عنوان مقاله [English]
Climatic changes and increase of air temperature is considered as one of the important environmental issues of the world wide .Climatic changes in certain regions can be detected by studying the mean air temperature. the researches made in the world mainly indicate the gradual increase of mean air temperature .In this study, to identify the temporal changes in temperature (minimum, maximum, mean), the observations (1956-2005) of 10 meteorological stations distributed in arid and semi-arid regions were applied. In this study, linear regression method and with respect to non-linear nature of climatic elements, non parametric Mann-Kendall method was used, which shows approximately similar results. The results of the two statistical periods showed that in maximum temperature about 70% of the stations and in the mean and minimum temperature about 90% of the stations showed an annual meaningful and positive trend . Most of changes, among the five study decades, with the amount of 49% has been occurred at the third and fourth decades. . The increasing trend of temperature is more visible for monthly minimum nocturnal temperatures. Exceptionally, Birjand exhibited decreasing (negative) trend for few months.