沙尘气溶胶的光学特性及辐射强迫效应

在采用OPAC折射指数资料库和对数分布的基础上,利用MIE散射理论和一个简单的概念模型研究了沙尘气溶胶的辐射特性及全球直接辐射强迫值,分析了单相系沙尘气溶胶的消光、散射、吸收效率因子与粒径的关系,讨论了多相系沙尘气溶胶的光学参数随波长的变化特征。结果表明,消光效率因子和散射效率因子随粒径增大而衰减振荡,随波长增大振荡特性逐渐消失。消光系数对众数半径的变化很敏感,单次散射反照率和非对称因子对众数半径的变化不敏感。沙尘气溶胶的直接辐射强迫受气溶胶的单次散射反照率影响很大,随着众数半径的增大,沙尘气溶胶的负的直接辐射强迫值在减小,正辐射强迫值在增大。

Optical Properties and Radiative Forcing Effect of Dust Aerosol

Based on OPAC refractive index database and lognormal distribution, the radiative properties of dust aerosols and global averaged direct radiative forcing are studied by using Mie theory and a simple concept model. The relationship between mode radius and extinction efficiency, scattering efficiency and absorbing efficiency of single dust aerosols are analyzed too. We also discuss the change of optical parameters of the dust aerosols with the wavelength. The result shows that extinction efficiency and scattering efficiency oscillate and decrease as the mode radius increases. However, the oscillation gradually disappears as the wavelength increases. Extinction coefficient is substantial sensitive to mode radius, while single scattering albedo and asymmetry factor are opposite. Single scattering albedo of dust aerosol can strongly influence on the globally averaged direct radiative forcing. With mode radius increases, the negative globally averaged direct radiative forcing decreases, but the positive radiative forcing increases.