A numerical simualtion on a thunderstorm in Chongqing and its response to changes in initial number concentration of cloud droplets
In this paper,RAMS (Regional Atmospheric Modeling System) model,coupled with two non-inductive charging parameterization schemes (Saunders and Takahashi schemes),is adopted to stimulate a thunderstorm occurred in Chongqing.A comparative analysis of two schemes is presented on the distribution of hydrometeor particles,the charge density and the distribution of charge structure in the thunderstorm when the charges start to separate and the thunderstorm reaches its maturity.Simulation results show that a dipole characteristic is presented from electrifying to discharging in the charge structure with Saunders scheme,while the characteristic in the charge structure switches from inverse dipole to positive dipole with Takahashi scheme.To study the impact of CCN (cloud condensation nuclei) on the thunderstorm,two sets of sensitivity tests have been carried out.As the initial number concentration of cloud droplets increase,no polarity conversion occurs in the charge structure,however,in the thunderstorm,the charge amount increases and the distribution area of charge expands,which is conductive to the occurrence of lightning.With Saunders scheme,the amount of charge decreases when the initial number concentration of cloud droplets is over 2 000 cm-3.Through analysis of the microphysical field and microphysical process,it is found that the mass mixing ratio of ice-phase particles increases as the initial number concentration of cloud droplets increases,while the mass mixing ratio of graupel particles decreases when the initial number concentration of cloud droplets is over 2 000 cm-3,with Saunders scheme.This verifies the impact of CCN variation on the microphysical process,thus further on the distribution of charge in the thuderstorm and the occurrence of lightning,especially the impact of variation of ice-phase materials on the electrification process of thuderstorm.
RAMS modelnon-inductive charging parameterization schemecharge structureinitial number concentration of cloud droplets
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维普
