Wheat scattering mechanisms observed in near-field radar imagery compared with results from a radiative transfer model

The authors present a comparison between the backscatter information from a spring wheat canopy and the predictions of a radiative transfer model. Microwave measurements on a small wheat canopy were made in an anechoic chamber during the 1999 growing season over a range of frequencies, polarisations and incidence angles. The crop was measured at six different stages during the growing season and the resulting imagery clearly shows the various scatter mechanisms within the crop canopy. Simultaneous architectural information from the crop was gathered for each of the measurement sets to provide input parameters for a second order radiative transfer model (RT2). A comparison between the scattering in the individual layers predicted by the model and the scattering visible within the layers of the imagery was carried out. In addition, the total backscatter obtained from the model was compared with that from a measured canopy. The differences observed appear to be due to inadequate descriptions of plant components and incorrect representation of attenuation in the model.