Integrating climatic aridity indices and satellite vegetation indicators for agro-hydrological monitoring of vineyard drought stress

Vineyards in the Iberian Peninsula are highly sensitive to water stress driven by climate variability, particularly under the increasing frequency and intensity of drought events associated with climate change. Reliable, long-term indicators of water availability are therefore essential for monitoring vineyard vulnerability and supporting agro-hydrological assessment and adaptation strategies at regional scales. This study evaluates the performance of the De Martonne Aridity Index (DMI) as a climatic indicator for long-term monitoring of drought stress in vineyards across the Iberian Peninsula over the period 1993–2022.

Monthly DMI values were computed using bias-corrected temperature and precipitation data from the ERA5-Land reanalysis, allowing for a consistent characterization of aridity conditions over three decades. Vineyard conditions were independently assessed using the Vegetation Health Index (VHI), derived from satellite observations and spatially restricted to vineyard land-cover areas. The VHI integrates information on vegetation vigor and thermal stress, providing an effective proxy for plant response to water stress. Drought severity classes based on DMI were systematically compared with VHI-derived vegetation stress classes through spatial and temporal analyses.

The results reveal a strong correspondence between low DMI values and reduced VHI, particularly during periods classified as severe and extreme drought. This agreement indicates that the DMI effectively captures major water stress conditions affecting vineyard systems, despite its simple formulation and limited data requirements. Temporal analyses show that prolonged dry periods identified by DMI are consistently associated with sustained vegetation stress signals, while spatial patterns highlight a higher recurrence and persistence of drought impacts in central and southern regions of the Iberian Peninsula. In contrast, northern areas exhibit lower drought frequency and reduced vineyard vulnerability.

Overall, the findings demonstrate that the De Martonne Aridity Index provides a robust and practical indicator for regional-scale vineyard drought monitoring. When combined with satellite-based vegetation indices, DMI contributes valuable climatic context for agro-hydrological assessment, supporting drought impact analysis, water resource evaluation, and climate adaptation studies. Its simplicity and scalability make it particularly suitable for long-term monitoring frameworks and for complementing remote sensing approaches in viticultural water management under changing climatic conditions.