Assessment and Detection of Climate change in Iran during Recent Decades

The aim of this study is assessment and detection of climate change in Iran during recent decade. Daily precipitation، minimum and maximum data from 1437 synoptic، climatology and rain gauge stations during 1/1/1962 to 31/12/2004 has been used. Daily data interpolated by Kriging geo-statistical method over 15×15 kilometer pixels. A matrix with 15706×7187 dimension has been created that on the rows located days and on the columns، pixels. In order to detect climate change، 27 climate change indices used that was recommended by Expert Team on climate Change and Indices (ETCCDI). The results of this study show that warm extreme indices، including Summer Days (SU25)، Warm Days (TX90p)، Warm nights (TN90p) and Tropical nights (TR20) are increasing during the study period. While extreme cold indices for example Frost days (FD)، Ice days (ID)، Cold nights (TN10p) and Cold Days (TX10p) are decreasing. Warm Spell Duration Index (WSDI) is being longer while Cold Spell Duration Index (CSDI) is being shorter. The increase of maximum daily temperature and minimum temperature result in a decrease in Diurnal Temperature Range (DTR). The results also show positive trends for the frequency of occurrence of extreme precipitation.