Trends in extreme daily temperature in south west of Iran during recent decades

Long-term annual or seasonal averages of climatic variables like temperature, has generally been used as indicator for the assessment of climate change. Accordingly, this paper is aimed to examine extreme temperature as indicative climatic variable in synoptic stations of Ahwaz located in Khozestan province during a 40 year period (1964- 2003) to determine recent climatic changes over the mentioned area. To achieve the aim, 6 indices of extreme temperature recommended by the internationally agreed WMO–CCL/CLIVAR list of over 50 climate change indices climate extremes were selected and calculated. The six indices are consist of cold nights, cold days, warm nights, hot days, summer days and diurnal temperature range. These indices describe cold extremes as well as warm extremes. Extreme temperature indices for this study are based on the 1st and 99th percentiles. According to the current climate condition, based on ARIMA model, 10 years prediction of mentioned indices also was made. The results of the research indicated that thermal conditions over the area are changing as indicated by a warming trend identified during the study period. The results also shown the marked negative trends for indices such as cold days, cold nights and diurnal temperature range over the region. While significant increases are detected in the annual number of hot days, warm nights and summer days. The output of ARIMA model confirmed consist warming trend for Ahwaz in the next 10 years (2004-2013).