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The evolution of annual global solar radiation (GSR) and precipitation trends in the Cluj-Napoca area was analyzed for the period 1921 to 2009. In this study, we used data from Cluj-Napoca meteorological station and, also, from other two surrounding stations, Bistrița and Sibiu. Linear model and significance test method (Student’s t-test) were used to find the most appropriate expression of the annual mean GSR and average amount of precipitation interannual evolution. Global solar radiation showed an increasing trend for this period being statistically significant at 0.001 level only at Cluj-Napoca and Bistrița stations. There is no statistically significant trend in precipitations for this period. According to the linear model, the GSR increased with 8.241 W/m2 at Cluj-Napoca, 9.149 W/m2 at Bistrița and 2.581 W/m2 at Sibiu, while the amount of precipitations showed increasing trends for Cluj-Napoca (with 55.3 mm) and Bistrița (with 23.4 mm) and decreasing trend for Sibiu (with 11.1 mm) but these ones not being statistically significant. The significant increasing trend of the global solar radiation is rather the ascensional part of a natural micro-oscillation due to solar variations. The values of Pearson''''s correlation for Sibiu (r = - 0.33) and Bistrița station (r = - 0.31) and the 99% probability of making a correct statement for annual (p = 0.01) show that there is a correlation (negative relationship) between annual mean global solar radiation and annual mean precipitations. The value of Pearson''''s correlation for Cluj-Napoca (r = - 0.15) is not statistically significant.

Key words: Global solar radiation; annual mean precipitation; linear trend model; t-test; Pearson’s correlation.