Regional Frequency Analysis of Droughts in Portugal

Santos, João Filipe; Portela, María Manuela; Pulido‐Calvo, Inmaculada

doi:10.1007/s11269-011-9869-z

Cited by 111 publications

(56 citation statements)

References 67 publications

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“…In spite of the fact that the Wakeby distribution is able to exhibit shapes that other 2-or 3-parameter distributions cannot mimic (Sen & Niedzielski, 2010;Morgan et al, 2011;Santos et al, 2011), this 5-parameter function has also failed to describe the probabilistic structure of a large number of rainfall series observed at the weather station of Pelotas (37% of the 264 series). For instance, the observed rainfall amount for March 1905 is 1.0 mm.…”

Section: Resultsmentioning

confidence: 99%

Inadequacy of the gamma distribution to calculate the Standardized Precipitation Index

Blain

Meschiatti

2015

Rev. bras. eng. agríc. ambient.

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A B S T R A C TThe Standardized Precipitation Index was developed as a probability-based index able to monitor rainfall deficit in a standardized or normalized way. Thus, the performance of this drought index is affected by the use of a distribution that does not provide an appropriate fit for the rainfall data. The goal of this study was to evaluate the adjustment of the gamma distribution for the rainfall amounts summed over several time scales (Pelotas, Rio Grande do Sul, Brazil), to assess the goodness-of-fit of alternative distributions to these rainfall series and to evaluate the normality assumption of the Standardized Precipitation Index series calculated from several distributions. Based on the Lilliefors test and on a normality test, it is verified that the gamma distribution is not suitable for calculating this Index in several timescales. The generalized normal distribution presented the best performance among all analysed distributions. It was also concluded that the drought early warning systems and the academic studies should re-evaluate the use of the gamma distribution in the Standardized Precipitation Index calculation algorithm. A computational code that allows calculating this drought index based on the generalized normal distribution has also been provided. Inadequação da distribuição gama para o cálculo do Índice Padronizado de Precipitação R E S U M OO Índice Padronizado de Precipitação foi desenvolvido para ser um método probabilístico que monitora os déficits de precipitação pluvial, de forma normalizada. Assim, a confiabilidade deste índice é afetada pelo uso de distribuições inadequadas aos dados de precipitação. Com isto, o objetivo do trabalho foi: avaliar o ajuste da distribuição gama aos totais de precipitação acumulados em distintas escalas temporais (Pelotas, Rio Grande do Sul), analisar o desempenho de demais distribuições no cálculo desse índice e avaliar o pressuposto de normalidade das séries desse quantificador de seca, calculadas com base nessas distintas distribuições. Os testes Lilliefors e de normalidade indicaram que a distribuição gama não é apropriada para o cálculo do índice em diversas escalas temporais. A distribuição generalizada normal mostrou-se apropriada. O uso desta função também resultou no maior número de séries com distribuição normal. Recomenda-se, então, que os sistemas de monitoramento de seca e os estudos acadêmicos reavaliem o uso da distribuição gama no cálculo do Índice Padronizado de Precipitação. Um código computacional capaz de calcular este índice de seca a partir da distribuição generalizada normal é também apresentado.

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Section: Resultsmentioning

confidence: 99%

Inadequacy of the gamma distribution to calculate the Standardized Precipitation Index

Blain

Meschiatti

2015

Rev. bras. eng. agríc. ambient.

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“…By following Parida (1999), Morgan et al (2011) and Santos et al (2011) the parameters of Eq. 3 (ξ, α, k, and h) were also estimated by using the lmom.…”

Section: Goodness-of-fit Testsmentioning

confidence: 99%

“…According to Morgan et al (2011) the KAP and WAK are able to exhibit shapes that other distributions cannot mimic. Because of its flexibility, these two distributions can be used to describe the probabilistic structure of a natural process, such as rainfall, which has several contributing factors (Sen & Niedzielski, 2010;Santos et al, 2011). Accordingly, these multi-parameter distributions have been used in several hydrological and meteorological studies.…”

Section: Introductionmentioning

confidence: 99%

Using multi-parameters distributions to assess the probability of occurrence of extreme rainfall data

Blain

Meschiatti

2014

Rev. bras. eng. agríc. ambient.

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Soil erosion, soil saturation and floods are frequently associated with extreme rainfall events. Thus, the scientific literature agrees on the need to carry out studies that improve the assessment of the probability of occurrence of extreme rainfall values. The main goal of this study was to compare the performance of the multi-parameters distributions Wakeby, Kappa and Generalized Extreme Value in fitting the annual maximums of daily, 2-day and 3-day rainfall amounts obtained from the weather station of Campinas, located in the State of São Paulo, Brazil (1890-2012. As a secondary aim, the presence of climate trends and serial correlation in these series was also evaluated. The auto-correlation function and the Mann-Kendall tests have shown the presence of no serial correlation and climate trends in the above mentioned series. The results obtained from goodness-of-fit procedures allowed us to conclude that the Kappa and the Generalized Extreme Value distributions present the best performance in describing the probabilistic structure of the series under analysis.Distribuições multi-paramétricas para avaliar a probabilidade de ocorrência de eventos extremos de precipitação pluvial R E S U M O Erosão e saturação hídrica do solo estão frequentemente associadas a eventos extremos de precipitação pluvial, tal como as enchentes. Desta forma, a literatura científica indica a necessidade de se realizar estudos que aprimorem a determinação da probabilidade de ocorrência desses eventos. O objetivo principal do estudo foi comparar o desempenho das distribuições multiparamétricas Wakeby, Kappa e Generalizada dos Valores Extremos na estimativa dos máximos anuais de totais de precipitação (diários, dois e três dias) da localidade Campinas-SP (1890-2012. O objetivo secundário foi avaliar a presença de tendências climáticas e a correlação serial nessas variáveis. A função autocorrelação e o teste de Mann-Kendall não indicaram a presença de significativas tendências climáticas e correlações serias em nenhuma das séries. Com base nos resultados dos testes de aderência concluiu-se que as distribuições Kappa e Generalizada dos Valores Extremos apresentam os melhores desempenhos na descrição probabilística das séries do estudo.

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“…A partial duration series (PDS) analysis is conducted, since it is based on the magnitude of all drought events above a certain predetermined threshold and is related with the SPI event identification [24]. Therefore, the SPI time series was built using the PDS analysis.…”

Section: Methodsmentioning

confidence: 99%

Application of a Standardized Precipitation Index for Meteorological Drought Analysis of the Semi-Arid Climate Influence in Minas Gerais, Brazil

Juliani

Okawa

2017

Hydrology

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Abstract:In recent years, the Southeast region in Brazil has suffered from the effects of drought events. Analyzing the history of drought events is fundamental to establish potential risks of the occurrence of droughts in the future. One of the many ways to prevent substantial impacts and evaluate a drought risk assessment is through analysis of severity, duration and frequency characteristics of these events. In this context, the current study developed Severity-Duration-Frequency curves and derived an isohyetal map for the area influenced by the semi-arid climate in the state of Minas Gerais, through the analysis of 17 rainfall stations. The drought events identification and the analysis of its conditions were assessed using the Standardized Precipitation Index (SPI) for a 12-month time scale. The SDF curves were developed using the minimum cumulative 12-month precipitation values fitted to the Gamma distribution for 1, 3, 6, 9 and 12-month drought durations. The computed SDF curves for each station were further regionalized in order to obtain a general result for the study area. It can be observed that for a return period of 100 years, the estimated cumulative 12-month precipitation varies from 353 mm in a 1-month drought duration to 458 mm in a 12-month drought duration. The derived isohyetal map provides a more accurate local application of the results.

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Regional Frequency Analysis of Droughts in Portugal

Cited by 111 publications

References 67 publications

Inadequacy of the gamma distribution to calculate the Standardized Precipitation Index

Inadequacy of the gamma distribution to calculate the Standardized Precipitation Index

Using multi-parameters distributions to assess the probability of occurrence of extreme rainfall data

Application of a Standardized Precipitation Index for Meteorological Drought Analysis of the Semi-Arid Climate Influence in Minas Gerais, Brazil

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