A model of the top-of-atmosphere reflectance in the visible and near infrared is presented. The reflectance is parametrized as the product of a constant and normalized bidirectional and temporal functions. Bidirectional and temporal effects are thus separated. The bidirectional function includes isotropic, nonazimuthally dependent, and azimuthally dependent, yet symmetric, components. The temporal function is a development in modified Fourier series. An iterative scheme is used to determine the constants of the model. Applying the scheme to AVHRR data acquired in 1987 over the Konza Prairie during FIFE, 98 and 95% of the variance is explained in the visible and near-infrared channels, respectively. The remaining variance exhibits no apparent dependence with water vapor and aerosol contents. ¿ American Geophysical Union 1995