Monte Carlo Model For Lightning Radiative Transfer Simulation

Monte Carlo method, also called statistical simulation method, is a very important numerical calculation method, based on the probability statistical theory, which was proposed as the development of the science and technology and the invention of computer in the middle of the 1940's. It uses random numbers (or more common pseudo-random numbers) to solve many computing problems. The method avoids mathematical difficulties of the structural reliability analysis, regardless of the state function non-linear, or the random variable non-normal, as long as simulation times enough, by which we can get more precise failure probability and reliability. In recent years, the mathematical method for lightning radiative transfer calculations is Monte Carlo method.Using Monte Carlo method for radiative transfer calculations, finding approximate solution through statistical experiments of the random variables, has the following two characteristics: (1) Monte Carlo method is not restricted by plane stratified atmosphere, it can not only solve the plane non-uniform problem, but also the spherical atmosphere problems; (2) Monte Carlo method has no need to solve the radiative transfer equation, but rather simulate radiation transmission processes in the atmosphere. It observes the scattering, absorption, occurs when the photons transport in the atmosphere one by one, calculates the final radiation intensity distribution, which the lightning should be.This article treats the thunderstorm clouds as nuclear reactor, simplifies the lightning source as a point source, considers the cloud model as three-dimensional uniform water cloud. A photon incidents at an angle from the upper atmosphere, after some distance, it will be collided by the cloud particles, and be absorbed or scattered to some directions at a certain probability, and then the second, the third collision,…the Nth collision takes place, until speed reduced to zero or escape from the cloud. After each collision, the direction of the photon scattering (θ,φ) is also a random variable, and related the phase function p (Θ). Finally, the model gets the radiation intensity distribution for a given cloud model cloud-7 and the relevant external environment. And the result agrees with William J. Koshak, Richard J. Solakiewicz's diffusion model nearly.