Inadequacy of the gamma distribution to calculate the Standardized Precipitation Index
ABSTRACT The 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 rainfal...
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| Language: | English |
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Universidade Federal de Campina Grande
2015-12-01
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| Series: | Revista Brasileira de Engenharia Agrícola e Ambiental |
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| Online Access: | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-43662015001201129&lng=en&tlng=en |
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| _version_ | 1849738092960808960 |
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| author | Gabriel C. Blain Monica C. Meschiatti |
| author_facet | Gabriel C. Blain Monica C. Meschiatti |
| author_sort | Gabriel C. Blain |
| collection | DOAJ |
| description | ABSTRACT The 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. |
| format | Article |
| id | doaj-art-7b64c336e2f14112a2800a57ce99dd39 |
| institution | DOAJ |
| issn | 1807-1929 |
| language | English |
| publishDate | 2015-12-01 |
| publisher | Universidade Federal de Campina Grande |
| record_format | Article |
| series | Revista Brasileira de Engenharia Agrícola e Ambiental |
| spelling | doaj-art-7b64c336e2f14112a2800a57ce99dd392025-08-20T03:06:43ZengUniversidade Federal de Campina GrandeRevista Brasileira de Engenharia Agrícola e Ambiental1807-19292015-12-0119121129113510.1590/1807-1929/agriambi.v19n12p1129-1135S1415-43662015001201129Inadequacy of the gamma distribution to calculate the Standardized Precipitation IndexGabriel C. BlainMonica C. MeschiattiABSTRACT The 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.http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-43662015001201129&lng=en&tlng=endesvios de precipitaçãoteste de normalidadeteste de aderência |
| spellingShingle | Gabriel C. Blain Monica C. Meschiatti Inadequacy of the gamma distribution to calculate the Standardized Precipitation Index Revista Brasileira de Engenharia Agrícola e Ambiental desvios de precipitação teste de normalidade teste de aderência |
| title | Inadequacy of the gamma distribution to calculate the Standardized Precipitation Index |
| title_full | Inadequacy of the gamma distribution to calculate the Standardized Precipitation Index |
| title_fullStr | Inadequacy of the gamma distribution to calculate the Standardized Precipitation Index |
| title_full_unstemmed | Inadequacy of the gamma distribution to calculate the Standardized Precipitation Index |
| title_short | Inadequacy of the gamma distribution to calculate the Standardized Precipitation Index |
| title_sort | inadequacy of the gamma distribution to calculate the standardized precipitation index |
| topic | desvios de precipitação teste de normalidade teste de aderência |
| url | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-43662015001201129&lng=en&tlng=en |
| work_keys_str_mv | AT gabrielcblain inadequacyofthegammadistributiontocalculatethestandardizedprecipitationindex AT monicacmeschiatti inadequacyofthegammadistributiontocalculatethestandardizedprecipitationindex |