An analysis of trends of mean monthly temperature and precipitation totals in Poland in the period 1951-2000 was carried out. Areal means of temperature and precipitation were used, averaged for 51 meteorological stations evenly distributed within Poland's borders. Sensitivity of air temperature and precipitation variations towards circulation was assessed. Circulation variations were expressed by sea-level pressure in the 52.5°N, 20°E grid point and geostrophic wind calculated from meridional (45-60°N) and latitudinal (10-30°E) pressure gradients.It was shown that the circulation factor explains up to 77% and 44% of temperature and precipitation variance respectively. Significant upward trends of temperature in March and May were detected. Also, the precipitation total in March was on the increase. The last decade of the 20th century was slightly 'too warm' in comparison with the circulation-induced temperature level, as well as with the temperature change scenario according to HadCM2 GS model.An attempt was made to evaluate the contribution of the frequency of snow cover occurrence to the temperature increase in winter, i.e. the temperature-albedo feedback.

Mean monthly values of the zonal index of surface pressure for the zone 35"-65"N during the period 1899-1990 are studied. The extreme values -11.5 hPa in February 1947 and 16.5 hPa in January 1978 define the range of zonal index variability. The highest annual value occurred in 1990. O n average, the maximum of zonal index occurs in October (mean value 7.5 hPa), the minimum in May (2.5 hPa). Spectral variance analysis shows 2-month, 3-month, 6-month, annual, quasi-biennial, and 13.2-year cyclicity in time series of monthly values. The quasi-biennial and 13-year cyclicity appear also in seasonal values of the zonal index.Instability of the zonal index spectra and autocorrelation for monthly values has been noted. The period under study is divided into three subperiods characterized by high (1899-1938 and 1972-1990) and lowThe correlation and correspondence between zonal index and air temperature changes of the Northern Hemisphere zonal indexes.and over Europe has been also examined.

The correlation coefficients between air temperature, precipitation, and geopotential heights of the 500 hPa level for six stations in Europe, located along the 20"E meridian from Scandinavia to Greece, for the period of 1951-1985 are calculated. The fields of correlation coefficients for each station and season are described. It is observed that the correlation coefficients of temperatures are, as a rule, significantly greater than for precipitation. How meridional and zonal circulation determine temperatures and precipitation has been examined.

The influence of general hemispheric circulation on European temperature and precipitation was investigated. Data from the period 1901-1976 were utilized: the monthly frequencies of Occurrence of W, E, C circulation pattern types according to the Wangenheim-Girs classification, monthly values of pressure differences between 35" an 65"N (zonal index), mean temperatures of January and July at 30 stations in both the warm season (May-October) and the cold season (November-April) and semi-annual precipitation totals for 21 stations in Europe. The correlation coefficients between the circulation characteristics and climate elements indicated above in Europe were calculated.Maps of these correlation coefficients have been produced, with the areas of their statistical significance. The results show that variability of temperature, and also partly of precipitation in Europe are significantly correlated with changes of circulation pattern types. January temperature also depends on the zonal index.If it is assumed that in future, until the end of this century, an increase of W type frequency and a decrease of C circulation pattern types will take place-it may be expected that temperature and precipitation will undergo appropriate changes in certain parts of Europe. Northern and some central areas of Europe are likely to change from continental to Oceanic climate as. regards temperature; precipitation is likely to increase in northern Europe.

Mean monthly air temperatures in Cracow for the period 1826-1990 were used. The temperatures of the coldest (Tow) the warmest (Thigh) periods of the year, and mean annual temperatures (T'.), 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 werecalculated. An 8-year period was found in Tow, T,, 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 Tarnow, it was found that the difference in annual means increased from -0.3"C at the end of the previous century to 1 . 0 T in the last two decades. About 05°C of this increase occurred in the last 40-year period of abrupt expansion and industrialization of the city of Cracow.KEY WORDS Cracow Warm and cold stages Urban heat island Poland THE 'HISTORICAL' METEOROLOGICAL OBSERVATORY IN CRACOW Meteorological measurements at Cracow, as at the other oldest meteorological stations in central Europe, began in the late eighteenth century-in 1792. However, the uninterrupted and homogeneous, as far as thermometer location is concerned, series of temperature measurements began in 1826. From that time till the present the thermometers were situated on the northern side of the building of Sniadecki Collegium of the Jagiellonian University at a height of 12 m above the ground. The nearest buildings are 150 m away. At the beginning there were two thermometers located, outside the window, so that the readings were always made in the shade. Since 1836 a louvered box protecting the thermometers against direct solar radiation has been used.