Bartczak et al. (2026) Dry and wet periods in north-central Poland in the years 1952–2020

Identification

• Journal: Acta Geophysica
• Year: 2026
• Date: 2026-03-28
• Authors: Arkadiusz Bartczak, Zbigniew Podgórski, Andrzej Araźny, Halina Kaczmarek, Sebastian Tyszkowski
• DOI: 10.1007/s11600-026-01854-z

Research Groups

• Faculty of Geographical Sciences, Kazimierz Wielki University, Bydgoszcz, Poland
• Department of Environmental Resources and Geohazards, Institute of Geography and Spatial Organization, Polish Academy of Sciences, Toruń, Poland
• Department of Meteorology and Climatology, Faculty of Earth Sciences and Spatial Management, Nicolaus Copernicus University, Toruń, Poland
• Centre of Climate Change Research, Nicolaus Copernicus University, Toruń, Poland

Short Summary

This study quantifies dry and wet periods in north-central Poland from 1952–2020, investigating their correlation with atmospheric circulation and climatic variables. It reveals statistically significant trends of increasing potential evaporation (+27.8 mm per decade) and decreasing Climatic Water Balance (-29.6 mm per decade), with dry periods linked to anticyclonic circulation and wet periods to cyclonic circulation.

Objective

• To quantify the number, duration, and intensity of dry and wet periods in north-central Poland during 1952–2020.
• To explore the correlations of these periods with atmospheric circulation types and selected climatic elements: precipitation, potential evaporation, and Climatic Water Balance (CWB).

Study Configuration

• Spatial Scale: North-central Poland, specifically the Zgłowiączka River catchment (1491.8 km²) and Skrwa Lewa River catchment (367.4 km²). Data from three meteorological stations (Koło, Płock, Toruń) and two river gauging stations.
• Temporal Scale: 1952–2020 for most data; 1961–2020 for Skrwa Lewa River discharge. Analyses performed for annual and monthly data, presented in relation to the hydrological year (1 November to 31 October).

Methodology and Data

• Models used:
  • Ivanov method for monthly potential evaporation.
  • Linear trend function for assessing changes over time.
  • General Box-Cox procedure for transforming hydrological series to approximate a normal distribution.
  • Standardised Streamflow Index (SSI) for identifying dry and wet periods, calculated for 1, 3, 6, and 12-month moving windows.
  • Spearman’s rank correlation coefficient for assessing correlations between variables.
  • t-test for statistical significance of Spearman’s rank correlation coefficients.
  • Mann–Kendall test for trend analysis of atmospheric circulation indices.
• Data sources:
  • Meteorological and hydrological data from the Institute of Meteorology and Water Management National Research Institute (IMGW-PIB, Poland).
  • Daily surface synoptic maps from the German Meteorological Service (Deutscher Wetterdienst) for atmospheric circulation types.
  • Atmospheric circulation indices (zonal (W), meridional (S), and cyclonicity (C)) derived from a unique calendar of circulation types for the Bydgoszcz-Toruń region.

Main Results

• Annual potential evaporation in north-central Poland exhibited a statistically significant upward trend of +27.8 mm per decade from 1952–2020.
• Annual Climatic Water Balance (CWB) showed a statistically significant downward trend of −29.6 mm per decade from 1952–2020.
• Annual precipitation totals did not display a statistically significant trend over the study period.
• A significant correlation was found between the cyclonicity index (C) and the Standardised Streamflow Index (SSI) for both rivers and all moving windows, indicating dry periods under anticyclonic circulation and wet periods under cyclonic circulation.
• No significant correlation was generally observed between meridional (S) or zonal (W) circulation indices and the SSI.
• The SSI showed positive and statistically significant correlations with precipitation, negative correlations with potential evaporation, and the strongest positive correlations with CWB across all moving windows.
• Correlation coefficients generally strengthened with longer moving windows (SSI-1 to SSI-12), reflecting the influence of seasonal variability.
• The mean annual specific discharge for the Zgłowiączka River (1952–2020) was 2.33 dm³ s⁻¹ km⁻², with no statistically significant trend.
• The mean annual specific discharge for the Skrwa Lewa River (1961–2020) was 2.89 dm³ s⁻¹ km⁻², with a statistically significant decreasing trend.
• The number of identified dry and wet periods decreased consistently with increasing length of the SSI moving window, while the duration of individual periods generally increased.

Contributions

• Provides a comprehensive quantification of dry and wet periods (number, duration, intensity) in north-central Poland over a 69-year period (1952–2020) using the Standardised Streamflow Index (SSI).
• Establishes robust statistical correlations between these hydroclimatic periods and specific atmospheric circulation types (cyclonicity), as well as key climatic variables (precipitation, potential evaporation, CWB).
• Highlights the significant impact of increasing potential evaporation and decreasing Climatic Water Balance on regional water resources, even in the absence of a statistically significant trend in precipitation, underscoring the role of rising temperatures.
• Utilizes a unique regional atmospheric circulation classification, enhancing the specificity of the findings for north-central Poland.
• Contributes to the understanding of regional hydroclimatic dynamics in a transitional climate zone, offering valuable insights for water resource management and climate change adaptation strategies.

Funding

There was no specific grant for this research from any funding source.

Citation

@article{Bartczak2026Dry,
  author = {Bartczak, Arkadiusz and Podgórski, Zbigniew and Araźny, Andrzej and Kaczmarek, Halina and Tyszkowski, Sebastian},
  title = {Dry and wet periods in north-central Poland in the years 1952–2020},
  journal = {Acta Geophysica},
  year = {2026},
  doi = {10.1007/s11600-026-01854-z},
  url = {https://doi.org/10.1007/s11600-026-01854-z}
}