The effect of electromagnetic wave polarization on wave attenuation in a vegetation canopy

The extinction coefficient of a radar wave traversing vegetation was modeled as a function of polarization and angle of incidence, using data from scatterometers and laboratory experiments. Results show that HH polarized waves suffer less attenuation than VV, and are more suitable for moisture determination of agricultural soils. Vegetation influence is minimal to 20 degrees of incidence in HH mode, while it is significant in VV. Penetration is greater with HH polarization, so that backscattering is influenced down to soil level. For VV polarization, the upper layer contributes most, so this type of polarization is better to study crops such as wheat, where the ears are of interest.