BRDF modeling comparison in hotspot effect with modified kernel-driven models

Kernel-driven model has been widely used in operational production including RossThick-LiSparse-Reciprocal model in MODIS (Lucht et al., 2000) and RossThick-Roujean model in POLDER (Roujean et al., 1992). Both the operational models have used the RossThick as the volumetric kernel. However, RossThick kernel does not count for the so-called hot spot effect. In this paper, analyses have been investigated into the hotspot effects for two models. The research aims to further study the modified classic kernel-driven models' performances in the principal plane, particularly in the retro-solar direction using Bréon et al. hot spot factor (Bréon et al., 2002). The results show that the factor indeed improves the hotspot modeling of RossThick used in kernel-driven models. However, the factor is somewhat not so suitable for land cover type without strong hotspot effect.