Spatial Analysis of Meteorological Drought in Iran from 1965 to 2003

The present study examined year-to-year variations in areas affected by drought during a period of 39 water years in iran. ninety-five meteorological stations were chosen to provide near-continuous long term records, although some data was missing (less than 10%). the missing data points were estimated using a linear correlation method between the reference station with the missing data points and a neighboring station that had a complete record. at all stations, the standard index of annual precipitation (siap) was calculated for water year (sum of precipitation from october 1 to september 31). the geo-statistical method of weighting moving average (wma) was applied to a 2×2 km grid network map of iran and the geographical distribution of siap was calculated and displayed. from this, the percentage of area affected by severe, moderate, and mild drought was computed for each year; the frequency of drought was analyzed by severity and the behaviors of the most extensive historical droughts were determined. the results showed that: a) the maximum frequency of severe drought was 5.1 times and moderate drought was 23.1 times per 100 years; b) the most extensive droughts (more than 80% of the country) occurred during 197 -1971 (82.21%), 1988-1989 (92.05%), and 1999-2000 (96.27%); and c) drought spread in iran beginning from the northwestern and southeastern regions, gradually extending to the central regions