Çelik et al. (2026) Multi-index assessment of meteorological drought in Türkiye based on CHIRPS and TRMM data

Identification

• Journal: Climate Services
• Year: 2026
• Date: 2026-09-22
• Authors: Mehmet Ali Çelik, Zehra Işık, Dessalegn Obsi Gemeda
• DOI: 10.1016/j.cliser.2026.100730

Research Groups

• Geography Department, Faculty of Arts and Sciences, I˘gdır University, Türkiye
• Department of Geography, Nakhchivan State University, Azerbaijan
• Department of Natural Resource Management, College of Agriculture and Veterinary Medicine, Jimma University, Ethiopia
• New era and development in civil engineering research group, Scientific Research Center, Al-Ayen Iraqi University (AUIQ), Iraq

Short Summary

This study assessed the spatiotemporal patterns of meteorological drought in Türkiye using a multi-index framework (PCI, RAI, PNPI) and satellite precipitation data (CHIRPS, TRMM) from 1998-2019, revealing significant regional and interannual variability, with 2008 as an extreme drought year and 2018 as a very wet year, and demonstrating CHIRPS's superior accuracy after bias correction.

Objective

• To evaluate the spatial and temporal variability of meteorological drought across Türkiye using a multi-index framework (Precipitation Concentration Index (PCI), Rainfall Anomaly Index (RAI), and Percent of Normal Precipitation Index (PNPI)) based on CHIRPS and TRMM satellite-derived precipitation datasets.

Study Configuration

• Spatial Scale: National scale, covering the entire country of Türkiye.
• Temporal Scale: 22-year period from 1998 to 2019.

Methodology and Data

• Models used: Precipitation Concentration Index (PCI), Rainfall Anomaly Index (RAI), Percent of Normal Precipitation Index (PNPI).
• Data sources: Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS), The Tropical Rainfall Measuring Mission (TRMM) data, Turkish State Meteorological Service (MGM) provincial precipitation records (for bias correction and validation).

Main Results

• Precipitation distribution in Türkiye exhibits high spatial heterogeneity and pronounced interannual variability.
• In 2008, severe drought (PNPI <75%) and drought (PNPI 75–89%) conditions covered 38.3% and 47.8% of Türkiye, respectively, indicating that approximately 86.1% of the country experienced drought or severe drought.
• In contrast, in 2018, wet (PNPI 110–124%) and very wet (PNPI ≥125%) conditions covered 41.1% and 37.5% of Türkiye, respectively, indicating that approximately 78.6% of the country experienced wet or very wet conditions.
• The year 2008 was identified as an extreme drought year, with minimum spatial PNPI values reaching approximately 47% and RAI values reaching −2.70.
• The year 2018 represented a predominantly wet year at the spatial scale, with maximum spatial PNPI values reaching 174% and RAI values exceeding +3.36.
• After province-based bias correction, CHIRPS data showed superior accuracy (Pearson correlation coefficient (R) = 0.990; Root Mean Square Error (RMSE) = 4.13 mm/month) compared to TRMM (R = 0.963; RMSE = 7.89 mm/month) when validated against MGM observations.
• PCI values generally ranged between 8.7 and 28.6, showing a clear north-south gradient with higher precipitation concentration in southern regions.
• The country-wide mean annual precipitation trend for 1998-2019 showed a slightly positive Sen's slope of 1.78 mm/year, but 94.44% of pixels did not exhibit statistically significant trends.

Contributions

• This study provides an integrated evaluation of two widely used satellite-based precipitation datasets (CHIRPS and TRMM) through a multi-index framework (PCI, PNPI, and RAI) at the national scale in Türkiye.
• It offers a comprehensive comparison of satellite datasets while simultaneously examining different dimensions of meteorological drought, thereby improving the assessment of spatial drought variability across diverse climatic and topographic regions.
• The combined multi-index and multi-dataset approach enables a more robust assessment of dry and wet conditions and enhances the identification of spatial heterogeneity and temporal variability in precipitation.
• The findings provide spatially explicit information that can support drought surveillance and climate-informed decision-making, particularly in areas with limited ground-based observations.

Funding

This research received no specific grant from any funding agency.

Citation

@article{Çelik2026Multiindex,
  author = {Çelik, Mehmet Ali and Işık, Zehra and Gemeda, Dessalegn Obsi},
  title = {Multi-index assessment of meteorological drought in Türkiye based on CHIRPS and TRMM data},
  journal = {Climate Services},
  year = {2026},
  doi = {10.1016/j.cliser.2026.100730},
  url = {https://doi.org/10.1016/j.cliser.2026.100730}
}