Cold Waves in Poznań (Poland) and Thermal Conditions in the City during Selected Cold Waves

Abstract

Abstract:The objective of the paper was to characterize the occurrence of cold days and cold waves in Poznań in the years 1966/67-2015/16, as well as to characterize thermal conditions in the city during selected cold waves in the years 2008/09-2015/16. The study was based on daily data on maximum and minimum air temperature for station Poznań-Ławica from the years 1966/67-2015/16 and daily air temperature values from eight measurement points located in the territory of the city in different types of land use from the years 2008/08-2015/16. In addition, to characterize thermal conditions during selected days forming cold waves, satellite images were used, on the basis of which the land surface temperature (LST) was calculated. A cold day was defined as a day with daily maximum temperature (Tmax) below the value of 5th annual percentile of Tmax, and a cold wave was defined as at least five consecutive cold days. The study showed an increase in Tmax in winter, which translated to a decrease in the number of cold days over the last 50 years, although the changes were not statistically significant. Thermal conditions in the city showed high variability in the winter season and during the analyzed cold waves.

Cold spells in Poland and Germany and their circulation conditions

“…In the multi‐annual course, a high number of long‐lasting cold spells that occurred throughout the study area concerned winters: 1969/1970, 1984/1985, 1995/1996, 2010/2011. The occurrence of strong cold spells in the aforementioned winter seasons was also pointed out in earlier studies (Krzyżewska, ; Tomczyk et al, ).…”

“…A decrease in the number of cold days in the south of Germany and in Bremen and Magdeburg has been proven and it was fastest and statistically significant only in Regensburg. A decrease in the frequency of cold days and cold spells was also mentioned by other authors, but the differences in their results come from the adopted methodological assumptions (Lhotka and Kyselý, ; Tomczyk, ; Owczarek and Filipiak, ; Tomczyk et al, ). The lack of a spectacular decrease in frequency of cold extremes in Central Europe despite contemporary warming contributes to suggestions by Francis and Vavrus (, ), Cohen et al (), Vavrus et al (), and others, concerning the increasing frequency and persistence of extreme weather conditions (including the occurrence of severe winters) at midlatitudes, which they link to changes in tropospheric circulation—specifically to an increasing amplitude of Rossby waves, possibly due to the decreasing thermal difference between the Arctic and midlatitudes (Arctic amplification).…”

Quantifying Thermal Stress for Sport Events—The Case of the Olympic Games 2020 in Tokyo

“…Readings from an individual meteorological station can be hardly representative for a whole city or urban area, like Tokyo. All of the input parameters to the thermal indices as well as the indices themselves are modified significantly by the urban environment and show strong variation in short distances of few meters [28,29]. However, the general background conditions and the temporal variation in day and year can be seen from the readings and for keeping the study simple only one station was used.…”

Understanding the Impacts of Climate Change on Health to Better Manage Adaptation Action

“…There are further research papers addressing the effects of temperatures on health in this issue, including analyses on heatwaves and cold spells, and reduced productivity in relation to heat. Two of the papers in this special issue focus on the incidence of heatwaves [17] and cold spells [18] over a 50 year period in the city of Poznan, Poland. The authors highlight how the diversity of land type is reflected by diverse thermal conditions across the city compared with the reference monitoring stations, and the increased frequency of heatwave and reduced frequency of cold spells over the period studied.…”