Monitoring vegetation and soil from passive and active microwave remote sensing data: A model analysis

Microwave remote sensing data are particularly well suited to global monitoring of tile earth. Frequent estimates of the surface characteristics can be obtained, since the atmosphere is nearly transparent to the low frequency(1-10 GHz) microwave radiations. Also, the microwave sensors can provide estimates of surface variables which are key determinant of water and energy exchanges at the soil/atmosphere interface. Based on a sensitivity analysis, the present work investigates possible synergy between passive and active microwave data over vegetation covered areas. The simulations are carried out for a leafy agricultural vegetation cover (soybean). Based on bi-frequency passive or active microwave measurements and simultaneous passive/active measurements, the potential of the microwave sensors in estimating two key land surface variables, surface soil moisture and vegetation biomass, is investigated in this work. In particular, it is found that the combination of active & passive data is very efficient when monitoring vegetation biomass: the active technique has the best potential, in some specific configurations, for rather dr; soil conditions; while the passive technique is generally more efficient for rather wet soil conditions.