Low-parametrical approximation of reflectance in a gas absorption band

The sunlight transfer equation problem in a gas absorption band is under consideration. Structure of spectral dependence of reflectance of solar light reflecting by the atmosphere-surface system is studied. Low-parametrical approximations of reflectance as expansion of reflectance inverse logarithm by absorption section degrees are constructed. The approximation are synthesis of the Bouguer–Lambert–Beer law. The explicit algorithm of approximation parameters calculation based on known values of reflectance. It is shown how the constructed approximations can be used for reduction of time of line-byline calculations of reflectance.