Drought Trends and Variability in the Arabian Peninsula Using SPEI and SPEDI Indices and their Implications for Climate Adaptation

Abstract

Recent decades have witnessed intensifying drought across the Arabian Peninsula, yet scientists poorly understand whether precipitation deficits or increased potential evapotranspiration (PET) drive this intensification. This study employs the Standardized Precipitation Evapotranspiration Index (SPEI) and Standardized Precipitation Evaporation Differential Index (SPEDI) at 3, 6 and 12-month timescales to assess drought across the Arabian Peninsula from 1975 to 2024 using ERA5 Land reanalysis data validated against observed meteorological stations. We isolated each variable’s contribution through diagnostic scenarios, holding either PET or precipitation at climatological means while varying the other. Validation results demonstrated exceptional ERA5 Land performance for temperature variables (mean R = 0.99, NSE > 0.89) and adequate performance for precipitation (mean R = 0.72, NSE = 0.48). Temporal analysis revealed intensifying multi-year droughts with drought-affected areas increasing by 20 to 133 percent between the first (1975–1999) and second (2000–2024) periods of the study across all zones. The Frequency Innovative Trend Analysis (F-ITA) confirms a systematic decline in wet anomalies and increases in drought frequency with the southwestern zone experiencing the most pronounced shift, where mild drought rose from 14.6 percent to 37.6 percent for SPEI 12. The SPEI scenarios revealed that PET contributes 68 to 77% of drought trend variability across climatic zones, while the contribution of precipitation is only 23 to 32%. In SPEI scenarios, when PET is held constant (PETclm), significant drying trends largely disappear; conversely, drought intensification exceeds observed trends when precipitation is held constant (Prclm), confirming thermodynamic forcing as the primary driver. The findings demonstrate that rising temperatures will determine future drought severity in the Arabian Peninsula, necessitating fundamental shifts in water resource management from precipitation-centric approaches toward strategies explicitly addressing temperature-driven PET.

Keywords: Drought intensification; SPEI; SPEDI; Potential evapotranspiration; ERA5-Land; Climate change; Arabian Peninsula

 

Acknowledgment

This work was supported by the Korea Environmental Industry & Technology Institute (KEITI) through Water Management Program for Drought, funded by the Korea Ministry of Climate, Energy and Environment(MCEE)(2480000378).