Trends of meteorological parameters and reference evapotranspiration in the northern Zagros region

In order to test the hypothesis of connection between the changes in climatic parameters and declining northern Zagros forests in the west of Iran, long-trends of meteorological parameters and reference evapotranspiration (ET0) on seasonal and annual time scales using three synoptic meteorological stations of Piranshahr, Saghez, and Khoram-Abad were examined. The Penman-Monteith combination equation was applied to calculate the ET0. To examine the long-term trends of meteorological parameters and ET0, the non-parametric tests of Mann-Kendal and Spearman were used and the significance of the slope of trends lines was tested using the Sen-slope estimator. Results showed that the increasing trends of air temperature in Piranshahr (1986-2009) were statistically significant (P