Evaluation of Elimate Indices and the General Trend of Climate Changes (Case study: Shiraz synoptic station)

Continual drought affected on the earth surface and has changed appearance of it. Therefore accurate assessment of changes in the climate parameters and effect of them on the environmental factors and water resources is very important and necessary. In this paper¡ precipitation and temperature changes in Shiraz synoptic station since 1983 to 2013 were evaluated. In this study various drought indexes such as SPI¡ RAI¡ PNPI¡ DI and SIAP evaluated in the annual scale and based of them¡ the different rainfall regimes in Shiraz were categorized. According to the monitoring of drought and wet years condition¡ maximum similarity is between SIAP index and DI¡ RAI indexes¡ SPI and RAI indexes have minimum similarity. According to the Results of this paper in the recent decade changes trend of annual precipitation¡ maximum intensity of rainfall and minimum absolute of temperature have been decreased. So that annual precipitation decreased about 50 millimeters in the last decade¡ maximum intensity of daily precipitation decreased 20 percent and average of minimum annual temperature decreased 2 degrees centigrade. Also the trend changes of maximum absolute temperature and number of frost days have been increased. According to results difference between maximum and minimum annual temperature have been increased¡ average of maximum absolute temperature in the ten years periods have been increased about 0.6 degrees centigrade.