Charge transfer in convective thunderclouds induced by molecular interface crossing and free energy reduction

In spite of many experiments showing that charge is transferred during collisions of cloud particles, the precise mechanism of the charge separation and its effect on the spatial charge distribution in thunderclouds is not yet understood. Collision processes between two cloud particles could be treated as composed of three phases: before contact, contact and withdrawal. Interfacial mass and charge transfer between proximal and contacting water or ice surfaces depends on the balance of competing intermolecular interactions at the interfaces. This paper attempts to demonstrate how the Free Energy Reduction by Molecular Interface Crossing (FERMIC) model could be complementarily applied and fully implemented into existing concepts to interpret complex atmospheric charge transfer processes, offering a novel qualitative physical explanation to the experimental results of charge separation in thunderclouds assumed to occur before contact. The FERMIC process has been extensively applied to the understanding of the transfer of mass or charge across liquid interfaces, self-organized molecular assembly in physical and biological processes and in the development of biomaterials. However, it was never used to explain the interfacial mass and charge transfer processes occurring during collisions of hydrometeors in thunderclouds where strong electrification and lightning are common. (C) 2001 Elsevier Science B.V. All rights reserved.