Evaluation of satellite-based soil moisture for agricultural drought monitoring in the Brazilian semiarid region

The Northeast region of Brazil, particularly the Brazilian semiarid region (BSR), is frequently affected by drought events, such as the great drought that started in 2012 and is considered one of the most severe droughts in recent decades. Monitoring and quantifying this type of event is essential for decision-making and the adoption of impact mitigation strategies. In this study, re-motely sensed soil moisture (SM) data from three products derived from Soil Moisture and Ocean Salinity (SMOS-CATDS and SMOS-IC) and Soil Moisture Active Passive (SMAP) were validated in the BSR using a dense network of in situ stations (N = 120) from 2015 to 2020. Subsequently, the best product was selected for the evaluation of agricultural drought, based on the Soil Water Deficit Index (SWDI), which was compared with the Atmospheric Water Deficit (AWD) obtained from in situ data (N = 50). After validation, SMAP was selected as the best product for estimating SM in the BSR, and SWDI-SMAP showed a strong temporal correlation with AWD. Based on these two indices, the results indicate the severity of drought in the BSR during the evaluated period, with significant social and economic impacts, highlighting the need for continuous monitoring, especially to support family farming, which is predominant in the region.