Wintertime cold and warm spells in the eastern part of the Baltic Sea region

One of the most important uncertainties in a changing climate conditions are changes in climate extremes. While precipitation extremes are particularly important at low latitudes, thermal extremes are of major interest at mid-latitudes. This study analyses the cold (CS) and warm (WS) spells winter climatology in the eastern part of the Baltic Sea region from 1951 till 2020. Data from the E-OBS database were used in the research. A CS/WS in this study is an event when extreme low/high (below 10th/above 90th percentile) air temperature persists for at least 5 days. The period 1971–2000 was used as the climate norm. The results show that both absolute winter air temperature minimum and maximum increased over the investigation period. The absolute maximum of winter air temperature strongly increased after 1988, when a statistically significant regime shift was determined. The results show that the number of WSs has increased and changes are statistically significant in most cases. Meanwhile, the recurrence and duration of CSs have changed insignificantly, although the number of years with more than one CSs is decreasing. The total number of CS/WS cases per season slightly increased. Total number of WSs days increased a lot at the last decade of the investigation period, while the number of CSs days changed insignificantly in recent several decades.