A semi-empirical modelling approach to calculate two-way attenuation in radar backscatter from soil due to crop cover

Synthetic aperture radar (SAR) backscatter from crop-covered agricultural fields is a strong function of dielectric properties of the crop, crop canopy structure, crop volume along with moisture and surface roughness of the underlying soil. These unique features of SAR along with its ability to penetrate through vegetation and soil make it a right choice for many agricultural applications like soil moisture estimation and crop monitoring. Backscattering coefficient contains information of the crop as well as the soil underneath and therefore, in order to retrieve soil moisture or the crop parameters from SAR backscatter, it is necessary to separate out the relative contributions of the soil underneath and the vegetation layer. The effect of crop cover on the sensitivity of SAR backscatter towards soil moisture is more severe, as the crop cover not only introduces its own backscatter contribution ($\sigma^{o}_{crop}$), but also introduces two-way attenuation in the radar backscatter from the soil surface. An attempt has been made here to adopt a semi-empirical modelling approach to estimate the SAR backscatter contribution from the crop cover ($\sigma^{o}_{crop}$) along with the two-way attenuation (1/L2) introduced by the crop cover in SAR backscatter from the soil as well. This has been done using Extended Low-1 beam mode RADARSAT-1 SAR data over parts of Haridwar and Saharanpur districts. We report here the results obtained from the study during March 2005 and March 2006, and discuss the methodology used for the calculation of two-way attenuation in the backscattering coefficient from the soil surface and from that of wheat crop.