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Universidad de Chile (2011)

Análisis regional de frecuencia mediante el método de los L-momentos en las regiones de Valparaíso y Metropolitana para la generación de cartografía probabilística de sequía meteorológica

Naranjo Toledo, Raúl Cristián Antonio

Titre : Análisis regional de frecuencia mediante el método de los L-momentos en las regiones de Valparaíso y Metropolitana para la generación de cartografía probabilística de sequía meteorológica

Auteur : Naranjo Toledo, Raúl Cristián Antonio

Université de soutenance : Universidad de Chile

Grade : Ingeniero en Recursos Naturales Renovables 2011

Résumé
In the present study, we applied a methodology called regional frequency analysis based on the L-moments. This methodology was applied to generate cartography of probabilities associated to meteorological drought in the Valparaíso and Metropolitan Region of Chile for different time spans, on the base of the criteria of water deficit established by the decree 39 of the General Management of Water of 1984. In order to apply the statistical procedures associated to the L-moments, it was required to generate a database of precipitation according to the supposed of the regional of frequency analysis, it proceeded to eliminate anomalous and incomplete data of the precipitation records and to analyse if the series of data satisfied the supposed of presenting non tendencies neither correlation. Also, it proceeded to form homogeneous regions of precipitation through different procedures. Finally, the homogeneous regions of precipitation were formed based on the indicators of discordance and homogeneity based on the L-moments. Different distributions of probability to the homogeneous regions were adjusted to select a distribution of best adjustment according to certain criteria. Regional quintiles were estimated with each distribution selected and at the early month combinations of April and July for duration of a span of 3, 6, 12, 18, 24, 39 and 36 months. To create the map of probabilities of meteorological drought, it was necessary to estimate the spatial distribution of the L-moments (L-coefficient of variation and L- skewness) through the adjustment of an exponential function between the L-moments and the annual average of precipitation, utilizing this as a variable to help. As main results, maps of probabilities of non-excedence associated to precipitation equal or lower to the 70% of the average of each period and return period maps associated to the probabilities of nonexcedence were obtained. The values of the probabilities obtained were adjusted to the spatial distribution of precipitation of the Valparaíso and Metropolitan Region. Greater odds of water deficit in the driest zones were obtained and smaller odds in the most humid zones, being the values of the similar odds for certain combinations due to the annual distribution of the precipitations.

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