Monitoring of lightning activity based on simultaneous measurement of electric field and electric field-change in the Tokyo metropolitan area

Main objective of this study is nowcast of thunderstorm activity that causes extreme weather, such as torrential rain, based on lightning observation. Lightning observation has been focused on as an effective way for nowcast of thunderstorm activity. Spatial distribution of lightning discharge has been used as a proxy of the presence or absence of deep convection, which generates thunderstorm. We have constructed sensor network for lightning observation in the Tokyo metropolitan area, Japan, since 2013. In this network, VLF sensors (frequency range is 1 - 40 kHz) to measure electric field radiated from lightning discharges are distributed about 100 km apart. Additionally, slow antenna and electric field mill are also installed to detect electric field-change by lightning discharge. In this study, evaluations of not only spatial distribution but also scale distribution of lightning activity have been examined based on simultaneous measurement of electric field and electric field-change. As a scale of lightning discharge, charge moment change is derived. Preceding observation shows that there is extremely huge lightning whose scale is more than hundreds times bigger than that of averaged event. Estimation of scale for each lightning discharge would makes it possible to evaluate not only existence but also strength of atmospheric convection in thunderstorm area quantitatively. Based on lighting observation in the Tokyo metropolitan area, we start to construct new sensor network for real-time monitoring of lightning activity from this year. VLF sensors, slow antenna and electric field mill are mounted on real-time weather observation system named POTEKA developed by Meisei Electric Co., Ltd. and will be distributed in Metro Manila, Philippines under the 5-year project (SATREPS). At the presentation, observation in the Tokyo metropolitan area are summarized as a prototype for lightning observation that will be carried out in Metro Manila, Philippines.