Computation of Drought Index SPI with Alternative Distribution Functions

Panagiotis Angelidis (), Fotios Maris, Nikos Kotsovinos and Vlassios Hrissanthou

Water Resources Management: An International Journal, Published for the European Water Resources Association (EWRA), 2012, vol. 26, issue 9, 2453-2473

Abstract: The Standardized Precipitation Index (SPI) is widely used as drought meteorological index, to identify the duration and/or severity of a drought. The SPI is usually computed by fitting the gamma probability distribution to the observed precipitation data. In this work, the possibility to calculate SPI by fitting to the precipitation data the normal and the log-normal probability distributions was studied. For this purpose, 19 time series of monthly precipitation of 76 years were used, and the assumption that the gamma probability distribution would provide better representation of the precipitation data than log-normal and normal distributions, at various time scales (1, 3, 6, 12 and 24 months) was tested. It is concluded that for SPI of 12 or 24 months, the log-normal or the normal probability distribution can be used for simplicity, instead of gamma, producing almost the same results. Copyright Springer Science+Business Media B.V. 2012

Keywords: Meteorological drought; SPI; Gamma; Log-normal; Normal probability distributions (search for similar items in EconPapers)
Date: 2012
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Citations: View citations in EconPapers (17)

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DOI: 10.1007/s11269-012-0026-0

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