The evaluation of the incidence of extreme monthly precipitation totals across central-eastern Poland (1971–2020)

Abstract

This study investigates the temporal and spatial variability of extreme monthly precipitation sums in central- eastern Poland over the period 1971–2020. The analysis is based on records from six IMGW-PIB stations over a 50-year span. Monthly precipitation totals were examined using the Mann–Kendall trend test in conjunction with Sen’s slope estimator. Extreme value behaviour was assessed through the 95th and 99th percentiles and extreme value analysis (EVA) employing the Gumbel distribution. To identify common modes of variability, principal component analysis (PCA) was applied. The findings reveal substantial variability in monthly precipitation totals. The most pronounced extremes occurred in the summer months (July and August), whereas spring and autumn exhibited a lower frequency of extreme events. The highest risk of extreme precipitation and the greatest projected rainfall values (T2) were observed in Białowieża, Legionowo, and Pułtusk. Decadal analysis highlighted fluctuations ranging from deficit periods in the 1980s to relative stabilisation in the most recent decade (2011–2020). The Mann–Kendall test did not identify statistically significant trends for most months and stations, except for a notable increase in May precipitation at Szepietowo. Results of PCA confirmed a clear distinction between moderate extremes (P95) and the most intense episodes (P99), underscoring the dominant role of spring-summer P99 extremes in shaping overall precipitation variability across the region.