Rainfall trends in arid and semi-arid regions of Iran

Time-series of annual rainfall, number of rainy-days per year and monthly rainfall of 20 stations were analyzed to assess climate variability in arid and semi-arid regions of Iran. The results showed mixed trends of increasing and decreasing rainfall, which were statistically significant (p<0.05 and p<0.01) only for Sabzevar and Zahedan stations by the Mann–Kendall test. Also, with the exception of Kashan and Torbat stations there was no statistically significant trend in the mean number of rainy-days per year. Increasing and decreasing monthly rainfall trends were found over large continuous areas in the study region. These trends were statistically significant mostly during the winter and spring seasons, suggesting a seasonal movement of rainfall concentration. Results also showed that there is no significant climate variability in the arid and semi-arid environments of Iran.