Selek et al. (2026) Multi-Index evaluation of meteorological drought across Türkiye: a temporal and seasonal perspective

Identification

• Journal: Natural Hazards
• Year: 2026
• Date: 2026-02-25
• Authors: Bülent Selek, Murat Pınarlık, İsmail Faki, Zeliha Selek
• DOI: 10.1007/s11069-025-07961-2

Research Groups

• Ministry of Agriculture and Forestry, Ankara, Turkey
• Civil Engineering Department, Faculty of Technology, Gazi University, Ankara, Turkey
• Graduate School of Natural and Applied Sciences, Gazi University, Ankara, Turkey

Short Summary

This study evaluates the temporal and seasonal dynamics of meteorological drought across Türkiye using SPI, SPEI, and PNI from 1972-2023, revealing an increasing frequency and severity of temperature-driven droughts, particularly in summer and autumn, with a significant intensification after 2000.

Objective

• To evaluate the temporal and seasonal dynamics of meteorological drought across Türkiye using the Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI), and Percent of Normal Index (PNI) to understand its characteristics and trends.

Study Configuration

• Spatial Scale: Nationwide assessment across Türkiye, utilizing data from 255 meteorological stations. Areal average precipitation was derived through Ordinary Kriging interpolation.
• Temporal Scale: Long-term analysis spanning 52 years (1972–2023). Drought assessments were conducted on monthly and seasonal scales, with SPI and SPEI calculated at 3-, 6-, 9-, 12-, and 24-month timescales.

Methodology and Data

• Models used:
  • Standardized Precipitation Index (SPI) using a two-parameter Gamma distribution.
  • Standardized Precipitation Evapotranspiration Index (SPEI) using a three-parameter log-logistic distribution, with Potential Evapotranspiration (PET) estimated by the Thornthwaite method.
  • Percent of Normal Index (PNI).
  • Mann–Kendall (MK) test for trend analysis.
  • Ordinary Kriging with an exponential model for spatial interpolation of precipitation data.
• Data sources:
  • Monthly areal average precipitation data.
  • Monthly average temperature data.
  • All data obtained from the Turkish State Meteorological Service (TSMS) from 255 meteorological stations.

Main Results

• The most severe drought occurred during 2007–2009, with nationwide SPI values dropping below -2.0.
• Severe droughts (SPI < -1.5) were observed in approximately 18% of the study period, with summer droughts being 30–35% more frequent than winter droughts.
• During 2020–2023, more than 70% of stations simultaneously experienced drought conditions, highlighting the increasing influence of temperature-driven evapotranspiration.
• SPEI values were consistently lower than SPI during summer and autumn, reflecting the intensifying role of rising temperatures and Potential Evapotranspiration (PET).
• The PNI corroborated these findings, emphasizing Türkiye’s heightened drought sensitivity during the summer season, identifying 13 drought events (2 severe, 2 moderate) in summer.
• The Mann–Kendall analysis indicated an overall increase in drought severity after 2000, marked by temperature-driven summer drying (SPEI decreasing trend at >90% confidence) and a slight winter wetting tendency (SPI increasing trend at 70–80% confidence).
• Correlation between SPI and SPEI was highest in winter (r = 0.9666) and lowest in summer (r = 0.5771), and decreased with increasing time scales (from r = 0.8598 at 3 months to r = 0.7106 at 24 months), indicating a growing influence of evapotranspiration on longer-term droughts.

Contributions

• Provides an unprecedented spatially and temporally comprehensive assessment of drought dynamics across Türkiye, utilizing data from 255 meteorological stations over a 52-year period (1972–2023).
• Employs areal precipitation data generated through Ordinary Kriging interpolation, ensuring a realistic spatial representation of rainfall distribution and enhancing the reliability of drought assessments.
• Offers an integrated assessment by using both precipitation-based (SPI, PNI) and temperature-based (SPEI) indices, providing a more complete understanding of drought drivers, particularly the intensifying role of temperature-driven evapotranspiration.
• Focuses on the temporal dynamics of drought, addressing a scarcity of long-term, nationwide drought studies specific to Türkiye and offering valuable insights for monitoring and management.
• Demonstrates the added value of temperature-based indices in drought monitoring and provides essential insights for drought early warning systems and water resource management in drought-prone regions.
• Highlights Türkiye's entry into a temperature-driven drought regime, underscoring the urgent need to integrate temperature effects into national drought monitoring and adaptation strategies.

Funding

• Scientific and Technological Research Council of Türkiye (TÜBİTAK).

Citation

@article{Selek2026MultiIndex,
  author = {Selek, Bülent and Pınarlık, Murat and Faki, İsmail and Selek, Zeliha},
  title = {Multi-Index evaluation of meteorological drought across Türkiye: a temporal and seasonal perspective},
  journal = {Natural Hazards},
  year = {2026},
  doi = {10.1007/s11069-025-07961-2},
  url = {https://doi.org/10.1007/s11069-025-07961-2}
}