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This letter presents the results evaluating retrievals of liquid water content (theta(liq)) performed with a zero-order radiative transfer (tau-omega) model under frozen and thawed soil conditions from Soil Moisture Active Passive (SMAP) and ELBARA-III brightness temperature (T-B(P) ) measurements collected over a Tibetan meadow ecosystem. A good agreement is found between time series of the SMAP and ELBARA-III measured T-B(P) resulting in a Pearson product-moment coefficient (R) larger than 0.87. Differences noted between the two data sets can be associated with discrepancies in theta(liq) measured in the specific footprints, whereby the SMAP measurements are best explained by the in situ theta(liq). Furthermore, the in situ theta(liq) has a better agreement with the horizontally polarized SMAP and ELBARA-III measurements (T-B(H)) in the cold season, whereas the vertically polarized measurements (T-B(V)) are better correlated with liq in the warm season. With the implementation of new vegetation and surface roughness parameterizations for the tau-omega model, the dynamics of in situ theta(liq) is better reproduced by corresponding retrievals for both frozen and thawed soil conditions, leading to the reduction in the unbiased root-mean-square error (ubRMSE) by more than 31% in comparison with these retrievals using SMAP default parameterizations. Notably, the single-channel algorithm configured with the new parameterizations using SMAP T-B(V) measured during the ascending overpass provides the best theta(liq) retrievals with a ubRMSE of 0.035 m(3).m(-3) that is well within the SMAP mission requirements.