Warm Cloud Electricity in a Shallow Axisyminetric Cloud Model

Abstract

An axisymmetric warm cloud model (Takahashi, 1975b), modified in both the calculation scheme and diffusion term, is used to investigate the development of electricity in a warm cloud. The study focuses on four electric charge separation mechanisms: 1) the ion-drop interaction under an electric field; 2) the competitional attachment of small ions to drops by the mobility difference between positive and negative small ions; 3) the polarization effect when drops collide and rebound under an electric field., and 4) the ion-drop interaction during drop condensation and evaporation. Comparison with observed data supports the conclusion that ion-drop interaction during drop condensation and evaporation is the major electric charge separation mechanism in warm clouds. The investigation stresses the importance of drizzle and raindrop formation near the cloud top for both the development of rain and electric charge separation.