Validation of Aquarius Soil Moisture Products Over the Northwest of Spain: A Comparison With SMOS

Abstract

[EN]A validation of the new L2 and L3 soil moisture products from the Aquarius/SAC-D mission from August 2011 to June 2014 using two in situ networks in Spain was conducted. The first network, the Soil Moisture Measurement Stations Network of the University of Salamanca (REMEDHUS), is considered to be a dense network. The second network (Inforiego) could be considered a sparse or large-scale network. Comparisons of temporal series using different strategies were made. Similar analysis was performed for the same area and period with two soil moisture ocean salinity (SMOS) soil moisture products: SMOS L2 and SMOS Barcelona Expert Center (BEC) L3. The aim of the study was to analyze the performance of the Aquarius soil moisture products and to compare with that of SMOS soil moisture. Results from the area-averaged comparison show that Aquarius products have correlation coefficients (R) between 0.33 and 0.65, and root-mean-square difference (RMSD) and centered RMSD (cRMSD) between 0.046 and 0.111 m3m−3. A better match was found for the L2 ascending series than for the L2 descending and L3 series. A dry bias was found. SMOS products showed better accuracy (R > 0.8, RMSD and cRMSD ∼ 0.06m3m−3) than those of Aquarius. The comparison made at point-scale reflected that the size and density of the networks do not influence the validation results at the Aquarius resolution, but it is remarkable at the SMOS resolution. Despite the scale restrictions, the results of this study showed that Aquarius soil moisture products have reasonably good performance.