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Abstract: Study of air temperature in the upper basin of Barlad river (eastern Romania), during 1964 – 2007 period, indicates an increasing trend. Data from Negresti meteorological station, the only one in the studied area, and also from other two surrounding stations, Iassy and Vaslui, are analysed. To find the most appropriate expression of the annual mean temperature interannual evolution, different statistical procedures are used: regression models, Runs test and cumulative curve of the temperature standardized anomaly. The parametric analysis with regression models shows significant increasing trends, the quadratic trend model providing a better fit than the linear and exponential models. According to the quadratic model, the temperature increased with 0.9°C at Negresti and Vaslui and with 1°C at Iassy. In the non-parametric analysis the Runs test is used in order to verify if the temperature variation are caused by trend/oscillation and mixture/clustering in the data. At all the three meteorological stations, the results of Runs test, based on the number of runs above/below the median and on the number of runs up or down, did not clearly detect neither a cluster or mixture in the data nor a trend or an oscillation, because all the p-values obtained are below α-level (0.05). The shape of the cumulative curve suggests that the increasing tendency of the annual mean temperature and the observed fluctuations represent a microcycle. The results are emphasizing the idea that a micro-oscillation, connected with the natural variability of the climate, is more properly than a linear trend. Therefore, it is very probably that the temperature increasing is not an anthropic-induced linear process since 1964 until 2007, it is rather representing the ascensional part of a natural micro-oscillation, which is impelled in the last few years by the anthropical interventions on the environment.

Keyword: annual mean temperature, quadratic trend, Runs test, temperature standardized anomaly, microcycle