Fig. 1. Geometric diagram of slant-range visibility

Fig. 2. Schematic diagram of radiative transfer in multi-layer atmosphere

Fig. 3. Flow chart of solving high-resolution radiative transfer equation

Fig. 4. Atmospheric molecular and aerosol particle data. (a) Increment of optical depth; (b) single scattering albedo; (c) asymmetric factor; (d) pressure; (e) temperature; (f) water vapor density; (g) ozone density

Fig. 5. Spatial distribution of sky background radiance of different altitudes. (a) 0 km; (b) 1 km; (c) 3 km; (d) 10 km; (e) 20 km; (f) 50 km

Fig. 6. Variation trend of sky background radiance with altitude. (a) Downward observation; (b) upward observation

Fig. 7. Comparison of surface irradiance between MERRA-2 and SBDART model. (a) Trend comparison; (b) relative error; (c) correlation analysis

Fig. 8. Relative error distribution of sky background radiance. (a) Downward observation; (b) upward observation

Fig. 9. Variation trend of brightness contrast with slant range under different observation zenith angles. (a) Downward observation; (b) upward observation

Fig. 10. Distribution of slant-range visibility results using empirical expression and proposed method. (a) Spring; (b) summer; (c) autumn; (d) winter