Jalal et al. (2025) Spatiotemporal dynamics and future projections of aridity in a semi-arid region based on multi-model CMIP6 scenarios

Identification

• Journal: Theoretical and Applied Climatology
• Year: 2025
• Date: 2025-12-17
• Authors: Halah K. Jalal, Waqed H. Hassan, Basim K. Nile
• DOI: 10.1007/s00704-025-05977-z

Research Groups

• College of Engineering, Civil Engineering, University of Kerbala, Kerbala, Iraq
• College of Engineering, University of Warith Al-Anbiyaa, Kerbala, Iraq

Short Summary

This study investigated the spatiotemporal variability and projected changes in aridity across western Iraq using historical data (1993–2023) and multi-model CMIP6 future climate projections (2020–2100). It revealed a predominantly arid to hyper-arid climate, with significant intensification of aridity, particularly in southern regions under high-emission scenarios, underscoring increasing climatic stress on water resources.

Objective

• To assess historical aridity patterns using multiple indices across five meteorological stations in western Iraq.
• To examine the spatiotemporal variability of arid conditions across the study region.
• To evaluate projected aridity changes under SSP245 and SSP585 emission pathways.
• To provide science-based recommendations for climate adaptation policy development and strategic water resource management initiatives at the regional scale.

Study Configuration

• Spatial Scale: Western Iraq, focusing on five meteorological stations: Najaf (32.0217°N, 44.1836°E), Kerbala (32.6076°N, 43.8639°E), Ramadi (33.4466°N, 42.9779°E), Rutba (33.0361°N, 40.2095°E), and Haditha (34.1454°N, 41.7893°E).
• Temporal Scale: Historical period (1993–2023) and future projection period (2020–2100).

Methodology and Data

• Models used:
  • Downscaling: Long Ashton Research Station Weather Generator (LARS-WG 8).
  • Global Climate Models (GCMs) from CMIP6: ACCESS-ESM1-5, HadGEM3-GC31-LL, MPI-ESM1-2-LR, MRI-ESM2-0.
  • Emission Scenarios: Shared Socioeconomic Pathway (SSP245 and SSP585).
• Data sources:
  • Historical meteorological records (1993–2023) from five stations.
  • Daily minimum and maximum temperatures: NASA POWER global meteorological platform.
  • Precipitation data: CHIRPS dataset.
  • Aridity and Drought Indices: Reconnaissance Drought Index (RDI), United Nations Environment Programme (UNEP) Aridity Index (AI), De Martonne Aridity Index, Lang Aridity Index, Standardized Precipitation Index (SPI), and Potential Evapotranspiration (PET).
  • Software: DrinC (Drought Indices Calculator) software version 1.7 for index computation.
  • PET calculation method: Hargreaves methodology.

Main Results

• Historical Aridity (1993–2023): Western Iraq exhibits a predominantly arid to hyper-arid climate. Southern stations (Kerbala and Najaf) consistently show hyper-arid conditions (UNEP AI values between 0.04 and 0.07), while northern stations are classified as arid. A clear latitudinal gradient of increasing dryness towards the south was observed. Potential Evapotranspiration (PET) ranged from 1605.1 mm (Haditha) to 1882.7 mm (Najaf) annually, significantly exceeding local rainfall. SPI analysis revealed notable year-to-year fluctuations with severe to extremely dry conditions, particularly in the south, and recurring severe drought events (e.g., mid-1990s, late 2000s, mid-2010s, 2023–2024).
• Future Projections (2020–2100):
  • SSP245 (moderate emission scenario): Shows some apparent improvements in aridity classifications (e.g., Kerbala and Najaf shifting from hyper-arid to arid by UNEP AI). However, projected PET increases from 0.5% to 11.4% across sites, indicating a significant rise in atmospheric water demand that offsets rainfall increases, leading to worsening actual moisture deficits (e.g., Najaf's absolute moisture deficit increases from approximately 1800 mm to over 1890 mm per year). SPI projections suggest a potential decline in aridity frequency and intensity compared to historical patterns.
  • SSP585 (high emission scenario): Reveals marked environmental decline. Southern stations (Kerbala and Najaf) experience significant intensification of aridity, with PET increasing substantially from 6.6% to 12.2%. Moisture deficits could surpass 1900 mm annually. SPI analysis forecasts enhanced aridity periodicity and magnitude, predominantly targeting southern geographical zones.
• Overall Trend: Southern regions are projected to be more severely affected by aridity than northern areas, a trend expected to continue and worsen under climate change, with profound implications for water management and agricultural sustainability.

Contributions

• Provides the first comprehensive analysis of spatiotemporal aridity dynamics and future projections for western Iraq, addressing a critical knowledge gap in a region previously understudied with predictive climate modeling.
• Integrates multi-model CMIP6 scenarios with a comprehensive suite of aridity and drought indices to offer a robust assessment of climate change impacts.
• Offers science-based recommendations for climate adaptation policy and strategic water resource management, including specific strategies for water-efficient irrigation, early warning systems, and adoption of aridity-resistant crops, tailored to regional differences.
• Highlights the complex interplay between precipitation and potential evapotranspiration in defining actual water stress in arid regions, emphasizing that increased water demand can offset apparent improvements in aridity indices.

Funding

No funding was received for this study.

Citation

@article{Jalal2025Spatiotemporal,
  author = {Jalal, Halah K. and Hassan, Waqed H. and Nile, Basim K.},
  title = {Spatiotemporal dynamics and future projections of aridity in a semi-arid region based on multi-model CMIP6 scenarios},
  journal = {Theoretical and Applied Climatology},
  year = {2025},
  doi = {10.1007/s00704-025-05977-z},
  url = {https://doi.org/10.1007/s00704-025-05977-z}
}