Trend Analysis of Monthly and Annual Mean Temperature of the Northern Half of Iran Over the Last 50 Years

The temperature is one of the essential elements in formation of climate and its changes can alter the climate of each region, Therefore study of temperature changes at different spatial and temporal scales is devoted a large part of research to climatology. The mean temperature changes of the northern half area of Iran (18 Synoptic stations) in monthly or annual scales (1961-2010) are tested with using non-parametric Mann-Kendall test and elimination of all auto-correlation coefficients. To determine the slope of temperature gradient, the Sen’s slope estimation method was used. The results showed that 61% of the stations have experienced a significant increase in annual scale, in expect of Urmia, Zanjan, Qazvin and Gorgan stations. Arak is also a significant decrease, Torbate Heydarie and Saghez have experienced non-significant negative trend in annual scale. In monthly scale, number of months with increasing trend was greater than decreasing trend. April, September and October have significant increasing trend in most stations. December has lowest changing in compare with others. In conclusion, the studied temperature area in past half century 1.15 C is increased