Frequency Analysis of Dangerous Extreme Rainy Days in IRAN

Today, rainfall hazards creates wide crisis in military, security and social, because the tensions in rural and social destruction of the natural environment have led to violent conflicts. To analysis the extreme rainy days in Iran, has been used daily data of extreme rainy day in 235 synoptic stations in the period from 1961/03/21 to 2019/03/20(21549 days). Therefore, this database is a matrix of size 21549×235. Rows are time and columns represent the stations. Using Euclidean distance and Ward linkage, extreme rainy days the country was in four regular rain cluster. The results showed that the first cluster (days with relatively heavy rain) with a frequency of 87% of stations, is widely distributed in Iran. The second cluster (Semi-heavy rain) with 9 percent, limited to a few stations in the eastern coast of the Caspian Sea and the western half of the Zagros Mountains. The third cluster (heavy rain) with 3% of stations located on the shore of the Caspian Sea and western Zagros mountains stations in Astara, Baboulsar, Noushahr, Ramsar, Rasht, Kouhrang and Yasouj. Finally, the fourth cluster (super heavy rain) with 1 percent, it occurs only in Bandar-Anzali station. It seems that the frequency of extreme rainy days in Iran tends to cluster and implant and complies with topography and distance or proximity to the sea.Among these, the role of rainfall hazards and their heterogeneous distribution, such as heavy rains and floods, is of particular importance in countries around the world, especially Iran. So that sometimes such events greatly affect the security and defense conditions of a country.