A simulation study of the sensitivity of bistatic scattering to soil moisture and surface roughness at L-band

Abstract

Soil moisture plays a key role in many hydro-meteorological processes. Remote sensing of soil moisture in a bistatic mode has attracted increasing attention in recent years. Systematic simulation of bistatic scattering behaviors from a rough surface offers physical insights into designing bistatic radar configuration and field campaigns. In the study, the sensitivity of bistatic scattering to soil moisture and surface roughness of bare surfaces was investigated. The well-known advanced integral equation model (AIEM) was adopted for this purpose. To better explore the potential of bistatic scattering for soil moisture sensing, both polarized and angular scattering coefficients, and their combinations, were evaluated using a defined sensitivity index. The results show that a better sensitivity to the soil moisture can be achieved by configuring the bistatic observation compared with the monostatic observation from which only backscattering coefficients can be obtained. In a bistatic mode, the scattering coefficients of V V polarization are generally more sensitive to soil moisture than those of HH polarization. The influence of surface autocorrelation function (ACF) cannot be ignored when using a single polarized scattering coefficient, but its effects can be suppressed by a combination of dual polarized or dual angular measurements. Compared to the results of single polarized and combined dual polarized data, it seems that combination of dual angular measurements can achieve the most reliable soil moisture estimation since it can suppress the influence of surface roughness while maintaining a good sensitivity to soil moisture. Equally important to note is that the forward region is preferable for soil moisture sensing in regardless of the ACF.