Cold spells in the city of Poznań and their circulation conditions

Abstract

This study analyzed the occurrence of cold days, very cold days and cold spells in Poznań in the years 2008/09-2022/23. A cold day was defined as a day with Tmax < 0.0 °C and ≥-10.0 °C, whereas a very cold day was defined as a day with Tmax <-10.0 °C. In the next step, cold spells were determined, which are sequences of at least 5 days with Tmax < 0.0 °C. Circulation conditions were determined based on daily values of sea-level pressure, the height of the 500 hPa isobaric surface, as well as their anomalies and air temperature anomalies at the 850 hPa isobaric level. The conducted research showed a decrease in the number of cold and very cold days in Poznań in the years 2008/09-2022/23. A variation in the number of cold and very cold days and cold spells was noted across the city area, which is a consequence of the form of land use. The occurrence of cold spells in Poznań was associated with higher than average sea-level pressure.