climatology atlas of frosts statistical properties of iran

in order to provide climatology atlas of frosts statistical properties of iran and to attain spatial and temporal pattern of it, daily data of minimum temperature of 62 synoptic weather stations for a 15 year-period (1991-2007) from october to may, were adopted from iran meteorological organization. by choosing may 1st as basis day, five statistical properties and their spatial and temporal distribution were extracted and plotted: mean beginning day of frost, mean ending day of frost, average frequency of frost days, average period of frost season and average period of growth season. spatial configuration of these factors is such that from south to center of iran which high altitudes are fewer, has regular western-eastern configurations, but from center of iran toward north which high altitudes play more sensible role, this configuration is disturbed and more dependent to altitudes. therefore, by performing cluster analysis on five statistical properties of frost of iran, it was observed that we can divide iran to 6 distinct clusters. these clusters are entitled from a to f. spatial configuration of these, like five statistical properties, are functions of latitude and altitude. region of a is southernmost region of iran, have no frost and region f, that is located in northwest of iran, have earliest, latest, longest periods of frost and shortest period of growth season. thus, configuration of statistical properties of frost at iran is function of geo-climate factors and of synoptic systems which were penetrated country.