A multifrequency algorithm for the retrieval of soil moisture on a large scale using microwave data from SMMR and SSM/I satellites

The sensitivity of microwave emission at different frequencies to soil mois ture in bare and vegetated soils has been investigated using experimental d ata. Since the best frequency for the measurement of soil moisture (L-band) is absent in current satellite sensors, it is necessary to seek alternativ e solutions. An algorithm is proposed for the retrieval of soil moisture ba sed on the sensitivity to moisture of both the brightness temperature and t he polarization index at C-band, one that is able to correct for the effect of vegetation by means of the polarization index at X-band. The algorithm has been tested by using experimental data collected with airborne microwav e radiometers on agricultural areas and validated by using the data sets of special sensor microwave/imager (SMM/I) and scanning multichannel microwav e radiometer (SMMR). These research activities are planned in view of comin g new satellites: AQUA (NASA) and ADEOS-II (NASDA), which will be launched by the end of 2001. These will have new generation microwave radiometers (A MSR-E and AMSR) onboard, which show much better characteristics with respec t to the previous sensors, in particular an enhanced spatial resolution.