Bi-decadal drought assessment in Northwestern Algeria: integrating meteorological and remote-sensing indices.

Drought is an escalating hazard in arid and semi‑arid regions with major consequences for agriculture, ecosystems, and water resources. This study presents a 2003–2023 integrated assessment of meteorological and vegetation-based drought across northwest Algeria (2003–2023) using CHIRPS precipitation and MODIS remote‑sensing products. Meteorological drought was quantified with the Standardized Precipitation Index (SPI) at 3‑, 6‑ and 12‑month timescales; vegetation and thermal stress were assessed with MODIS‑derived Vegetation Condition Index (VCI), Temperature Condition Index (TCI) and Vegetation Health Index (VHI). Temporal trends were evaluated using the Mann–Kendall test and Sen’s slope estimator, and relationships between precipitation and vegetation were examined with Pearson correlation. We identify recurrent drought episodes in 2007–2009, 2011–2012 and a pronounced dry phase from 2020–2023. Mann–Kendall results indicate widespread drying across all SPI timescales, with 56% of the study area showing significant negative trends at SPI‑3 (mean Sen’s slope = − 0.10 yr⁻¹). Vegetation indices mirror these changes: VHI shows substantially more degraded area than improvement (4.89% vs 0.51% of the domain), while VCI and TCI responses are spatially heterogeneous. The strongest coupling between precipitation and vegetation occurs at the semi‑annual scale (SPI‑6 vs VHI, r = 0.578), suggesting that 6‑month precipitation anomalies best predict agricultural drought in this region. These results demonstrate the value of combining meteorological and satellite vegetation indices for regional drought monitoring and early warning, and they point to an ongoing shift toward increased aridity with implications for water management and agricultural adaptation.