Validation of SMOS Level 2 Soil Moisture Products over the West and Southwest Catchments of Iran

The European Space Agency’s (ESA) Soil Moisture and Ocean Salinity (SMOS) satellite mission was launched in November 2009 that carries the first L-band (1.4 GHz) 2-D synthetic aperture microwave radiometer. SMOS provides global surface soil moisture over the land surfaces with an averaged ground resolution of 43 km over the field of view and with an expected accuracy of 0.04 m³m⁻³ every 3 days. The objective of this study is the validation of soil moisture retrievals from SMOS Level 2 Soil Moisture (MIR_SMUDP2) Products over the west and southwest of Iran. Validation of SMOS soil moisture were done using the In situ soil moisture observations from the meteorological stations in the study area. The validation process was carried out using Collocation technique for the period 2012 to 2013. Four statistical metrics and Taylor diagram were used for the evaluation error of validation; the Root Mean Squared Difference (RMSD), the centered Root Mean Square Difference (cRMSD), the Mean Bias Error or bias and the correlation coefficient (R). The results of validation error shows a good correlation (R) between the SMOS soil moisture and In situ data. Based on the RMSD results, the SMOS soil moisture data have acceptable accuracy at the most of stations that are close to the SMOS target accuracy (RMSD < 0.04 m3 m−3). Due to the lack of soil moisture data in the most parts of Iran, we can use the SMOS products as a tool to derive soil moisture maps over the area field.