Estimation of soil microwave effective temperature at L and C bands

The soil microwave effective temperature (T_e) is an important parameter which improves the accuracy of the soil surface moisture derived from low frequency microwave radiometric observations. A new semi-empirical model of T_e at L- and C-bands is proposed. The model is based on the following inputs: the air temperature (T_a), a deep soil temperature (T_d), and the microwave brightness temperature measured at X-band (λ≃3 cm) and V polarization (T_BXV). Unlike other approaches based on the surface temperature (T_s), the proposed model can be implemented without being dependent on the clear sky conditions required to measure T_s with a spaceborne infrared radiometer. However, the proposed model may also use T_s when available. The model was designed from a large data set simulated by a physical model for smooth bare soil. The model of T_e was then successfully validated with experimental data acquired during a ground based experiment with the multifrequency PORTOS radiometer. This model designed from smooth soil data was successfully tested on rough bare soil using experimental data