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Drought characteristics in the Middle East simulated by raw and bias-corrected CMIP6 models
Babak Ghazi1, Hossein Salehi2, Kaveh Madani3
1Department of Meteorology and Climatology, Faculty of Earth Sciences and Spatial Management, Nicolaus Copernicus University, Toruń, Poland.
The Science of the Total Environment
|September 20, 2025
Summary
Future Middle East droughts will intensify, with the Standardized Precipitation Evapotranspiration Index (SPEI) showing higher probability and longer durations than the Standardized Precipitation Index (SPI). Downscaled climate models (NEX-GDDP) offer improved projections over raw general circulation models (GCMs).
Area of Science:
- Climate Science
- Hydrology
- Environmental Science
Background:
- The Middle East faces significant drought risk due to its arid climate and limited water resources.
- Existing climate projections for Middle East droughts lack comprehensive analysis of model biases and spatial resolution impacts.
- Understanding future drought characteristics is crucial for water resource management and regional stability.
Purpose of the Study:
- To compare drought projections from NASA NEX-GDDP downscaled data and raw CMIP6 general circulation models (GCMs) for the Middle East.
- To assess the influence of model biases and spatial resolution on future drought projections under various Shared Socioeconomic Pathways (SSPs).
- To evaluate drought characteristics using Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI).
Main Methods:
- Utilized NEX-GDDP and raw CMIP6 GCMs for drought analysis.
- Employed SPI and SPEI to assess drought probability and duration.
- Analyzed projections across four SSP scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0, SSP5-8.5) for historical, near-future, and far-future periods.
Main Results:
- Both NEX-GDDP and raw GCMs project increased drought probability in the Middle East.
- SPEI consistently indicates higher drought probability and spatial extent than SPI, especially for longer durations (6- and 12-month scales) in the far future.
- NEX-GDDP models demonstrate superior performance over raw GCMs due to better precipitation distribution representation, highlighting the value of statistical downscaling.
Conclusions:
- Future drought conditions in the Middle East are projected to worsen significantly, particularly under higher emission scenarios (SSP3-7.0 and SSP5-8.5).
- The increasing role of evapotranspiration, as captured by SPEI, suggests more severe and prolonged droughts.
- Enhanced drought conditions pose substantial risks to water security, human populations, and potentially regional stability.
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