Diurnal/Seasonal variation of the bidirectional reflectance distribution function on larix leptolepis forest

Abstract

The change of the reflectance due to the change of the position of the sun, canopy, and sensor geometry is called Bi-directional Reflectance Distribution Function(BRDF). we focused on and revealed the diurnal/seasonal change of BRDF on larix leptolepis forest at Yatsugatake,Japan. As a result of observing BRDF twice or more times on the same day, BRDF changed depending on the solar zenith angle at the time of observation. The index termed HDS(Hotspot-Darkspot signature) that is calculated from the difference between the strongest vector (hotspot) and weakest vector (dark spot) of reflectance is linearly correlated with solar zenith angle. Moreover, it is formed that HDS decreased from september to norbember. This indicated that BRDF changed with phenological change of vegetation.