Exploration of the standardized precipitation index with regional analysis

A regional analysis of 5-d precipitation is presented as an interpretative tool for the standardized precipitation index (SPI). As a water stress index, the SPI provides an historical context to the precipitation fallen over the last i days. A regional analysis allows the SPI to be used beyond its usual diagnostic function, by quantifying the probability that precipitation to come will put an end to an ongoing drought. The proposed regional analysis relies on the precipitation gathered at 110 meteorological stations within Quebec. Five homogeneous regions have been established through the use of a discordancy test and heterogeneity test. Various normalised regional distribution have been adjusted by L-moments. The best adjustments are achieved for the Pearson type III (gamma) distribution.