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CR prepress abstract   -  DOI: https://doi.org/10.3354/cr01705

A new version of the reconnaissance drought index, N-RDI

Mohammad Mehdi Ghasemi, Abdol Rassoul Zarei*, Marzieh Mokarram

*Corresponding author:

ABSTRACT: In this study, a modified version of the reconnaissance drought index (RDI), named the new version of the RDI (N-RDI), has been presented. To calculate the N-RDI, the precipitation and potential evapotranspiration were replaced with the spatially normalized precipitation (SNP) and spatially normalized potential evapotranspiration (SNPET), respectively. To assess the capability of N-RDI, at first based on the climatic data series of 12 stations from 1967 to 2019, the RDI and N-RDI were computed in monthly, seasonal, and annual time scales over Iran. Then the interpolated maps of the RDI, N-RDI, and annual yield of rain-fed winter wheat were prepared using the inverse distance weighting (IDW) method. In the next step, four regions were selected in Iran (with different climate conditions) and 30 random points were chosen in each area. Finally, based on the correlation coefficient (CC) between the difference of the average yield of rain-fed winter wheat (DMRWWY) and the difference of the average of RDI (Da-RDI) in selected points and also, the CC between DMRWWY and the difference of the average of N-RDI in chosen points (Da-N-RDI) in different regions at different time scales, the capability of N-RDI and RDI were compared. The CC between DMRWWY and Da-N-RDI in humid (H) and semi-arid (SA) regions, in H and hyper-arid (HA), in SA and A, in SA and HA, and in arid (A) and HA at 88.23% of selected periods were more than the CC between DMRWWY and Da- RDI. Also, the CC between DMRWWY and Da-N-RDI in H and A regions at 76.47% of selected periods were more than the CC between DMRWWY and Da- RDI. The results showed that the capability of N-RDI for assessing drought in large basins is more than RDI.