The Numerical Simulation Research On The Effect Of The Inductive Charging On The Electrification Of Thunderstorms And Lightning Characteristic

A two-dimensional cloud model with electrification and lightning processes is used to investigate the role of inductive charge separation in thunderstorm clouds.By varying the collision coefficient of graupel-cloud droplets to represent the strength of inductive intensity.For the same dynamic and microphysical evolution,four cases that the same non-inductive charging parameterization is combined with different inductive charging process are compared:only including non-inductive process;including non-inductive process,the inductive process operates between graupel and cloud droplets;considering non-inductive process and the inductive process between graupel and ice crystals;all three processes applied.Each of them focuses on the same micro-physical process,then discusses the difference in electrification process and discharge characteristics and puts up corresponding physical basis,and also performs certain quamntitative analysis to make the simulation result more accurate.By simulation,we obtain an important role of the inductive charge separation process in the electrification process.It provides a better experimental background and improves the existing research results,which makes a new reference for the follow-up research on the lightning mechanism of thunderstorm cloud.This article gets the following main conclusions:(1)The difference of inductive intensity does not change the charge distribution in the early stage of development and maturity of thunderstorm clouds.A small negative charge region is embedded in the lower part of the structure based on the tripolar charge structure.This is due to the strong updraft in the thunderstorm cloud in the previous period,the thunderstorm cloud developed rapidly.The graupel particles developed more rapidly at that moment.After the graupel particles increased,they continued to settle and formed solid precipitation.Since the graupel particles were negatively charged,a weak negative charge zone appeared under the positive charge zone of the bottom,and since then,a weak negative charge zone appeared.After the particles settled,the negative charge area gradually disappeared,returning to the previous tripolar charge structure.With the increase of the induction intensity,the total nuber of flashes was not changed,but the cloud discharge time was advanced in the later period.(2)Non-inductive charge separation alone is found to be sufficient to produce a dipolar charge structure.IC and positive cloud-to-ground(+CG)flashes are initiated between a main negative charge region and a upper positive charge region.The inductive charging process between graupel and cloud exhibits a normal tripole charge structure,consisting of a lower positive charge region under the main negative charge region.In the simulated tripole-structure,negative cloud-to-ground(-CG)flashes are initiated between the main negative and lower positive charge regions.In addition,inductive charge separation between the graupel and ice crystal is found to be capable of producing strong charge separation in a dipole charge structure.Tests with inductive graupel-ice crystal process produce more flashes than that in the other cases.