Güler et al. (2026) Influence of teleconnection patterns on daily extreme precipitation in Turkey

Identification

• Journal: Theoretical and Applied Climatology
• Year: 2026
• Date: 2026-02-01
• Authors: Hakan Güler, Ecmel Erlat
• DOI: 10.1007/s00704-026-06056-7

Research Groups

• Department of Geography, Ege University, Bornova-Izmir, Turkey

Short Summary

This study investigates the relationship between four major teleconnection patterns (NAO, AO, NCP, EA) and the frequency and intensity of daily extreme precipitation across Turkey from 1950 to 2023. It finds that the North Atlantic Oscillation (NAO) is the dominant influence, particularly in western Turkey during winter and autumn, with distinct responses for extreme precipitation frequency versus intensity.

Objective

• To determine which teleconnection patterns affect the intensity and frequency of daily extreme precipitation in Turkey.
• To identify spatially consistent patterns between daily extreme precipitation indices and teleconnection patterns using a high-resolution gridded dataset.

Study Configuration

• Spatial Scale: Turkey, covered by 8055 grid cells at an approximate resolution of 9 km (0.1° × 0.1°).
• Temporal Scale: 74-year period (1950–2023), analyzed on annual and seasonal (spring, summer, autumn, winter) timescales.

Methodology and Data

• Models used: ERA5-Land reanalysis product (for precipitation data).
• Data sources:
  • ERA5-Land total precipitation dataset (hourly data aggregated to daily).
  • North Atlantic Oscillation (NAO) indices from the Climate Analysis Section of the US National Center for Atmospheric Research (NCAR).
  • Arctic Oscillation (AO) and Eastern Atlantic Pattern (EA) monthly indices from the National Centers for Environmental Prediction (NCEP)/NCAR.
  • North Sea-Caspian Pattern (NCP) index calculated for 1950–2023 using methods from Kutiel and Benaroch (2002).
• Statistical methods: Pearson correlation coefficient, two-tailed Student’s t-test (p < 0.05), Empirical Orthogonal Function (EOF) analysis.
• Extreme precipitation indices:
  • R95N, R99N: Annual or seasonal frequency of extreme precipitation events exceeding the 95th (99th) percentile threshold.
  • R95AM, R99AM: Cumulative precipitation amount from events exceeding the 95th (99th) percentile threshold.

Main Results

• The North Atlantic Oscillation (NAO) is the primary driver, explaining over 30% of the variance in the annual frequency of daily extreme precipitation (R95N).
• A negative NAO phase significantly correlates with increased frequency and amount of extreme precipitation, particularly in western Turkey during winter (17% of area for R95N) and autumn (15% for R95N).
• The Arctic Oscillation (AO) is the second most influential, showing significant correlations in winter (~17% of area for R95N/R95AM) and summer (~20–24% for all indices, especially in Central Anatolia).
• The North Sea-Caspian Pattern (NCP) and Eastern Atlantic Pattern (EA) have weaker and more seasonally constrained impacts; NCP shows maximum influence in summer (17% for R95N), and EA primarily affects spring precipitation (16–20% for R95N/R95AM).
• The influence of all teleconnections is strongest in winter, with western, Mediterranean-influenced regions being most sensitive.
• EOF analysis reveals that the frequency and intensity of daily extreme precipitation can respond differently to NAO variability, sometimes showing opposite correlations despite similar spatial EOF patterns (e.g., negative NAO phases lead to more frequent but lower total precipitation events in western Turkey, while positive NAO phases lead to less frequent but more intense events).

Contributions

• Provides the first systematic assessment of how four major teleconnection patterns simultaneously influence daily extreme precipitation indices across Turkey using a comprehensive high-resolution spatial dataset and combining correlation analysis with EOF decomposition.
• Reveals a novel finding that the NAO modulates the character of extreme precipitation events (frequency versus intensity) rather than just their overall occurrence.
• Offers valuable information for determining risk management strategies, improving disaster preparedness, and developing climate change adaptation strategies for extreme precipitation in Turkey.

Funding

The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.

Citation

@article{Güler2026Influence,
  author = {Güler, Hakan and Erlat, Ecmel},
  title = {Influence of teleconnection patterns on daily extreme precipitation in Turkey},
  journal = {Theoretical and Applied Climatology},
  year = {2026},
  doi = {10.1007/s00704-026-06056-7},
  url = {https://doi.org/10.1007/s00704-026-06056-7}
}