Validation of SMAP Satellite-Based Soil Moisture in Different Land Uses of Simineh-Zarrineh (Bokan) Basin

Soil moisture is a key variable in determinant terrestrial systems for water and energy exchanges between the earth's surface and the atmosphere. In this study, the soil moisture data of SMAP satellite at different times and land uses were validated through four indices of correlation coefficient, root mean square error, unbiased root mean square error, and mean difference in 2017. For this purpose, Simineh-Zarineh basin located in the south and southeast of Urmia Lake, which is the largest sub-basin of the Urmia Lake basin, was investigated. The total study area is about 1762500 hectares. The spatial and temporal resolution of the SMAP satellite is 9 square kilometers and three days. Therefore, 287 ground points on a grid were selected for sampling in the study area. The results showed that the SMAP satellite data with ground observation data on December 3 and April 3 had a maximum RMSD value of 0.25 to 0.35 cm3 cm-3. The results revealed that the soil moisture data of SMAP satellite with RMSD values between 0.18 to 0.33 cm3 cm-3 and ubRMSE between 0.17 to 0.33 cm3 cm-3 show better performances correspond to ground data. The highest correlations and the lowest RMSD value were observed in July 3rd and September 13th, respectively. The lowest RMSD and the highest correlation for dryland was observed on April 3rd. In July 3rd the highest correlation was observed in all land uses, and among them the highest correlation was observed in dryland.