Find in Library

The aim of this study  is  to analyze the areas of heavy rainfall thresholds in Iran. For this purpose, daily rainfall data  of over 50 years were produced from  Esfezari database. In continue, percentile  was used to determine the heavy precipitation threshold. In order to study and zoning the thresholds, the analysis of harmonic means has been used. By implementing cluster analysis on heavy rainfall, four zones as the following were recognized. First,  the zone with great heavy rainfall threshold and coefficient of very great changes, second, zone with medium heavy rainfall threshold and coefficient of  medium changes, third zone with very great heavy rainfall and coefficient of very low changes  and the fourth, zone with too low  heavy rainfall and coefficient  of very great changes. Among the zones, the third zone, i. e. the  Caspian coast has  had the highest heavy rainfall  threshold, while a great deal of areas in the central part of Iran has  had low heavy rainfall threshold. The results of the analysis  in the four zones indicate that  except in the third zone , which the medium term is dominant, in other areas, the short term cycles is dominant on the Iran's heavy rain fall threshold.