Variabilidade amostral das séries mensais de precipitação pluvial em duas regiões do Brasil: Pelotas-RS e Campinas-SP

Blain, Gabriel Constantino; Kayano, Mary Toshie; Camargo, Marcelo Bento Paes de; Lulu, Jorge

doi:10.1590/s0102-77862009000100001

Cited by 19 publications

(20 citation statements)

References 8 publications

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“…The choice of Pelotas is because it is one of the longest meteorological series of Brazil showing a high consistency (Blain et al, 2009). From the daily data, it was derived the rainfall series used to calculate the SPI at several timescales (1 to 24 months).…”

Section: Methodsmentioning

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: Methodsmentioning

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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“…Although several author, such as Thom (1966), Blain (2005), Blain et al (2007), Blain et al (2009) and Blain (2009), have already assessed the robustness of the Gam distribution in describing monthly precipitation series of the State of São Paulo; the use of PE3 distribution in describing these series seems to be neglected. Since the SPI is a probability index, assessing the robustness of the PE3 distribution in describing (4) (5) (6) precipitation series may be seen as the first (and perhaps the most important) step in evaluating the possibility of adopting this three parameters distribution within SPI calculation algorithm.…”

Section: Methodsmentioning

confidence: 99%

Standardized precipitation index based on pearson type III distribution

Blain

2011

Rev. bras. meteorol.

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The initial step in calculating the Standardized Precipitation Index (SPI) is to determine a probability density function (pdf) that describes the precipitation series under analysis. Once this pdf is determined, the cumulative probability of an observed precipitation amount is computed. The inverse normal function is then applied to the cumulative probability. The result is the SPI. This article assessed the changes in SPI final values, when computed based on Gamma 2-parameters (Gam) and Pearson Type III (PE3) distributions (SPIGam and SPIPE3, respectively). Monthly rainfall series, available from five weather stations of the State of São Paulo, were chosen for this study. Considering quantitative and qualitative assessments of goodness-of-fit (evaluated at 1-, 3-, and 6-months precipitation totals), the PE3 distribution seems to be a better choice than the Gam distribution, in describing the longterm rainfall series of the State of São Paulo. In addition, it was observed that the number of SPI time series that could be seen as normally distributed was higher when this drought index was computed from the PE3 distribution. Thus, the use of the Pearson type III distribution within the calculation algorithm of the SPI is recommended in the State of São Paulo. Keywords: drought, Gamma distribution, SPI RESUMO: ÍNDICE PADRONIZADO DE PRECIPITAÇÃO BASEADO NA DISTRIBUIÇÃO PEARSON TIPO III O cálculo do Índice Padronizado de Precipitação (IPP) inicia-se com a adoção de uma distribuição paramétrica (dp) utilizada para a estimativa das probabilidades de ocorrência associadas a uma série de precipitação pluvial. Após essa escolha, a probabilidade acumulada de ocorrência de um determinado valor de precipitação é calculada. O IPP é obtido após a aplicação da função normal inversa a essa probabilidade acumulada. O artigo avaliou as alterações nos valores finais do IPP, quando calculado com base nas distribuições Gama com dois parâmetros (Gam) e Pearson tipo III (PE3; IPPGam e IPPPE3, respectivamente). Utilizaram-se dados de precipitação pluvial de cinco localidades do Estado de São Paulo, nas escalas de 1, 3 e 6 meses. Aplicando testes de aderência, tanto qualitativos, quanto quantitativos, verificou-se que as probabilidades associadas às séries utilizadas foram melhores estimadas por meio da PE3. Foi também observado, que o número de séries temporais do IPP que podem ser consideradas normalmente distribuídas, foi maior quando este índice de seca foi calculado com base na PE3. Dessa forma, recomenda-se a adoção da PE3 no cálculo do IPP no Estado de São Paulo. Palavras-Chave: seca, distribuição gama, IPP

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“…It is observed that, of the 14 stations analyzed, only in the station 3152014 (Pelotas), the null hypothesis was rejected at a significance level of 5% when it was used the precipitation data of the periods from 1953 to 1973 and from 1974 to 2007, meaning that there was a change in the trend of annual precipitation in the locality of Pelotas. BLAIN et al (2009) A: accept the null hypothesis (H 0 ) at 5% probability, R: reject the null hypothesis (H 0 ) at 5% probability.…”

Section: Resultsmentioning

confidence: 99%

Monotonic trend and change points in southern Brazil precipitation

Damé¹,

Teixeira²,

Bacelar

et al. 2013

Eng. Agríc.

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Scientific evidence on climate changes at global level has gained increasing interest in the scientific community in general. The impacts of climate change as well as anthropogenic actions may cause errors in hydro-agricultural projects existent in the watershed under study. This study aimed to identify the presence or absence of trend in total annual precipitation series of the watershed of the Mirim Lagoon, state of Rio Grande do Sul-RS / Brazil / Uruguay (Brazilian side) as well as to detect the period in which they occurred. For that, it was analyzed the precipitation data belonging to 14 weather stations. To detect the existence of monotonic trend and change points, it was used the nonparametric tests of Mann-Kendall and Mann-Whitney, the "t" test of Student for two samples of unpaired data (parametric), as well as the technique of progressive mean. The Weather Station 3152014 (Pelotas) presented changes in the trend in the series of annual precipitation in the period from 1953 to 2007. The methodologies that use subdivided series were more efficient in detecting change in trend when compared with the Mann-Kendall test, which uses the complete series (from 1921 to 2007 PALAVRAS-CHAVE:teste paramétrico e não paramétrico, mudança climática, alteração de tendência.Monotonic trend and change points in southern Brazil precipitationEng.

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Variabilidade amostral das séries mensais de precipitação pluvial em duas regiões do Brasil: Pelotas-RS e Campinas-SP

Cited by 19 publications

References 8 publications

Inadequacy of the gamma distribution to calculate the Standardized Precipitation Index

Inadequacy of the gamma distribution to calculate the Standardized Precipitation Index

Standardized precipitation index based on pearson type III distribution

Monotonic trend and change points in southern Brazil precipitation

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