两种按比例混合颗粒系的多次散射模拟

摘要

一种颗粒与其他种类的颗粒混合后,会使其散射特性发生变化,本文研究了水云中混有黑炭气溶胶后的散射特性变化.根据Mie理论计算了水云和黑炭气溶胶散射相函数、单次散射反照率和不对称因子.给出了混合颗粒系的蒙特卡罗模拟方法,给出了颗粒碰撞类型抽样、自由程抽样和根据Mie相函数进行散射方向抽样的方法.计算了光垂直入射时,水云和黑炭气溶胶混合颗粒系的反射光强随观测角的变化,并计算了平面反照率随入射角的变化,讨论了黑炭气溶胶的有效半径、混合比例对整个混合颗粒系散射特性的影响.计算结果表明,水云中混合黑炭会加强其吸收,且黑炭的比例和尺寸不同其散射特性差异较大.%If particles are mixed with other type of particles,the light scattering characteristics will be changed.In this paper,the light scattering characteristics of water clouds mixed with black carbon are studied.Based on the Mie theory,the single scattering phase function,the single scattering albedo and the asymmetric parameters of water clouds and black carbon aerosols are computed.The Monte Carlo method for simulating the scattering of mixed particles is given,the methods of sampling particle types,sampling free path length,and the sampling scattering directions based on the Mie phase function are given.The changes of the scattering characteristics for water clouds mixed with black carbon aerosols are studied.Reflected light intensity varying with observation angle is calculated with the light normal incidence,and the plane albedo is computed as a function of incidence angle.The influences of mixing ratio and effective radius of black carbon on the scattering characteristic of mixture are discussed.The results show that the black carbon can greatly increase the absorption of the clouds,and the ratio and the size of black aerosols can greatly affect the scattering characteristics of the mixture.