Multitemporal radar backscattering measurement of wheat fields using multifrequency (L, S, C, and X) and full‐polarization

[1] This paper presents the measurements of the backscattering coefficients over the wheat fields using an L-, S-, C-, and X-band scatterometer system during a whole period of wheat growth. The wheat field located at Qionglai County of China was measured during a wheat growing season from November 2010 to May 2011. Twelve experimental acquisitions (ground and radar data) were measured over the wheat field in a flat area at VV-, VH-, HV-, and HH-polarizations of L-, S-, C-, and X-bands, with the incidence angles ranging from 0° to 80°. Wheat biomass, canopy structure, leaf area index (LAI), soil moisture, and eco-physiological canopy variables were also collected to investigate the radar sensitivity. It shows that the HH measurements for wheat are higher than VV at each band after jointing, and the value of HH/VV is larger for lower frequency. The temporal variations of each band at selected incidence angles were compared with the wheat biomass, canopy height, LAI, and soil moisture. The correlations were analyzed between backscattering coefficients and wheat crop variables at 23°, 38°, 53°, and 68°, respectively. The results show that the backscattering coefficient has a strong correlation with biomass and LAI, especially for the HH- and cross-polarizations of L-band, and the radar backscatter signatures at high frequency (X- and C-bands) are sensitive to detect newly transplanted thin wheat seedlings at the high incident angle. These data can provide experimental evidence to allow for determining the growth status and/or condition of wheat by use of measured radar backscatters.