Simulation and Analysis of Sky Background Radiance in Slant Visibility Calculation

In this paper, based on the principle of slant visibility detection, the SHDART (Santa Barbara DISORT Atmospheric Radiative Transfer) model is used to solve the radiation transfer equation, and detailed theoretical simulation and analysis of the sky background radiation arc carried out. First, using the aerosol models from SHDART model, the sky background radiation results of different types of aerosol models under sunny conditions arc obtained. The distribution trends of solar direct radiation and atmospheric scattering radiation at different heights arc discussed. The influences of single scattering radiation albedo and asymmetry factor on the results arc analyzed. A calculation method combined with Lidar and SHDART model is presented to obtain the real sky background radiation. The aerosol data obtained by a scanning lidar is taken as the input parameter of SHDART model, and the distribution results of solar direct radiation in the real atmosphere and sky background radiation at different heights arc calculated. In order to validate the correctness of the results, the solar direct radiation synchronously measured by the solar photometer is compared and verified. The results show that a consistent change trend can be obtained between them, showing positive correlation with a correlation coefficient of 0.99. Finally, taking blackbody as the target, the influence of sky background radiation on slant visibility is preliminarily discussed. The actual sky background radiation obtained by combining Lidar and SHDART models can provide guarantee for accurate inversion of slant visibility.