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Changes in thermal extremes in Poland

Graczyk D., Kundzewicz Z. W.

Acta Geophysica

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2014

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Vol. 62, no. 6

1435--1449

EN

Changes in thermal extremes of the climate of Poland in 1951-2010 are examined. Warm extremes have become more frequent, while cold extremes have become less frequent. In the warming climate of Poland, the increase in the number of extremely warm days in a year and the decrease in the number of extremely cold days in a year have been observed. Also the increase of the maximum number of consecutive hot days in a year and the decrease of the maximum number of consecutive very cold and extremely cold days in a year have been observed. However, the trends are not of ubiquitous statistic significance, as the natural variability is strong.

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Fale chłodu i ciepła w przebiegu rocznym temperatury powietrza w Warszawie (1951-2010)

Stopa-Boryczka M., Boryczka J.

Przegląd Geofizyczny

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2011

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Z. 3-4

181-200

PL

Artykuł dotyczy fal ochłodzeń i ociepleń w przebiegu rocznym temperatury powietrza, które rozpatrzono na podstawie średnich 60-letnich (1951-2010) wartości dobowych z Warszawy Okęcia. Badanie dotyczy ochłodzeń majowych ("zimni święci"), ochłodzenia czerwcowego ("monsun europejski"), ocieplenia jesiennego ("babie lato") oraz sprawdzalności przysłowia dotyczącego temperatury w grudniu (4 i 25 XII). Cykle temperatury powietrza, tj. okresy, amplitudy i fazy, wyznaczono metodą "sinusoid regresji". Na uwagę zasługują cykle 15,2-18,3 dni występujące we wszystkich miesiącach roku; w przybliSeniu 15 dni - w styczniu i listopadzie, 16 dni - w marcu, kwietniu, maju, sierpniu, wrześniu i październiku, 17 dni - w czerwcu i grudniu oraz 18 dni w lutym i lipcu. Fale chłodu i ciepła są wynikiem interferencji cykli o długości kilku i kilkunastu dni temperatury średniej dobowej oraz cykli wieloletnich temperatury średniej miesięcznej. Fale chłodu i ciepła opisano przez odchylenia (reszty) ei wartości zmierzonych temperatury Ti od sinusoidy regresji przebiegu rocznego.

EN

The presented paper deals with cold and warm waves in yearly course of air temperature. These waves were analysed on the basis of 60-year (1951-2010) mean values from meteorological station Warsaw Okęcie. Investigation refers to cold waves in May ("Ice Saints"), "European monsoon" in June, autumnal warming (in Poland called "old woman summer") as well as to verification of Polish proverb dealing the air temperature in December 4th (Barbara) and December 25th (Christmas). Air temperature cycles, i.e. periods, amplitudes and phases, were calculated by using method of "regression sinusoid". Authors stated that 15,2-18,3 day cycles occurred in every months: about 15 days in January and November, about 16 days in March, April, May, August, September and October, about 17 days in June and December, about 18 days in February and July. The cold and warm waves are a result of interference of several days cycles in monthly course of the daily mean temperature and of several years cycles in multiannual course of the monthly mean temperature. The cold and warm waves are described by deviations (rests) e. of measured temperature values T from regression sinusoid of multiannual yearly course.

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Fale termiczne nad Polską w zimie w zależności od pola wiatru w Europie

Degirmendzić J.

Przegląd Geofizyczny

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2004

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Z. 1-2

11-23

EN

The main goal of this paper is to analyze transformation of wind field over Europe associated with change of intensity of thermal wave in Poland during winter. Thermally anomalous periods were distinguished on the basis of daily mean temperature record at 52.5°N, 20°E grid point. Wind field was defined by meridional and zonal wind components. Both, temperature and wind data were retrieved from NCEP/NCAR Reanalysis. The analysis was performed for the period of 1950-2001 and 850 hPa isobaric level. Cold/heat waves were categorized into three thermal classes - extreme, moderate and weak. In order to analyze wind field the following parameters were employed: relative vorticity, wind speed and directional steadiness of wind vector. Additionally, the structure of streamlines was analyzed. Temperature rise in Poland is forced by the development of dipole-like structure, clearly seen on the map of anomalies of relative vorticity. Positive anomalies are situated over Norwegian See, eastern Atlantic and Scandinavia, while negative vorticity advection is observed in southern Europe. Simultaneously with dipole development the increase of wind speed in middle Europe is also noted - supposedly it constitutes significant feature of wind field responsible for temperature increase in Poland in winter. In case of extreme heat waves the source region of warm advection is shifted southwards. Streamline pattern indicates more parallel flow over the Atlantic to the Iberian Peninsula and change of wind direction over Poland, from westerly to south-westerly. Intensive transport of heat over the northern Europe reduces temperature contrast at the Mediterranean front, which consequently decelerates western flow and lowers directional steadiness of wind vector down to 50% over the southern part of continent. Field of vorticity anomalies corresponding to the cold waves occurrence over Poland posseses dipole-like structure, however its polarization is reversed. Anticyclonic vorticity advection occurs in northern Europe and northern Atlantic while southern Europe experiences increase of cyclonic vorticity. Cooling in central Europe is associated with transformation of circulation field into blocking type - simultaneously the source region of cold advection shifts northwards over the Scandinavia (around 70°N). Enhanced thermal contrasts over southern Europe together with air masses inflow from the north, i.e. possessing surplus of cyclonic vorticity, strengthen the Mediterranean front.