A 3D Modeling Study on Multi-Layer Distribution and Formation Mechanism of Electrical Charging in a severe Thunderstorm

A three-dimensional hail-bin cloud model coupled with electrification process has been developed and used for simulating electrical charging and lightning processes in a severe thunderstorm in Beijing City in China. The results indicate that 1) the charge transfer between cloud droplets and graupel, and spatial distribution of charge density are primarily influenced by cloud water through inductive charging mechanism. However, when including rain water content the noninductive charging between graupel and snow (or ice) crystals in different liquid water content may have important influences on the distribution of charge density through influencing the polarity and quantity of charges. 2) Different microphysical processes may produce the inhomogeneous distribution of the source and sink of hydrometeors. It causes the inhomogeneous distribution of hydrometeors in different vertical cross-sections and leads to the complicated charge separation due to both inductive and non-inductive charging processes. At the same time, the charge transfer due to mass transfer of hydrometeors is not homogeneous. 3) Lightning flashes deposit charges of opposite polarity in channels after discharge. Different microphysical processes can complicate the distribution of charge density of hydrometeors by complicating the charge transfer in the processes of the mass transfer. The three factors mentioned above are main factors that lead to multi-layer charge structures.