A simulative study of the influnce of electric processes on the content and the size distribution of graupel in a severe thunderstorm.

A threedimensional hailbin cloud model coupled with electrification process was developed and used for simulating influences of electric processes on water content and number density of graupel (considering the effect of electric fields on hydrometeors through electric field force) in a severe thunderstorm in Beijing City in China. The results show that: （1) The water content of relatively smallersize graupel is influenced more by the electric processes, which may later have an indirect effect on the content of relatively biggersize graupel. In the center areas of graupel content, the electric field is not maximum or minimum, whose influences on the graupel with largersize and the maximum graupel content ( QgMax) are relatively less. Therefore, little changes occur in the time evolution ofQ gMax. （2) On the whole, in the model domain, the influence of electric process on microphysical processes, which will influence the number density of graupel, is different in different regions; where the electric field is stronger, the influence of electric process on the graupel with smallersize is more direct than that with largersize. The influence of electric processes on the size distribution of graupel is less at areas where electric field is weaker. （3) In the process of formation and development of graupel, electric processes show no influence on the position of the maximum cloud water content, and the position has important influence on accretion of graupel. Therefore, the formation and distribution of graupel would not be highly influenced by electric processes. Although the size distribution of graupel changes a little, the position of the maximum graupel content does not change notably. Therefore, electric processes are able to influence the total quantity and the region of hail-fall, but not notably.