Review the Changes of Spatial Autocorrelation Patterns Within a Decade of Precipitation Over the Last Half-Century in Iran

Precipitation is the most variable climatic elements. These changes occur in the area in both the spatial and time dimension in the form of climatic condition of the area. The aim of this study is the review of the spatial correlation pattern of changes within a decade of precipitation over the past half-century in Iran. For this purpose، the daily precipitation data was extracted by using 664 synoptic and climatic stations during the time period of 1961-2011 and was used as the data base (Asfazari data). For obtaining the changes information of a decade''s precipitation in Iran، the methods of ground statistics such as spatial autocorrelation of global Moran index، local Anselin index of Moran and Hotspots and also planning facilities in Matlab، Surfer and GIS environments have been used. The results obtained of this study showed that the changes of precipitation during one decade in Iran has a high cluster pattern. However، based on local Moran index and hot spots، precipitation at coastal areas and some parts at the west and south west of Iran (mainly Zagros mountains) had a positive spatial autocorrelation (precipitation clusters with high value) and parts of central areas and also parts of the south east of the country (mainly Zabol) had a negative autocorrelation (precipitation clusters with low value). In other areas of Iran، precipitation has had no significant pattern or spatial autocorrelation. For the purpose of reviewing the changes of precipitation cycles، spectrum analysis method has been used. The results obtained from the said method indicates the existence of short and medium term cycles in annual precipitation of the country.