Tempo-spatial analysis of extreme 24 hour precipitations in Iran

In this paper, in order to analysis tempo-spatial variations of extreme 24 hour precipitations in Iran, monthly precipitation data of synoptic and climatologic stations from beginning of establishment to Dec 2005 have been studied. Using these data set monthly digital maps with a spatial resolution of 15*15Km has been calculated. Dividing 24 hour precipitation to annual precipitation provided extreme 24 hour precipitation coefficient map. An agglomerative hierarchical cluster analysis then applied to highest 24 hour precipitation coefficient matrix. This analysis shows that there are four main precipitation regions in Iran. In region No.3 about 60-100 percent of annual precipitation may occur just in 24 hours. In region No.4 about 100-160 percent of annual precipitation may occur just in 24 hours. These regions more subject to the extreme rainfall. These two regions are located in southern half of Iran, along Persian Gulf and northern coasts Oman Sea.The possibility of heavy 24 hour precipitation exists throughout Iran, except southern coasts of Caspian Sea in four months Dec, Jan, Feb and March. Extreme 24 hour precipitations of Caspian Sea coasts have occurred in Aug, Sept and October.Because of the weakness of westerlies, possibilities of extreme 24 hour precipitation didnt exist in southern half of Iran from April to November