Analyzing Spatial Pattern of Drought Changes in Iran, Using Standardized Percipetation Index (SPI)

Abstract

At present, the Standardized Precipitation Index (SPI) is the most widely used ought index to provide good estimations about the intensity, magnitude and spatial extent of oughts. The objective of this study was Analyzing Spatial Pattern of ought by SPI index. In this paper, according to the data of 40 stations in Iran during 1967-2005, the pattern of ought changes is evaluated. Influenced zone of each station was specified by thiessen method. The results of this paper showed that the surface percent of the wet area has been decreased during a period evaluation. The surface percent of the extremely wet areas, very wet areas and moderately wet areas have had a descending trend. However, only the descending trend of moderately wet areas has been significant, but the surface percent of the y areas have had an ascending trend. The surface percent of moderately y areas and very y areas have had an ascending trend. However, only the ascending trend of moderately y areas has been significant.