Spatial analysis on continuty of rainfalls over Iran during in the cold period of the year

Precipitation plays a fundamental role in the survival of Earth's systems and provides water to sustain life on earth. The importance of precipitation durability, especially in arid and semi-arid regions, which includes most part of Iran, is greater than its volume. The aim of this study is to identify the rainfall regions of Iran in terms of rainfall durability and to investigate the characteristics of rainfall durability in each region. in order to investigate the durability of Iran's precipitation and by defining the day of precipitation as "Day with a rainfall equal to or greater than 0.5 mm", the daily precipitation data of 80 synoptic stations in the country during the cold 6 months of the year from October to March over a 30-year period (1987-2016) used. Setting the data in daily tables in the first step, enabled programming in the MATLAB environment for separating precipitation into ten groups from "one-day" to "ten-day". And in the second step in the SPSS environment based on frequency characteristics, amount and mean of precipitation in the mentioned groups, clustering done by WARD method were merged by clustering method. Implementation of clustering process on Iran rainfall durability showed that there are 7 almost homogeneous zones in Iran based on rainfall durability; which the effect of inland and outer climatic factors including latitude, roughness, path of precipitation systems and distance to moisture sources is evident that with declining the last three factors, these zones become more homogeneous in the eastern half of Iran. One of the projectable hazards is that the supply of atmospheric precipitation, especially in east of Iran, is more in charge of short durable precipitation. In fact, the one-day and the two-day low precipitations are dominant in the western part of the country and in terms of the proportion of durability in the eastern half of Iran. This finding shows the general inefficiency of the country's water resources management plans with the macro approach of storage the surface water.Key words: Spatial patterns, Precipitation durability, Rainy day, Iran