A Comparison Analysis Between SMAP, SMOS and ATI Root Zone Soil Moisture Estimations

This research presents a comparison between three different root zone soil moisture (RZSM) estimations obtained through satellite with in situ measurements from the Soil Moisture Measurement Stations Network of the University of Salamanca (REMEDHUS). The first product analyzed was the Soil Moisture Active Passive (SMAP) L4 RZSM product. The second satellite product was the surface soil moisture (SSM) of the Soil Moisture and Ocean Salinity (SMOS) mission, in which the Soil Water Index (SWI) model was applied to retrieve RZSM. Finally, the Moderate Resolution Imaging Spectroradiometer (MODIS) was used to retrieve SSM using visible/infrared observations and the apparent thermal inertia (ATI) algorithm. The derived SSM from the ATI was then transformed into RZSM through the SWI. The statistical results showed similar performance for the three products. However, the good results based on the MODIS ATI must be highlighted since this methodology is only based in thermal imagery.