Studies on Thunderstorm Electricity

I. Cloud Discharge

Abstract

To study the electrical process in cloud discharge and the charge distribution in thunderclouds, the electrostatic field changes due to a cloud discharge have been recorded simultaneously at three field sites. It has been found that there are three types of thundercloud: Type I predominantly produces an upper-positive vertical dipole discharge, Type II an inclined or horizontal discharge, Type III an upper-negative vertical discharge. Type III is found likely to have more or less thin distribution of negative electric charge on top of or just above it. The streamer velocity ranges mostly in 1-2×10⁶cm/sec, and is neary kept constant through out the whole duration of a discharge. The path length of a vertical discharge is usually of 2km or less, while that of a horizontal one is mostly longer than this value. The electric charge quantity neutralized in a cloud discharge often exceeds 100 coulombs, which is in a good agreement with Hatakeyama's report, while it is appreciably larger than the value presented in other reports. A cloud discharge consists of many local discharges being distributed on its path at 200m interval in average. The charge dissipated by a local discharge is estimated to be of about 1 coulomb or more.