Climate Change Trends During Two Periods in Hamedan and Tabriz

This study was carried out to investigate climate change at Hamedan-nozheh and Tabriz meteorological stations during two periods of 55 and 41 years ending to 2005, using nonparametric Mann-Kendall and parametric linear regression tests. Results indicated the upward trend of maximum temperature in Hamedan at annual scale and at late winter to early autumn in 55 years period. Increasing wind speed at annual scale, spring and summer and decreasing of the spring precipitation were occurred in this period. The minimum temperature had synchronous downward trend. In 41 years period, the maximum temperature was stable and decreasing minimum temperature trend was changed to upward trend. Also, the mean temperature at annual scale and summer and the sunshine hours at annual, winter, late summer and early autumn were increased. Noticeable changes in Tabriz climate were decreasing of precipitation at annual scale and winter, decreasing of the relative humidity throughout the year, decreasing of the wind speed at summer and increasing of the minimum, maximum and mean temperatures at annual scale and summer in 55 years period. In 41 years period, reference evapotranspiration had upward trend at winter, early spring and early autumn. The relative humidity and sunshine hours had synchronous downward and upward trends, respectively. Also, the minimum, maximum and mean temperatures had upward trends in some cases. Altogether, aridity index had downward trend in consequence of precipitation decrease and reference evapotranspiration increase in Tabriz that led to rise of climate aridity.