Bonacci et al. (2026) Assessing Drought Intensification with SPEI and NDI in Pazin, Istria (Northern Adriatic, Croatia)

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Identification

• Journal: Meteorology
• Year: 2026
• Date: 2026-02-05
• Authors: Ognjen Bonacci, Ana Žaknić‐Ćatović, Tamara Brleković, Tanja Roje-Bonacci, Anita Filipčić
• DOI: 10.3390/meteorology5010004

Research Groups

Not explicitly stated in the provided text, likely a regional meteorological or hydrological institute or a university department focused on climatology/hydrology in Croatia.

Short Summary

This study investigated drought intensification in the continental Istrian peninsula using the Standardized Precipitation Evapotranspiration Index (SPEI) and the New Drought Index (NDI), revealing a significant increase in mean annual air temperatures since the late 1990s and intensified drought conditions after 1985, with NDI showing higher sensitivity to temperature-driven processes.

Objective

• To investigate the intensification of drought in the continental part of the Istrian peninsula using the Standardized Precipitation Evapotranspiration Index (SPEI) and the New Drought Index (NDI).

Study Configuration

• Spatial Scale: Continental part of the Istrian peninsula, specifically using data from the main meteorological station in Pazin, Croatia.
• Temporal Scale: 64 years (1961–2024) of monthly data.

Methodology and Data

• Models used: Standardized Precipitation Evapotranspiration Index (SPEI), New Drought Index (NDI). Statistical methods included linear regression, Mann–Kendall test, and Rescaled Adjusted Partial Sums (RAPS) analysis.
• Data sources: Monthly precipitation and temperature data from the main meteorological station in Pazin (observational data).

Main Results

• A significant increase in mean annual air temperatures has been observed since the late 1990s, with particularly strong warming during summer months.
• Precipitation trends showed high variability but no statistically significant long-term decline.
• Both SPEI and NDI indicate an intensification of drought conditions after 1985.
• The NDI demonstrated stronger sensitivity to temperature rise compared to the SPEI.
• Seasonal analyses revealed that drought occurrence is most pronounced during the warm part of the year.
• Cumulative series suggest a shift from predominantly wet to predominantly dry conditions after the mid-1980s.
• The two indices showed a high degree of agreement, but NDI provided added value in detecting temperature-driven drought processes.
• The findings highlight a growing risk of more frequent and severe droughts, including potential flash drought events, in the humid regions of Istria.

Contributions

• Quantifies and confirms the intensification of drought conditions in the continental Istrian peninsula, a specific Mediterranean region, driven primarily by rising temperatures.
• Provides a comparative analysis of SPEI and NDI, demonstrating the enhanced sensitivity of NDI to temperature-driven drought processes, which is crucial for understanding climate change impacts.
• Offers valuable insights that can support the development of improved drought early-warning systems and adaptation strategies tailored for the Mediterranean context.

Funding

Not mentioned in the provided text.

Citation

@article{Bonacci2026Assessing,
  author = {Bonacci, Ognjen and Žaknić‐Ćatović, Ana and Brleković, Tamara and Roje-Bonacci, Tanja and Filipčić, Anita},
  title = {Assessing Drought Intensification with SPEI and NDI in Pazin, Istria (Northern Adriatic, Croatia)},
  journal = {Meteorology},
  year = {2026},
  doi = {10.3390/meteorology5010004},
  url = {https://doi.org/10.3390/meteorology5010004}
}