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Four Decades of Climate Change (1981–2020) in the South-Eastern Baltic Region: trends and spatial patterns of air temperature and precipitation extremes
The objective of the paper was the spatio-temporal analysis of the dynamics of extreme climate indices for the south-eastern coast of the Baltic Sea over the 40-year period 1981–2020, employing 10 extreme indices proposed by Expert Team (ET) on Climate Change Detection and Indices (ETCCDI), characterizing hazardous phenomena as: extremely high temperatures, heat waves and intense precipitation, and utilising climate data recorded at 9 meteorological coastal and inland stations. Extreme temperature indices were calculated using the ClimPACT software package, and trends were identified using the Mann-Kendall non-parametric test. The analysis showed a significant increase in warm temperature extremes across most stations, including summer days (SU), warm days (TX90p), and heatwave frequency (HWF) and duration (HWD) in the region. At the same time, the number of frost days (FD0) showed a significant decreasing trend at all stations, reflecting a general warming tendency. Precipitation-related indices showed weaker and more mixed trends. At the coastal station Baltiysk, number of very heavy rain days (R10mm) and total annual precipitation (PRCPTOT) showed significant decreases. In contrast, both number of very heavy rain days (R10mm) and (R20mm) increased at the south-western station Chojnice, while very heavy rain days (R20mm) also increased at the inland station Zheleznodorozhnyy in the central part of the region. Consecutive wet days (CWD) showed no significant changes. Pearson correlation analysis was used to quantitatively assess the influence of large-scale atmospheric circulation patterns — the Arctic Oscillation (AO), the North Atlantic Oscillation (NAO), the Scandinavia Pattern (SCAND), and sea surface temperature (SST). It has been shown that the AO (Arctic Oscillation) and sea surface temperature (SST) are closely associated with the interannual variability of temperature indices.