Feasibility of the SMOS soil moisture for agricultural drought monitoring: Assessment with the Soil Water Deficit Index

A comparison analysis was made between the SWDI (Soil Water Deficit Index) calculated with in situ and SMOS (Soil Moisture and Ocean Salinity satellite) soil moisture series (June-2010 to December-2014), over an agricultural area in Spain. Additionally, both SWDI have been compared with two well-known agricultural drought indices, the CMI (Crop Moisture Index) and the AWD (Atmospheric Water Deficit index), used as reference indicators. The main goal was to assess the feasibility of SMOS data for agricultural drought monitoring. The results show that the SMOS-based index correlates very well with the in situ one, both using surface and root-zone soil moisture data. The comparison was also acceptable in the case of the CMI but was much better when the AWD was used, showing that the SWDI calculated with SMOS data is able to track the soil water dynamics and that it is a suitable tool for agricultural drought monitoring.