Assessment of the newest ECV soil moisture product over the Tibetan plateau using ground-based observations

Validation of the remotely sensed soil moisture products is very important for data application and the refinement of the retrieval algorithms. In the study, we evaluated three newest soil moisture products that are the essential climate variable (ECV) soil moisture products (active-only, passive-only, and merged active-passive) which are the first multi-decadal satellite-based soil moisture data sets released by the European Space Agency recently. In-situ measurements used for validation are from three networks established in the Tibetan Plateau. The results show that all the ECV products can capture the soil moisture dynamics well. The active product performs better than the passive product when adding the Advanced Scatterometer (ASCAT) data set and is less sensitive to vegetation cover, but both of them overestimate the ground measurements and exhibit higher variation than in-situ data. Overall, the combined product outperforms other two products. It can preserve the relative dynamics of the active and passive products very well and the number of observations is also improved, indicating a positive effect by merging both active and passive data sets in the Tibetan Plateau.