A Multiscale Remote-Sensing Assessment of Root-Zone Soil Moisture, Evapotranspiration and Canopy Moisture Stress Across Uruguay During the 2020–2023 Drought

Abstract

Drought affects meteorological forcing, root-zone water availability and land-surface functioning at different spatial and temporal supports. We evaluated Uruguay’s 2020–2023 drought using an observational 2016–2024 panel of 1423 SMAP parent cells. Monthly SPEI-3, SPEI-6 and SPEI-12 represented short, intermediate and persistent climatic water-balance deficits. SMAP root-zone soil moisture (RZSM) was retained at 9 km support, whereas actual evapotranspiration (ETa) and the moisture stress index (MSI) were summarized from approximately 500 m pixels using annual MapBiomas fractions for grassland, cropland and silviculture within each parent cell. For each cell and 8-day composite position, responses were expressed relative to the corresponding 2016–2019 mean. An interval was classified as locally dry when its overlap-day-weighted SPEI-12 was below −1. During 2020–2023, RZSM responses ranged from −13.09% to −16.63% among dominant landscape domains. Fraction-weighted ETa responses were −8.69% for grassland, −6.75% for cropland and −7.39% for silviculture, while oriented MSI responses were −6.62%, −3.32% and −11.20%, respectively. At lag zero, monthly RZSM correlated the most strongly with SPEI-3 (r = 0.81), followed by SPEI-6 (r = 0.64) and SPEI-12 (r = 0.51). At native 8-day support, RZSM was positively aligned with ETa (r = 0.42–0.57) and the oriented MSI (r = 0.31–0.59), although prewhitening weakened some associations. Overall, the 2020–2023 drought was consistently expressed across meteorological, root-zone and land-surface indicators. The strong association between SPEI-3 and RZSM, together with consistent land-surface departures and product-dependent ETa variation among components, highlights the value of multiscale monitoring for characterizing drought intensity and ecosystem responses across Uruguay.