surveying of changes in spatial pattern of decadal freezing of iran

purpose of this study is analysis of spatial auto-correlation of freezing changes of iran over the last half century. daily temperature data over the period 1340 - 1383 of esfezari database provided by doctor masoodian (to enhance the temporal resolution of the database, daily observations of temperature from 1383 to the end of 1390 using the same method and the same spatial resolution is added to the database) has been used. then by using matlab and gis soft wares, freezing changes during 5 same length period extracted by using spatial auto-correlation analysis (moran index). in this study, surfer software was used for mapping operations. the results show that the maximum frequency of freezing occurrence in all periods is in west, north west and north east, which are adapted on altitude regions. regions that located in the southern parts of the country due to dynamic high pressure didn’t have freezing day. however, the recent periods (particularly since 1370) freezing has declined sharply. analysis of spatial auto-correlation of freezing pattern changes show that the spatial distribution freezing decreases recent years that corresponded with the results of studies on global warming.