Analysis and Forecasting of Drought by Developing a Fuzzy-Based Hybrid Index in Iran

Drought is the most important and destructive climate phenomenon which is usually of importance in a regional scale. Therefore, this study offers a fuzzy-based hybrid index in order to analyze the regional drought in Abadan and khoramshahr, Khuzestan, Iran. Influencing all aspects of human activity, drought does not have a comprehensive definition and an appropriate and general index to explore it. Consequently, in order to develop a model to evaluate and analyze drought, the fuzzy model has been used. The application of fuzzy logic to examine drought in Abadan-khoramshahr station demonstrated that fuzzy logic enables us to examine drought more accurately and appropriately because it takes into account the type of product (wheat or dates) in calculating the probability of drought. In furtherance of this aim, the fuzzy function related to the standardized Precipitation Index (SPI) and the standardized evapotranspiration index (SEI) have been combined and a new indicator called the standardized evapotranspiration and Precipitation index (SEPI) was developed. In the final fuzzy model, 81 rules have been utilized. In this study, the annual data of wheat and dates from 1994 to 2012 have been utilized (sometimes 2013 data have been used), and on this basis, the results of the model revealed that severe and continued droughts have occurred in 1999, 2007 and 2009 and the probability of drought for wheat and dates was 64.29 and 57.14 percent respectively in this period.