Abstract:In order to study the effect of cloud saturation on thunderstorm electrification,a parameterization of non-inductive graupel-ice charge separation S91 based on the laboratory results of Saunders et al.(1991) is introduced into a three-dimensional dynamic-electrification coupled model.The effective liquid water content and environment temperature in S91 are replaced by cloud saturation,resulting in the deformation of S91.The evolution characteristics of non-inductive charge separation polarity,magnitude,charge structure and their relationship with ice crystal and graupel particle distributions produced by the deformation of S91 and original S91 in a typical storm before the first discharge are analyzed,respectively.The results indicate that the transfer charges per collision and the change rates of charge density adopted in these two parameters are the same,but difference of factors which determine the increase of graupel and ice particles in these schemes exerts a relatively important influence on the distribution of charge.In the deformation of S91 scheme,the domain polarity of non-inductive charge separation changes is basically positive,the charge structure switches from unipolar to tripole,and it tends to produce a positive dipole charge structure.In addition,the difference of charge distribution and charge separation changes in the schemes are caused by the difference of coincidence region between graupel and ice particles.