Cloud electrification by fracture in ice-ice collisions: a 3D model

A study to evaluate the electrification caused by only one kind of noninductive mechanism, namely ice-ice collisions with fractures is presented. Its ability to reproduce the most important features of cloud electrification is discussed. The study is carried out numerically and use is made of recent laboratory data. The model has the dynamical and electrical developments uncoupled. The particle spectrum is discrete with eight categories and the fragments increase the number of only the smallest of them. It is shown that high fields (250 kV/m) are produced by fracture charging in times of about 3 min. It is also found that positive and negative charge distributions overlap considerably and their superposition results in a highly stable stratification forming a vertical tripole structure. The charge on individual particles so obtained are in good accord with the experimental data reported by airborne in situ measurements.