Soil moisture retrievals from biangular L-band passive microwave observations

A simple approach for correcting the effect of vegetation in the estimation of soil moisture (w_S) from L-band passive microwave observations is presented in this study. The approach is based on statistical relationships, calibrated from simulated datasets, which requires only two observations made at distinct incidence angles (θ₁,θ₂). A sensitivity study was carried out, and best retrieval remote sensing configurations, in terms of polarization and couple of incidence angles (θ₁,θ₂), were investigated. Best estimations of w_S could be made at H polarization, for θ₁ varying between 15° and 30°, and with a difference (θ₂-θ₁) larger than 30°. The method was tested against two experimental datasets acquired over crop fields (soybean and wheat). The average accuracy in the soil moisture retrievals during the whole crop cycle was found to be about 0.05 m³/m³ for both crops.