عنوان مقاله [English]
In this study, drought monitoring based on three drought indexes SPI, RDI and SPEI in stations Babolsar, Bandar Abbas, Sabzevar, Shiraz and Zahedan in order to evaluate the impact ofthe evapotranspiration on drought has been paid. Correlation between 12-month scale drought indexes and 12-month moving average for some of the meteorological parameters was calculated. According to the results SPI index showed the highest correlation with rainfall. Also significant correlation between SPEI index and ETo were observed in different climatic areas. ETo correlation in low rainfall and dry areas with SPEI index shows extremely high values and with decrease in precipitation to ETo, the correlation value between SPEI index and ETo were increased. Affecting parameters onETo correlation with drought indices is lower than the correlation ETo with drought indexes and The amount of correlation this parameters with drought indexes, is directly affected by its correlation with ETo. These parameters are implicitly affect the drought and its effects on aggregate drought is more effective. Due to high correlation of parameters ETo with drought conditions in most regions studied is suggested that in arid and semi-arid area SPEI index (compared with indices SPI and RDI) should be used for drought monitoring. On the other hand; the use of SPI index in these areas is not recommended in any way. However, in areas with precipitation to ETo ratio close to one, using based on rainfall indices such as SPI can be well region's status.