Increasing the regional availability of the Standardized Precipitation Index: an operational approach

Monica Cristina Meschiatti,Gabriel Constantino Blain

doi:10.1590/1678-4499.478

Monica Cristina Meschiatti, Gabriel Constantino Blain

Open Access

https://doi.org/10.1590/1678-4499.478

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Journal: Bragantia	Publication Date: Oct 6, 2016
Citations: 13	License type: cc-by

Affiliation: Instituto Agronômico do Paraná

Abstract

The need to use a length of rainfall records of at least 30 years to calculate the Standardized Precipitation Index (SPI) limits its application in several Drought Early Warning Systems of developing countries. Therefore, in order to increase the number of weather stations in which the SPI may be applied, this study quantified the difference among SPI values derived from calibration periods (CP) smaller than 30 years in respect to those computed from the 30-year period of 1985 – 2014 in the State of Sao Paulo, Brazil (time scales ranging from 1 to 12 months were considered). The correlation, agreement and consistency of SPI values derived from CP ranging from the last 30 to 21 years have been evaluated. The Kolmogorov-Smirnov/Lilliefors test indicated, for all CP, that the 2-parameter gamma distribution may be used to calculate the SPI in the State of Sao Paulo. The normality test indicated that, even for the period of 1985 – 2014, the normally assumption of the SPI series is not always met. However, it was observed no remarkable difference in the rejection rates of the normality assumption obtained from the different CP. Finally, both absolute mean error and the modified index of agreement indicated a high consistence among SPI values derived from the calibration period of 1991 – 2014 (24 years) in respect to those derived from the 30-year period. Accordingly, it is possible to use weather stations with rainfall records starting in 1991 (or earlier) to calculate, in operational mode, the SPI in the State of Sao Paulo.

Highlights

Drought is a slow-moving hazard that occurs in practically all regions of the Globe (Hayes et al 2011)
The Standardized Precipitation Index (SPI) is largely used in operational mode by Brazilian agricultural institutions, such as the Brazilian Agricultural Research Corporation (Embrapa), the Agronomic Institute of Campinas (IAC) and the National Institute of Meteorology (INMET) as part of their Drought Early Warning Systems
McKee et al (1993) stated that a continuous period of at least 30 years is required to calculate this index. It is well-known that this statement has limited the operational application of the SPI in several regions of the world. This fact is true for developing countries such as Brazil, where the lack of longterm meteorological records is a common problem

Summary

Introduction

Drought is a slow-moving hazard that occurs in practically all regions of the Globe (Hayes et al 2011). The Standardized Precipitation Index (SPI; McKee et al 1993) has been used to improve the timely detection of emerging droughts (Hayes et al 1999; Wu et al 2007; Blain 2012a, among many others) by quantifying, on regional basis, the rainfall departures over a particular time scale. McKee et al (1993) stated that a continuous period of at least 30 years is required to calculate this index It is well-known that this statement has limited the operational application of the SPI in several regions of the world. This fact is true for developing countries such as Brazil, where the lack of longterm meteorological records is a common problem.

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Results