احسان رشید بیگی

The purpose of this study is zoning and analyzing the precipitation cycles in central areas of Irna. For this purpose, 29 climatic variables for 72 synoptic and climatology stations during the statistical period of (1980-2011) have been uses. To this end, by using geostatic methods, a data base of dimension 29×3673 km was formed. Then for climatic zoning, cluster analysis method and discriminant analysis have been used. For detecting hidden or visible precipitation cycles at each area, spectrum analysis have been used. Data obtained from selected climatic variables have been reviewed and analyzed by Ward incorporation cluster analysis method that after drawing Dan Degram, four climatic areas(1- the area with high precipitation, 2-very low temperature and high humidity, 3- very low precipitation, very high temperature and very low humidity 4- low precipitation, high temperature and low humidity) have been recognized. To evaluate the results of the cluster analysis, discriminant analysis method was used to test the mean difference. The results of discriminant analysis showed that 98.87 of the stations are located correctly in their respective groups.The results obtained from using analysis of precipitation cycles of each of these areas showed that short cycles of 2-4years have been mostly dominant in the both four groups. However, the most variable cycles are located in area No.1 due to different factors including vicinity with Persian Gulf waters and locating in the shadow of Zagros mountains.