Synergy of active and passive signatures to decouple soil and vegetation effects

In the past years, several works demonstrated that the emissivity e and the backscattering coefficient σ° of land surfaces are affected in different ways by surface variables. In particular, an increase of soil roughness or vegetation biomass may produce an increase of both the emissivity and the backscattering coefficient. On the contrary, an increase of soil moisture always produces opposite effects on the two parameters. In this paper we show that a synergistic use of active and passive signatures allows us to decouple soil moisture effects from the effects of vegetation, better than in the case of a single instrument. To this end, we present experimental data and model simulations that support this idea, and we introduce the σ°/(1-e) parameter, which increases with vegetation biomass and it is scarcely influenced by soil moisture.