针对含粒子参与性介质内红外辐射传输与光谱特性开展了数值方法研究.推导了辐射传输方程的球谐函数(PN -Approximation)分解形式，建立了求解非线性各向异性散射介质内红外传输的任意阶PN方法.基于辐射—导热耦合换热模型，通过已有理论解验证了高阶PN方法的计算精度.经验证，对于非线性各向异性散射问题，文章建立的任意阶PN方法的计算精度非常高，对高阶散射相函数处理地十分简便，该方法对含气溶胶大气的红外传输问题计算非常适合.最后计算了2~5 μm含气溶胶大气红外辐射传输特性，研究了各向异性散射对大气红外传输特性的影响.研究结果表明： 非线性各向异性散射对于大气红外光谱辐射强度起到了削弱作用；同时对于强吸收谱带，散射也会削弱方向辐射强度.

A numerical method, used for infrared radiative transmission and spectrum characteristics in participating medium with particles, was developed in this paper. Decomposition form of radiative transfer equation was deduced using spherical harmonics (PN-Approximation) method. Arbitrary order PN-Approximation method for solving infrared transmission in nonlinear anisotropic scattering medium was established. Based on the coupled radiation and conduction model, the calculation accuracy of high-order PN-Approximation method was verified through comparison with theoretical solution. Compassion shows that the arbitrary order PN-Approximation method established in this paper has a high accuracy, and it can easily treat the nonlinear anisotropic scattering phase functions with high order. Therefore, this method is very suitable for solving the problem of atmospheric infrared transmission. Atmospheric transmission characteristics with aerosols in the spectrum band ranging from 2μm to 5μm were calculated, and the influence of anisotropic scattering on atmospheric infrared transmission characteristics was studied. The results show that nonlinear anisotropic scattering can reduce both the atmospheric infrared spectral radiation intensity and the direction radiation intensity in strong absorptive bands.