Monte Carlo methods for numerical simulation of solar energy radiation transfer in crystal clouds

The paper deals with numerical models related to radiation transfer in ice clouds. A mathematical model of crystal particles of irregular shape and an algorithm for modeling such particles based on constructing a convex hull of a set of random points are considered. Two approaches to simulating radiation transfer in optically anisotropic clouds are studied. One approach uses pre-calculated scattering phase functions for crystals of various shapes and orientations. In the other approach, no knowledge of the phase functions is required; the radiation scattering angle is modeled directly in the interaction of a photon with crystal faces. This approach makes it possible to simply adjust the input parameters of the problem to changing microphysical characteristics of the environment, including shape, orientation, transparency of particles and roughness of their boundaries, and does not require time-consuming preliminary calculations. The impact of flutter on radiation transfer by a cloud layer and angular distributions of reflected and transmitted radiation are studied.