An Emission Models (EM) adequate for a retrieval algorithm requires being simple while still capturing the responses of brightness temperatures T^p,θ_B to the retrieval parameters. The objective of this study is to explore the benefits of the multiple-scattering Two-Stream (2S) EM over the "Tau-Omega" (TO) EM to retrieve soil Water Content WC and vegetation optical depth τ from L-band T^p,θ_B. For sparse and low-scattering vegetation T^p,θ_B,EM simulated with EM = TO and EM = 2S converge, which is not the case for dense and strongly scattering vegetation. WC_RC and τ_RC are retrieved with Retrieval Configurations RC = {TO, 2S} from T^p,θ_B measured: i) from a tower within a deciduous forest, and ii) by the "Soil Moisture and Ocean Salinity" (SMOS) mission. Using 2S EM instead of TO EM resulted in marginally lower WC_RC retrievals while τ_RC retrievals are reduced more considerably. With respect to in-situ WC_in-situ, retrievals WC_2S derived from tower-based T^p,θ_B performed better than forest soil water-content WC_TO retrieved via the inversion of the "reference" TO EM. Likewise, SMOS based WC2S retrievals revealed better agreement with ECMWF WC simulations than WCTO achieved with the "reference" RC = TO. In short, our study provides clear evidence that it is meaningful to replace TO EM used for current SMOS and SMAP land retrieval with 2S EM.

Further advantages of the 2S EM over the TO EM are outlined in this study.