Approximate model for calculating radiance of atmospheric background

Spectral intensity of atmospheric background radiance plays an important part in effects during Earth-sensing and measuring, for example flood monitoring, resource remote sensing, earthquake forecasting, monitoring of forest fire, etc. An approximate model for calculating atmospheric radiance was developed with Radiative Transfer theory based on transmission of energy. In this model, atmospheric radiance is divided into four sections: (1) single scattering radiance process of solar radiance by atmosphere particulates; (2) multiple scattering radiance of solar radiation by atmosphere particulates; (3) infrared thermal emission of the path atmosphere; (4) reflected radiance by the Earth's surface. Computing methods are analyzed deeply, and their analytical expresses are given out, respectively. Particularly, effect of reflection of the Earth's surface on atmospheric radiance is thoroughly studied and derived. Finally, atmospheric spectral radiance was calculated for some representatively meteorologic states. The results show that atmospheric background radiance is mainly composed with scattered radiance of solar radiation by atmospheric particulates while wavelength is less than 3μm, and with infrared thermal radiance of path atmosphere and effect of the Earth's surface on atmospheric radiance may be neglectable while wavelength is more than 3 μm.