Atmospheric Chemistry and Physics

Abstract. The evolution of two-dimensional drop distribu-tions is simulated in this study using a Monte Carlo method. The stochastic algorithm of Gillespie (1976) for chemical re-actions in the formulation proposed by Laurenzi et al. (2002) was used to simulate the kinetic behavior of the drop popula-tion. Within this framework, species are defined as droplets of specific size and aerosol composition. The performance of the algorithm was checked by a comparison with the analyti-cal solutions found by Lushnikov (1975) and Golovin (1963) and with finite difference solutions of the two-component ki-netic collection equation obtained for the Golovin (sum) and hydrodynamic kernels. Very good agreement was observed between the Monte Carlo simulations and the analytical and numerical solutions. A simulation for realistic initial condi-tions is presented for the hydrodynamic kernel. As expected, the aerosol mass is shifted from small to large particles due to collection process. This algorithm could be extended to incorporate various properties of clouds such several crystals habits, different types of soluble CCN, particle charging and drop breakup.