Drought characteristics in the Middle East simulated by raw and bias-corrected CMIP6 models

The Middle East is among the most drought-prone regions globally, primarily due to its naturally arid climate and scarce water resources. While climate projections indicate worsening drought conditions, a critical gap remains in understanding how model biases and spatial resolution influence these projections. This research focuses on the future of droughts in the Middle East by providing comprehensive comparisons of NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP) and raw general circulation models (GCMs) from Coupled Model Intercomparison Project Phase 6 (CMIP6). The study assesses drought characteristics using the Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) under four Shared Socioeconomic Pathway (SSP) scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0, SSP5-8.5) for historical (1985-2014), near future (2041-2070), and far future (2071-2100) periods. Our findings indicate a significant increase in drought probability for both raw-GCMs and NEX-GDDP models. SPEI consistently projects a higher probability and broader spatial extent of droughts in the far future compared to SPI, particularly for longer durations (6- and 12-month scales), highlighting the increasing role of warming-driven evapotranspiration. Under SSP3-7.0 and SSP5-8.5 scenarios, in the far future, for SPEI-based drought, it is projected that mean drought probability increases by 33 %-41 %, compared to 6 %-15 % for SPI-based drought. In addition, results revealed the superior performance of NEX-GDDP models over raw-GCMs, as a result of the better reproduction of precipitation distribution, indicating the added value of statistical downscaling for regional-scale climate analysis. Moreover, SPEI systematically projects longer drought durations, with 12-month droughts potentially increasing by 40 months in the far future under SSP5-8.5, relative to the historical period. The increase in the probability and duration of droughts can exacerbate the region's already high water stress, posing severe challenges for human populations and potentially impacting global stability.