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 behaviorof a region. many studies have been conducted in different regions of the world on climatechange. the results of these studies show considerable changes in climatic factors especiallyin precipitation and temperature. in this research, the trend of changes in annual and seasonalrainfall and temperature in 24 synoptic stations over a 50-year data period (1956-2005) wasinvestigated in iran. the mann- kendall test and linear regression technique were used to analyzethe trend of changes in climatic factors. the results showed both increasing and decreasingtrends in annual rainfall at various regions of iran. annual rainfall in northern slopes of alborzand western slopes of the zagros mountain as well as in eastern and southeast parts of iran hada decreasing trend while in the central of iran the trend of changes was increasing. in southernregion of iran the rainfall had an increasing trend. the results also showed that temperature inmost of the studied stations over the considered period was increasing. the highest and lowestchanges 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 towardmore cooling. the temperature trend in oromiye was decreasing in autumn and summer whileshahrekord and bandar abbas had the same trend in summer and winter.