Comparing Satellite Soil Moisture Products Using In Situ Observations Over an Instrumented Experimental Basin in Romania

This study assessed the performance of different remotely sensed soil moisture products with in situ observations; six profile probes for the water content monitoring were selected, operating during 2016–2021 from the Voine¸sti Experimental Basin in the Romanian Subcarpathian region. The reliability of satellite observations has been analyzed on both single ground-based observation points and spatialized information, considering near-surface and root-zone soil moisture data. The physics-based index (HCI) and some statistical tests widely used in inter-comparison analyses have been computed. The study of HCI highlighted that the SMAP SP_L4_SM products have shown the best performances considering the near-surface and root-zone data evaluations. The comparison of SWI1km observations with in situ data produced good results for single-point and spatialized soil moisture estimations acquired at different depths over the experimental basin. The SSM1km and SMAP L2_SM_SP products exhibited the lowest performances. The results contribute to the validation of satellite products of surface and root-zone soil moisture in the Subcarpathian region, helping to provide information in an area not monitored by the International Soil Moisture Network. The findings offer valuable insights into evaluating the performance of satellite soil moisture products in the Romanian region.