The Development of Microwave Vegetation Index for Future SMOS Applications

Knowledge of the variability of microwave signatures of vegetation and roughness are necessary to separate these influences from those of soil moisture for remote sensing applications to global hydrology and climate. Conventional, vegetation indices are often limited by the effects of atmosphere, background soil conditions. The Soil Moisture and Ocean Salinity (SMOS) satellite will provide global multi-angular microwave brightness temperature observations at L-band, in dual polarization and multi-angles. Through the analysis of the simulations by the advanced integral equation model (AI EM), we found that the polarization difference for the bare surface emission signals at different view angles can be well characterized by a line function with parameters that are dependent on the pair of view angles to be used. This makes it possible to minimize the surface emission signal and maximize the vegetation signal when using multi-angular radiometer measurements. The developed microwave vegetation index (MVI) is independent of soil surface emission signals and can provide new vegetation information since the L-band microwave measurements are sensitive to the properties of the overall vegetation. We compared the developed MVI with the Leaf Area Index (LAI) with SMOSREX data in 2003. The results showed that the general distribution and the change patterns of the MVI are consistent with those of LAI and VWC derived by the field experiments. This method provides a new opportunity to monitor vegetation cover for future SMOS applications.