An Investigation on Trends of Annual and Seasonal Rainfall and Temperature in Different Climatologically Regions of Iran

Climate change is defined as long term and irreversible changes in the climatic behavior of a region. Many studies have been conducted in different regions of the world on climate change. The results of these studies show considerable changes in climatic factors especially in precipitation and temperature. In this research، the trend of changes in annual and seasonal rainfall and temperature in 24 synoptic stations over a 50-year data period (1956-2005) was investigated in Iran. The Mann- Kendall test and linear regression technique were used to analyze the trend of changes in climatic factors. The results showed both increasing and decreasing trends in annual rainfall at various regions of Iran. Annual rainfall in northern slopes of Alborz and western slopes of the Zagros Mountain as well as in eastern and southeast parts of Iran had a decreasing trend while in the central of Iran the trend of changes was increasing. In southern region of Iran the rainfall had an increasing trend. The results also showed that temperature in most of the studied stations over the considered period was increasing. The highest and lowest changes in temperature were seen in the mean temperature of summer and winter، respectively. Ahwaz and Khorramabad stations had a decreasing trend and over all seasons would go toward more cooling. The temperature trend in Oromiye was decreasing in autumn and summer while Shahrekord and Bandar abbas had the same trend in summer and winter.