The Electrical Shielding Layer Around Charged Clouds and its Role in Thunderstorm Electricity

Abstract

The system of differential equations which governs the equilibrium charge distribution around a charged cloud located in an atmosphere with constant ionization is solved numerically for clouds with differing water content. The equations include the effects of ionic recombination, and the ionic conduction currents to cloud droplets. The results show that the electric field external to the cloud is greatly reduced by a shielding charge distribution which first develops at the clear air-cloud boundary and then slowly moves inward toward the charge center. If ions are generated locally within the cloud, they produce an inner region of charged droplets of opposite polarity to the outer screening layer. An increased electric field maximum will exist between the regions of charge. The effects of turbulence and electroconvection within boundary layers and the time-dependence of the shielding layer charging with and without turbulent transport are discussed. The role of the shielding charge in determining the electric field recovery time following lightning discharges is specified and the ionic concentration and electrical conductivity within thunderstorms is considered.