Initial Streamer of the Cloud Discharge in Winter Thunderstorms of the Hokuriku Coast

Abstract

Assuming the initial streamer development of the cloud discharge be represented by the movement of a point charge with constant velocity, the parameters of the initial streamer, such as height of starting point, charge amount, direction and velocity of propagation, were determined by using the data of electric field-change measured simultaneously at three to seven stations. The following characteristics of the initial streamer of the cloud discharge were deduced from the analyses of thirteen discharges in the winter thunderstorms at the Hokuriku coast: (1) Cloud discharges originate in the region of the temperature from-6* to-10*, which is the same temperature range as that in the summer thunderclouds. (2) The electric charge carried by an initial streamer is about 30 to 130C, and the average value is 63C. (3) The direction of streamer progress is upward, and the zenith angle of the progress is less than 30*. (4) The streamer velocity is of the order of 104m/s, and depends on the altitude of its starting point.