Articles | Volume 24, issue 9
Hydrol. Earth Syst. Sci., 24, 4541–4565, 2020
https://doi.org/10.5194/hess-24-4541-2020
Hydrol. Earth Syst. Sci., 24, 4541–4565, 2020
https://doi.org/10.5194/hess-24-4541-2020

Research article 21 Sep 2020

Research article | 21 Sep 2020

A universal Standardized Precipitation Index candidate distribution function for observations and simulations

Patrick Pieper et al.

Data sets

MPI-ESM-LR seasonal precipitation hindcasts P. Pieper, A. Düsterhus, and J. Baehr http://cera-www.dkrz.de/WDCC/ui/Compact.jsp?acronym=DKRZ_LTA_1075_ds00001

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Short summary
The Standardized Precipitation Index (SPI) is a widely accepted drought index. SPI normalizes the precipitation distribution via a probability density function (PDF). However, which PDF properly normalizes SPI is still disputed. We suggest using a previously mostly overlooked PDF, namely the exponentiated Weibull distribution. The proposed PDF ensures the normality of the index. We demonstrate this – for the first time – for all common accumulation periods in both observations and simulations.