Comparison,Correction And Application Of Different Radiative Transfer Models On Atmospheric Scattered Radiance

As an important parameter of atmospheric optical properties,atmospheric scattered radiance has important scientific research significance and engineering application value in the fields of atmospheric composition detection,space target recognition and aviation safety.At present,the results of atmospheric scattered radiance can be simulated accurately and quickly by using the radiative transfer model.However,there are differences in the simulation results of atmospheric scattered radiance by different geometric approximation models.Especially,in the accurate measurement of daytime slant visibility,the atmospheric scattered radiance will directly affect the measurement results of slant visibility.In this paper,the atmospheric scattered radiance is taken as the research object,and the SBDART radiative transfer model of the parallel plane atmospheric model and the libRadtran radiative transfer model of the pseudospherical atmospheric model are used as the means to carry out for the comparisons of the atmospheric scattered radiance and mutual correction from different radiative transfer models.The corrected atmospheric scattered radiance results are further applied to the measurements of the slant visibility.The specific work is as follows:Firstly,based on the radiative transfer equation and its solution theory,the simulation of atmospheric scattered radiance by SBDART model and libRadtran model is carried out.The built-in parameters and input options of solar spectrum,standard atmosphere model and aerosol model are unified.Through the setting of aerosol optical parameters and cloud parameters,the atmospheric scattered radiance under sunny and cloudy weather conditions was simulated by two models.The distribution of atmospheric scattered radiance at different layers,the atmospheric scattered radiance at different directions,and the output results of the solar direct and diffuse irradiance reaching the ground were compared respectively.The comparison and analysis results show that,the simulated atmospheric scattered radiance by SBDART model is higher than that by libRadtran model in the direction of large observation zenith angles,which reflects the necessity of the correction of SBMART model in the direction of large observation zenith angles.Furthermore,the correction method of atmospheric scattered radiance is carried out.Based on the difference between the parallel plane and the pseudo-spherical radiative transfer equation,a pseudo-spherical atmospheric correction method based on libRadtran is proposed.The Chapman correction function is introduced,and the atmospheric correction coefficient C and atmospheric correction process are simulated by combining the atmospheric aerosol extinction coefficient and atmospheric transmittance.On this basis,under different weather conditions,the Chapman function is used to correct the atmospheric scattered radiance simulated by the SBDART model in the direction of larger observation zenith angle.The simulation results show that,in the direction of large zenith angle,the corrected radiance of the SBDART model is consistent with that of the libRadtran model.After correction,the deviation is reduced from 24.5 W/m2/μm/sr to about 13.7 W/m2/μm/sr under clear conditions,and reduced from 21 W/m2/μm/sr to about 9.5 W/m2/μm/sr at cloud height,which verifies the correctness and effectiveness of the pseudo-spherical correction method.Finally,based on the simulation of the correction method and the established slant visibility lidar system in Xi’an University of Technology Laser Radar Remote Sensing Center,the atmospheric scattered radiance under actual atmospheric conditions is corrected and applied to the measurement of slant visibility.The results show that,under clear condition,the slant visibility is 9.88 km and 11.49 km before and after the correction of atmospheric scattered radiance;under cloudy weather condition,the slant visibility by scattered radiance correction is extended from 4.17 km to 5.03 km.Thus,the measurement distance of slant visibility can be improved by the pseudo-spherical correction method,and the error caused by the parallel plane atmospheric radiative transfer model can be reduced to a certain extent.