[M-IS09] Effects of lightning, severe weather and tropical storms

[MIS09-03] Time variation of the lightning activities in typhoon clouds and its relation to the typhoon intensity development

*佐藤 光輝¹、高橋 幸弘¹、久保田 尚之¹、Lopez Glenn Vincent² (1.北海道大学 大学院理学研究院、2.フィリピン科学技術省 先端科学技術研究所)

キーワード：雷活動、台風、直前予測

Many countries in the western north Pacific suffer from the attack of typhoons and have a strong demand not only to predict the typhoon track but also to rapidly and accurately predict the typhoon intensity development in order to prevent the typhoon disasters. Recent studies revealed that the lightning occurrence number in tropical cyclones (TCs) shows clear relation to the intensity development of TCs. Thus, the final goal of our study is to establish a method to empirically predict typhoon intensity development using lightning data. For this purpose, we constructed the lightning observation network in the western north Pacific and conducted the cross-correlation analysis between lightning activity monitored by this network and typhoon intensity development. First, we developed a new automatic weather and lightning observation system (V-POTEKA) and deployed this system in the Philippines, Guam, Palau, Jakarta, Okinawa since September 2017. V-POTEKA equips a VLF receiver, which can detect the electromagnetic waves in the frequency range of 1-50 kHz radiated by lightning discharges. Then, lightning locations can be estimated using V-POTEKA data and using the time-of-arrival geolocation algorithm. Finally, we compared the relation between the lightning activity within the typhoon area and the intensity development of the western north Pacific typhoons in the period of 2018-2020. In this study, typhoon track and intensity data provided by Japan Meteorological Agency (JMA) and Joint Typhoon Warning Center (JTWC) are used, and a total of 48 of 81 typhoons are selected for the cross-correlation analysis. It is confirmed that the time variations of the detected lightning event numbers and typhoon intensities (maximum wind speed (Vmax) and minimum pressure (Pmin)) are correlated (R=0.55 for Vmax and R=0.57 for Pmin) and that there is a clear time lag between lightning activities and typhoon intensities (+39 h for Vmax and +36 h for Pmin), which means the peak of lightning activity comes first and the peak of the typhoon intensity comes next. It is also found that the time lag in the weaker typhoons is smaller than that in the stronger typhoons and that the detected lightning density (events/day) in the weaker typhoon is larger than that in the stronger typhoons. At the presentation, we will show the results derived from this cross-correlation analysis in detail and discuss the possible physical mechanism for these relations.