Based on the 6S code, an improved model of the surface BRDF-atmospheric cou
pled radiation is proposed, in which the key point is an up upward flux cor
rection. As shown in comparative numerical simulations, this model generall
y has a better accuracy than some exiting models. In the condition of the s
olar zenith angle theta (s) less than or equal to 75 degrees and the viewin
g angle theta (v) less than or equal to 60 degrees, the error by the presen
t model is usually smaller than 2.5%.