A new approach to technique for order-preference by similarity to ideal solution (TOPSIS) method for determining and ranking drought: A case study of Shiraz station

In this research, using technique for order-preference by similarity to ideal solution (TOPSIS) index, drought phenomenon is determined and ranked. For this purpose, using 5 atmospheric elements including temperature, wind, precipitation days, annual precipitation, precipitation concentration index (PCI), droughts occurred in Shiraz station for 20-year statistical period (1983-2003) have been determined and ranked. In TOPSIS method, having employed more climate elements as compared with the earlier more simple methods, drought phenomenon is considered systematically. Finally, in order to validate the suggested method, the output data of rainfall anomaly index (RAI), decadal precipitation index (DPI) and standard index of annul precipitation (SIAP) methods have been compared for most stations of the country using TOPSIS. The obtained results prove the validity of the suggested method, so that the correlation of this method with 3 methods of RAI, SIAP, DPI with regard to Shiraz station outputs has been calculated to be r= 0.8.   Key words: TOPSIS method, climatic drought, ranking, Shiraz station.