Construction of an Electrostatic Sensor Network to Estimate Total Charge in an Isolated Thundercloud

This paper presents a methodology to estimate the quantity and location of charges in an isolated cloud based on multipoint measurements of electrostatic fields on the ground. We have newly designed and fabricated an electric field mill (EFM) and constructed an EFM network in Tochigi and Gunma prefectures, Japan. It is difficult to understand the relationship between variations of surface electrostatic field and charge distribution in the cloud. In our observation, a single cell thundercloud is focused on to assume a simple charge model inside the cloud and to simplify the calculation of the quantity and height of the point charge in the cloud. In this paper, by assuming a point charge model in the cloud, amount and height of charge in an isolated storm is estimated as an initial result. We also summarize details of the developed sensor system and the method of calibration for sensors in our EFM network.