Rapid Yet Accurate Radiative Transfer Algorithm for Remote Sensing
适用于遥感应用的辐射传输高精度快速计算方法

Energy conservation and accurate angular distribution of radiance are the basic requirements for simulation of radiative transfer processes.Current climate model and operational remote sensing technique demands fast and accurate radiative transfer algorithm.To improve the computational efficiency,the scattering phase function is expanded and truncated as the summation of orthogonal polynomials such as Legendre function.Based on mathematical theory,number of polynomials must agree with streams(number of grids in angular integration) to satisfy the integration conservation,inappropriate truncation of scattering phase function results in considerable errors,especially for strong forward scattering media such as cloud particles and dust aerosol in the atmosphere.The truncated scattering phase function of dust or cloud,which fluctuate with scattering angle,results in false fluctuation in angular distribution of radiance,the fluctuation could be removed through taking huge number terms in expansion of scattering phase function,but energy conservation is broken,radiation flux is wrong and the results are unstable.Based on mathematical and radiative transfer theory,the phenomenon of false fluctuation and the stability of radiative transfer algorithm are analyzed,several fast and accurate methods are compared.Finally,two fast and accurate algorithms,satisfying the energy conservation and using less streams,are given,which is of significance in remote sensing,parameterization of radiative forcing in global climate models,energy budget estimation of the earth-atmosphere system,in particular,the effect of clouds and dust events.