The brightness temperature (T-B(P)) observed by the Soil Moisture Active Passive (SMAP) satellite mission is significantly affected by the soil permittivity (epsilon(s)), surface roughness and vegetation opacity (tau(P)). This study assesses the impact of these factors on simulating the SMAP horizontally (p = H) and vertically (p = V) polarized T-B(P) K-measurements and retrieving the liquid soil water content (theta(liq)) for both frozen and thawed soils in the typical Tibetan desert and meadow ecosystems. For this investigation, the zero-order approximation of the radiative transfer equations, i.e., tau-omega emission model, is configured with surface roughness and tau(P) parameterizations adopted by current SMAP soil moisture retrieval algorithms, and the es is computed with the four-phase dielectric mixing model that epsilon(s) is applicable for both frozen and thawed soils.