The air temperature in cracow from 1826 to 1990: Persistence, fluctuations and the urban effect

Abstract

AbstractMean monthly air temperatures in Cracow for the period 1826–1990 were used. The temperatures of the coldest (Tlow) the warmest (Thigh) periods of the year, and mean annual temperatures (Ta), were calculated. The persistence of temperatures was examined using the correlation coefficients between monthly temperatures in succeeding months. A significant temperature persistence was found for a cold season (December‐March) and also for the summer (July‐August). Long‐term fluctuations were analysed by means of 20‐year and 30‐year running mean values and the positive and negative squared deviations of moving 20‐year subperiods. Two warm stages were found. One at the beginning of the present century, the second at the end of the period analysed. The first warm phase was connected with a decrease in the degree of continentality. Warm phases were also linked with a decrease in the temperature variability.The spectrum and the moving spectrum in 40‐year subperiods of monthly and annual temperature records were calculated. An 8‐year period was found in Tlow, Ta, and in the monthly series of the cold season, and 4‐ and 5‐year periods were found in Thigh and in the monthly series of the warm season.By comparing the temperature in Cracow with that at the neighbouring stations of Wieliczka, Bochnia, and Tarnów, it was found that the difference in annual means increased from −0.3°C at the end of the previous century to 1.0°C in the last two decades. About 0.5°C of this increase occurred in the last 40‐year period of abrupt expansion and industrialization of the city of Cracow.