Characteristics of air temperature in Poland from 1994 to 2019 based on hourly data

Abstract

AbstractThis study was conducted to understand the characteristics of hourly air temperature across Poland over the period 1994–2019. For this purpose, hourly temperature observations from 38 stations were used. It was found that the average temperature at all stations in the period 2007–2019 (second half of data) is higher than that in the period 1994–2006 (first half of data). The increase in the average temperature in autumn was smaller than that in the other seasons. In the northern part of Poland, the increase in the average temperature in spring was more notable compared with that in the other seasons. In the southern part of Poland, the increase in the average temperature in winter and summer was more notable compared with that in the other seasons. At all stations, a statistically significant increasing trend in the average temperature was seen in the period 1994–2019. This trend was highest at Warszawa (0.067°C/year) and lowest at Kraków Balice (0.029°C/year). At all stations, the frequency of relatively low/high temperatures was lesser/higher in the period 2007–2019 compared with that in the period 1994–2006 indicating that temperature distribution has shifted toward a warmer climate. In comparison to the period 1994–2006, in the period 2007–2019, in the southern region of Poland, a large increase in the average number of hours per year above high percentiles and a large decrease in the average number of hours per year below low percentiles was observed. Also, it was found that warm/cold spells are becoming more/less frequent in Poland. In many stations, compared with the period 1994–2006, in the period 2007–2019, an increase in the length of the longest spell of hours above the 99th percentile and below the first percentile was observed.