Diurnal variation of backscattering properties of pine trees at C and X-band

The behavior of the backscattering coefficient of a pine tree canopy was monitored at C- and X-band, VV, HH, VH and HV polarizations over a period of 24 hours in August 1993. By using their HUTSCAT ranging scatterometer, the authors could measure separately the total backscattering coefficient, the ground contribution and the canopy contribution. The incidence angle was 40° off nadir and the radar system was moved along a rail in order to obtain enough independent samples. The volumetric moisture of a tree trunk and ground surface (0 to 15 cm) along with the air temperature and total solar radiation was monitored as well. The backscattering coefficient for various frequency/polarization combination was compared with the ground truth. The results indicate that the diurnal behavior of the backscattering coefficient at C-band is different from that at X-band