Multiannual variation of thermal specific days in Warsaw (1951 – 2010)

The paper focuses on the frequency, annual pattern and long-term variability of thermal specific days in Warsaw during the period 1951 – 2010. The following were distinguished: days with frost ( tmax ≥ 0.0 °C, tmin < 0.0 °C ), cold days ( t_max –0.1 – –10.0°C ), very cold days ( t_max – 10.1– – 20.0 °C ), extremely cold days ( t_max < –20.0°C ), hot days ( t_max 25.1–30.0 °C ), very hot days ( t_max 30.1–35.0 °C ) and extremely hot days ( t _max > 35.0 °C ) as well as warm nights ( t _min 15.1 – 18.0 °C ), very warm nights ( t _min 18.1 – 20.0 °C ) and tropical nights ( t _min > 20.0 °C ). The following average numbers of days/nights per year were found during the period 1951 – 2010: 109 days with t _min < 0.0°C, including 37 days with t _max < 0.0°C, 38 days with t_max > 25°C, and 21 nights with t _min > 15.0 °C. The minimum temperature ranged from –30.7 °C to 21.8 °C and the maximum temperature from –20.4 °C to 36.4 °C. The number of days with t_max ≥ 0.0 °C and t_min < 0.0 °C dropped by 1.8 day/10 years, days with t _max < 0.0 °C also by 1.8 day / 10 years; the number of days with t _max > 25.0 °C rose by 2.2 day / 10 years, while the number of days with t _min > 15.0 °C rose by 2.4 day / 10 years. The results are based the on data collected at the Okęcie airport station, which is located outside the town and therefore they are not representative of the Warsaw urban area, but rather of the eastern part of the Warsaw basin.

Zarys treści: W opracowaniu rozpatrzono częstość, przebieg roczny i zmiany wieloletnie tzw. termicznych dni charakterystycznych w Warszawie w latach 1951 – 2010. Wyróżniono: dni przymrozkowe, mroźne, bardzo mroźne i skrajnie mroźne; dni gorące, upalne i bardzo upalne oraz noce ciepłe, bardzo ciepłe i tropikalne. Stwierdzono, że w 60-leciu 1951 – 2010 dni z t _min < 0,0 °C było średnio w roku 109, w tym dni z t _max < 0,0 °C – 37, dni z t _max > 25 °C było
średnio 38, a nocy z t _min > 15,0 °C – 21. Temperatura minimalna wahała się od –30,7 °C do 21,8 °C, temperatura maksymalna od –20,4 °C do 36,4 °C. W 60-leciu 1951 – 2010 liczba dni z t _max ≥ 0,0 °C i t_min < 0,0 °C zmniejszała się o 1,8 dnia/10 lat, dni z t _max < 0,0 °C również o 1,8 dnia/10 lat; liczba dni z t _max > 25,0 °C zwiększała się o 2,2 dnia/10 lat, z t _min > 15,0 °C o 2,4 dnia / 10 lat. Uzyskane wyniki są oparte na danych pochodzących ze stacji położonej na lotnisku Okęcie, poza miastem, nie są zatem reprezentatywne dla obszaru miejskiego Warszawy, ale dla obszaru wschodniej części Kotliny Warszawskiej.

Multiannual variation of thermal specific days in Warsaw (1951 – 2010)

The paper focuses on the frequency, annual pattern and long-term variability of thermal specific days in Warsaw during the period 1951 – 2010. The following were distinguished: days with frost ( tmax ≥ 0.0 °C, tmin < 0.0 °C ), cold days ( t_max –0.1 – –10.0°C ), very cold days ( t_max – 10.1– – 20.0 °C ), extremely cold days ( t_max < –20.0°C ), hot days ( t_max 25.1–30.0 °C ), very hot days ( t_max 30.1–35.0 °C ) and extremely hot days ( t _max > 35.0 °C ) as well as warm nights ( t _min 15.1 – 18.0 °C ), very warm nights ( t _min 18.1 – 20.0 °C ) and tropical nights ( t _min > 20.0 °C ). The following average numbers of days/nights per year were found during the period 1951 – 2010: 109 days with t _min < 0.0°C, including 37 days with t _max < 0.0°C, 38 days with t_max > 25°C, and 21 nights with t _min > 15.0 °C. The minimum temperature ranged from –30.7 °C to 21.8 °C and the maximum temperature from –20.4 °C to 36.4 °C. The number of days with t_max ≥ 0.0 °C and t_min < 0.0 °C dropped by 1.8 day/10 years, days with t _max < 0.0 °C also by 1.8 day / 10 years; the number of days with t _max > 25.0 °C rose by 2.2 day / 10 years, while the number of days with t _min > 15.0 °C rose by 2.4 day / 10 years. The results are based the on data collected at the Okęcie airport station, which is located outside the town and therefore they are not representative of the Warsaw urban area, but rather of the eastern part of the Warsaw basin.