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, and lead to a sudden decrease in the maxima of electrostatic potential and potential gradient as well as consume of electrostatic energy of thundercloud. The ratio of induced charges to surrounding space charges varies from 0.2% to 70.8%, 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 10(7) similar to 10(10) J. (2) As contrasted with transient IC discharges, the charge neutralization in thundercloud is a slow process with a relaxation time of about one minute or less. The dispersed space charges in thundercloud and opposite charges deposited in the flash channels are mixed slowly and neutralized partially by turbulence exchanging, advection transporting and gravitational sedimentation etc.. There are 15% similar to 40% excess of induced channel charges to be not neutralized, which contributes to rebuilding new distribution of space charges and electrostatic potential.