A Simulation of the Effects of Intra‐Cloud Lightning Discharges on the Charges and Electrostatic Potential Distributions in a Thundercloud

This paper extends the use of Stochastic Lightning Model in a simulation experiment, in which 12.5 and 250 m resolution simulations of intra-cloud (IC) lightning discharges within a two dimensional numerical thunderstorm model have been performed, and gives the comparing analyses of the simulated results with the observed data. The results show: (1) During an IC flash discharge, more complex distribution of the space charges in thundercloud is caused by the induced charges along the channels, leading to a sudden decrease in the maxima of electrostatic potential and potential gradient as well as consume of electrostatic energy of thundercloud. The electrostatic potential and field strength drop down respectively to ±30 MV and ±20 kV·m−1 where the flash channels passed, and consumed electrostatic energy of thunderstorm for a positive or negative IC flash is about 107 ~ 1010 J. (2) As contrasted with transient IC discharges, the charge neutralization in thundercloud is a slow process with a relaxation time of about 14~40 secs. The relaxation time is confirmed by turbulence exchanging, advection transporting and gravitational sedimentation, during which the induced charge along leader channels drops down to 50%. There are some excess of induced channel charges to be not neutralized, which contributes to rebuilding new distribution of space charges and electrostatic potential.