comparative study of the meteorological drought indices (spi and siap) using data mining method (case study of kermanshah province)

abstract precipitation is an important variable which is used in definition of drought. based on precipitation amounts, some indices are devised for drought monitoring including, the standardized precipitation index (spi) and the standard index of annual precipitation (siap). each of these drought indices are classified into some classes so that each class descripts a given severity of drought. investigation of simultaneously occurrence situation for two drought indices can be an appropriate measure to evaluate the agreement of indices. association rules in data mining is used to find rules and patterns in database. in this paper, two drought indices, spi and siap, were computed at 11 meteorological stations belong to ministry of energy in kermanshah province. then, based on association rules, simultaneously occurrence situation of drought severity classes for both indices were determined in seasonally, half yearly and yearly time scales. results showed that there is not any good agreement between most of drought category from these indices (less than 50 percent) and shows different behavior of drought.