high-density three-dimensional analyzes have been performed simultaneously, and the relationship between intracloud precipitation particles and lightning discharge paths is not clear.
In this study, we performed a spatiotemporal comparison of polarization parameters obtained by MPPAWR and lightning location results, and discussed the relationship between polarization data and discharge paths. The polarization parameters used are the polarization phase difference rate of change (KDP) and the radar reflection factor difference (ZDR). KDP shows the particle size distribution, and ZDR shows different values depending on the shape and degree of mixing of precipitation particles. Simultaneous 3D analysis was performed based on these cloud particle distributions and 3D lightning location results. Two types of case studies, lightning strikes and cloud discharges, were analyzed, and the vertical and horizontal distributions of the results were shown. As a result, the relationship between KDP and lightning discharge shows that lightning discharge develops in areas where the flatness of raindrops of 0 to 2 degrees/km is small and where raindrops are relatively less concentrated. Furthermore, in the relationship between ZDR and lightning discharge, we were able to obtain a characteristic in which the degree of oblateness progresses to a region close to 0. Regarding the spatiotemporal frequency of lightning discharges, it was confirmed that they occur frequently during the maturation and decline stages of cumulonimbus clouds. This suggests that the complication of charge distribution within cumulonimbus clouds due to strong downdrafts may be related to increases and decreases in lightning discharges. In the future, we plan to further investigate the characteristics of lightning discharge paths by increasing the number of analysis targets and performing analysis in conjunction with cloud particle discrimination.